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HUMAN BIOLOGY

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THE MACMILLAN COMPANY

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ATLANTA SAN FRANCISCO

MACMILLAN & CO., LIMITED

LONDON BOMBAY CALCUTTA
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THE MACMILLAN CO. OF CANADA, LTD.

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ANIMAL BIOLOGY
HUMAN BIOLOGY

PARTS II AND III

OF

FIRST COURSE IN BIOLOGY

BY
L. H. BAILEY AND W. M. COLEMAN

Xdrr gorfe
THE MACMILLAN COMPANY

1910

All rights reserved

COPYRIGHT, 1908,
BY THE MACMILLAN COMPANY.

Set up and electrotyped. Published July, 1908. Reprinted
October, 1908; February, September, 1909 ; January, 1910.

Norinooti
J. S. Gushing Co. Berwick & Smith Co.

Norwood, Mass., U.S.A.

PREFACE

THE present tendency in secondary education is away
from the formal technical completion of separate subjects
and toward the developing of a workable training in the
activities that relate the pupil to his own life. In the
natural science field, the tendency is to attach less im-
portance to botany and zoology and physiology as such,
and to lay greater stress on the processes and adaptations
of life as expressed in plants and animals and men. This
tendency is a revolt against the laboratory method and
research method of the college as it has been impressed
into the common schools, for it is not uncommon for the
pupil to study botany without really knowing plants, or
physiology without knowing himself. Education that is
not applicable, that does not put the pupil into touch with
the living knowledge and the affairs of his time, may be
of less educative value than the learning of a trade in a
shop. We are coming to learn that the ideals and the
abilities should be developed out of the common surround-
ings and affairs of life rather than imposed on the pupil
as a matter of abstract, unrelated theory.

One of the marks of this new tendency in education
is the introduction of unit courses in biology in the sec-
ondary schools, in the place of the formal and often dry
and nearly meaningless isolated courses in botany, zoology,
and physiology. This result is one of the outcomes of the
recent nature-study discussions.

The present volume is an effort to meet the need for

vi PREFACE

a simple and untechnical text to cover this secondary
biology in its elementary phases. The book stands be-
tween the unorganized nature-study of the intermediate
grades and the formal science of the more advanced
courses. It is a difficult space to bridge, partly because
the subjects are so diverse, and partly because some
teachers do not yet understand the importance of im-
parting to beginners a general rather than a special
view point.

Still another difficulty is the lack of uniformity in the
practice of different schools. It is not urged that it is
desirable to have uniformity in all respects, but the lack
of it makes it difficult to prepare a book that shall equally
meet all needs. It is hoped, however, that the present
book is fairly adaptable to a variety of conditions, and
with this thought in mind the following suggestions are
made as to its use :

Being in three separate parts, the teacher may begin
with plants, or with animals, or with human physiology.

If a one-year course is desired, the topics that are
printed in large type in Parts II and III may be used,
and a choice from the chapters in Part I.

For three half-year courses, all the parts may be cov-
ered in full.

If the course in biology begins in the fall (with the
school year), it may be well to study plant biology two
days in the week and animal biology three days until
midwinter ; when outdoor material becomes scarce, human
biology may be followed five days in the week ; in spring,
plants may be studied three days and animals two days.

If the use of the book is begun at midyear, it will prob-
ably be better to follow the order in the book consecu-
tively.

PREFACE vii

If it is desired to take only a part of the plant biology,
Chapters VI, XIV, XX, XXIII, XXIV may be omitted,
and also perhaps parts of other chapters (as of X, XII,
XIII) if the time is very short. The important point is
to give the pupil a rational conception of what plants are
and of their main activities ; therefore, the parts that deal
with the underlying life processes and the relation of the
plant to its surroundings should not be omitted.

If more work is wanted it is best to provide the extra
work by means of the study of a greater abundance of
specimens rather than by the addition of more texts; but
the teacher must be careful not to introduce too much
detail until the general subject has first been covered.

The value of biology study lies in the work with the
actual things themselves. It is not possible to provide
specimens for every point in the work, nor is it always
desirable to do so ; for the beginning pupil may not be
able to interest himself in the objects, and he may become
immersed in details before he has arrived at any general
view or reason of the subject. Great care must be exer-
cised that the pupil is not swamped. Mere book work or
memory stuffing is useless, and it may dwarf or divert
the sympathies of active young minds.

Every effort should be made to apply the lessons to
daily life. The very reason for knowing plants and ani-
mals is that one may live with them, and the reason for
knowing oneself is that he may live his daily life with
some degree of intelligence. The teacher should not be
afraid to make all teaching useful and practical.

In many cases a state syllabus designates just what
subjects shall be covered ; the topics may be chosen easily
from the text, and the order of them is usually left largely
to the discretion of the teacher.

viii PREFACE

Finally, let it be repeated that it is much better for the
beginning pupil to acquire a real conception of a few
central principles and points of view respecting common
forms that will enable him to tie his knowledge together
and organize it and apply it, than to familiarize himself
with any number of mere facts about the lower forms of
life which, at the best, he can know only indirectly and
remotely. If the pupil wishes to go farther in later years,
he may then take up special groups and phases.

CONTENTS ix
PART II. ANIMAL BIOLOGY

CHAPTER PAGE

I. INTRODUCTION i

II. PROTOZOANS 10

III. SPONGES 17

IV. POLYPS 22

V. ECHINODERMS 34

VI. WORMS 42

VII. CRUSTACEANS . . . . , . . . .51

VIII. INSECTS 63

IX. MOLLUSKS 97

X. FISHES .......... 109

XI. BATRACHIANS 126

XII. REPTILES 139

XIII. BIRDS 150

XIV. MAMMALS 184

PART III. HUMAN BIOLOGY

I. INTRODUCTION i

II. THE SKIN AND KIDNEYS 16

III. THE SKELETON 29

IV. THE MUSCLES 39

V. THE CIRCULATION 51

VI. THE RESPIRATION .70

VII. FOOD AND DIGESTION 89

VIII. THE NERVOUS SYSTEM 117

IX. THE SENSES ......... 142

X. BACTERIA AND SANITATION .158

GENERAL INDEX i

GENERAL INTRODUCTION

PRELIMINARY EXPERIMENTS

These experiments are inserted for those pupils who have not
had instruction in chemistry and physics, to give them a point of
view on the subjects that follow. At least a general understanding
of some of these subjects is necessary to a satisfactory elementary
study of biology.

Elements and Compounds. - The material world is made
up of elements and compounds. An element is a sub-
stance that cannot be separated into two or more sub-
stances. A compound is formed by the union of two or
more elements. All the material or substance of which
the earth and its inhabitants is composed is formed of the
chemical elements ; this substance taken all together is
known as matter'.

Carbon and iron are examples of elements. Compare a
bit of charcoal, which is one form of carbon, with a new
iron nail. Which is brighter ? Heavier for its size ?
Tougher ? More brittle ? Harder ? More readily com-
bustible ? Resistant to change when left exposed to air
and dampness ? There are two other forms of carbon :
graphite or black lead (used in pencils and stove polish);
and diamond, which occurs in crystals and is the hardest
known substance. Iron does not have varied forms like
carbon. Sulfur is another element. What is its color ?
Has it odor? Taste? Will it dissolve in water? Is it
heavy or light ? Will it burn ? What is the color of
the flame ? Of the fumes ? Phosphorus, another element,

xi

xii GENERAL INTRODUCTION

burns so readily that it ignites by friction and is used in
matches. Rub the tip of a match with the finger. What
is the odor of phosphorus ? Phosphorus exists in nature
only in combination with other elements. Lead, tin, silver,
gold, copper, zinc, nickel, platinum, are elements.

There are less than eighty known elements ; but the com-
pounds formed of them are innumerable. Carbon is found
in all substances formed by the growth of living things.
That there is carbon in sugar, for example, can easily be
shown by charring it on a hot shovel or a stove until its
water is driven off and only charcoal is left. Part of the
starch in a biscuit remains as charcoal when it has been
half burned.

Favorable and Unfavorable Conditions for Evaporation.
Pour the same quantity of water (half a glassful) into
three saucers and two bottles. Place one saucer near a
hot stove ; place the other two in a cool place, having first
covered one of them with a dish. Place one of the bottles
by the stove and the other by the remaining saucers. After
some hours, examine the saucers and bottles and compare
and record the results. Explain. State three conditions
that are favorable to evaporation. State three ways in
which evaporation may be prevented or decreased.

Tests for Acid, Alkaline, and Neutral Substances. - - For
acid tests, use sour buttermilk (which contains lactic acid),
or hydrochloric acid diluted in ten parts water, or strong
vinegar (which contains acetic acid). Has the acid a char-
acteristic (" sour") odor and taste (test it only when very
dilute)? Rub dilute acid between the fingers; how does
it feel? Is there any effect on the fingers ? Obtain litmus
paper at a druggist's. Dip a strip of red litmus and of
blue litmus paper into the acid. What result ?

For alkaline tests, dissolve in a glass of water a spoonful

PRELIMINARY EXPERIMENTS xiii

of baking soda or some laundry soap ; or dissolve an inch
stick of caustic soda in a glass of water. Test odor and
" feel " of last solution as with the acid ; likewise test effect
of alkaline solution on red and blue litmus paper. Record
results. Alkalies are strong examples of a more general
class of substances called bases, which have the opposite
effect from acids.

Test pure water. Has it odor ? A taste ? Test it with
red and blue litmus paper. Water is a neutral substance ;
that is, it is neither an acid nor an alkali (or base).

After making appropriate tests, write ac, al, or neu after
each name in the following list (or write in three columns):
vinegar, soda, saliva, sugar, juice of apple, lemon, and
other fruits, milk, baking powder, buttermilk, ammonia,
salt water.

Pour some of the alkaline solution into a dish, gradually
add dilute acid (or sour buttermilk), stirring with glass rod
and testing with litmus until the mixture does not turn red
litmus blue nor blue litmus red. The acid and alkali are
then said to have neutralized each other, and the resulting
substance is called a salt. The salt may be obtained by
evaporating the water of the solution. Most common
minerals are salts. If the last experiment is tried with
soda and sour buttermilk, the demonstration will show
some of the facts involved in bread making with the use
of these substances.

Tests for Starch. - - Starch turns blue with iodine. The
color may be driven away by heat, but will return again as
the temperature lowers. Produce a few cents' worth of tinc-
ture of iodine and dilute it. Get a half dozen pieces of
paper and cardboard, all different, and test each for starch
by placing it over mouth of bottle and tipping the bottle
up. It much starch is present, the spot will be blue-black

xiv GENERAL INTRODUCTION

or dark blue ; if little starch, pale blue ; if no starch, brown
or yellowish.

Make pastes with wheat flour, potato starch, and corn
starch. Treat a little of each with a solution of rather
dilute tincture of iodine. Try grains from crushed rice
with the same solution. Are they the same color? Cut a
thin section from a potato, treat with iodine and examine
under the microscope.

To study Starch Grains. Mount in cold water a few
grains of starch from each of the following : potato, wheat,
arrowroot (buy at drug store), rice, oats, corn. Study under
microscope the sizes, forms, layers, fissures, and location
of nuclei, and make a drawing of a few grains of each.

Test for Grape Sugar. Make a thick section of a bit of
the edible part of a pear and place it in a bath of Fehling's
solution. After a few moments boil the liquid containing
the section for one or two minutes. It will turn to an
orange color, showing a deposit of an oxid of copper and
perhaps a little copper in the metallic form. A thin sec-
tion treated in like manner may be examined under the
microscope, and the fine particles, precipitated from the
sugar of the pear, may be clearly seen. (Fehlings solution
is made by taking one part each of these three solutions
and two parts of water: (i) Copper sulfate, 9 grams in
250 cubic centimeters of water; (2) sodium hydroxid, 30
grams in 250 c.c. water ; (3) Rochelle salts, 43 grams in
250 c.c. water.)

Test for Nitrogenous Substances, or Proteids. - - Put a little
white of egg into a test tube and heat slowly. What change
takes place in the egg? Put another part of the white of
egg into a test tube and add dilute nitric acid. Compare
the results of the two experiments. White of egg is an ex-
ample of a proteid ; that is, it is the form of nitrogen most

PRELIMINARY EXPERIMENTS XV

commonly found in plant and animal tissue, and it can be
formed only by life processes. Do acid and heat harden
or soften most substances ? Either of the above tests
reveals proteid, if present. Does cooking tend to soften
or toughen lean meat ?

Another test for proteid is nitric acid, which turns pro-
teid (and hardly anything else) yellow. Proteid when
burned has a characteristic odor ; this will be noticed if lean
meat or cheese is charred in a spoon. The offensive odor
from decomposing proteid is also characteristic, whether it
comes from stale beans, meat, mushrooms, or other things
containing proteid.

Test for Fats and Oils. - - Place a little tallow from a
candle on unglazed paper and warm. Hold the paper up
to the lierht and examine it. What effect has the fat had

O

on the paper ? Place a little starch, sugar, powdered chalk,
or white of egg on paper and repeat the experiment ; is
the effect the same ? Place some of the tallow in a spoon,
and heat. Compare the effect of heat on fat and proteid.
Water also makes paper semi-transparent, but it soon
evaporates : fat does not evaporate.

Another test for fats is to mount a thin section of the
endosperm of castor-oil seed in water and examine with
high power. Small drops of oil will be quite abundant.
Treat the mount with alcanin (henna root in alcohol).
The drops of oil will stain red. This is a standard test
for fats and oils.

To make or liberate Oxygen. - - If there is a chemistry
class in school, one of its members will doubtless be glad
to prepare some of the gas called oxygen, and furnish
several glass jars filled with it to the biology class. If
it is desired to make oxygen, the following method may
be employed : Provide a dry glass flask of three to four

xvi GENERAL INTRODUCTION

ounces capacity. It should have a glass delivery tube,
inserted through a one-holed rubber stopper, and so bent
as to pass under the surface of water contained in a
deep dish. Fill several pint fruit-jars with water, cover
with pieces of stiff pasteboard, and turn mouth down-
wards in the dish of water. From one half to two thirds
ounce of an equal mixture of potassium chlorate and
manganese dioxid (procured at drug store) is put in the
flask and heated by means of a gas or alcohol lamp.
When the oxygen begins to form, collect some in jars
by inserting the end of delivery tube under the jars as
they stand in water. Caution : Remove delivery tube
from water before cooling the flask, to prevent any water
being drawn back.

Oxygen and the Air. - The great activity of pure oxygen
in attacking other substances can be shown by passing
into a fruit-jar a lighted splinter, a piece of lighted mag-
nesium ribbon, an old watch spring (or a bit of picture
wire), the end of which has been dipped in sulfur and
lighted. About one fifth of the air is oxygen and about
four fifths is nitrogen and other inactive gases. Pure
nitrogen will quickly extinguish a lighted splinter thrust
into it. It is the oxygen in the air that supports all forms
of burning. Less than one half of one per cent of th"
air is an inactive gas called carbon dioxid, a compound
of carbon and oxygen. It is formed not only when wood
or coal is burned, but also by the life processes of animals
and plants.

Oxidation. - - That something besides wood or coal is
necessary to a fire can be shown by shutting off entirely
the draught of a stove. Fire and other forms of combus-
tion depend on a process called oxidation. This consists
in the uniting of oxygen with other substances. When

PRELIMINARY EXPERIMENTS xvii

wood decays, the carbon in it oxidizes (unites with oxygen)
and carbon dioxid gas is formed. When wood burns, the
oxidation is more rapid. When iron oxidizes, iron rust is
formed. When hydrogen is oxidized, water is formed.
Kerosene oil contains hydrogen, and water is formed when
it is burned. Almost every one has noticed the cloud of
moisture which collects on the chimney when the lamp is
first lighted. By using a chimney which has been kept
in a cold place, the moisture becomes apparent ; soon
the chimney becomes hot and the water no longer collects,
but it continues to pass into the room as long as the lamp
burns. Fats also contain hydrogen. Hold a piece of cold
glass or an^ inverted tumbler above the flame of a tallow
candle. Does water collect on it ?

Oxidation may be said to be the basis of all life processes
for this reason : oxidation gives rise to heat and sets free
energy, and all living things need heat and energy in order
to grow and live. The heat of animals is very noticeable.
The oxidation in plants also forms a slight amount of heat.
In both animals and plants oxidation is much slower than
in ordinary fires. That heat is formed even in slow oxida-
tion is shown by fires which arise spontaneously in masses
of decaying material. The rotting of wood is not only
" ;companied by heat but sometimes by light, as when
"fox fire" is emitted. Rub the end of a match on your
finger in the dark. Explain the result. Strike a match
and notice the white fumes which rise for an instant.
These fumes are not ordinary smoke (particles of carbon),
but they are oxid of phosphorus. Why will water (oxid
of hydrogen) not burn ? Sand is oxid of silicon. Explain
how throwing sand on a fire puts it out. [See also experi-
ments with candle and breath, in Introduction to Human
Biology.]

xviii GENERAL INTRODUCTION

Inorganic and Organic Matter. - - Test for Minerals.
The earth was once in a molten condition, which would
have destroyed any combustible material if any had then
existed. Before plants and animals existed, the earth con-
sisted mostly of incombustible minerals, known as inorganic
matter. Substances formed by animals and plants are
organic matter, so called because built up by organized or
organ-bearing or living things ; starch is an example, being
formed in plants. Organic substances are composed chiefly
of carbon, oxygen, hydrogen, and nitrogen. (See page I
of " Animal Biology.") Coal-oil, and all combustible ma-
terials have their origin in life. Hence, burning to find
whether there is an incombustible residue is^al^o a test for
minerals. Meat, bread, oatmeal, bone, wood, may be tested
for mineral matter by burning in a spoon held over a hot
fire, or flame of gas or lamp. The substance being tested
should be burned until all black material (which is organic
carbon and not a mineral) has disappeared. Any residue
will be mineral matter.

Protoplasm. - - Inside the cells of plants and animals is
the living substance, known as 'protoplasm. It is a struc-
tureless, nearly or quite colorless, transparent jelly-like
substance of very complex and unstable composition.
Eighty per cent or more is water ; the remainder is pro-
teid, fats, oils, sugars, and salts. Protoplasm has the
power of groivtJi and reproduction ; it can make living sub-
stance from dead or lifeless substances. It has the power
of movement within the cell, and it is influenced (or is irrita-
ble) by heat, light, touch, and other stimuli. When proto-
plasm dies the organism dies.

Physics is the science that treats of the properties and
phenomena (or behavior) of matter or of objects ; as of
such properties or phenomena or agencies as heat, light,

PRELIMINARY EXPERIMENTS xix

force, electricity, sound, friction, density, weight, and the
like.

Chemistry is the science that treats of the composition of
matter. All matter is made up, as we have seen, of ele-
ments. Very few elements exist in nature in a free or
uncombined form. The nitrogen and oxygen of the air

*s

are the leading uncombined elements.

In order to express the chemical combinations clearly,
symbols are used to represent each element, and these
symbols are then combined to represent the proportions
of each in the compound. If C stands for carbon and O
for oxygen, the carbon dioxid might be represented by the
formula COO. In order to avoid the repetition of any
letter, however, a number is used to denote how many
times the element is taken : thus the formula always used
for carbon dioxid is CO 2 . The formula for hydrogen
oxid, or water, is H 2 O ; that for starch is C 6 H 10 O 5 . N
stands for nitrogen ; P, for phosphorus ; K, potassium ;
Fe, iron ; S, sulfur.

Biology is the science that treats of life ; that is, of all
knowledge of plants and animals of all kinds. (See page
i, " Animal Biology.")

How A CANDLE BURNS

Some of the foregoing suggestions may be readily explained
and illustrated by simple experiments with a burning candle.
The following directions for such experiments are by G. W.
Cavanaugh.

The materials needed for this exercise are : a piece of candle
about two inches long, a lamp chimney (one with a plain top is
best), a piece of white crockery or window glass, a piece of fine
wire about six inches long, a bit of quicklime about half the
size of an egg, and some matches. All of these, with the possible
exception of the quicklime, can be obtained in any household.

XX

GENERAL INTRODUCTION

If you perform the experiment requiring the Jime, be sure that you
start with a fresh piece of quick or stone lime, which can be had
of any lime or cement dealer. During the performance of the
following simple experiments, the pupil should describe what he
sees at each step. The questions inserted in the text are offered
merely as suggestions in the development of the desired ideas.

f

The answers are those which it is desired the pupils shall reach
or confirm by their own observation.

I. Oxygen

Light the candle and place it on a piece of blotting
paper (A). What do you see burning ? Is anything burn-
ing besides the candle ? The answer
will probably be " no." Let us see.

Place the lamp chimney over the
lighted candle, and partly cover the
top by a piece of stiff paper, as in
Fig. A. Ask the pupils to observe
and describe how the flame goes out ;
i.e. that it is gradually extinguished
and does not go out instantly. Why
did the flame go out ? The probable
thought will be,

" Because there was no air." (If there
was no air within the chimney, some
could have entered at the top.)

Place two pencils beside the re-
lighted candle and on them the chim-
ney (B\ What is the difference be-
tween the way in which the candle
burns now and before the chimney
was placed over it? It flickers, or * SUPPLYING AIR UN-

DERNEATH THE CHIM-

dances about more. What makes NEY.

A. THE BEGINNING OF
THE CANDLE EX-
PERIMENT.

PRELIMINARY EXPERIMENTS xxi

boys and girls feel like dancing about when they go out
from a warm schoolroom ? What makes the flame dance
or flicker when the chimney is raised by the pencils ?
Because it gets fresh air under the chimney.

Repeat the first experiment, in which the flame grows
gradually smaller till it is extinguished. Why does the
flame die out now ? Is it really necessary to have fresh
air in order to keep a flame burning?

To prove this further, let the candle be relighted. Place
the chimney over it, now having the top completely closed
by a piece of paper. Have ready a lighted splinter or
match, and just as soon as the candle is extinguished
remove the paper from the chimney top and thrust in the
lighted splinter. Why does the light on the splinter go
out? What became of the freshness that was in the air ?
It was destroyed by the burning candle.

Evidently there is some decided difference between un-
burned air and burned air, since a flame can continue to
burn only in air that has the quality known as freshness.
This quality of fresh air is due to oxygen, represented by O.
Why was the splinter put out instantly, while the candle
flame died out gradually ? When the splinter was thrust
in, the air had no freshness or oxygen at all, while when
the candle was placed under the chimney, it had whatever
oxygen was originally in the air within the chimney.

Endeavor to have this point clearly understood : that the
candle did not go out as long as the air had any oxygen
and that the splinter was extinguished immediately because
there was no oxygen left.

Relight the candle. A former question may now be
repeated : Is anything else burning besides the candle?

When the subject of the necessity of fresh air and con-
sequently of oxygen for the burning of the candle seems

XX11

GENERAL INTRODUCTION

to be understood, the following questions, together with
any others which suggest themselves, may be asked: What
is the reason that draughts are opened in stoves ? Why is
the bottom of a " burner " on a lamp always full of holes ?

II. Carbon

Let us now observe the blackened end of a burned match
or splinter. This black substance is usually known by the
name of charcoal. If handled, it will blacken the fingers.
Try this. The same substance is found on the bottoms of
kettles which have been used over a wood fire, but it is
there a fine powder.

Let us see what was burning when the candle was
lighted, besides the oxygen in the air. Relight the candle

and hold the porcelain or glass about
an inch above the bright part of the
flame. What happens to it there ?
Next, lower it directly into the flame
(C). What is the black stuff that
gets on the glass ? Look closely and
see whether it is not deposited here
also as a fine powder. Will this de-
posit from the candle blacken the

C. THE CARBON (OR

SOOT) IS DEPOSITED
ON THE GLASS.

fingers ?

Instead of using the name charcoal for this black sub-
stance, let us call it carbon, the better name, because
there are several kinds of carbon, and charcoal is only
that kind which is rather light and easily blackens the
hands.

The carbon from the candle flame came mostly from the
wax or tallow ; only a very small part came from the wick.
It cannot be seen in the tallow, neither can it be seen in

PRELIMINARY EXPERIMENTS xxiii

unburned wood, and yet it can be found when the wood is
partly burned.

Why, now, is the glass blackened when held in the flame
and not when held directly above it? It is because the
carbon from the candle has not been completely burned
at the middle of the flame ; but it is burned beyond the
bright part of the flame. When the glass is held in the
flame, the carbon that is not yet completely burned is de-
posited on it, because it is cooler than that in the surround-
ing flame.

A fine deposit of carbon can be had from any of the
luminous parts of the flame ; and it is these thousands of
little particles of carbon, getting white hot, which glow
like coals in the stove and make the light. Just as soon
as they are completely burned, there is no more light, as
coals cease to glow when burned to ashes.

III. Carbon dioxid

Let us now inquire what becomes of the carbon that we
find in the bright part of the flame and of the oxygen that
was in the air in the lamp chimney. When the candle was
extinguished within the chimney, there was no oxygen left,
as shown by the lighted splinter, which was put out immedi-
ately. . Neither could any of the particles of carbon be
found except on the wick. Yet they both still exist within
the chimney, but in an entirely different condition. While
the candle was burning, the little particles of carbon that
we find ascending in the flame are joining with the oxygen
of the air and making an entirely new substance. This
new substance is a gas and cannot be seen in the air.

Of what two substances is this new substance made ?
It is CO 2 .

XXIV

GENERAL INTR OD UCTION

D. THE TEST
WITH THE SUS-
PENDED FILM

OF LlMEWATER.

Place a bit of quicklime in about half a glass of water
on the day previous to the experiment. When ready for
use there will be a white sediment at the bottom and a thin

white scum on the top of the clear lime-
water. The pupils should see this white
scum, as a question about it will follow.
Make a loop in the end of the piece of
wire by turning it around the point of a
lead pencil. Remove the scum from the
limewater with a piece of paper and insert
the loop into the clear water. When
withdrawn, the loop ought to hold a film
of clear water. Pass the wire through a
piece of cardboard or stiff paper, and
arrange as shown in D.
Place the chimney over the lighted candle. Lower the
loop into the chimney and cover the top of the chimney
with the paper. Withdraw the wire two minutes after the
candle goes out. Note the cloudy appearance of the film
of water on the wire. The cloudiness was caused by the
carbon dioxid formed while the candle was burning.

Omitting the candle, hang the freshly wetted wire in the
empty chimney. Let the film of limewater remain within
the chimney for the same length of time as when the can-
dle was used. It does not become cloudy now. The
cloudiness in clear limewater is a test or indication that
carbon dioxid is present.

What caused the white scum on the limewater which
stood overnight ?

How does the CO 2 get into the air ? It is formed when-
ever wood, coal, oil, or gas is burned.

The amount of CO 2 in ordinary air is very small, being
only three parts in ten thousand. If the limewater in the

PRELIMINARY EXPERIMENTS XXV

loop be left long enough in the air, it will become cloudy.
The reason it clouds so quickly when the candle is being
burned is that a large amount of CO 2 is formed. Besides
being made by real flames, CO 2 is formed every time we
breathe out air. Renew the film of water in the loop and
breathe against it gently for two or three minutes.

The presence of CO 2 in the breath may be shown better
by pouring off some of the clear limewater into a clean
glass and blowing into it through a straw.

Why does water put out a fire ? The answer is, not
alone because it wets and shuts off the supply of free
oxygen, but because it cools the carbon, which must be
hot in order to unite with the oxygen, and prevents the
oxygen of the air from getting as near the carbon as
before.

ANIMAL BIOLOGY

CHAPTER I

THE PRINCIPLES OF BIOLOGY

BIOLOGY (Greek, bios, life; logos, discourse) means the
science of life. It treats of animals and plants. That
branch of biology which treats of animals is called zoology
(Gr. zoon, animal ; logos, discourse). The biological
science of botany (Gr. botanc, plant or herb) treats of
plants.

Living things are distinguished from the not living by a
series of processes, or changes (feeding, growth, develop-
ment, multiplication, etc.), which together constitute what
is called life. These processes are called functions. Both
plants and animals have certain parts called organs which
have each a definite work, or function; hence animals and
plants are said to be organized. For example, men and
most animals have a certain organ (the mouth) for taking
in nourishment; another (the food tube), for its digestion.

Because of its organization, each animal or plant is said
to be an organism. Living things constitute the organic
kingdom. Things without life and not formed by life
constitute the inorganic, or mineral, kingdom. Mark I for
inorganic and O for organic after the proper words in this
list: granite, sugar, lumber, gold, shellac, sand, coal, paper,
glass, starch, copper, gelatine, cloth, air, potatoes, alcohol,
oil, clay. Which of these things are used for food by
animals ? Conclusion ?

B i

ANIMAL BIOLOGY

Energy in the Organic World. - - We see animals exerting
energy; that is, we see them moving about and doing
work. Plants are never seen acting that way; yet they
need energy in order to form their tissues, grow, and raise
themselves in the air.

Source of Plant Energy. - - We notice that green plants
thrive only in the light, while animal growth is largely in-
dependent of light. In fact, in the salt mines of Poland
there are churches and villages below the ground, and
children are born, become adults, and live all their lives
below ground, without seeing the sun. (That these people
are not very strong is doubtless due more to want of fresh
air and other causes than want of sunlight.)

The need of plants for
sunlight shows that they
must obtain something
from the sun. This has
been found to be energy.
This enables them to lift
their stems in growth, and form the various structures
called tissues which make up their stems and leaves. (See
Part I, Chap. XIII.) It is noticed
that they take in food and water
from the soil through their roots.
Experiments also show that green
plants take in through pores
(Fig. i), on the surface of their
leaves, a gas composed of carbon
and oxygen, and called carbon
dioxid. The energy in tJie sunligJit
enables the plant to' separate out the

carbon of the carbon dioxid and

. FIG. 2. A LEAF STORING

build mineral and water and carbon ENERGY IN SUNLIGHT.

FIG. i. SURFACES OF A LEAF,
magnified.

Carbonic^Acid Gas
in the Air going
into the Leaf

THE PRINCIPLES OF BIOLOGY

into organic substances. The oxygen of the carbon dioxid
is set free and returns to the air (Fig. 2). Starch, sugar,
oil, and woody fiber are examples of substances thus
formed. Can you think of any fuel not due to plants ?
How Animals obtain Energy. You have noticed that
starch, oil, etc., will burn, or oxidize -, that is, unite with the
oxygen of the air ; thus the sun's energy, stored in these
substances, is changed back to heat and motion. The
oxidation of oil or sugar may occur in a furnace; it may
also occur in the living substance of the active animal.

FIG. 3. Colorless plants, as MUSH- A GREEN LEAF, even after it is cut, gives
ROOMS, give off no oxygen. off oxygen (O) if kept in the sun.

Fortunately for the animals the plants oxidize very little
of the substances built up by them, since they do not move
about nor need to keep themselves warm. We notice that
animals are constantly using plant substances for food, and
constantly drawing the air into their bodies. If the sun-
light had not enabled the green plant to store up these
substances and set free the oxygen (Fig. 3), animals
would have no food to eat nor air to breathe; hence we
may say that the sunlight is indirectly the source of the
life and energy of animals. Mushrooms and other plants
without green matter cannot set oxygen free (Fig. 3).

4 ANIMAL BIOLOGY

Experiment to show the Cause of Burning, or Oxidation.
-Obtain a large glass bottle (a pickle jar), a short candle,
and some matches. Light the candle and put it on a table
near the edge, and cover it with the glass jar. The flame
slowly smothers and goes out. Why is this ? Is the air
now in the jar different from that which was in it before
the candle was lighted ? Some change must have taken
place or the candle would continue to burn. To try
whether the candle will burn again under the jar without
changing the air, slide the jar to the edge of the table and
let the candle drop out. Light the candle and slip it up
into the jar again, the jar being held with its mouth a little
over the edge of the table to receive the candle (Fig. 5).
The flame goes out at once. Evidently the air in the jar
is not the same as the air outside. Take up the jar and
wave it to and fro a few times, so as to remove the old air
and admit fresh air. The candle now burns in it with as
bright a flame as at first. So we conclude that the candle
will not continue to burn unless there is a constant supply
of fresh air. The gas formed by the burning is carbon
dioxid. It is the gas from which plants extract carbon.
(See Plant Biology, Chap. V.) One test for the presence
of this gas is that it forms a white, chalky cloud in lime
water ; another is that it smothers a fire.

Experiment to show that Animals give off Carbon Dioxid.
Place a cardboard over the mouth of a bottle containing
pure air. Take a long straw, the hollow stem of a weed,
a glass tube, or a sheet of stiff paper rolled into a tube,
and pass the tube into the bottle through a hole in the
cardboard. Without drawing in a deep breath, send one
long breath into the bottle through the tube, emptying the
lungs by the breath as nearly as possible (Fig. 4). Next
invert the bottle on the table as in the former experiment,

THE PRINCIPLES OF BIOLOGY

afterward withdrawing the cardboard. Move the bottle
to the edge of the table and pass the lighted candle up
into it (Fig. 5). Does the flame go out as quickly as
in the former experiment ?

If you breathe through a tube into clear lime water,
the water turns milky. The effect of the breath on the
candle and on the lime water shows that carbon dioxid is
continually leaving our bodies in the breath.

FlG. 4. Breathing into a bottle. 1 FlG. 5. Testing the air in the bottle. 1

Oxidation and Deoxidation. The union of oxygen with
carbon and other substances, which occurs in fires and
in the bodies of animals, is called oxidation. The separa-
tion of the oxygen from carbon such as occurs in the
leaves of plants is called deoxidation. The first process
sets energy free, the other process stores it up. Animals
give off carbon dioxid from their lungs or gills, and plants
give off oxygen from their leaves. But plants need some
energy in growing, so oxidation also occurs in plants, but
to a far less extent than in animals. At night, because
of the absence of sunlight, no deoxidation is taking place

1 From Coleman's " Physiology for Beginners," Macmillan Co., N.Y.

6 ANIMAL BIOLOGY

in the plant, but oxidation and growth continue; so at
night the plant actually breathes out some carbon dio.rid.
The deepest part of the lungs contains the most carbon
dioxid. Why was it necessary to empty the lungs as
nearly as possible in the experiment with the candle ? Why
would first drawing a deep breath interfere with the experi-
ment ? Why does closing the draught of a stove, thus
shutting off part of the air, lessen the burning ? Why does
a " firefly " shine brighter at each breath ? Why is the pulse
and breathing faster in a fever ? Very slow in a trance ?

The key for understanding any animal is to find how
it gets food and oxygen, and how it uses the energy
thus obtained to grow, move, avoid its enemies, and get
more food. Because it moves, it needs senses to guide it.

The key for understanding a plant is to find how it gets
food and sunlight for its growth. It makes little provision
against enemies ; its food is in reach, so it needs no senses
to guide it. The plant is built on the plan of having the
nutritive activities near the surface (e.g. absorption by roots ;
gas exchange in leaves). The animal is built on the plan
of having its nutritive activities on the inside (e.g. digestion ;
breathing).

Cell and Protoplasm. Both plants and animals are
composed of small parts called cells. Cells are usually
microscopic in size. They have various shapes, as spheri-
cal, flat, cylindrical, fiber-like, star-shaped. The living
substance of cells is called protoplasm. It is a stiff, gluey
fluid, albuminous in its nature. Every cell has a denser
spot or kernel called a nucleus, and in the nucleus is a still
smaller speck called a nucleolus. Most cells are denser and
tougher on the outside, and are said to have a cell wall,
but many cells are naked, or without a wall. Hence the
indispensable part of a cell is not the wall but the nucleus,

THE PRINCIPLES OF BIOLOGY

and a cell may be defined as a bit of protoplasm containing
a nucleus. This definition includes naked cells as well as
cells with walls.

One-celled Animals. There are countless millions of
animals and plants the existence of which was not sus-
pected until the invention of the micro-
scope several centuries ago. They are
one-celled, and hence microscopic in size.
It is believed that the large animals and
plants are descended from one-celled ani-
mals and plants. In fact, each individual
plant or animal begins life as a single
cell, called an egg cell, and forms its
organs by the subdivision of the egg cell into many cells.
An egg cell is shown in Fig. 6, and the first stages in the
development of an egg cell are shown in Fig. 7.

The animals to be studied in the first chapter are one-
celled animals. To understand them we must learn how

FIG. 6. Egg cell of
mammal with yolk.

FlG. 7. Egg cell subdivides into many cells forming a sphere (morula) containing
a liquid. A dimple forms and deepens to form the next stage (gastrula).

they eat, breathe, feel, and move. They are called Pro-
tozoans (Greek protos, first; soon, life). All other animals
are composed of many cells and are called Metazoans
(Greek meta, beyond or after). The cells composing the
mucous membrane in man are shown in Fig. 8. The cellu-
lar structure of the leaf of a many-celled plant is illustrated
in Fig. i. (See also Chap. I, Human Biology.)

8

ANIMAL BIOLOGY

Method of Classifying Animals. - The various animals
display differences more or less marked. The question
arises, are not some of them more closely related than
others ? We conclude that they are, since the differ-
ence between some animals is very slight, while the
difference between others is quite marked.

To show the different steps in classi-
fying an animal, we will take an ex-
ample, the cow. Even little children
learn to recognize a cow, although indi-
vidual cows differ somewhat in form,
size, color, etc. The varieties of cows,
such as short-horn, Jersey, etc., all
form one species of animals, having the
scientific name taurus. Let us include
in a larger group the animals closest
akin to a cow. We see a cat, a bison,
and a dog ; rejecting the cat and the
dog, we see that the bison has horns,
hoofs, and other similarities. We in-
elude it with the cow in a genus called
2^os y calling the cow Bos taurus, and

. , . ,

the blson > Bos blSOn - The sacred COW

of India (Bos indicus) is so like the
cow and buffalo as also to belong in the genus Bos. Why
is not the camel, which, like Bos bison, has a hump, placed
in the genus Bos ?

The Old World buffaloes, - - most abundant in Africa
and India,- -the antelopes, sheep, goats, and several other
genera are placed with the genus Bos in a family called
the hollow-horned animals.

This family, because of its even number of toes and
the habit of chewing the cud, resembles the camel family,

FIG. 8. Mucous MEM-
BRANE formed of one
layer of cells. A few
cells secrete mucus.

THE PRINCIPLES OF BIOLOGY 9

the deer family, and several other families. These are all
placed together in the next higher systematic unit called
an order, in this case, the order of ruminants.

The ruminants, because they are covered with hair
and nourish the young with milk, are in every essential
respect related to the one-toed horses, the beasts of
prey, the apes, etc. Hence they are all placed in a
more inclusive division of animals, the class called
mammals.

All mammals have the skeleton, or support of the
body, on the inside, the axis of which is called the verte-
bral column. This feature also belongs to the classes
of reptiles, amphibians, and fishes. It is therefore
consistent to unite these classes by a general idea or
conception into a great branch of animals called the
vertebrates.

Returning from the general to the particular by succes-
sive steps, state the branch, class, order, family, genus,
and species to which the cow belongs.

The Eight Branches or Sub-kingdoms. - The simplest
classification divides the whole animal kingdom into
eight branches, named and characterized as follows, be-
ginning with the lowest : I. PROTOZOANS. One-celled.
II. SPONGES. Many openings. III. POLYPS. Circular;
cup-like ; having only one opening which is both mouth and
vent. IV. ECHINODERMS. Circular ; rough-skinned ; two
openings. V. MOLLUSKS. No skeleton ; usually with ex-
ternal shell. VI. VERMES. Elongate body, no jointed legs.
VII. ARTHROPODS. External jointed skeleton; jointed
legs. VIII. VERTEBRATES. Internal jointed skeleton with
axis or backbone.

CHAPTER II
PROTOZOA (One-celled Animals)

THE AMEBA

SUGGESTIONS. Amebas live in the slime found on submerged
stems and leaves in standing water, or in the ooze at the bottom.
Water plants may be crowded into a glass dish and allowed to
decay, and after about two weeks the ameba may be found in
the brown slime scraped from the plants. An ameba culture
sometimes lasts only three days. The most abundant supply
ever used by the writer was from a bottle of water where some
oats were germinating. Use ^ or -^ inch objective, and cover
with a thin cover glass. Teachers who object to the use of
the compound microscope in a first course should require a
most careful study of the figures.

FIG. 9. AMEBA PROTEUS, much enlarged.

10

PROTOZOA

II

PS:

EC.

EN

FIG. 10. AMEBA.

ci>, contractile vacuole; ec, ectoplasm; en,
endoplasm; , nucleus; ps, pseudopod;
ps' , pseudopod forming; ectoplasm pro-
trudes and endoplasm flows into it.

Form and Structure. The ameba (also spelled amoeba)
looks so much like a clear drop of jelly that a beginner
cannot be certain that he
has found one until it moves.
It is a speck of protoplasm
(Fig. 9), with a clear outer
layer, the ectoplasm ; and a
granular, internal part, the
endoplasm. Is there a dis-
tinct line between them ?
(Fig. 10.)

Note the central portion
and the slender prolonga-
tions or pseudopods (Greek,
false feet). Does the endoplasm extend into the pseudo-
pods ? (Fig. 10.) Are the pseudopods arranged with any
regularity ?

Sometimes it is possible to see a denser appearing por-
tion, called the nucleus ; also a clear space, the contractile
vacuole (Fig. 10).

Movements. - - Sometimes while the pseudopods are be-
ing extended and contracted, the central portion remains

in the same place (this is mo-
tioii). Usually only one pseudo-
pod is extended, and the body
flows into it ; this is locomotion
(Fig. 11). There is a new foot
made for each step.
Feeding. If the ameba crawls near a food particle, the
pseudopod is pressed against it, or a depression occurs (Fig.
12), and the particle is soon embedded in the endoplasm.
Often a clear space called a food vacuole is noticed around
the food particle. This is the water that is taken in with

FlG. ii. The same ameba seen
at different times.

12

ANIMAL BIOLOGY

the particle (Fig. 12). The water and the
particle are soon absorbed and assimilated
by the endoplasm.

Excretion.- -If a particle of sand or other
indigestible matter is taken in, it is left behind
as the ameba moves on. There is a clear
space called the contractile vacuole, which
slowly contracts and disappears, then reap-
pears and expands (Figs. 9 and 10). This
possibly aids in excreting oxidized or useless
material.

Circulation in the ameba consists of the
movement of its protoplasmic particles. It
lacks special organs of circulation.

Feeling. Jarring the glass slide seems to
be felt, for it causes the activity of the ameba
to vary. It does not take in for food every
particle that it touches. This may be the
beginning of taste, based upon mere chemical
affinity. The pseudopods aid in feeling.

Reproduction. Sometimes an ameba is seen

FIG. 12. --THE
AMEBA tak- dividing into two parts. A narrowing takes

ing food.

place in the middle; the nucleus also divides,
a part going to each portion (Fig. 13). The mother ameba
finally divides into two daughter amebas. Sex is wanting.
Source of the Ameba's Energy. - - We thus see that the
ameba moves without feet, eats without a mouth, digests
without a stomach, feels
without nerves, and, it
should also be stated,
breathes without lungs,
for oxygen is absorbed
from the water by its whole FIG. 13. AMEBA, dividing.

PROTOZOA 13

surface. Its movements require energy ; this, as in all ani-
mals, is furnished by the uniting of oxygen with the food.
Carbon dioxid and other waste products are formed by the
union ; these pass off at the surface of the ameba and taint
the water with impurities.

Questions. -- Why will the ameba die in a very small quantity of
water, even though the water contains enough food? Why will it die
still quicker if air is excluded from contact with the drop of water?

The ameba never dies of old age. Can it be said to be immortal?

According to the definition of a cell (Chapter /), is the ameba a
unicellular or multicellular animal?

Cysts. - - If the water inhabited by a protozoan dries up,
it encysts, that is, it forms a tough skin called a cyst.
Upon return of better conditions it breaks the cyst and
comes out. Encysted protozoans may be blown through
the air : this explains their appearance in vessels of water
containing suitable food but previously free from proto-
zoans.

THE SLIPPER ANIMALCULE OR PARAMECIUM

SUGGESTIONS. Stagnant water often contains the paramecium as
well as the ameba ; or they may be found in a dish of water con-
taining hay or finely cut clover, after the dish has been allowed to
stand in the sun for several days. A white film forming on the
surface is a sign of their presence. They may even be seen with
the unaided eye as tiny white particles by looking through the side
of the dish or jar. Use at first a \ or \ in. objective. Restrict
their movements by placing cotton fibers beneath the cover glass ;
then examine with \ or -J- objective. Otherwise, study figures.

Shape and Structure.- The paramecium's whole body,
like the ameba's, is only one cell. It resembles a slipper
in shape, but the pointed end is the hind end, \htfront end
being rounded (Fig. 14). The paramecium is propelled
by the rapid beating of numerous fine, threadlike append-

ANIMAL BIOLOGY

ages on its surface, called cilia (Latin, eyelashes) (Figs.).
The cilia, like the pseudopods of the ameba, are merely

prolongations of the cell protoplasm,
but they are permanent. The sepa-
ration between the outer ectoplasm
and the interior granular endoplasm
is more marked than in the ameba
(Fig. 14).

Nucleus and Vacuoles. There is
a large nucleus called the macro-
nucleus, and beside it a
smaller one called the
micronucleus. They are
hard to see. About one
third of the way from
each end is a clear, pul-
sating space (bb. Fig.
15) called the pulsat-
ing vacuole. These
spaces contract until
they disappear, and then
reappear, gradually ex-
panding. Tubes lead from the vacuoles which probably
serve to keep the contents of the cell in circulation.

Feeding. A depression, or groove, is seen on one side,
this serves as a mouth (Figs.). A tube which serves as a

gullet leads from the
mouth-groove to the in-
terior of the cell. The
mouth-groove is lined
with cilia which sweep

food particles inward.
-Two PARAMECIA exchanging

parts of their nuclei. The particles accumulate

FIG. 14. PARAMECIUM,
showing cilia, c.

Two contractile vacuoles, cv;
the macronucleus, mg;
two micronuclei, mi', the
gullet (ffi), a food ball
forming and ten food balls
in their course from gullet
to vent, a.

FIG. 15.

FIG. 16.

PROTOZOA

pj

in a mass at the inner end of the gullet, become separated
from it as a food ball (fig. 14), and sink into the soft pro-
toplasm of the body. The food balls
follow a circular course through the
endoplasm, keeping near the ectoplasm.
Reproduction. - This, as in the ameba,
is by division, the constriction being in
the middle, and part of the nucleus going
to each half. Sometimes two individ-
. uals come together with their

mouth-grooves touching and

exchange parts of their nuclei

(Fig. 16). They then separate

and each divides to form two

new individuals.

We thus see that the para-

mecium, though of only one

cell, is a mucJi more complex and advanced

animal than tJie ameba. The tiny paddles,

or cilia, the mouth-groove, etc., have their

special duties similar to the specialized organs
of the many-celled animals to be studied later.

If time and circumstances
allow a prolonged study, sev-
eral additional facts may be
observed by the pupil, e.g.
Does the paramecium swim
with the same end always
foremost, and same side
uppermost ? Can it move
backwards ? Avoid obsta-
cles ? Change shape in a
narrow passage ? Does refuse FIG. 19. SHELL OF A RADIOLARIAN.

FIG. 17. VORTI-

CELLA (or bell

animalcule), two

extended, one
withdrawn.

FIG. 18.
Euglena.

1 6 ANIMAL BIOLOGY

matter leave the body at any particular place ? Trace
movement of the food particles.

Draw the paramecium.

Which has more permanent parts, the ameba or para-
mecium ? Name two anatomical similarities and three dif-
ferences ; four functional similarities and three differences.

The ameba belongs in the class of protozoans called
Rkizopoda "root footed."

Other classes of Protozoans are the Infusorians (in the
broad sense of the term), which have many waving cilia
(Fig. 17) or one whip-like flagellum (Fig. 18), and the
Foraminifers, which possess a calcareous shell pierced with
holes (Fig. 19). Much chalky limestone has been formed
of their shells. To which class does the paramecium
belong ?

Protozoans furnish a large amount of food to the higher
animals.

To the Teacher. If plant, animal, and human biology are to be
given in one year as planned, and full time allowed for practical work,
the portions of the text in small type, as Chapter III, may be omitted
or merely read and discussed. Any two of the three parts forming the
course may be used for a year's course by using all of the text and
spending more time on practical and field work.

CHAPTER III

SPONGES

SUGGESTIONS. In many parts of the United States, fresh-water
sponges may, by careful searching, be found growing on rocks and logs
in clear water. They are brown, cream}-, or greenish in color, and re-
semble more a cushion-like plant than an animal. They have a char-
acteristic gritty feel. They soon die after removal to an aquarium.

A number of common small bath sponges may be bought and kept
for use in studying the skeleton of an ocean sponge. These sponges
should not have large
holes in the bottom ; if
so, too much of the
sponge has been cut
away. A piece of marine
sponge preserved in alco-
hol or formalin may be
used for showing the
sponge with its flesh in
place. Microscopic slides
may be used for showing
the spicules.

The small fresh-water
sponge (Fig. 21) lacks
the more or less vase-
like form typical of sponges. It is a rounded mass growing
upon a rock or log. As indicated by the arrows, where does

water enter the sponge? This
may be tested by putting color-
ing matter in the water near
the living sponge. Where does
the wafer come outt (Fig. 22.)
Does it pass through ciliated

FIG. 2i. FRESH-WATER SPONGE.

FIG. 22. SECTION of fresh-water sponge
(enlarged).

chambers in its course? Is the

i8

ANIMAL BIOLOGY

FIG. 23. EGGS and SPICULES of fresh-water
sponge (enlarged).

surface of the sponge rough or smooth? Do any of the skeletal
spicules show on the surface? (Fig. 21.) Does the sponge thin
out near its edge?

The egg of this sponge is shown in Fig. 23. It escapes from
the parent sponge through the osculum t or large outlet. As in

most sponges, the first
stage after the egg is
ciliated and free-swim-
ming.

Marine Sponges.
The grantia (Fig. 24) is
one of the simplest of
marine sponges. What is the shape of grantia? What is its length
and diameter? How does the free end differ from the fixed end?
Are the spicules projecting from its body few or many?
Where is the osculum, or large outlet? With what
is this surrounded? The osculum opens from a central
cavity called the cloaca. The canals from the pores
lead to the cloaca.

Buds are sometimes seen growing out from the
sponge near its base. These are young sponges formed
asexually. Later they become detached from the
parent sponge.

Commercial " Sponge." What part of the complete
animal remains in the bath sponge? Slow growing
sponges grow more at the top and form tall, simple,
tubular or vase-like animals. Fast growing sponges
grow on all sides at once and form a complicated system of canals,
pores, and oscula. Which of these habits of growth do you think

belonged to the bath sponge ? Is there a large
hole in the base of your specimen ? If so, this
is because the cloaca was reached in trimming
the lower part where it was attached to a rock.
Test the elasticity of the sponge when dry and
when wet by squeezing it. Is it softer when wet
or dry? Is it more elastic when wet or dry?
FIG 2< Plan of How many oscula does your specimen have?
a sponge. How many inhalent pores to a square inch ?

FIG. 24.

Grantia.

SPONGES

Using a probe (a wire with knob at end, or small hat pin), try
to trace the canals from the pores to the cavities inside.

Do the fibers of the sponge appear to
interlace, or join, according to any system?
Do you see any fringe-like growths on the
surface which show that new tubes are be-
ginning to form? Was the sponge growing
faster at the top, on the sides, or near the
bottom ?

Burn a bit of the sponge ; from the odor,

., . , e . -> FlG. 26. Bath Sponge.

what would you judge of its composition?

Is the inner cavity more conspicuous in a simple sponge or in a

compound sponge like the bath sponge? Is the bath sponge

FIG. 27. Bath Sponge.

FlG. 28. Bath Sponge.

branched or lobed? Compare a number of specimens (Figs. 26,
27, 28) and decide whether the common sponge has a typical

shape. What features do their forms
possess in common?

Sponges are divided into three classes,
according as their skeletons are flinty
(silicious), limy (calcareous), or horny.

Some of the silicious sponges have
skeletons that resemble spun glass in
their delicacy. Flint is chemically nearly
the same as glass. The skeleton shown
in Fig. 29 is that of a glass sponge which
lives near the Philippine Islands.

The horny sponges do not have spi-
cules in their skeletons, as the flinty and

limy sponges have, but the skeleton
FIG. 29. Skeleton of a

glass sponge. is composed of interweaving fibers of

2O

ANIMAL BIOLOGY

spoil gin, a durable substance of the same chemical nature as silk
(Figs. 30 and 31).

The limy sponges have skeletons made of numerous spicules of
lime. The three-rayed spicule is the commonest form.

The commercial sponge, seen as it grows in the ocean, appears
as a roundish mass with a smooth, dark exterior, and having about
the consistency of beef liver. Several large openings (oscula),
from which the water flows, are visible on the upper surface.
Smaller holes (inhalent pores --many of them so small as to be
indistinguishable) are on the sides. If the sponge is disturbed,

the smaller holes, and
perhaps the larger
ones, will close.

The outer layer of
cells serves as a sort
of skin. Since so
much of the sponge
is in contact with
water, most of the
cells do their own
breathing, or absorp-
tion of oxygen and giving off of carbon dioxid. Nutriment is
passed on from the surface cells to nourish the rest of the body.

Reproduction. Egg-cells and sperm-cells are produced by
certain cells along the canals. The egg-cell, after it is fertilized
by the sperm-cell, begins to divide and form new cells, some of
which possess cilia. The embryo sponge passes out at an oscu-
lum. By the vibration of the cilia, it swims about for a while.
It afterwards settles down with the one end attached to the ocean
floor and remains fixed for the rest of its life. The other end de-
velops oscula. Some of the cilia continue to vibrate and create
currents which bring food and oxygen.

The cilia in many species .are found only in cavities called
ciliated chambers. (Figs. 22, 32.) There are no distinct organs
in the sponge and there is very little specialization of cells. The
ciliated cells and the reproductive cells are the only specialized
cells. The sponges were for a long time considered as colonies
of separate one-celled animals classed as protozoans. They are,

FlG. 30. A horny
sponge.

FlG. 31. Section
of horny sponge.

SPONGES

21

without doubt, many-celled animals. If a living sponge is cut
into pieces, each piece will grow and form a complete sponge.

That the sponge is not a colony of one-celled animals, each like
an ameba, but is a many-celled animal, will be realized by exam-
ining Fig. 32, which shows a bit of sponge highly magnified. A
sponge may be conceived as having developed from a one-celled
animal as follows : Sev-
eral one-celled animals
happened to live side by
side ; each possessed a
thread-like flagellurn (E,
Fig. 32) or whip-lash for
striking the water. By
lashing the water, they
caused a stronger cur-
rent (Fig. 25) than pro-
tozoans living singly
could cause. Thus they
obtained more food and
multiplied more rapidly
than those living alone.
The habit of working
together left its impress
on the cells and was trans-
mitted by inheritance.

Cell joined to cell
formed a ring ; ring

FlG. 32. Microscopic plan of ciliated chamber.
Each cell lining the chamber has a nucleus,
a whip-lash, and a collar around base of
whip-lash. Question : State two uses of
whip-lash.

joined to ring formed a tube which was still more effective than
a ring in lashing the water into a current and bringing fresh food
(particles of dead plants and animals) and oxygen.

Few animals eat sponges ; possibly because spicules, or fibers,
are found throughout the flesh, or because the taste and odor are
unpleasant enough to protect them. Small animals sometimes
crawl into sponges to hide. One sponge grows upon shells in-
habited by hermit crabs. Moving of the shell from place to place
is an advantage to the sponge, while the sponge conceals and thus
protects the crab.

Special Report : Sponge " Fisheries." (Localities; how sponges
are taken, cleaned, dried, shipped, and sold.)

CHAPTER IV

FIG. 33.-
A HYDRA.

POLYPS (CUPLIKE ANIMALS)

THE HYDRA, OR FRESH WATER POLYP

SUGGESTIONS. - - Except in the drier regions of the United States,
the hydra can usually be found by careful search in fresh water ponds
not too stagnant. It is found attached to stones, sticks, or leaves,
and has a slender, cylindrical body from a quarter to half an
inch long, varying in thickness from that of a fine
needle to that of a common pin. The green hydra
and the brown hydra, both very small, are common
species, though hydras are often white or colorless.
They should be kept in a large glass dish filled with
water. They may be distinguished by the naked
eye but are not studied satisfactorily without a
magnifying glass or microscope. Place a living specimen attached
to a bit of wood in a watch crystal filled with water, or on a hol-
lowed slip, or on a slip with a bit of weed to support the cover
glass, and examine with hand lens or lowest power of microscope.
Prepared microscopical sections, both transverse and longitudinal,
may be bought
of dealers in mi-
croscopic sup-
plies. One is
shown in Fig. 39.

Is the hy-
dra's body
round or two-
sided ? (Fig.
35.) What is

FlG. 34, Forms assumed by Hydra.

its general sJiape ? Does one individual keep the same
shape ? (Fig. 34.) How does the length of the thread-

22

POLYPS (CUPLIKE ANIMALS}

like tentacles compare with the length of the hydra's body ?
About how many tentacles are on a hydra's body ? Do all
have the same number of tentacles ? Are the tentacles
knotty or smooth ? (Fig. 35.) The hydra is usually ex-
tended and slender ; sometimes it is contracted and rounded.
In which of these conditions is the base (the foot) larger
around than the rest of the body ? (Fig. 34.) Smaller ?
How many openings into the
body are visible ? Is there a
depression or an eminence at
the base of the tentacles ? For
what is the opening on top of
the body probably used ? Why
are the tentacles placed at the
top of the hydra's body ? Does
the mojitJi have the most con-
venient location possible ?

The conical projection bear-
ing the month is called hypo-
stome (Fig. 34). The mouth
opens into the digestive cavity.
Is this the same as the general
body cavity, or does the stomach have a wall distinct from
the body cavity f How far down does the body cavity
extend ? Does it extend up into the tentacles ? (Fig. 39.)

If a tentacle is touched, what happens? Is the body ever bent?
Which is more sensitive, the columnar body or the tentacles? In
searching for hydras would you be more likely to find the ten-
tacles extended or drawn in? Is the hypostome ever extended
or drawn in? (Fig. 34.)

Locomotion. - The round surface, or disk, by which the
hydra is attached, is called its foot. Can you move on
one foot without hopping ? The hydra moves by alter-

FIG. 35. HYDRA (much
enlarged).

ANIMAL BIOLOGY

FIG. 36. NETTLING CELL.

II. discharged, and I. not discharged.

nately elongating and rounding the foot. Can you dis-
cover other ways by which it moves ? Does the hydra
always stand upon its foot ?

Lasso Cells. Upon the tentacles (Fig. 35) are numer-
ous cells provided each with a thread-like process (Fig. 36)

which lies coiled within the
cell, but which may be
thrown out upon a water
flea, or other minute animal
that comes in reach. The
touch of the lasso paralyzes
the prey (Fig. 37). These
cells are variously called
lasso cells, nettling cells, or
thread cells. The thread is
hollow and is pushed out by the pressure of liquid within.
When the pressure is withdrawn the thread goes back as
the finger of a glove may be turned back into the glove by
turning the finger outside in.

When a minute animal, or
other particle of food comes in
contact with a tentacle, how
does the tentacle get the food
to the mouth ? By bending
and bringing the end to the
mouth, or by shortening and
changing its form, or in both
ways ? (Fig. 34, C.) Do the
neighboring tentacles seem to
bend over to assist a tentacle in
securing prey ? (Fig. 34, C.)
Digestion. The food parti-

f IG. 37. HYDRA capturing a

cles break up before remaining water flea.

POLYPS {CUPLIKE ANIMALS}

long in the stomach, and the nutritive part is absorbed
by the lining cells, or endoderm (Fig. 39). The indiges-
tible remnants go out through the mouth. The hydra is
not provided with a special vent. Why could the vent not
be situated at the end opposite the mouth ?

Circulation and Respiration. - - Does water have free
access to the body cavity ? Does the hydra have few or
nearly all of its cells exposed to the water in which it
lives ? From its structure, decide whether it can breathe
like a sponge or whether
special respiratory cells are
necessary to supply it with
oxygen and give off carbon
dioxid. Blood vessels are
unnecessary for transfer-
ring oxygen and food from
cell to cell.

Reproduction. - Do you
see any swellings upon the
side of the hydra ? (Fig. 34, A.) If the swelling is near
the tentacles, it is a spcnnary ; if near the base it is an
ovary. A sperm coalesces with or fertilizes the ovum after
the ovum is exposed by the breaking of the ovary wall.
Sometimes the sperm from one hydra unites with the ovum
of another hydra. This is called cross-fertilization. The
same term is applied to the process in plants when the
male element, developed in the pollen of the flower, unites
with the female element of the ovule of the flower on
another plant. The hydra, like most plants and some other
animals, is hermaphrodite, that is to say, both sperms and
ova are produced by one individual. In the autumn, eggs
are produced with hard shells to withstand the cold until
spring. Sexual reproduction takes place when food is

FIG. 38. HYDRAS on pondweed.

26

ANIMAL BIOLOGY

scarce. Asexual generation (by budding) is common with
the hydra when food supply is abundant. After the bud

grows to a cer-
tain size, the
outer layer of
cells at the base
of the bud con-
stricts and the
young hydra is
detached.

Compare the
sponge and the
hydra in the fol-
lowing respects:
- many celled,
or one celled ;

obtaining food ;
breathing; tubes
and cavities ;
openings ; re-
production ; loco-
motion. Which
ranks higher

ECTODERM CELLS
INTERSTITAL DO
MUSCLE LAYER

MESOGLCEA
ENDODERM CELL

OVARY-
OVUM

FLAGE1LA
ENTERIC CAVITY*

FlG. 39. Longitudinal section of hydra (microscopic
and diagrammatic).

among the metazoa ? The metazoa, or many celled ani-
mals, include all animals except which branch ?

Figure 39 is a microscopic view of a vertical section of a hydra to
show the structure of the body wall. There is an outer layer called the
ectoderm, and an inner layer called the endodenn. There is also a thin
supporting layer (black in the figure) called the mesoglea. The mesoglea
is the thinnest layer. Are the cells larger in the endoderm or the ectoderm ?
Do both layers of cells assist in forming the reproductive bud ? The ecto-
derm cells end on the inside in contractile tails which form a thin line and
have the effect of muscle fibers. They serve the hydra for its remarkable
changes of shape. When the hydra is cut in pieces, each piece makes a
complete hydra, provided it contains both endoderm and ectoderm.

POLYPS (CUPLIKE ANIMALS} 2/

In what ways does the hydra show " division of labor " ? Answer
this by explaining the classes of cells specialized to serve a different
purpose. Which cells of the hydra are least specialized? In what par-
ticulars is the plan of the hydra different from that of a simple sponge ?
An ingenious naturalist living more than a century ago, asserted that it
made no difference to the hydra whether the ectoderm or the endoderm
layer were outside or inside, - - that it could digest equally well with
either layer. He allowed a hvdra to swallow a worm attached to a

j *

thread, and then by gently pulling in the thread, turned the hydra inside
out. More recently a Japanese naturalist showed that the hydra could
easily be turned inside out, but he also found that when left to itself
it soon reversed matters and returned to its natural condition, that
the cells are really specialized and each layer can do its own work and
no other.

Habits. The hydra's whole body is a hollow bag, the
cavity extending even into the tentacles. The tentacles
may increase in number as the hydra grows but seldom
exceed eight. The hydra has more active motion than
locomotion. It seldom moves from its place, but its ten-
tacles are constantly bending, straightening, contracting,
and expanding. The body is also usually in motion, bend-
ing from one side to another. When the tentacles ap-
proach the mouth with captured prey, the mouth (invisible
without a hand lens) opens widely, showing five lobes or
lips, and the booty is soon tucked within. A hydra can
swallow an animal larger in diameter than itself.

The endoderm cells have ameboid motion, that is, they
extend pseudopods. They also resemble amebas in the
power of intra-cellular digestion ; that is, they absorb the
harder particles of food and digest them afterwards, re-
jecting the indigestible portions. Some of these cells have
flagella (see Fig. 39) which keep the fluid of the cavity
in constant motion.

Sometimes the hydra moves after the manner of a small
caterpillar called a " measuring worm," that is, it takes
hold first by the foot, then by the tentacles, looping its

28

ANIMAL BIOLOGY

body at each step. Sometimes
the body goes end over end in
slow somersaults.

The length of the extended
hydra may reach one half
inch. When touched, both
tentacles and body contract
until it looks to the unaided
eye like a round speck of

icily. This shows sensibility,
FIG. 40. HYDROID COLONY, with J

nutritive (P) reproductive (M) and and a few Small Star-shaped

defensive (S) hydranths. ce]ls are believed to be nerve

cells, but the hydra has not a nervous system. Hydras
show their liking for light by moving to the side of
the vessel or aquarium whence the light comes.

The Branch Polyps
(sometimes called Ccelen-
teratd). The hydra is
the only fresh water rep-
resentative of this great
branch of the animal
kingdom. This branch
is characterized by its
members having only
one opening to the body.
The polyps also include
the salt water animals
called hydro ids, jelly-
fishes, and coral polyps.

Hydroids. - - Figure 40
shows a hydro id, or
group of hydra-like
growths, one of which

FIG. 41. " PORTUGUESE MAN-O'-WAR"
(compare with Fig. 40). A floating
hydroid colony with long, stinging (and
sensory) streamers. Troublesome to
bathers in Gulf of Mexico. Notice
balloon-like float.

POLYPS {CUPLIKE ANIMALS}

eats and digests for the group, another defends by nettling
cells, another produces eggs. Each hydra-like part of a
hydroid is called a hydranth. Sometimes the buds on the
hydra remain attached so long that a bud forms upon the
first bud. Thus three generations are represented in one
organism. Such growths show us that it is not always
easy to tell
what consti-
tutes an indi-
vidual animal.
Hydro ids
may be con-
ceived to have
been developed
by the failure
of budding hy-

QraS LO Sepa-
rate from the

parent, and by
the gradual formation of the habit of living together and
assisting each other. When each hydranth of the hydroid
devoted itself to a special function of digestion, defense, or
reproduction, this group lived longer and prospered ; more
eggs were formed, and the habits of the group were trans-
mitted to a more numerous progeny than were the habits
of a group where members worked more independently of
each other.

As the sponge is a simple example of the devotion
of special cells to special purposes, the hydroid is a
primitive and simple example of the occurrence of organs,
that is of special parts of the body set aside for a special
work.

FlG. 42. --The formation of many free swimming jelly-
fishes from one fixed hydra-like form. The saucer-like
parts (h) turn over after they separate and become like
Fig. 43 or 44. Letters show sequence of diagrams.

ANIMAL BIOLOGY

How many mature hydranths are seen in the hydroid
shown in Fig. 40? Why are the defensive hydranths

on the outside of the
colony ? Which hy-
dranths have no tenta-
cles ? Why not ?

Jellyfish. Alterna-
tion of Generations. -
Medusa. With some
species of hydroids, a
very curious thing hap-
pens. The hydranth
tJiat is to produce tJie
eggs falls off and be-
comes independent of

the colony. More sur-
prising ^ ^ appear _

FIG. 43- - A JELLYFISH.

ance changes entirely and instead of being hydra-like, it

becomes the large and complex creature called jellyfish

(Fig. 43). But

the egg of tJie

jellyfish pro-

duces a small

hydra- like ani-

mal 'which gives

rise by budding

to a hydroid)

and the cycle is

complete.

The bud (or
reproductive
hydranth) of
the hydroid FIG. 44 . A JELLYFISH (medusa).

POLYPS (CUPLIKE ANIMALS}

does not produce a hydroid, but a jellyfish; the egg of the
jellyfish does not produce a jellyfish, but a hydroid. This is
called by zoologists, alternation of generations. A complete
individual is the life from the germination of one egg to
the production of another. So that an "individual' con-
sists of a hydroid colony fixed in one place together with
all the jellyfish produced from its buds, and which may
now be floating miles away from it in the ocean. Bathers
in the surf are sometimes touched and stung by the long,
streamer-like tentacles of the jellyfish. These, like the
tentacles of the hydra, have
nettling cells (Fig. 41).

The umbrella-shaped free
swimming jellyfish is called a
medusa (Fig. 44).

Coral Polyps. Some of the
salt water relatives of the hydra
produce buds which remain
attached to the parent without,
however, becoming different
from the parent in any way.
The coral polyps and corallines are examples of colonies of
this kind, possessing a common stalk which is formed as
the process of multiplication goes on. In the case of coral
polyps, the separate animals and the flesh connecting them
secrete within themselves a hard, limy, supporting structure
known as coral. In some species, the coral, or stony part,
is so developed that the polyp seems to be inserted in the
coral, into which it withdraws itself for partial protection

(Fig. 45).

The corallines secrete a smooth stalk which affords
no protection, but they also secrete a coating or sheath
which incloses both themselves and the stalk, The

FIG. 45. CORAL POLYPS (tenta-
cles, a multiple of six). Notice
hypostome.

ANIMAL BIOLOGY

coating has apertures through which the polyps pro-
trude in order to feed when no danger is near (Fig. 46).

FIG. 46. RED CORAL-
LINE with crust and
polyps (eight tentacles) .

FIG. 47. SEA FAN (a coralline).

The red " corals " used for jewelry are bits of stalks of cor-
allines. The corallines (Figs. 47, 48) are not so abundant

nor so important
as the coral polyps
(Figs. 45, 49).

Colonies of coral
polyps grow in
countless numbers
in the tropical seas.
The coral formed
by successive colo-
nies of polyps accu-
mulates and builds
up many islands

FIG. 48. -ORGAN PIPE "Coral" (a coralline). and important addi-

tions to continents. The Florida " keys," or islands, and
the southern part of the mainland of Florida were so
formed.

POLYPS (CUPLIKE ANIMALS}

33

The Sea Anemone, like the coral
polyp, lives in the sea, but like
the fresh water hydra, it deposits
no limy support for its body. The
anemone is much larger than the

hydra and
most coral
polyps,
many spe-
cie s at-
taining a
height of
several
inches. It

FIG. 49. UPRIGHT CUT
through coral polyp X 4.

ms, mouth; tnr, gullet; Is,
Is, fleshy partitions (mesen-
teries) extending from outer
body wall to gullet (to in-
crease absorbing surface) ;
s, s, shorter partitions ; nib,
fb, stony support (of lime,
called coral) ; t, tentacles.

FIG. 50. SEA ANEMONE.

does not
form colo-
nies. When its arms are drawn in,

it looks like a large knob of shiny but opaque jelly. Polyps
used to be called zoophytes (plant- animals), because of
their flower-like appearance (Figs. 50, 51).

FJG. 51. SEA ANEMONES.

CHAPTER V

ECHINODERMS (SPINY ANIMALS)

THE STARFISH
SUGGESTIONS. Since the echinoderms are aberrant though inter-

o

esting forms not in the regular line of development of animals, this

chapter may be
omitted if it
is desired to
shorten the
course. The
common star-
fish occurs
along the At-
lantic coast. It
is captured by

wading

along

FIG. 52. Starfish on a rocky shore.

\

the shore when
the tide is out.

It is killed by immersion in warm, fresh water. Specimens are usually

preserved in 4 per cent formalin. Dried starfish and sea urchins are also

useful. A living starfish kept

in a pail of salt water will be

instructive.

External Features.
Starfish are usually brown
or yellow. Why? (See
Fig. 52.) Has it a head or
tail? Right and left sides?
What is the shape of the

4'
FIG. 53. PLAN of starfish ; III, madreporite.

disk, or part which bears
the five arms or rays ? (Fig. 53.) Does the body as a whole
have symmetry on two sides of a line (bilateral symmetry), or
around a point (radial symmetry) ? Do the separate rays have

34

ECHINODERMS (SPINY ANIMALS}

35

FlG. 55. Starfish (showing
MADREPORITE) .

bilateral symmetry ? The skeleton consists of limy plates embedded

in the tough skin (Fig. 54). Is the skin rough or smooth? Hard

or soft? Are the projections (or spines]

in the skin long or short? The skin is

hardened by the
limy plates, ex-
cept around the
mouth, which is FIG. 54. LIMY PLATES

at the center of in portion of a ray "
the lower side and surrounded by a mem-
brane. Which is rougher, the mouth side,
(oral 'side) or the opposite (#&?ra/side)?
Which side is more nearly flat ? The
vent is at or near the center of the
disk on the aboral surface. It is usually

very small and sometimes absent. Why a vent is not of much

use will be understood after learning how the starfish takes food.
An organ peculiar to animals of this

branch, and called the madreporic plate,

or madreporite t is found on the aboral

surface between the bases of two rays

(Fig. 55). It is wartlike, and usually

white or red. This plate is a sieve ; the

small openings keep out sand but allow

water to filter through.

Movements : the Water-tube System.

The water, which is filtered through

the perforated madreporite, is needed

to supply a system of canals (Fig. 56).

The madreporite opens into a canal

called the stone canal, the wall of which

is hardened by the same kind of mate-
rial as that found in the skin. The stone
canal leads to the ring canal which sur-
rounds the mouth (Fig. 56). The ring
canal sends radial canals into each ray to supply the double row
of tube feet found in the groove at the lower side of each ray
(Fig. 57). Because of their arrangement in rows, the feet are

FIG. 56. WATER tube
SYSTEM of starfish.

in, madreporite; sic, stone
canal; ap, ampulla.

ANIMAL BIOLOGY

also called ambithtcral feet (Latin ambulacra, " forest walks").

There is a water holder (ampulla), or muscular water bulb at the

base of each
tube foot (Fig.
58). These con-
tract and force
the water into
the tube feet and
extend them.
The cuplike
ends of the
tubes cling to
the ground by
suction. The
feet contain
delicate muscles
by which they
contract and
shorten. Thus
the animal pulls
itself slowly

along, hundreds of feet acting together. The tube feet, for their

own protection, may contract and retire into the groove, the

water which extended them being sent back into the ampulla.

This system of water

vessels (or water-

vascular system) of

the echinodermata

is characteristic of

them ; i.e. is not

found elsewhere in

the animal kindom.

FlG. 57. Starfish, from below; tube feet extended.

/?

FIG. 58.

The grooves and the

plates on each side

of them occupy the

ambulacral areas. The rows of spines on each side of the grooves

are freely movable. (What advantage?) The spines on the aboral

surface are not freely movable.

SECtlON OF ONE RAY arfd central portion
of starfish.

f\i fit fz> tube feet more or less extended; an, eye spot;
k, gills; da, stomach; in, madreporite; st, stone canal;
p, ampulla; ei, ovary.

ECHINODERMS (SPINY ANIMALS} 37

Respiration.- -The system of wafer vessels serves the additional
purpose of bringing water containing oxygen into contact with
various parts of the body, and the starfish was formerly thought
to have no special respiratory organs. However there are holes in
the aboral wall through which the folds of the delicate lining mem-
brane protrude. These are now supposed to be gills (k, Fig. 58).

The nervous system is so close to the aboral surface that much
of it is visible without dissection. Its chief parts are a nen>e ring
around the mouth, which sends off a branch along each ray.
These branches may be seen by separating the
rows of tube feet. They end in a pigmented i
cell at the end of each ray called the eye-spot.

The food of starfish consists of such animals
as crabs, snails, and oysters. When the prey
is too large to be taken into the mouth, the
starfish turns its stomach inside out over
the prey (Fig. 59). After the shells separate,
the stomach is applied to the soft digestible
parts. After the animal is eaten, the stomach FIG. 59. Starfish cat-
is retracted. This odd way of eating is very

..... r b, stomach everted.

economical to its digestive powers, for only
that part of the food which can be digested and absorbed is taken
into the body. Only the lower part of the stomach is wide and
extensible. The upper portion (next to the aboral surface) is
not so wide. This portion receives the secretion from five
pairs of digestive glands, a pair of which is situated in each ray.
Jaws and teeth are absent. (Why?) The vent is sometimes
wanting. Why ?

Reproduction.- -There is a pair of ovaries at the base of each
ray of the female starfish (Fig. 58). The spermaries of the male
have the same position and form as the ovaries, but they are
lighter colored, usually white. 1

Regeneration after Mutilation. - - If a starfish loses one or more
rays, they are replaced by growth. Only a very ignorant oyster-
man, angry at the depredations of starfish upon his oyster beds,

L The sperm cells and egg cells are poured out into the water by the adults,
and the sperm cell, which, like nearly all sperm cells, has a vibratory, tail-
like flagellum to propel it, reaches and fertilizes the egg cell.

ANIMAL BIOLOGY

would chop starfish to pieces, as this only serves to multiply them.
This power simulates multiplication by division in the simplest
animals.

Steps in Advance of Lower Branches. The starfish and other
echinodermata have a more developed nervous system, sensory
organs, and digestion, than forms previously studied ; most dis-
tinctive of all, they have a body
cavity distinct from the food
cavity. The digestive glands,
reproductive glands, and the
fluid which serves imperfectly
for blood, are in the body
cavity. There is no heart or
blood vessels. The motions
of the stomach and the bend-
ing of the rays give motion to
this fluid in the body cavity.
It cannot be called blood,
but it contains white blood
corpuscles.

The starfish when first
hatched is an actively swim-
ming bilateral animal, but it soon becomes starlike (Fig. 60). The
limy plates of the starfish belong neither to the outer nor inner
layer (endoderm and ectoderm) of the body wall, but to a third
or middle layer (mesoderm) ; for echinoderms, like the polyps,
belong to the three-layered animals. In this its skeleton differs
from the shell of a crawfish, which is formed by the hardening
of the skin itself.

Protective Coloration. - - Starfish are brown or yellow. This
makes them inconspicuous on the brown rocks or yellow sands
of the seashore. This is an example of protective coloration.

THE SEA URCHIN

External Features. - - What is the shape of the body ? What
kind of symmetry has it? Do you find the oral (or mouth) sur-
face? The aboral surface? Where is the body flattened? What
is the shape of the spines? What is their use? How are the tube

FlG. 60. Young starfish crawling upon
their mother. (Challenger Reports.)

ECHINODERMS (SPINY ANIMALS}

39

feet arranged? Where do the rows begin and end? Would you
think a sea urchin placed upside down in water, could right itself
less or more readily than a star-
fish? What advantage in turn-
ing would each have that the
other would not have? The
name sea urchin has no refer-
ence to a mischievous boy, but
means sea hedgehog (French
oursin, hedgehog), the name
being suggested by its spines.
Comparison of Starfish and
Sea Urchin. The water sys-
tem of the sea urchin, consist-
ing of madreporite, tubes, and
water bulbs, or ampullae, is
similar to that of the starfish.

FIG. 61. A SEA URCHIN crawling up
the glass front wall of an aquarium
(showing mouth spines and tube feet).

The tube feet and locomotion are alike. There is no need for
well-developed respiratory organs in either animal, as the whole
body, inside and out, is bathed in water. The method of repro-
duction is the same.

The starfish eats soft animal food. The food of the sea
urchin is mainly vegetable, and it needs teeth (Fig. 62, 63 );

-fc,-jKii^'e^ =;= ' ..~'-a

FIG. 62. A SEA URCHIN
with spines removed,
the limy plates showing
the knobs on which the
spines grew.

FIG. 63. SECTION OF SEA URCHIN
with soft parts removed, showing the
jaws which bear the teeth protruding
in Fig. 6e.

its food tube is longer than that of a starfish, just as the food tube
of a sheep, whose food digests slowly, is much longer than that of
a dog.

ANIMAL BIOLOGY

The largest species of sea urchins are almost as big as a
child's head, but such size is unusual. The spines are mounted

on knobs, and the joint resembles a
ball-and-socket joint, and allows a wide
range of movement. Some sea urchins
live on sandy shores, other species live
upon the rocks. The sand dollars are
lighter colored. (Why?) They are usu-
ally flatter and have lighter, thinner
walls than the other species. The five-
holed sand cake or sand dollar has its
weight still further diminished by the
holes, which also allow it to rise more
easily through the water.

Both starfish and sea urchin rest on
the flattened lower surface of the body,
while the tube feet are stretching for-
ward for another step.

OTHER ECHINODERMS
The sea cucumbers, or holothurians, re-

semble the sea urchin in many respects, ^^^ A ^^-~ : - 1:"^

FIG. 64. --THE SEA OT-
TER, an urchin with
mouth (<?) and vent (A)
on same side of body.

SP^' '

FIG. 65. SEA CUCUMBERS.

but their bodies are elon-
gated, and the limy plates
are absent or very mi-
nute. The mouth is sur-
rounded by tentacles (Fig.

65)-

The brittle stars resem-
ble the starfish in form,
but their rays are very
slender, more distinct

from the disk, and the tube feet are on the edges of the rays, not

under them (Fig. 66).

FIG. 66. A BRITTLE STAR.

ECHINODERMS (SPINY ANIMALS}

FIG. 67.-

CRINOID,
arms closed.

The crinoids are the most ancient of the echino-
derms. (Figs. 67, 68.) Their fossils are very
abundant in the rocks. They
inhabited the geological seas,
and it is believed that some of
the other echinoderms de-
scended from them. A few
now inhabit the deep seas.
Some species are fixed by
stems when young, and later
break away and become free-
swimming, others remain
fixed throughout life.

The four classes of the branch echinoderms are
Starfish (asteroids], Sea urchins (echincids). Sea
cucumbers (holothurians}, and Sea lilies {crinoids] .

Comparative Review

.Make a table like this as large as the page of the
notebook will allow, and fill in without guessing.

1!

FIG. 68. DISK OF CRI-
NOID from above, show-
ing mouth in center
and vent near it, at
right (arms removed).

AMEBA

SPONGE

HYDRA

CORAL
POLYP

STARFISH

Is body round, two-
sided, or irregular

What organs of sense

Openings into body

Hard or supporting
parts of body

How food is taken

How move

How breathe

CHAPTER VI

WORMS

SUGGESTIONS : - - Earthworms may be found in the daytime after
a heavy rain, or by digging or turning over planks, logs, etc., in
damp places. They may be found on the surface at night by
searching with a lantern. Live specimens may be kept in the
laboratory in a box packed with damp (not wet) loam and dead
leaves. They may be fed on bits of fat meat, cabbage, onion,
etc., dropped on the surface. When studying live worms, they
should be allowed to crawl on damp paper or wood. An earth-
worm placed in a glass tube with rich, damp soil, may be watched
from day to day.

External Features. Is the body bilateral? Is there a
dorsal and ventral surface ? Can you show this by a test
with live worm ? Do you know of an animal with dorsal

and ventral surface, but not
bilateral ?

Can you make out a head ?

A head end ? A neck ? Touch
FIG. 69. -AN EARTHWORM. the head and tegt whether it

can be made to crawl backwards. Which end is more
tapering ? Is the mouth at the tip of the bead end or on
the upper or lower surface ? How is the vent situated ?
Its shape ? As the worm lies on a horizontal surface, is
the body anywhere flattened ? Are there any very distinct
divisions in the body ? Do you see any eyes ?

Experiment to find whether the worm is sensitive (i) to touch t
(2) to light, (3) to strong odors, (4) to irritating liquids. Does it
show a sense of taste ? The experiments should show whether

42

WORMS

43

it avoids or seeks a bright light, as a window ; also whether any
parts of the body are especially sensitive to touch, or all equally
sensitive. What effect when a bright light is brought suddenly near
it at night ?

Is red blood visible through the skin ? Can you notice
any pulsations in a vessel along the back ? Do all earth-
worms have the same number of divisions or rings ? Com-
pare the size of the rings or segments. Can it crawl faster
on glass or on paper ?

A magnifying glass will show on most species tiny bristle-
like projections called seta. How are the setae arranged ?
(d, Fig. 70.) How many on
one ring of the. worm ? How
do they point ? Does the worm
feel smoother when it is pulled
forward or backward between

FIG. 70. MOUTH AND

the fingers ? Why ? Are setae on the lower sur-
face ? Upper surface ? The sides ? What is the
use of the setae ? Are they useful below ground ?
Does the worm move at a uniform 'rate ? What
change in form occurs as the front part of the
body is pushed forward ? As the hinder part is
pulled onward ? How far does it go at each
movement ? At certain seasons a broad band,
or ring, appears, covering several segments and
making them seem enlarged (Fig. 71). This is
the clitellnm^ or reproductive girdle. Is this girdle
nearer the mouth or the tail ?

Draw the exterior of an earthworm.
Dorsal and Ventral Surfaces. - The earthworm
always crawls with the same surface to the ground ; this
is called the ventral surface, the opposite surface is the
dorsal surface. This is the first animal studied to which

FIG. 71.
EARTH-
WORM,

mouth end
above.

44

FIG. 72. FOOD
TUBE of earth-
worm. (Top
view.)

ANIMAL BIOLOGY

these terms are applicable. What are the
ventral and dorsal surfaces of a fish, a frog,
a bird, a horse, a man ?

The name "worm " is often carelessly applied
to various crawling things in general. It is prop-
erly applied, however, only to segmented animals
without jointed appendages.
Although a caterpillar crawls,
it is not a worm for several
reasons. It has six jointed
legs, and it is not a developed
animal, but only an early stage
in the life of a moth or but-
terfly. A " grubworm ' also
has jointed legs (Fig. 167).
It does not remain a grub, but
in the adult stage is a beetle.
A worm never develops into N.S*- |
another animal in the latter
part of its life ; its setae are
not jointed.

N.S.

C.L

The Food "Tube. The earthworm has
no teeth, and the food tube, as might be
inferred from the form of the
body is simple and straight. Its
parts, recognizable because of
slight differences in size and
structure, are named the pharynx
(muscular), gullet, crop, gizzard

FIG. 73. FOOD
TUBE AND
BLOOD VES-
SELS of earth-
worm showing
the ring-like
hearts. (Side
view.)

FIG. 74.

(muscular), and stomach-intestine. The last ex-
tends through three fourths of the length of the
body (Fig. 72). The functions of the parts of
the food tube are indicated by their names.

Circulation. There is a large dorsal blood
vessel above the food tube (Fig. 73). From the

WORMS

45

front portion of this tube arise several large tubular rings
or " hearts " which are contractile and serve to keep the
blood circulating. They lead to a ventral vessel below the
food tube (Fig. 74). The blood is red, but the coloring
matter is in the liquid, not in the blood cells.

Nervous System. Between the ventral blood vessels
is a nerve cord composed of two strands (see Fig. 75).
There is a slight swelling, or ganglion, on each strand, in
each segment (Fig. 75). The strands sepa-
rate near the front end of the worm, and a
branch goes up each side of the gullet and
enters the two pear-shaped cerebral ganglia,
or. "brain" (Fig. 75).

Food. The earthworm eats earth contain-
ing organic matter, the inorganic part passing
through the vent in the form of circular casts;
these are found in the morning at the top of
the earthworm's burrow.

The earthworm has no teeth. It excretes
through the mouth an alkaline fluid which
softens and partly digests the food before it
is eaten. When this fluid is poured out upon a green leaf,
the leaf at once turns brown. The starch in the leaf is
also acted upon. The snout aids in pushing the food into
the mouth.

Kidneys. - - Since oxidation is occurring in its tissues,
and impurities are forming, there must be some way of
removing impurities from tJie tissues. The earthworm
does not possess one-pair organs like the kidneys of
higher animals to serve this purpose, but it has numerous
pairs of small tubular organs called ncphridia which serve

*

the purpose. Each one is simply a tube with several coils.
There is a pair on the floor of each segment. Each neph-

FIG. 75.

GANGLIA

NEAR MOUTH

and part of
nerve chain of

earthworm.

4 6

ANIMAL BIOLOGY

Wtr

FIG. 76. Two PAIRS

OF NEPHRIDIA in a

worm (diagram).

ridium has an inner open end within the body cavity, and

its outer end opens by a pore on the surface between the

setae. The nephridia absorb waste
from the liquid in the celom, or body
cavity surrounding the food tube,
and convey it to the outside.

Respiration. - The skin of the
earthworm is moist, and the blood
capillaries approach so near to the
surface of the body that the oxygen
is constantly passing in from the air,
and carbon dioxid passing out ; hence

it is constantly breathing through all parts of its skin.

// needs no lungs nor special respiratory organs of any

kind.

Reproduction. - -When one individual animal produces both
sperm cells and egg cells, it is said to be hermaphrodite. This
is true of the earthworm. The egg cell
is always fertilized, however, not by the
sperm cells of the same worm, but by
sperm cells formed by another worm, x
The openings of these ovaries consist of
two pairs of small pores found on the
ventral surface of the fourteenth segment
in most species (see Fig. 77). There
are also two pairs of small receptacles
for temporarily holding \\\Q foreign sperm
cells. One pair of the openings from
these receptacles is found (with diffi-
culty) in the wrinkle behind the ninth
segment (Fig. 77), and the other pair
behind the tenth segment. The sperm-
aries are in front of the ovaries (Fig. 77), but the sperm ducts
are longer than the oviducts, and open behind them on the fifteenth
segment (Figs. 77, 78). The worms exchange sperm cells, but not

IX

FIG. 77. Sperm (sp) and
egg glands (es) of worm.

WORMS

47

egg cells. The reproductive girdle, or clitellum, already spoken of,
forms the case which is to hold the eggs (see Fig. 71). When the
sperm cells have been exchanged, and the ova are ready for fertili-
zation, the worm draws itself backward from the collar-like case or
clitellum so that this slips over the head. As it passes the four-
teenth segment, it collects the ova, and as it passes the ninth and
tenth segments, it collects the sperm cells previously
received from another worm. The elastic, collar-like
clitellum closes at the ends after it has slipped over the
worm's head, forming a capsule. The ova mt fertilized
in this capsule, and some of them hatch into worms in
a few days. These devour the eggs which do not
hatch. The eggs develop into complete but very
small worms before escaping from the capsule.

T.P.

Habits.- The earthworm is omnivorous. It

will eat bits of meat as well as leaves and
other vegetation. It has also the advantage,
when digging its hole, of eating the earth which
must be excavated. Every one has noticed the
fresh " casts " piled up at the holes in the morn-
ing. As the holes are partly filled by rains, the FlG - 7%--

Side view

casts are most abundant after rains. The chief showing setae,
enemies of the earth worm are moles and birds, nephridia

. . pores, and

The worms work at night and retire so early in reproductive
the morning that the very early bird has the P enin gs.
advantage in catching worms. Perhaps the nearest to
an intelligent act the earthworm accomplishes is to con-
ceal the mouth of its hole by plugging it with a pebble or
bit of leaf. Worms hibernate, going below danger of
frost in winter. In dry weather they burrow several feet
deep.

The muscular coat of the body wall is much thicker than
the skin. It consists of two layers : an outer layer of fibers
wJiich run around the body just beneath the skin, and an

48 ANIMAL BIOLOGY

inner, thicker layer of fibers whicJi run lengthwise. The
worm crawls by shortening the longitudinal muscles. As
the bristles (setce) point backward, they prevent the front
part of the body from slipping back, so the hinder part is
drawn forward. Next, the circular muscles contract, and
the bristles preventing the hind part from slipping back,
the fore portion is pushed forward. Is the worm thicker
when the hinder part is being pulled up or when the fore
part is being thrust forward ? Does the earthworm pull or
push itself along, or does it do both ? Occasionally it trav-
els backward, e.g. it sometimes goes backward into its hole.
Then the bristles are directed forward.

The right and left halves of the body are counterparts of
each other, hence the earthworm is bilaterally symmetrical.
The lungs and gills of animals must always be kept moist.
The worm cannot live long in dry air, for respiration in the
skin ceases when it cannot be kept moist, and the worm
smothers. Long immersion in water is injurious to it,
perhaps because there is far less oxygen in water than in
the air.

Darwin wrote a book called "Vegetable Mold and Earth-
worms." He estimated that there were fifty thousand earth-
worms to the acre on farm land in England, and that they
bring up eighteen tons of soil in an acre each year. As
the acids of the food tube act upon the mineral grains that
pass through it, the earthworm renders great aid in form-
ing soil. By burrowing it makes the soil more poroiis and
brings up the subsoil.

Although without eyes, the worm is sensitive to light
falling upon its anterior segments. When the light of a
lantern suddenly strikes it at night, it crawls quickly to its
burrow. Its sense of touch is so keen that it can detect a
light puff of breath. Which of the foods kept in a box of

WORMS

49

damp earth disappeared first? What is indicated as to a
sense of taste ?

Why is the bilateral type of structure better adapted for
development and higher organization than the radiate type
of the starfish ? The earthworm's body is a
double tube ; the hydra's body is a single
tube ; which plan is more advantageous, and
why ? Would any other color do just as well
for an earthworm ? Why, or why not ?

The sandworm (Nereis) lives in the sand of the
seashore, and swims in the sea at night (Fig. 79).
It is more advanced in structure than the earth-
worm, as it has a distinct head (Fig. 80), eyes, two
teeth, two lips, and several pairs of antennae, and
two rows of muscular projections which serve as
feet. It is much used by fishermen for bait. If
more easily obtained, it may be studied instead of
the earthworm.

There are four classes in the branch Vermes :

i) the worms, including sandworms and leeches; 2) the

roundworms, including trichina, hairworms,
and vinegar eels; 3) flativorms, including
tapeworm and liver fluke ; 4) rotifers, which
are microscopic aquatic forms.

The tapeworm is a flatworm which has lost
most of its organs on account of its parasitic
life. Its egg is picked up by an herbivorous
animal when grazing. The embryo under-
goes only partial development in the body
of the herbivorous animal, e.g. an ox. The
next stage will not develop until the beef is eaten by a
carnivorous animal, to whose food canal it attaches itself
and soon develops a long chain of segments called a
"tape." Each segment absorbs fluid food through its

FIG. 79. SAND

WORM x

(Nereis).

FIG. 80. HEAD
OF SANDWORM

(enlarged) .

5O ANIMAL BIOLOGY

body wall. As the segments at the older end mature,
each becomes full of eggs, and the segments become
detached and pass out of the canal, to be dropped and
perhaps picked up by an herbivorous animal and repeat
the life cycle.

The trichina is more dangerous to human life than the
tapeworm. It gets into the food canal in uncooked pork
(bologna sausage, for example), multiplies there, migrates
into the muscles, causing great pain, and encysts there,
remaining until the death of the host It is believed to
get into the bodies of hogs again when they eat rats, which
in turn have obtained the cysts from carcasses.

Summary of the Biological Process. - - An earthworm is
a living machine which does work (digging and crawling;
seizing, swallowing, and digesting food; pumping blood:
growing and reproducing). To do the work it must have
a continual supply of energy. The energy for its work is
set free by the protoplasm (in its microscopic cells) under-
going a destructive chemical change (oxidation). The
waste products from the breaking down of the protoplasm
must be continually removed (excretion). The broken-
down protoplasm must be continually replaced if life is to
continue (the income must exceed the outgo if the animal
is still growing). The microscopic cells construct more
protoplasm out of food and oxygen (assimilation) supplied
them by the processes of nutrition (eating, digesting,
breathing, circulating). This protoplasm in turn oxidizes
and releases more energy to do work, and thus the cycle
of life proceeds.

CHAPTER VII
CRUSTACEANS

CRAWFISH

SUGGESTIONS. In regions where crawfish are not found, a live
crab may be used. Locomotion and behavior may be studied by
providing a tub of water, or better, a large glass jar such as a
broad candy jar. For suggestions on study of internal structure,
see p. 58.

Habitat. - Do you often see crawfish, or crayfish, mov-
ing about, even in water where they are known to be abun-
dant? What does your answer suggest as to the time
when they are probably most active ?

Why do you never see one building its chimney, even
where crawfish holes are abundant ? Is the chimney
always of the same color as the surface soil ? Are the
crawfish holes only of use for protection ? In what kind
of spots are crawfish holes always dug ? Why ? What
becomes of crawfish when the pond or creek dries up ?
How deep are the holes ? How large are the lumps of
mud of which the chimney is built ? How does it get
them out of the hole ? Why is the mud built into a chim-
ney instead of thrown away ? (What would happen to a
well with its mouth no higher than the ground ?) Why
are crawfish scarce in rocky regions, as New England ?

How does the color of the crawfish compare with its
surroundings ? Is its color suited to life in clear or muddy
Vater ? Define protective coloration.

S 1

52 ANIMAL BIOLOGY

Habits. - - Does the crawfish walk better in water or out
of it ? Why ? Does it use the legs with the large claws
to assist in walking? Do the swimmerets (under the ab-
domen) move fast or slow? (Observe it from below in a
large jar of clear water.) What propels it backward ?
Forward ? Does the crawfish move at a more uniform
rate when swimming backward or forward ? Why ? In
which way can it swim more rapidly ? Do the big legs
with claws offer more resistance to the water while it is
swimming backward or forward ? How does it hold the
tail after the stroke, while it is darting backward through
the water ? Hold a crawfish with its tail submerged and
its head up. Can the tail strike the water with much
force ? Allow it to grasp a pencil : can it sustain its own
weight by its grip ?

Feeding. Offer several kinds of food to a crawfish that
has not been alarmed or teased. Does it prefer bread,
meat, or vegetables ? How does it get the food to its mouth ?
Does it eat rapidly or slowly ? Does it tear the food with
the big pincers ? Can it gnaw with the small appendages
near the mouth ?

Breathing. - - Does the crawfish breathe with gills or
lungs ? Place a few drops of ink near the base of the hind
legs of a crawfish resting quietly in shallow water. Where
is the ink drawn in ? Where does it come out ? To ex-
plain the cause and purpose of this motion, place a craw-
fish in a-' large glass jar containing water, and see the
vibratory motion of the parts under the front portion of
the body. There is a gill paddle, or gill bailer, under the
shell on each side of the body that moves at the same rate.

Senses. - - Crawfish are best caught with a piece of meat
or beef's liver tied to a string. Do they always lose hold
as soon as they are lifted above the water ? What do you

CRUSTACEANS

53

conclude as to the alertness of their senses ? Does the cov-
ering of its body suggest the possession of a delicate or dull
sense of touch ?

Of what motions are the eyes capable? Touch one of
the eyes. The result ? Can a crawfish see in all direc-
tions ? To test this, place a crawfish on a table and try
whether you can move to a place where you can see the

FIG. 81. CRAWFISH
(dorsal surface).

FIG. 82.

crawfish without seeing its eyes. What are the advantages
and disadvantages of having the eyes on stalks ?

Touch the body and the several appendages of the
crawfish. Where does it seem most sensitive to touch ?
Which can reach farther, the antennae or the big claws?
Why are short feelers needed as well as long ones ?

Make a loud and sudden noise without jarring the craw-
fish. Is it affected by sound?

External Anatomy (Figs. 81, 82, 83, 84). - - Is the body of
the crawfish rounded out (convex) everywhere, or is any
part of its surface either flat or rounded in (concave) ?

54

ANIMAL BIOLOGY

FIG. 83. LATERAL VIEW OF CRAWFISH.

What color has the crawfish ? Is this color of any use to
the crawfish ?

Make out the two distinct regions or divisions of the body
(Fig. 81). The anterior (front) region is called the head-
chest or cephalothorax, and the posterior (rear) region is

called the tail.
Which region is
larger ? Why ?
Which is flex-
ible ? Why ?

Is the covering
of the body hard
or soft? What
is the advantage of such a covering ? What are its dis-
advantages ? How is the covering modified at the joints
to permit motion ?

Tail. How many joints, or segments, of the tail ? ( Figs.
8 1, 83.) Does the hard covering of each segment slip
under or over the segment behind it when
the tail is straight ? Does this lessen
friction while swimming forward ?

Is there a pair of swimmerets to each
segment of the tail? (Figs. 82, 86.)
Notice that each swimmeret has a main
stalk (protopod), an outer branch (exopod),
and an inner branch (endopod) (Fig. 84).
Are the stalk and the branches each in
one piece or jointed ? The middle part of the tail fin is
called the telson. By finding the position of the vent,
decide whether the food tube goes into the telson
(Fig. 82). Should it be called an abdominal segment.
Are the side pieces of the tail fin attached to the telson
or to the sixth segment ? Do these side pieces correspond

FIG. 84.
FOURTH ABDO-
MINAL SEGMENT
OF CRAWFISH
with swimmeret.

CRUSTACEANS

55

5

to swimmerets ? Do they likewise have the Y-shaped

structure? (Fig. 86.)

If the swimmerets on the first abdominal segment are

large, the specimen is a male. If they are small, it is a

female. Which sex is shown in Fig. 82 ?

Fig. 86 ?

Carapace. The covering of the head

chest (cephalothorax) is called the cara-
pace. Has it free edges? The gills are

on the sides of the body and are covered

by the carapace (Fig. 87). The projection

in front is called the rostrum, meaning beak.

Does the rostrum project beyond the eyes ?

There is a transverse groove across the cara-
pace which may
be said to divide
the head from the
abdomen. Where
does this groove end at the sides ?
Legs. How many legs has the
crawfish ? How many are provided
with large claws ? Small claws ?
Is the outer claw hinged in each
of the large grasping pincers ?
The inner claw ?

Appendages for Taking Food. -
If possible to watch a living craw-
fish eating, notice whether it places

the food directly into the mouth with the large claws. Bend

the large claws under and see if they will reach the mouth.
Attached just in front of the legs the crawfish has three

pairs of finger-like appendages, called foot jaws(maxilli-

peds), with which it passes the food from the large pincers

FIG. 85. i, mandi-
ble ; 2, 3, maxillae;
4, 5, 6, maxillipeds.

L i -V
? -.- -~

FIG. 86. CRAWFISH
(ventral surface).

ANIMAL BIOLOGY

to its mouth (Figs. 85, 86). They are in form and use more
like fingers than feet. In front of the foot jaws are two

pairs of thin jaws
(maxillae) and in
front of the thin
jaws are a pair of
stout jaws (mandi-
bles) (Fig. 85). Do
the jaws move
sidewise or up

FlG. 87. Gill cover removed and gills exposed. and down ? Which

^' gin baner. of the jaws has a

jointed finger (palp) attached to it ? Do all of the appen-
dages for taking food have both exopod and endopod
branches on a basal stalk or protopod ? Which of the
appendages have a scalloped edge? How would you know
from looking at the crawfish that it is not merely a
scavenger ? Why are there no pincers on the hind feet ?

Sense Organs. Find the antennce, or long feelers (Figs.
82, 90). Are the antennae attached above or below the
eyes ? (Fig. 87.)

F" F'

FIG. 88. LENGTHWISE SECTION OF MALE CRAWFISH.

c, heart; A c, artery to head; Aa, artery to abdomen; Km, stomach; D, intestine;
L, liver; T, spermary; Go, opening of sperm duct; G, brain; A 7 ", nerve chain.

Find the pair of antenmdes, or small feelers. Are their
divisions like or unlike each other ? Compare the length
of the antennules and the antennae. Compare the flex-
ibility of the antennae with that of the other appendages,

CR US TA CEANS 5 /

Observe the position of the eyes (Figs. 8 1, 88). How long
are the eyestalks ? Is the stalk flexible or stiff ? Touch the
eye. Where is the joint which enables the stalk to move ?
Is the outer covering of the eye hard or soft ? A mounted
preparation of the transparent covering (cornea) of the
eye, seen with lower power of microscope, reveals that the
cornea is made up of many divisions, called facets. Each
facet is the front of a very small eye, hundreds of which
make up the whole eye, which is therefore called a com-
pound eye. The elongated openings to the ear sacs are
located each on the upper side of the base of a small feeler
just below the eye.

Respiratory System. The respiratory organs are gills
located on each side of the thorax in a space between the
carapace and body (Fig. 87). The gills are white, curved,
and feathery. Is the front gill the largest or the smallest ?
The gills overlap each other ; which is the outermost gill ?
On the second maxilla is a thin, doubly curved plate called
a gill bailer (Fig. 85). The second maxilla is so placed
that the gill bailer comes at the front end of the gill
chamber. The bailer paddles continually, bringing the
water forward out of the gill. The gills are attached
below at the base of the legs. Are the gills thick or thin ?
How far upward do they go ? Does the backward motion
in swimming aid or hinder the passage of the water through
the gills ? Does a crawfish, when at rest on the bottom
of a stream, have its head up or down stream ? Why ?

Openings.- The slitlike vent is on the under side of
the telson (Figs. 82, 88). The viontJi is on the under side
of the thorax behind the mandibles. At the base of the
long antennae are the openings from the green glands, two
glands in the head which serve as kidneys (Fig. 89).
The openings of the reproductive organs are on the third

ANIMAL BIOLOGY

le

FIG. 89. Level length-
wise section showing

k, heart.
d, green gland.
le, liver.
kie, gills.
kh, gill cavity.
ma, stomach.

(After Huxley.)

to the vent,
or small? Straight or
curved? The powerful
flexor muscles of the tail
lie in the abdomen below
the intestines. Compare
the size of these muscles
with the extensor muscle
above the intestine (Fig.
90). Why this difference ?
Does the food tube ex-
tend into the telson? Lo-
cate the vent (Fig. 90) .

pair of legs in the female, and the fifth
pair of legs in the male (Fig. 88). The
eggs are carried on the swimmerets.

Internal Structure. - - SUGGESTIONS. If
studied by dissection, it will be necessary
to have several crawfish for each pupil, one
for gaining general knowledge, and others for
studying the systems in detail. Specimens
should have lain in alcohol for several days.

The Food Tube.- -Is the stomach in the
head portion of the cephalothorax or in the
thoracic portion? (Figs. 88, 89). Is the stomach
large or small? What is its general shape?
Does the gullet lead upward or backward?
Is it long or short? (Fig. 88.) The mid tube,
which is the next portion of the food tube, is
smaller than the stomach. On each side of
it are openings from the bile ducts which
bring the secretion from the digestive gland,
sometimes called the liver. Does this gland
extend the whole length of the thorax? Is
it near the floor or the top of the cavity?
The third and last portion of the food tube
is the intestine. It extends from the thorax
Is it large

FIG. 90. SECTION OF CRAWFISH showing
stomach JT, liver //, and vent a.

CRUSTACEANS

59

The Circulation. The blood is a liquid containing white cor-
puscles. It lacks red corpuscles and is colorless. The heart is in

the upper part of the thorax. It is sur-
rounded by a large, thin bag, and thus it is

in a chamber (called the pericardial sinus].

The blood from the pulmonary veins enters

this sinus before it enters the heart. The

origin of this pericardial sinus by the fusing of

veins is shown in Fig. 1 30. Does one artery,

or do several arteries, leave the heart ? There

is a larger dorsal artery lying on the intestine

and passing back to the telson; there are

three arteries passing forward close to the

dorsal surface (Figs. 89, 91). One large artery

(the sternal) passes directly downward (Figs.

88, 91), and sends a branch forward and

another backward near the ventral surface.

The openings into the heart from the sinus

have valvular lips which prevent a backward

flow of blood into the sinus. Hence, when

the heart contracts, the blood is sent out into the sev-
eral arteries. The arteries take a supply of fresh blood
to the eyes, stomach, muscles, liver, and the various
organs. After it has given oxygen to the several organs
and taken up carbon dioxid, it returns by veins to pass
through the gills on each side, where it gives out the use-
less gas and takes up oxygen from the water. It is then
led upward by veins into the pericardial sinus again.
The central nervous system consists of a double
chain of ganglia (Fig. 92). This main nerve chain
lies along the ventral surface below the food tube
(Fig. 90), except one pair of ganglia which lie
above the esophagus or gullet (Fig. 88), and are
FIG. 92. called the supra-esophageal ganglia, or brain.

Crustacea. The crawfish and its kindred are placed in
the class called Crustacea.

FIG. 91. Showing heart
and main blood vessels.

6o

ANIMAL BIOLOGY

FIG. 93. CRAB FROM
BELOW.

FIG. 94. HERMIT CRAB,
using shell of sea snail
for a house.

Decapods. All Crustacea which have ten feet belong
in the order called decap'oda (ten-footed). This order

includes the crabs, lobsters, shrimp,
etc. The crabs and lobsters are of
considerable importance because of
use as food. Small boys sometimes
catch crawfish, and in some instances
are known to cook and eat them for
amusement,

the only part cooked being the
muscular tail. The crab's tail is
small and flat and held under the
body (Fig. 93).

Since the limy covering to serve
the purpose of protection is not
soft enough to be alive and growing, it is evident that the
Crustacea are hampered in their growth by their crusty

covering. Dur-
ing the first
year the craw-
fish sheds its
covering, or
molts three
times, and
once each year
thereafter. It
grows very fast
for a few days
just after molt-
ing, while the
FIG. 95. DEVELOPMENT OF A CRAB. covering is soft

a, nauplius just after hatching; b,c,d t zoe'a; , megalops; f, adult. and extensible

Question: Which stage is most like a crayfish? Compare .

with metamorphoses of insects. oince 11 IS d.1

CR US TA CEANS 6 1

the mercy of birds, fish, and other enemies while in this
soft and defenseless condition, it stays hidden until the
covering hardens. Hence it cannot eat much, but probably
by the absorption of water the tissues grow ; that is, enlarge.
In the intervening periods, when growth is impossible, it
develops ; that is, the tissues and organs change in structure
and become stronger. " Soft-shelled crab " is a popular dish,
but there is no species by that name, this being only a crab
just after molting which has been found by fishermen in
spite of its hiding.

General Questions. How do crawfish choose their food ?
How long can they live out of water? Why do their gills remain
moist out of water longer than a fish? How do they breathe
out of water ? Are they courageous or cowardly animals ? When
they lose appendages in fighting or molting, these are readily
reproduced, but an organ molts several times in regaining its
size. Have you seen crawfish with one claw smaller than the
other? Explain.

Compare the crawfish and crab (Figs. 81, 93, and 95) in the
following particulars : shape, body, eyes, legs, abdomen, habitat,
movement.

KEY TO THE FOUR CLASSES IN BRANCH ARTHROPODS

1. INSECTS ... 3 body divisions, 6 legs

2. ARACHNIDS . . 2 body divisions, 8 legs

3. MYRIAPODS . . many body divisions, many legs

4. CRUSTACEANS . gill breathers, skeleton (external) limy

By the aid of the key and of figures 96-105, classify the following
Arthropods : tick, thousand-leg centipede, king crab, pill bug, spider,
scorpion, beetle.

62

ANIMAL BIOLOGY

FIG. 96. PILL
BUG.

FIG. 98. SCORPION.

FIG. 101. ONE SEG-
MENT OF CENTIPEDE
with one pair of legs.

FIG. 102.-

ONE SEGMENT

OF THOUSAND

LEGS with two

pairs of legs.

a b

FIG. 99. TICK
before and after

/

feeding.

P

FIG. 103. THOUSAND

LEGS.

FIG. 100.
CENTIPEDE. FIG. 104. A SPIDER. FIG. 105. KING CRAB.

Illustrated Study. CLASSIFICATION OF ARTHROPODS. Key on p. 61.

CHAPTER VIII

INSECTS

THE GRASSHOPPER

SUGGESTIONS. - - Collect grasshoppers, both young and full-
grown, and keep alive in broad bottles or tumblers and feed on
fresh grass or lettuce. When handling a live grasshopper, never
hold it by its legs, as the joints are weak. To keep them for
some time and observe their molts, place sod in the bottom of a
box and cover the box with mosquito netting or wire gauze.

What is the general shape of its body? (Fig. 106.)
Where is the body thickest ? Is it bilaterally symmetri-
cal, that is, are the two sides of the
body alike ? Is the skeleton, or hard
part of the body, internal or external ?
Is the skeleton as stiff and thick
as that of a crawfish ? What is the FIG. 106. A GRASS-
length of your specimen ? Its. color ?

Why does it have this coloration ? In what ways does the
grasshopper resemble the crawfish ? Differ from it ?

The Three Regions of the Body. - The body of the grass-
hopper is divided into three regions, the head, thorax, and
abdomen. Which of these three divisions has no distinct
subdivisions ? The body of the grasshopper, like that of
the earthworm, is made of ringlike segments. Are the
segments most distinct in the head, thorax, or abdomen ?
Which region is longest ? Shortest ? Strongest ? Why ?
Which region bears the chief sense organs ? The ap-
pendages for taking food ? The locomotory appendages ?
Which division of the body is most active in breathing ?

63

6 4

ANIMAL BIOLOGY

The Abdomen. - -About how many segments or rings in
the abdomen ? Do all grasshoppers have the same num-
ber of rings ? (Answer for different species and different
individuals of the same species.) The first segment and
the last two are incomplete rings. Does the flexibility of
the abdomen reside in the rings, or the joints between the
rings ? Is there merely a thin, soft line between the rings,
or is there a fold of the covering ? Does one ring slip into
the ring before it or behind it when the abdomen is bent ?
As the grasshopper breathes, does each ring enlarge
and diminish in size ? Each ring is divided into two parts

by folds. Does the upper half-ring
overlap the lower half-ring, or the
reverse ? With magnifying glass, find
a small slit, called a spiracle, or breath-
ing hole, on each side of each ring just
above the side groove (Fig. 106). A
tube leads from each spiracle. While
the air is being taken in, do the two
portions of the rings move farther
apart ? When they are brought
together again, what must be the
effect ? In pumping the air, the abdomen may be said to
work like a bellows. Bellows usually have folds to allow
motion. Is the comparison correct ?

How many times in a minute does the grasshopper take
in air ? If it is made to hop vigorously around the room
and the breathing is again timed, is there any change ?

Find the ears on the front wall of the first abdominal
ring (Fig. 107). They may be seen by slightly pressing
the abdomen so as to widen the chink between it and
the thorax.. The ears are merely glistening, transparent
membranes, oval in form. A nerve leads from the inner

FIG. 107. A GRASS-
HOPPER DISSECTED.

INSECTS

- -~ f *f r '**- &r j, - -- r:r=5

surface of each membrane. State any advantage or dis-
advantage in having the ears located where they are.

Ovipositor. - - If the specimen is a female, it has an egg-
placer or ovipositor, consisting of four blunt projections at
the end of the abdomen (Fig. 107). If it is a male,
there are two appendages above the end of the abdomen,
and smaller than the parts of the ovipositor. Females
are larger and more abundant than males. In laying
the eggs, the four blunt points are brought tightly to-
gether and then forced into the
ground and opened (Fig. 108). By
repeating this, a pit is made almost
as deep as the abdomen is long.
The eggs are laid in the bottom of
the pit.

Draw a side view of the grass-
hopper.

Thorax. This, the middle por-
tion of the body, consists of three
segments or rings (Fig. 107). Is the division between the
rings most apparent above or below ? Which two of the
three rings are more closely united ?

The front ring of the thorax is called prothorax. Is it
larger above or below ? Does it look more like a collar
or a cape ? (Fig. 106.) A spiracle is found on the second
ring (mesothorax, or middle thorax) just above the second
pair of legs. There is another in the soft skin between
the prothorax and mesothorax just under the large cape or
collar. The last ring of the thorax is called the metathorax
(rear thorax).

How many legs are attached to each ring of the tho-
rax ? Can a grasshopper walk ? Run ? Climb ? Jump ?
Fly? Do any of the legs set forward? (See Fig. 106.)

.

FIG. 108. GRASSHOPPER
LAYING EGGS. (Riley.)

66

ANIMAL BIOLOGY

Outward ? Backward ? Can you give reasons for the posi-
tion of each pair? (Suggestion : What is the use of each
pair ?) If an organ is modified so that it is suited to serve
some particular purpose or function, it is said to be special-
ized. Are any of the legs specialized so that they serve
for a different purpose than the other legs ?

The leg of a grasshopper (as of all insects) is said to
havejfo'^ parts, all the small parts after the first four parts
being counted as one part and called the foot. Are all
the legs similar, that is, do the short and long joints in all
come in the same order ? Numbered in order from the

FIG. 109. How A GRASSHOPPER
WALKS.

FIG. no. How A SPIDER
WALKS.

body, which joint of the leg is the largest,- -the first, sec-
ond, third, or fourth ? Which joint is the shortest ? The
slenderest? Which joint has a number of sharp points or
spines on it ? Find by experiment whether these spines
are of use in walking (Fig. 106). Jumping? Climbing?
In what order are the legs used in walking ? How many
legs support the body at each step ?

All animals that have ears have ways of communicating
by sounds. Why would it be impossible for the grasshop-
per to have a voice, even if it had vocal cords in its
throat? The male grasshoppers of many species make a
chirping, or stridulation, by rubbing the wing against the
leg. Look on the inner side (why not outer side ?) of the

INSECTS

6 7

FIG. in. A, Row OF
SPINES, z, used in
chirping.

B, the same more enlarged.

largest joint of the hind leg for a row of small spines visi-
ble with the aid of a hand lens (Fig. in). The sound is
produced by the outer wings rubbing against the spines.
Have you noticed whether the sound is
produced while the insect is still or in
motion ? Why ? The male grasshop-
pers of some species, instead of having
spines, rub the under side of the front
wing on the upper side of the hind wing.
Wings. - - To what is the first pair
of wings attached ? The second pair ?
Why are the wings not attached to the
prothorax ? Why are the wings attached
so near the dorsal line of the body ? Why are the second
and third rings of the thorax more solidly joined than the
first and second rings ?

Compare the first and second pairs of wings in shape,
size, color, thickness, and use (Fig. 112). How are the

second wings folded so as to go
under the first wings ? About
how many folds in each ?
Draw a hind wing opened out.
Head. What is the shape of
the head viewed from the front, the
side, and above ? ]\Iake sketcJies.
What can you say of a neck ? Is
the head movable in all directions ?
What is the position of the large
eyes ? Like the eyes of the craw-
fish, they are compound, with many facets. But the grass-
hopper has also three simple eyes, situated one in the middle
of the forehead and one just above each antenna. They
are too small to be seen without a hand lens. How does

FIG. ii2, GRASSHOPPER IN
FLIGHT.

68

ANIMAL BIOLOGY

the grasshopper's range of vision compare with that of the
crawfish ?

Are the antennae flexible ? What is their shape ? Posi-
tion ? Are they segmented ? Touch an antenna, a wing,
a leg, and the abdomen in succession. Which seems to be
the most sensitive to touch? The antennae
are for feeling; in some species of insects
they also are organs of hearing and smelling.
The mouth parts of a grasshopper should
be compared with the mouth parts of a bee-
tle shown in Fig. 113, since they correspond
closely. If the grasshopper is fed with a
blade of fresh grass, the function of each organ may be
plainly seen. It is almost impossible to understand these
functions by studying a dead specimen, but a fresh speci-
men is much better than a dry one.

The upper lip, or labrum, is seen in front. Is it tapering
or expanded ? In what direction is it movable? The dark
pointed biting jaws (mandibles) are next. Are they curved

FIG. 113.

FIG. 114. a, FOOD TUBE OF BEETLE.

b, gizzard ; d, intestine; c, biliary vessels. See Fig. 127.

or straight? Sharp or blunt pointed ? Notched or smooth ?
Do they work up and down, or sideways ? The holding jaws
(maxilla), each with two jaw fingers {maxillary palpi), are
behind the chewing jaws. Why? The lower lip (labinm)
has a pair of lip fingers {labial palpi) upon it. The brown

INSECTS

6 9

tongue, usually bathed in saliva, is seen in the lower part of
the mouth. Since the grasshopper has no lips, or any way
of producing suction, it must lap the dew in drinking. Does
it merely break off bits of a grass blade, or does it chew ?

The heart, circulation, nervous system, digestive and res-
piratory organs of the grasshopper agree mainly with the
general description of the organs of insects given in the
next section.

Microscopic Objects. - These may be bought ready
mounted, or may be examined fresh. A portion of the
covering of the large eye may be cut off and the dark layer
on the inside of the covering scraped off to make it trans-
parent. What is the shape of the facets ? Can you make
any estimate of
their number? A
portion of the
transparent hind
wing may be used,
and the "veins'
in it studied. A
thin bit of an abdominal segment containing a spiracle
will show the structure of these important organs.

Growth of the Grasshopper. Some species hibernate in
sheltered places and lay eggs in the spring, but adult species
are scarce at that season. Most species lay the eggs in the
fall ; these withstand the cold and hatch out in the spring.
Those hatched from one set of eggs sometimes stay together
for a few days. They eat voraciously, and as they grow, the
soft skin becomes hardened by the deposit of horny sub-
stance called chitin. This retards further growth until the
insect molts, the skin first splitting above the prothorax. After
hatching, there are five successive periods of growth. At
which molt do the very short wings first appear ? (Fig. 1 1 5.)

FIG. 115. EGG AND MOLTS OF A GRASSHOPPER.

ANIMAL BIOLOGY

After the last molt the animal is complete, and changes
no more in size for the rest of its life. There has been an

attempt among writers to restrict the term
grasshopper to the long-winged, slender
species, and to call the shorter winged,
stouter species locusts according to old
English usage.

Economic Importance of Grasshoppers.
Great injury is often done to vegetation by
grasshoppers ; however, the millions of tiny
but ravenous eaters hatched in early spring
are usually soon thinned out by the birds. The migra-
tory locusts constitute a plague when they appear, and

FIG. 116.
COCKROACH.

FIG. 117. PRAYING MANTIS, or devil's
horse.

FIG. 118. CRICKET.

they have done so since ancient times. The Rocky Moun-
tain locusts flying eastward have darkened the sky, and
where they settled to the earth
ate almost every green thing.
In 1874-5 they produced almost
a famine in Kansas, Nebraska, FlG " "9- -MOLE CRICKET.

and other Western states. The young hatched away

from the mountains were not healthy,
and died prematurely, and their devas-
tations came to an end. Of course the
migrations may occur again. Packard

calculates that the farmers of the

FIG. 120. -FRONT w t j t ^ because of grass-

LEG OF MOLE
CRICKET, x 3. hopper ravages in 1874-5.

INSECTS

The cockroaches (Fig. 116), kindred of the grasshoppers,
are household pests that have migrated almost everywhere
that ships go. The praying mantis (Fig. 117), or devil's
horse, also belongs to this order. It is beneficial, since it
destroys noxious insects. Which of its legs are specialized ?
The walking stick (Fig. 121) and cricket (Fig. 118), like
most members of the order, are vegetarian.

Are grasshoppers more common in fields and meadows,
or in wooded places ? How many different colors have you
seen on grasshoppers ? Which
colors are most common ?

Grasshoppers are very scarce
in Europe as they love dry,
warm countries. Why do lo-
custs migrate ? Give an in-
stance in ancient times.

How long do most grass-
hoppers live ? Does a grass-
hopper spread its wings before
it flies ? Does it jump and fly
together ? Can it select the
place for alighting ?

NOTE TO TEACHER. Field work in
Zoology should be systematic. Every trip FlG - I21 - ~ FouR WALKING STICK
has a definite region and definite line of

study in view, but every animal seen should be noted. The habitat, adapta-
tion by structure and habits to the environment, relations to other animals,
classification of animals seen, should be some of the ideas guiding the study.
The excursions may be divided somewhat as follows, according as opportunities
offer : Upland woods, lowland woods, upland pastures, fields, swamps, a fresh-
water lake, a pond, lower sea beach, higher sea beach, sand hills along shore,
roadside, garden, haunts of birds, insect visits to flowers, ground insects,
insects in logs.

An alphabetical letter file may be used for filing individual field observations.
These should be placed before the class orally or in writing. If accepted as
reliable (repeated and revised if necessary), the observations should be filed

72 ANIMAL BIOLOGY

away and credit given the student on a regular scale. Thus will grading and
marks be placed to encourage intelligent study of nature rather than book
or laboratory cram. One per cent to be added to the final grade may be cred-
ited for every species of pupa, every rare insect (with an observed fact as to its
habits) brought in, every bird migration observed, every instance of protective
coloration, mimicry (p. 146), outwitting of enemy, instance of injurious insects,
and how to combat them, etc. Sharp eyes and clear reasoning will then count
as much on school grades as a memory for words or mechanical following of
laboratory directions. On scale of 100, class work = 50, examination = 25,
field work = 25.

Collecting Insects. In cities and towns insects, varying with
the season, are attracted by electric lights. Beetles and bugs will
be found under the lights, moths on posts near the lights, grass-
hoppers and crickets and other insects in the grass near by. A
lamp placed by a window brings many specimens. In the woods
and in rocky places insects are found under logs and stones, and
under the bark of dead trees. In open places, prairies, meadows,
and old fields with grass and flowers, it will be easy to find grass-
hoppers, butterflies, and some beetles. Ponds and streams are
usually rich in animal forms, such as bugs and beetles, which swim
on or under the surface, and larvse of dragon flies crawling on
the bottom. Dragon flies and other insects that lay eggs on the
water are found flying in the air above. (In the spring, newly
hatched crawfish, tadpoles, and the eggs of frogs and toads should
also be collected, if found.) Moths may be caught at night by
daubing molasses or sirup made from brown sugar upon the
trunks of several trees, and visiting the trees at intervals with a
lantern.

An insect net for catching butterflies and for dredging ponds
may be made by bending a stout wire into a circle one foot in
diameter, leaving enough straight wire to fasten with staples on an
old broomstick. To the frame is fastened a flour sack, or cOne
made of a piece of mosquito netting.

Butterflies and moths should be promptly killed, or they will
beat their wings to pieces. The quickest method is by dropping
several drops of gasoline upon the ventral (under) side of the
thorax and abdomen. (Caution : Gasoline should never be used
near an open fire, or lamp, as explosions and deaths result from

INSECTS

73

the flame being led through the gasoline-saturated air to the vessel
containing it.)

A cigar box and a bottle with a notched cork may be used for
holding specimens. Cigar boxes may be used for holding collec-
tions of dried insects. Cork or ribbed packing paper may be
fixed in the bottom for supporting the insect pins. Moth balls or
tobacco may be placed in each box to keep out the insect pests
which infest collections.

It is pleasant and profitable to take to the fields a small book
like this one, or even Comstock's " Manual of Insects," or Kel-
logg's "American Insects," and study the insects and their habits
where they are found.

Captured insects which, in either the larval or perfect stage,
are injurious to vegetation, should always be killed after studying
their actions and external features, even if the internal structure is
not to be studied. Beneficial insects, such as ladybugs, ichneumon
flies, bees, mantis (devil's horse), dragon flies, etc., should be set
free uninjured.

ANATOMY AND GENERAL CHARACTERISTICS OF THE CLASS

INSECTA

The body of an insect is divided by means of two marked
narrowings into three parts : the head, chest, and ab-
domen.

The head is a freely movable cap-
sule bearing four pairs of append-
ages. Hence it is regarded as
having been formed by the union
of four rings, since the ancestor of
tJie insects is believed to have con-
sisted of similar rings, each ring
bearing a pair of unspecialized legs. FIG. 122. YELLOW FEVER

The typical mouth parts of an
insect (Fig. 123) named in order
from above, are (i) an upper lip (labrum, ol\ (2) a pair

MOSQUITO, showing head,
thorax, abdomen.

74

ANIMAL BIOLOGY

FIG. 123. MOUTH
PARTS OF BEETLE.

of biting jaws (mandibles, ok\ (3) a pair of grasping
jaws (maxillae, A, >), and (4) a lower lip (labium, m, a, b).

The grasping jaws bear two pairs of
jointed jaw fingers (maxillary palpi,
D, C\ and the lower lip bears a pair
of similar lip fingers (labial palpi, d).
The biting jaws move sideways ; they
usually have several pointed notches
which serve as teeth. Why should the
grasping jaws be beneath the chewing
jaws ? Why is it better for the lower
lip to have fingers than the upper lip ?
Why are the fingers (or palpi)
jointed ? (Watch a grasshopper
or beetle eating.) Why does an
insect need grasping jaws ?

The chest, or thorax, consists
of three rings (Fig. 124) called
the front thorax (prothorax),
middle thorax (mesothorax) and
hind thorax (metathorax), or
first, second, and third rings.

The first ring
bears the first

pair of legs, the second ring bears the
second pair of legs and the upper or front
wings, and the third ring bears the third
pair of legs and the under or hind wings.

The six feet of insects are characteristic of
them, since no other adult animals have that
number, the spider having eight, the craw-
fish and crabs having ten, the centipedes still more, while
the birds and beasts have less than six. Hence the insects

FIG. 124. EXTERNAL PARTS
OF A BEETLE.

FIG. 125. LEG
OF INSECT.

INSECTS 75

are sometimes called the Six-Footed class (Hexapodd).
The insects are the only animals that have the body in
three divisions. Man, beasts, and birds have only two
divisions (head and trunk) ; worms are not divided.

Define the class insecta by the two facts characteristic of
them (i.e. possessed by them alone), viz. : Insects are ani-
mals with and . Why would it be ambig-
uous to include " hard outer skeleton " in this definition ? To
include "bilateral symmetry"? "Segmented body"? The
definition of a class must include all the individuals of the class,
and exclude all the animals that do not belong to the class.

The leg of an insect (Fig. 125) has five joints (two -short
joints, two long, and the foot). Named in order from above, they
are (i) the hip (coxa), (2) thigh ring (trochanter), (3) thigh
(femur), (4) the shin (tibia), (5) the foot, which
has five parts. Which of the five joints of a
wasp's leg (Fig. 122) is thickest? Slenderest?
Shortest? One joint (which?) of the foot
(Fig. 122) is about as long as the other four F]G I26- _ FooT OF
joints of the foot combined. Is the relative FLY, with climbing
length of the joints of the leg the same in P ads -
grasshoppers, beetles, etc., as in the wasp (Figs.)? Figure 125 is
a diagram of an insect's leg cut lengthwise. The leg consists of
thick-walled tubes (o, n) with their ends held together by thin,
easy-wrinkling membranes which serve as joints. Thus motion is
provided for at the expense of strength. When handling live
insects they should never be held by the legs, as the legs come
off very easily. Does the joint motion of insects most resemble
the motion of hinge joints or ball-and-socket joints? Answer by
tests of living insects. There are no muscles in the foot of an
insect. The claw is moved by a muscle (m) in the thigh with which
it is connected by the long tendon (2, s, t, v). In which part are
the breathing muscles? As the wings are developed from folds
of the dorsal skin, the wing has two layers, an upper and a lower
layer. These inclose the so-called " nerves " or ribs of the wing,
each of which consists of a blood tube inclosed in an air tube.

ANIMAL BIOLOGY

The abdomen in various species consists of from five
to eleven overlapping rings with their foldlike joints be-
tween them. Does each ring overlap the ring in front
or the one behind it ?

The food tube (Fig. 127) begins at the mouth, which
usually bears salivary glands (4, Fig. 127, which repre-
sents internal organs of the grasshopper). The food tube
expands first into a croplike enlargement ; next to this
is an organ (6, Fig. 127), which resembles the gizzard

FIG. 127. VISCERA OF
GRASSHOPPER. Key
in text. Compare with
Fig. 114.

FIG. 128. AIR TUBES OF INSECT.

in birds, as its inner wall is furnished with chitinous teeth
(b, Fig. 1 14). These reduce the food fragments that were
imperfectly broken up by the biting jaws before swallow-
ing. Glands comparable to the liver of higher animals
open into the food tube where the stomach joins the small
intestine. At the junction of the small and large intestine
(9) are a number of fine tubes (8) which correspond to
kidneys and empty their secretion into the large intestine.
The breathing organs of the insects are peculiar to
them (see Fig. 128). They consist of tubes which are

INSECTS

77

^K^,
IflKa

FIG. 129.

INSECT'S

HEART

(plan).

kept open by having in their walls continuous spirals of
horny material called chitin. Most noticeable are the
two large membranous tubes filled with air and
situated on each side of the body. Do these
tubes extend through the thorax? (Fig. 128.) The
air reaches these two main tubes by a number
of pairs of short windpipes, or tracheas, which
begin at openings (spiracles). In which division
are the spiracles most numerous? (Fig. 128.)

Which division is
without spiracles ?
Could an insect
be drowned, i.e.
smothered, by holding its
body under water ? Could
it be drowned by immersing
all of it but its head ? The
motion of the air through
the breathing tubes is caused by a bellowslike motion of the
abdomen. This is readily observed in grasshoppers, beetles,
and wasps. As each ring slips into the ring in front of it,
the abdomen is shortened, and the impure air, laden with
carbon dioxid, is forced out. As the rings slip out, the
abdomen is extended
and the fresh air comes
in, bringing oxygen.

The Circulation.
Near the dorsal surface
of the abdomen (Fig.
131) extends the long, slender heart (Fig. 129). The heart
has divisions separated by valvelike partitions. The blood
comes into each of the heart compartments through a pair
of openings. The heart contracts from the rear toward

FIG. 130. DIAGRAMS OF EVOLUTION
OF PERICARDIAL SAC around in-
sect's heart from a number of veins
(Lankester).

FIG. 131. POSITION OF INSECT'S HEART,
food tube, and nerve chain.

ANIMAL BIOLOGY

the front, driving the blood forward. The blood contains
bodies corresponding to the white corpuscles of human
blood, but lacks the red corpuscles and the red color. The
blood is sent even to the wings. The veins in the wings
consist of horny tubes inclosing air tubes surrounded
by blood spaces, and the purification of the blood is

taking place throughout the course
of the circulation. Hence the im-
perfect circulation is no disadvan-
tage. The perfect provision for
supplying oxygen explains the
remarkable activity of which in-
sects are capable and their great
strength, which, considering their
size, is unequaled by any other
animals.

The Nervous System. The
heart in backboned animals, e.g.
man, is ventral and the chief nerve trunk is dorsal. As
already stated, the heart of an insect is dorsal ; its chief
nerve chain, consisting of a double row of ganglia, is near
the ventral surface (Fig. 131). All the ganglia are below
the food tube except the first pair in the head, which are
above the gullet. This pair may be said to
correspond somewhat to the brain of backboned
animals ; the nerves from the eyes and feelers
lead to it. With social insects, as bees and
ants, it is large and complex (Fig. 132). In a
typical insect they are the largest ganglia.

The Senses. The sense of smell of most in-
sects is believed to be located in the feelers.
The organ of hearing is variously located in different in-
sects. Where is it in the grasshopper ? The organs of

FIG. 132. NERVOUS SYS-
TEM OF BEE.

FIG. 133.

FEELER
of a beetle.

INSECTS

79

FIG. 134. Diagram
of simple eye of
insect.

L, lens; N", optic
nerve.

sight are highly developed, and consist of two compound

eyes on the side of the head and three simple eyes on the

top or front of the head between the com-
pound eyes. The simple eye has nerve

cells, pigments, and a lens resembling

the lens in the eyes of vertebrates (Fig.

134). The compound eye (Fig. 135) has

thousands of facets, usually hexagonal,

on its surface, the facets being the outer

ends of cones which have their inner

ends directed toward the center of the

eye. It is probable that the large, or

compound, eyes of insects only serve to distinguish bright

objects from dark objects. The simple eyes afford dis-
tinct images of objects within a
few inches of the eye. In gen-
eral, the sight of insects, contrary
to what its complex sight organs
would lead us to expect, is not at
all keen. Yet an insect can fly
through a forest without striking
a twig or branch. Is it better for
the eyes that are immovable in
the head to be large or small ?
Which has comparatively larger

FIG. 135. COMPOUND EYE
OF INSECT.

i, hexagonal facets of crystalline
cones. 6, blood vessel in optic nerve.

Inherited Habit, or Instinct. - - Insects and other ani-
mals inherit from their parents their particular form of
body and of organs which perform the different functions.
For example, they inherit a nervous system with a struc-
ture similar to that of their parents, and hence with a ten-
dency to repeat similar impulses and acts. Repeated acts
constitute a habit, and an inherited habit is called an in-

8O ANIMAL BIOLOGY

stinct. Moths, for example, are used to finding nectar in
the night-blooming flowers, most of which are white. The
habit of going to white flowers is transmitted in the struc-
ture of the nervous system ; so we say that moths have
an instinct to go to white objects ; it is sometimes more
obscurely expressed by saying they are attracted or drawn
thereby.

Instincts are not Infallible. They are trustworthy in
only one narrow set of conditions. Now that man makes
many fires and lights at night, the instinct just mentioned
often causes the death of the moth. The instinct to
provide for offspring is necessary to the perpetuation of
all but the simplest animals. The dirt dauber, or mud
wasp, because of inherited habit, or instinct, makes the
cell of the right size, lays the egg, and provides food for
offspring that the mother will never see. It seals stung
and semiparalyzed spiders in the cell with the egg. If
you try the experiment of removing the food before the
cell is closed, the insect will bring more spiders ; if they
are removed again, a third supply will be brought; but if
taken out the third time, the mud wasp will usually close
the cell without food, and when the egg hatches the grub
will starve.

The Development of Insects. The growth and molting
of the grasshopper from egg to adult has been studied.
All insects do not develop exactly by this plan. Some
hatch from the egg in a condition markedly different from
the adult. The butterfly's egg produces a wormlike cater-
pillar which has no resemblance to the butterfly. After
it grows it forms an inclosing case in which it spends a
quiet period of development and comes out a butterfly.
This change from caterpillar to butterfly is called the
metamorphosis. The life of an insect is divided into four

INSECTS

81

FlG. 136. Measuring worm,
the larva of a moth.

stages : (i) egg, (2) larva, (3) pupa, and (4) imago,, or per-
fect insect (Figs. 136, 137, 138).

The egg stage is one of development, no nourishment
being absorbed. The larval stage is one of voracious feed-
ing and rapid growth. In the pupa
stage no food is taken and there is
no growth in size, but rapid devel-
opment takes place. In the per-
fect stage, food is eaten, but no
growth in size takes place. In this
stage the eggs are. produced. When

there is very little resemblance between
the larva and imago, and no pupal stage,
the metamorphosis, or change, is said to be
complete. When, as with the grasshopper,
no very marked change takes place between
the larva and imago, there being no pupal
stage, the metamorphosis is said to be in-
of a mosquito. complete. By studying the illustrations and
specimens, and by thinking of your past .observations of
insects, determine which of the insects in the following list
have a complete metamorphosis : beetle, house fly, grass-
hopper, butterfly, cricket, wasp.

FIG. 137. Pupa

FIG. 138. THE FOUR STAGES OF A BOTFLY, all enlarged.

, egg on hair of horse (bitten off and swallowed) ; b, larva; c, larva with hooks for holding
to lining of stomach; d, pupal stage, passed in the earth; e, adult horse fly.

82 ANIMAL BIOLOGY

RECOGNITION-CHARACTERS FOR THE PRINCIPAL
ORDERS OF ADULT WINGED INSECTS

(All are wingless when young, and wingless adult forms occur
in all the orders : order APTERA lacks wing-bearing thoracic
structures.)

A single pair of wings is characteristic of the order DIPTERA.

A jointed beak, that is sheath-like, inclosing the other mouth
parts, is characteristic of the order HEMIPTERA.

A coiled sucking proboscis and a wing covering of dust-like
microscopic scales are characteristic of the order LEPIDOPTERA.

Horny sheath-like fore wings, covering the hind wings and
meeting in a straight line down the middle of the back, will dis-
tinguish the order COLEOPTERA.

Hind wings folded like a fan beneath the thickened and over-
lapping fore wings, will distinguish most members of the order
ORTHOPTERA.

The possession of a sting (in females) and of two pairs of thin
membranous wings the small hind wing hooked to the rear mar-
gin of the fore wing will distinguish the common HYMENOPTERA.

Besides these, there remain a number of groups most of which
have in the past been included under the order NEUROPTERA,
among which the Mayflies will be readily recognized by the lack
of mouth parts and by the possession of two or three long tails ;
the dragon flies by the two pairs of large wings, enormous eyes, and
minute bristle-like antennae ; the scorpion flies, by the possession
of a rigid beak, with the mouth parts at its tip ; the caddis flies,
by their hairy wings and lack of jaws ; the lace wings, by the
exquisite regularity of the series of cross veins about the margin
of their wings, etc.

INSECTS

FIG. 139. MAY FLY. What order (see table)?

Exercise in the Use of the Table or Key. -

Write the name of the order after each of the fol-
lowing names of insects : -

Wasp (Fig. 122)
Weevil (Fig. 163)
Squash bug ( Fig. 184)
Ant lion (Fig. 170)
Dragonfly (Fig. 177)

House fly (Fig. 172)
Flea (Fig. 173)
Silver scale or earwig

(Fig. 140)
Codling moth (Fig. 141)

FIG. 140. SILVER
SCALE. (Order?)

Ichneumon fly (Fig. 159) Botfly (Fig. 138)

Moths and Butterflies. - - Order_ ? Why. - (p. 82) ?

The presence of scales on the wings is a never-failing
test of a moth or butterfly. The wings do not fold at all.
They are so large and the legs so weak and delicate
that the butterfly keeps its balance with difficulty when
walking in the wind.

The maxillae are developed to form the long sucking
proboscis. How do they fit together to form a tube ?
(See Fig. 147.) The proboscis varies from a fraction of an
inch in the "miller" to five inches in some tropical moths,
which use it to extract nectar from long tubular flowers.
When not in use, it is held coiled like a watch spring under
the head (Fig. 148). The upper lip (labrum), under lip
(labium), and lip fingers (labial palpi) are very small, and
the mandibles small or wanting (Fig. 146).

The metamorphosis is complete, the contrast between
the caterpillar or larva of the moth and butterfly and the
adult form being very great. The caterpillar has the
three pairs of jointed legs typical of insects; these are

84 ANIMAL BIOLOGY

found near the head (Fig. 141). It has also from three
to five pairs of fleshy unjointed proplegs, one pair of
which is always on the last segment. How many pairs
of proplegs has the silkworm caterpillar? (Fig. 143.)
The measuring worm, or looper ? (Fig. 136.) The pupa
has a thin shell. Can you see external signs of the
antennae, wings, and legs in this stage ? (Fig. 143.) The
pupa is concealed by protective coloration, and is some-
times inclosed in a silken cocoon which was spun by the
caterpillar before the last molt. Hairy caterpillars are
uncomfortable for birds to eat. The naked and brightly
marked ones (examples of warning coloration) often con-
tain an acrid and distasteful fluid. The injuries from
lepidoptera are done in the caterpillar stage. The codling
moth (Fig. 141) destroys apples to the estimated value of
$6,000,000 annually. The clothes moth (Fig. 171) is a
household pest. The tent caterpillar denudes trees of their
leaves. The only useful caterpillar is the silkworm (Fig.
143). In Italy and Japan many of the country dwellings
have silk rooms where thousands of these caterpillars are
fed and tended by women and children. Why is the cab-
bage butterfly so called ? Why can it not eat cabbage ?
Why does sealing clothes in a paper bag prevent the
ravages of the clothes moth ?

Flight of Lepidoptera. - - Which appears to use more ex-
ertion to keep afloat, a bird or a butterfly ? Explain why.
Of all flying insects which would more probably be found
highest up mountains? How does the butterfly suddenly
change direction of flight ? Does it usually fly in a straight
or zigzag course ? Advantage of this ? Bright colors are
protective, as lepidoptera are in greatest danger when at
rest on flowers. Are the brightest colors on upper or
under side of wings of butterfly ? Why ? (Think of the

INSECTS

colors in a flower.) Why is it better for moths to hold
their wings flat out when at rest ? Where are moths dur-
ing the day? How can you test whether the color of the
wings is given by the scales ?

State how moths and butterflies differ in respect to :
body, wings, feelers, habits.

Insects and Flowers.- -Perhaps we are indebted to in-
sects for the bright colors and sweet honey of flowers.
Flowers need insects to carry their pollen to other flowers,
as cross-fertilization produces the best seeds. The insects
need the nectar of the flowers for food, and the bright
colors and sweet odors are the advertisements of the
flowers to attract insects. Flowers of brightest hues are
the ones that receive the visits of insects. Moths, butter-
flies, and bees carry most pollen (see Plant Biology,
Chap. VI).

Comparative Study. - - Make a table like this, occupying entire page
of notebook, leaving no margins, and fill in accurately :

GRASS-
HOPPER

BUTTER-
FLY

FLY

PP- 9 2 > 93

DRAGON
FLY, p. 93

BEETLE
pp. 90, QI

BEE
pp. 88, 89

Number and kind
of wings

Description of legs

Antennae (length,
shape, joints)

Biting or sucking
mouth parts

Complete or incom-
plete metamor-
phosis

Illustrated Studies

FIG. 142. CABBAGE BUTTERFLY, male
and female, larva and pupa.

FIG. 141. CODLING MOTH, from egg to
adult. (See Farmers' Bulletin, p. 95.)

FIG. 143. LIFE HISTORY OF SILKWORM.

FlG. 144. SCALES FROM

BUTTERFLIES' WINGS, as
seen under microscope.

Illustrated Studies

To THE TEACHER: These illustrated studies require
slower and more careful study than the text. One, or at
most two, studies will suffice for a lesson. The questions can
be answered by studying the figures. Weak observers will
often fail and they should not be told, but should try again
until they succeed.

FIGS. 141-148. Illustrated Study of Lepidoptera.
Study the stages in the development of codling moth, silk-
worm moth, and cabbage butterfly.

Where does each lay its eggs ? What does the larva of
each feed upon ? Describe the pupa of each. Describe
the adult forms. Find the spiracles and prolegs on the
silkworm. Compare antenna of moth and butterfly.
Which has larger body compared to size of wings ?

Describe the scales from a butterfly's wings as seen under
microscope (144). How are the scales arranged on moth's
wing (145) ? By what part is scale attached to wing ? Do
the scales overlap ?

Study butterfly's head and proboscis (Figs. 146-148).
What shape is compound eye ? Are the antennae jointed ?
Is the proboscis jointed ? Why not call it a tongue ?
(See text.)

Which mouth parts have almost disappeared ? What is
the shape of cut ends of halves of proboscis ? How are
the halves joined to form a tube ?

If you saw a butterfly on a flower, for what purpose
would you think it was there? What, if you saw it on a
leaf? How many spots on fore wing of female cabbage
butterfly? (Fig. 124, above.)

Does the silkworm chrysalis fill its cocoon ? Eggs may
be obtained from U. S. Dept. of Agriculture.

i-IG. 145. SCALES

ON MOTH'S WING.

FIG. 146. HEAD
OF BUTTERFLY.

FIG. 148. HEAD
OF BUTTERFLY
(side view).

FIG. 147. SECTION
OF PROBOSCIS of
butterfly showing
lapping joint and
dovetail joint.

88

Illustrated Studies

FIG. 153.

FIG. 152.

FIG. 156.

FIG. 157.

v

FIG. 158. Anatomy of bee.

FIGS. 149-161. Illustrated
Study of Bees and their Kin-
dred. Head of worker (Fig.
149) : o, upper lip ; ok, chew-
ing jaws; uk, grasping jaws;
kt, jaw finger : It, lip finger ;
z, tongue.

How do heads of drone
(150) and queen (151) differ
as to mouth, size of the two

compound eyes, size and position of the three simple eyes ? Is the head of a
worker more like head of drone or head of queen ? Judging by the head, which
is the queen, drone, and worker in Figs. 154-156 ? Which of the three is largest?
Smallest ? Broadest ?

Figure 152 shows hind leg of worker. What surrounds the hollow, us, which
serves as pollen basket ? The point, fh, is a tool for removing wax which is
secreted (c, Fig. 157) between rings on abdomen. In Fig. 158, find relative
positions of heart, v, food tube, and nerve chain. Is crop, /, in thorax or abdo-
men ? In this nectar is changed to honey, that it rnay not spoil. Compare
nerve chain in Fig. 132.

Illustrated Studies

FIG. 159.
Ichneumon fly.

Compare the cells of
bumble bee (Fig. 153) with
those of hive bee. They
differ not only in shape but
in material, being made of
web instead of wax, and
they usually contain larvae
instead of honey. Only a
few of the queens among
bumble bees and wasps
survive the winter. How
do ants and honey bees
provide for the workers
also to survive the win-
ter ? Name all the social
insects that you can think of. Do
they all belong to the same order ?

The ichneumon fly shown enlarged in
Fig. 159 lays its eggs under a caterpillar's
skin. What becomes of the eggs ? The
true size of the insect is shown by the
cross lines at a. The eggs are almost
microscopic in size. The pupae shown
(true size) on caterpillar are sometimes
mistaken for eggs. The same mistake is
made about the pupa cases of ants.
Ichneumon flies also use tree-borers as
" hosts " for their eggs and larva. Is
this insect a friend of man ?

The digging wasp (Figs. 160 and 161)
supplies its larva with caterpillars and
closes the hole, sometimes using a stone
as pounding tool. Among the few
other uses of tools among lower
animals are the elephant's use
of a branch for a fly brush, and
the ape's use of a walking stick.
This wasp digs with fore feet
like a dog and kicks the dirt
out of the way with its hind
feet.

Are the wings of bees and
wasps more closely or less
closely veined than the wings
of dragon flies ? (Fig. 177.)
For an interesting account
of the order " Joined-wings "
(bees and their kindred) see
Comstock's " Ways of the Six-
footed," Ginn & Co.

FIG. 161. Wasp using pebble.

From Peckham's " Solitary Wasps,"
Houghton, Mifflin & Co.

Illustrated Studies

niustrated

Study of
Beetles.

FIG. 162. Diving beetle (Dystic-us), with larva, a. FIG. 163. Weevil.

FIG. 165.

FIG. 166. Click beetle

FIG. 167. MAY BEETLE

FlG. 169. Colorado beetle (potato bug).

Illustrated Studies

Illustrated Study of Beetles (Figs. 162-169) . Write the life history of the
Colorado beetle, or potato bug (Fig. 169), stating where the eggs are laid and describ-
ing the form and activities of each stage (the pupal strige, b, is passed in the ground).

Do the same for the May beetle (Figs. 167-168). (It is a larva the white
g ru b for three years; hogs root them up.) Beetles, like moths, maybe trapped
with a lantern set above a tub of water.

Where does a Scarab (or sacred beetle of the Egyptians, also called tumble
bug (Fig. 164), lay its eggs (Fig. 165)? Why?

How does the click beetle^r jack snapper (Fig. 166), throw itself into the air?
For what purpose ?

The large proboscis of the -weevil (Fig. 163) is used for piercing a hole in which
an egg is laid in grain of corn, boll of cotton, acorn, chestnut, plum, etc.

How are the legs and body of the diving beetle suited for swimming (Fig. 162) ?
Describe its larva.

What is the shape of the lady bug (Fig. 97) ? It feeds upon plant lice (Fig. 185) .
Is any beetle of benefit to man ?

' r; i i

fjlp%p" f/

^''^iiij.i ,\f

^^^S^&

FlG. 170. Life history of ant lion.

Illustrated Study of Ant Lion, or Doodle Bug (Fig. 170). Find the pitfall
(what shape? ) ; the larva (describe it) ; the pupa case (ball covered with web and
sand) ; the imago. Compare imago with dragon fly (Fig. 177).

How does ant lion prevent ant from climbing out of pitfall (see Fig. 170) ?
What is on edge of -nearest pitfall ? Explain.

Ant lions may be kept in a box half filled with sand and fed on ants. How is
the pitfall dug? \Vhat part of ant is eaten ? How is unused food removed?

How long is it in the larval state ? Pupal state ? Keep net over box to pre-
vent adult from flying away when it emerges.

Illustrated Studies

FIG. 171.

A

FIG. 173. Metamorphosis of flea.

**-- o

FlG. 172. Metamor-
phosis of house fly
(enlarged).

FIG. 174. Louse and
its eggs attached to a
hair. Natural size
and magnified.

^^^;.j'Vv/!4 : t

Si "S; \.'\- ,"X 'JKV '-. -''!/ uJ*' v.:1-iir3iEM3^fcr

^^^*lP'r" ; ^s^%^ s'feQ^|; : Sp^^^B

FIG. 175. Bed bug. x 5.

H^r-"^ ''^'^B^fc^SSS't^-SJIs&^j^BJfflE^^ ^-a^--
FlG. 176. Life history of mosquito.

Illustrated Studies

93

Illustrated Study of Insect Pests (Figs. 171-176). Why does the clothes
moth (171) lay its eggs upon woolen clothing ? How does the larva conceal itself?
The larva can cut through paper and cotton, yet sealing clothes in bags of paper
or cotton protects them. Explain.

The house fly eats liquid sweets. It lays its eggs in horse dung. Describe its
larval and pupal forms. Banishing horses from city would have what beneficial
effect ?

Describe the louse and its eggs, which are shown attached to a hair, natural size
and enlarged.

Describe the bed bug. Benzine poured in cracks kills bed bugs. Do bed
bugs bite or suck ? Why are they wingless ?

Describe the larva, f, pupa, g, and the adult flea, all shown enlarged. Its
mandibles, b, b, are used for piercing. To kill fleas lather dog or cat completely
and let lather remain on five minutes before washing. Eggs are laid and first
stages passed in the ground.

How does the mosquito lay its eggs in the water without drowning (176) ? Why
are the eggs always laid in still water ? Which part of the larva (wiggletail) is held
to the surface in breathing ? What part of the pupa (called tumbler, or bull head)
is held to the surface in breathing ? Give differences in larva and pupa. Where
does pupa change to perfect insect ? Describe mouth parts of male mosquito (at
left) and female (at right). Only female mosquitoes suck blood. Males suck
juice of plants. Malarial mosquito alights with hind end of body raised at an
angle. For figure see Human Biology, Chap. X. Why does killing fish and frogs
increase mosquitoes? i oz. of kerosene for 15 ft. of surface of water, renewed
monthly, prevents mosquitoes.

What is the use to the squash bug (Fig. 184) of having so bad an odor ?

\ 2 5 <k 5

FIG. 177. Illustrated Study of Dragon Fly. 3 shows dragon fly laying its
eggs in water while poised on wing. Describe the larval form (water tiger). The
extensible tongs are the maxillae enlarged. The pupa (i) is active and lives in
water. Where does transformation to adult take place (5) ? Why are eyes of
adult large ? its legs small ? Compare front and hind wings.

Do the eyes touch each other ? W T hy is a long abdomen useful in flight ?
Why would long feelers be useless ? What is the time of greatest danger in the
development of the dragon fly ? What other appropriate name has this insect ?
Why should we never kill a dragon fly ?

94

Illustrated Studies

f,y.,-\ KCV

I .;$>'

FIG. 179. Trap-door
spider.

FIG. 178. The tarantula.

FIG. 180.

FIG. 181. Anatomy of spider.

FIG. 182. Laying egg.

FlG. 183. Foot of spider.

Illustrated Study of Spiders (Figs. 178-183). The tarantula, like most spi-
ders, has eight simple eyes (none compound). Find them (Fig. 178). How do
spiders and insects differ in body ? Number of legs ? Which have more joints to
legs? Does trap-door spider hold the door closed (Fig. 179)? How many pairs
of spinnerets for spinning web has a spider (Spw, 180) ? Foot of spider has how
many claws ? How many combs on claws for holding web ? Spiders spin a
cocoon for holding eggs. From what part of abdomen are eggs laid (E, 182;
2, 181) ? Find spider's air sacs, lu, Fig. 181 ; spinning organs, sp ; fang, //"; poison
gland, g\ palpi, kt\ eyes, au ; nerve ganglia, og, ug\ sucking tube, sr ; stomach, rf;
intestine, ma ; liver, le ; heart, h, (black) ; vent, a. Give two reasons why a spider
is not an insect. How does it place its feet at each step (Fig. no) ? (Does the
size of its nerve ganglia indicate great or little intelligence ? Why do you think
first part of body corresponds to both head and thorax of insects ?

INSECTS

95

FIG. 184. Squash bug, or
stink bug.

The following Farmer's Bulletins are available for free
distribution to those interested, by the U. S. Department
of Agriculture, Washington, D.C. :

Farmer's Bulletin No. 47, Insects affecting the Cotton Plant;
No. 59, Bee Keeping; No. 70, The Principal Insect Enemies of
the Grape ; No. 80, The Peach Twig
Borer ; No. 99, Three Insect Enemies
of Shade Trees; No. 120, The Principal
Insects affecting the Tobacco Plant ;
No. 127, Important Insecticides; No.
132, The Principal Insect Enemies of
Growing Wheat; No. 145, Carbon Bi-
sulphid as an Insecticide ; No. 146,
Insecticides and Fungicides; No. 152,
revised, Mange in Cattle; No. 153, Orchard Enemies in the
Pacific Northwest; No. 155, How Insects affect Health in Rural
Districts; No. 159, Scab in Sheep; No. 165, Silkworm Culture;
No. 171, The Control of the Codling Moth; No. 172, Scale In-
sects and Mites on Citrus Trees; No. 196, Usefulness of the
Toad ; No. 209, Controlling the Boll Weevil in Cotton Seed and
at Ginneries ; No. 211, The Use of Paris Green in controlling the

/ / Cotton Boll Weevil; No. 212,

' The Cotton Bollworm ; No.

216, The Control of the Boll
Weevil; No. 223, Miscellane-
ous Cotton Insects in Texas ;
No. 247, The Control of the
Codling Moth and Apple Scab.
The following bulletins of
the Bureau of Entomology may
be obtained from the same source at the prices affixed : Bulletin
No. 25 (old series), Destructive Locusts, i5c. ; No. i (new series),
The Honey Bee, 150. ; No. 3, The San Jos Scale, loc. ; No. 4,
The Principal Household Insects of the U. S., ice. ; No. n, The
Gypsy Moth in America, 5c. ; No. 14, The Periodical Cicada,
i5c. No. 15, The Chinch Bug, ice. ; No. 16, The Hessian Fly,
ioc.; Nos. 19, 23, and 33, Insects Injurious to Vegetables, loc.

FIG. 185. Female plant louse, with and
without wings (enlarged).

9 6

ANIMAL BIOLOGY

each; No. 25, Notes on Mosquitoes of the U. S., loc. ; No. 42
Some Insects attacking the Stems of Growing Wheat, Rye, Barley,

and Oats, 5c. ; No. 50, The
Cotton Bolhvorm, 25C. ; No. 51,
The Mexican Boll Weevil, 25c.
Bureau of Plant .Industry
FIG. 186. - Gall fly (enlarged) and oak Bulletin No. 88, Weevil-resisting

gall with larva, and one from which Adaptations of the Cotton Plant,

a developed insect has escaped. JOC< ^his giyes an i nstruc tive

account of the struggle of a plant for existence against an insect
enemy.

FIG. 187. Weevil on a Corylus or filbert.

w^ ^eslrisgsisSr- 1 . v- ' . t

Pearl divers.

CHAPTER IX

MOLLUSKS

THE FRESH-WATER MUSSEL

SUGGESTIONS. The mussel is usually easy to procure from
streams and lakes by raking or dredging. In cities the hard-
shelled clam, or quahog, is for sale at the markets, and the follow-
ing descriptions apply to the anodon, unio, or quahog, with
slight changes in regard to the siphons. Mussels can be kept
alive for a long time in a. tub with sand in the bottom. Pairs of
shells should be at hand for study.

External Features.- The shell is an elongated oval,
broader and blunter at one end (Fig. 188). Why does
the animal close its shell ? Does it open the shell ?
Why ? Does it thrust the foot forward and pull up to it,
or thrust the foot back and push ? (Mussels and clams
have no bones.) Does it go with the blunt or the more
tapering end of the shell forward ? (Fig. 188.) Can a
mussel swim ? Why, or why not ?

97

H

9 8

ANIMAL BIOLOGY

'

FIG. 188.

ANODON, or fresh-water
mussel.

Lay the shells, fitted together, in your hand with the hinge
side away from yon and tJie blunt end to tJie /<*/?( Fig. 1 88).

Is the right or the left shell
uppermost ? Which is the
top, or dorsal, side ? Which
is the front, or anterior,
end ? Is the straight edge
at the top or the bottom ?
Our word " valve " is derived
from a word meaning shell,
because the Romans used
shells for valves in pumps. Is the mussel a univalve or a
bivalve ? Which kind is the oyster ? The snail ?

Does the mussel have bilateral symmetry ? Can you
find a horny coveiing, or epidermis, over the limy shell
of a fresh specimen ? Why is it necessary ? Does water
dissolve lime ? Horn ? Find a bare spot. Does any of
the shell appear to be missing there ?

The bare projection on each shell is called the umbo.
Is the umbo near the ventral or the dorsal line ? The
posterior or anterior end ? Is
the surface of the umbones
worn ? Do the umbones rub
against the sand as the mussel
plows its way along ? How are
the shells held together ? Where
is the ligament attached ? (Fig.
189.) Is it opposite the um-
bones or more to the front or
rear? (Fig. 189.) Is the liga-
ment of the same material as the shell? Is the ligament
in a compressed condition when the shell is open or when
it is closed ? (Fig. 189.) When is the muscle relaxed ?

FIG. 189. DIAGRAM OF SHELL
open and closed, showing mus-
cle, m, and ligament, b.

MOLLUSKS

99

ex si..

FIG. 190. MUSSEL crawl-
ing in sand.

Notice the lines on the outside of the shell (Figs. 188
and 190). What point do they surround? They are lines
of growth. Was each line once the
margin of the shell? If the shell
should increase in size, what would
the present margin become ? (Fig.
191.) Does growth take place on
the margin only? Did the shell
grow thicker as it grew larger?
Where is it thinnest ?

Draw the outside of the shell from
the side. Draw a dorsal view. By the drawings write the
names of the margins of the shell (p. 98) and of other parts
learned, using lines to indicate the location of the parts.

Study the surface of the shell inside and out. The
inside is called mother-of-pearl. Is it of lime ? Is the
deeper layer of the shell of lime ? (When weak hydro-
chloric acid or strong vinegar is dropped on limy substances,
a gas, carbon dioxid, bubbles up.) Compare the thickness
of the epidermal layer, the middle clialky layer, and the
inner, pearly layer.

Anatomy of the Mussel. - - What parts protrude at any
time beyond the edge of the shell ? (Fig. 190.) The shell

is secreted by two folds of the outer
layer of the soft body of the mus-
sel. These large, flaplike folds hang
down on each side, and are called
the mantle. The two great flaps
of the mantle hang down lower than
the rest of the body and line the
shell which it secretes (Fig. 192).
The epidermis of the mantle secretes the shell just as the
epidermis of the crawfish secretes its crust. Can you find

X.JE.

FIG. 191. - DIAGRAM.
Change of points of attach-
ment of muscles as mussel
enlarges. (Morgan.)

IOO

ANIMAL BIOLOGY

SHELL

FIG. 192. CROSS SECTION
OF MUSSEL. (Diagram,
after Parker.)

the pallial line, or the line to which the mantle extended
on each shell when the animal was alive ? A free portion
of the mantle extended like a fringe below the pallial line.

The shells were held together by
two large adductor muscles. The
anterior adductor (Fig. 193) is near
the front end, above the foot. The
posterior adductor is toward the rear
end, but not so near the end as the
anterior. Can you find both muscle
scars in the shells ? Are they nearer
the ventral or dorsal surface ? The
points of attachment traveled down-
ward and farther apart as the ani-
mal grew (see Fig. 191). Higher
than the larger scars are small scars, or impressions, where
the protractor and retractor muscles that extend and draw
in the foot were attached. H

The muscular foot extends downward in the middle, half-
way between the shells (Fig. 193). On each side of the
foot and behind
it hang down
the two pairs of
gills, the outer
pair and the in-
ner pair (Fig.
192). They may
be compared to
four V-shaped
troughs with
their sides full of holes. The water enters the troughs
through the holes and overflows above. Is there a marked
difference in the size of the two pairs of gills ? A kind of

HEART.

LIVER

INT

ANT.AOD5

POST5 ADD" MUS. ,

FIG. 193. ANATOMY OF MUSSEL. (Beddard.)

MOLL USKS

101

chamber for the gills is made by the joining of the mantle
flaps below, along the ventral line. The mantle edges are
separated at two places, leaving openings called exhalent
and inJialent sipJwns.

Fresh water with its oxygen, propelled by cilia at the
opening and on the gills, enters through the lower or
inhalent siphon, passes between the gills, and goes to an
upper passage, leaving the gill chamber by a slit which
separates the gills from the foot.
For this passage, see arrow
(Fig. 194). The movement of
the water is opposite to the way
the arrow points. After going
upward and backward, the water
emerges by the exhalent siphon.
The gills originally consisted of
a great number of filaments.
These are now united, but not

completely so, and the gills still

r FIG. 194. MUSSEL.

have a perforated or lattice

A, left shell and mantle nap removed.

structure. Thus they present a B, section through body.

large surface for absorbing oxy- , Question: Guided by other figures,

J identify the parts to which lines are

gen from the water. drawn.

The mouth is in front of the foot, between it and the
anterior adductor muscle (Fig. 194). On each side of the
mouth are the labial palps, which are lateral lips (Fig. 195).
They have cilia which convey the food to the mouth after
the inhalent siphon has sent food beyond the gill -chamber
and near to the mouth. Thus both food and oxygen enter
at the inhalent siphon. The foot is in the position of a
lower lip, and if regarded as a greatly extended lower lip,
the animal may be said to have what is to us the absurd
habit of using its lower lip as a foot. The foot is some-

IO2

ANIMAL BIOLOGY

times said to be hatchet-shaped (Fig. 195). Do you see
any resemblance ? Does the foot penetrate deep or shal-
low into the sand ? (Fig. 190.) Why,
or why not ?

The food tube of the mussel is com-
paratively simple. Behind the mouth it
enlarges into a swelling called the stom-
ach (Fig. 193). The bile ducts of the
neighboring liver empty into the stomach.
The intestine makes several turns in the
substance of the upper part of the foot,
and then passing upward, it runs ap-
proximately straight to the vent (or anus),
which is in the wall of the exhalent
siphon. The intestine not only runs
through the pericardial cavity (celome)
surrounding the heart, but through the
ventricle of the heart itself (Fig. 196).

The kidneys consist of tubes which
open into the pericardial chamber above

FIG. 195. MUSSEL. From
below. Level cut across
both shells.

Se, palp; P, foot; O, mouth;
G, liver; Gg, Vg, Pg, gan-
glia.

and into the gill chamber below (Neph.,

Fig. 193). The tubes are surrounded by

numerous blood vessels (Fig. 198) and

carry off the waste matter from the blood.
The nervous system consists of three

pairs of ganglia and nerves (Fig. 197).

The ganglia are distinguishable because of
~ their orange color. The pedal

ganglia on the front of the foot
are easily seen also ; the vis-
ceral ganglia on the posterior
'/* adductor muscle may be seen
without removing the mussel

from the shell (Fig. 193). The reproductive organs
open into the rear portion of the gill cavity (Fig. 193).

The sperms, having been set free in the water, are drawn into

the ova by the same current that brings the food. The eggs

\

FIG. 196. -- HEART OF
MUSSEL, with intestine
passing through it.

MOLL USKS

103

ed

are hatched in the gills. After a while the young mussels go out
through the siphon.

Summary.- -In the gills (Fig. 198) the blood gains what?
Loses what? From the digestive tube the blood absorbs nourish-
ment. In the kidneys the blood is partly purified by the loss of
nitrogenous waste.

The cilia of the fringes on the inhalent, or lower, siphon,
vibrate continually and drive water and food particles into
the mouth cavity. Food particles that are brought near the
labial palps are conveyed by them ff

to the mouth. As the water passes
along the perforated gills, its oxygen
is absorbed ; the mantle also absorbs
oxygen from the water as it passes.
The water, as stated before, goes
next through a passage between the
foot and palp into the cavity above
the gills and on out through the ex-
halent siphon. By stirring the water,
or placing a drop of ink near the /

siphons of a mussel kept in a tub, FIG. 198. -- DIAGRAM OF

,. . r . a -i MUSSEL CUT ACROSS,

the direction of its flow may be seen. showing mantlC| ma . gills>

The pulsations of the heart are

ma.

kie\ foot,/; heart,

testine. ed.

n-

plainly visible in a living mollusk.

Habits of the Mussel. Is it abundant in clear or muddy
water ; swift, still, or slightly moving water ? Describe
its track or furrow. What is its rate of travel ? Can you
distinguish the spots where the foot was attached to the
ground ? How long is one " step " compared to the length
of the shell ? The animal usually has the valves opened
that it may breathe and eat. The hinge ligament acts like
the case spring of a watch, and holds the valves open un-
less the adductor muscles draw them together (Fig. 189).

104

ANIMAL BIOLOGY

FIG. 199. OYSTER.

C, mouth; a, vent; g,g',
ganglia; nit, mantle; b,
gill.

When the mussel first hatches from the egg, it has a tri-
angular shell. It soon attaches itself to some fish and thus

travels about ; after two months it
drops to the bottom again.

Other Mollusca. - The oysters shells
are not an exact pair, the shell which
lies upon the bottom being hollowed
out to contain the body, and the upper
shell being flat. Can you tell by ex-
amining an oyster shell which was the
lower valve ? Does it show signs of
having been attached to the bottom ?
The young oyster, like the young mus-
sel, is free-swimming. Like the arthropoda, most mollusks
undergo a metamorphosis to reach
the adult stage (Fig. 199).

Examine the shells of clams,
snails, scallops, and cockles. Make
drawings of their shells. The slug
is very similar to the snail except
that it has no shell. If the shell of tl\e snail shown in
Fig. 202 were removed, there would be left a very good

representation of a slug.

Economic Importance of
Mollusca. - - Several species
of clams are eaten. One of
them is the hard-shell clam
FIG. 201. CYPR^A. (Univalve, (quahog) found on the At-

with a long opening to shell.) i , r /-* r* A

lantic coast from Cape Cod

to Texas. Its shell is white. It often burrows slightly
beneath the surface. The soft-shell clam is better liked as
food. It lives along the shores of all northern seas. It
burrows a foot beneath the surface and extends its siphons

FIG. 200. TROCHUS.

MOLL USKS

105

through the burrow to the surface when the tide is in,
and draws into its shell the water containing animalcules
and oxygen.

Oysters to the value of many millions of dollars are gath-
ered and sold every year. The most valuable oyster fish-
eries of the United States are in Chesapeake Bay. The
young oysters, or " spat," after they attach themselves to
the bottom in shallow water, are transplanted. New oyster
beds are formed in this way. The beds are sometimes
strewn with pieces of rock, broken pottery, etc., to encourage
the oysters to attach themselves. The dark spot in the
fleshy body of the oyster is the digestive gland, or liver.
The cut ends of the tough adductor muscles are noticeable
in raw oysters. The starfish is very destructive in oyster
beds.

Pearls are deposited by bivalves around some irritating
particle that gets between the shell and the mantle. The
pearl oyster furnishes most of the pearls ; sometimes
pearls of great value are obtained from fresh-water mussels
in the United
States. Name
articles that are
made partly or
wholly of mother-
of-pearl.

Study of a Live
Snail or Slug.- -Is

its body dry or

moist ? Do land

snails and slugs have lungs or gills? Why? How many pairs

of tentacles has it? What is their relative length and position?

The eyes are dark spots at bases of tentacles of snail and at the

tips of the rear tentacles of slug. Touch the tentacles. What

happens? Do the tentacles simply stretch, or do they turn inside

FIG. 202. A SNAIL.

/, mouth; vf, kf, feelers; e, opening of egg duct; fu, fopt;
ma, mantle; lit, opening to lung; a, vent.

io6

ANIMAL BIOLOGY

out as they are extended? Is the respiratory opening on the
right or left side of the body? On the mantle fold or on the body?

(Figs. 202-3-4.) How
often does the aperture
open and close ?

Place the snail in a
FIG. 203. A SLUG.

moist tumbler. Does

the whole under surface seem to be used in creeping? Does the
creeping surface change shape as the snail creeps ? Do any folds
or wrinkles seem to
move either toward the
front or rear of its
body? Is enough mu-
cus left to mark the
path traveled? The
fold moves to the front,
adheres, and smooths
out as the slug or snail
is pulled forward.

Cephalopods. The
highest and best de-
veloped mollusks are
the Cephalopods, or " head-footed ' mollusks. Surrounding the
mouth are eight or ten appendages which serve both as feet and
as arms. These appendages have two rows of sucking disks by
which the animal attaches itself to the sea bottom, or seizes fish
or other prey with a firm grip. The commonest examples are the

squid, with a long body and ten
arms, and the octopus, or devil-
fish, with a short body and
eight arms. Cephalopods have
strong biting mouth parts and
complex eyes somewhat resem-
bling the eyes of backboned,
FIG. 205. -A SQUID. .

or vertebrate, animals. Ine

large and staring eyes add to the uncanny, terrifying appearance.

The sepia or " ink " discharged through the siphon of the squid
makes a dark cloud in the water and favors its escape from

FIG. 204. CIRCULATION AND RESPIRATION
IN SNAIL.

a, mouth; b, b, foot; c . vent; d, d, lung; 7z, heart.
Blood vessels are black. (Perrier.)

MOLLUSKS

lO/

enemies almost as
much as its swiftness
(Fig. 205). The squid
sometimes approaches
a fish with motion so
slow as to be imper-
ceptible, and then sud-
denly seizes it, and
quickly kills it by bit-
ing it on the back be-
hind the head.

The octopus is more
sluggish than the squid.
Large species called
devilfish sometimes have a spread of arms of twenty-five feet.
The pearly nautilus (Fig. 206) and the female of the paper argo-
naut (Fig. 207) are examples of cephalopods that have shells.
The cuttlefish is closely related to the squid.

FIG. 206. --PEARLY NAUTILUS. (Shell sawed
through to show chambers used when it was
smaller, and siphuncle, S, connecting them. Ten-
tacles, T.}

FIG. 207. PAPER ARGONAUT (female).

x % (i.e. the animal is three times as long

and broad as figure) .

FIG. 208. PAPER ARGO-
NAUT (male), x i/ 2 .

General Questions. - The living parts of the mussel are
very soft, the name mollusca having been derived from
the Latin word mollis, soft. Why is it that the softest
animals, the mollusks, have the hardest coverings ?

To which class of mollusks is the name acephala (head-
less) appropriate ? Lamellibranchiata (platelike gills) ?

io8

ANIMAL BIOLOGY

Why is a smooth shell suited to a clam and a rough
shell suited to an oyster ? Why are the turns of a snail's
shell so small near the center ?

Why does the mussel have no use for head, eyes, or pro-
jecting feelers? In what position of the valves of a mussel
is the hinge ligament in a stretched condition ? How does
the shape of the mussel's gills insure that the water cur-
rent and blood current are brought in close contact ?

The three main classes of mollusks are : the pelecypoda
(hatchet-footed); gastropoda (stomach-footed); and cepha-
lopoda (head-footed). Give an example of each class.

Comparison of Mollusks

MUSSEL

SNAIL

SQUID

Shell

Head

*

Body

Foot

Gills

Eyes

i

Comparative Review. - - (To occupy an entire page in notebook.)

GRASS-
HOPPER

SPIDER

CRAYFISH

CENTIPEDE

MUSSEL

Bilateral or radiate

Appendages for lo-
comotion

Names of divisions
of body

Organs and method
of breathing

Locomotion

CHAPTER X

FISHES

SUGGESTIONS.
The behavior of a
live fish in clear
water, preferably in
a glass vessel or an
aquarium, should be
studied. A skeleton may be
prepared by placing a fish in
the reach of ants. Skeletons
of animals placed on ant beds
are cleaned very thoroughly.

The study of the perch, that follows, will apply to almost any
common fish.

Movements and External Features.- -What is the gen-
eral shape of tJie body of a fish ? How does the dorsal, or
upper, region differ in form from the ventral ? Is there a
narrow part or neck where the head joins the trunk?
Where is the body thickest? What is the ratio between
the length and height ? (Fig. 209.) Are the right and left
sides alike ? Is the symmetry of the fish bilateral or
radial ?

The body of the fish may be divided into three regions,
the head, trunk, and tail. The trunk begins with the
foremost scales ; the tail is said to begin at the vent, or
anus. Which regions bear appendages ? Is the head
movable independently of the trunk, or do they movq
together ? State the advantage or disadvantage in this,
Is the body depressed (flattened vertically) or compressed

109

no

ANIMAL BIOLOGY

(flattened laterally) ? Do both forms occur among fishes ?
(See figures on pages 123, 124.)

How is the sJiape of the body advantageous for move-
ment ? Can a fish turn more readily from side to side, or
up and down ? Why ? Is the head wedge-shaped or coni-
cal ? Are the jaws flattened laterally or vertically? The
fish swims in the water, the bird swims in the air. Account
for the differences in the shape of their bodies.

Is the covering of tJie body like the covering of any ani-
mal yet studied ? The scales are attached in little pockets,

l(( , , I I <( I I " , (

i i 1 1 ii 1 1 1 1 1 !,
L l -u,..i <. ^

FIG. 209. WHITE PERCH (Morone Americana).

or folds, in the skin. Observe the shape and size of scales
on different parts of the body. What parts of the fish are
without scales ? Examine a single scale ; what is its
shape ? Do you see concentric lines of growth on a scale ?
Sketch a few of the scales to show their arrangement.
What is the use of scales ? Why are no scales needed on
the head ? How much of each scale is hidden ? Is there
a film over the scale ? Are the colors in the scale or
on it ?

The Fins.- -Are the movements of the fish active or
sluggish ? Can it remain stationary without using its fins ?

FISHES 1 1 1

Can it move backward ? How are the fins set in motion ?
What is the color of the flesh, or muscles, of a fish ? Count
the fins. How many are in pairs ? (Fig. 209.) How many
are vertical ? How many are on the side ? How many
are on the middle line ? Are the paired or unpaired fins
more effective in balancing the fish ? In turning it from
side to side ? In raising and lowering the fish ? In pro-
pelling it forward ? How are some of the fins useful to
the fish besides for balancing and swimming ?

The hard spines supporting the fins are called the fin
rays. The fin on the dorsal line of the fish is called the
dorsal fin. Are its rays larger or smaller than the rays of
the other fins ? The perch is sometimes said to have two
dorsal fins, since it is divided into two parts. The fin
forming the tail is called the tail fin, or caudal fin. Are
its upper and lower corners alike in all fishes ? (Fig. 228.)
On the ventral side, just behind the vent, is the ventral
fin, also called the anal fin. The three fins mentioned are
unpaired fins. Of the four-paired fins, the pair higher on
the sides (and usually nearer the front) are the pectoral
fins. The pair nearer the ventral line are the pelvic fins.
They are close together, and in many fish are joined
across the ventral line. The ventral fins are compared to
the legs, and the pectoral fins to the arms, of higher verte-
brates. (Fig. 244.) Compare fins of fish, pages 123, 124.

Make a drawing of the fish seen from the side, omit-
ting the scales unless your drawing is very large.

Are the eyes on the top or sides of the head, or both ?
Can a fish shut its eyes ? Why, or why not ? Is the eye-
ball bare, or covered by a membrane ? Is the covering of
the eyeball continuous with the skin of the head ? Is
there a fold or wrinkle in this membrane or the surround-
ing skin ? Has the eye a pupil ? An iris ? Is the eye of

112

ANIMAL BIOLOGY

FIG. 210. BLACKBOARD OUTLINE OF FISH.

the fish immovable, slightly movable, or freely movable ?
Can it look with both eyes at the same object ? Is the
range of vision more upward or downward ? To the front

or side ? In what
direction is vision
impossible ? Can a
fish close its eyes
in sleep ? Does
the eyeball appear
spherical or flat-
tened in front ?
The ball is really
spherical, the lens is very convex, and fish are nearsighted.
Far sight would be useless in a dense medium like water.

In what direction are the nostrils from the eyes? (Fig.
211.) There are two pairs of nostrils, but only one pair of
nasal cavities, with two nostrils opening into each. There
are no nasal passages to the mouth,
as the test with a probe shows
that the cavities do not open into
the mouth. What two functions
has the nose in man ? What func-
tion has it in the fish ?

There are no external ears.
The ear sacs are embedded in the
bones of the skull. Is hearing acute or dull? When fish-
ing, is it more necessary not to talk or to step lightly,
so as not to jar the boat or bank ?

What is the -use of the large openings found at the back
of the head on each side ? (Fig. 211.) Under the skin at
the sides of the head are thin membrane bones formed from
the skin ; they aid the skin in protection. Just under these
membrane bones are the gill covers, of true bone. Which

FIG. 211. HEAD OF CARP.

FISHES 1 1 3

consists of more parts, the membranous layer, or the true
bony layer in the gill cover ? (Figs. 21 1 and 21 2.)

Is the mouth large or small ? Are the teeth blunt or
pointed ? Near the outer edge, or far in the mouth ?
(Fig. 212.) Does the fish have lips? Are the teeth in
one continuous row in either jaw? In the upper jaw
there are also teeth on the premaxillary bones. These
bones are in front of the maxillary bones, which are with-
out teeth. Teeth are also found in the roof of the mouth,
and the tongue bears horny appendages similar to teeth.
Are the teeth of the fish better suited for chewing or for

FIG. 212. SKELETON OF PERCH.

grasping ? Why are teeth on the tongue useful ? Watch
a fish eating : does it chew its food ? Can a fish taste ?
Test by placing bits of brown paper and food in a vessel
or jar containing a live fish. Is the throat, or gullet, of the
fish large or small ?

The skeleton of a fish is simpler than the skeleton of
other backboned animals. Study Fig. 212 or a prepared
skeleton. At first glance, the skeleton appears to have
two vertebral columns. Why ? What bones does the fish
have that correspond to bones in the human skeleton ?
Are the projections (processes) from the vertebrae long or
short ? The ribs are attached to the vertebrae of the trunk,
the last rib being above the vent. The tail begins at the

ANIMAL BIOLOGY

vent. Are there more tail vertebrae or trunk vertebrae ?
Are there any neck (cervical) vertebrae (i.e. in front of
those that bear ribs)? The first few ribs (how many ?) are
attached to the central body of the vertebrae. The re-

FIG. 213.

maining ribs are loosely attached to processes on the
vertebrae. The ribs of bony fishes are not homologous
with the ribs of the higher vertebrates. In most fishes
there are bones called intermuscular bones attached to the
first ribs (how many in the perch ?) which are possibly homol-
ogous to true ribs ; that is, true ribs in the higher verte-
brates may have been developed from such beginnings.

Which, if any, of the fin skeletons (Fig. 214) are not
attached to the general skeleton ? Which fin is composed
chiefly of tapering, pointed rays ? Which fins consist of

rays which sub-
divide and widen

FIG. 214. SOFT-RAYED AND SPINY-RAYED FINS.

toward the end ?
Which kind are
stiff, and which are
flexible ? Which of
the fin rays are segmented, or in two portions ? The outer
segment is called the radial, the inner the basal segment.
Which segments are longer ? There is one basal segment
that lacks a radial segment; find it (Fig. 212).

FISHES

FIG. 215. -- CARP, with
right gill cover removed
to show gills.

What is the advantage of the backbone plan of struc-
ture over the armor-plate plan ? You have seen the spool-
like body of the vertebra in canned salmon. Is it concave,
flat, or convex at the ends ?

The gills are at the sides of the head (Fig. 215) under
the opercula, or gill covers. What is the color of the gills ?
Do the blood vessels appear to be
very near the surface of the gills, or
away from the surface ? What advan-
tage in this ? Are the gills smooth
or wrinkled ? (Fig. 215.) What ad-
vantage ? The bony supports of the
gills, called the gill arches, are shoxvn
in Fig. 216 (j to 4 ). How many
arches on each side? The gill arches have projections
on their front sides, called gill rakers, to prevent food

from being washed
through the clefts
between the arches.
The fringes on the
rear of the gill
arches are called
the gill filaments (a,
Fig. 216). These
filaments support
the thin and much-
wrinkled borders of
the gills, for the
gills are constructed
on the plan of exposing the greatest possible surface to
the water. Compare the plan of the gills and the human
lungs. The gill opening on each side is guarded by
seven rays (kh, Fig. 216) along the hinder border of the

FIG. 216. SKELETON AROUND THROAT OF FISH.

n6

ANIMAL BIOLOGY

gill cover. These rays grow from the tongue bone. (Zu,

Fig. 216. This is a rear view.)

Watch a live fish and determine how the water is forced

between the gills. Is the mouth opened and closed in the
act of breathing? Are the openings behind
the gill covers opened and closed ? How

B

FIG. 217.

CIRCULATION
IN GILLS.

FIG. 218. NOSTRILS, MOUTH, AND GILL OPENINGS OF

STING-RAY.

many times per minute does fresh water reach
the gills ? Do the mouth and gill covers
open at the same time ? Why must the water
in contact with the gills be changed constantly ? Why

does a fish usually rest with its

head up stream ? How may a
fish be kept alive for a time
after it is removed from the
water ? Why does drying of
the gills prevent breathing ? If
the mouth of a fish were propped open, and the fish re-
turned to the water, would it suffocate ? Why, or why not?

a I

FIG. 219. GILL OPENINGS OF
EEL.

Food Tube. The gullet is short and wide. The stomach is
elongated (Fig. 220). There is a slight constriction, or narrow-
ing, where it joins the intestine. Is the intestine straight, or does
it lie in few or in many loops? (Fig. 220.) The liver has a gall
bladder and empties into the intestine through a bile duct. Is the

FISHES

117

liver large or small? Simple or lobed? The spleen (mi, Fig. 220)
lies in a loop of the intestine. The last part of the intestine is
straight and is called the rectum. Is it of the same size as the
other portions of the intestine? The fish does not possess a pan-
creas, the most important digestive gland of higher vertebrates.

ma

FIG. 220. ANATOMY OF CARP. (See also colored figure 4.)

bf, barbels on head (for feeling) ; h, ventricle of heart; as, aortic bulb for regulating flow to
gills; vk, venous sinus; ao, dorsal aorta; ma, stomach; /, liver; gb, gall cyst; mi, spleen;
d, small intestine; md, large intestine; rt,vent; s, s, swim bladder; ni,ni, kidney; hi,
ureter; hb, bladder; ro, eggs (roe>; mhe, opening of ducts from kidney and ovary.

Questions: Are the kidneys dorsal or ventral ? The swim bladder ? Why? Why is the
swim bladder double ? Does blood enter gills above or below ?

The ovary lies between the intestine and the air bladder. In Fig.
220 it is shown enlarged and filled with egg masses called roe. It
opens by a pore behind the vent. The silver lining of the body cavity
is called the peritoneum. (See Chap. VII, Human Biology.)

Is the air bladder simple or partly divided in the perch? In the carp?
(Fig. 220.) Is it above or below the center of the body? Why?" The
air bladder makes the body of the fish about as light as water that it
may rise and sink with little effort. When a fish dies, the gases of
decomposition distend the bladder and the abdomen, and the fish turns
over. Why ?

Where are the kidneys? (Fig. 220.) Their ends unite close under
the spinal column. The ureters, or tubes, leading fro.m them, unite,
and after passing a small urinary bladder, lead to a tiny urinary pore
just behind the opening from the ovary. (Colored figure 4.)

The Circulation. The fish, unlike other vertebrates, has its
breathing organs and its heart in its head. The gills have already
been described. The heart of an air-breathing vertebrate is near

ANIMAL BIOLOGY

its lungs. Why? The heart of a fish is near its gills for the same
reason. The heart has one auricle and one ventricle. (Colored
figure i.)

Blood returning to the heart comes through several veins into a
sinus, or antechamber, whence it passes down through a valve

FIG. 221. PLAN OF CIRCULATION.

A b, arteries to gills; Ba, aortic bulb; V, ventricle.

into fas auricle ; from the auricle it goes forward into the ventricle.

The ventricle sends it into an artery, not directly, but through a

bulb (as, Fig. 220), which serves to maintain
a steady flow, without pulse beats, into the
large artery (aorta) leading to the gills. The
arteries leading from the gills join to form a
dorsal aorta (Ao, Fig. 221), which passes
backward, inclosed by the lower processes of
the spinal column. After going through the
capillaries of the various organs, the blood
returns to the heart through veins.

The color of the blood is given by red
corpuscles. These are nucleated, oval, and
larger than the blood corpuscles of other ver-
tebrates. The blood of the fish is slightly
above the temperature of the water it in-
habits.

Notice the general shape of the brain
(Fig. 222). Are its subdivisions distinct or
indistinct? Are the lobes in pairs? The
middle portion of the brain is the widest,

and consists of the two optic lobes. From these lobes the optic

nerves pass beneath the brain to the eyes (Sn, Fig. 223). In

FIG. 222. BRAIN OF
PERCH, from above.

, end of nerve of smell ;
an, eye; v, z, m, fore,
mid, and hind brain;
h, spinal bulb; r, spi-
nal cord.

FISHES

119

front of the optic lobes lie the two cerebral lobes, or the cerebrum.
The small olfactory lobes are seen (Fig. 224) in front of the cere-
brum. The olfactory nerves may be traced to the nostrils. Back
of the optic lobes (mid brain) is the cerebellum (hind brain), and

back of it is the medulla oblongata,
or beginning of the spinal cord.

FIG. 223. BRAIN OF PERCH,
side view.

FIG. 224. BRAIN OF PERCH,
from above.

Taking the eyeball for comparison, is the whole brain as large
as one eyeball? (Fig. 222.) Judging from the size of the parts of
the brain, which is more important with the fish, thinking or per-
ception? Which is the most important sense?

The scales along a certain line on each side of the fish, called
the lateral line, are perforated over a series of lateral line sense
organs, supposed to be the chief organs of touch (see Fig. 209).

Questions. Which of the fins of the fish have a use
which corresponds to the keel of a boat ? The rudder ? A

:.

"%;-**'' * -

" i ^~v

Njir v % .saw*.* ' " - ' . v k .
*}?> ji'Y '''V/ v >

S i ,

,_^^*ss^:

TT-T '- V- --r*f*y - - . - ^ *

FlG. 225. THE STICKLEBACK. Instead of depositing the eggs on
the bottom, it makes a nest of water plants the only fish that does
so and bravely defends it.

I2O

ANIMAL BIOLOGY

FIG. 226. ARTIFICIAL FECUNDATION. The
egg-cells and sperm-cells are pressed out into
a pan of water.

paddle for sculling ?
An oar? State several
reasons why the head
of the fish must be
very large, although
the brain is very small.
Does all the blood go
to the gills just after
leaving the heart ?

Make a list of the
different species of
fish found in the
waters of your neigh-
borhood ; in the markets of your town.

Reproduction. The female fish deposits the unfertilized
eggs, or ova, in a secluded spot on the bottom. Afterward
the male fish deposits the sperms in the same place (see
Fig. 225). The eggs, thus unprotected, and newly hatched
fish as well, are used for food by fish of the same and other
species. To compensate for this great destruction, most
fish lay (spawn) many thousands of eggs, very few of
which reach maturity. Higher vertebrates (e.g. birds) have,
by their superior in-
telligence, risen above
this wasteful method
of reproduction. Some
kinds of marine fish,
notably cod, herring,
and salmon, go many
miles up fresh rivers
to spawn. It is possible that this is because they were
originally fresh-water species ; yet they die if placed in
fresh water except during the spawning season. They go

FIG. 227. NEWLY HATCHED TROUT, with
yolk-sac adhering, eyes large, and fins mere
folds of the skin. (Enlarged.)

FISHES 1 2 1

because of instinct, which is simply an inherited habit.
Rivers may be safer than the ocean for their young. They
are worn and exhausted by the journey, and never survive
to lay eggs the second time.

FIG. 228. A SHARK (Acanthias vulgaris).

The air bladder is developed from tJie food tube in the
embryo fish, and is homologous with lungs in the higher
vertebrates. Are their functions the same ?

Fish that feed on flesh have a short intestine. Those
that eat plants have a long intestine. Which kind of food
is more quickly digested ?

There are mucous glands in the skin of a fish which
supply a secretion to facilitate movement through the
water ; hence a freshly caught fish, before the secretion
has dried, feels very slippery.

The air bladder, although homologous to lungs, is not a
breathing organ in common fishes. It is filled by the
formation of gases from the blood, and can be made
smaller by the contraction of muscles along the sides of
the body ; this causes the fish to sink. In the gar and
other ganoids, the air bladder contains blood vessels, is con-
nected with the gullet, and is used in breathing. Organs
serving the same purpose in different animals are said to be
analogous. To what in man are the gills of the fish analo-
gous ? Organs having a like position and origin are
said to be homologous. The air bladders of a fish are
homologous with the lungs of man ; but since they have
not the same use they are not analogous.

122

ANIMAL BIOLOGY

How does the tail of a shark or a gar differ from the
tail of common fishes ? (Fig. 228.) Do you know of fish
destitute of scales ? Do you know of fish with whiplike
feelers on the head ? (Figs.) Why are most fishes white
on the under side ?

Comparative Review. (Copy table on one page or two facing pages
of notebook.)

IS THERE

A HEAD?
A NECK?

METHOD OF
FEEDING

DIGESTIVE
ORGANS AND
DIGESTION

REPRODUC-
TION

SENSES

Ameba

Sponge

Hydra

Starfish

Earthworm

Wasp

Mussel

Fish

wm^^^^j^

FIG. 229. DRAWING THE SEINE.

FIG. 230. SUNFISH.

FIG. 235. CARP.

FIG. 231.-- TUNNY

FIG. 236. HERRING.

FIG. 232. SWORDFISH.

FIG. 237. SPECKLED TROUT.

FIG. 233. SWELLFISH.

FIG. 238. PERCH.

FIG. 234. --TURBOT. FIG. 239. SALMON.

Seven Food Fish. Three Curious Fish.
SPECIAL REPORTS. (Encyclopedia, texts, dictionary.)

123

FIG. 243. LANTERN FISH (Linophryne lucifer}. (After Collett.)

FIG. 240.-
SEA HORSE ,

( Hippocampus) ,
with incubat-
ing pouch, Brt.

FIG. 244. LUNG FISH of Australia
( Ceratodus m iolepis) .

FIG. 241. BAND FISH.

FIG. 245. TRUNK FISH.

FIG. 242. TORPEDO. Elec-
trical organs at right and
left of brain.

FIG. 246. SEAWEED FISH.
{Phyllopteryx egues) .

Remarkable Fish. SPECIAL REPORTS. (Encyclopedia, texts, dictionary.)

124

GENERAL CLASSIFICATION 125

RECOGNITION GROUP CHARACTERS

The commoner members of the several branches may be recog-
nized by the following characters :

1. The Protozoans are the only one-celled animals.

2. The Sponges are the only animals having pores all over the
body for the inflow of water.

3. The Polyps are the only many-celled animals having a single
opening into the body, serving for both mouth and vent. They
are radiate in structure, and usually possess tentacles.

4. The Echinoderms are marine animals of more or less radiate
appearance, having a food tube in the body separate from the
body wall.

The following groups are plainly bilateral : that is, dorsal and
ventral surfaces, front and hind ends are different.

5. The Vermes have usually a segmented body but lack jointed
legs.

6. The Arthropods have an external skeleton and jointed legs.

7. The Mollusks have soft bodies, no legs, no skeleton, but
usually a limy shell.

8. The Vertebrates have an internal skeleton of bones, and
usually two pairs of legs. ^

CHAPTER XI

BATRACHIA

THE theory of evolution teaches that animal life began in a very
simple form in the sea, and that afterward the higher sea animals
lost their gills and developed lungs and legs and came out to live
upon the land ; truly a marvelous procedure, and incredible to
many, although the process is repeated every spring in count-
less instances in pond and brook.

In popular language, every cold-blooded vertebrate breathing
with lungs is called a reptile. The name reptile is properly
applied only to lizards, snakes, turtles, and alligators. The com-
mon mistake of speaking of frogs and salamanders as reptiles
arises from considering them only in their adult condition. Rep-
tiles hatch from the egg as tiny reptiles resembling the adult
forms ; frogs and salamanders, as every one knows, leave the egg
in the form of tadpoles (Fig. 248). The fact that frogs and
salamanders begin active life as fishes, breathing by gills, serves to
distinguish them from other cold-blooded animals, and causes
naturalists to place them in a separate class, called batrachia

(twice breather) or amphibia (double life).

TADPOLES

SUGGESTIONS. - -Tadpoles may be studied by placing a number
of frog's eggs in a jar of water, care being taken not to place
a large number of eggs in a small amount of water. When they
hatch, water plants (e.g. green algae) should be added for food.
The behavior of frogs may be best studied in a tub of water. A
toad in captivity should be given a cool, moist place, and fed well.
A piece of meat placed near a toad may attract flies, and the toad
may be observed while catching them, but the motion is so swift
as to be almost imperceptible. Live flies IT ay be put into a glass
jar with a toad. Toads do not move about until twilight, except

126

BATRACHIA

127

in cloudy, wet weather. They return to ponds and brooks in
spring at the time for laying eggs. This time for both frogs and
toads is shown by trilling. All frogs, except tree frogs, remain in
or near the water all the year.

FIG. 248. METAMORPHOSES OF THE FROG, numbered in order.

Do eggs hatch and tadpoles grow more rapidly in a
jar of water kept in a warm place or in a cold place ?
In pond water or drinking water ? Can the tadpoles be
seen to move in the eggs before hatching ? When do
the external gills show ? (Fig. 248.)

What parts may be described in a tadpole ? What is
the shape of the tail ? Compare tJie tadpole with the fish
as to (i) general
shape, (2) cover-
ing, (3) fins, (4)
tail, (5) gills.

Do the exter-
nal gills disap-
pear before or after any rudiments of limbs appear ?
(6, 7, Fig. 248.) Can you locate the gills after they be-
come internal ? (Fig. 249.)

FIG. 249. TADPOLE, from below, showing intestine
and internal gills. (Enlarged.)

128 ANIMAL BIOLOGY

In what state of growth are the legs when the tadpole
first goes to the surface to breathe ? Which legs appear
first ? What advantage is this ? What becomes of the
tail ? Is the tail entirely gone before the frog first leaves
the water ? Are tadpoles habitually in motion or at
rest ?

Is the intestine visible through the skin ? (Fig. 249.)
Is it straight or coiled ? Remembering why some fish
have larger intestines than others, and that a cow has a
long intestine and a cat a short one, state why a tad-
pole has a relatively longer intestine than a frog.

Compare the mouth, jaws, eyes, skin, body, and habits
of tadpole and frog.

FROGS

Prove that frogs and toads are beneficial to man. Did
you ever know of a frog or toad destroying anything
useful, or harming any one, or causing warts ? How
many pupils in class ever had warts ? Had they handled
frogs before the warts came ? Frogs are interesting,
gentle, timid animals. Why are they repulsive to some
people ?

Environment. Where are frogs found in greatest
numbers ? What occurs when danger threatens them ?
What enemies do they have ? \yhat color, or tint, is most
prominent on a frog ? Does the color " mimic " or imi-
tate its surroundings ? What is the color of the under
side of the body ? (Fig. 250.) Why is there greater
safety in that color ? What enemies would see water frogs
from below ? Do tree frogs mimic the bark ? The
leaves ?

Can a frog stay iinder water for an indefinite time ?
Why, or why not ? What part of a frog is above the

BATRACHIA

129

surface when it floats or swims in a tub of water ? Why ?
Do frogs croak in the water or on the bank ? Why do
they croak after a rain ? Do toads croak ?

Are the eggs laid in still or flowing water ? In a clear
place or among sticks and stems ? Singly, or in strings or
in masses ? (Fig. 248.) Describe an egg. Why do frogs
dig into the mud in autumn in cold climates ? Why do
they not dig in mud at the bottom of a pond ? Why is
digging unnecessary in the Gulf states ?

. -S

FIG. 250. PAINTED FROG {Chorophilus ornatus), of Mexico.

Describe the position of the frog when still (Fig. 250).
What advantage in this position ? Does the frog use
its fore legs in swimming or jumping ? Its hind legs ?
How is the frog fitted for jumping ? Compare it in this
respect with a jumping insect; a jumping mammal. How
is it fitted for swimming ? Is the general build of its body
better fitted for swimming or jumping? How far can a
frog jump ?

External Features. The frog may be said to have two
regions in its body, the head and trunk. A neck hardly

130 ANIMAL BIOLOGY

exists, as there is only one vertebra in front of the shoul-
ders (Fig. 252), while mammals have seven neck (cervical)
vertebrae. There are no tail (caudal) vertebrae, even in the
tadpole state of frogs and toads.

The head appears triangular in shape when viewed from
what direction ? The head of a frog is more pointed than
the head of a toad. Is the skull a closed case of broad
bones or an open structure of narrow bones ? (Fig. 252.)

Describe the mouth. Observe the extent of the mouth
opening (Fig. 251). Are teeth present in the upper jaw?
The lower jaw ? Are the teeth sharp or dull ? Does the

frog chew its food ? Is the tongue
slender or thick? (Fig. 251.) Is
it attached to the front or the back
of the mouth ? In what direction
does the free end extend when the
tongue lies flat? Is the end pointed

or lobed ? How far out will the
FIG. 251. HEAD OF FROG.

tongue stretch ? For what is it

used ? Why is it better for the teeth to be in the upper
, jaw rather than in the lower jaw? That the teeth are of
little service is shown by the fact that the toad with simi-
lar habits of eating has no teeth. Will a toad catch and
swallow a bullet or pebble rolled before it ? The toad is
accustomed to living food, hence prefers a moving insect
to a still one.

The Senses. Compare the eyes with the eyes of a
fish in respect to position and parts. Are the eyes pro-
truding or deep-set ? Touch the eye of a live frog. Can
it be retracted ? What is the shape of the pupil ? The
color of the iris ? Is the eye bright or dull ? What
probably gave rise to the superstition that a toad had a
jewel in its head? Is there a third eyelid? Are the

B ATRAC HI A

upper and lower eyelids of the same thickness ? With
which lid does it wink ? Close its eye ?

Observe the large oval ear drum or tympanum. What
is its direction from the eye? (Fig. 251.) The mouth?
Is there a projecting ear? Does the frog hear well?
What reason for your answer ? As in the human ear, a
tube (the Eustachian tube) leads from the mouth to the
inner side of the tympanum.

How many nostrils? (Fig. 251.) Are they near to-
gether or separated ? Large or small ? A bristle passed
into the nostril comes into the mouth not far back in the
roof. Why must it differ from a fish in this ?

How do \htfore and liind legs differ ? How many toes
on the fore foot or hand ? On the hind foot ? On which
foot is one of the toes rudimentary ? Why is the fore limb
of no assistance in propelling the body in jumping ? Do
the toes turn in or out? (Fig. 250.) How does the frog
give direction to the
jump ? What would
be the disadvantage
of always jumping
straight forward
when fleeing? Which
legs are more useful
in alighting ?

Divisions of the
Limbs.- -Distinguish
the upper arm, fore-
arm, and hand in the
fore limb (Figs. 252 and 253). Compare with skeleton of
man (Fig. 399). Do the arms of a man and a frog both
have one bone in the upper arm and two in the forearm ?
Both have several closely joined bones in the wrist and

FIG. 252. SKELETON OF FROG.

132

ANIMAL BIOLOGY

five separate bones in the palm. Do any of the frog's
fingers have three joints ? Compare also tJie leg of man

and the hind leg
of the frog (Figs.
253 and 399). Does
the thigh have one
bone in each ? The
shank of man has
two bones, shin and
splint .bone. Do
you see a groove
near the end in the
shank bone of a
frog (Fig. 252), in-
dicating that it
was formed by the

union of a shin and

FIG. 253. SKELETON OF FROG. v i, > -ru

splint bone ? The

first two of the five bones of the ankle are elongated, giv-
ing the hind leg the appearance of
having an extra joint (Fig. 253). The
foot consists of six digits, one of which,
like the thumb on the fore limb, is
rudimentary. The five developed toes
give the five digits of the typical verte-
brate foot. Besides the five bones cor-
responding to the instep, the toes have
two, three, or four bones each. How
is the hind foot specialized for swim-
ming? Which joint of the leg con-
tains most muscle? (Fig. 254.) Find other bones of the
frog analogous in position and similar in form to bones in
the human skeleton.

FIG. 254. LEG MUS-
CLES OF FROG.

BATRACHIA

133

Is the skin of a frog tight or loose ? Does it have any
appendages corresponding to scales, feathers, or hair of
other vertebrates ? Is the skin rough or smooth ? The
toad is furnished with glands in the skin which are some-
times swollen ; they form a bitter secretion, and may be,
to some extent, a protection. Yet birds and snakes do not
hesitate to swallow toads whole. Show how both upper
and under surfaces of frog illustrate protective coloration.

All batrachians have large and numerous blood vessels
in t/ie skin by which gases are exchanged with the air,
the skin being almost equal to a third lung. That the
skin may function in this way, it
must not become dry. Using this
fact, account for certain habits of
toads as well as frogs.

If a frog is kept in the dark or
on a dark surface, its skin will be-
come darker than if kept in the light
or on a white dish. Try this experi-
ment, comparing two frogs. This
power of changing color is believed
to be due to the diminution in size
of certain pigment cells by contrac-
tion, and enlargement from relaxation.
This power is possessed to a certain
degree not only by batrachians but
also by many fishes and reptiles.
The chameleon, or green lizard of
the Gulf states, surpasses all other
animals in this respect (Fig. 280).
What advantage from this power ?

Digestive System. - The large mouth cavity is connected
by a short throat with the gullet, or esophagus (Fig. 255).

a-

9-J.

FIG. 255. DIGESTIVE
CANAL OF FROG.

Mh, mouth; Z, tongue pulled
outward; S. opening to
larynx; Oe, gullet; M, stom-
ach; D, intestine; P, pan-
creas; L, liver; G, gall
bladder; R, rectum; Hb,
bladder; Cl, cloaca; A,
vent.

134

ANIMAL BIOLOGY

A slit called the glottis opens from the throat into the
lungs (Fig. 255). Is the gullet long or short? Broad
or narrow? Is the stomach short or elongated? Is the
division distinct between the stomach and gullet, and
stomach and intestine ? Is the liver large or small ? Is
it simple or lobed ? The pancreas lies between the
stomach and the first bend of the intestines (Fig. 255).
What is its shape ? A bile duct connects the liver with

the small intestine (Dc, Fig.
255). It passes through the
pancreas, from which it re-
ceives several pancreatic
ducts. After many turns, the
small intestine joins the large
intestine. The last part of
the large intestine is called
the rectum (Latin, straight).
The last part of the rectum is
called the cloaca (Latin, a
drain), and into it the ducts
from the kidneys and repro-
ductive glands also open. The
kidneys are large, elongated,
and flat. They lie under the
dorsal wall. The urinary bladder is also large. Does the
salamander have a similar digestive system? (Fig. 256.)
Why are the liver and lungs (Fig. 256) longer in a sala-
mander than in a frog ?

Respiration.- -How many lungs? Are they simple
or lobed ? (Fig. 256.) A lung cut open is seen to be
baglike, with numerous ridges on its inner surface.
This increases the surface with which the air may come
in contact. In the walls of the lungs are numerous

FIG. 256. ANATOMY OF SALA-
MANDER.

I a t heart; 2, lungs; j a, stomach; 3 b, in-
testine; _j c, large intestine; 4, liver;
5, egg masses ; 10, bladder; a , vent.

BATRACHIA 135

'capillaries. Does the frog breatJie with moutJi open or
closed? Does the frog have any ribs for expanding the
chest ? What part of the head expands and contracts ?
Is this motion repeated at a slow or rapid rate ? Regu-
larly or irregularly ? There are valves in the nostrils for
opening and closing them. Is there any indication of
opening and closing as the throat expands and contracts ?
The mouth and throat (pharynx) are filled with air each
time the throat swells, and the exchange of gases (which
gases ?) takes place continually through their walls and
the walls of the lungs. At intervals the air is forced
through the glottis into the lungs. After a short time
it is expelled from the lungs by the muscular abdominal
walls, which press upon the abdominal organs, and so
upon the lungs. Immediately the air is forced back
into the lungs, so that they are kept filled. In some
species the lungs regularly expand at every second con-
traction of the throat. This is shown by a slight out-
ward motion at the sides. Does the motion of the throat
cease when the frog is under water ? Why would the
frog be unable to breathe (except through the skin) if its
mouth were propped open ? Why does the fact that the
breathing is so slow as to almost cease when hibernat-
ing, aid the frog in going through the winter without
starving? (Chap. I.) Why must frogs and toads keep their
skins moist ? Which looks more like a clod ? Why ?

The Heart and Circulation.- -What is the shape of the heart?
(Fig. 257.) Observe the two auricles in front and the conical
ventricle behind them. The great arterial trunk from the ventricle
passes forward beyond the auricles ; it divides into two branches
which turn to the right and left (Fig. 257). Each branch im-
mediately subdivides into three arteries (Fig. 257), one going to
the head, one to the lungs and skin, and a third, the largest,

136

ANIMAL BIOLOGY

OL

passes backward in the trunk, where it is united again to its'

fellow. (Colored Fig. 2.)

Both of the pulmonary veins, returning to the heart with pure

blood from the lungs, empty into the left auricle. Veins with the

impure blood from the body empty into the right auricle. Both

the auricles empty into the ventri-
cles, but the pure and impure blood
are prevented from thoroughly mix-
ing by ridges on the inside of the
ventricle. Only in an animal with
a four-chambered heart does pure
blood from the lungs pass unmixed
and pure to all parts of the body,

FIG. 257. PLAN OF FROG'S
CIRCULATION.

Venous system is black; the arterial,
white. A U, auricles ; I', ventricle;

L, lung; LIV, liver. Aorta has one FlG. 258. FROG'S BLOOD (magnified 2500

branch to right, another to left, which areas). Red cells oval, nucleated, and

reunite below. Right branch only ]arger than human blood cells. Nuclei of

persists in birds, left branch in beasts twQ white cel]s yisible near centen ( p ea .

and man. , , ,

body.)

and only such animals are warm-blooded. The purer (i.e. the more
oxygenated) the blood, the greater the oxidation and warmth.

The red corpuscles in a frog's blood are oval and larger than those
of man. Are all of them nucleated ? (Fig. 258.) The flow of blood m
the web of a frog's foot is a striking and interesting sight. It may
be easily shown by wrapping a small frog in a wet cloth and laying
it with one foot extended upon a glass slip on the stage of a
miscroscope.

BA TRA CHI A

137

01-

cir

The brain of the frog (Fig. 259) is much like that of a fish
(Fig. 224). The olfactory, cerebral, and optic lobes, cerebellum
and medulla are in the same relative position, although their rela-
tive sizes are not the same. Compared with the

other parts, are the

olfactory lobes more

or less developed

than in a fish? The

cerebral hemispheres ?

The optic lobes? The

cerebellum? There is

a cavity in the brain.

It is readily exposed

on the under surface

of the medulla by cut-
ting the membrane,

which is there its only

covering (Fig. 259).

FIG. 259.
BRAIN OF FROG.

FIG. 260. NERVOUS SYSTEM
OF FROG.

Frogs and toads are beneficial (why ?) and do not the slight-
est injury to any interest of man. If toads are encouraged
to take up their abode in a garden, they will aid in ridding
it of insects. A house may be made in a shady corner with
four bricks, or better still, a hole a foot deep may be dug to
furnish them protection from
the heat of the day. A toad's
muzzle is not so tapering as a
frog's (why ?), its feet are not
so fully webbed (why?), and its
skin is not so smooth (why ?).
Incase of doubt open the mouth
and rub the finger along the up-
per jaw; a frog has sharp teeth,
a toad none at all. The tadpoles of frogs, toads, and sala-
manders are much alike. In toad's spawn the eggs lie in
strings inclosed in jelly ; frogs spawn is in masses (Fig. 248).

FIG. 261. Position of legs in tail-
less (A) and tailed (#) amphibian.

133

ANIMAL BIOLOGY

Any batrachian may easily be passed around the class after placing
it in a tumbler with gauze or net tied over top. It should be kept in a
box with two inches of moist earth on the bottom. If no live insects
are obtainable for feeding a toad, bits of moist meat may be dangled
from the end of a string. If tadpoles are placed in a pool -or tub in a
garden, the toads hatched will soon make destructive garden insects
become a rarity.

Does a frog or a salamander have the more primitive
form of body ? Why do you think so ? Salamanders are
sometimes called mud puppies. The absurd belief that
salamanders are poisonous is to be classed with the belief
that toads cause warts. The belief among the ancients
that salamanders ate fire arose perhaps from seeing them
coming away from fires that had been built over their
holes on river banks by travelers. Their moist skin pro-
tected them until the fire became very hot.

Describe the "mud puppy" shown in Fig. 262. In the
West the pouched gopher, or rat (Fig. 371), is sometimes
absurdly called a salamander.

FIG. 262. BLIND SALAMANDER (Proteus anguinus). x . Found in caves and
underground streams in Balkans. Gills external, tail finlike, legs small.

CHAPTER XII

REPTILIA (REPTILES)

THIS class is divided into four orders which have such
marked differences of external form that there is no diffi-
culty in distinguishing them. These orders are represented
by Lizards, Snakes, Turtles, and Alligators. Of these, only
the forms of lizards and alligators have similar propor-
tions, but there is a marked difference in their size,
lizards being, in general, the smallest, and alligators the
largest of the reptiles.

Comparison of Lizards and Salamanders. - -To make clear
the difference between reptiles and batrachians, it will be
well to compare the orders in the two classes which re-
semble each other in size and shape ; namely, lizards and

- v> <-=-

FIG. 263. A SALAMANDER. FIG. 264. A LIZARD.

salamanders (Figs. 263 and 264). State in a tabular form
their differences in skin, toe, manner of breathing, develop-
ment from egg, sliape of tail, habitat, habits. Each has
an elongated body, two pairs of limbs, and a long tail, yet
they are easily distinguished. Are the differences sug-
gested above valid for the other batrachians (frogs) and
other reptiles (e.g. turtles) ? Trace the same differences

139

140

ANIMAL BIOLOGY

between the toad or frog (Fig. 250) and the "horned
toad," which is a lizard (Fig. 265),

FIG. 265. --"HORNED TOAD" LIZARD, of the Southwest
(Phrynosoma cornita). x.

STUDY OF A TURTLE OR TORTOISE

SUGGESTIONS. - - Because of the ease with which a tortoise or
turtle may be caught and their movements and habits studied, it is
suggested that one of these be studied as an example of reptiles.
Besides a live specimen, a skeleton of one species and the shells of
several species should be available.

^''/.r k\: . fi

1^*-^ tf$ ft -. ;-RW?i

"')/%. ^M^f<v1

p^

FIG. 266. EUROPEAN POND TURTLE (Emys lutario). (After Brehms.)

The body (of a turtle or tortoise) is divided distinctly into
regions (Fig. 266). Is there a head ? Neck ? Trunk ?
Tail ? The trunk is inclosed by the so-called shell, which

REPTILIA 141

consists of an upper portion, the carapace, and a lower
portion, the plastron. How are the other regions covered ?
What is the shape of the head ? Is the mouth at the
front, or on the under side ? Where are the nostrils ?
Are the motions of breathing visible ? Is there a beak or
snout ? Do the jaws contain teeth ?

Do the eyes project? Which is thinner and more
movable, the upper or lower lid ? Identify the third eye-
lid (nictitating membrane). It is translucent and comes
from, and is drawn into, the inner corner of the eye. It
cleanses the eyeball. Frogs and birds have a similar
membrane. The circular ear drum is in a depression back
of the angle of the mouth. What other animal studied
has an external ear drum ?

The tortoise has a longer, more flexible neck than any
other reptile. Why does it have the greatest need for
such a neck ? Is the skin over the neck tight or loose ?

Why ?

Do the legs have the three joints or parts found on the
limbs of most vertebrates ? How is the skin of the legs
covered? Do the toes have claws? Compare the front
and hind feet. Does the tortoise slide its body or lift it
when walking on hard ground ? Lay the animal on its
back on a chair or table at one side of the room in view
of the class. Watch its attempts to right itself. Are
the motions suited to accomplish the object ? Does the
tortoise succeed ?

What are the prevailing colors of turtles ? How does
their coloration correspond to their surroundings ?

What parts of the tortoise extend at times beyond the
shell ? Are any of these parts visible when the shell is
closed? \Vhat movements of the shell take place as it is
closed ? Is the carapace rigid throughout ? Is the plastron ?

142

ANIMAL BIOLOGY

The Skeleton (Fig. 267). - The carapace is covered with
thin epidermal plates which belong to the skin. The bony
nature of the carapace is
seen when the plates are
removed, or if its inner
surface is viewed (Fig.
267). It is seen to con-
sist largely of wide ribs
(how many ?) much flat-
tened and grown together
at their edges. The ribs
are seen to be rigidly at-
tached to the vertebrae.
The rear projections of
the vertebrae are flattened

FIG. 267. SKELETON OF EUROPEAN
TORTOISE.

C, rib plates; M, marginal plates; B, plastron;
H, humerus bone; R, radius; U, ulna;
fe, femur.

into a series of bony plates

which take the place of

the sharp ridge found

along the backs of most

vertebrates. Show that the shell
of a turtle is not homologous with
the shells of mollusks. Does the
turtle have shoulder blades and
collar bones ? Hip bones ? Thigh
bones ? Shin bone (fibia) and splint
bone (fibula)? (Fig. 267.)

Do the plates formed by the ribs
extend to the edge of the cara-
pace ? See Fig. 267. About how
many bony plates form the cara-
pace ? The plastron ? Do the
horny plates outside correspond

two branches of aorta. Compare i 11 i

with Fig. 269 and colored Fig. 2 . to the bony plates of the shell ?

FIG. 268. THREE-CHAM-
BERED HEART OF A REP-
TILE (tortoise).

a, veins; b,f, right and left auri-
cles; eg, ventricle; if, arteries to
lungs; e, veins from lungs; z", ,

REPTILIA

143

FIG. 269. PLAN OF REP-
TILIAN CIRCULATION.
See arrows.

How many axial plates ? How many costal (rib) plates ?

How many border plates? Which plates are largest?

Smallest ? Do the horny plates

overlap like shingles, or meet edge

to edge ? Is there any mark where

they meet on the bony shell ?

Basing it upon foregoing facts,

give a connected and complete de-
scription of the structure of the

carapace. Compare the skeleton

of the turtle with that of the snake,

and correlate the differences in

structure with differences in habits.
Draw the tortoise seen from the

side or above, with its shell closed, showing the arrange-
ment of the plates.

Place soft or tender vegetable
food, lettuce, mushroom, roots, ber-
ries, and water, also meat, in reach
of the turtle. What does it pre-
fer ? How does it eat ? It has no
lips ; how does it drink ?

Study the movements of its eye-
balls and eyelids, and the respira-
tory and other movements already
mentioned. State a reason for
thinking that no species of land
animals exists that lacks the sim-
ple power of righting itself when

turned on its back.
FIG. 270. REPTILIAN VIS-
CERA (lizard) . Tortoise, Turtle, Terrapin. The

fr, windpipe; h, heart ; hi, lungs; turtles belong tO the Order of
Ir, liver; ma, stomach; dd,
md, intestines ; hb, bladder. tllCS Called ClieLOHianS. No

144

ANIMAL BIOLOGY

can have any difficulty in knowing a member of this order.
The subdivision of the order into families is not so easy,
however, and the popular attempts to classify chelonians
as turtles, tortoises, and terrapins have not been entirely
successful. Species with a vaulted shell and imperfectly
webbed toes and strictly terrestrial habits are called tor-
toises. Species with flattened shells and strictly aquatic
habits should be called terrapins {e.g. mud terrapin). They
have three instead of two joints in the middle toe of each
foot. The term turtle may be applied to species which are
partly terrestrial and partly aquatic (e.g. snapping turtle
(Fig. 271)). - Usage, however, is by no means uniform.

FIG. 271. SNAPPING TURTLE (Chefydra serpentina).

Most reptiles eat animal food ; green terrapins and some
land tortoises eat vegetable food. Would you judge that
carnivorous chelonians catch very active prey ?

The fierce snapping turtle, found in ponds and streams,
sometimes has a body three feet long. Its head and tail
are very large and cannot be withdrawn into the shell.
It is carnivorous and has great strength of jaw. It has
been known to snap a large stick in two. The box tortoise
is yellowish brown with blotches of yellow, and like its
close kinsman, the pond turtle of Europe (Fig. 266), with-
draws itself and closes its shell completely. Both lids of the
plastron are movable, a peculiarity belonging to these two
species. The giant tortoise of the Galapagos Islands, ac-

REPTILIA

145

cording to Lyddeker, can trot cheerfully along with three
full-grown men on its back. " Tortoise shell ' used for
combs and other articles is obtained from the overlapping
scales of the hawkbill turtle, common in the West Indies.
The diamond-back terrapin, found along the Atlantic Coast
from Massachusetts to Texas, is prized for making soup.

: \ : :

^

"'r^

^Mg; / *^c

^ _:' . .^^v.^ *

~?^\w-'^s-'--'s^&&---**

.H?***/ 1 . "

m

FIG. 272. A RATTLESNAKE.

Venomous snakes of United
States named in order of virulence :
i. Coral snakes, Elaps, about sev-
enteen red bands bordered with yel-
low and black (colored figure 6)
(fatal). 2. Rattlesnakes (seldom
fatal). 3. Copperhead (may kill
a small animal size of dog).

4. Water moccasin (never fatal).

5. Ground rattler.- -Effects: Pulse
fast, breathing slow, blood tubes
dilated, blood becomes stored in ab-
dominal blood tubes, stupefaction

FIG. 2730. HEAD OF
VIPER, showing typical
triangular shape of head
of venomous snake.

FIG. 273 b. SIDE VIEW,
showing poison fangs ; also
tongue (forked, harmless) .

FIG. 274. VIPER'S HEAD,
showing poison sac at
base of fangs.

FIG. 275. SKULL, showing
teeth, fangs, and quadrate
bone to which lower jaw
is joined. See Fig. 284.

146

ANIMAL BIOLOGY

and death from blood being withdrawn from brain. Al-
ways two punctures, the closer together the smaller the
snake. Remedies: Ligature between wound and heart,
lance wound and suck; inject into wound three drops of i
per cent solution of chromic acid or potassium perman-
ganate. Give strychnine, hypodermically, until strychnine
symptoms (twitchings) appear. If symptoms of collapse
recur, repeat dose. Digitalin or caffein acts like strych-
nine ; alcohol has opposite effect.

Protective Coloration and Mimicry. When an animal
imitates the color or form of its inanimate surroundings it

is said to be protectively col-
ored or formed. Give an
instance of protective col-
oration or form among
lizards ; butterflies ; grass-
hoppers; amphibians; echi-
noderms. When an animal imitates the color or form of
another animal it is said to mimic the animal. Mimicry
usually enables an animal to deceive
enemies into mistaking it for an ani-
mal which for some reason they avoid.
The milkweed butterfly has a taste
that is repulsive to birds. The vice-
roy butterfly is palatable to birds, but
it is left untouched because of its
close resemblance to the repulsive
milkweed butterfly. The harlequin
snake (Flaps) of the Gulf states is the
only deadly snake of North America
(Figs. 277, 278). It is very strikingly colored with rings of
scarlet, yellow, and black. This is an example of warning
coloration. The coral snake (Lampropeltis) has bands of

FIG. 276. " GLASS SNAKE," a lizard
without legs.

FIG. 277. SKULL OF

ELAPS. See colored

Fig- 5-

FIG. 278. = SKULL OF
LAMPROPELTIS.

COLORED FIGURES i, 2. 3. CIRCULATION IN FISH, REPTILE, MAMMAL.

In which is blood from heart all impure ? Mixed ? Both pure and rnpure ?

FIG. 4. ANATOMY OF CARP. For description see Fig. 220, page 117.

FIG. 5. --HARLEQUIN SXAKE (Elapse.

THE HARMLESS

CORAL SNAKE

MIMICS THE

DEADLY HARLEQUIN

SNAKE.

FIG. 6. CORAL SNAKE (Lampropeltis).

REPTILIA

147

scarlet, yellow, and black (colored Fig. 6) of the same tints,
and it is hardly distinguishable from the harlequin. The

FIG. 279. GILA MONSTER (Heloderma suspectum), of Arizona. Ifpoisonous.it
is the only instance among lizards. It is heavy-built, orange and black mottled,
and about 16 inches long. Compare it with the green lizard (Fig. 280).

coral snake is said to mimic the
imitates the quiet inoffensive hab-
its of the harlequin snake, which
fortunately does not strike except
under the greatest provocation.
The rattles of the less poisonous
and seldom fatal rattlesnake
(Fig. 272) may be classed as an
example of warning sound which
most animals are quick to heed
and thus avoid encounters which
might be destructive to either the
snake or its enemy.

Survival of the Fittest. The two
facts of most far-reaching importance
in the history of animals and plants
are : ( i ) Heredity ; animals inherit
the characteristics of their parents.
(2) Variation; animals are not ex-
actly like their parents. The first
fact gives stability, the second makes

harlequin snake. It also

I
I

FIG. 280. CHAMELEON (Ano-
lis), or green lizard of south-
ern U.S. Far excels European
chameleon (Fig. 281) and all
known animals in power of
changing color (green, gray,
yellow, bronze, and black).

148

ANIMAL BIOLOGY

FIG. 281. CHAMELEON OF SOUTHERN EUROPE.

progress or evolution possible. The climate of the world is slowly
changing, and animals must change to adapt themselves to it. A
more sudden change of environment (surroundings) of animals
occurs because of migration or isolation ; these in turn are caused

by the crowding of
other animals or by
the formation or dis-
appearance of geo-
graphical barriers,
such as deserts, water,
mountain chains.

The young vary in
many ways from their
parents. Some have
a more protective color
or form, sharper claws,
swifter movements, etc. The individuals possessing such bene-
ficial variations live longer and leave more offspring, and because
of heredity transmit the desirable qualities to
some of their young. Variations which are dis-
advantageous for getting food, defense, etc., cause
shorter life and fewer offspring. Thus the fittest
survive, the unfit perish ; an automatic natural
selection occurs.

Darwin taught that variations are infinitesimal
and gradual. Recent experiments and observa-
tions seem to show that many variations are by
sudden jumps, somewhat resembling so-called
" freaks of nature." As to whether these " sports,"
or individuals with new peculiarities, survive,
depends upon their fitness for their environ- p IG- 2 g 2- _ j? M _
ment. "Survival of the fittest" results from this
natural selection, but the selection occurs be-
tween animals of marked, not infinitesimal, dif-
ferences, as Darwin taught. Darwin's theory is
probably true for species in the usual state of nature ; the new
theory (of De Vries) is probably true for animals and plants under
domestication and during rapid geographical changes.

BRYO OF A
TURTLE, show-
ing four gill slits.
(Challenger Re-
port.)

REP T ILIA

149

Table for Review (for notebooks or blackboards).

FISH

TADPOLE

FROG

TURTLE

LIZARD

Limbs, kind and
number

Are claws present ?
How many ?

Covering of body

Teeth, kind of, if
present

Which bones found
inman are lacking?

.

Chambers of heart

Respiration

Movements

*m$.&~*7& -",/'< "-

m^mp

-^ i 4

, I , I' , ' Al >

FIG. 283. BiG-HEADED TURTLE {Platy sternum megalocephalmri). x |. China.
This and Fig. 282 suggest descent of turtles from a lizardlike form. Figure 282
shows earlier ancestors to have been gill breathers.

CHAPTER XIII
BIRDS

SUGGESTIONS. The domestic pigeon, the fowl, and the English
sparrow are most commonly within the reach of students. The
last bird has become a pest and is almost the only bird whose
destruction is desirable. The female is somewhat uniformly mot-
tled with gray and brown in fine markings. The male has a black
throat with the other markings of black, brown, and white, in
stronger contrast than the marking of the female. As the different
species of birds are essentially alike in structural features, the direc-
tions and questions may be used with any bird at hand. When
studying feathers, one or more should be provided for each pupil
in the class. The feet and bills of birds should be kept for study.

Does the body of the bird, like the toad and turtle, have

a head, trunk, tail, and two pairs
of limbs ? Do the fore and hind
limbs differ from each other more or
less than the limbs of other backboned
animals ? Does any other vertebrate use
them for \ purposes as widely different ?

Eye. *\ Does the eyeball have parts corresponding
to the eyeball of a fish or frog; viz., cornea, iris, pupil?
Which is more movable, the upper or lower eyelid? Are
there any lashes ? The bird (like what other animal?) has
a third eyelid, or nictitating membrane. Compare its
thickness with that of the other lids. Is it drawn over
the eyeball from the inner or outer corner of the eye ?
Can you see in the human eye any wrinkle or growth
which might be regarded as remains, or vestige, of such a
membrane ?

BIRDS I 5 i

How many nostrils? In which mandible are they
located ? Are they nearer the tip or the base of the
mandible ? (Fig. 284.) What is their shape ? Do the nasal
passages go directly down through the mandible or do they
go backward ? Is the inner nasal opening into the mouth
or into the throat ?

The beak or bill consists of the upper and lower man-
dibles. The outside of the beak seems to be of what kind
of material ? Examine the decapitated head of a fowl or of
a dissected bird, and find
if there is a covering on
the bill which can be cut
or scraped off. Is the
mass of the bill of bony
or horny material ? With
what part of the human
head are the mandibles FlG - *8 4 .- SKULL OF DOMESTIC FOWL.

, , D /T7* o ' ("four-sided") bone by which lower

nOmolOgOUS r (r Ig. 284.) j aw is Cached to skull (wanting in beasts, pres-

EarS. DO birds have ent in reptiles; seeFig. 277 ).

external ears ? Is there an external opening leading to the
ear ? In searching for it, blow or push forward the feath-
ers. If found, notice its location, size, shape, and what
surrounds the opening. There is an owl spoken of as the
long-eared owl. Are its ears long ?

The leg has three divisions: the uppermost is the thigh
(called the "second joint" in a fowl); the middle division
is the shank (or "dr-um stick"); and the lowest, which is
the slender bone covered with scales, is formed by the
union of the ankle and instep. (The bones of the three
divisions are named the femur, tibiotarsus, and tarsometa-
tarsus.) The foot consists entirely of toes, the bones of
which are called phalanges. Is there a bone in each claw ?
(See Fig. 285.) Supply the numerals in this sentence:

152

ANIMAL BIOLOGY

The pigeon has - - toes, the

hind toe having joints;

of the three front toes, the
inner has joints (count
the claw as one joint), the

FIG. 286. SKELETON OF BIRD.

Rh, vertebrae; Cl, clavicle; Co, coracoid; Sc, scap-
ula; St, sternum; H, humerus; R, radius; U,
ulna; P, thumb; Fe, femur; T, tibia. See Fig. 394.

Questions : Which is the stiflest portion of the
vertebral column ? How are the ribs braced against
each other ? Which is longer, thigh bone or shin ?
Compare shoulder blade with man's (Fig. 399) . Which
is the extra shoulder bone ? Compare tail vertebrae
with those of extinct bird, Fig. 290.

FIG. 285. LEG BONES
OF BIRD.

middle has

joints, and the

outer toe has

joints (Fig. 285).
Is the thigh of a bird bare or
feathered? The shin ? The
ankle ? Where is the ankle
joint of a bird ? Do
you see the remains
of another bone (the
splint bone, or fibula)
on the shin bone of
the shank? (Fig. 285
or 286.) Why would
several joints in the
ankle be a disadvan

tage to a bird ?

BIRDS

153

The thigh hardly projects beyond the skin of the trunk,
as may be noticed in a plucked fowl. The thigh extends
forward from the hip joint (Figs. 286, 299) in order to bring
the point of support forward under the center of weight.
Why are long front toes more necessary than long hind toes ?
As the bird must often bring its head to the ground, the
hip joints are near the dorsal surface and the body swings
between the two points of support somewhat like a silver
ice pitcher on its two pivots. Hence stooping, which makes
a man so unsteady, does not cause a bird to lose steadiness.

The wing has three divisions which correspond to the
upper arm, forearm, and hand of man (Fig. 286). When
the wing is folded, the three divisions lie close alongside
each other. Fold your arm in the same manner. The
similarity of the bones of the first and second divisions to
the bones of our upper arm and forearm is very obvious
(Fig. 286). Ex-
plain. The hand of
a bird is furnished
with only three dig-
its (Fig. 287). The
three palm bones
(metacarpals) are
firmly united (Fig.
287). This gives
firmness to the
stroke in flying.

That the bird is
descended from ani-
mals which had the
fingers and palm bones less firmly united is shown by
comparing the hands of a chick and of an adult fowl
(Figs. 287, 288). The wrist also solidifies with age, the

DG.I

MC.I

F T0 . 287. HAND AND WRIST OF FOWL
(after Parker).

DG. 1-3, digits; MC. 1-3, metacarpals;
CC. 3, wrist.

2MD.DIGT

FIG. 288. HAND, WRIST (c\ FOREARM, AND
ELBOW OF YOUNG CHICK (after Parker).

154

ANIMAL BIOLOGY

FIG. 289. BREAST-
BONE AND SHOUL-
DER BONES OF
CASSOWARY.

five carpals of the chick being reduced to two in the fowl
(Figs. 287, 288). The thumb or first digit has a separate

covering of skin from the other digits, as
may be seen in a plucked bird. The de-
generate hand of the fowl is of course
useless as a hand (what serves in its
place ?) but is well fitted for firm support
of the feathers in flying. The two bones
of the forearm are also firmly joined.
There are eighteen movable joints in our
arm and hand ; the bird has only the three
joints which enable it to fold its wing.
The wrist joint is the joint in the forward angle of the wing.

Since the fore limbs are taken up with loco-
motion, the grasping function has been as-
sumed by the jaws. How does their
shape adapt them to this use ? For
the same reason the neck of a bird
surpasses the necks of all other ani-
mals in what respect? Is the trunk
of a bird
flexible or
inflexible?
There is
thus a cor-
relation between struc-
ture of neck and trunk.
Explain. The same
correlation is found in
which of the reptiles ?
(Why does rigidity of
trunk require flexibility

Question: Find two resemblances to reptiles in
Of neck?) Why does this extinct bird absent from skeletons of extant birds.

FIG. 290. A FOSSIL BIRD (archceopteryx)
found in the rocks of a former geological
epoch.

BIRDS

155

the length of neck in birds correlate with the length of
legs? Examples? (See Figs. 314, 315, 332.) Exceptions?
(Fig. 324.) Why does a swan or a goose have a long
neck, though its legs are short ?

To make a firm support for the wings the vertebrae of
the back are immovably joined, also there are three bones
in each shoulder, the collar bone,
the shoulder blade, and the
coracoid bone (Fig. 286). The
collar bones are united (why ?)
and form the " wishbone ' or

' pulling bone." To furnish sur-
face for the attachment of the
large flying muscles there is a
prominent ridge or keel on the
breastbone (Fig. 286). It is
lacking in most birds which do
not fly (Fig. 289).

The feathers are perhaps the
most characteristic feature of
birds. The large feathers of the
wings and tail are called quill
feathers. A quill feather (Fig.
291) is seen to consist of two
parts, the shaft , or supporting
axis, and the broad vane or web.
What part of the shaft is round ? Hollow ? Solid ? Is
the shaft straight ? Are the sides of the vane usually
equal in width ? Can you tell by looking at a quill whether
it belongs to the wing or tail, and which wing or which
side of the tail it comes from ? Do the quills overlap
with the wide side of the vane above or beneath the next
feather ? Can you cause two parts of the vane to unite again

FIG. 291. QUILL FEATHER.

D, downy portion.

i 5 6

ANIMAL BIOLOGY

by pressing together the two sides of a split in the vane ?
Does the web separate at the same place when pulled until

it splits again ?

The hollow part of the
shaft of a quill feather is
called the quill. The part
of the shaft bearing the
vane is called the rachis
(ra-kis). The vane consists
of slender barbs which are
branches of the shaft (II,
Fig. 292). As the name
indicates (see dictionary), a
barb resembles a hair. The
barbs in turn bear second-
ary branches called bar-
bides, and these again have
shorter branches called bar-
bicels (III, Fig. 292). These are sometimes bent in the
form of hooklets (Fig. 292, III), and the booklets of
neighboring barbules interlock, giv-
ing firmness to the vane. When two
barbules are split apart, and then re-
united by stroking the vane between
the thumb and finger, the union may
be so strong that a pull upon the vane
will cause it to split in a new place
next time.

There are four kinds of feathers,

(1) the quill feathers, just studied ;

(2) the contour feathers (I, Fig. 292),

which form the general surface of the body and give it its
outlines ; (3) the downy feathers (Fig. 293), abundant on

FIG. 292.--!, CONTOUR FEATHER.

II, III, PARTS OF QUILL FEATHER,

enlarged.

-Sh.

FIG. 293. A DOWN
FEATHER, enlarged.

BIRDS

157

nestlings and found among the contour feathers of the
adult but not showing on the surface ; (4) the pin feathers,
which are hair-like, and which are removed from a plucked
bird by singeing. The contour feathers are similar in
structure to the quill feathers. They protect the body
from blows, overlap so as to shed the rain, and, with the
aid of the downy feathers retain the heat, thus accounting
for the high temperature of the bird. The downy feathers
are soft and fluffy, as they possess few or no barbicels ;
sometimes they lack the rachis (Fig. 293). The pin feath-
ers are delicate horny shafts, greatly resembling hairs, but
they may have a tuft of barbs at the ends.

A feather grows from a small projection (or papilla) found
at the bottom of a depression of the skin. The quill is
formed by being molded around the papilla. Do you see
any opening at the tip of the quill for blood vessels to enter
and nourish the feather ? What is in the quill ? (Fig. 291.)
The rachis ? A young con-
tour or quill feather is in-
closed in a delicate sheath
which is cast off when the
feather has been formed.
Have you seen the sheath
incasing a young feather in
a molting bird ?

There are considerable
areas or tracts on a bird's
skin without contour feath-
ers. Such bare tracts are
found along the ridge of the breast and on the sides of
the neck. However, the contour feathers lie so as to over-
lap and cover the whole body perfectly (Fig. 294).

The shedding of the feathers is called molting. Feathers,

FIG. 294. DORSAL AND VENTRAL
VIE\V OF PLUCKED BIRD, showing
regions where feathers grow.

158

ANIMAL BIOLOGY

like the leaves of trees, are delicate structures and lose

perfect condition with age. Hence the annual renewal

of the feathers is
an advantage. Most
birds shed twice a
year, and with many
the summer plum-
age is brighter col-
ored than the winter
plumage. When a
feather is shed on
one side, the corre-
sponding feather on
the other side is

always shed with it. (What need for this ?) A large

oil gland is easily found on the

dorsal side of the tail. How does

the bird apply the oil to the

feathers ?

FIG. 295. WING OF BIRD.

/, false quills (on thumb) ; 2, primaries; 5, secondaries;
tertiaries (dark) are one above another at right;
a, b t coverts.

A

FIG. 296.

A t point dividing primaries from second-
aries; B, coverts.

In describing and classifying
birds, it is necessary to know the
names of the various external
regions of the body and plum-
age, These may be learned by
studying Figs. 295, 296, 297, 298.

FIG. 297. CEDAR WAXWING,
with regions of body marked.

S, forehead; Sc, crown (with crest);
Hh, nape; K, throat; Br, breast;
Ba, lower parts; R, back; Rt, tail;
B, tail coverts; P, shoulder feathers
(scapulars) ; T, wing coverts; HS,
primaries; AS, secondaries; A I,
thumb feathers.

The quills on the hand

BIRDS

159

are called primaries, those on the forearm are the sec-
ondaries, those on the upper arm are the tertiaries. Those
on the tail are called the tail quills. The feathers at the
base of the quills are called the coverts. The thumb bears
one or more quills called the spurious quills. Is the wing
concave on the lower or upper
side ? What advantage is this
when the bird is at rest ? When
it is flying ?

Control of Flight. - - Did you ever
see a bird sitting on a swinging
limb ? What was its chief means
of balancing itself ? When flying,
what does a bird do to direct its
course upward ? Downward ? Is
the body level when it turns to
either side? Birds with long,
pointed wings excel in what respect ? Examples ? Birds
with great wing surface excel in what kind of flight ? Ex-
amples. Name a common bird with short wings which
has a labored, whirring flight. Is its tail large or small ?

Does it avoid obstacles and direct its
flight well ? Why or why not ? When
a boat is to be turned to the right,
must the rudder be pulled to the right
or the left ? (The rudder drags in
the water and thus pulls the boat
around.) When the bird wishes to

FIG. 299. POSITION OF g O upward, must its tail be turned up

LIMBS OF PIGEON. ..

or down ? How when it wishes to go

down ? When a buzzard soars for an hour without flapping
its wings, does it move at a uniform rate ? For what does
it use the momentum gained when going with the wind ?

FIG. 298. PLAN OF BIRD.

s, center of gravity.

i6o

ANIMAL BIOLOGY

Flying. When studying the quill feathers of the wing,
you saw that the wider side of the vane is beneath the
feather next behind it. During the downward stroke of
the wing this side of the vane is pressed by the air against

m

FIG. 300.

a, clambering foot of chimney sweep; b, climbing foot of woodpecker; c, perching foot of
thrush; d, seizing foot of hawk; e, scratching foot of pheasant ; f, stalking foot of king-
fisher; g, running foot of ostrich; 7t, wading foot of heron; i, paddling foot of gull;
k, swimming foot of duck; /, steering foot of cormorant; m, diving foot of grebe; n, skim-
ming foot of coot. Question: Does any bird use its foot as a hand? (Fig. 320.)

the feather above it and the air cannot pass through the
wing. As the wing is raised the vanes separate and
the air passes through. The convex upper surface of
the wing also prevents the wing from catching air as
it is raised. Spread a wing and blow strongly against

BIRDS

161

its lower surface ; its upper surface. What effects are
noticed ?

Study the scales on the leg of a bird (Fig. 300). Why is
the leg scaly rather than feathered from the ankle down-
ward ? Which scales are largest? (Fig. 300.) How do
the scales on the front and back differ ? What can you
say of the scales at the bottom of the foot ; at the joints
of the toes ? Explain. How does the covering of the
nails and bill compare in color, texture, hardness and firm-
ness of attachment with the scales of the leg ?

Draw an outline of the bird seen from the side. Make
drawings of the head and feet
more detailed and on a larger
scale.

Why does a goose have more
feathers suitable for making pil-
lows than a fowl ? In what
country did the domestic fowl
originate? (Encyclopedia.) Why
does a cock crow for day ?
(Consider animal life in jungle.)

Activities of a Bird. Observe
a bird eating. Does it seem to
chew or break its food before
swallowing ? Does it have to
lift its head in order to swallow
food ? To swallow drink ? W 7 hy
is there a difference ? After feed-
ing the bird, can you feel the
food in the crop, or enlargement
of the gullet at the base of the
neck ? (Fig. 304.)

Feel and look for any move-

M

FIG. 301. AN ALTRICAL BIRD,
i.e. poorly developed at hatch-
ing. Young pigeon, naked,
beak too weak for eating.

FIG. 302. A PRECOCIAL BIRD
(well developed at hatching).
Feathered, able to run and to
pick up food. Precocity is a
sign of instinctive life and low
intelligence. A baby is not pre-
cocious.

Question: Is pigeon or fowl ex-
posed to more dangers in infancy ?

l62

ANIMAL BIOLOGY

ments in breathing. Can you find how often it breathes
per minute ? Place hand under the bird's wing. What
do you think of its temperature ; or better, what tempera-
ture is shown by a thermometer held under its wing ? Do
you see any connection between the breathing rate and the
temperature ? Test (as with the crayfish) whether a bird
can see behind its head ? Notice the movements of the
nictitating membrane. Does it appear to be transparent ?
Watch a bird fly around a closed room and review the
questions on Control of Flight.

Bend a bird's leg and see if it has any effect upon its
toes. Notice a bird (especially a large fowl) walk to see
if it bends its toes as the foot is lifted. Pull the rear
tendon in a foot cut from a fowl for the kitchen. Does
the bird have to use muscular exertion to grasp a stick
upon which it sits ? Why, or why not ? When is this
bending of the toes by bending the legs of special ad-
vantage to a hawk ? To a duck ? A wading bird ? Why
is a fowl safe from a hawk if it stands close to a tree ?

Do you see any signs of teeth in the bird's jaws? Why
are duck's " teeth ' (so called by children) not teeth ?

Can the tongue of a bird be
pulled forward ? (Fig. 303.)
What is its shape ? If there
is opportunity, dissect and
study the slender, bony
(hyoid) apparatus to which
the base of the tongue is
attached (Fig. 303), the open-
ing of the windpipe, or
trachea, the slit-like opening
of windpipe which is so narrow as to prevent food falling
into the windpipe.

...f

FIG. 303. HEAD OF WOODPECKER.

c, tongue; a, b, d, hyoid bone; e, g, wind-
pipe; f, salivary gland.

BIRDS

I6 3

The Internal Organs, or Viscera (Figs. 304 and 305).
The viscera (vis'se-ra), as in most vertebrates, include
the food tube ancl its glands; the lungs, the heart, and
larger blood vessels; the kidneys and bladder and the
reproductive organs. The lower part, or gullet, is en-
larged into a crop. It is largest in grain-eating birds. It

M

FIG. 304. ANATOMY OF DOVE x%.

bk, keel of breastbone; G, g, brain; lr,
windpipe; In, lung; h. heart; sr, gul-
let; k, crop; dr, glandular stomach;
mm, gizzard; d, intestine; , kidney;
hi, ureter; eil, openings of ureter and
egg duct into cloaca, kl.

FIG. 305. FOOD TUBE OF BIRD.

P, pancreas; C, caeca.

Question: Identify each part by means
of Fig. 304.

is found in the V-shaped depression at the angle of the
wishbone, just before the food tube enters the thorax.
The food is stored and softened in the crop. From the
crop the food passes at intervals into the glandular stomach.
Close to this is the muscular stomach, or gizzard. Are the
places of entrance and exit on opposite sides of the gizzard,
or near together ? (Fig. 304.) Is the lining of the gizzard

164

ANIMAL BIOLOGY

rough or smooth? Why? Is the gizzard tough or weak?
Why are small stones in the gizzard ? Why do not hawks
and other birds of prey need a muscular gizzard ? The
liver and pancreas empty their secretions into the intestines
by several ducts a little way beyond the gizzard. Beyond
the mouths of two caeca (Fig. 305) the many-coiled

intestine empties into the straight
rectum, which terminates in a
widened part called the cloaca.
Not only the intestine, but the
two ureters of the urinary system
and the two genital ducts of the
reproductive system all empty into
the cloaca (Figs. 304, 305).

The lungs have their rear sur-
faces attached to the spinal
column and ribs (/;/, Fig. 304).
They are connected with thin-
walled, transparent air sacs which
aid in purifying the blood. When
inflated with warm air, they prob-
ably make the body of the bird
more buoyant. For the names,
location, and shape of several
pairs of air sacs, see Fig. 306.
The connection of the air sacs with
hollows in the humerus bones is also shown in the figure.
Many of the bones are hollow ; this adds to the buoyancy of
the bird. The pulmonary artery, as in man, takes dark
blood to the lungs to exchange its carbon dioxide for
oxygen. Of two animals of the same weight, which ex-
pends more energy, the one that flies, or the one that runs
the same distance ? Does a bird require more oxygen

FIG. 306. POSITION OF LUNGS
AND AIR SACS (Pigeon).

TV, windpipe; P, lungs; Lm, sac
under clavicle with prolongation
(Lh} into humerus; La, sacs in
abdomen.

BIRDS

I6 5

FIG. 307. POSITION OF VOCAL
CORDS (str) OF MAMMAL AND BIRD.

Question : Does a fowl ever croak after
its head and part of its neck are cut off?
Explain.

or less, in proportion to its weight, than an animal that
lives on the ground ? Are the vocal cords of a bird
higher or lower in the wind-
pipe than those of a man?

(Fig. 307-)

The heart of a bird, like a
man's heart, has four cham-
bers ; hence it keeps the
purified blood separate from
the impure blood. Since
pure blood reaches the or-
gans of a bird, oxidation is
more perfect than in the
body of any animals yet
studied. Birds have higher
temperature than any other class of animals whatsoever.
Tell how the jaws, tail, and wings of the fossil bird
Archaeopteryx differed from living birds (Fig. 290).

SUGGESTIONS. In the field work, besides seeking the answers to
definite questions, pupils may be required to hand in a record of the
places and times of seeing a certain number of birds (20 to 40), with
the actions and features which made each distinguishable. Also, and
more important, each pupil should hand in a record of a careful and
thorough outdoor study of one common species (see below) as regards
habits, nesting, relation to environment, etc.

Field Study of a Common Species. (For written report.)
Name of species. Haunts. Method of locomotion when not
flying. Flying (rate, sailing, accompanying sound if any, soaring) .

What is the food? How obtained? Association with birds of
its own species. Relation to birds of other species.

Where does it build its nest? Why is such a situation selected?
Of what is the nest built? How is the material carried, and
how built into the nest? Does the bird's body fill the nest?

Describe the eggs. Does the male bird ever sit or otherwise
assist female before hatching? Does it assist after hatching?

1 66

ANIMAL BIOLOGY

How long is taken to lay
a sitting of eggs? How
long before the birds are
hatched? When hatched
are they helpless? Blind?
Feathered? (Figs. 301,
302.) Do the nest-
lings require much food ?
How many times is food
brought in an hour?
How distributed? Even
if the old birds some-
times eat fruit do they
take fruit to the young?
What do they feed to the
young? How long be-

FIG. 308. EUROPEAN TOMTIT'S NEST.
What are the advantages of its shape ?

fore they leave the nest?
Do the parents try to teach
them to fly? Do the par-
ents care for them after the
nest is left ? What songs or
calls has the bird?

General Field Study.
{For written report.} Name
the best and poorest flyers
you know ; birds that fly
most of the time ; birds that
seldom fly. Observe birds
that pair ; live in flocks.
Does their sociability vary
with the season? Do you
ever see birds quarreling?

gag

FIG. 309. TAILOR BIRD'S NEST (India).

Instinct for nest building highly perfected.

BIRDS

167

Fighting? What birds do you observe whipping or driving birds
larger than themselves? Which parent do young birds most re-
semble ? Name the purposes for which birds sing. Which senses
are very acute? Why? Dull? Why? Can you test your state-
ments by experiment? A partridge usually sits with 18 to 24
eggs in nest. About how long after laying first egg before sitting
begins? Do several partridge hens lay in the same nest?

Haunts. Name some birds that are found most often in
the following localities : about our homes, in gardens and or-
chards, fields and meadows,
in bushes, in the woods,
in secluded woods, around
streams of water, in thick-
ets, in pine woods.

Size. - - Name birds as
large as a robin or larger,
nearly as large, half as large,
much smaller.

Colors. - - Which sex is
more brilliant? What ad-
vantage are bright colors to
one sex? What advantage
are dull colors to the other FlG ' 3i HOUSE WREN.

sex? Which have yellow breasts, red patch on heads, red or
chestnut breasts, blue backs, black all over?

Habits. Name the birds that walk, jump, swim, live in flocks,
-sing while flying, fly in undulations, in circles, have labored flight.

Such books as Wright's "Birdcraft" (Macmillan, N. Y.), Clark's
"Birds of Lakeside and Prairie" (Mumford, Chicago), and Pear-
son's "Stories of Bird Life" (B. F. Johnson, Richmond), will be
of great help. The last book is delightfully written, and is one of
the few treating of bird life in the South.

Economic Importance of Birds. Farmers find their
most valuable allies in the class aves, as birds are the dead-
liest enemies of insects and gnawing animals. To the in-
numerable robbers which devastate our fields and gardens,
nature opposes the army of birds. They are less numerous

1 68

ANIMAL BIOLOGY

ifv< .

V" '~ . " : " 'iOLS 'ff,'*"^,! " ^v'
$',',' 'i 1 ' ^ ~ ' ,/ ,'' '' 4' >TT * -' : X- <C'.' "'- ' "*

<?/:>4f, 7 ' "S^r' ; 'v5t,v ;$- r ;.!' V'v'>

im-''.' r^m^' ^-V'.

ppf//'

FIG. 311. SCREECH OWL {Megascops asio).

Question: Compare posture of body," position of
eyes, and size of eyes, with other birds.

than insects and other
robbers, it is true, but
they are skillful and
zealous in pursuit, keen
of eye, quick, active,
and remarkably vora-
cious. The purely in-
sectivorous birds are
the most useful, but the
omnivorous and grami-
nivorous birds do not
disdain insects. The
perchcrs and the wood-
peckers should be pro-
tected most ca

(and those of the day to a less degree) are very destructive
to field mice, rabbits, and other
gnawing animals. Some igno-
rant farmers complain continu-
ally about the harm done by
birds. To destroy them is as
unwise as it would be to destroy
the skin which protects the hu-
man body because it has a spot
upon it! It cannot be repeated
too plainly that to hunt useful
birds is a wrong and mischievous
act, and it is stupid and barba-
rous to destroy their nests.

Injurious birds are few. Of

course birds which are the ene-

FIG. 312. GOSHAWK,

mies of other birds are enemies or chicken hawk.

BIRDS

169

%

-,J .-_ -v\ ' .

- ' ' '

^1^. X. \,\l >

FIG. 313. ROAD RUNNER, or chaparral bird (Tex. to Cal.). What order?

(Key, p. 177.)

of mankind, but examples are scarce (some owls and
hawks). Many birds of prey are classed thus by mistake.
Sparrow hawks, for instance, do not eat birds except in
rare instances ; they feed chiefly upon insects. A sparrow
hawk often keeps watch over a field where grasshoppers
are plentiful and destroys great numbers of them. When
a bird is killed because it is supposed to be injurious, the
crop should always be examined, and its contents will often
surprise those who are sure it is a harmful bird. The
writer once found two frogs, three grasshoppers, and five
beetles that had been swallowed by a " chicken hawk '
killed by an irate farmer, but no sign of birds having been
used for food. Fowls should not be raised in open places,
but among trees and bushes, where hawks cannot swoop.
Birds which live exclusively upon fish are, of course,
opposed to human interests. Pigeons are destructive to
grain ; eagles feed chiefly upon other birds.

If the birds eat the grapes, do not kill the birds, but plant
more grapes. People with two or three fruit trees or a small

170

ANIMAL BIOLOGY

garden are the only ones that lose a noticeable amount of
food. We cut down the forests from which the birds ob-
tain part of their food. We destroy insect pests at great
cost of spraying, etc. The commission the birds charge
for such work is very small indeed. (See pages 177-183.)

FlG. 314. WOOD DUCK, male (Aix sponsa). Nests in hollow trees throughout
North America. Also called summer duck in South. Why ?

The English sparrow is one bird of which no good word
may be said. Among birds, it holds the place held by rats
among beasts. It is crafty, quarrelsome, thieving, and a
nuisance. It was imported in 1852 to eat moths. The
results show how ignorant we are of animal life, and how
slow we should be to tamper with the arrangements of
nature. In Southern cities it produces five or six broods
each year with four to six young in each brood. (Notice
what it feeds its young.) It fights, competes with and
drives away our native useful birds. It also eats grain and
preys upon gardens. They have multiplied more in Aus-

BIRDS 171

tralia and the United States than in Europe, because they
left behind them their native enemies and their new ene-
mies (crows, jays, shrikes, etc.) have not yet developed, to
a sufficient extent, the habit of preying upon them. Nature
will, perhaps, after a long time, restore the equilibrium
destroyed by presumptuous man.

Protection of Birds.--:. Leave as many trees and bushes
standing as possible. Plant trees, encourage bushes.

2. Do not keep a cat. A mouse trap is more useful than
a cat. A tax should be imposed upon owners of cats.

3. Make a bird house and place on a pole ; remove
bark from pole that cats may not climb it, or put a broad
band of tin around the pole.

4. Scatter food in winter. In dry regions and in hot
weather keep a shallow tin vessel containing water on the
roof of an outhouse, or out-of-the-way place for shy birds.

5. Do not wear feathers obtained by the killing of birds.
What feathers are not so obtained ?

6. Report all violators of laws for protection of birds.

7. Destroy English sparrows.

Migration. - - Many birds, in fact most birds, migrate to
warmer climates to spend the winter. Naturalists were

once content to speak of the migra-
tion of birds as a wonderful instinct,

and made no attempt
to explain it. As
birds have the warmest covering
of all animals, the winter mi-
gration is not for the pur-

FIG. 315. -GREAT BLUE HERON, pose of escaping the cold; it
in flight, balancing with legs. is pro b a bly to escape starva-
tion, because in cold countries food is largely hidden by
snow in winter. On the other hand, if the birds remained

1 72

ANIMAL BIOLOGY

in the warm countries in summer, the food found in north-
ern countries in summer would be unused, while they
would have to compete with the numerous tropical birds
for food, and they and their eggs would be in danger from
snakes, wild cats, and other beasts of prey so numerous in
warm climates. These are the best reasons so far given
for migration.

The manner and methods of migration have been studied
more carefully in Europe than in America. Migration is

m

FIG. 316. EUROPEAN SWALLOWS (Hirundo urbicd), assembling for autumn

flight to South.

not a blind, infallible instinct, but the route is learned and
taught by the old birds to the young ones ; they go in
flocks to keep from losing the way (Fig. 316); the oldest
and strongest birds guide the flocks (Fig. 317). The birds
which lose their way are young ones of the last brood, or
mothers that turn aside to look for their strayed young.
The adult males seldom lose their way unless scattered
by a storm. Birds are sometimes caught in storms or
join flocks of another species and arrive in countries
unsuited for them, and perish. For example, a sea or

BIRDS 1 73

marsh bird would die of hunger on arriving in a very dry
country.

The landmarks of the route are mountains, rivers, valleys,
and coast lines. This knowledge is handed down from one
generation to another. It includes the location of certain
places on the route where food is plentiful and the birds
can rest in security. Siebohm and others have studied

the routes of migration in the Old
World. The route from
the nesting places in
northern Eu-

Africa fol- JT ^S^SL ^ ... r P e to

lows the Rhine,
the Lake of Geneva,
the Rhone, whence some spe-
cies follow the Italian and others the Span- Fl( , CRANES
ish coast line to Africa. Birds choose the MIGRATING, with

, . r-r,, . , , ATr , , leader at point of

lowest mountain passes. The Old World v-shaped line
martin travels every year from the North
Cape to the Cape of Good Hope and back again ! An-
other route has been traced from Egypt along the coast
of Asia Minor, the Black Sea and Ural Mts. to Siberia.
Field Study of Migration. Three columns may be filled
on the blackboard in an unused corner, taking several
months in spring or fall for the work. First column, birds
that stay all the year. Second column, birds that come
from the south and are seen in the summer only. Third
column, birds that come from the north and are seen in
winter only. Exact dates of arrival and departure and
flight overhead should be recorded in notebooks. Many
such records will enable American zoologists to trace the
migration routes of our birds. Reports may be sent to the
chief of the Biological Survey, Washington, D.C,

174

ANIMAL BIOLOGY

Molting. - How do birds arrange their feathers after
they have been ruffled ? Do they ever bathe in water?

FIG. 318. APTERYX, of New Zealand. Size of a hen, wings and tail

rudimentary, feathers hair-like.

In dust ? Dust helps to remove old oil. At what season
are birds brightest feathered ? Why ? Have you ever seen

FIG. 319. GOLDEN, SILVER, AND NOBLE PHEASANTS, males. Order?
(Key, p. 177.) Ornaments of males, brightest in season of courtship, are due to
sexual selection (Figs. 321-7-9, 333).

evidence of the molting of birds ? Describe the molting
process (page 120).

BIRDS

175

FIG. 320.
COCKATOO.

Adaptations for
Flying. Flight
is the most diffi-
cult and energy-
consuming meth-
od of moving
found among ani-
mals, and care-
ful adjustment is
necessary. For
balancing, the
heaviest muscles
are placed at the
lower and central
portion of the body.
These are the flying
muscles, and in some
birds (humming birds)
they make half of the
entire weight. Teeth
are the densest of ani-
mal structures ; teeth
and the strong chew-
ing muscles required
would make the head
heavy and balancing
difficult ; hence the chewing apparatus is
transferred to the heavy gizzard near the
center of gravity of the body. The bird's
neck is long and excels all other necks in
flexibility, but it is very slender (although
apparently heavy), being inclosed in a
loose, feathered skin. A cone is the best -]-.

^ \

.

FIG. 321. BIRD OF
PARADISE (Asia).

ANIMAL BIOLOGY

shape to enable the body to penetrate the air, and a small
neck would destroy the conical form. The internal organs
are compactly arranged and rest in the cavity of the breast
bone. The bellows-like air sacs filled with warm air
lighten the bird's weight. The bones are hollow and very
thin. The large tail quills are used by the bird only in
guiding its flight up and down, or balancing on a limb.

The feet also aid a
flying bird in bal-
ancing. The wing
is so constructed as
to present to the
air a remarkably

large surface com-
pared with the
small bony support
in the wing skele-
ton. Are tubes
ever resorted to by

FIG. 322. HERRING GULL. (Order?)

human architects when lightness combined with strength
is desired ? Which quills in the wing serve to lengthen
it? (Fig. 296.) To broaden it? Is flight more difficult
for a bird or a butterfly ? Which of them do the flying
machines more closely resemble ? Can any bird fly for a
long time without flapping its wings ?

Exercise in the Use of the Key. Copy this list and write the name
of the order to which each of the birds belongs. (Key, page 177.)

Cockatoo (Fig. 320)
Sacred Ibis (Fig. 328)
Screech Owl ( Fig. 311)
Nightingale (Fig. 325)
Top-knot Quail (Fig.

329)

Wren (Fig. 310)
Apteryx (Fig. 318)
Lyre bird (Fig. 327)
Road Runner (Fig. 3 1 3)
Ostrich (Fig. 332)
Penguin (Fig. 330)

Pheasant (Fig. 319)
Wood Duck (Fig. 314)
Jacana (Fig. 324)
Sea Gull (Fig. 322)
Heron (Fig. 315)
Hawk (Fig. 312)

BIRDS

177

KEY, OR TABLE, FOR CLASSIFYING BIRDS (Class Aves)

INTO ORDERS

ORDERS

Aj Wings not suited for flight, 2 or 3 toes
A 2 Wings suited for flight (except the penguin)
Bj Toes united by a web for sii'iiriming, legs short
Cj Feet placed far back ; wings short, tip not

reaching to base of tail (Fig. 300)
C, Bill flattened, horny plates under margin

of upper bill (Fig. 323)
C 3 Wings long and pointed, bill slender
C 4 All four toes webbed, bare sac under

throat

B 2 Toes not united by web for swimming
Cj Three front toes, neck and legs long, tibia

(shin, or " drumstick ") partly bare
Co Three front toes, neck and legs not long
D! Claws short and blunt (e, Fig. 300)
E t Feet and beak stout, young feathered,

base of hind toe elevated
E 2 Feet and beak weak, young naked
Do Claws long, curved and sharp, bill

hooked and sharp
D 3 Claws long, slightly curved, bill nearly

straight

C 3 Two front and two hind toes (Fig. 300)
Dj Bill straight, feet used for climbing
D l Bill hooked, 'both bill and feet used for
climbing

RUNNERS

DIVERS
BILL-STRAINERS

SEA-FLIERS
GORGERS

WADERS

SCRATCHERS

MESSENGERS
ROBBERS

PERCHERS

FOOT-CLIMBERS
BILL-CLIMBERS

The Food of Birds. Extracts from Bulletin No. 54
(United States Dept. of Agriculture), by F. E. L. Beal.

The practical value of birds in controlling insect pests should
be more generally recognized. It may be an easy matter to
exterminate the birds in an orchard or grain field, but it is an
extremely difficult one to control the insect pests. It is certain,
too, that the value of our native sparrows as weed destroyers is
not appreciated. Weed seed forms an important item of the
winter food of many of these birds, and it is impossible to estimate
the immense numbers of noxious weeds which are thus annually

N

ANIMAL BIOLOGY

destroyed. If crows or blackbirds are seen in numbers about

j

cornfields, or it woodpeckers are noticed at work in an orchard,

it is perhaps not surprising that they
are accused of doing harm. Careful in-
vestigation, however, often shows that
they are actually destroying noxious in-
sects ; arid also that even those which
do harm at one season may compensate
for it by eating insect pests at another.
Insects are eaten at all times by the
majority of land birds. During the

breeding season most kinds subsist largely on this food, and rear

their young exclusively upon it.

Partridges.- - Speaking of 13 birds which he shot, Dr. Judd says :

These 13 had taken weed seed to the extent of 63 per cent of

FIG. 323. HEAD OF DUCK.

FIG. 324. JACANA. (Mexico, Southwest Texas, and Florida.)
Questions: What appears to be the use of such long toes? What peculiarity of wing? head?

their food. Thirty-eight per cent was ragweed, 2 per cent tick
trefoil, partridge pea, and locust seeds, and 23 per cent seeds of
miscellaneous weeds. About 14 per cent of the quail's food for

BIRDS

179

the year consists of animal matter (insects and their allies).
Prominent among these are the Colorado potato beetle, the
striped squash beetle, the cottonboll-weevil, grasshoppers. As a
weed destroyer the quail has few, if any, superiors. Moreover,
its habits are such that it is almost constantly on the ground,
where it is brought in close contact with both weed seeds and
ground-living insects. It is a good ranger, and, if undisturbed, will
patrol every day all the fields in its vicinity as it searches for food.

v * ' -

. ;

FIG. 325. NIGHTINGALE, > *. FIG. 326. SKYLARK, x .

Two celebrated European songsters.

Doves.- -The food of the dove consists of seeds of weeds,
together with some grain. The examination of the contents of
237 stomachs shows that over 99 per cent of the food consists
wholly of vegetable matter.

Cuckoos. - - An examination of the stomachs of 46 black-billed
cuckoos, taken during the summer months, showed the remains
of 906 caterpillars, 44 beetles, 96 grasshoppers, 100 sawflies, 30
stink bugs, and 15 spiders. Of the yellow-billed cuckoos, or
" rain-crow," 109 stomachs collected from May to October, in-
clusive, were examined. The contents consisted of 1,865 cater ~
pillars, 93 beetles, 242 grasshoppers, 37 sawflies, 69 bugs, 6 flies,
and 86 spiders.

i8o

ANIMAL BIOLOGY

Woodpeckers. Careful observers have noticed that, excepting
a single species, these birds rarely leave any conspicuous mark on
a healthy tree, except when it is affected by wood-boring larvae,
which are accurately located, dis-
lodged, and devoured by the wood-
pecker. Of the flickers' or yellow-
hammers' stomachs examined, three
were completely filled with ants.
Two of the birds each
contained more than
3,000 ants, while the
third bird contained fully
5,000. These ants be-
long to species which
live in the ground. It is
these insects for which
the flicker is reaching
when it runs about in the
grass. The yellow-bellied
woodpecker or sapsucker
(Sphyrapicus varius) was shown to be guilty of pecking holes in
the bark of various forest trees, and sometimes in that of apple

trees, and of drinking the
sap when the pits became
filled. It has been proved,
however, that besides tak-
ing the sap the bird cap-
tures large numbers of
insects which are attracted
by the sweet fluid, and
that these form a very
considerable portion of

its diet. The woodpeck-
ers seem the only agents
FIG. 328. -SACRED IBIS. (Order?) which can success f u n y

cope with certain insect enemies of the forests, and, to some
extent, with those of fruit trees also. For this reason, if for no
other, they should be protected in every possible way.

FIG. 327. LYRE BIRD, male.

BIRDS

181

The night hawk, or "bull bat," may be seen most often soaring
high in air in the afternoon or early evening. It nests upon rocks or
bare knolls and flat city roofs. Its food consists of insects taken
on the wing ; and so greedy is the bird that when food is plentiful,
it fills its stomach almost to bursting. Ants (except workers) have
wings and fly as they are preparing to propagate. In destroying
ants night hawks rank next to, or even with, the woodpeckers, the
acknowledged ant-eaters among birds.

FIG. 329. --TOP-KNOT QUAIL, or California Partridge.
(West Texas to California.)

The kingbird, or martin, is largely insectivorous. In an ex-
amination of 62 stomachs of this bird, great care was taken to
identify every insect or fragment that had any resemblance to a
honeybee ; as a result, 30 honeybees were identified, of which 29
were males or drones and i was a worker.

Blue Jay. - - In an investigation of the food of the blue jay 300
stomachs were examined, which showed that animal matter com-
prised 24 per cent and vegetable matter 76 per cent of the bird's
diet. The jay's favorite food is mast (i.e. acorns, chestnuts,
chinquapins, etc.), which was found in 200 of the 300 stomachs,
and amounted to more than 42 per cent of the whole food.

182

ANIMAL BIOLOGY

FIG. 330. PENGUIN OF PATA-
GONIA. Wings used as flip-
pers for swimming.

Crow. That he does pull up sprouting corn, destroy chickens,
and rob the nests of small birds has been repeatedly proved. Nor
are these all of his sins. He is known to eat frogs, toads, sala-
manders, and some small snakes, all
harmless creatures that do some good
by eating insects. Experience has
shown that they may be prevented
from pulling up young corn by tarring
the seed, which not only saves the
corn but forces them to turn their at-
tention to insects. May beetles, " dor-
bugs," or June bugs, and others of
the same family constitute the princi-
pal food during spring and early sum-
mer, and are fed to the young in
immense quantities.

Ricebird. The annual loss to rice
growers on account of bobolinks has
been estimated at $2,000,000.

Meadow Lark. --Next to grasshop-
pers, beetles make up the most impor-
tant item of the meadow lark's food,
amounting to nearly 21 per cent.
May is the month when the dreaded
cut-worm begins its deadly career, and
then the lark does some of its best
work. Most of these caterpillars are
ground feeders, and are overlooked
FIG. 331. Umbrella holding by birds which habitually frequent

trees, but the meadow lark finds and
devours them bv thousands.

j

Sparrows. - - Examination of many stomachs shows that in
winter the tree sparrow feeds entirely upon seeds of weeds.
Probably each bird consumes about one fourth of an ounce a
day. Farther south the tree sparrow is replaced in winter by the
white-throated sparrow, the white-crowned sparrow, the fox spar-
row, the song sparrow, the field sparrow, and several others ; so
that all over the land a vast number of these seed eaters are at

the nests of social weaver
bird of Africa; polygamous.

BIRDS

183

work during the colder months reducing next year's crop of worse
than useless plants.

Robin. --An examination of 500 stomachs shows that over
42 per cent of its food is animal matter, principally insects,
while the remainder is made up largely of small fruits or
berries. Vegetable food forms nearly 58 per cent of the stom-
ach contents, over 47 per cent being wild fruits, and only a
little more than 4 per cent being possibly cultivated varieties.
Cultivated fruit amounting to about 25 per cent was found
in the stomachs in June and July, but only a trifle in August.
Wild fruit, on the contrary, is eaten in every
month, and constitutes during half the year a
staple food.

Questions. - - Which of these birds are com-
mon in your neighborhood? Which of them
according to the foregoing report are plainly inju-
rious? Clearly beneficial? Doubtful? Which
are great destroyers
of weed seeds?
Wood-borers? Ants?
Grain? Why is the

j

destruction of an ant
by a night hawk of
greater benefit than
the destruction of an
ant by a woodpecker ?
Name the only wood-
pecker that injures
trees. If a bird eats
two ounces of grain
and one ounce of in-
sects, has it probably
done more good or
more evil? F IG- 332. AFRICAN OSTRICH, x 5 V (Order?)

r-

CHAPTER XIV

MAMMALS (BEASTS AND MAN)

SUGGESTIONS. - -A tame rabbit, a house cat, or a pet squirrel may
be taken to the school and observed by the class. Domestic ani-
mals may be observed at home and on the street. A study of the
teeth will give a key to the life of the animal, and the teacher
should collect a few mammalian skulls as opportunities offer. The
pupils should be required to identify them by means of the chart
of skulls (p. 194). If some enthusiastic students fond of anatomy
should dissect small mammals, the specimens should be killed with
chloroform, and the directions for dissection usual in laboratory
works on this subject may be followed. There is a brief guide on
page 223. The following outline for the study of a live mammal
will apply almost as well to the rabbit or squirrel as to the cat.

The Cat.- The house cat (Fe/is domesticd) is probably
descended from the Nubian v&\.(Felis maniculata t Fig. 333)
found in Africa. The wild species is about half again as
large as the domestic cat, grayish brown with darker
stripes ; the tail has dark rings. The lynx, or wild cat
of America {Lynx rufus\ is quite different. Compare the
figures (333, 335) and state three obvious differences.
To which American species is the house cat closer akin,
the lynx (Fig. 335) or the ocelot (Fig. 334)? The domes-
tic cat is found among all nations of the world. What is
concluded, as to its nearest relatives, from the fact that the
Indians had no cats when America was discovered ? It
was considered sacred by the ancient Egyptians, and after
death its body was embalmed.

The body of the cat is very flexible. It may be divided
into five regions, the head, neck, trunk, tail, and limbs. Its

184

MAMMALS

185

/

FIG. 333. WILD CAT OK AFRICA (Felis maniculatd), x %.

eyes have the same parts as the eyes of other mammals.
Which part of its eye is most peculiar? (Fig. 333.) What
part is lacking that is present in birds ? How are the eyes
especially adapted for seeing at night ? Does the pupil in
the light extend up or down or across the iris ? Does it
ever become round ?

What is the shape and position of the ears? Are they
large or small compared with those of most mammals ?
They are fitted best for catching sound from what direc-
tion ? What is thus indicated in regard to the cat's habits ?
(Compare with ears of rabbit.) Touch the whiskers of the
cat. What result ? Was it voluntary or involuntary mo-
tion ? Are the nostrils relatively large or small compared
with those of a cow ? Of man ?

Is the neck long or short ? Animals that have long fore
legs usually have what kind of a neck ? Those with short
legs ? Why ? How many toes on a fore foot ? Hind foot ?
Why is this arrangement better than the reverse ? Some
mammals are sole walkers (plantigrade), some are toe
walkers (digitigrade). To which kind does the cat

1 86

ANIMAL BIOLOGY

\ ' i i i^'-V- >V -'-""- ' '"' " ' '"' ,

V : ilSl

..ii ; ^' '.': LsirSstfytiaiii: ' : -\\ .

..

FIG. 334. OCELOT (Felis pardalis), of Texas and Mexico, x |.

belong ? Does it walk on the ends of the toes ? Does it
walk with all the joints of the toes on the ground ? Where
is the heel of the cat? (Fig. 334.) The wrist? To make
sure of the location of the wrist, begin above : find the shoul-
der blade, the upper arm (one or two bones ?), the lower
arm (one or two bones?), the wrist, the palm, and the
fingers (Fig. 337). Is the heel bone prominent or small?

In what direction does the knee of the cat point ? The
heel ? The elbow ? The wrist ? Compare the front and
hind leg in length; straightness ; heaviness; number and
position of toes ; sharpness of the claws. What makes the
dogs claivs duller than a cat's ? What differences in habit
go with this ? Judging from the toe that has become use-
less on the fore foot of the cat, which toe is lacking in the
hind foot ? Is it the cat's thumb or little finger that does
not touch the ground ? (Fig. 337.) Locate on your own
hand the parts corresponding to the pads on the forefoot
of a cat. Of what use are soft pads on a cat's foot ?

Some animals have short, soft fur and long, coarse over
hair. Does the cat have both ? Is the cat's fur soft or
coarse ? Does the fur have a color near the skin different

MAMMALS

I8 7

from that at the tip ? Why is hair better suited as a cover-
ing for the cat than feathers would be? Scales? Where
are long, stiff bristles found on the cat ? Their length
suggests that they would be of what use to a cat in going
through narrow places ? Why is it necessary for a cat to
be noiseless in its movements ?

-
^ - x

FIG. 335- LYNX

rufus). The " Bob-tailed cat" (North America).

Observe the movements of the cat.- -Why cannot a cat
come down a tall tree head foremost ? Did you ever see a
cat catch a bird? How does a cat approach its prey?
Name a jumping insect that has long hind legs; an am-
phibian; several mammals (Figs. 362, 374). Does a cat
ever trot ? Gallop ? Does a cat chase its prey ? When
does the cat move with its heel on the ground ? The
claws of a cat are withdrawn by means of a tendon (see
Fig. 338). Does a cat seize its prey with its mouth or its
feet ?

How does a cat make the purring sound ? (Do the lips
move ? The sides ?) How does a cat drink ? Do a cat

1 88

ANIMAL BIOLOGY

and dog drink exactly the same way ? Is the cat's tongue
rough or smooth ? How is the tongue used in getting the
flesh off close to the bone ? Can a cat clean a bone
entirely of meat?

In what state of development is a newly born kitten ?
With what does the cat nourisli its young f Name ten

animals of various kinds
whose young are simi-
larly nourished. What
is this class of ani-
mals called ?
Why does a

FIG. 336. JAGUAR, of tropical America.

cat bend its back
when it is frightened or
angry ? Does a cat or a dog eat a greater variety of food ?
Which refuses to eat an animal found dead ? Will either
bury food for future use ? Which is sometimes trouble-
some by digging holes in the garden ? Explain this in-
stinct. Which lived a solitary life when wild ? Which had
a definite haunt, or home ? Why are dogs more sociable
than cats? A dog is more devoted to his master. Why?
A cat is more de-
voted to its home,
and will return if
carried away. Why?
Why does a dog
turn around before
lying down ? (Con-
sider its original
environment.) FlG - 337- - SKELETON OF CAT.

The Skeleton (Fig. 337).- -Compare the spinal column
of a cat in form and flexibility with the spinal column of
a fish, a snake, and a bird.

MAMMALS 189

The skull is joined to the spinal column by two knobs
(or condyls\ which fit into sockets in the first vertebra.
Compare the jaws with those of a bird and a reptile.
There is a prominent ridge in the temple to which the
powerful chewing muscles are attached. There is also a
ridge at the back of the head where the muscles which
support the head are attached (Fig. 348).

Count the ribs. Are there more or fewer than in man ?
The breastbone is in a number of parts, joined, like the
vertebrae, by cartilages. Compare it with a bird's ster-
num ; why the difference ? The shoulder girdle, by which
the front legs are attached to the
trunk, is hardly to be called a gir-
dle, as the collar bones (clavicles)
are rudimentary. (They often es-
cape notice during dissection, being
hidden by muscles.) The shoulder

\ -*"

blades, the other bones of this gir-

die, are large, but relatively not so F ' G ; 338 ' ~ <r h LAW OF t CA *

J (i) retracted by ligament, and

broad toward the dorsal edge as (2) drawn down by muscle

i i ii 11 i r-pi , attached to lower tendon.

human shoulder blades. The clav-
icles are tiny because they are useless. Why does the cat
not need as movable a shoulder as a man ? The pelvic, or
hip girdle, to which the hind legs are attached, is a rigid
girdle, completed above by the spinal column, to which it
is immovably joined. Thus the powerful hind legs are
joined to the most rigid portion of the trunk.

Mammals. The cat belongs to the class Mammalia or
mammals. The characteristics of the class are that the
young are not hatched from eggs, but are born alive, and
nourished with milk (hence have lips), and the skin is
covered with hair. The milk glands are situated ventrally.
The position of the class in the animal kingdom was

ANIMAL BIOLOGY

shown when the cow was classified (p. 9). Their care for
the young, their intelligence, and their ability to survive
when in competition with other animals, causes the mam-
mals to be considered the highest class in the animal
kingdom.

According to these tests, what class of vertebrates should
rank next to mammals? Compare the heart, lungs, blood,
and parental devotion of these two highest classes of ani-
mals.

FIG. 339. SKELETON OF LION (cat family).

The first mammals, which were somewhat like small
opossums, appeared millions of years ago, when the world
was inhabited by giant reptiles. These reptiles occupied
the water, the land, and the air, and their great strength
and ferocity would have prevented the mammals from
multiplying (for at first they were small and weak), but
the mammals carried their young in a pouch until able to
care for themselves, while the reptiles laid eggs and left
them umcared for. The first mammals used reptilian eggs
for food, though they could not contend with the great
reptiles. Because birds and mammals are better parents
than reptiles, they have conquered the earth, and the rep-

MAMMALS

IQI

tiles have been forced into subordination, and have become
smaller and timid.

Classification of Mammals. - - Which two have the closest
resemblances in the following lists : Horse, cow, deer. Why ?
Cat, cow, bear. Why ? Monkey, man, sheep. Why ? Rat,
monkey, squirrel. Why? Giraffe, leopard, camel. Why?
Walrus, cat, cow. Why ?
Check the five mammals
in the following lists that
form a group resembling
eacJi other most closely :
Lion, bear, pig, dog, squir-
rel, cat, camel, tiger, man.

State your reasons. Gi- FIG. 340. WALRUS (Tnctieckusrosmarus).

raffe, leopard, deer, cow,
rat, camel, hyena, horse,
monkey. State reasons.
Teeth and toes are
the basis for subdividing
the class mammalia into
orders. Although the
breathing, circulation, and
internal organs and pro-
cesses are similar in all
mammals, the external

,1 -i FIG. 341. WEASEL, in summer ; in Canada

organs vary greatly be-
in winter it is all white but tip of tail.

cause of the varying en-
vironments of different species. The internal structure
enables us to place animals together which are essentially
alike ; e.g. the whale and man are both mammals, since
they resemble in breathing, circulation, and multiplication
of young. The external organs guide us in separating the
class into orders. The teeth vary according to the food

192

ANIMAL BIOLOGY

.f

FIG. 342. FOOT OF BEAR

(Plantigrade).

eaten. The feet vary according to use in obtaining food
or escaping ffom enemies. This will explain the differ-
ence in the length of legs of lion
and horse, and of the forms of
the teeth in cat and cow. Make
a careful study of the teeth and
limbs as shown in the figures and
in all specimens accessible. Write
out the dental formulas as indi-
cated at the top of page 194. The numerals above the line
show the number of upper teeth; those below the line
show the number of lower teeth in one half of the jaw.
They are designated as follows : /, incisors ; C, canine ;
M, molars. Multiplying by two gives the total number.
Which skulls in the chart have the largest canines ?
Why ? The smallest, or none at all ? Why ? Compare
the molars of the cow, the hog, and the dog. Explain
their differences. In which skulls are some of the molars
lacking ? Rudimentary ? Why are the teeth that do not
touch usually much smaller than those that do ?

-

;" ' - 1 --

?"- : " -S.uV's V .

- ..
-w iifc';':

'i

/

^',; '-' m X A
'^^U^.^ 1 ' 1 ^ ; ' >''/'' \N

s ; -"" X , .,&M,v; -.. ,.-. V I

>?Aa

FIG. 343. POLAR BEAR (Ursus maritimus).

MAMMALS

193

KEY, OR TABLE, FOR CLASSIFYING MAMMALS
(class Mammalia} INTO ORDERS

Imperfect Mammals, young hatched or pre-
maturely born

BI Jaws a birdlike beak, egg-laying
Bo Jaws not beaklike, young carried in pouch
A 2 Perfect Mammals, young not hatched, nor
prematurely born

Cj Front part of both jaws lack teeth

C 2 Teeth with sharp points for piercing

shells of insects
C 3 Canines very long, molars suited for

tearing
.C 4 Canines lacking, incisors very large

Digits
with
claws

B 2

Digits

not
distinct

Digits

with
nails
or
hoofs

C 1 Head large ; carnivorous
C 2 Head small ; herbivorous

C 1 Five toes, nose prolonged into a snout

C 9 Toes odd number, less than five

C 3 Toes even number, upper front teeth

lacking, chew the cud
C 4 Toes even number, upper front teeth

present, not cud-chewers
C- All limbs having hands
C 6 Two limbs having hands

ORDERS

Mon'otrentes
Marsu'pials

Eden 1 tales

Insect'ivors

Car'nivors
Rodents

Ceta'ceans
Sire'neans

Proboscideans

Equities

Ru' minants

Swine
Quad' rumans

Bf mans

Exercise in Classification. Copy the following list, and by refer-
ence to figures write the name of its order after each mammal : -

Ape (Figs. 405, 406) Cow (Figs. 344, 386) Antelope (Fig. 391)

Rabbit (Fig. 345)
Dog (Figs. 356, 408)
Hog (Figs. 357, 393)
Bat (Figs. 347, 370)
Cat (Figs. 337, 348)
Armadillo

(Figs. 349, 365)

Walrus (Fig. 340)
Monkey

(Figs. 352,401)
Horse

(Figs. 355, 395)
Ant-eater

Mole

(Figs. 367, 368)
Beaver

(Figs. 372, 373)
Duckbill (Fig. 359)
Tapir (Fig. 384)

(Figs. 354, 364) Dolphin (379, 397)

Use chart of skulls and Figs. 381, 382, 395-400 in working out this

exercise.

o

(194)

Chart of Mammalian Skulls (Illustrated Study)

Man's dental formula

is ( At >, C- , / - } = 32.
V 5 i /

In like manner fill out formulas below:

Cow (M C- - fY 2 = 32

Rabbit (M C I}' 2 = 28

Walrus (M C- - /~Y 2 = 34

Bat (M C / )2 = 34

Cat (M CIV- = 30

Armadillo (M C- - / )- = 28

Horse (M C / ) 2 = 40

Whale ( M C / )2 = o

Am. Monkey. . .(M C / )2 3 6

Sloth (M C I )2 = 18

Ant-eater (M C / )2 = o

Dog (M C--/Y 2 = 42

Hog (M- C / )2 = 44

Sheep (M C I )2= o 2

FlG. 344. Skull and front of lower jaw
of Cow.

FIG. 346. WALRUS (see Fig. 341).

FIG. 347. BAT.

FIG. 345. RABBIT.
, ^, incisors; C, molars.

FIG. 348. CAT.

Chart of Mammalian Skulls

(195)

FIG. 349. ARMADILLO.

FIG. 354. ANT-EATER (Fig. 364).

FIG. 350. HORSE
(front of jaw).

FIG. 351. GREENLAND
WHALE.

FlG - 355. HORSE.

FIG. 356. DOG. Upper (A) and lower (B) jaw.

FlG - 357- HOG.

FIG. 352. AMERICAN MONKEY.

FlG - 353- SLOTH (Fig. 363).

FIG. 358. SHEEP.

196

ANIMAL BIOLOGY

FlG. 359. DUCKBILL ( Ornith orhynchus paradoxus) .

The lowest order of mammals contains only two species,
the duckbill and the porcupine ant-eater, both living in

the Australian re-
gion. Do you judge
that the duckbill
of Tasmania -(Fig.
359) lives chiefly in
water or on land ?
Why? Is it prob-
ably active or slow in movement ? It dabbles in mud and
slime for worms and mussels, etc. How is it fitted for
doing this ? Which
feet are markedly
webbed ? How far
does the web extend ?
The web can be
folded back when not
in use. It lays two
eggs in a nest of
grass at the end of a
burrow. Trace re-
semblances and dif-
ferences between this
animal and birds.

The porcupine ant-
eater has numerous
quill-like spines (Fig.
360) interspersed with
its hairs. (Use ?) De-
scribe its claws. It
has a long prehensile
tongue. It rolls into a ball when attacked. Compare its
jaws with a bird's bill. It lays one egg, which is carried

FIG. 360. SPINY ANT-EATER (Echidna acu-
leata). View of under surface to show pouch.
(After Haacke.)

MAMMALS

197

in a fold of the skin until hatched. Since it is pouched
it could be classed with the pouched mammals (next order),
but it is egg-laying. Suppose the two animals in this
order did not nourish their young with milk after hatching,
would they most resemble mammals, birds, or reptiles ?

Write the name of this order. _ (See Table,

p. 193.) WJiy do you place them in this order (_ _)?
See p. 193.) The name of the order comes from two Greek

\\

FlG. 361. OPOSSUM (Didelphys Virginianus).

words meaning u one opening," because the ducts from
the bladder and egg glands unite with the large intestine
and form a cloaca. What other classes of vertebrates
are similar in this ?

Pouched Mammals.- These animals, like the last, are
numerous in the Australian region, but are also found in
South America, thus indicating that a bridge of land once
connected the two regions. The opossum is the only
species which has penetrated to North America (Fig. 361).
Are its jaws slender or short ? What kinship is thus sug-
gested ? As shown by its grinning, its lips are not well de-

198

ANIMAL BIOLOGY

veloped. Does this mean a low or a well-developed mam-
mal? Where does it have a thumb? (Fig. 361.) Does
the thumb have a nail ? Is the tail hairy or bare ? Why ?
Do you think it prefers the ground or the trees ? State
two reasons for your answer. It hides in a cave or bank
or hollow tree all day, and seeks food at night. Can it run
fast on the ground ? It feigns death when captured,

and watches for a
chance for stealthy
escape.

The kangaroo
(Fig. 362), like the
opossum, gives
birth to imperfectly
developed young.
(Kinship with what
classes is thus in-
dicated ?) After
birth, the young
(about three fourths
of an inch long)
are carried in a ventral pouch and suckled for seven or
eight months. They begin to reach down and nibble grass
before leaving the pouch. Compare fore legs with hind
legs, front half of body with last half. Describe tail.
What is it used for when kangaroo is at rest? In jump-
ing, would it be useful for propelling and also for balanc-
ing the body ? Describe hind and fore feet. Order _ _.
Why?. See key, page 193.

Imperfectly Toothed Mammals. - - These animals live
chiefly in South America (sloth, armadillo, giant ant-eater)
and Africa (pangolin). The sloth (Fig. 363) eats leaves.
Its movements are remarkably slow, and a vegetable growth

FIG. 362. GIANT KANGAROO.

MAMMALS

199

X . ' \ '

FIG. 363. SLOTH of South America.

resembling moss often gives its hair a green color. (What
advantage?) How many toes has it? How are its nails
suited to its man-
ner of living? Does
it save exertion by
hanging from the
branches of trees
instead of walking
upon them ?

Judging from the
figures (363, 364,
365), are the mem-
bers of this order
better suited for at-
tack, active resistance, passive resistance, or concealment

when contend-
ing with other
animals ? The
ant-eater's claws
(Fig. 364) on the
fore feet seem
to be a hin-
drance in walk-
ing ; for what
are they useful ?
Why are its jaws

so slender?
Jfi*K<^

H*

FIG. 364. GIANT ANT-EATER of South America.

(See Fig. 354.) Find evidences that the edentates are a the
degenerate order. Describe another ant-eater (Fig. 360).

What is prob-
ably the use of

enorniOUS
rail ?

nine-banded armadillo (Fig. 365) lives in Mexico and Texas.
It is omnivorous. To escape its enemies, it burrows into

2OO

ANIMAL BIOLOGY

the ground with surprising rapidity. If unable to escape
when pursued, its hard, stout tail and head are turned

under to protect
the lower side of
the body where
there are no scales.
The three-banded
species (Fig. 366)
lives in Argentina.
Compare the ears

FIG. 365. NINE-BANDED ARMADILLO of Texas
and Mexico. (Dasypus novemcinctus.') It is increas-

ing in numbers; it is very useful, as it digs up and
destroys insects. (See Fig. 347.)

and tail of the two
species ; give rea-
sons for differences. Why are the eyes so small ? The
claws so large ? Order _. WJiy?-

7;i%^jN _ |f

A/^rM'^: : \ ' ".^^s^i-l

m

FIG. 366. THREE-BANDED ARMADILLO (Tolypeutes tricinctus) .

Insect Eaters. - The soft interior and crusty covering of
insects makes it unnecessary for animals that prey upon
them to have flat-topped teeth for grinding them to

MAMMALS

2OI

powder, or long cusps for tearing them to pieces. The
teeth of insect eaters, even the molars (Fig. 368), have
many sharp tubercles, or points, for holding insects and
piercing the crusty outer skeleton and reducing it to bits.
As most insects dig in the ground or fly in the air, we
are not surprised to learn that some insect-eating mam-

FIG. 367. THE MOLE.

mals (the bats) fly and others (the moles) burrow. Are
the members of this order friends or competitors of man?

FIG. 368. SKELETON OF MOLE. (Shoulder blade is turned upward.)

Why does tJie mole have very small eyes ? Small ears ?
Compare the shape of the body of a mole and a rat.
What difference ? Why ? Compare the front and the hind
legs of a mole. Why are the hind legs so small and
weak ? Bearing in mind that the body must be arranged
for digging and using narrow tunnels, study the skeleton

202

ANIMAL BIOLOGY

(Fig. 368) in respect to the following : Bones of arm
(length and shape), fingers, claws, shoulder bones, breast-
bone (why with ridge like a bird ?), vertebrae (why are the
first two so large ?), skull (shape). There are no eye
sockets, but there is a snout gristle ; for the long, sensitive
snout must serve in place of the small and almost useless
eyes hidden deep in the fur. Is the fur sleek or rough ?
Why ? Close or thin ? It serves to keep the mole clean.
The muscles of neck, breast, and shoulders are very
strong. Why ? The mole eats earthworms as well as
insects. It injures plants by breaking and drying out
their roots. Experiments show that the Western mole will
eat moist grain, though it prefers insects. If a mole is
caught, repeat the experiment, making a careful record of
the food placed within its reach.

FIG. 369. SKELETON OF BAT.

As with the mole, the skeletal adaptations of tJie bat
are most remarkable in the hand. How many fingers ?
(Fig. 369.) How many nails on the hand ? Use of
nail when at rest? When creeping? (Fig. 369.) In-
stead of feathers, the flying organs are made of a pair
of extended folds of the skin supported by elongated
bones, which form a framework like the ribs of an um-
brella or a fan. How many digits are prolonged ? Does

MAMMALS

203

FIG. 370. VAMPIRE (Phyllostoma spectrum) of South America. : .

the fold of the skin extend to the hind legs ? The tail ?
Are the finger bones or the palm bones more prolonged
to form the wing skeleton ?

The skin of the wing is rich in blood vessels and nerves,
and serves, by its sensitiveness to the slightest current of
air, to guide the bat in the thickest darkness. Would you
judge that the bat has sharp sight ? Acute hearing?

The moles do not hibernate ; the bats do. Give the
reason for the difference. If bats are aroused out of a
trance-like condition in winter, they may die of starvation.
Why ? The mother bat carries the young about with her,
since, unlike birds, she has no nest. How are the young
nourished? Order. _. Why? _. (Key, p. 193.)

The Gnawing Mammals. These animals form the most
numerous order of mammals. They lack canine teeth. In-
ference ? The incisors are four in number in all species

204

ANIMAL BIOLOGY

except the rabbits, which have six (see Fig. 345). They
are readily recognized by their large incisors. These teeth
grow throughout life, and if they are not constantly worn

FlG. 371. POUCHED GOPHER (Geomys bursarius] X |, a large, burrowing
field rat, with cheek pouches for carrying grain.

away by gnawing upon hard food, they become incon-
veniently long, and may prevent closing of the mouth and
cause starvation. The hard enamel is all on the front sur-
face, the dentine in the rear being softer ; hence the in-
cisors sharpen themselves by use to a chisel-like edge.

FlG. 372. Hind foot a, fore foot b,
tail c, of BEAVER.

FIG. 373. BEAVER.

The molars are set close together and have their upper
surfaces level with each other. The ridges on them run
crosswise so as to form a continuous filelike surface for

MAMMALS

205

reducing the food still finer after it has been gnawed off
(Fig. 345). The lower jaw fits into grooves in place of
sockets. This allows the jaw to work back and forth in-
stead of sidewise. The rabbits and some squirrels have a
hare lip ; i.e. the upper lip is split. What advantage is
this in eating ? In England the species that burrow are
called rabbits ; those that do not are called hares.

Name six enemies of rabbits. Why does a rabbit usually
sit motionless unless approached very close ? Do you
usually see one before it dashes off ? A rabbit has from
three to five litters of from three to six young each year.
Squirrels have fewer and smaller
litters. Why must the rabbit
multiply more rapidly than the
squirrel in order to survive ?
English rabbits have increased
in Australia until they are a
plague. Sheep raising is inter-
fered with by the loss of grass.
The Australians now ship them to England in cold storage
for food. Rabbits and most rodents lead a watchful,
timid, and alert life. An exception is the porcupine,
which, because of the defense of its barbed quills, is dull
and sluggish.

The common rodents are :

FIG. 374. POSITION OF LIMBS
IN RABBIT.

porcupines

pouched gopher ground hog
prairie dog field mouse

prairie squirrel
guinea pig chipmunk

Which of the above rodents are commercially important ?
Which are injurious to an important degree ? Which have
long tails? Why? Short tails? Why? Long ears ? Why?

squirrels beavers
rabbits muskrats
rats
mice

2O6

ANIMAL BIOLOGY

Short ears ? Why ? Which are aquatic ? Which dig or bur-
row ? Which are largely nocturnal in habits ? Which are
arboreal ? Which are protected by coloration ? Which
escape by running ? By seeking holes ?

Economic Importance. - - Rabbits and squirrels destroy the
eggs and young of birds. Are rabbits useful ? Do they
destroy useful food ? The use of beaver and muskrat skins
as furs will probably soon lead to their extinction. Millions
of rabbits' skins are used annually, the hair being made into

FIG. 375. FLYING SQUIRREL (Pteromysvolucella). x V 4 .

felt hats. There are also millions of squirrel skins used
in the fur trade. The hairs of the tail are made into fine
paint brushes. The skins of common rats are used for the

thumbs of kid gloves. Order _. Why?

Elephants. - - Elephants, strange to say, have several
noteworthy resemblances to rodents. Like them, elephants
have no canine teeth ; their molar teeth are few, and marked
by transverse ridges and the incisors present are promi-
nently developed (Figs. 376, 3/7). Instead of four incisors,
however, they have only two, the enormous tusks, for there
are no incisors in the lower jaw. Elephants and rodents

MAMMALS

207

FIG. 376. HEAD OF AFRICAN ELEPHANT.

both subsist upon plant food. Both have peaceful disposi-
tions, but one order has found safety and ability to survive
by attaining enormous size and strength ; the other (e.g.
rats, squirrels) has found safety in small size. Explain.

Suppose you were
to observe an elephant
for the first time, with-
out knowing any of its
habits. How would
you know that it does
not eat meat ? That it
does eat plant food ?
That it can defend it-
self ? Why would you make the mistake of thinking that
it is very clumsy and stupid ? Why is its skin naked ?
Thick? Why must its legs be so straight? Why must it
have either a very long neck or a substitute for one ?
(Fig. 376.) Are the eyes large or small? The ears? The
brain cavity ? What anatomical feature correlates with
the long proboscis ? Is the proboscis a new organ not
found in other animals, or is it a specialization of one or
more old ones ? Reasons ? What senses are especially
active in the proboscis ? How is it used in drinking ? In

grasping ? What evidence that
it is a development of the
nose ? The upper lip ?

The tusks are of use in up-
rooting trees for their foliage
and in digging soft roots for
food. Can the elephant graze ? Why, or why not ? There
is a finger-like projection on the end of the snout which is
useful in delicate manipulations. The feet have pads to
prevent jarring ; the nails are short and hardly touch the
ground. Order. _. Why?. _. Key, page 193.

FIG. 377. MOLAR TOOTH OF
AFRICAN ELEPHANT.

208

ANIMAL BIOLOGY

Whales, Porpoises, Dolphins. - - As the absurd mistake
is sometimes made of confusing whales with fish, the pupil
may compare them in the following respects : eggs, nour-
ishment of young, fins, skin, eyes, size, breathing, tem-
perature, skeleton (Figs. 209, 379, and 397).

' H

*T

FIG. 378. HARPOONING GREENLAND WHALE
"(see Fig. 351).

Porpoises and dolphins, which are smaller species of
whales, live near the shore and eat fish. Explain the ex-
pression " blow like a porpoise." They do not exceed five
or eight feet in length, while the deep-sea whales are from
thirty to seventy-five feet in length, being by far the largest
animals in the world. The size of the elephant is limited
by the weight that the bones and muscles support and
move. The whale's size is not so limited.

The whale bears one young (rarely twins) at a time.
The mother carefully attends the young for a long time.
The blubber, or thick layer of fat beneath the skin, serves
to retain heat and keep the body up to the usual tempera-
ture of mammals in spite of the cold water. It also serves,
along with the immense lungs, to give lightness to the body.

MAMMALS

2O9

Why does a whale need large lungs ? The tail of a whale

_ __ _ is horizontal instead

1 ^J of vertical, that it may

steer upward rapidly
from the depths when
needing to breathe.
The teeth of some
FIG. 379. -DOLPHIN. whales do not cut the

gum, but are reabsorbed and are replaced by horny plates
of "whalebone," which act as strainers. Give evidence,
from the flippers, lungs, and other organs, that the whale
is descended from a land mammal (Fig. 397). Compare
the whale with a typical land mammal, as the dog, and
enumerate the specializations of the whale for living in
water. What change took place in the general form of the
body ? It is believed that on account of scarcity of food
the land ancestors of the whale, hundreds of thousands of
years ago, took to living upon fish, etc., and, gradually be-
coming swimmers and divers, lost the power of locomotion
on land. Order _ _ . Why ?

Elephants are rapidly becoming extinct because of the
value of their
ivory tusks.
Whales also
furnish valua-
ble products,
but they will
probably exist
much longer.
Why?

The manatees and dugongs (sea cows) are a closely re-
lated order living upon water plants, and hence living close
to shore and in the mouths of rivers. Order Why f_ _.

-. -' - -315
jj~

FIG. 380. MANATEE, or sea cow ; it lives near the shore
and eats seaweed. (Florida to Brazil.)

2IO

ANIMAL BIOLOGY

Hoofed Mammals.- -All the animals in this order walk
on the tips of their toes, which have been adapted to this
use by the claws having developed into hoofs. The order
is subdivided into the odd-toed (such as the horse with one
toe and the rhinoceros with three) and the even-toed (as
the ox with two toes and the pig with four). All the even-
toed forms except the pig and hippopotamus chew the cud
and are given the name of ruminants.

Horse and Man Compared (Figs. 381, 399). To which
finger and toe on man's hand and foot does the toe of a

horse's foot correspond ?
Has the horse kneecaps ?
Is its heel bone large or
small ? Is the fetlock on
toe, instep, or ankle ?
Does the part of a horse's
hind leg that is most elon-
gated correspond to the
thigh, calf, or foot in
man ? On the fore leg,
is the elongated part the
upper arm, forearm, or
hand ? Does the most
elongated part of the fore
foot correspond to the finger, palm, or wrist ? On the hind
foot is it toe, instep, or ankle ? Is the fetlock at the toe,
instep, or heel ? (Fig. 385.) Is the hock at the toe, in-
step, heel, or knee ? Order - WJiy ?

Specializations of the Mammals. The early mammals,
of which the present marsupials are believed to be typical,
had five toes provided with claws. They were not very
rapid in motion nor dangerous in fight, and probably ate
both animal and vegetable food.

FlG. 381. Left leg of man, left hind leg
of dog and horse ; homologous parts
lettered alike.

MAMMALS

211

*$-*. xs /
fil\u\\ ?a/>Afc\<

Miohippus

\J

Mcsottippus'

FIG. 382. SKELETONS OF FEET OF MAMMALS.

P, horse; D, dolphin; E, elephant; A, monkey; T, tiger; O, aurochs;

F, sloth ; M, mole.

Question: Explain how each is adapted to its specialized function.

According to the usual rule, they tended to u B
increase faster than the food supply, and there
were continual contests for food. Those whose
claws and teeth were sharper drove the others
from the food, or preyed upon them. Thus the
specialization into the bold flesh eating beasts
of prey and the timid vegetable feeders began.
Which of the flesh eaters has already been stud-
ied at length ? The insectivora escaped their
enemies and found food by learning to burrow
or fly. The rodents accomplished the same result either by
acquiring great agility in climbing, or by living in holes, or
by running. The proboscidians acquired enormous size
and strength. The hoofed animals found safety in flight.

FIG. 383.

Feet of the

ancestors of

the horse.

212

ANIMAL BIOLOGY

' i-)f * ..-''/ :-'-

;, ;-'-; |
''>

i ' ..

: '

\ , r - .,,

-. .

' '" - - ' - - *f

-- * - . '! -.. "

.;/* ;-,<,. . .,:,-.* ;..,v/-

$/.</ *&":&

FIG. 384. TAPIR OF SOUTH AMERICA {Tapirus americanus}. X ^5.
Questions: How does it resemble an elephant? (Fig. 376.) A horse ? (p. 210.)

Ungulates, as the horse, need no other protection than
their great speed, which is due to lengthening the bones of

the legs and rising
upon the very tip of
the largest toe, which,
to support the weight,
developed an enor-
mous toe-nail called a
hoof. The cattle, not
having developed such
speed as the horse,
usually have horns
for defense. If a calf
or cow bellows with distress, all the cattle in the neigh-
borhood rush to the rescue. This unselfish instinct to
help others was an aid to the survival of wild cattle living
in regions infested with beasts of prey. Which of ^Esop's
fables is based upon this instinct ? The habit of rapid
grazing and the correlated habit of chewing the cud were
also of great value, as it enabled cattle to obtain grass hur-

FlG. 385. HORSE, descended from a small
wild species still found in Western Asia.

MAMMALS

213

riedly and retire to a safe place to chew it. Rudiments of
the upper incisors are present in the jaw of the calf, show-
ing the descent from animals which had a complete set of
teeth. The rudiments are absorbed and the upper jaw of
the cow lacks incisors entirely, as they would be useless
because of the cow's habit of seizing the grass with her
rough tongue
and cutting it
with the lower
incisors as the
head is jerked
forward. This
is a more rapid
way of eating
than by biting.

AH 71 i FIG. 386. SKELETON OF Cow. Compare with horse

Which leaves

(Fig. 395) as to legs, toes, tail, mane, dewlap, ears, body.

the grass shorter

after grazing, a cow or a horse ? Why ? Grass is very
slow of digestion, and the ungulates have an alimentary
canal twenty to thirty times the length of the body.
Thorough chewing is necessary for such coarse food, and
the ungulates which chew the cud (ruminants) are able,
by leisurely and thorough chewing, to make the best use
of the woody fiber (cellulose) which is the chief substance
in their food.

Ruminants have four divisions to the stomach. Their
food is first swallowed into the roomy paunch in which,
as in the crop of a bird, the bulky food is temporarily
stored. It is not digested at all in the paunch, but after
being moistened, portions of it pass successively into the
honeycomb, which forms it into balls to be belched up and
ground by the large molars as the animal lies with eyes
half closed under the shade of a tree. It is then swal-

214

ANIMAL BIOLOGY

lowed a second time and is acted upon in the third divi-
sion (or manyplies) and the fourth division (or reed ). Next

FIG. 387. Food traced
through stomachs of
cow. (Follow arrows.)

FIG. 388. Section of cow's stomachs.
Identify each. (See text.)

it passes into the intestine. Why is the paunch the largest
compartment ? In the figure do you recognize the paunch
by its size ? The honeycomb by its lining ? Why is it

round ? The last two
of the four divisions
may be known by their
direct connection with
the intestine.

The true gastric juice
is secreted only in the
fourth stomach. Since
the cud or unchewed
food is belched up in
balls from the round
" honeycomb," and since
a ball of hair is some-
times found in the stom-
ach of ruminants, some
ignorant people make the absurd mistake of calling the
ball of hair the cud. This ball accumulates in the paunch

FIG. 389. OKAPI. This will probably prove
to be the last large mammal to be discovered
by civilized man. It was found in the for-
ests of the Kongo in 1900.

Questions: It shows affinities (find them) with
girafie, deer, and zebra. It is a ruminant ungulate
(explain meaning see text).

MAMMALS

215

because of the friendly custom cows have of combing each
other's hair with their rough tongues, the hair sometimes

FIG. 390. AFRICAN CAMEL (Camelus dromedarius) .

being swallowed. Explain the saying that if a cow stops
chewing the cud she will die.

Does a cow's lower jaw move sidewise or
back and forth ? Do the ridges on the molars
run sidewise or lengthwise ? Is a
cow's horn hollow ? Does it
have a bony core ? (Fig. 344.)

The permanent hol-
low horns of the cow
and the solid decidu-
ous horns of the deer
are typical of the two
kinds of horns pos-
sessed by ruminants.

The prong-horned an-

FIG. 391. PRONG-HORNED ANTELOPE
telope (Fig. 39 1) of (Antelocarpa Americana) . Western states.

2l6

ANIMAL BIOLOGY

the United States, however, is an intermediate form, as its
horns are hollow, but are shed each year. The hollow
horns are a modification of hair. Do solid or hollow
bones branch ? Which are possessed by both sexes ?
Which are pointed ? Which are better suited for fight-
ing ? Why would the deer have less need to fight than
the cattle ? Deer are polygamous, and the males use their

FIG. 392. ROCKY MOUNTAIN SHEEP (Ovis montana). x

5 .

horns mostly for fighting each other. The sharp hoofs of
deer are also dangerous weapons. The white-tail deer
(probably the same species as the Virginian red deer) is
the most widely distributed of the American deer. It
keeps to the lowlands, while the black-tailed deer prefers
a hilly country. The moose, like the deer, browses on
twigs and leaves. The elk, like cattle, eats grass.

The native sheep of America is the big horn, or Rocky
Mountain sheep (Fig. 392). The belief is false that they

MAMMALS

217

alight upon their horns when jumping down precipices.
They post sentinels and are very wary. There is also a
native goat, a white species, living high on the Rocky
Mountains near the snow. They are rather stupid ani-
mals. The bison once roamed in herds of countless thou-
sands, but, with the exception of a few protected in parks,
it is now extinct. Its shaggy hide was useful to man in
winter, so it has been well-nigh destroyed. For gain man
is led to exterminate elephants, seals, rodents, armadillos,
whales, birds, deer, mussels, lobsters, forests, etc.

FIG. 393. PECCARY (Dicofyles torquatus] of Texas and Mexico, x ^

Our only native hog is the peccary, found in Texas (Fig.
393). In contrast with the heavy domestic hog, it is
slender and active. It is fearless, and its great tusks are
dangerous weapons. The swine are the only ungulates
that are not strictly vegetable feeders. The habit of fat-
tening in summer was useful to wild hogs, since snow hid

most of their food in winter. The habit has been pre-
served under domestication. Are the small toes of the
hog useless? Are the "dew claws' 1 of cattle useless?
Will they probably become larger or smaller ? Order f

218

Illustrated Study
y

FlG - 395. HORSE.

FIG. 397. DOLPHIN.

FIG. 398. FISH.

.' A^ . ~-~~~-fr

FSG. 396. Ox.

e

Illustrated Study

219

FIG. 400. CHIMPANZEE. (See Fig. 406.)

Illustrated Study of Vertebrate Skeletons:
Taking man's skeleton as complete, which of these
seven skeletons is most incomplete ?

Regarding the fish skeleton as the original verte-
brate skeleton, how has it been modified for
(i) walking, (2) walking on two legs, (3) flying?

Which skeleton is probably a degenerate reversion
to original type ? (p. 209.)

How is the horse specialized for speed ?
Do all have tail vertebras, or vertebrae beyond
hip bones ? Does each have shoulder blades ?
Compare (i) fore limbs, (2) hind limbs, (3) jaws
of the seven skeletons. Which has relatively the
shortest jaws ? Why ? What seems to be the
typical number of ribs ? limbs ? digits ?
Does flipper of a dolphin have same bones as arm of a man ?
How many thumbs has chimpanzee ? Which is more specialized, the foot of a
man or a chimpanzee ? Is the foot of a man or a chimpanzee better suited "for
supporting weight ? How does its construction fit it for this ?

Which has a better hand, a man or a chimpanzee ? What is the difference in
their arms ? Does difference in structure correspond to difference in use ?
Which of the seven skeletons bears the most complex breastbone ?
Which skeleton bears no neck (or cervical) vertebrae ? Which bears only one ?
Are all the classes of vertebrates represented in this chart ? (p. 125.)

FIG. 399. MAN.

220

ANIMAL BIOLOGY

\
FIG. 401. SACRED MONKEY OF INDIA (Semnopithecus entellus}. x &

Monkeys, Apes, and Man. -
Study the figures (399, 400);
compare apes and man and ex-
plain each of the differences in
the following list : (i) feet, three
differences; (2) arms; (3) brain
case; (4) jaws; (5) canine
teeth ; (6) backbone ; (7) dis-
tance between the eyes.

A hand, unlike a foot, has
one of the digits, called a
thumb, placed opposite the
other four digits that it may be
used in grasping. Two-handed
man and four-handed apes and
monkeys are usually placed in FIG. 402 . -LEMUR

goz). X r V Which digit bears a

one order, the Primates, or claw?

MAMMALS

221

in two orders (see table, page 193). The lowest members
of this order are the lemurs of the old world. Because of

m rv

FIG. 403. BROAD-NOSED
MONKEY, x iV America.

.
^\

''f .

FIG. 404. NARROW-NOSED
MONKEY, x r*. Old World.

-

-

their hands and feet being true grasping organs, they are
placed among the primates, notwithstanding the long
muzzle and expres-
sionless, foxlike face.
(Fig. 402.) Next in
order are the tailed
monkeys, while the
tailless apes are the
highest next to man.
The primates of the
New World are all
monkeys with long
tails and broad noses.
They are found from
Paraguay to Mexico.
The monkeys and apes
of the Old World 'have
a thin partition be-
tween the nostrils,
and are thus distin-

guished from the

FIG. 405. GORILLA. (Size of a man.)

222

ANIMAL BIOLOGY

monkeys of the New World, which have a thicker par-
tition and have a broader nose. (Figs. 403, 404.) The
monkeys of America all have six molar teetJi in each half
jaw (Fig. 352); the monkeys and apes of the Old World
have thirty-two teeth which agree both in number and
arrangement with those of man.

Which of the primates figured in this book appear to
have the arm longer than the leg ? Which have the

eyes directed forward instead of
sideways, as with cats or dogs ?
Nearly all the primates are
forest dwellers, and inhabit warm
countries, where the boughs of
trees are never covered with ice
or snow. Their ability in climb-
ing serves greatly to protect
them from beasts of prey.
Many apes and monkeys are
able to assume the upright posi-
tion in walking, but they touch
the ground with their knuckles
every few steps to aid in preserving the balance.

The Simians are the highest family of primates below
man, and include the gorilla, chimpanzee, orang, and gib-
bon. Some of the simians weave together branches in the
treetops to form a rude nest, and all are very affectionate
and devoted to their young. How are apes most readily
distinguished from monkeys? (Figs. 401, 406.)

The study of man as related to his environment will be
taken up in detail in the part called Human Biology. We
will there examine the effect upon man's body of the rapid
changes since emerging from savagery that he has made
in food eaten, air breathed, clothing, and habits of life.

FIG. 406. CHIMPANZEE.

MAMMALS

223

FIG. 407. ANATOMY OF RABBIT.

a, incisor teeth;

b, b' , b" , salivary
glands :

k, larynx;
I, windpipe;

c, gullet;

d, diaphragm
(possessed only
by mammals) ;

e, stomach;

g, small intestine;
h, h' , large intes-

tine;
/, junction of small

and large intes-

tine;
g, g', caecum, or

blind sac
(corresponds to
the shrunken

rudiment ary
vermiform ap-
pendix in man);

m, carotid arte-
ries;

n, heart;

<?, aorta;

/, lungs;

q, end of sternum;

r, spleen;

j, kidney;

t, ureters (from
kidney to blad-
der 7>) .

2 brain of rabbit:

a, olfactory
nerves;

b, cerebrum:

c, midbrain;

d, cerebellum.

.k

Table for Review

FISH

FROG

TURTLE

BIRD

CAT

HORSE

MAN

Names of limbs

Acutest sense

Digits on fore
and hind limb

Locomotion

Kind of food

Care of young

i

St. Bernard
Eskimo
Poodle

Dachshund

German mastiff
English* bloodhound

Pointer

Bulldog

Greyhound

Newfoundland
Shepherd
Spitz

FIG. 408. ARTIFICIAL SELECTION. Its effects in causing varieties in one species.
Which of the dogs is specialized for speed ? Driving cattle ? Stopping cattle ?
Trailing by scent ? Finding game ? Drawing vehicles ? Going into holes ?
House pet ? Cold weather ? In Mexico there is a hairless dog specialized for hot
climates. The widely differing environments under various forms of domestica-
tion cause " sports " which breeders are quick to take advantage of when wishing
to develop new varieties. Professor De Vries by cultivating American evening
primroses in Europe has shown that a sudden change of environment may cause
not only varieties but new species to arise.

224

HUMAN BIOLOGY

CHAPTER I

INTRODUCTION

To which ' branch of animals does man belong ? To
which class and order in that branch ? (Animal Biology,
pages 125, 193.) There is no other animal species in the
same genus or order with man. This shows a wide pliysi-
cal difference be-
tween man and
other animals, but
man's mind iso-
lates him among
the other animals
still more.

The human
species is divided
into five varieties
or races: I. Cau-
casian (Fig. i).
Skin fair, hair wavy, eyes oval. (Europe except Finns
and Lapps, Western Asia, America.) 2. Mongolian. Skin
yellow, hair straight and black, face flat, nose blunt, almond
eyes. (Central Asia, China, Japan, Lapps and Finns of
Europe, Eskimos of North America.) 3. Americans. Skin
copper red, hair straight, nose straight or arched. (North
and South America.) 4. Malay. Skin brown, face flat,
hair black. (Australia and Islands of Pacific.) 5. Ethi-

B I

* . , ,

FIG. i. FACIAL ANGLES of Caucasian (nearly 90)
and Ethiopian (about 70). The angle between
lines crossing at front of upper jaw near base of
nose, one line drawn from most prominent part of
forehead, the other through hole of ear.

HUMAN BIOLOGY

opian (Fig. i). Skin dark, hair woolly, nose broad, lips
thick, jaws and teeth prominent, forehead retreating, great
toe shorter than next toe and separate. (Africa, America.)

There is a struggle between the races for the possession of different
lands. The Caucasian is gaining in Australia, Africa, and America.
With difficulty the Mongolians are kept from the western shores of
America. The Ethiopian in America shows a lessened rate of increase
every decade ; this may be due to the tendency of the race to crowd into
cities and the strain of suddenly changing from jungle life in less than
two centuries. Civilization is a strain upon any race. It is destroying
the American Indian. The Mongolian and Caucasian survive civiliza-
tion best, but insanity is increasing rapidly among the latter.

FIG. 2. INDIAN WEAPONS: LANCE AND ARROW HEADS.
From a bank of mussel shells (remains of savage feast) at Keyport, N.J.

Man's Original Environment. - - Primitive man lived without the use
of fire or weapons other than sticks or stones. His first home was in
the tropics, where his needs were readily supplied, and probably in
Asia. Many nations have a tradition of a home in a garden (Greek,
paradisos). His food was chiefly tree fruits and nuts. When because

of crowding he left nature's
garden, he acquired skill in
hunting and fishing and the
use of fire that flesh might sup-
plement the meager fruits of
colder climates. His weapons
were of rough (chipped) stone
at first in the old stone age.
In this age the mammoth lived.

FIG. 3. INDIAN TOMAHAWK.
Stone. Keyport, N.J.

Polished

He learned to polish implements in the new stone age. The Indians
were in that stage when Columbus came to America (Figs. 2, 3). The
cultivation of grain and the domestication of animals probably began
in this age. The bronze and iron ages followed the stone age.

INTRODUCTION 3

The Reaction between Man and his Environment. - - The estimates
by various geologists of the time man has existed as a species vary
from 20,000 to 200,000 years. The active life out of doors which man
led for ages (Fig. 4) has thoroughly adapted his body only for such a
life. Now steam and other forces work for him, and his muscles
dwindle ; his lungs are seldom fully expanded, and the unused portions
become unsound ; he lives in tight houses, and the impure air makes
his blood impure and his skin delicate ; he eats soft concentrated food,
and his teeth decay and his too roomy food tube becomes sluggish.
His nerves and brain are fully active and they become unsound from
overwork and impure blood. 1

FIG. 4. PRIMITIVE MAN, showing clothing and weapons of chase and war.

Degeneration of Unused Parts. -- Several facts just stated illustrate
the oiological law that disuse causes degeneration.

Man's Modification of his Environment.- -The energy of the world,
whether of coal, waterfall, oil, forest, or rich soil, has the sun as its
source. All of these are being destroyed by man, often with recklessness
and wantonness. The promised land which u flowed with milk and
honey 11 is now almost a desert. Other examples are Italy, Carthage,
Spain. The destruction of forests causes floods which wash away the
soil. It is estimated that there are only one fourth as many song birds
in the United States as there were fifteen years ago. Insects and weeds
or deserts replace rich soil, noble quadrupeds, singing birds, and stately
trees. Many farmers, however, preserve the fertility of the soil.

To the erect posture is due man's free use of his hands and the
cooperation of hands and senses. This has given man his intellectual

1 It has been prophesied that the future man will be a brownie-like crea-
ture with near-sighted eyes, shrunken body, slim little legs and arms, large
hairless head, toothless gums, a stomach using only predigested food, muscles
suited only to push an electric button or pull a lever, and mind very active.
But this disregards the indispensable need of a sound mind for a sound body.
There cannot even be a play of emotion without a change in the circulation.

4 HUMAN BIOLOGY

development. The erect position has given greater freedom to the
chest. Man uses fewer organs of locomotion than any other animal.
The opossum has two hands, but they are on the hind limbs. The
ape has four hands, but must use them all in locomotion. (What is a
hand ?) The erect position, however, makes spinal deformity easier to
acquire, and the whole weight being upon one hip at each step man is
liable to hip-joint diseases. In the horizontal trunk the organs lie one
behind another ; in man they lie one upon another, and are more liable
to crowding and displacement. The prone position in sickness helps
to restore them. Large blood vessels at neck, armpits, and groins,
which occupy protected positions in quadrupeds, are held to the front
and exposed to danger. The open end of the vermiform appendix and
of the windpipe are upward in the erect trunk of man. Valves are
lacking in some vertical veins and present where little needed in hori-
zontal veins. But the freedom of the hands more than makes up for
all the disadvantages of erectness.

The Survival of the Fittest. - - Those who do not work degenerate.
Those who overwork, or work with only a few organs, as the brain and
nerves, degenerate. The workers survive and increase in numbers, the

O '

idle perish and leave few descendants.

What rate of adjustment to new environment is possi-
ble for man? This has not been ascertained; it is prob-
ably much slower than has been generally imagined. The
natives of Tasmania, New Zealand, and many of the
Pacific Islands became extinct in less than a century after
adopting clothing and copying other habits from Euro-
peans. Life in the country in civilized lands differs less
from the environment of primitive man than does life in
cities. Cities have been likened to the lion's cave in the
fable, to which many tracks led, but from which none led.
The care of health in cities is now making rapid strides
along the biological basis of purer air, more open space, less
noise, simple food, and pure water. Biology, by supplying
as a standard the conditions which molded man's body
for ages, furnishes a simple and sure basis for hygiene.
To mention one instance among many, man blundered for
centuries in attempting the cure of consumption, and well-

INTRODUCTION

5

nigh gave up in despair. Yet it has recently been shown
that if the sufferer returns only in a measure to the open-
air habits of his remote ancestors, tuberculosis is one of
the most preventable of diseases. The biological guide to
health is surer and simpler than tinkering with drugs, fuss-
ing with dietetics, and avoiding exposure. Man is of all
animals least thoroughly adjusted to his environment, be-
cause of his continual and rapid progress. Disease may
be defined as the process by ivJiicli tJie body adapts, or at-
tempts to adapt, itself to so sudden a change of environ-
ment that some organ has failed to work in harmony with
the others. By disease the body comes into adjustment
with the new condition, or attempts to do so.

Protoplasm.- -The life and growth of man's body, as
the life and growth of all animals and plants, depend upon
the activity of the living
substance called proto-
plasm, as manifested in
minute bodies called cells.
In fact, protoplasm can-
not exist outside of cells.
The cells of the human
body and their relation to
the body as a whole will
next be considered.

FIG. 5. AN AMEBA, highly magnified.
, nucleus; psd, false foot.

The Ameba. Of all the
animal kingdom, the minute
creatures that can be seen only with a microscope are most different from
man. One of the most interesting of these is the a-me'ba (Fig. 5 ;
spelled also amaba, see Animal Biology, Chap. II). A thousand of
them placed in a row would hardly reach an inch. Some may doubt
whether the ameba is a complete animal. Study the figures of it, and
no head, or arms, or legs, or mouth can be found. It appears, when
still, to be merely a lump of jelly. But the ameba can push out any
part of its body as a foot, and move slowly by rolling its body into the

6

HUMAN BIOLOGY

a.

foot. 77 can put out any part of its body as an arm, and take in a
speck of food ; or, if the food happens to be near, the ameba can make
a mouth in any part of its body, and swallow the food by closing around
it (Animal Biology, Fig. 12). The ameba has no lungs, but breathes
with all the surface of its body. Any part of its body can do anything
that another part can do. When the ameba grows to a certain size, Lt
multiplies by squeezing together near the middle (Animal Biology, Fig.
13) and dividing into two parts. Amebas have not been observed to
die of old age ; starvation and accident aside, they are immortal.

The Ameba and Man Compared.- -The microscope shows us that the
skin, the muscles, the blood, in fact, all parts of the body, contain

numberless small
Parts called cells.
These cells are
continually chang-
ing with the activi-
ties of the body.
One of the most
interesting kinds

of cells we shall find to be the white blood cells, or corpuscles. One is
shown in Fig. 6, with the changes that it had undergone at intervals
of one minute. The thought readily occurs that these cells, although
part of mail's body, resemble tJie ameba that lives an independent life.
A man or a horse or a fish in fact any animal not a protozoan has
something of the nature of a colony, or collection, of one-celled ani-
mals. We are now prepared to understand a little as to how the body
grows, and how a cut in the skin is re-
paired. The cells take the nourishment
brought by the blood, use it, and grow
and multiply like the ameba. Thus new
tissue is formed. All animals and vege-
tables --that is to say, all living things
are made of cells.

FIG. 6. A WHITE BLOOD CELL, magnified ; forms
noticed at intervals of one minute.

A living cell always contains a
still smaller body called a nucleus
(Fig. 7). There is sometimes a
small dot in the nucleus, called
the nucleohis. TJie main body of
the cell consists of the living substance called protoplasm, con-
taining nitrogen. Usually, but not always, there is a wall

FIG. 7. DIAGRAM OF A
CELL.

protoplasm; n, nucleus; ', nu-
cleolus.

INTR OD UCTION J

surrounding the cell, called the cell wall. Workers with
the microscope found long ago that animals and plants are
constructed of little chambers which they called cells. It
was found later that the soft contents in the little chambers
is of more importance than the walls which the protoplasm
builds around itself. A living cell is not like a cell in a
honeycomb or a prison. In biology we define a cell as a
bit of protoplasm containing a nucleus. No smaller part of
living matter can live alone. The protoplasm of the nu-
cleus is called nucleoplasm ; the rest of the protoplasm is
called cytoplasm.

A fiber is threadlike, and is either a slender cell (Fig. 8),
a slender row of cells (Fig. 10), or a branch of a cell. A

-n,

FIG. 8. A CELL (from involuntary muscle), so slender that it is called a fiber.

tissue is defined as a network of fibers or a mass of similar
cells serving the same purpose, or doing the same work. A
membrane is a thin sheetlike tissue.

The Nature of the Human Body. The human body is a
community of cells, and may be compared to a community
of people. It is a crowded community, for all the citizens
live side by side as they work. They are so small that it
takes several hundred of them to make a line an inch long.
We should never have suspected the existence of cells had
it not been for the microscope ; but now we know that
they eat and breathe and work and divide into young cells
which take the place of the old ones.

A child that is born in a community of people may become a railroad
man and carry food and other freight from place to place ; so, in the
great community of cells (see Fig. 9) making up the human body, the
red blood cells, like the railroad man, are employed in carrying material
from place to place. But the community is old-fashioned, for the

8

HUMAN BIOLOGY

citizens build canals instead of railroads for their commerce (see Fig.
84). Just as a child may grow up to be ^farmer and aid in the con-
version of crude soil into things suitable for the use of man, so the
digestive cells take the food we eat and change it into material with
which the cells can build tissue. Some of the citizens of a community
must, at times, take the part of soldiers and policemen, and protect the

community against
the attacks of ene-
mies. The ivhite blood
cells, already referred
to, may be called the
soldiers ; for they go
to any part attacked
by injurious germs, a
particle of poison, or
other enemy, and try
to destroy the ene-

sSSi^SiS^^^ g/fc mies by devouring or

digesting them. At
other times they help
to repair a break in
the skin. If a splin-
ter gets into the skin, the white blood cells form a white pus around
the splinter and remove it. In fact, the white blood cell has been re-
ferred to as a kind of Jack-at-all-trades. In the human community
there are certain persons who reach the positions of teachers, law-
makers, and governors ; they instruct and direct the other members of
the community. Just so, in the community of cells, there are certain
cells called nerve cells (see Fig. n) that have the duty of governing
and directing the other cells. The nerve cells are most abundant in
the brain. Large cities must have scavengers. Likewise in the human
body, a community composed of millions of cells, there are certain cells
in the skin and the kidneys which have this duty. They are continually
removing impurities from the body. 1

Division of Labor. There is a great advantage in each
cell of the human body having its special work, instead of
having to do everything for itself, as each ameba cell must
do. Under tJiis system each cell can do its own work better
than a cell of any other kind can do it. Among wild tribes

1 From Coleman's " Hygienic Physiology," The Macmillan Co., N.Y.

FIG. 9. VARIOUS CELLS of the body. (Jegi.)
Tiny citizens of the bodily community.

INTR OD UC TION 9

there is very little division of labor. Each man makes his
own weapons, each knows how to weave coarse cloth, how
to cook, how to farm, etc. Savages do not have as good
weapons as do people who leave the making of weapons to
certain men whose special business it is. What kind ol
pocketknives or pencils do you think the boys of this
country would have if each boy had to make his own
pocketknife or pencil ? What kind of scissors and thread
would the girls have if each girl had to make them her-
self ? Our muscle cells can contract better than the
ameba ; the cells in the lungs can absorb oxygen better
than the ameba. We have just as great an advantage in
digestion, feeling, and other processes ; for the ameba eats
without a mouth, digests without a stomach, feels without
nerves, breathes without lungs, and moves without muscles.
Division of labor between the sexes also occurs among
the higher animals. Those who desire that man and
woman should have the same education and work would
violate the biological law of "progress by specialization,"
which could only cause race degeneration.

A part of the body which is somewhat distinct from
surrounding parts, and has special work to do, is called an
organ ; the special work which the organ does is called its
function. The eye is the organ of sight. The skin is an
organ ; its function is to protect the body. This book will
treat of (i) the structure, appearance, and position of each
organ, or anatomy; (2) the function of each organ, or
physiology; (3) the conditions of health for each organ,
or hygiene ; (4) the conditions under which each organ
worked in the primitive life of the race 5(5) the effects of
change of environment ; (6) the anatomy of man compared
with the lower animals. (5) belongs to the science of
Ecology. These sciences are parts of the science of Biology.

10

HUMAN BIOLOGy

FIG. 10. - - THREE
MUSCLE FIBERS
from the heart
(showing the nu-
clei of six cells).

The Tissues. - - As the organs have dif-
ferent functions, tJiey must have different
structures that they may be adapted to their
work. Just as a house must have brick
for the chimney, shingles for the roof,
and nails to hold the timbers and other
parts together, so the body has various
tissues to serve different purposes. The
bones must not be constructed like the
muscles, and the muscles cannot be like
the skin. The chief work of the cells is
to construct the tissues and repair them.
During life changes are constantly going
on. Careful little workmen are keeping
watch over every part of
the body; thrifty little
builders are busy in repairing and restor-
ing. No sooner is one particle removed
than another takes its place. In one di-
rection the cells, acting as undertakers, are
hurrying away matter which is dead ; in
the other direction the unseen builders
are filling the vacant places with matter
that is living.

The Seven Tissues. There are seven
kinds of tissues. Two of them, the mus-
cular and nervous tissues, are called the
master tissues, since they control and ex-
pend the energies of the body. The other
five tissues are called the supporting tis-
sues, since they supply the energy to the FIG. n. NERVE
master tissues, support them in place, CELLS showing

their branches

nourish and protect them. interlacing.

INTRODUCTION

II

FIG. 12. CONNECTIVE TISSUE CELLS,
removed from among the fibers of
Fig. 13.

t/, c, nucleus; /. branches.

The Master Tissues.- -The muscular tissue consists
chiefly of rows of cells placed end to end (Fig. 10). These
cells have the remarkable property of becoming broader
and shorter when stimulated by impulses from nerve cells

The nerve tissue consists
of cells with long, spiderlike
branches (Fig. u). Some
nerve cells have branches
several feet long, so long that
they go from the backbone
to the foot. The branches
are called nerve fibers (Fig.
142). Nerve fibers which
carry impulses to the nerve
cells are called sensory fibers.
The nerve fibers which carry
impulses from the nerve cells
are called motor fibers. The
organs are set to work by
impulses through the motor
fibers. Besides these two
master tissues there are five
supporting tissues.

Connective tissue, like all
other tissues, contains cells

(see Fig. 12), but it consists

, . n . f, -, , FIG. 13. CONNECTIVE TISSUE

chiefly of fine fibers. These FIBERS

fibers are of two kinds, -
very fine white fibers which
are inelastic, and larger yellow fibers which are very elastic
(see Fig. 13). Connective tissue is found in every organ,
binding together the other tissues and cells. It is inter-
woven among the muscle cells, and the tendons at the

C

a, b, bundles of white fibers; c, a yellow
fiber.

12

HUMAN BIOLOGY

ends of the muscles are composed almost wholly of it. If
every other tissue were removed, the connective tissue
would still give a perfect model of all the organs. How
abundant this tissue is in the skin may be known from the
fact that leather consists entirely of it.

Fatty (Adipose) Tissue. - - Fatty tissue is formed by the
deposit of oil in connective tissue cells (see Fig. 14). Fat is

held in meshes of
connective tissue
fibers. That fatty
tissue consists not
alone of fat, but of
fibers also, is shown
when hog fat is
rendered into lard,
certain tough parts
called "crack-
lings" being left.
What is the differ-
ence between beef
fat and tallow ?

Epithelial tissue
consists of one or
more layers of dis-
tinct cells packed
close together (see
Fig. 15). It con-
tains no connective tissue or other fibers, and is the simplest
of the tissues. Epithelial tissue forms the outer layer of
the skin, called the epidermis, and the mucous membrane
lining the interior of the body. It contains no blood ves-
sels, the epithelial cells obtaining their nourishment from
the watery portion of the blood which soaks through the

FIG. 14. FATTY TISSUE. Five fat cells, held in
bundles of connective tissue fibers.

a is a large oil drop; ;;z, cell wall; nucleus () and proto-
plasm (_/) have been pushed aside by oil drop (a).

INTRODUCTION

underlying tissues. Epithelial cells are
usually transparent ; for instance, the
blood is visible beneath the mucous
membrane of the lips. The finger nails
are made of epithelial cells, and they
are nearly transparent.

There are two classes of epithelial
cells ; one class forms protective cover-
ings (Fig. 15) ; the other class forms the
lining of glands (Fig. 16). Glands are
cavities whose lining of epithelial cells
(Fig. 17) form either useful fluids called
secretions to aid the body in its work, or
harmful fluids called excretions to be cast
out, or excreted. Most glands empty
their fluids through tubes called ducts.

Cartilaginous tissue is tough, yet
elastic. Cartilage or gristle may be
readily felt in the ears, the windpipe,
and the lower half of the nose. This
tissue consists of cartilage cells embedded

in an intercellular substance through

>

which run connective tissue fibers (see
Fig. 1 8). If yellow fibers predominate,
the cartilage is yellow and very elastic,
as in the ear ; if white fibers predomi-
nate, it is white and less elastic, as in
the pads of gristle between the bones
of the spinal column. Cartilage is to
prevent jars, and, in movable joints, to
lessen friction.

Bony (Osseous) Tissue.- -Solid bone
is seen under the microscope to contain

FIG. 15. EPITHELIAL
TISSUE (epidermis ol
skin, magnified).

FIG. 16. EPITHELIAL

TISSUE; cells form-
ing two glands in
wall of stomach.

FIG. 17. Six GLAND
CELLS : at left,
shrunken after activ-
ity ; at right, rested,
full of granules.

HUMAN BIOLOGY

FIG. 18. CARTILAGINOUS
TJSSUE. A thin slice highly
magnified.

a, b, c, groups of cells; m, inter-
cellular substance.

many minute cavities (Fig. 19). /;/ these cavities the bone
cells lie self -imprisoned in walls of stone ; for these cells

have formed the bone by deposit-
ing limestone and phosphate of
lime around themselves. There
are minute canals (3, Fig. 19),
however, through which nourish-
ment comes to the cells. The
watery portion of the blood passes
through these small canals from
the blood vessels that flow through
the larger canals (i, Fig. 19).
Bone cells may live for years, al-
though some of the other cells of
the body live only a few hours.

New cells to repair the tissues are
formed by subdivision of the cells, as
with the ameba. Unlike protozoans,
many-celled animals are mortal because
the outer cells prevent the deeper cells
from purifying themselves perfectly and
obtaining pure food and oxygen. Even
the arteries of an old man become hard-
ened by the deposit of mineral matter
which the body has been unable to ex-
crete.

The body is kept alive anc
warm by burning, or oxidation,
One fifth of the air is oxygen gas.
We breathe it during every min-
ute of our existence. It is car-
ried by the blood to all the tis-

r __

FIG. 19. BONY TISSUE. Thin
slice across bone, as viewed
through microscope.

Larger blood tubes pass through
the large holes (i) ; the cavities
containing bone cells lie in cir-
cles, and are connected by fine
tubes (3) with the larger tubes.

sues. Not one of the cells could
work without oxygen. Without it the body would soon be
cold and dead, for oxygen keeps the body alive and warm

INTR OD UC TION I 5

by uniting in the cells with sugar, fat, and all other sub-
stances in the body except water and salt. Oxygen burns
or consumes the substances with which it unites, and the
process is called oxidation. Hence the cells have to be
continually growing and multiplying to repair the tissue
and replace the material used up by oxidation. Sugar and
flour and fat oxidize, or burn, outside of the body, as well
as in it, as can be proved by throwing them into a fire.
Water and salt are two foods that do not burn. Hence
they can furnish no heat or energy to the body. Water
puts out a fire instead of helping it, and so does salt.
Throw salt into a fire or on a stove; it will pop like sand,
but will not burn.

The cells need the oxygen of fresh air ; they need food
for the oxygen to unite with, but they arc injured by many
substances called poisons. Arsenic destroys the red blood
cells. Strychnine attacks the nerve cells in the spinal
cord. Alcohol attacks the epithelial cells lining the
stomach and, when it is absorbed, attacks the nerve cells
and other cells. Morphine attacks the nerve cells.

WRITTEN EXERCISES. - - Draw a series of seven pictures to show the
seven tissues (Figs. 10. 14, 15, 18, 19). Write the "Autobiography 11
of a White Blood Cell (see also pages 59 and 68). The Rewards of
Caring for the Health. Health and the Disposition. Which is more
important, a Thorough Knowledge of Geography or of Physiology?
Five Things which people Value above Health (and lose health to ob-
tain). The Blessings that follow Good Health. The Tissues Com-
pared (function, proportion of cells, intercellular material and fibers,
activity, rate of change).

See also pages 50, 116. Pupils should choose their own subjects.

CHAPTER II

THE SKIN

NOTE TO TEACHER.- -The experiments should be assigned in turn
to the pupils as each chapter is reached : e.g. this set of 13 will leave 3
pupils in a class of 39 to stand responsible for each experiment. Each
pupil should do the work separately and credit may be given for the
best results. Encourage (or require) each pupil to try every experi-
ment and record them in a note book.

Experiment i. (At home or in class.) Albinism. --Study a white
rabbit as an example of albinism. Does albinism affect only the skin?
What evidence that its blood is of normal color?

Experiment 2. Use of Hairs on the Skin. - - Let one pupil rest his
hand upon the desk behind him while another touches a hair on his
hand with a pencil. He should speak at the moment, if it is felt. Do
the hairs increase the sensitiveness of the skin? What was their use
with primitive man? Are the hands of all your acquaintances equally
hairy? Are the hairs to be classed as rudimentary? Will they disap-
pear? Will the race become baldheaded?

Experiment 3. (Home or school.) Invisible Perspiration. -- Hold
a piece of cold glass near the hand or place the cheek near a cold win-
dow pane and notice for evidence of moisture. Its source?

Experiment 4. Effect of Evaporation on Temperature. Read a
thermometer and cover its bulb with a moist cloth. Read again after
twenty minutes. Repeat experiment in breeze.

Experiment 5. Moisten one hand and allow it to dry. Touch the
other hand with it. Explain result.

Experiment 6. Absorbing Power of Fabrics. - - Wet the hands and
dry them upon a piece of cotton cloth. Repeat with woolen, linen, and
silk. Arrange in list according to readiness in absorbing water.

Experiment 7. Rates of Drying. -- Immerse the cloths in water and
hang them up to dry. Test their rates of drying with dry powder or by
touch.

Experiment 8. Test Looseness of Weave of above cloths by measur-
ing the distance pieces of equal length will stretch.

Experiment 9. Does Cotton or Wool protect better from Radiant
Heat? --Lay a thermometer in the sun for ten minutes, first covering

16

\-^t^zp&

i&

COLORED FIGURE i. SECTION OF SKIN (diagram, enlarged 25 times). On the left
the connective tissue fibers of the true skin are shown.

in cutis (c), or dermis, find capillaries, nerve fibers, fat cells, /7t^ sweat glands and ducts, four
oil glands (two in section), two hairs, three nerve papillae, five papillae containing capillaries,
t2uo muscles for erecting hairs. In epidermis find flat cells, round cells, and pigment cells.

FIG. 2. WHERE
THE FOOD is

ABSORBED (villus Of

intestine).

FIG. 3. WHERE

THE FOOD is

USED (cells with

lymph spaces).

i,j, jaws; ol, nerve of smell;
op, nerve of sight : ^,
brain; /, tongue; ep, epi
glottis; oe, gullet;
th, thymus gland;
Ig, lung; //, heart;
/, liver; g, stom-
ach; s. spleen;
/, pancreas;
k, kidney; d.
diaphragm;
m, muscle;
it, bladder;
ch, spinal
cord; 7', ver-
tebrae.

/fi/sc/e ce//s

t ///SI Itftlffff af ,
////////// .','> ' .-.

FIG. 2.

FIG. 4. -

IDEAL SEC-
TION OF
MAMMAL.

Compare with organs of
man (colored Fig. 6).

THE SKIN I/

it with a woolen cloth. Note change in reading. After it regains first
reading, repeat, covering it with a cotton cloth of same weight and tex-
ture ? Conclusion ? Expose wrists or arms to sun for five minutes, one
protected by the cotton, the other by the wool. Result ? Conclusion?

Experiment 10. Rates of Heat Absorption and Radiation by Different
Colors. -- Expose thermometer to sunlight, covered successively by pieces
of cloth of same thickness, material, and texture. Use black, blue, red,
yellow, and white cloth. Note rise of temperature for equal times in each
case ; also the fall of temperature for equal times after removal to shade.

Experiment 1 1. Effects of Dry Powders. - - Prepare two squares from
the same piece of leather (e.g. an old shoe). Moisten them both, and
apply face powder to one. Which dries more quickly? Repeat after
oiling them. Powder a portion of the face or arm daily for a week and
compare with the clean portion.

Experimejit \ 2. Dissect the kidney of an ox or sheep, making out
the parts mentioned in the text, p. 26.

Experiment 13. (In class.) Emergency Drill. - - Have one pupil wet
an imaginary burn on the arm of another, treat it with flour or soda, and
bandage. (See text.)

The Skin has Two Layers.- The outer layer is called the
epidermis ; it is thinner, more transparent, and less elastic
than the inner layer, or dcrmis. The epidermis is com-
posed of epithelial cells packed close together (see colored
Fig. i).

The dermis, or inner layer, is a closely woven sheet of
connective tissue (colored Fig. i) containing a great num-
ber of sweat and oil glands, roots of hairs, blood vessels,
absorbent vessels (lymphatics), and nerves (colored Fig. i).
The dermis is sometimes called the true skin because it is
of greater importance than the epidermis. It is united
loosely to the underlying organs by a layer of connective
tissue. It is in this layer that fat is stored. The upper
surface of the dermis rises into a multitude of projections
(see colored Fig. i) called papiVlcE (singular, papilla). The
epidermis fits closely over them and completely levels up
the spaces between them except on the palms and the
soles. Here the papillae are in rows, and there is a fine

i8

HUMAN BIOLOGY

ridge in the skin above each row of papillae (Fig. 24). In
the papillae are small loops of blood vessels and sometimes
a nerve fiber (colored Fig. i).

The epidermis is composed of a mass of cells held to-
gether by a cement resembling the white of an egg. The
cells near the surface are hard and flattened ; those deeper
down near the dermis are round and soft (see Fig. 21).

These cells are liv-
ing cells. They are
kept alive by the
nourishment in the
watery portion of
the blood which
soaks through from
the blood tubes in
the neighboring pa-
pillae. Hence these
cells are growing
cells; they subdivide
when they reach a
certain size, and re-
place those wearing
away at the surface, thus constantly repairing the epider-
mis. The dry outer cells wear away rapidly. They have
no nuclei and are dead cells. The new cells forming be-
neath push them so far away from the dermis that nour-
ishment no longer reaches them, and they die.

Pigment. The cells in the lower layers of the epidermis
contain grains of coloring matter, or pigment. All other
cells of the epidermis are transparent ; the pigment has the
function of absorbing and arresting light. Albinos or
animals entirely without pigment have pallid skins and
pink eyes (Exp. i).

FIG. 20. EPIDERMIS
OF ETHIOPIAN.

FIG. 21. EPIDERMIS
OF CAUCASIAN.

THE SKIN 19

Immigrants from a Cloudy to a Sunny Climate. Adaptation. The
cells of the deeper tissues can readily be exhausted by the stimulation
of too much light. The sunnier the climate, the greater the need of
pigment ; hence the dark skin of the negro and the blonde skin and
hair of the Norwegian. European immigrants to sunny America will
grow darker. The Indian's skin is better suited to our climate than is
a fair skin. Brunettes have a better chance for adaptation than blondes.
The American type when developed will doubtless be brunette.

The hair grows from a pit or follicle (Fig. 22). Blood
vessels and a nerve fiber go to the root or bulb from which
a hair grows. The hair will grow un-
til this papilla, or bulb, is destroyed
(Exp. 2).

Adaptation of the scalp to a tight warm cov-
ering is accomplished through the shedding of
the hair rendered useless by the covering. It is
impossible to stop the growth of superfluous hair
unless the hair papillae are destroyed with an
electric needle, such is the vitality of hair; yet
many men, by overheating the head and cutting

off the circulation with tight hats, destroy much FlG - 22> ' DEVELOP '
, .. ..' ~, MEXT OF A HAIR

of the hair before reaching middle age. 1 he AND TWQ

health of the hair can be restored and its loss GLANDS.
be stopped by going bareheaded except in the

hot sun or in extremely cold weather. This frees the circulation; cold
air and light stimulate the cells of the scalp. Some men wear hats,
even at night in summer. The brain needs the protection of the hair.
Beard protects the larynx or voice box. which is large and exposed in man.
It was also a protection in hunting wild beasts and in war. Compare
mane of lion, not possessed by lioness. " Goose-flesh " after a cold bath
is caused by the contraction of small muscles (colored Fig. i), raising
the now tiny hairs in an absurdly useless effort to keep the body warm.

The nails are dense, thick plates of epidermis growing
from a number of papillae situated in a groove, or fold, of
the skin ; there are many fine papillae along the bed from
which the nail grows. Since it grows from its under side
as well as from the little fold of skin at its rcot, the nail is
thicker at the end than near the root.

20

HUMAN BIOLOGY

FIG. 23. A, DEVELOPMENT OF
SWEAT GLAND; B, SWEAT
TUBE DEVELOPED.

The oil glands empty into the hair follicles (colored Fig. I ).
They form an oil from the blood that keeps the hair glossy

A and the surface of tJie skin soft

t and flexible by preventing ex-
cessive drying. Hair oil should
never be used upon the hair, as
the oil soon becomes rancid, and
besides causes dust and dirt to
stick to the hair.

The sweat glands (Fig. 23),
like the hair bulbs, are deep in
the lowest part of the dermis.
A sweat gland Jias the form of a
tube coiled into a ^//(colored Fig. i). This tube continues
as a duct through the two layers of skin, and its opening
at the surface is called a. pore (Fig. 24). The perspiration
evaporates as fast as it flows out through the pores, if the
secretion is slow ; but if poured out rapidly, it gathers into
drops (Exp. 3). The perspiration is chiefly water, contain-
ing in solution several salts, including
common salt and a trace of a white,
crystalline substance called urea. The
material for the perspiration is fur-
nished by the blood flowing around
the gland in a network of fine tubes.
The amount of the perspiration is con-
trolled in two ways : by nerves that
regulate the activity of the epithelial
cells lining the gland, and by nerves
that regulate the size of the blood ves-
sels supplying the gland (Fig. 25).

FIG. 24. PORES on
ridges in palm of hand.

THOUGHT QUESTIONS. Freckles, Warts, Moles, Scars, Proud Flesh,
Pimples, Blackheads. Use these names in the proper places below :

THE SKIN 21

A rough prominence formed by several papillae growing through the
epidermis at a weak spot and enlarging is called a - . Small patches
of pigment developing on the hands and face from much exposure to
the sun are called - . The growth of exposed dermis sprouting
through an opening in the epidermis due to accident is called - -.
(This should be scraped off and cauterized to aid the epidermis to grow
over it again.) Sometimes a cut heals in such a way that no epidermis
and therefore no pigment cells cover the place of injury, which is occu-
pied only by white fibrous tissue (cicatricial tissue) of the true skin.
In this case the mark left is called a cicatrice or -. If pores or the
openings of oil glands become clogged, but not enlarged, little swell-
ings called - - may result. An enlarged pore filled with oil and dirt
is called a - . A spot present since birth, dark with pigment, and
often containing hairs and blood vessels, is called a - .

Regulation of Temperature. - -As is well known, rapid
running or violent exercise of any kind causes profuse per-
spiration. The sweat glands are connected with the brain
by means of nerves, and when the body has too much heat,
a nerve impulse from tJie lowest part of the brain causes the
sweat glands to form sweat more rapidly. Heat and exer-
cise may cause the activity of the sweat glands to increase
to forty times the usual rate. The evaporation of the sweat
cools the body, for a large amount of heat is required to
evaporate a small amount of water (Exp. 4 and 5). This
is shown by the cooling effect of sprinkling water on the
floor on a warm day. By fanning we hasten the cooling
of the body (Exp. 4).

Exercise tends to heat the body, but it also causes us to
breathe faster and causes much blood to flow through the
skin. Both of these effects aid in cooling the body, for
the cool air is drawn into the lungs, becomes warm, and
takes away heat when it leaves ; and the warm blood flow-
ing in the skin loses some of its heat to the cool air in con-
tact with the skin.

Effects of Alcohol upon the Skin. - The more blood
goes to the skin, the more blood is cooled. The body

22 HUMAN BIOLOGY

as a whole may be cooler, but we fed warmer ivJien
tJierc is more blood in tJie skin because of tJie effect of
t/ie warm blood upon the nerves of temperature. There
are no nerves for perceiving temperature except in the
skin and mucous membrane, and the body has practically
no sensation of heat or cold except from the skin or
mucous membrane. That alcoholic drinks make the skin
red is commonly noticed. Often the skin is flushed by
one drink ; the bloodshot eyes and purple nose of the
toper are the results of habitual use. Can you explain
why alcohol brings a deceptive feeling of warmth ? Why
does alcohol increase the danger of freezing during ex-
posure in very cold weather ? During the chill which pre-
cedes a fever, the body (except the skin) is really warmer
than usual.

Exercise will relieve internal congestion and send the
blood to the skin better than alcohol. This is the effect
sought by sedentary people who use it to replace exercise.
The long and sad experience of the race with alcohol
proves that the attempt to adapt the body to its use should
be given up.

THOUGHT QUESTIONS. The Functions of the Skin. 1. State a fact
which shows that the skin is a protection ; gives off offensive sub-
stances ; regulates the temperature. 2. What is lacking in the skin
when it cracks or chaps ? Why does this occur more often in cold
weather? When the hands are bathed with great frequency?

Effects of Indoor and Outdoor Life. Those who live much out of
doors, exposed to sunlight and pure, cold air, are robust and hardy ;
while those whose occupations keep them constantly indoors, especially
if no physical labor is necessary, show by their pale skins, their fat and
flabby, or their thin and emaciated bodies, the weakening effect of such
a life. We are descended from ancestors who lived in the open air, and
it is impossible for a human being to live much indoors without de-
generation of the body and shortening of life.

A Well-trained Skin. --We hear a great, deal about training the
muscles, the brain, the eye, the hand ; yet we may fail to realize that

THE SKIN

the skin also can be trained and its powers developed, or it can be
allowed to become weak and powerless. Soundness of the skin is as es-
sential to health as soundness of any other organ. A rosy color indicates
good health because of a well-balanced circulation. Paleness often
means internal congestion and great liability to indigestion, colds, etc.
Hence we think a rosy skin beautiful and a pale skin ugly. With the
skin in a healthy condition, the danger of taking most diseases is
removed.

Characteristics of a Vigorous Skin. --A person who readily takes
cold, who is fearful of drafts of air at all times, has a weak skin. To
one who has a healthy skin drafts are dangerous only when the skin
is moist with perspira-
tion, and the body is
inactive ; cold drafts
may then do harm.
Cold air and cold water
are the best means of
toughening a tender
skin. A batJi is to tJie
skin what gymnastic
exercises are to the
muscles. The muscle
fibers in the walls of
the blood vessels and
.the nerves controlling
them need exercise as
well as the rest of the
body (Fig. 25).

Importance of
Bathing. -If we

followed tlie out- FIG. 25. BLOOD VESSELS, with the VASO-MOTOR

NERVES which accompany and control them.

door life and wore

tJie scanty clothing of savage races, tJie rains , the cool air,
and the sunlight would keep our skins vigorous and
sound. But want of exercise to induce perspiration allows
the sweat glands to become stopped up. The wearing
of clothes is a very uncleanly custom. Clothes make the
skin inactive, yet confine the impurities which the
weakened skin may still be able to excrete. Thick and

o

24 HUMAN BIOLOGY

heavy clothing and overheated rooms prevent the nerves
from being stimulated by cold air and sunlight. The best
way to counteract these weakening conditions is by frequent
cool or cold bat/is. An air bath, which consists of exposing
the bare skin to the air for half an hour or more before
dressing in the morning, may take the place of a cold
bath. Even the lower animals bathe : birds, dogs, and
many lower animals bathe in the rivers. An elephant
sometimes takes a bath by showering water over his back
with his trunk.

Treatment of Burns. Wet the burn with a little water
and sprinkle common baking soda or flour thickly on it.
Bind with a narrow bandage. For deeper burns soak a
small square of cloth in a strong solution of baking soda,
bandage it on wound, and keep it wet with the solution.
Olive, cotton seed, and linseed oils are excellent for burns
(Exp. 13).

Hygiene of Bathing. - - A bath should not be taken
within an hour after a meal. Cold baths (i) should
never be taken in a cold room nor when the skin is*
cold ; (2) are more beneficial in summer and in warm cli-
mates, but are necessary in winter for those who live in
overheated houses or dress very warmly; (3) should be
followed in winter by vigorous rubbing and a glowing re-
action ; (4) should usually not last longer than one minute
in winter. Warm baths (i) are more cleansing than cold
baths ; (2) should not be used alone but should always be
followed by a dash of cold water ; (3) are better than cold
baths if the body is greatly fatigued ; (4) are more benefi-
cial when going to bed than upon rising.

Cold baths and very hot baths are both stimulants to
the nervous system and cause an expenditure of nervous
energy. For one whose nervous energy is at a very low

THE SKIN 25

ebb cold baths may be weakening if prolonged beyond a
few seconds. For one with skin relaxed and body sluggish
from indoor life, cool baths arouse activity, tone up the
body, and may be as beneficial as outdoor exercise in restor-
ing vigorous health. As with every hygienic measure,
each person must find out by experience what suits him
best.

Clothing was first employed for ornament. In cold climates it aids
in maintaining the uniform temperature of the body ; to it man owes
his distinction of being the most widely distributed of animal species.
Clothing prevents rapid escape of bodily heat by confining air, a non-
conductor of heat, in its meshes. Hence, the effect of clothing varies
with the weave ; likewise with the tendency of its fibers to keep dry, for
if water replaces air in the meshes, the body loses heat rapidly. For
cool clothing the weave should be hard and tight, for warm clothing it
should be soft and loose. The warmth of clothing is affected more by
its weave than by its weight. The weave may be tested by stretching;
the fabric with softest weave will stretch the most (Exp. 8). Linen
makes the coolest of all clothing because it weaves hard with small
meshes ; silk ranks next in coolness. When warmth is desired, linen
or cotton garments should be made of fabrics woven like stockings.
Linen and cotton both absorb water rapidly and dry rapidly (Exp. 6) ;
if woolen did also, it would make the warmest of all clothing, but it
dries so slowly (Exp. 7) that it cools the body after the activity is over
instead of drying rapidly and, as with linen and cotton, keeping the
body cool during the exertion (Exp. o) . Woolen weaves with the
largest air meshes of all materials ; hence its warmth increases perspi-
ration, but woolen removes perspiration most slowly and tends to relax
the skin if the wearer has an active skin or makes active exertion.
Woolen is best for underclothing during extreme cold only or for per-
sons who neve'r make such vigorous muscular exertion as to perspire.
In general, cotton or linen is best for underwear. They possess the
added advantages of less cost and of not shrinking out of size and
shape when washed. A mixture of cotton and silk or of cotton and
wool is more durable than either alone. Cotton and linen, unlike
woolen, are not attacked by insect pests.

It is better to depend more upon outer clothing than underclothing
for warmth. In the Gulf states the wearing of woolen outer clothing
indoors during warm weather (which lasts eight months) is unhealth-
ful and uncleanly because of the perspiration absorbed ; this is as

26

HUMAN BIOLOGY

absurd as to wear cotton outer clothing in Northern states during the
eight cold months.

Black clothing absorbs twice, blue almost twice, red and yellow
almost one and a half times, as much heat as white clothing (Exp. 10).
Which material protects best from radiant heat ? (Exp. 9.) Because
large blood vessels are near the surface at the neck, wrists, and ankles
very thin or no covering at those points aids greatly in keeping the
body cool. High collars, long sleeves, and high shoes are unhealth-
ful in warm climates and in summer. What objection to black shoes
in summer ? Patent leather ? Show how women dress more sensibly
in hot weather than men.

The kidneys are located on each side of the spinal col-
umn in the " small of the back " and extend slightly above

the level of the waist.
They are bean-shaped or-
gans about four incites long
(Fig. 26). The kidneys of
a sheep or ox closely re-
semble those of man. They
are outside of the perito-
neum (Fig. 99) and at-
tached to the rear wall of
the abdomen. A large
artery (12, colored Fig. 5)
goes to each kidney and
divides into many capilla-
ries which surround tubules
in the kidneys (Fig. 27).
The secretion, containing
nitrogenous impurities of
the blood, is continually being deposited in the tubules,
which take it to a funnel-shaped cavity at the inner edge
of the kidney (Fig. 26). From this cavity a white tube
called the ureter leads down to a storage organ in the
pelvis called the bladder.

FIG. 26. SECTION OF KIDNEY.

RA, renal artery; Py, pyramids surrounding
hollow space from which the ureter (U)
leads the secretion to the bladder.

THE SKIN

A.

TT>

1 '!<;. 27. PLAN OF A
URINARY TUBULE,
Tb, with artery A,
and V in p V.

Changes in Blood in the Kidneys.
The water holding the nitrogenous
waste varies in amount with the
amount of water drunk and with the
activity of the skin, being less in sum-
mer when the perspiration is great.
The lungs aid the skin and kidneys
in disposing, of superfluous moisture.
The kidneys have almost the entire
responsibility of relieving the body of
certain mineral salts and a white crys-
talline solid called urea. This is very
injurious if retained, causing headaches, rheumatism, and
other troubles.

THOUGHT QUESTIONS. Hygiene of the Skin.--l. What kind of a
scar is not affected by freckles or tan? 2. Can a scar on a negro be
white? 3. Does a scar on a child grow in size? 4. Why is heat
most oppressive in moist weather? 5. How do you account for the
shape and location of the usual bald spot? 6. How does the wearing
away of the outer cells of the epidermis contribute to the cleanliness of
the body? 7. Why does the palm of the hand absorb water more
rapidly than the back of the hand? 8. Is it more necessary for mental
workers to bathe often or change their clothes often? For physical
workers? 9. Is cotton or woolen clothing more liable to stretch or
shrink out of shape or size? To catch fire? To make the skin clammy
with moisture? To cost mor?.? To be eaten by moths?

Os frontale

Maxilla superior
Maxilla inferior

Clavicula

Humerus

Costae

Os parietale
Os temporale

Os- occipitis
Vertebrae

Scapula
Sternum

Radius

Ulna

Fibula

Metatarsus

Tarsus
Digiti pedis

FIG. 28. THE SKELETON.
28

CHAPTER III

THE SKELETON

Experiment \. (At home.) Is the Arch of the Foot Elastic?
Wet the foot in a basin of water and, while sitting, place the foot flat
upon a piece of paper. Draw the outline of the track. Repeat, but
stand with your whole weight upon the foot. Draw track. Con-
clusion? (Take sketches to school. Which sketch shows the flattest
foot?) Devise a method for measuring the length of the foot with
and without the weight of the body upon it. What difference? Con-
clusion ?

Experiment 2. Composition of Bone. - - Place a bone in a hot fire and
let it remain for three or four hours. It will keep its shape however long
you burn it ; but unless you handle it carefully when you take it out, it
will crumble to pieces. If not thoroughly burned, the bone will be
black from the carbon of the animal matter still left in it. Experiment 3.
Obtain a slender bone like the rib of a hog or the leg bone of a fowl,
and put the raw bone into a vessel containing strong vinegar or two
ounces of muriatic acid and a pint of water. Leave it there for four
days. When the bone is taken out, it can be tied into a knot. The
acid may be washed off, and the bone preserved in a bottle of alcohol
or glycerine.

Experiment 4. The Forms of Joints. --Obtain the disjointed bones
of a fowl or small mammal and place them one at a time in their
sockets and study the fit and motion of the joints.

Experiment 5. Pivot Joints. - - Through what fraction of a circle do
the pivot joints in the forearm and neck allow the hand and head to
rotate ?

Review Questions. - -Where are the bone cells? How does nour-
ishment reach them ? How has the mineral part of the bones been de-
posited? How long may bone cells live? Name animals with outside
skeletons. Inside skeletons. No skeleton.

Forms and Uses of Bones. - The three chief uses of bones
are protection, motion, and support. In order to fulfill
these purposes, the bones must have different sizes, shapes,
and positions. The bones are classed by shape, as long,

29

HUMAN BIOLOGY

Spongy
tissue,

: j C Marrow.

Compact
or dense
tissue

and compact near

- o

flat, and irregular. Those whose chief use is to protect are
broad and flat. The bones which furnish support are tJiick

and solid ; those designed to aid in
motion are long and straigJit. Including
six small bones in the ear, there are two
hundred and six bones g
in the adult skeleton.

Gross Structure of
Bones. The structure
of a long bone is shown
in Fig. 29. It has a
long, Jwllow sJiaft of
hard, compact bone, and
enlarged ends composed
of spongy bone. The
hollow in the shaft is
filled witJi yellow mar-
row, which is composed
of blood vessels and fat,
and aids in nourishing
thebone. Thelongbones
are found in the limbs
(Fig. 28). The ribs and
other flat bones and the

FIG. 29. -FEMUR, sawed irregular bones contain
lengthwise. The red no yellow marrow ; they

blood cells are formed .

in the red marrow of are spongy inside, and

the spongy part.

FIG. 30.

the surface. There is a red marrow in the FRONT VIEW OF

f . /T ^. RIGHT FEMUR.

cavities in the spongy parts 01 bones (r ig. 29).

New red blood cells are formed in tJiis marrow. The bones
have a close-clinging, fibrous covering composed of con-
nective tissue and blood vessels. It is called periosteum.

THE SKELETON

Chemical Composition of Bone. Experiments (2 and 3)
show that the bones contain a mineral or earthy substance,
which makes them hard and stiff, and ,,
a certain amount of animal matter,
called gelatine, which binds the min-
eral matter together and makes the
bones tough and somewhat elastic.
The fire burned out the animal matter rj
of the first bone, and the acid dissolved
out the mineral matter of the second
bone. The mineral matter is cJiiefly
lime, and makes up about two thirds of
the weight of the bone. (Why is more
mineral than animal matter needed ?)
The animal gelatine is a gristly sub-
stance. As the body grows old, the
animal matter of the bones decreases,
and they become lighter. They are L.
more easily broken and do not heal so
readily as the bones of young persons.

The skeleton is subdivided into the
bones of the head, trunk, and limbs.
The bones of the trunk are those of
the spine, the chest, the shoulder blades,
collar bone, and hip bones.

The spinal or vertebral column is
made up of twenty-six bones (Fig. 31).
It is the axis of the human skeleton,
to which all other bones are directly
or indirectly attached. Animals with FIG. 31. --VERTEBRAL
inside skeletons have this column, and CoLUMN - Side view -
are called vertebrates. Fish, reptiles, birds, beasts, apes,
and man are vertebrates. The spine, as this column is some-

CLJ

HUMAN BIOLOGY

times called, is not only the main connecting structure and
support of the body, but it forms a channel through which
passes the spinal cord.

Fig. 32 shows a vertebra, or one of the bones that compose the
column. The three projecting points or processes are for the attachment

of ligaments and muscles. The main body
of each vertebra is for supporting the
weight transmitted by the column above.
Just behind this thick body is a half ring
(Fig. 32), which with the half rings on
the other vertebrae form the channel for
the spinal cord. Between the vertebras
are thick pads of gristle, or cartilage, which
act as cushions to prevent jars, and by
compression allow bending of the spinal
column in all directions.

The Chest (see Fig. 75). The
twelve pairs of ribs are attached

FIG. 32. SIDE AND UNDER to the spinal column behind, and
VIEW OF A VERTEBRA. ,

extend around toward the front of

the body, somewhat like hoops. The first seven pairs,
called true ribs, are attached directly to the flat breastbone,
or sternum. Each of the next three pairs, called false ribs,
is attached to the pair above it. The last two pairs,
called floating ribs, are free in front.

The Shoulder Girdle. - - The collar bones (Fig. 28) can be
traced from the shoulders until they nearly meet on the
breastbone at the top of the chest. The collar bone is
shaped like the italic letter/"/ it helps to form the shoulder
joint and holds the shoulder blade out from the chest that
the motions of the arm may be free.

The flat, triangular shoulder blade (Fig. 75) can be felt
by reaching with the right hand over the left shoulder. It
spreads over the ribs like a fan. Its edges can be made
out, especially if the shoulder is moved while it is being

THE SKELETON

33

Parietal

Frontal

Ethmoid
nasal

Malar

Occipital

FIG. 33. HUMAN SKULL,
disjointed.

felt. The high ridge which runs across the bone can be
felt extending to the top of the shoulder.

The Pelvic Girdle. - The edges of the hip bones can be
felt at the sides of the hips (Fig. 28). The hip bones,
with the base of the spine,
form a kind of basin called
the pelvis.

The skull (Fig. 33) rocks,
or nods, on the top vertebra.
It consists of the cranium, or
brain case, and the bones of
the face. The shapes and
names of the bones of the
skull are shown in Fig. 33.

Adaptations of the Skull
for Protection. - - Its arched
form is best for resisting pressure and turning aside blows.
Like all flat bones, the skull has a spongy layer of bone
between the layers of compact bone forming the outer and
inner surfaces ; hence it is elastic and not easily cracked.
The nose, brow, and cheek bones project around the eye
for its protection. The delicate portions of the ear are
embedded in the strongest portion of the skull. The
branches of the nerves of smell end in the lining of the
bony nasal chambers. The spinal cord rests securely in
the spinal canal.

The arms and legs have bones that closely correspond to
each other. The Latin names of these bones, as well as
of all the other bones, are given in Fig. 28. There are
30 bones in each arm and 30 in each leg (Fig. 34).
Here is a list of the bones of the arm, followed by the
names in brackets of the corresponding leg bones : upper
arm bone [thigh bone], 2 forearm bones [shin bone and

34

HUMAN BIOLOGY

splint bone], 8 wrist bones [7 ankle bones], 5 palm bones
[5 bones of instep], 14 finger bones [14 toe bones]. The
shin bone is the larger bone between knee and ankle.

The long, slender splint bone and the
shin bone are bound side by side.

Differences between Arm and Leg.
There is a saucer-like bone, called the
kneecap, embedded in the large liga-
ment which passes over each knee.
There is no such bone in the elbow.
There is one less bone in the ankle
than in the wrist, hence there are the
same number of bones in the arm and
leg. The shoulder joint is more freely
movable than the hip joint. The fin-
gers are longer and more movable than
the toes; the thumb moves far more
freely than the big toe. The instep is
much stronger than the palm ; for each
instep must support, unaided, the
weight of the whole body at each step,
with any other weight that the person
may be carrying. The palm is nearly
flat, but the instep is arched to prevent
jars. When the weight of the body is
thrown on the foot at each step, the top of the arch is
pressed downward, making the foot longer than before.
The arch springs up when the weight is removed (Exp. i).

ILLUSTRATED STUDY. The Shapes of Bones. Write Z,, F, or 1
after these names (see Fig. 28, etc.). according as the bones are long,
flat, or irregular : face, cranium, vertebra, hip, rib,
bone, collar bone, shoulder blade, upper arm bone,
arm bones, wrist, palm, fingers, thigh bone,
splint bone, ankle, instep, toes, kneecap.

FIG. 34. BONES OF
ARM AND LEG.

breast-
lower
shin bone.

THE SKELETON 35

Structure of Joints. The meeting of two bones forms
a joint (Exp. 4). Some of the joints are immovable.
The skull bones join in zigzag lines called sutures, formed
by the interlocking of sawlike projections (Fig. 35). These
immovable joints are necessary for the protection of the
brain, which is the most delicate of the organs. The brain
attains almost its full size by the seventh
year of life ; its bony case needs to grow
very little after that. The joints of the
pelvis are also immovable. All movable
joints have two cartilages, and as the bones
turn, one cartilage slips over the other.
There is an intermediate class of joints
found between the vertebrae and where the
ribs join the breastbone. These joints de- FIG. 35. SUTURES
pend for their motion upon the flexibility OF SKULL -
and compressibility of their cartilages. They are called
mixed, or elastic, joints, and allow slight motion. Such a
joint has only one cartilage.

Kinds of Movable Joints. The movable joints are found
chiefly in the limbs. When one end of the bone is rounded
and fits into a cuplike hollow, the joint allows motion in
all directions, and is known as a ball-and-socket joint. The
hip joints and shoulder joints are examples. A hinge joint
allows motion in only two (opposite) directions ; for exam-
ple, the to-and-fro motion of the elbow. A pivot joint
allows a rotary motion ; examples, the first vertebra on
the second, one bone of forearm upon the other. A glid-
ing joint consists of several bones that slide upon one
another, as at the wrists and ankles.

The Four Features presented by a Movable Joint (Fig.
36). If not held in place, the bones would slip out of
their sockets, hence there are ligaments, or tough bands,

HUMAN BIOLOGY

to bind the bones together. Sudden jolts would jar the
bones and injure them; shocks are prevented by a layer

of elastic cartilage over the
end of each bone. The mov-
ing of one bone over another
in bending a joint would wear
the bone with friction un-
less the cartilages were very
smooth and lubricated with a
fluid called the synovial fluid.
The synovial fluid would be
constantly escaping into the
surrounding tissues except for
the collarlike ligament called

Joint
cartilage

L. Joint
capsule

O! Synovial

membrane

FIG. 36. DIAGRAM OF A JOINT.

the capsule, which surrounds the joint and is attached to
each bone entirely around the joint (Fig. 36).

THOUGHT QUESTIONS. The Kinds of Joints. --Write B, H, G, E,
P, or /after these names according to the kind of joint (ball-and-socket,
hinge, gliding, elastic, pivot, immovable) : between bones of skull,
head nodding, head turning, vertebrae, lower jaw, ribs to
breastbone (Fig. 75), shoulder, elbow, wrist, fingers,
hip, knee, ankle, toes.

Growth of Bones.- -The blood vessels pass into the bones from the
periosteum. If the periosteum is removed, the larger blood vessels are
taken away and the bone beneath it perishes. If the underlying bone is
removed and the periosteum left, the bone will be replaced. A curious
proof of the active circulation in the bone is furnished when madder is
mixed with the food of pigs. In a few hours the bones become a darker
pink than usual ; and if the madder is fed to the pigs for a few days,
their bones become red. A child grows in height chiefly during three
or four months in spring and summer; but its body broadens and
becomes heavier during autumn.

Health of the Bones. - -It is plain that a strong and free circulation
of pure blood contributes to the health and strength of the bones ; good
food and pure air make pure blood. Cases of " delayed union," or
slow mending of broken bones, occur more often with intemperate than
with sober people. This is because the vitality of the bone cells has

THE SKELETON

37

been weakened by the use of alcohol. Many surgeons dislike to operate
on an old drunkard.

Posterior Curvature of the Spine. - -The spine (see Figs. 28, 31) has
two backward curves (opposite chest and hips) and two forward curves
(at loins and neck). The deformity called posterior curvature is chiefly
an exaggeration of the upper posterior curve. Round shoulders is the
slightest, and hunchback the most marked, degree of this
deformity. Causes : i, bending over the work while either
standing or sitting ; 2. slipping down in the seat, as in Fig-
ure 51 ; 3, working habitually with the work low in front,
as reading and writing at too low a desk (Fig. 49), or bend-
ing over while hoeing, sitting on the floor (Japanese and
Chinese) ; 4, weak muscles in the back ; 5, wearing shoes
with high heels; 6, binding the ribs down with tigJit cloth-
ing; 7, walking with the head drooped forward or the
chest flat ; 8, wearing suspenders without a pulley, or lever,
at the back ; 9, carrying the hands in the pockets. (Swing
the arms to keep the hands out of the pockets and break
the habit) : 10, wearing a coat or vest that is tight at
the back of the neck. This deformity is brought about by
stretching t /i e ligaments at the back side of the spine, and
by compressing the cartilages until tJiey become wedge-
shaped, with the thin part of the wedge in front. The
flexibility of the spine is a great advantage, but it in-
creases the risk of deformity. One of the most serious
evils of posterior curvature is a flat chest and restricted
breathing.

Lateral Curvature of the Spine. -- A perfect spine curves
to neither side (Fig. 47), but is perfectly erect. The least
habitual lateral curvature is deformity. Causes: i, writing
at a desk that is too JiigJi ; 2, habitually carrying a book,
satchel, or other weight in the same hand ; 3. carrying the
head on one side (Fig. 46) ; 4, habitually standing with the
weight on the same foot ; 5, a certain defect of vision
(astigmatism. Chap. IX).

To overcome Spinal Deformities.- -The work, or the
manner of doing the work, should be so changed as to give
extra labor to the neglected muscles. Avoid the habits
mentioned above as causing deformity. Sit and stand in
the manner described in the next paragraph. Sleeping on
the back upon a hard mattress without a pillow tends to ^ ut stra ined
cure posterior curvature and flat chest. and stiff.

FIG. 37. -
INCORRECT
POSTURE.

'
CORRECT

HUMAN BIOLOGY

The correct position in standing is : chest forward, chin in, hips back
(Figs. 38, 39). To sit correctly, sit far back in tJie chair (Figs. 60,
61, 62) with the body erect and balanced. In youth the bones are soft
and growing ; they will readily grow into perfect shape, and will almost
as readily grow deformed.

Sprains. -- Immerse the part in hot water for half an hour, then
bandage to keep the part at rest. Use the litnb as little as possible. It
may be necessary for a physician to apply a plaster dressing to a very
bad sprain where the ligament is torn from the bone.

Broken Bones. To prevent bone from cutting flesh and skin, do not
move the person until a temporary splint has been provided by tying
sticks or umbrellas around the limb with handkerchiefs.

PRACTICAL QUESTIONS. The Skeleton. --1. What kind of a chair
back causes one to slide forward in the seat? 2. What fault in sitting
is made necessary by using a chair with so large a seat that the front
edge strikes the occupant behind the
knee? 3. Why is the shoulder more

often dislocated than
the hip? 4. High pil-
lows may cause what
deformity? 5. Find
three bones in the
body not attached to
other bones. Find
twenty-five bones at-
tached to other bones
by one end only (Figs.
28 and 39). 6. What
deformities may result
from urging a young
child to stand or walk ?
7. Which bone is
most often broken by
falling upon the shoul-
der? 8. Where in
bones is fat stored for
FIG. 39. THE HUMAN SKELETON IN ACTION. future use? 9. Liga-
ments grow very slowly. Why is recovery from a sprain often tedious?

CHAPTER IV

THE MUSCLES

IT has already been stated that there are at least two
muscles attached to a bone to move it in opposite direc-
tions. Since there are two hundred and six bones, you
are not surprised to learn that to move the bones and
accomplish the various purposes just stated, there are
five hundred and twenty-six (526) skeletal muscles.

Two Kinds of Muscles. - - All muscles are controlled by
means of the nervous system. Some of them are directed
by parts of the brain that work consciously ; others are
controlled by the spinal cord and the parts of the brain
that work unconsciously. Those of the first kind are
usually controlled by tJie will, but they sometimes act invol-
untarily. They are called voluntary muscles. They move
the bones and are located in the limbs and near the surface
of the trunk (Fig. 44). The other kind of muscles are
never controlled by tJie will, and are called involuntary
muscles. We cannot cause them to act, nor can we prevent
them from acting. They contract more slowly than the
voluntary muscles. Most of them are tubular and found
in the cavity of the trunk. The involuntary muscles belong
to the internal organs, and relieve the will of the responsi-
bility and trouble of the activity of these organs ; other-
wise, the mind would have no time for voluntary actions.

Gross Structure of Voluntary Muscles. A beefsteak is
seen to be chiefly red, although parts of it are white or
yellowish. The white or yellowish flesh is fat ; the red,

39

HUMAN BIOLOGY

FIG. 40. - - MUSCLE BUNDLES bound to-
gether by connective tissue sheaths.

lean flesh is voluntary
muscle. If a piece of beef
is thoroughly boiled, it
may be easily separated
into bundles the size of
large cords. These bun-
dles may, by the use of
needles, be picked apart
and separated into thread-
like fibers (Fig. 40).
Microscopic Structure of Muscles. These threadlike
fibers may, under a magnifying glass,
be separated into fine strands called
fibrils. TJiese last are the true muscle
cells ; they are shown by the micro-
scope to be crossed by many dark lines
(Fig. 48). Hence voluntary muscles are
called striated or striped muscles. Pro-
longed boiling and patient picking with
a needle are needed to dissect muscle,
because the bundles are held together
by thin, glistening sheets of connective
tissue by which they are surrounded.
This connective tissue surrounds and
holds in place the separate fibers of each bundle (Fig. 40).

The fibrils of invol-
untary muscles are
spindle-shaped (see
Fig. 42). There are no
cross lines on the fibrils ;
hence involuntary mus-
cles are called smooth
FIG. 42. INVOLUNTARY MUSCLE CELLS

(or fibers). or 2instriped imiscles.

FIG. 41. --Two MUS-
CLE FIBERS OF
HEART.

THE MUSCLES

The heart fibers are exceptional ; they are the only invol-
untary muscle fibers that are striped (Fig. 41).

THOUGHT QUESTIONS. Classification of Some of the Muscles.
Copy the following list and mark / for involuntary and V for voluntary
after the appropriate muscles.

Muscles for chewing. Muscles of gullet. Muscles of the heart.
Muscles that move arms. Muscles for breathing. Muscles in the skin
that cause the hair to stand on end. Muscles that move eyelids.
Muscles that contract pupil of eye. Muscles for talking. Muscles
that contract and expand the arteries (in blushing and turning pale).
Muscles that move eyeball. Muscles that give expression to the face.

Tendons. The connective tissue ivJiich binds the fibers of

muscles into bundles, and forms sJicatJis for the bundles,
extends beyond the ends of tJie muscles and unites to form
tough, inelastic white cords called tendons. Some muscles
are without tendons, and are attached directly to bones.
Study the figures and find examples of this (see Figs.
44, 75). To realize the toughness of tendons, feel the
tendons under the bent knee or elbow, where they feel
almost as hard as wires. The tendons save space in places
where there is not room enough
for the muscles, and permit the
bulky muscles to be located where
they are out of the way. Wher-
ever the tendons would rise out of
position when a joint is bent, as
at the wrist and ankle, they are
bound down by a ligament.

Arrangement of Voluntary Mus-
cles. Circular muscles, called
sphincter muscles, are found around
the mouth and eyes. Muscles that
extend straight along the limb either bend it and are called
flexors, or straighten it and are called extensors. Most of

FIG. 43. (For blackboard.)
BICEPS relaxed and contracted.

42 HUMAN BIOLOGY

the voluntary muscles are arranged in pairs and cause
motion in opposite directions ; they are said to be antago-
nists. The biceps (Fig. 43) bends the arm. Its antagonist
is the triceps on the back of the arm. By feeling them
swell and harden as they shorten, locate on your own
body the muscles mentioned in Fig. 44.

How a Muscle grows Stronger ; its Blood Supply.
Nature has provided that any part of the body shall receive
more blood when it is working than when it is resting.
WJien it works the hardest, the blood tubes expand the most
and its blood supply is greatest. So whenever a muscle is
used a great deal, an unusual amount of material is carried
to it by the blood, the cells enlarge and multiply, and the
muscle grows. The walls of the capillaries are so thin that
the food which is in the blood readily passes from them to
the muscle. Because of the oxidation taking place, a work-
ing muscle is warmer than one at rest. By use a muscle
grows large, firm, and of a darker red ; by disuse, it be-
comes small, flabby, and pale. But if muscles are worked
too constantly, especially in youth, their cells do not have
time to assimilate food and oxygen, and their growth is
stunted.

Unless the meal has been a very light one, vigorous
exercise should not be taken after eating, as the blood will
be drawn from the food tube to the muscles and the secre-
tion of the digestive fluids will be hindered. Persons
whose entire circulation is weak may find that light exercise
after a meal, such as walking slowly, may help circulation
and digestion.

Why the Muscles work in Harmony. WJien a boy throws
a stone, almost every part of the body is concerned in tJie
action. His arms, his legs, his eyes, the breathing, the
beating of the heart, are all modified to assist in the effort.

Illustrated Study of Muscular Function

Draw a dotted line from each function mentioned on margin to the muscle
or muscles having that function.

Bows the head?

Draws shoulder back?

Straightens the
elbow?

Straightens the fingers?

Swings leg outward?

Bends the knee?

Straightens the knee?

Crosses the leg?

Straightens toes?

Lifts the whole arm outward
and upward?

Draws who'e arm downward
and forward?

Bends the elbow?

Bends the fingers?

Raises the body on the
toes?

Raises toes?

FIG. 44. SUPERFICIAL MUSCLES AFTER THE STATUE OF "THE DIGGER

(Lami).

43

44

HUMAN BIOLOGY

As the boy wills to throw the stone, nerve impulses are
sent to all the organs that can assist, and they are excited
to just the amount of action needed.

The Nerve Impulse and the Contraction. - - Each nerve
that goes to a muscle is composed of many fibers ; the
fibers soon separate and go to all parts of the muscle,
and each muscle fiber receives its nerve fiber (see Fig. 45).

In the brain each fiber is
stimulated at once, and all
the fibers shorten'and thicken
together. This change is
spoken of as contraction ; but
since the muscle does not be-
come smaller, the word may
be misleading. When the
muscle shortens, it thickens
in proportion and occupies as
much space as it did when
relaxed.

Where does Muscular En-
ergy come from? - - The nerve
does not furnish tJie energy
which the muscle uses when

b

FIG. 45. MOTOR NERVE FIBERS,
ending among fibrils of voluntary
muscle. Compare with Fie. 48. , TV / //

contracting. 1 he muscle cells

have already stored up energy from the food and oxygen
brougJit to them by the blood, and the process called oxida-
tion sets free the energy. Activity of muscle may increase
the carbon dioxid output fivefold. Mental work has prac-
tically no effect upon it.

How a Muscle stays Contracted. - -The muscle relaxes at
once after contraction ; and in order to keep it contracted,
nerve impulses must be sent in quick succession, causing
in fact many contractions ; the effect of this is sometimes

THE MUSCLES

45

visible, as the trembling of the muscle. Figure 47 shows
an easy standing posture.

What causes Fatigue. - - Fatigue or exhaustion is due to
the using up of the living material in the nerve cells and
muscle cells by oxidation. Rest is necessary to give cells
opportunity to repair themselves. Why is it less fatiguing
to walk for an hour than to stand perfectly still for ten
minutes ?

FIG. 46. IMPROPER POSITION;
causes spine to curve to side ;
raises one hip and shoulder
above the other.

FK;. 47. P>KST POSITION;
chest is free to expand,
and weight is easily shifted
from one foot to other.

Degeneration of Muscles begins with habitual disuse.
We dare not furnish a substitute for the work of a muscle,
if we wish the muscle to remain sound. A belt or a stay
at the waist will cause the muscles of the trunk to become
flabby and the abdomen to relax and protrude.

How Muscular Activity helps the Health. - - Life is
change, stagnation is death. Muscular activity uses up the

4 6

HUMAN BIOLOGY

food, g ives a good appetite, and sets the digestive organs to
work ; it uses up the oxygen and sets the lungs to work ;
but most of all, every contraction of a muscle helps the blood
to flow. As a muscle contracts, it presses upon the veins
and lymphatics, and, by this pressure, forces the blood

and lymph along (Fig.
48). In any ordinary
activity, dozens of mus-
cles are being used.
That the effect upon the
circulation is very pow-
erful, is shown by the
rosy skin, deep breath-
ing, and rapid heart beat.
The many benefits of an
active circulation of the
blood and lymph will
be discussed in the next
chapter See page 67.
A grave danger from athletics is that of developing the
muscles, including the heart, to an enormous extent by
training ; then ivhen training ceases the muscles undergo
fatty degeneration from disuse. Heart disease and other
diseases may follow. Many athletes die young, killed by
trying to turn their bodies into mere machines for run-
ning, boxing, or rowing, instead of living complete lives.
The athletic ideal is not the highest ideal of health ; gen-
eral activity, resembling the occupations of hunting and
farming by which the early race supported itself, is
best for health. Many kinds of factory work use only
one set of muscles. The savage did not lead a monoto-
nous life, and monotony is bad for both muscles and
nerves.

FIG. 48. CAPILLARIES among fibers of
voluntary (cross striped) muscle. (Peabody.)

THE MUSCLES

47

Advantages of Work and
Play over Gymnastic Exer-
cises. The interest that
comes from doing something
useful, makes muscular exer-
tion doubly beneficial to the
health. The lifting of dumb-
bells, Indian clubs, and pulley
weights, and letting them
down again, tends to become
very irksome, even though
done with the knowledge that
the exercise will benefit the
health. Useful labor and
games place definite objects in
view and do not require so
great an effort of the will nor
exhaust the nerves so much as
mere exercise. The interest
in the work or the game serves
to arouse all the nerves and
muscles to work in harmony.

An Advantage of Gymnas-
tics over Work and Play. -
Gymnastics can furnish anv

j *

required variety of exercises
and can develop exactly the
muscles that need develop-
ment and leave those idle that
have become overdeveloped by
doing constantly one kind of
work or playing continually
the same game. The deform-
ity of a flat chest (and round
shoulders which always ac-
company it) does not so often
indicate a weak chest or small
lungs as it indicates weak or
relaxed muscles of the back
and the habit of sitting in a
relaxed position at work
(Figs. 49, 50, 51). Gymnas-

FIG. 49. DESK TOO Low. (Jegi.)

FIG. 50. CORRECT POSITION.

FIG. 51. SLIPPING DOWN IN SEAT.

48 HUMAN BIOLOGY

*

tic exercise is not wholly an artificial custom. Cats stretch themselves,
stretching each leg in succession ; many animals gambol and play. A
gymnastic drill, taken to music and with large numbers of pupils in
the drill, is interesting as work or play, and should not be neglected for
any study, however important.

Environment of Early Man and Modern Man. --A well-developed
man of one hundred and fifty pounds weight should have sixty pounds
of muscles. The proportion is often different in the puny bodies of the
average civilized men, such as clerks, merchants, lawyers, and other
men with sedentary occupations ; their bodies are as likely to be lean
and scrawny or fat and flabby as to be correctly proportioned. Why
does a normal man have sixty pounds of muscles instead of twenty
pounds of puny strings such as would have sufficed for a clerk, student,
or a writer? This is because, in his native condition, he had to seek
his food by roaming through the forest, contending with wild beasts
or with other savage men, often traveling many miles a day, climbing
trees, etc.

Too Rapid Change of Environment ; Destructive Tendencies of Civil-
ization. --// is impossible for the human body to change greatly in a few
hundred years. The body of man served him for many ages for the
manner of life outlined above. It was suited for these conditions, and
the muscles and the organs that support them cannot accommodate
themselves to changed conditions in a few generations. It has only
been a few hundred years since the ancestors of the Britons and Ger-
mans, for instance, were running wild in the German forests, clad in the
skins of wild beasts. Yet civilized man lets his muscles fall into disuse,
he takes a trolley car or horse vehicle to go half a mile, an elevator to
climb to the height of thirty feet. He neglects all his muscles except
those that move the tongue and the fingers of the right hand. He
never makes enough exertion to cause him to draw a deep breath, and
his lungs contract and shrivel. He seldom looks at anything farther
than a few inches frpm his nose, and his eyes become weak. At the
same time that he neglects his muscles and his lungs, he overworks his
brain and his stomach ; yet he expects his body to undergo the rapid
changes to suit the demands of his life. Such rapid changes in the
human race are impossible. A man that does not see that sound health
is the most valuable thing in the world, except a clear conscience, is in
danger both of wrecking his own happiness and of failing in his duty
to others.

THOUGHT QUESTIONS. Shoes. 1. What the faults of shoes may
be in size ; shape; sole; heel; toe; instep. 2. Name deformities re-
sulting to skin of foot ; nails ; joints ; arch ; ankle ; spine. 3. State effects

THE MUSCLES 49

of uncomfortable shoes on muscular activity : mind and disposition.
4. State effect of aversion to walking on muscles ; circulation. 5. If
a shoe is too loose, it slips up and down at the heel and chafes the skin
there ; if too tight, there is pres-
sure on the toes, which causes a
corn or ingrowing nail. Have
your shoes been correct, or have
they been too loose or too tight ?

According to this test, what pro-

FIG. 52. ARCH OF FOOT. It forms an
portion of people wear shoes that elastic springi

are too tight? 6. How many

sprained ankles have you known among boys; girls? 7. Why is it
that people who grow up in warm climates have high, arched insteps,
and short, broad, elastic feet, but people of the same race who pass their
childhood in cold climates often have long narrow feet with low arches
and sometimes have the deformity called " flat foot " ?

Instinct as a Guide for using the Muscles. - - The instinctive feeling
called fatigue tells us when to rest. There is also a restless, uneasy
feeling that conies over a normal human being ic/icn confinemejit and
restraint of the muscles have reached an unhealthy limit. This feeling
should not be repressed for long at a time. Many, ruled by avarice,
ambition, interest in sedentary work, a silly notion of respectability, or
a false conception of duty, have repressed this feeling and have lost
it. There is then a feeling of languor, and a disinclination to the very
activity which health demands. An unheeded instinct is as useless as
an alarm clock that has been habitually disregarded.

Exercise and Climate. --In our warmest states and in the tropics,
one hour's vigorous physical labor a day, combined with the ordinary
activities of life, will keep a person in good condition. In the colder
states, muscular exertion for several hours is needed daily.

Complete Living. - - Numberless people have devoted themselves to
an intellectual occupation, and planned to keep their bodies sound by
gymnastics and special exercises. Because of the monotony of exer-
cises, they are soon given up in nearly every instance. The safest -way
is never to allow all the energies to be devoted to a one-sided occupation,
but so to plan one^s life and work that a part of the time is devoted to
some physical work, whether it be in a garden, workshop, or orchard ;
in walking a long distance to the office : at bookbinding, cooking, wood
carving, or any one of various other useful occupations. The result of
manual training shows that not only strength of body, but strength of
mind, is promoted by physical labor. Problems of war and of the chase
kept active both the body and mind of the savage. Hence he led
E

50 HUMAN BIOLOGY

a more nearly complete life than his civilized descendants, and his body
was strong accordingly. We should admit the hopelessness of having
permanent good health without muscular activity and should determine
that muscular exertion shall be as much a habit and pleasure as eating
and sleeping.

Alcohol and Muscular Strength. Benjamin Franklin, one of the
wisest and greatest of Americans, was a printer when he was a young
man. In his autobiography he gives an account of his experience as a
printer in London. He says: "I drank only water; the other work-
men, fifteen in number, were great drinkers of beer. On occasion I
carried up and down stairs a large form of types in each hand, when
others carried but one in both hands. They wondered to see, from this
and several instances, that the Water-American, as they called me, was
stronger than themselves, who drank strong beer. My companion at
the press drank every day a pint before breakfast, a pint at breakfast
with his bread and cheese, a pint between breakfast and dinner, a pint at
dinner, a pint in the afternoon about 6 o'clock, and another when he had
done his day's work. I thought it a detestable custom, but it was neces-
sary, he supposed, to drink strong beer that he might be strong to labor. 1 '

EXERCISES IN WRITING.- -The Right and the Wrong Way to ride
a Bicycle. Pay Day at a Factory. A Graceful Form : how Acquired ;
how Lost. A Drinking Engineer and a Railway Wreck.

PRACTICAL QUESTIONS. 1. Can we always control the voluntary
muscles? Do we shiver with the voluntary or involuntary muscles?
2. If a man had absolute control over his muscles of respiration,
what might he do that he cannot now do? 3. Why is one who uses
alcoholic drinks not likely to be a good marksman? 4. Why should a
youth who wishes to excel in athletic contests abstain from the use
of tobacco? 5. Is there any relation between the amount of bodily
exertion necessary for a person's health and the amount of wealth or
the amount of intelligence he possesses ? 6. Can you relax the chewing
muscles so that the lower jaw will swing loosely when the head is
shaken? Can you relax your arm so that it falls like a rope if another
person raises it and lets it fall? 7. The average man has sixty pounds
of muscle and two pounds of brain ; one half of the blood goes through
the muscles and less than one fifth goes through the brain. What
inference may you draw as to the kind of life we should lead? 8. Why
is a slow walk of little value as exercise? 9. How can we best prove
that we have admiration and respect for our wonderful bodies?
10. Why is the ability to relax the muscles thoroughly of great benefit
to the health? How is this ability tested ? (Question 6.) 11. Why is
it as correct to say that the muscles support the skeleton as the reverse ?

1. Head arteries

(carotid).

2. Nameless arteries

(innominate).

3. Collar bone (sub-

clavian) artery.

4. Great bend of the

aorta.

t8. Ascending vena
cava.

19. Vein from liver

(hepatic).

20. Vein from stom-

ach (gastric).

21. Vein from

spleen.

i

5. Pulmonary

arteries.

6. Thoracic aorta.

7. 10. Abdominal

aorta.

8. Artery to liver

i hepatic). :

9. Artery to spleen ?

(splenic).

11. Artery to in-

testine
(mesenteric).

12. Artery to

kidney
(renal).

13. Descending

vena cava.

i t. Nameless vein
(innominate,
15 and 16 be-
fore branching).

15. Collar bone vein
(subclavian).

J 6- Jugular vein.

17. Pulmonary vein.

22. Vein from
intestine.
23 Vein to liver

(portal).
24. Vein from
kidney.

25. Right auricle.
R 26. Left auricle.

27. Right ven-

tricle.

28. Left ventri-

cle.

29. Thoracic

duct.

30. Stomach.

31. Spleen.

32. Liver.

33. Kidneys.

34. Duodenum.

35. Ascending colon,

36. Descending

colon.

37. Lymphatic glands
of mesentery.

COLORED FIGURE 5. DIAGRAM OF CIRCULATION.

CHAPTER V

THE CIRCULATION

Experiment i . Anatomy of Mammalian Heart. Get a sheep's
or beef's heart from the butcher. Get the whole heart, not simply the
ventricles (as usually sold). Note the blood vessels, four chambers,
thickness of di fife re nt walls, valves, cords, openings.

Experiment 2. Does Gravity affect the Blood Flow? --Hold the
right hand above the head for a few minutes. At the same time let the
left hand hang straight down. Then bring the hands together and see
which is of a darker red because of containing more blood. Now re-
verse the position of the hands for a few minutes, and find whether the
effect is reversed. (Entire class.)

Experiment 3. Study of Human Blood. --Examine a drop of blood
under the microscope, first diluting it with a little saliva. See Fig. 60.

Experiment 4. The Circulation in a Frog. - -Wrap a small frog in a
moist cloth, lay on a slip of glass, place under the microscope, and
study the circulation in the web of its foot.

Experiment 5. (Entire class.) Effect of Exercise upon the Pulse.
Tap a bell as the second hand of a watch begins a minute and let the
pupils count the pulse at the radial artery on the wrist above base of
thumb. Repeat standing, or after gymnastics or recess. Result?

Experiment 6. The Action of the Valves in the Veins. --Place the
tip of the middle finger on one of the large veins of the wrist ; with
the forefinger then stroke the vein toward the elbow so as to push the
blood from a portion of it, keeping both fingers in place. The vein
remains empty between the fingers. Lift the finder nearer the heart
and no blood enters the vein ; there is a valve above which holds it back.
Lift the other finger and the vein fills instantly. Stroke a vein toward
the hand, and notice that the the veins swell up into little knots where
the valves are. Stroke in the reverse direction. Result ?

Experiment 7. Finding the Capillary Pressure. This is found by
pressing a glass plate or tumbler upon a red part of the skin. When
the skin becomes pale the capillary pressure is counterbalanced.

Experiment 8. Emergency Drill. Let one pupil come forward, mark
with blue chalk or pencil the position on his arm of a supposedly cut
vein. Let another pupil use means to stop the imagined blood flow.

51

HUMAN BIOLOGY

Experiment 9. Let another pupil stop the flow from an imaginary cut
artery marked red. See text. Experiment 10. In a case of nose bleed
do not let pupil lean over a bowl. (Why?) Cause him to stand
rather than lie. (Why? See Exp. 2.) Apply cold water to contract
arteries to nose, also have pupil hold a small roll of paper or a coin
under upper lip (to make muscular pressure on arteries to nose).
Experitnoit 11. Let one pupil treat another for a bruise (seep. 62).
Experiment 12. Emergency drill, restoration from fainting (see p. 57).

The Cells have a Liquid Home. - - The cells in the body of man, like
the ameba, live in a watery liquid. This liquid is called lympJi. The
cells cannot move about as the ameba does to obtain food, so the
blood brings the food near them and it soaks through the blood tubes
into the lymph spaces next to the cells (see colored Fig. 3). The
ameba gives off waste material into the water ; the cells of the body
give it off into the lymph to be carried off by the circulation. The
blood, then, has two functions : (i) to take nourishment to the tissues ;
(2) to take away waste material from them.

The Organs of Circulation. - These are the Jieart, which
propels the blood ; the arteries, which take blood away

from the heart ; the veins, which take
the blood back to the heart ; and the
capillaries (Fig. 53), which take the
blood from the arteries to the veins.

The heart is a cone-shaped organ
about the size of its owner's fist. It
lies in a diagonal position behind the
breastbone, with the small end of the
cone extending toward the left. The
smaller end (Exp. i) taps or beats
against the chest wall at a point be-
tween the fifth and sixth ribs on the left side. The
breastbone and ribs protect it from blows. An inclosing
membrane called the pericardium secretes a serous fluid
and lessens the friction from its beating.

Why the Heart is Double. - - There must be a pump to move
the impure blood from the body to the lungs to get oxygen

FIG. 53. CAPILLARIES,
connecting artery (l>)
with vein (a}.

THE CIRCULATION

53

from the air, and there must be another pump to send the
pure blood from the lungs back to the body. Hence there
are two pumps bound together into one heart, beating at
the same time like two men keeping step, or like two car-
penters keeping time with their hammers. There are
valves in the heart, as in other pumps. These valves are
so arranged that when any part of the heart contracts and
forces the blood onward, the blood cannot return after that
part of the heart relaxes. Are the pumps placed one
behind the other? Or is one above the other? Neither;
they are side by side, with a
fleshy partition between them
(Fig. 54). The pump on the
right moves the impure blood
from the body to the
lungs, and the one on the
left moves the pure blood
from the lungs to the body.
There is no direct connection
between the right and left sides
of the heart.

To trace one complete circuit
of the blood (Fig. 54), let us
begin with the blood in the
capillaries of the outer tissues,
such as the skin or muscles.

pulmonary
veins

pulmonary
veins

The blood goes through small

FIG. 54. DIAGRAM OF HEART.

Notice the two dark spots in the right
auricle, and four dark spots in left
auricle, where the veins enter. Does
the aorta pass in front of, or behind,
the pulmonary artery?

veins which unite into two
large veins, through which it
enters the receiving chamber, or right auricle, goes through
the tricuspid valve into the expelling chamber, or right
ventricle, then through a semilunar valve into the pulmo-
nary artery leading to the lungs. Becoming purified while

54

HUMAN BIOLOGY

passing through the capillaries of the lungs, the blood goes
throngJi tJie pulmonary veins to the left auricle (Fig. 54),
then through the bicuspid or mitral valve, to the left ventri-
cle, whence it is forced through a semilunar valve into the
largest artery of the body, called the great aorta (Fig. 54).
Thence it goes to the smaller arteries, and then to the capil-
laries of the tissues in general, thus completing the circuit

vm.

v.s

vm..

FIG. 55. THE LEFT SIDE OF HEART (plan), showing the left ventricle at the mo-
ment when relaxing and receiving the blood from the auricle; and the same at
the beginning of contraction to send blood into aorta. Notice action of the valve.

Structure of Veins and Arteries. Seen under the micro-
scope the arteries and veins show that they are made of
three kinds of tissues arranged in three coats (Fig. 56) : a
tissue resembling epithelial tissue (Chap. I), as a lining
to lessen friction ; an outer connective tissue (Chap. I), to
give elasticity ; and a middle coat of muscular tissue to
enable the vessels to change in size. Let us see why blood
vessels must have these three properties?

Why the Blood Vessels must be Elastic. - -The aorta and its branches
are always full of blood. When the left ventricle with its strong, mus-
cular walls contracts, the blood in the aorta and small blood tubes can-
not move forward fast enough to make room for the new supply so
suddenly sent out of the ventricle. Where can this blood go ? If a

THE CIRCULATION'

55

cup is full, it cannot become more full; not so with an artery. The
elastic connective tissue allows it to expand as a rubber hose does
under pressure. The first part of the aorta having expanded to receive
the incoming blood, the stretched walls contract because of the elas-
ticity of the outer connective tissue coat and force blood into the por-
tion of the aorta just ahead, forcing it to expand in turn. Thus a wave
of expansion travels along the arteries. This wave is called the pulse.

The Pulse may be most easily felt in the wrists and neck. As the
artery stretches and springs back, one beat of the pulse is felt. In men
there are about seventy heart beats or
pulse beats a minute. In women the
rate is about eighty a minute. It is
slowest when one is lying down, faster
while sitting, still faster when stand-
ing, and fastest of all during running or
violent exercise. (Exp. 5.) It should
not be thought that the muscular or
middle layer of the artery actively con-
tracts and helps to send along the pulse
wave ; for this wave is simply the pas-
sive stretching and contracting of the
outer connective coat, and travels like
a wave crossing a pond when a stone
is dropped into the water. The force
of the pulse is furnished, not by the
muscle fibers in the artery, but by the
beat of the heart ; the outer, or con-
nective tissue, coat enables the pulse
to travel. Why must there be a mid-
dle, or muscular^ coat for variation in
size?

Use of the Middle Coat ; Quantity of
Blood and its Distribution.- -The body
of an adult contains about five quarts
of blood. The blood furnishes the nourishment needed for the activity
of each organ. The more vigorous the work of any organ, the greater
is the amount of blood needed. The whole amount of blood in the body
cannot be suddenly increased, but the muscular coat of the arteries going
to the working organ relaxes, and allows the arteries to become enlarged
by the pressure from the heart. Consequently, more blood goes to the
active organ, and the other organs get along with less blood for the time.
When we are studying, our brains get more blood ; when running, the

FIG. 56. SECTION OF ARTERY,

A, AND VEIN, y, showing inner
coat, e (endothelial) ; middle
coat, m (muscular) ; and third
coat, a (connective tissue).

HUMAN BIOLOGY

r

leg muscles get more ; after a hearty dinner, the stomach and intestines
get more than any other part of the body. Why is it difficult to do the

best studying and digest a meal at the
same time? We see that the muscu-
lar coat of the arteries is a very useful
coat, for // enables the supply of blood
to be increased in any organ which is
in temporary need of it.

Why the Blood Vessels must be
Smooth. - - The inner coat of the heart
and other blood vessels is made of
tissue like the epithelial tissue which
forms the epidermis and the smooth
lining of the mouth and other organs.
The purpose of this lining is to lessen
friction, and thus save the work of
the heart. The friction is greatest in

FIG. 57. CAPILLARIES MAGNI-
FIED, SHOWING CELLS forming
their walls. Notice that each cell
has a nucleus and three branches.

the capillaries because of their small
size. The inner coat of smooth cells
is the only coat that is prolonged to
form the capillaries (see Fig. 57).

The capillaries are small, thin, short, and very numerous.
They are very small so that they may go in between the
cells of the tissues. The capillaries are very tJiin so that
the nourishment from the blood may pass readily into the
tissues, and the waste material pass readily into the blood.
They are very sJwrt so that the friction may be less ; and
they are very numerous so that all parts of the tissues may
be supplied with blood, and that the blood may flow very
slowly through them. Because of the number of the cap-
illaries, their total volume is several hundred times larger
than the volume of the arteries that empty into them, or
of the veins that flow from them. Hence the blood
flows slowly through the capillaries, as water flows slowly
through a lake along the course of a river. All the
changes between the blood and the lungs, and between
the blood and the tissues, take place in the capillaries, and

THE CIRCULATION

57

the object of the other parts of the circulation is merely
to move the blood continually through the capillaries.

The effect of gravity is to retard the flow in certain parts of the
body and aid the flow in other parts, according to the position of the
body (Exp. 2).

Fainting is usually due to lack of blood in the brain, which in turn results
from a weakening of the heart beat. Since the brain cannot work with-
out fresh blood, fainting is accompanied by unconsciousness. Recov-
ery from fainting is aided by loosening the clothing at the neck and by
placing the head of the patient a little lower than the body so that the
weight of the blood may aid the flow to the brain. Dashing a little
cold water in the face shocks the nerves and arouses the heart to
stronger beats.

The veins have valves placed frequently along their
course (Fig. 58). These valves are pockets made by a
fold in the inner coat of the wall
of the vein. When a boy places
his hand in his pocket, the pocket
swells out ; but if he rubs his hand
on the outside of the pocket from
the bottom toward the top, it flat-
tens down. So with the action of
the blood upon the valves in the
veins. (Repeat Exp. 6 in class.)

How Muscular Exercise aids the Heart.

T , v , . , , , FIG. 58. VALVES IN VEINS.

II hen a muscle contracts, it hardens and

(Jegi.)

presses upon a vein which goes through

the muscle, and the blood is pressed out of the vein (see Fig. 58). The
blood cannot go toward the capillaries, for the valves fill and close when
it starts that way ; so it must all go out toward the heart. When the
muscle relaxes, the blood that has been pressed forward cannot go back
because of the valves, but the valves nearer the capillaries open, and the
veins are filled from the capillaries (Fig. 53). When the muscle con-
tracts again, the same effect on the blood movement is repeated. We see,
therefore, that every contracting muscle converts into a pump the vein
running through it, and when a person works or exercises, many little
pumps are working all over the body, aiding the heart in its function.

HUMAN BIOLOGY

This aid makes the blood flow faster and relieves the heart of part of
its work, so that it beats faster, just as a horse might trot faster if
another horse helped to draw the load (Exp. 3). The pressure of a
contracting muscle upon an artery does not aid the blood flow in the
artery because the latter is destitute of valves.

How Breathing aids the Heart. --Breathing is a blood-pumping pro-
cess as well as an air-renewing process. When the chest expands,

biood is drawn into it. When the chest con-
tracts, the flow of blood away from it is aided.
As the chest expands, the downward pressure
of a great, broad muscle, the diaphragm (Fig.
74) compresses the liver, stomach, and other ab-
dominal organs, and forces the venous biood up-
ward into the expanding chest, thus helping it
on its way to the heart. But if the abdominal
wall is weakened by tight lacing or by the pres-
sure of belts and bands which support the cloth-
ing, the weak abdominal wall yields to the
downward pressure of the diaphragm, and no
compression of the liver or aid to the circulation
will result.

How the Blood Vessels are Controlled. Evi-
dently the biood vessels are not regulated by the
will. We cannot voluntarily increase the teat-
ing of the heart, or cause it to slacken its action. Even an actor cannot
cause his face to turn pale or to blush at will. This is because the
tiny muscies in the walls of the blood vessels are involuntary muscles.
They are controlled by nerves of the sympathetic system called vaso-
motors. They are not subject to the will (see Fig. 25). The nerve cen-
ter which controls the biood vessels is located in the top of the spinal
cord at the base of the brain. When cold air strikes the skin the
nerves near the arteries are stimulated, the arteries in the skin contract,
and the skin turns white. When the heat from a hot fire strikes the
skin, the nerves are soothed, the arteries relax, and the face becomes
red. When the stomach is filled with food, the heart beats faster
and sends more biood to aid in digestion. When we run fast, the
heart beats fast to supply more blood to the muscles, but it slows down
as sleep comes on, that the body and brain may rest.

Parts of the Blood. - The blood which flows from a cut
finger seems to be a bright red throughout. When a drop
of it is looked at through a microscope, however, the

FIG. 59. --THE VEN-
TRICLES OF A
DOG'S HEART
relaxed (above),
and contracted (be-
low).

THE CIRCULATION

59

liquid itself is seen to be almost as clear as water. This
liquid is called the plasma. Floating in it are millions of
biconcave disks contain-
ing a pigment (hemo-
globin) which gives the
red color to the blood.
The disks are called red
corpuscles (Fig. 60). A
few irregularly shaped
bodies, nucleated and
almost transparent, and
called ^cvJiite corpuscles,
are also found in the
blood. The red corpus-
cles go only where the FlG - 60. -HUMAN BLOOD CELLS (magni-

plasma carries them

(Exps. 3, 4). The white

corpuscles sometimes leave the blood vessels entirely.

At times one may be seen shaped like a
dumb-bell, half of it through the wall of
the blood vessel and half still in the
blood vessel. After the corpuscle is
out, no hole can be found to account
for its mysterious passage. The ^cvJdte
corpuscles consist of protoplasm. TJie
red corpuscles contain no protoplasm.
Hence tJie latter are not really alive.

The Use of Each Part of the Blood.-
The plasma keeps the blood in a liquid
state, so that it may flow readily ; the
plasma also transports the food that has

been eaten and digested, and carries carbon dioxid to the

lungs and other waste material to the kidneys. The red

fied 40,000 areas), showing many red cells
and a single white blood cell on left, larger
than red cells. (Peabody.)

FIG. 61. SIDE AND
FRONT VIEWS OF
FROG'S AND MAN'S
RED CORPUSCLES,
drawn to same
scale. Compare
outline, concavity,
diameters.

60 HUMAN BIOLOGY

corpuscles transport the oxygen from the lungs to the tis-
sues. The ivliite corpuscles devour and destroy irritating
particles, such as drugs, poisons, and germs. They are of
great importance in purifying the blood and as a protec-
tion against disease. One is shown in Fig. 60.

The sounds of the heart beat may be heard by applying
the ear to the chest. They are two, a long, dull sound and
a sliort, clear one. The first comes from the vibration of
the bicuspid valve together with an unexplained tone aris-
ing from large contracting muscles, in this case the walls
of the ventricles. The second, or short, clear sound, is
produced by the sudden closing and vibration of the semi-
lunar valves.

Changes in the Composition of the Blood as it passes
through the Various Organs. - - When the blood is forced
out by the heart, part of it goes to the stomach and
intestines through arteries which divide into capillaries.
These capillaries absorb all kinds of food from the ali-
mentary canal except the fats (see p. 64), and unite to
form the portal vein, which takes the absorbed food to the
liver. In the liver some of the impurities of the blood are
burned up and changed into bile. The blood, purified and
laden with food, is carried from the liver to the heart, where
it reenters the general blood stream. The blood flow from
the food tube through portal vein and liver to the heart, as
just described, is called the Portal circulation.

Renal circulation. Two branches from the aorta carry
blood to the kidneys. There the urea and a large amount
of water are taken out, and the purified blood is emptied
into the large vein that leads up to the heart.

Pulmonary circulation (Fig. 67). This is the circulation
through the lungs. During this circulation carbon dioxid
gas is removed from the blood and oxygen is added to it.

THE CIRCULATION

6l

FIG. 62. BLOOD CLOT
separated from serum.

Some impurities and a large amount of water escape
from the blood as it passes through the skin.

Coagulation. - - So long as blood is in an uninjured blood
vessel it remains a liquid. In a few minutes after it flows
from a blood vessel, it forms into a
stiff, jelly like mass called a clot (Fig.
62). The process of forming the clot
is called coagulation, and it is brought
about by the albuminous substance
called fibrin, which is always in the
plasma of healthy blood. On expos-
ure to air the fibrin forms into a net-
work of fine tJireads tJirougJwnt tJie
mass (Fig. 63) and the corpuscles become entangled in the
meshes. The clot consists of the fibrin of the plasma and
corpuscles ; the watery portion of the plasma, called the
serum, separates from the clot (Fig. 62 ). The property of

coagulating is a great safe-
guard, as a clot often plugs
up a cut blood vessel. What
is the difference between se-
rum and plasma ?

Veins and Arteries com-
pared. - The veins have tJiin,
soft walls and the arteries
have tJiick, tongJi, elastic walls.
When a vein is cut, it may

FIG. 6 3 . NETWORK OF FIBRIN IN usually be closed by pinching
HUMAN BLOOD (enlarged). tne wa u s Q f the end together.

If an artery is cut, the walls will not readily stick together,
but often stand open until the end of the artery is tied.
For this reason, and because an artery is subject to the
direct pressure of the heart, a cut artery is more dangerous

62 HUMAN BIOLOGY

to life than a cut vein. Because of the toughness of the
arteries, and because they are located close to the bones,
they are less likely to be cut than the veins, which are
softer and nearer the surface. The veins begin in capil-
laries and empty into tJie auricles ; the arteries begin at tJie
ventricles and empty into capillaries ; and there is a semi-
lunar valve at the origin of each artery.

Cuts and Bruises.- - 1. Wash a cut under running water.
2. Stop the bleeding. The washing in cold water may do
this. Elevating an injured arm or leg will aid the blood
greatly in forming a clot at the opening. 3. Bandage
firmly with a strip of cloth and sew the end. Keep wet
the part of the bandage where the cut is ; this lowers the
temperature of the wound. It may be necessary to hold
a gaping wound closed with strips of surgeon's plaster
placed across the cut. A handkerchief folded first
into a triangle and then into a narrow bandage is often
useful. A cut artery may be known from a cut vein by
the brighter color of the blood, and by the flow being
stronger at eacJi heart beat, while the flow from a vein is
uniform. Pressure to stop the flow of blood from an
artery should be applied between the cut and the heart ;
but when the blood comes from a vein, the pressure should
be applied to the side of the cut farthest from the heart.

Apply hot water immediately for several minutes to a
bruise. Either a bruise or a cut may be washed with a weak
solution of some antiseptic such as carbolic acid. After
washing a bruise it may be bound with a cloth soaked in
witch hazel or arnica.

THE LYMPHATIC SYSTEM

This system contains and conveys a liquid called
the lymph. It consists of lymph spaces, lymph tubes,

THE CIRCULATION 63

(lymphatics), and lymphatic ghnds. Lymph corresponds
nearly to tJic blood without the led corpuscles. It is the
familiar liquid seen in a blister, or oozing out where the
skin has been grazed without breaking a blood vessel.

Necessity for Lymph and Lymph Spaces. - The body
cannot be nourished with the albumin, sugar, oxygen, and
other digested food in the blood, until this food passes out
of the blood vessels. The food leaves the blood through
the thi r walls of the capillaries. Many of the cells do not
tr/uch the capillaries, and the lymph penetrates tJie spaces
between ilie cells to reach them (see colored Fig. 3). If
there were no lymp^ spaces, these cells could not get any
food. The lymph bathes the cells, and the cells absorb
what they want from the nourishing fluid. The red corpus-
cles bearing the oxygen cannot pass through the capillary
walls. Oxygen, being a gas, readily passes through the
walls and reaches the cells through the lymph in the
lymph spaces. The waste materials must go back into the
blood; carbon dioxid passes back through the capillary
walls and is taken to the lungs ; how the other waste
materials formed in the cells pass back will soon be
explained.

Need of Lymphatics. The plasma continually passes
into the tissues, but it cannot return directly into the blood.
The lymph contains waste material which must be
removed, and also much unused food which nature, like an
economical housekeeper, will offer to the tissues again.
TJiere are vessels called lymphatics that take the lymph back
into the blood (see Fig. 64).

The Lymphatic Circulation (Fig. 64). The blood flow does not
begin nor end, but makes a never ending circle. The countless
lymphatics begin, ivith open ends, in the lymph spaces between the cells
(colored Fig. 3). The smaller lymphatics unite into larger ones until
finally they all unite into two large ones that empty into the large veins

6 4

HUMAN BIOLOGY

under the collar bones, near the neck. The one that empties under the
left collar bone (3, Fig. 66) is called the thoracic duct because it goes

FIG. 64. SURFACE LYMPHATICS OF HAND.

up through the thorax just in front of the spinal column (i. Fig. 66).
The other at the right side of the neck is called the right lymphatic
duct (see Figs. 64, 65).

In persons with the dropsy, the lymph accumulates in the lymph
spaces and is not drained away by the lymph flow. Dropsy usually

shows itself first by swelling of the feet and
the leg below the knee. (Why ? See Exp. 2.)
There is a set of lymphatics called lacteals,
situated in the abdomen, which have the func-
tion of absorbing digested fats from the intes-
tine (Figs. 66, 100, and colored figure 2).

What makes the Lymph Flow ? - - The heart
does not, for its pressure is not transmitted be-
yond the blood tubes. The successive pressures
of a working muscle move the lymph forward
in the lymphatics in the same way that the blood
is moved forward in the veins, and the valves
keep it from moving back. When riding a trot-
ting horse, or in a jolting vehicle, the lymph is
moved beyond the valves at every jolt (Fig.
64). Without exercise the lymph stagnates,
and the body becomes poisoned by its own
wastes. At every expansion of the lungs lymph
is drawn into the chest ; and it is forced out of the chest at every con-
traction. Deep breathing is as great a benefit to the body in moving
stagnant lymph as it is in purifying the blood.

B'IG. 65. DIAGRAM TO
SHOW THE Two
PARTS OF THE BODY
DRAINED BY THE
Two LYMPH DUCTS.

THE CIRCULATION

The lymphatic glands are kernel-like enlargements
along the lymphatics, and they contain a great many
lymph cells which purify the lymph as it passes through

FIG. 66. CHIEF LYMPHATIC VESSELS AND GLANDS of trunk,

i, 3, Thoracic duct (emptying at 3) ; 2, receptacle for chyle (lacteals below it).

them. The lymphatic glands are numerous in the armpits
and the groins. The cells in the lymph glands multi-
ply, and some of them are carried by the lymph into
the blood to become those remarkable little bodies, the
white corpuscles.

66 HUMAN BIOLOGY

HYGIENE OF THE CIRCULATION

Effects of Work, Fresh Air, and Rest on Corpuscles and
Plasma. Work uses up the nutritious elements in the
blood. A few hours after food is eaten the nutritious ma-
terials in the blood are found to be increased. By the
breathing of fresh air the carbon dioxid in the ,plasma is
diminished and the oxygen in the colored corpuscles is in-
creased, changing the blood to a brighter red. Sleep gives
time for the exhausted cells and depleted blood to be re-
plenished. Loss of sleep means longer hours of activity
and greater consumption of nutriment with shorter hours
for replacing the nutriment. The pale skin of one who has
lost sleep tells of the exhausted condition of the blood.

How the Muscles help the Circulation. The imperative
need of muscular exercise to keep the body sound exists
because of the lack of other means to cause movement in
the veins and lymphatics. Good food, pure air, and plenty
of exercise are necessary for healthy blood. Many so-
called " blood purifiers ' are advertised to entrap the
ignorant. It is impossible to imagine how "blood puri-
fiers ' can aid the blood. The blood is purified, not by
putting anything into the blood, but by something going out
of it as it passes through the skin, kidneys, liver, and lungs.
These organs all send out impurities brought to them by
the blood.

The one great hygienic effect of muscular exercise is an
active circulation, and from an active circulation nine chief
effects may be traced. The effects upon the body will be
given in order, beginning with the surface- -skin, fat,
muscles, bones ; and the effects upon the internal organs
are given in order of position, beginning with the highest
brain, lungs, heart, digestive organs.

THE CIRCULATION 6/

Effects of Exercise and Improved Circulation. - i . The

skin is made fresh, pink, and smooth from the flushing of
the capillaries ; it is purified by the perspiration and the
renewal of cells. 2. If the fat is too great in amount, it is
burned up ; if it is too small in amount, the better nourish-
ment brought by the blood increases it. 3. The muscles
are better fed (see Fig. 48) and grow firm, strong, and
large. 4. The skeleton is held in proper position by the
stronger muscles, and deformity is prevented. 5. The
brain. The pure, fresh blood, loaded with oxygen from
expanded lungs, flushes every capillary of the brain, clears
the mind, and doubles or trebles its power to work.
6. The lungs are expanded by deep breathing if the exer-
cise be rapid and vigorous. A slow stroll or saunter is not
of value. 7. The circulation. Every contracting muscle
aids the heart in its work. The deep breathing moves
stagnant lymph. 8. The stomach. Exercise burns up the
food and increases the appetite. 9. General effects. Ex-
ercise promotes good humor, decreases loafing, cigarette
smoking, gossiping, and other vices.

The effect of tobacco on the heart, if cigarettes or
cigars are used, is sometimes to cause attacks of irregular
beating ; the heart flutters faintly for a while, then palpi-
tates strongly, then flutters again. This condition is called
tobacco heart, or trotting- heart.

Effect of Alcohol upon the Circulation.- -After a person
has taken an alcoholic drink his face and skin are likely to
become flushed, and perhaps his heart beats faster. Most
investigators have found that the alcohol itself does not
directly increase or strengthen the action of the heart.
Hence it is probably wrong to call alcohol a heart stimu-
lant. The flushing of the skin is believed to be due to the
relaxing effect of alcohol. It relaxes, it paralyzes, the

68 HUMAN BIOLOGY

vasomotor nerves which control the little muscle fibers
in the walls of the blood vessels. The relaxing and
enlarging of the blood vessels decreases the resistance to
the blood flow, and the heart beats faster under its lighter
load. The narcotic effect of alcohol is much more power-
ful than its irritating or stimulating effect. The effect
of alcohol in causing fatty degeneration of the muscles
often weakens the heart and other blood vessels.

Climate and Brain Work. --In going to sleep the vessels in the skin
dilate and blood is drawn from the brain to tJie skin. It is difficult to
go to sleep when cold, for cold sends the blood to the brain and keeps
the mind active. On the same principle, mental work is difficult in very
warm weather because of the enlarged capillaries in the skin and the
withdrawal of blood from the brain to the skin. This increases the
perspiration and keeps the temperature of the body down to normal, but
it deprives the brain of blood needed for good mental work. Mental
workers in warm weather and in warm climates should seek every con-
dition favoring coolness. Benjamin Franklin was accustomed to strip
himself almost entirely of clothing when he was writing and wanted his
brain to work at its best. The wearing of barefoot sandals and the thin-
nest cotton clothing^ light in color, helps to prevent mental inertia in hot
weather. In the Gulf states in summer and in our tropical islands the
best mental work can be done by rising at dawn and working before
the hot part of the day begins. Some of the greatest thinkers in the
world have lived in warm climates (Greece and India), but they wore
very few clothes and ate moderately of the simplest food (see p. 44).

Congestion is a swelling of the blood vessels of some part, with the
accumulation of blood therein. Congestion is active when a rapid flow
of blood distends the capillaries. Example, flushing of face when
running. Congestion is passive when there is a narrowing of the out-
let of the capillaries, the blood moves slowly and partly stagnates in the
swollen vessels. Example, when the nose feels stopped up during a
cold. If a syringe is worked so fast that the rubber tube swells, this is
like active congestion ; if the end of the tube is pinched together so
that moderate pumping causes it to swell, this is like passive con-
gestion.

Inflammation is congestion where the vessels of any part are strained
and injured. White corpuscles collect there to repair the vessels and
devour the blood that escapes and stagnates there. They also destroy
germs that have usually found lodgment and begun to multiply. The

THE CIRCULATION 69

serum of the blood also destroys the germs by the antitoxins in it.
Inflammatory troubles are : colds, rheumatism, diarrhoea, and all dis-
eases with name ending "itis" An inflamed part is red, swollen, hot,
and painful.

Prevention and Care of Colds. --A cold is an inflammation of a
mucous membrane. Colds are prevented by so living as to encourage
nfree, vigorous circulation, and especially by not coddling the body so
tenderly that the circulation becomes deranged by the least exposure.
The circulation may be deranged by overheating as well as by chilling
the body ; usually it would be more appropriate to say that the person
caught '-a hot" than u a cold." 1 At the first sign of a cold vigorous
exercise, a cold bath, or going outdoors into cold air may aid in sending
fresh blood to remove the stagnation and stop the inflammation. A
warm foot bath and hot drinks may relieve by drawing blood from the
congested mucous membrane. After the cold has become fixed such
measures will not help, but the cure is aided by helping the skin to
keep its full share of blood. The cold must run its course. The cells
will be given every chance to repair the injury and destroy the germs
(if any) by avoiding hard work, eating moderately of digestible food,
avoiding drugs, especially infallible drugs advertised in newspapers,
even if recommended by otherwise intelligent people. Repeated colds
tend to become a disgusting disease called chronic catarrh. Con-
stricting the blood vessels of the skin causes congestion of the (internal)
mucous membranes. A skin tenderly protected constricts more readily
than one accustomed to cold. Cold is the best preventive of cold. Cold
baths, pure air, light clothing, free breathing, moderate eating, ward off
colds. Fussing with sprays, gargles, and drugs will not; for the
main factor in bringing on a cold is not germs, nor temperature, but the
state of the system itself. Persons who have suffered much with colds
have found that after substituting cotton underwear for woolen, colds
became very rare. Linen will have a similar effect, but it is not as dur-
able, soft, or heat-retaining as cotton (see p. 16).

PRACTICAL QUESTIONS. 1. Through what kind of skin do the
blue veins in the wrist show most plainly? 2. Which is more com-
pressible, a vein or an artery? 3. Why are those who take little exer-
cise likely to have cold feet? (p. 57.) 4. Where does the so-called
venous blood flow through an artery? 5. What vein begins and
ends in capillaries? (The portal vein, colored Fig. 5.) 6. To what
purifying organ, after leaving the lungs, does the heart send part of
the blood for further purification. (Colored Fig. 5.) 7. What keeps
the blood moving between the beats of the heart ?

CHAPTER VI

THE RESPIRATION

Experiment i. (Home.) Study of the Throat. Sit with the back
to the light. Study the open mouth and throat with a mirror and make
out the uvula, tonsils, and other parts shown in Fig. 68.

Experiment 2. Anatomy of Lungs. -- Study fresh lungs of sheep,
hog, fowl, or frog. Will they float ? Will they contract when expanded
by air blown in through a quill or other tube? What is the structure
of the windpipe? Can you distinguish the arteries from the veins by
the stiffness of their walls? Which contain pure b'ood? Study
branching of air tubes. Make a sketch.

Experiment 3. Tests of Expired Air. Breathe upon a mirror, bright
knife blade, or cold window pane. Result? State your conclusion?

Experiment 4 Carbon dioxid added to limewater will cause a white

cloud consisting of particles of limestone. Breathe through a tube or
straw or the hollow stem of a reed into clear limewater. Result ? Con-
clusion? (Limewater may be had at druggists or made by pouring
water upon a lump of unslackened lime and draining it off when lime
has settled.) Experiment 5. Breathe for several minutes upon the
bulb of a thermometer. Result? Conclusion? Experiment 6. Breathe
a few times into a large, carefully cleaned pickle jar, or a bottle. Cork
it tightly, and set it in a warm place for several days. Then uncork
and smell the air in it. Result? Conclusion? Experiment 7. Pierce
a small hole in a card, place card over a wide-mouthed bottle, and
breathe into bottle through a tube, lemonade straw, or hollow reed.
Pull out straw. Place bottle, mouth downward, on table, and slip out
card. Slide bottle to edge of table and lift lighted candle into bottle.
Result? Experiment 8. Place bottle of fresh air over lighted candle.
Result? Conclusion? (See Animal Biology, p. 14.)

Experiment 9. (School.) Testing the Air of a Room. Fill a fruit
jar or large bottle with water, and take it into a room containing many
people. Pour out the water. (This insures that all the air now in the
jar is air obtained in the room to be tested.) Seal the jar if test is not to
be made at once. Test by pouring in two tablespoonfuls of clear lime-
water and shake. If the limewater turns milky, the ventilation is bad.

Experimejit 10. (Home and school.) Homemade Current Detector.
Dangle a bit of paper by means of a spider web or thread from the

70

THE RESPIRATION 1 71

end of a walking stick or ruler. (Or test with the flame of a candle.)
Hold it near cracks of window, above and below doors, and especially
before openings intended for entry and exit of air, and test if air moves
as desired.

Experiment 11. Ventilation of the Schoolroom. -- Let the whole
class rise, and with the fingers test cracks around doors and windows.
Wherever the air feels cold to the hand the air is entering.

Experiment 12. Dust. --With a mirror cause a sunbeam to play like
a search light into a closed room several, hours after it has been swept.
Result? Do the same in a room where every window and door were
open during sweeping and left open afterwards. Result? Conclusion?
Note also the amount of dust on the furniture of each room.

Experiment 13. Study of Habitual Quiet Breathing. - -Without any
more disturbance of the breathing than can be helped, direct your atten-
tion to your breathing while sitting quietly. Record motions of any
parts of chest and abdominal walls that may be noticeable. If neces-
sary, lay the hands successively against different parts of the wall to
test for motion. Think of another subject, and later repeat observations.

Experiment 14. Study of Deep Breathing. -- Place your hands suc-
cessively upon the front and sides of your chest, waist, and abdomen,
while drawing in and sending out deep breaths. What motions of the
several parts are observed at each stage ?

Experiment 15. Study of Elasticity as a Factor in Breathing. -
(i) Notice whether in quiet breathing there is an elastic rebound as
the breath goes either in or out. If so, it is due to the elasticity of the
cartilages or air cells of lungs, or both. (2) Breathe by inflating the
lungs strongly at each breath. Is the air then forced out without
effort? (3) Breathe by flattening the chest and abdomen as much as
possible at each breath. Does the air then rush in without effort?

Experiment 16. Chest Breathing. - -Try to breathe wholly by deep
expansions and contractions of chest wall. What motions, if any, are
noticed in abdominal wall as breath goes in ? As it goes out ? (Test
motions with hand.)

Experiment 17. Abdominal Breathing. - -Try to hold the chest walls
still and breathe by strong contraction and expansion of abdomen.
Do the chest walls move at all? Neither ''chest breathing 1 ' nor
< 4 abdominal breathing " is the normal way. See text.

Experiment 18. Full Breathing.- -Try breathing by outward and
inward movement of walls of chest, waist, and abdomen. Do you suc-
ceed? This is normal breathing. Is the motion greater at the front
or the sides of the waist? Put a belt around the waist tight enough to
stay in place and repeat. Is the wais* motion interfered with?

HUMAN BIOLOGY

Experiment 19. How the Ribs are Lifted. Make a model like
sketch to represent backbone, breastbone, and two ribs, using pins to

make joints loose at corners. Use cords for diagonals.
What happens when cord ac is pulled? When cord
bd is pulled? The cords correspond to the two sets
of muscles between the ribs.

Experiment 20. Study of Laughing. Place the
hands upon the waist and abdomen when laughing.
What motion occurs at each sound of laugh ? Draw
in the abdominal wall with a jerk. What is the effect
upon the breath ?

Experiment 21. Modifications of the Breath. -
Write I, E, or IE after each word in this list, accord-
ing as inspiration, expiration, or both, are involved in the action. (Test
with sham acts if possible.) Sighing, sobbing, crying (of a child),
coughing, laughing, yawning, sneezing, hiccoughing, snoring.

Experiment 22. Effects of Exercise. --Count and record the rates of
breathing before and after vigorous exercise.

Experiment 23. Comparative Study. -- Observe and record the rate
and manner of breathing of cow, horse, dog, cat, etc. Is the air drawn
in or sent out more quickly? Is there a pause? If so, after which stage
of breathing?

Experiment 24. Emergency Drill. Resuscitation from drowning,
etc. See Coleman''s " Elements -of Physiology," page 356.

Necessity for Breathing and for Specialized Organs of
Breathing.- The body is a self-regulating machine which
possesses energy. This energy, like that of steam engines,
arises from oxidation which takes place continually, but at
a varying rate. Food for fuel is taken at intervals, but
oxygen must be taken in continually. Man breathes about
eighteen times per minute. The blood in the tissues soon
becomes dark because of loss of oxygen and absorption of
carbon dioxid. It is then pumped through the heart to
the organ which has the function of absorbing oxygen
and giving off carbon dioxid (Fig. 67). In some animals,
as the ameba and the earthworm, the surface of the body
suffices for breathing. This cell breathing is the true
essential respiration ; it is universal among living things,

THE RESPIRATION

73

both plants and animals. To siipply the deeper cells large
animals require a breathing surface greater than the area
of the skin. TJiis is supplied by having the oxygen-absorb-
ing surface folded inward to form folds, tubes, and cavities
of great complexity. If the lungs of a man were unfolded
and all their tubes and cavities spread upon one surface,
an area of more than one hundred square feet (or ten feet
square) would be covered.

Each respiration, or breath, consists of the passing in
of the air, or inspiration, sending it out, or expiration^
and a pause after
one but not after
both of the other
stages.

The Air Passages.
The air usually
passes in at the
nose and returns
by the same way,
except during talk-
ing or singing. Ob-
serve your mouth
with a mirror (Fig.
68); at the back
part, an arch is
seen which is the
rear boundary line
of the mouth (Exp.
i). Just above the
arch is likewise the rear boundary line of the nasal pas-
sages. The funnel-shaped cavity beyond, into which both
the mouth and nasal passages open, is called the pJiarynx
(far'inks), or throat (see Fig. 68, also Fig. 83). Below,

FIG. 67. CIRCULATION THROUGH LUNGS (sche-
matic) : " venous " blood (in pulmonary artery)
black; "arterial" blood (in pulmonary veins)
white.

74

HUMAN BIOLOGY

Palate

Uvula

Posterior
arch

Pharynx

Tonsil

Anterior
arch

Tongue

FIG. 68. OPEN MOUTH, showing palate and tonsils.

two tubes open
from the phar-
ynx. One is the
tracJiea (tra'kea)
or windpipe, the
other is the esoph-
agus or gullet.
At the top of the
trachea is the
cartilaginous lar-
ynx, or voice box.
If the finger is
placed upon the
larynx or Adam's
apple, it is plainly
felt to move up
and down when

swallowing. The opening into the larynx is provided with
a lid of cartilage, the epiglottis. Inside the larynx, the

vocal cords are stretched
from front to back. Just
below the larynx comes the
trachea proper, which is a
tube about three fourths of
an inch in diameter and
about four inches long (Fig.
69). It consists of hoops of
cartilage (Fig. 69) which are
not complete circles, but are
shaped somewhat like the
letter C, being completed at

FiG.69. - - LUNGS P- with trachea, ^ ^ b invohmtary mus .
TA\ thyroid gland, th ; larynx, L\ J J

and hyoid bone, H. cular tissue, whose function

THE RESPIRATION

75

FIG. 70. LOBULE
OF LUNG.

is to draw the ends together at times (for instance, during
coughing) and reduce the size of the tube. The function
of the hoops of cartilage is to keep the windpipe open at
all times. If it should be closed by pressure, life might
be lost. These rings of cartilage may be felt in the neck.
The lower end of the trachea is just behind the upper
end of the breastbone; there it divides into two large
tubes. These subdivide into a great
number of smaller branches called bron-
chial tubes. Cartilage is found in the
walls of all but the smallest of the tubes.
The subdivision continues, somewhat like
the branching of a tree, until the whole
lung is,, penetrated by bronchial tubes.
Each tiny tube finally ends in a wider
funnel-shaped chamber called a lobule
(Fig. 70), into which so many dilated
sacs, called air cells, open, that the walls of the terminal
chamber or lobule may be said to consist of tiny cups, or

air cells, placed side by
side. The lobules, or
clusters of air cells, are
chiefly near the surface
of the lung. (The word
" cell ' is here used in
its original sense to de-
note a cavity or cham-
ber, and not in the sense
of a protoplasmic cell.)
The air cells are elastic
FIG. 71. CAPILLARIES AROUND AIR SACS and enlarge by stretch-

OF LUNGS (enlarged 30 diameters). Air ^ the chegt x _

sacs in white spaces. Dark lines are capil-
laries. (Peabody.) pands ; hence, the cells

7 6

HUMAN BIOLOGY

must have many of i\\Q yellow elastic fibers of connective
tissue in their walls. They are lined with an exceedingly
thin membrane of- epithelial cells through which oxygen
and carbon dioxid are exchanged. In the walls of the air
cells there is a network of capillaries (Fig. 71). The dark
red blood comes into these capillaries from the pulmonary
arteries, and is changed to a bright red by the time it
leaves them to enter the pulmonary veins. The air leaves
the lungs warmer, moister, and containing more carbon
dioxid than when it entered.

Most of the mucous membrane lining the air passages
has a surface layer of ciliated cells. Cilia are tiny thread-
like projections (Fig. 72) which con-
tinually wave to and fro, the quicker
stroke always being outward ; for their
function is to remove particles of dust
and germs that may find entrance to
the air passages. When the mucus
containing the dust is raised nearly to
the larynx, it may be thrown out by
coughing. Near the opening of the nos-
trils are placed many hairs, hundreds
of times larger than cilia, through which the air is strained
as it enters the nose. Hairs are multicellular ; cilia are
parts of cells. See Animal Biology, Fig. 14.

The Lungs.- -The entire chest cavity is occupied by the
lungs except the space occupied by the heart, the larger
blood vessels, and the gullet. The right lung has three
lobes, or divisions, and the left lung has two lobes. The
lungs are light pink in early life, but become grayish and
darker as age advances. This change is more marked in
those who dwell in cities, or wherever the atmosphere is
smoky and dusty. The lungs are covered and inclosed by

FIG. 72. CILIATED

CELLS, lining the air

passages.

THE RESPIRATION

77

a smooth membrane called the pleura. This membrane
turns back and lines the chest wall, so that when the chest
expands, the two sleek membranes glide over each other
with far less friction than would be the case if the lungs
and chest wall were touching (Exp. 2).

The Respiratory Muscles. - -(Repeat Exps. 13, 14, 15.)
The chief breathing muscles are the diaphragm (see Figs.
73 and 74), the muscles forming
tJic abdominal walls (see Fig.
44), and tivo sets of si tort mus-
cles (an internal and an external
set), between the ribs. They
are called intercostals. (They
are the flesh eaten when eating
pork ribs.) The diaphragm,
which is shaped like a bowl
turned upside down, rounds up
under the base of the lungs
somewhat like a dome and sepa-
rates the chest from the ab-
domen. Its hollow side is
toward the abdomen and its
edges are attached to the lowest
ribs and the vertebra of the
loins. Inspiration is brought
about by the rising of the ribs
and the descent of the dia-
phragm. Expiration takes
place when the ribs descend,
the abdominal walls draw in,
and the transmitted pressure lifts the relaxed diaphragm.

Inspiration.- -To cause inspiration the diaphragm con-
tracts, it flattens and descends, since its edges are attached

FIG. 73. VERTICAL SECTION
OF TRUNK, showing dia-
phragm, cavities of thorax and
abdomen.

HUMAN BIOLOGY

lower than its middle (Fig. 73); the lungs descend with it,
thus lengthening the chest from top to bottom ; at the

Inferior
vena
cava

(Esophagus

Aorta

Internal

ligament
External
ligament

FIG. 74. DIAPHRAGM (or midriff), seen from below. (Cunningham.)

The central portion (light) is tendinous. As the diaphragm descends, it acts like the piston
of a great pump and the blood is forced up through the vena cava, and the lymph through
the thoracic duct (Fig. 66).

\

same time the ribs are raised upward and outward (Fig.
76) by the contraction of the outer set of muscles between
the ribs. Thus the cJicst is made longer, broader, and
deeper from front to back. The lungs expand when the
chest expands, and the air rushes in. Why is this? The
lungs contain no muscles and cannot expand themselves ;
the air cannot be pulled in, for its parts do not stick to-
gether. The true reason is that the air has weight. The

THE RESPIRATION

atmosphere has a
height of many miles,
and the air above is
pressing on that be-
low. When the chest
walls are raised there
would be an empty
space or vacuum be-
tween these walls and
the lungs, did not the
pressure of the outside
air pusJi air through
tJie windpipe into tfie
lu tigs a n d exp and
tli cm (Ex p. 19).

FIG. 75. FRAMEWORK OF CHEST.

Expiration. - - In very active breathing the abdominal

walls actively contract so
that they press strongly
upon the digestive organs,
which in turn press the
diaphragm ?//. The ribs
are also drawn down and
in. Thus the chest be-
comes smaller and forces
the air to flow out through
the windpipe (Exps. 20
and 21).

THOUGHT QUESTIONS. Why
breathing with the waist is easier
than breathing with the itpper
chest. Effects of confining the
waist.

i . There are two pairs of -

FIG. 76. BLACKBOARD SKETCH, to
show how the chest is expanded when
the ribs move upward and outward.

ribs below, while there are none

8o

HUMAN BIOLOGY

above. 2. There are three pairs of -

none above, but all ribs of the upper chest are

ribs below, while there are
ribs. 3. The

lower of the joints between the seven pairs of true ribs and the sternum

are more flexible than the upper joints because . (Observe the

joints in Fig. 75.) 4. The walls of the waist swing - -and ,

while the walls of the upper chest must move - - and - . 5. The
bones of the - - rest upon the upper chest. In upper chest breathing

their weight, and the weight of both of the
lifted. (Fig. 28.) Test by trying it.

must, therefore, be

Hygienic Habits of Breathing. - - Chest breathing uses
chest chiefly, abdominal breathing uses abdomen chiefly,

FIG. 77. FIG. 78. FIG. 79.

FIG. 77. FEMALE FIGURE ENCASED IN CORSET. Expansion at the waist is here impossi-
ble and the breathing is called " collar-bone breathing."

FIG. 78. MALE FIGURE. Here, owing to pressure of clothing and faulty position, expan-
sion of chest is hindered and breath is taken by the " abdominal method."

FIG. 79. FIGURE PROPERLY POISED AND FREE. Here the entire thorax can move freely,
and natural breathing is the result. (For blackboard.) From Latson.

full breathing uses both. These three forms depend
upon whether the breathing is carried on by using
the muscles of (i) the chest, (2) the abdomen, or (3) both
(see Figs. 77, 78, 79). There has been much debate
among physicians, surgeons, and singers as to which of
these methods is best. Probably this question would not
have been raised but for the confining and deforming
effect of clothing upon the waist. Full breathing is used

THE RESPIRATION 8 I

by children of all races, by both men and women of wild
tribes, and by men of civilized countries. It is undoubtedly
the natural way, as well as the easiest and most effective
way (Exps. 16, 17, 18).

Breathing with the upper chest is exhausting because of the stiffness
of the upper part of the bony cage (see Fig. 75) ; for it is inclosed by
true ribs fixed to the breastbone bv short cartilages. The ribs in the

<j

waist (Fig. 75) are either floating in front or fixed by long cartilages to
the ribs above. In pure abdominal breathing the diaphragm must con-
tract more than in full breathing in order to descend, because its edges
have been drawn together and fixed by binding the ribs at the waist.
In full breathing the floating and false ribs at the waist (five pairs in
all) float in and out as nature provided. As they move out, this
broadens and deepens the chest, and aids the flattening of the dia-
phragm by moving its edges farther apart. Those persons, perhaps
one in a thousand, who voluntarily deform the body with tight clothing
are beneath contempt. But so uniform is the pressure of tight clothes
and shoes that the wearer soon becomes unconscious of them, and so
powerful are the effects that not one person in a thousand escapes
deformity and injury. Children's clothing should be supported by the
shoulders, and adults 1 clothing 'by both shoulders and hips, but by
the waist, never.

Cellular Respiration.- -The chemical activities within the cells and
their need of oxygen, not the amount of oxygen in the lungs or blood,
determine how much oxygen the cells absorb from the blood. Oxygen
cannot be forced even into the blood beyond the required amount.
Deep breathing movements, however, help the flow of the blood and
lymph. Carried to excess, they tire the will and exhaust the nerves.

Changes in Blood while in the Lungs. - The coloring
matter (or hemoglobin) of the corpuscles absorbs oxygen
(and becomes oxy-hemoglobin). Carbon dioxid is given off
from the plasma. The blood becomes a brighter red.

Changes in Air in the Lungs. - The air entering the
lungs consists of about one fifth oxygen and four fifths
nitrogen. This nitrogen is of no use to the body, and is
exhaled unchanged. A part of tJie oxygen inspired is taken
up by the blood, and carbon dioxid is sent out in its place.

82

HUMAN BIOLOGY

About half a pint of water is given off through the lungs
in a day. Minute quantities of injurious animal matter
are also given off in the breath from even the soundest
person. The air leaves the lungs warmer, damper, and with
more carbon dioxid than when it entered (Exps. 3 to 9).

Persons with decayed teeth, catarrh, indigestion, diseased lungs, or
other unsoundness give off still more of this material. When many
people are assembled in a badly ventilated room, the amount of injurious
animal matter in the air is much increased, and is called " crowd poison"
Its odor is strong and repulsive to one who just enters the room, but
the sense of smell becomes dull to it in a few minutes. It would seem
that nature gives a fair warning against harm ; but if we disregard the
warning.it soon ceases.

People who are really Unclean. Nature's plan seems to be for us to
live out of doors. Air once breathed is impure. It is just as unfit to
enter our bodies as muddy water or decayed food. Yet many who call

themselves cleanly
and refined, and
will not allow a
speck of dirt to
remain on their
clothes, nor use a
spoon just used by
another, do not
object to breathing
into their lungs,
over and over
again, the cast-off
air from the lungs of others. If a window is opened for ventilation,
they are horror-stricken for fear of drafts. Drafts are injurious only to
persons perspiring, or to those who have coddled the skin by continu-
ally overheating it. There are thousands of schools, churches, and
theaters all over the land which reek daily with the malodorous particles
from the lungs of their occupants. Although the air in them is odorless
to those who occupy them, it is disgusting to any one who enters from
the fresh air. Figure 80 shows the correct ventilation of a stove-heated
schoolroom.

Dust causes catarrh of the bronchial tubes and chronic

1 From Coleman's Elements of Physiology (400 pp.). The Macmillan Co., N.Y.

\

fffffffftf

JL

JL

FIG. 80. VENTILATION OF STOVE-HEATED RooM. 1

How are the inlet and outlet situated with reference to the stove ?

THE RESPIRATION 83

inflammation of the lungs ; it prepares for consumption,
by gradually weakening the lungs of those who breathe
it. Intelligence and common sense are necessary to pre-
vent it from accumulating in the house. The chief pur-
pose of the house cleaning should be not only to remove
bits of paper from the floor, which do no harm even to the
shoes, but to remove impurities from tJic air. It does no
good to stir up the dust and allow it to settle down again
(Exp. 12). In many houses dust is thus allowed to
accumulate for months. Experiments show that dust and
germs floating in the air are not diminished to a great extent
by a gentle draft through the room. The windows must
be open and sweeping done in the direction of the air
currents ; the windows should be left open for a long while
after tJie sweeping. A windy day is best for sweeping.

The habit some housekeepers have of buying furnishings and bric-
a-brac for the home until it looks like a retail store or junk shop, makes
it almost impossible to clean their houses. A few articles, carefully
selected, adorn a home more than many bought at random, and they do
not litter the house and serve as traps for dust. With all precautions
some dust may settle down. This should not simply be stirred up again
with a feather duster, but the dusting should be done 'with a damp cloth.
Ashes should be sprinkled before they are moved. Carpet sweepers,
but never brooms, should be used upon carpets. Carpets and lace cur-
tains are truly dust traps, in which dust will accumulate without limit.
Those who value the health will not use such uncleanly abominations,
at least in bedrooms. Though linoleum, bare floors with movable nigs,
oiled and painted floors, may not look so comfortable as a fixed carpet,
they bring far more comfort in the end. The weakening effect of ordi-
nary dust is one of the chief causes of lung diseases, and prepares a fertile
soil for the consumptive germ. The sputum coughed up by consump-
tives falls upon the floor or street, soon dries, and the germs are driven
about by the wind. In many cities there is a law against spitting in
public places, and the streets are flushed with water before they are
swept.

Ventilation presents no difficulties in the summer time
or in warm climates. The reason that it is a difficult

8 4

HUMAN BIOLOGY

question in cold weather is because the air furnished must

be not only pure, but warm. To keep cold air out often

means to keep foul air in. Heating with hot air, by which

system pure air is passed over
a furnace, and fresh air con-
stantly admitted, may be a good
method (Figs. 80, 81), but is
often a dismal failure because
it dries out the air, which in
turn dries out the skin. To
prevent this, wide vessels of
water should be set at the in-
lets. Dry air is cooling. Why ?
Dr. Barnes proved that moist
air at 65 is as comfortable as
dry air at 71. Air saturated
with vapor at 60 will only be
50 per cent saturated at 80.
Such air dries out the mucous
membrane of eyes, nose, and

throat. Heating by hot water circulating in pipes, or by

steam, gives no means of

introducing fresh air, and

is likely to cause worse

ventilation than any other

method. The radiators

should stand close to win-
dows or other fresh-air inlet,

that the air may be heated

as it enters, and the outlet

for air should be farthest

from the radiators. The same rules apply to heating by

stoves. An oil stove for heating is an inconceivable

FIG. 8 1. --The air enters through
a special inlet and is warmed
as it passes through hood sur-
rounding the stove.

\

/

FlG. 82. Chimney with a passage be-
hind fireplace, or grate, in which the
air is warmed as it enters.

THE RESPIRATION

iniquity to any but a person densely ignorant of hygiene.
Heating by fireplaces (Fig. 82) is the most healthful of
all methods, for there is a constant removal of air through
the chimney, and this air will be replaced; even if all
doors and windows are closed, it will come in through tiny
cracks. Radiant heat travels in straight lines from a
fireplace and warms solid objects, but not the air passed
through. Hence an open fire will keep the body warm
with the room at a low temperature. Fireplaces, however,
do not afford sufficient heat in severe climates.

Stoves are not as healthful as fireplaces, for there is not
so much air removed through
the pipe as through the
chimney. Carbon monoxid,
unlike carbon dioxid, is an ac-
tive poison causing the blood
corpuscles to shrivel. It
passes through red-hot iron
or a cracked stove or furnace.

FIG. 83. BLACKBOARD SKETCH.

Reasons for Breathing through the
Nose (Fig. 83). --(i) The many
blood vessels in the mucuous mem-
brane lining the nasal passages so
heat the air^ttidk it does not irritate the bronchial tubes. (2) The hairs

in the nostrils strain the air and catch
dust ; the cilia of the nasal passages
also do this. (3) A mouth-breather
often swallows food before chewing it
sufficiently, because he cannot hold his
breath longer. (4) The nasal mucous
membrane of an habitual mouth-
breather dries and shrinks and ob-
structs the circulation, bringing on
catarrh of the nose. (5) Mouth breath-
ing causes an unpleasant expression of
countenance (see Fig. 84). (6) The

FIG. 84. Facial expression in
mouth breathing, and breath-
ing through the nose.

86 HUMAN BIOLOGY

breath does not come through the nose as quickly as through the
mouth ; the lungs are kept more expanded, and one does not get
" out of breath " so quickly. (7) The voice of the mouth breather has
a hard twang, not a full, resonant tone as when the nostrils are open.
(8) Flavors and odors are better appreciated. Sometimes the sense
of smell is almost lost by mouth breathers. If one cannot breathe
through the nose, even for a short time, there is probably an adenoid,
or tonsil-like, growth in nose or pharynx, and a physician should be
consulted. " Adenoids " are glandular or grapelike in form.

Diseases of the Respiratory Organs. A cold or catarrh is an inflam-
mation of a mucous membrane. If the inflammation is in the nasal pas-
sages, it is called a cold in the head ; if it is in the pharynx, it is called
a sore throat ; if it is in the larynx or voice box, there is hoarseness ;
if it is in the bronchial tubes, it is bronchitis ; finally, if it is in the air
cells, it is pneumonia. If the air is cut off from access to the air cells,
there is an attack of the painful disease called asthma, which is accom-
panied by a feeling of suffocation. Some believe that asthma is caused
by the mucous membrane lining the finest bronchial tubes becoming
inflamed and swollen, and closing the tubes ; others think that the
muscles in the large bronchial tubes contract and close the tubes.
Pleurisy is inflammation of the pleura and makes breathing painful.
If much fluid forms between the pleuras, the inner pleura may press
upon the lungs and interfere with breathing.

Alcohol not only weakens the blood vessels near the sur-
face, but the blood vessels in general. Weakened and
congested blood vessels in the lungs make them more
liable to pneumonia and other congestive diseases. Con-
tinual congestion causes an abnormal growth of connec-
tive tissue fiber in the walls of the cells. This diminishes
the capacity of the lungs and interferes with the exchange
of carbon dioxid and oxygen.

Tobacco. It is often asked why cigarettes are so much
more injurious to the health than pipes and cigars. The
nature of the paper of cigarettes and various other absurd
reasons have been assigned. The true reason is that the
cigarette smoker usually inhales the tobacco smoke. Cigar
smoke, if drawn into the lungs, would usually be coughed
up at once. Cigarette smoke is weaker it is so weak

THE RESPIRATION

that the smoker is not content simply to absorb the nicotine
through the mucous membrane of the mouth ; he draws it
into the lungs. The very mildness of the smoke leads to
inhalation. Hence, as the surface of the lungs is a hundred
times greater than the surface of the mouth, and its lining
much thinner, cigarette smoking is far more injurious than
cigar smoking.

The poison accumulates in the bowl of a pipe ; hence an old pipe
is very injurious. The irritation of tobacco smoke often sets up a
chronic dry catarrh
of the air passages ;
rarely it causes cancer
of lips or tongue. Sir
Henry Thompson
says : " The only per-
sons who enjoy smok-
ing and find it tran-
quillizing at times are
those who smoke in
great moderation.
Men who are rarely
seen without a cigar
between the lips, have
long ceased to enjoy
smoking. They are
confirmed in a habit,
and are merely miser-
able when the cigar is
absent.'' They do not
smoke for pleasure,
but to escape misery
which wiser men
escape by avoiding
tobacco altogether.

FIG. 85. FIG. 86.

FIG. 85. FLATTENED CHEST and waist organs
sunken from wearing tight clothing since the age of
fourteen. Such women often walk with bodies
bent forward to hide the prominent abdomen.

FIG. 86. A NATURAL WOMAN.

PRACTICAL QUES-
TIONS.--!. State

how in the case of a person with round shoulders a gradual remolding
of cartilages (which ones ?), the strengthening of the muscles (which
ones ?), and the practice of deep breathing may each contribute toward

88

HUMAN BIOLOGY

acquiring an erect and perfect figure. 2. Should a hat be well venti-
lated? (A punch for making the holes costs a dime.) Should a hat

be stiff or soft ? 3. Name habits that im-
pair the power of the lungs. 4. How could
you convince a person that a bedroom
should be open while and after it is swept ?
That it should be ventilated at night ?
5. Which is the more injurious to others,
tobacco chewing which causes the ground
to be unclean, or smoking which renders
the air impure ? 6. Why do those who
stand straight up to hoe not get tired half
so quickly as those who bend or " hump "
over ? (Chap. VI.) 7. Why do students
who sit in rocking chairs, or from other
causes lean the head forward when they
study, often find that they recover from
drowsiness if they sit erect, or sit in a
straight chair? 8. How are high collars
a fruitful source of bad colds ? 9. If the
draft up the chimney of the fireplace, when
the fire is burning, takes up a volume of air sufficient for many people,
why is it unnecessary to open a window? 10. Why does cold impure
air make a person colder than cold pure air ? (p. 14.) 11. Do the
modern customs of uniformity in dress for all classes and climates,
shipping foods from great distances, one section or nation imitating the
ways of another section or nation, lead toward health or disease? Do
such customs violate or conform to the great biological law that life is
a process of adaptation to environment?

FIG. 87 .- Suspenders
should have a pulley or
lever at the back, that the
strap on one side may
loosen when one shoulder
is raised.

COLORED FIGURE 6. ORGANS OF THE TRUNK.

, collar bone; r, ribs; z, tongue bone (hyoid) ; k, k, cartilages of larynx; /, windpipe;
s, thyroid gland; rv, right ventricle; Iv, left ventricle; ru, right auricle; IK, left auricle;
a, aorta; ka, artery to head (carotid); sa, subclavian artery; la, pulmonary artery;
oh, superior vena cava; /w, jugular vein; lu, lungs; /", diaphragm; tt>, liver; g, gall
bladder; s, stomach; jr, spleen; , mesentery with vessels; d t small intestine; gd, large
intestine; b, caecum; -w, vermiform appendix ; /t, bladder.

CHAPTER VII

FOOD AND DIGESTION

Experiment i. Tests for Acid, Alkaline, and Neutral Substances.* -
Repeat tests described in General Introduction. 1

Experiment 2. Test for Starch. --See General Introduction.

Experiment 3. Test for Grape Sugar. -- See General Introduction.

Experiment 4. Test for Proteid. - - See General Introduction.

Experiment 5. Test for Fats. --See General Introduction.

Experiment 6. Human Teeth. -- Study the form of teeth from every
part of the mouth. Get a handful from a dentist. Break some of the
teeth to make out their structure. Classify them. Draw section,
enlarged.

Experiment 7. Study of the Teeth. (At home.) - - Sit with the back
to the light and look into a mirror, with the mouth wide open. Do you
see the four kinds of teeth named in text ? Which are fitted for cut-
ting ? Which for grinding? Are any suited for tearing ? Are any of
the teeth pointed? What is the difference in the bicuspids and molars?
Are there any decayed places ? Are the teeth clean ? Are the so-called
canine teeth so long that they project beyond the line of the other teeth,
as they do in a dog? Do the edges of the upper and lower incisors
meet when the mouth is closed, or do they miss each other like the
blades of scissors? How many roots has each lower tooth? (See Fig.
92.) Which tooth has the longest root?

Experiment^. Structure of Mammalian Stomach. --Get a piece of
tripe from the market. Study its several coats. The velvety inner
coat is covered with mucous membrane. (Photomicrograph, Fig. 95.)

Experiment 9. Model of Human Food Tube. --Make a model of the
food tube out of yellow cambric, giving to each organ its correct size.
Follow the dimensions given in text.

Necessity for Foods. - - Growing plants and growing ani-
mals need new material to enable them to increase in size
or grow. Plants never cease to grow while they live;
most mammals attain their full size in one fifth of the time

1 See also Peabody's " Laboratory Exercises in Physiology," Holt, N.Y.

89

QO HUMAN BIOLOGY

occupied by their whole lives. (By this rule how long
ought man to live?) Animals, moreover, move from place
to place, and work with their muscles. The energy for this
comes from the food they eat. Plants do not use food for
this purpose. Another need for food comes from the
necessity for Jieat in all living things. The activities of
animals cause the tissues to wear out, or break down, and
food furnishes material with which new living matter is
built up by the cells and the tissues repaired. We have
already stated the role of oxygen in setting free energy in
the living substance of the cell by oxidizing it. There is
no furnace in the body as in an engine, but the oxidation
occurs in the cells themselves and the fuel is built up into
living matter by the cells before it is oxidized. Plants
must lift mineral from the inorganic to the organic world
before it can be food for animals. Plants can assimilate
minerals ; animals cannot. The body cannot make bone
out of limewater. The iron in iron tonics cannot be used.
Iron makes the grain brown, and the peach red. There
is ten times as much iron in our food as the body needs.

State four reasons why animals need food. Which of
these reasons is very powerful with plants ? Least powerful ?
Absent altogether ? Why is constant breathing necessary
for life ? When is breathing more rapid ? Why? People
who lead what kind of lives usually have poor appetites ?
Good appetites ? Why ? What was the first distinct or-
gan evolved by animals ? (Animal Biology, Chap. IV.)

The Body is a Machine for transferring Energy. - - Energy
cannot be destroyed, but it can be transferred and changed
in form. When a coin is rubbed on the table, muscular
energy, supplied by oxidation in the muscle, produces the
motion. Friction may change motion into heat, and the
coin will become very hot. The uniting of food and

FOOD AND DIGESTION 91

oxygen in the cells of the body gives the heat and motion
(energy) of the body. Only substances which will oxidize,
or burn, are true foods. Water, salt, and carbon dioxid
will not burn ; hence, they cannot give rise to energy in
the body. But the sun energy, acting in the green leaf,
tears apart the carbon from the oxygen (Plant Biology,
Chap. XIII), sets free the oxygen, and the carbon is stored
in starch for future burning. Sunshine is energy (light
and heat). The sun sustains the life of plants and through
them the life of animals. The oxidation in the body is so
slow that it can hardly be called a burning, but it is faster
than the oxidation of iron in rusting or of wood in rotting,
and is about equal to the continual burning of two candles.
The Four Kinds of Nutrients, or Food Stuffs.- -The kinds
of food which we cat seem, to be numberless, but they con-
tain only f am' kinds of food stuffs, starches, fats, proteids,
and minerals. Many foods contain all four classes of
food stuffs. Milk contains sugar (a changed form of
starch), cream (a fat), curd (a proteid), and water (a min-
eral). Oatmeal contains starch, oil, gluten, and water.

USES OF THE NUTRIENTS, OR FOOD STUFFS

1. Proteids. The tissue-building foods (also of value as fuel).

2. Starches (and sugars) 1 Energy and heat (fuel) and

3. Fats (and oils) J fat producing foods.

4. Minerals (water, salt). Important aids in using other foods.

Relative Fuel Value.- -A pound of fat produces as much
heat in the body as 2.3 Ib. of proteid or 2.3 Ib. of starch,
the last two having equal fuel value in the body.

Starch and the sugars are closely related; starch readily
changes into sugar. They contain much carbon and are
called carbohydrates. Starch is especially abundant in
grains, seeds, and fleshy roots (Fig. 88). The sugar in
ripe fruit and in honey is called fruit sugar. Milk sugat

HUMAN BIOLOGY

is found in sweet milk. Grape sugar is found in grapes
and honey ; the small grains seen in raisins consist of

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: ' :^^7j;ji?^^ \

X^^^"* > V\ >Vt, V'l I' .* " .* "-' ' - \ - 5 H "i"^ . *~>i ..fVf * 'X'S -'(

fl^VYVft i i II ill ' fl is-- .. _ - ' i b : . - i :* -T-\V-'i -\

m** >

FIG. 88. A TINY BIT OF POTATO, highly
magnified, showing cells filled with grains
of starch. Cooking bursts these cells.

be prepared artificially
from starch. Cane sugar
is found in cane, in sap
of the maple, and in the
sugar beet (Exps. 2, 3).
Fats include the fats
and oils found in milk,
flesh, and plants. A
fat, such as tallow, is
solid at the ordinary
temperature ; while an
oil, such as olive oil, is
liquid at the same tem-
perature. Tallow was
oil while it was in the
warm body of the ox. Sugar is transformed into fatty
tissue as readily as is fatty food itself.

Proteids are the only foods that contain the tissue-
building nitrogen. Protoplasm cannot be formed without
nitrogen. We do not often see a pure proteid food, for
this food stuff is not so readily separated from foods
containing it as are starch, sugar, and fat. Albu;;zr;/,
or white-of-egg, is proteid united with four times its
weight of water. Pure proteid is also called albu;;//;/.
Coagulation by heat is one test for proteid (Exp. 4).
These are the names of proteids, or albumins, found in
several common foods : casein, the curd or cheesy part of
milk ; myosin of lean meat ; fibrin in blood ; legumin
in beans and peas; gluten, or the sticky part of wet flour;
gelatin in bones. Proteid is valuable to the body as fuel

FOOD AND DIGESTION 93

as well as a tissue builder. We could burn beans and
peas as well as the strictly fuel foods, starch and fat, in
an engine, and get heat to move the engine. If one takes
up athletics or hard physical labor, he should increase the
amount of fats and carbohydrates eaten, but not of proteid.
Muscular activity increases the carbon waste but not the
nitrogen waste of the body.

Minerals.- The iron of the blood and the mineral salts
in bone (carbonate and phosphate of lime) must enter the
body in organic form in order to be used. Water and salt
are mineral foods. The body is about two thirds water.
The cells must do their work under water. They cannot
live when dried. Water enables the blood to flow ; and
the blood is not only the feeder, but also the washer and
cleanser of the tissues. Some persons get out of the habit
of drinking plenty of water, and their health surfers thereby.
In such a case drinking plenty of water will be safer and
more effective than taking poisonous drugs to restore health.

Adulteration of Food. - - Sometimes cheaper materials, of
little or no value as food but of no great injury to health,
are added to foods. Examples: water added to milk,
sawdust to ground spices, chicory to coffee, glucose to
maple syrup. Other forms of adulteration not only cheat
the purse but tend to destroy health, or actually do so.
Examples: Boracic acid or formalin added to milk to
prevent souring, copper to canned peas, etc., to give a
bright green color ; salicylic acid or borax used in minute
quantities as a preservative with canned corn, tomatoes,
etc. ; acids added to " apple " vinegar; dried fruit treated
with sulphur to prevent a dull color. Pure food laws tend
to repress these evils. It is best to buy foods in their
original form. For instance, lemons are more reliable
than vinegar. A bit of lemon at each plate, in house-

94 HUMAN BIOLOGY

holds that can afford it, is far preferable to vinegar. We
should always buy from neighbors when possible. Farmers
and gardeners should do their own drying and canning.
For purity of water, see Chap. X.

The Daily Ration. - -A quarter of a pound (4 oz.) of pro-
teid foods and one pound (16 oz.) of fuel foods (total 20 oz.
of water-free foods) are needed to replace the daily waste
of the body. Hence a balanced ration has proteid and fuel
food in the ratio of 4 to 16, or i to 4. But recent experi-
ments at Yale University indicate that 2 oz. of proteid
daily are more strengthening than four.

Appetite is a perfect guide for those wJw lead an active
life and eat slowly of simple food. Highly seasoned food
and complex mixtures deprave the appetite ; it then leads
astray, instead of guiding safely. Of course the appetite
cannot guide one to eat the right kind and quantity of
food at a table where the food lacks any of the four neces-
sary food stuffs, or where innutritious or indigestible food
is provided. It is well to select one food for a meal be-
cause it is rich in proteids, another because it is rich in fat,
and the third because it is rich in starch or sugar. (See
table, p. 95.) Intelligence in regard to diet enables a
housekeeper to provide nourishing food for less money
than an ignorant housekeeper often pays for food deficient
in nourishing qualities.

A Balanced Ration. - - A deficiency of starch may be
supplied by an excess of fat or sugar. It is most essential
to provide proteid as it cannot be replaced by any other
food stuff. An excess of proteid is most harmful. An ex-
cess of starch or fat is oxidized into water and carbon
dioxid, which are harmless waste products ; an excess of
proteid is changed into urea which may become harmful
by overworking the liver and kidneys which excrete it.

FOOD AVD DIGESTION

95

COMPOSITION OF ONE OUNCE OF VARIOUS FOODS IN FRACTIONS OF

AN OUNCE

PRO

TEIDS

FATS

CARBOHY-
DRATES

WATER

MINERAL
SALTS

WOODY
FIBER

Daily Ration

4 oz.

2 OZ.

14 oz.

2 qt.

I. NUTS.

Pecan

.103

.708

.147

Q>~>

.017

/

^ J

/

Walnut ....

if

574

.16

03

.014

Almonds ....

53

.12

.078

Cocoanut ....

.050

5 1

35

.04

Chestnut ....

037

.02

38

54

.009

.02

II. FRUITS.

Sugar

Peach

.007

.04;

8c.

.007

.OJ.

Apple

/

^ j
.072

!S4

/

.OO Z

^t

T^

j

* j

Blackberry . . .

.005

.040

.86

.004

.OI

Cherrv ,

.cos

.10

.84

.007

.02

J

j

T^

/

Grape

.1C

.70

.OO C

j

/

j

Fig (dried) . . .

.040

.014

5

Banana ....

.050

.20

75

III. ANIMAL FOOL.

Lean beef . . .

.20

035

.009

75

.016

Fat pork ....

.098

.489

390

.023

Smoked ham

25

365

.278

.101

Whitensh ....

.181

.029

.780

.OIO

Poultry ....

.210

.038

.740

.012

Oysters ....

'75

.005

.800

.015

Cow's milk

035

.040

.040

.870

.007

Eggs

.121;

.120

7~" C.

.OIO

j

Cheese ....

335

243

.368

054

Butter

.003

.QIO

.060

.021

IV. PODS OR LEGUMES.

s

Starch

2?

.020

C2

12'

Q^r

.060

' j

* 3 ~

A ** ^

* J '

Peas

217

.oiq

C77

.12

.028

O^2

/

.^s A -y

j 1 1

Peanuts ....

2947

465

.162

.02

.028

043

V. GRAINS.

Wheat flour (white)

.110

.O2O

703

.150

.017

.003

Wheat bread

.080

.015

.490

.400

.OI2

.003

Oatmeal ....

.126

.056

.630

.150

.030

.016

Maize (corn) . .

.IOO

.067

.706

!35

.OI4

.015

Rice

.050

.008

St T O

O \ -^'

.IOO

.OO5

.040

VI. VEGETABLES.

Potatoes ....

.012

.001

.205

.767

.OO9

.OO6

Cabbage ....

.02

.030

.058

.910

.007

.015

96 HUMAN BIOLOGY

Studies based on Table. - -What nuts are rich in proteids ? What
fruits? What animal foods? What legumes? What grains? What foods
are rich in fats? What are rich in carbohydrates? Which grains have
much starch? Which nut? Which fruits have much sugar? A family
was living chiefly on corn bread, potatoes, syrup, cakes, and sweetmeats :
what two of the four food stuffs were deficient in their diet? Another
family lived chiefly on fat pork, bread, rice, vegetables, and fruit : which
food stuff was deficient ? A dozen eggs weigh \\ Ib. Which give
cheaper nourishment, eggs at 15 cents a dozen or beef at 15 cents a
pound? Which is cheapest among the foods abounding in proteid?
Fat ? Carbohydrates? Which is cheaper food, a pound of beef at 20
cents or a pound of pecans at the same price? (Fig. 101.) What food
contains most water? Least water? Which of the foods abounding in

o

proteid is costliest? Cheapest? Notice that nearly all foods contain-
ing much proteid are costly. Water and woody fiber are not counted
as nutriment. What weight of nutriment in I oz. of cow's milk ? If a
quart of whole milk costs 12 cts., what is a quart of skimmed milk
worth ?

How the Right Proportions of Fuel Foods and Proteid are reached by
Different Nations. -- Milk has an excess of nitrogen, and oatmeal an
excess of carbon ; oatmeal and milk form a popular food with the
Scotch. Potatoes are mostly starch and water, and an Irishman who
tried to live on potatoes alone would have to eat seven pounds a day
to get enough proteid. The Irish peasant keeps a cow and chickens ;
by eating milk and eggs he gets along on half the amount of potatoes
named above. The Mexicans eat bread made of corn meal, and supply
the proteid by using beans as a constant article of diet. Hundreds of
millions of people in Asia (the Hindus, Chinese, and others) subsist
mainly on rice, which contains only five per cent of proteid and no fat ;
the chief addition they make is butter, or other fat, and beans, which
contain vegetable proteid.

Outline of Digestion. The food is made soluble in the
alimentary canal and is absorbed by the blood vessels and
lymphatics in its walls. This canal is about thirty feet
long (Figs. 89, 90) and consists of -

(1) The mouth, where the food remains about a minute,
while it is chewed and mixed with the saliva ; the saliva
changes a portion of the starch to malt sugar.

(2) The gullet, a tube nine inches long, running from

FOOD AND DIGESTION

97

mouth to stomach and lying in front of the spinal
column*

Illustrated Study of Food Tract.

FIG. 89. ORGANS OF TRUNK
from the side.

L, larynx; th, thyroid gland; T, trachea;
St y breastbone ; C, heart ; D, dia-
phragm ; F, liver ; E, stomach ; /.
intestine ; Co, colon ; R, rectum ;
V, bladder.

Question : Parts of which organs are far-
ther back than spinal column? Com-
pare this figure with colored Fig. 6.

FIG. 90. DIGESTIVE ORGANS, from the
front (liver turned up).

i, gullet ; 2, stomach ; 3, spleen ; 4, pancreas ;
5, liver (turned upward) ; 6, gall bladder;
7, 8, 9, small intestine; 9', junction of small
with large intestine ; 10, caecum (blind sac) ;
n, vermiform appendix ; 12, 12', 12", ascend-
ing, transverse, and descending colon ; 13,
rectum (straight) just below S-shaped flexure
of colon.

Question: Compare with Fig. 89, and colored
Fig. 6.

(3) The stomach, a large pouch where the food is stored,
and from which it passes in the course of several hours,

H

9 8

HUMAN BIOLOGY

Crown

Enamel

Dentine

having become semi-liquid, and the proteids having been
partly digested by the gastric juice, an acid secretion from
the small glands in the stomach walls.

(4) The small intestine, a narrow tube more than twenty
feet long, where the fats are acted upon for the first time,
and where the starches and proteids are also acted upon,
and where, after about ten hours, the digestion of the
three classes of foods is completed by pancreatic juice
from the pancreas, and bile from the liver.

(5) The large intestine, about five feet long, where the
last remnant of nutriment is absorbed, and the indigestible
materials in the food are gathered together (Exp. 9).

The Teeth. - The main body
of the tooth consists of bone-
like dentine, or ivory. Hard,
shining enamel protects the
crown, or visible portion. The
part of the tooth beneath the
gum is called the neck, and the
part in the bony socket is called
the root. The enamel ends just
beneath the gum, where it is
overlapped by cement of the
root. There is a pulp cavity
in every tooth (Fig. 91); it
contains pulp made up of con-
nective tissue, with nerves and
blood vessels which enter at the
tip of the root (Exp. 6).

The temporary set of teeth is
completed at about two years of age and consists of twenty
teeth. The teeth cannot grow as the jaw grows, and soon
a larger and permanent set starts to growing deeper in the

cavity

Heck

r.oot

Bone

Cement or crust.i petrosa

Alveolar periosteum or root- membrane

FIG. 91. CANINE TOOTH CUT
LENGTHWISE.

FOOD AND DIGESTION

99

jaw. At the age of twelve or thirteen years all the
permanent set have appeared except the four wisdom
teeth, which appear between the ages of seventeen and

3rd rnolar

1st molar

1st premolar y Lateral incisor
2nd molar 2nd premolar Ca;ime Central incisor

FIG. 92. THE PERMANENT TEETH in right half of lower jaw.

twenty-five. The second set not only replaces the twenty
of the first set, but to fill the larger jaws twelve molars are
added, three at the back in each half jaw, making thirty-
two teeth in the second set(Exp.
7). The teeth in each quarter of
the mouth, named in order from
the front, are : two incisors, one
canine, two premolars, three molars.
Care of the Teeth. - The best
way to care for the teeth is to
keep the digestion perfect. Perfect
digestion' tends to preserve the
teeth, and sound teeth tend to

keep the digestion perfect. The teeth should be washed
regularly. Prepared chalk is the best dentifrice. Do not
rub across, but from gums to teeth, to prevent rubbing the
gums loose from the teeth. An unclean brush may har-
bor germs. Toothpicks and dental floss are useful. If
one eats only soft food, in which the mill and the
cooking stove have left no work for the teeth, the teeth
will decay ; for it seems to be a law of nature that
useless organs are removed. The pressure from chewing

-

Fi(i. 93. UPPER JAW WITH
TEETH.

100 HUMAN BIOLOGY

hard food is an aid to the teeth by helping the circulation
and nerves in the pulp. To take a very hot or very cold
drink into the mouth may cause the enamel to crack. If
a tooth aches, or a small decayed place is found in it, a
dentist should be consulted at once. A tooth is so valu-
able to the health that no tooth should be extracted when
it can be saved.

The process of digestion consists in liquefying the food
that it may pass through the walls of the food tube into
the blood, and through the walls of the blood vessels into
the tissues. It is accomplished: (i) by mechanical means,
including the chewing muscles, the teeth, and three layers
of muscles in the walls of the food tube ; (2) by chemical
means, or the action of alkalies and acids upon the food ;
(3) by organic agency, or the action of ferments. A
ferment (or enzyme) is a vegetable substance which has
the power of producing a chemical change in large quanti-
ties of substance brought in contact with it, without being
itself changed. There is one ferment secreted in the mouth,
two in the stomach, and three in the small intestine.

Digestion in the Mouth. Saliva is formed by six glands :
one in the cheek in front of each ear, one at the angle of
each lower jaw, and one pair is beneath the tongue. Each
gland opens into the mouth by a duct. Saliva is ropy
because it is mixed with mucus formed by the mucous
membrane lining the mouth ; it usually contains air bub-
bles. There is a ferment in the saliva called ptyalin, which
has the power of changing starch to malt sugar. If a bit
of bread is chewed for a long time, it becomes sweet,
because some of the starch is changed to sugar. The flow
of saliva is caused by chewing, or by the sight, or even the
thought, of agreeable food. Dryness of food is by far
more powerful than anything else in causing the saliva to

FOOD AND DIGESTION

101

flow. Saliva is secreted only one fourth as fast when eat-
ing oatmeal and milk as when eating dry toast (Fig. 94).

FIG. 94. CELLS OF A SALIVARY GLAND

A, after rest, full of granules ; B, after short activity ; C, after prolonged activity, cells

shriveled and granules lost.

Starchy grains and fruits were eaten by early man without cooking,
and required more chewing than sweet, ripe fruits or oils or proteids.
Hence the saliva was given the power of acting upon the starch, for
it must remain in the mouth longer. The saliva is alkaline ; and if
the food is not thoroughly mixed with it, the stomach digestion will
also be imperfect, for the alkaline saliva is necessary to excite an
abundant flow of gastric juice iti tJie stomach (Exp. i).

Eating slowly is difficult because of the grinding and cooking of
food; hence the common practice of overeating. To eat slowly (i) do
not take large mouthfuls ; (2) do not take a second morsel until the
first has been swallowed ; (3) sit erect or lean back after putting food
into the mouth; (4) the hands should lie idle most of the time. To
lean forward and keep food traveling to the mouth like coal into a
chute means overeating with all its bad effects.

Chewing gum is a coarse and impolite habit, and wastes the saliva,
besides weakening the glands and irritating the stomach by the saliva
that is continually swallowed. Chewing tobacco has several of these
disadvantages, besides allowing the poison in the tobacco to be absorbed
by the mucous lining of the mouth.

The pharynx (far'inks), or throat, is a muscular bag sus-
pended behind the nose and mouth. (See Fig. 89, also
Fig. 83.) There are seven openings into the pharynx : two
from the nostrils, two from the ears, one each from the
mouth, larynx, and gullet. Which of these openings are
downward ?. Forward ? Lateral ?

The gullet (or esophagus) is a muscular tube about nine

IO2

HUMAN BIOLOGY

inches long. (See Fig. 89.) Like the rest of the food tube,
it is lined with mucous membrane. It has two layers of
muscles in its walls, the fibers of one layer running length-
wise, and the fibers of the other layer being circular. In
swallowing, the food does not fall down the gullet of its
own weight, but the circular bands of muscle in front of the
food relax, and those behind it contract and push it on into
t/ie stoniacJi. This wavelike motion is called peristalsis.

The stomach, the greatest enlargement of the food tube,
is like a large bag lying sideways. It lies to the left

side of the abdomen. The
walls of the stomach con-
sist chiefly of muscular
fibers which run lengthwise >
1 crosswise, and slantwise,
making three coats (Exp.
7, also Fig. 95). As soon
as the food reaches the
stomach, the layers of
muscles begin to contract,
changing the size of the
stomach, first in length,
then in breadth, thus
churning the food to and

y. --*

\ \ ' .

'

*3
.

-

jviiBSKSSfiaPW
_T*!sisiB-:r

V

1

FIG. 95. MUSCULAR AND OTHER
LAYERS IN WALL OF STOMACH.

i, mucous lining ; 2, layer of blood vessels
and connective tissue ; 3, muscular
layers (involuntary muscles) ; 4, con-
nective-tissue fibers. (Peabody.)

fro, and mixing it with the
gastric juice, a fluid more
active than the saliva. For
as the food enters the stom-
ach, the mucous membrane lining it turns a bright red,
and many little gastric glands in the lining begin to
secrete gastric juice.

Digestion in the Stomach. The stomach churns the
food from two to four hours after the meal, according to

FOOD AND DIGESTION

103

the kind of food eaten, the way it has been cooked, and
the thoroughness with which it has been chewed. The
gastric juice is chiefly water, and contains two ferments
called pepsin and rennin, and a small quantity of hydro-
chloric acid. Rennin acts upon the curd of milk, and is
abundant only during infancy. Hydrochloric acid kills
germs that may enter the stomach, and changes the food
which has been made alkaline by the saliva into an acid
condition (Exp. i). This enables \\\e pepsin to act upon tJie
proteid part of the food, for pepsin will not act while the
food is alkaline. Gastric juice digests lean meat, which is
a proteid food, by first dissolving the connective tissue that
holds the fibers in place, and they fall apart ; it then acts
upon the fibers separately and makes them soluble. Like
human fatty tissue (Fig. 14), fat meat consists of cells
filled with fat and held together by threads of connective
tissue. The cell walls and the threads, both being proteid,
are soon dissolved by the gastric juice, and the free fat is
melted into oil, but still undigested.
The food is reduced in the stomach to
a creamy, half-fluid mass called chyme.
Where the stomach opens into the
small intestine, there is a folding in or
narrowing of the tube so as to form a
kind of valve called the pylorus. After
the food has been changed to chyme,
this fold relaxes every minute or two,
and allows some of the chyme to
escape into the intestine.

The small intestine is about one inch

in diameter and twenty feet long, with FIG. 96. A PORTION

ij, -, /-n" OF SMALL INTES-

many coils and turns in its course (Fig. TINEcutopentoshow

90). Its mucous lining is wrinkled into the folds in its lining.

IO4

HUMAN BIOLOGY

FIG. 97. LINING OF
SMALL INTESTINE,
magnified, showing villi
and mouths of intestinal
glands.

numerous folds in order to increase the secreting and
absorbing surface (Fig. 96). On and between the folds

are thousands of little threadlike
projections called villi (Fig. 97).
In each villus are found fine capil-
laries and a small lymphatic called
a lacteal (colored Fig. 2). The villi
are so thick that they make the
lining of the intestine like velvet,
and enormously increase the absorb-
ing surface.

Digestion in the Small Intestine. -
This is by far the most active and

important of the digestive organs. The mouth digests
a small part of the starch, and the stomach digests a
small part of the proteid ; the small intestine digests
most of the starcJi, most of tJie proteid, and all of tJie
fats. The food is in the mouth a few minutes, and in the
stomach two or three hours ; it is in the small intestine ten
or twelve hours. There are thousands of small glands
called intestinal glands that open between the villi (Fig.
97) and secrete the intestinal juice, which digests cane
sugar. Besides these, there are two very large and active
glands, the pancreas and liver, which empty into the
intestine by ducts.

The Pancreas. The small intestine is the most impor-
tant of the digestive organs, chiefly because it receives the
secretion from the pancreas, the most important of diges-
tive glands. The pancreas is a long, fiat, pinkisJi gland
situated behind tJie stomach (see Fig. 90). The pancreatic
juice contains three powerful ferments > one of which (amy-
lopsin) digests the starches, another (trypsin) digests pro-
teids, and the third (steapsin),. with the aid of the bile,

FOOD AND DIGESTION

105

breaks up the fats into tiny globules. Fat in small glob-
ules floating in a liquid is called an emulsion ; fresh milk
is an emulsion of cream (Fig. 98). Fat is not changed
to another substance
by digestion, but it is
emulsified, and in this
condition it readily
passes through the
walls of the intestines
and is absorbed by
the lymphatics called
lacteals (colored Fig.
5) found in the villi.

It then ascends
through the tlioracic

duct to a large vein

SMALL
INTESTINE

Mi

VERMIFORM APPENDIX

FIG. 98. JUNCTION OF LARGE AND
SMALL INTESTINE.

at the left side of the

neck (Fig. 100). TJie

digested proteid, starch, and sugar pass into tJie capillaries

of the portal vein, and go to tJie liver on their way to the

general circulation (Fig. 100). The portal circulation

empties into the large ascending vein leading to the

right auricle (Fig. 100).

The Liver. This large, chocolate-colored gland is located just
beneath the diaphragm on the right side (Fig. 90, colored Fig. 6). It
is on a level with the stomach, which it partly overlaps in front. The
liver has three important functions: (i) // is a storeroom; digested
sugar and starch are stored in it as a substance called liver starch (or
gly'cogen). (2) It is a guardian, and destroys poisonous substances
which may be swallowed, and which would otherwise enter the blood.
Twice as much morphine or other poison is necessary to kill a man
when.it is taken by the mouth and passes through the liver as when it
is injected through the skin. Alcohol, morphine, coffee, and drugs are
partly burned up in the liver. (3) It is a gland, and secretes bile.
The bile is made chiefly from waste products and impurities in the

io6

HUMAN BIOLOGY

blood; it is an excretion. Although an excretion, it is of use on its
way out of the body. It is alkaline and helps to neutralize the acid in
the chyme ; it excites the peristalsis, or wavelike motion, of the intes-
tines, and it aids the pancreatic juice to emulsify the fats.

The large intestine, or colon, is about two and one half
inches in diameter and five feet long. The small intestine

joins it in tlie lower rig Jit side of tJie
abdomen (Fig. 90). There is a fold,
or valve, at the juncture, and just
below the juncture there is a tube
attached to the large intestine, called
the appendix, which sometimes be-
comes inflamed, causing a disease
called appendicitis (Figs. 90, 98).
The appendix is a vestigial (vesti-
gium, trace) or rudimentary organ,
long since useless. Absorption of
the watery part of the food continues
in the colon, but the colon secretes no
digestive fluid. The undigested and
innutritious parts of the food are regu-

liver, stomach, and in-
testines.

FIG. 99. DIAGRAM OF
TRUNK to show the
many folds of the PERI-
TONEUM supporting the larly cast out of the colon. 1

tone 1 nm is a membrane with many folds
that supports the food tube (Fig. 99).
Absorption. - The way in which the various digested
foods are absorbed has been stated in several preceding
topics. What is the name of the organs of absorption in
the small intestine ? Which of the following pass into the
lacteals, and which into the capillaries of the portal vein :
sugar, digested proteid, emulsified fats ? Water and salt
need no digestion, and are absorbed all along the ^food

1 No truly refined person will allow business, pleasure, haste, or neglect to
interfere with regular attention to emptying the colon. This is more neces-
sary for real cleanliness than regular baths.

FOOD AND DIGESTION

IO7

tube, the absorption beginning even in the mouth. What
reasons can you give for the absorption of food being
many times greater in the small intestine than in the
stomach ? Through what large tube is the fat carried in
passing from the lacteals to the
veins ? Into what large vein do all
the capillaries that take part in ab-
sorption empty ? (Colored Fig. 5.)
What is the provision for storing
the sugar so that it will not pass
suddenly into the blood after a
meal, but may be given to the blood
gradually ? Food is assimilated, or
changed into living matter (proto-
plasm), in the cells. Blood and
lymph (except the white corpuscles)
are not living matter. (Fig. 100.)

FIG. zoo. THE Two
PATHS OF FOOD ABSORP-
TION. Thoracic duct (for
fats) ; through the portal
vein and liver (for all
other foods).

THOUGHT QUESTIONS. The Digestive
Organs. 1. In which of the digestive
organs is only one kind of secretion fur-
nished by glands? 2. In which organ
are three kinds of secretions furnished by
glands? 3. Which class of food goes

through the lymphatics ? 4. Which classes of foods go through the
liver ? 5. Which classes of foods are digested in only one organ ?
6. Which classes of foods are digested in two organs ? 7. Which
division of the food tube is longest ? Broadest ? Least active ?
Most active ? 8. Soup is absorbed quickly ; why does eating it at
the beginning of a meal tend to prevent overeating?

Hygienic Habits of Eating. In hot weather much
blood goes to the skin and little to the food tube, and di-
gestion is less vigorous. Hearty eaters suffer from heat
in summer because of much fuel, and because the blood is
kept away from the skin where it would become cool and
then cool the whole body. Some persons believe that the

108 HUMAN BIOLOGY

stomach should be humored and given nothing that it di-
gests with difficulty ; others believe that it should be gradu-
ally trained to digest any nutritious food. Some believe that
no animal food should be eaten ; others believe that animal
food is as valuable as any. Some believe that all food
should be eaten raw, but this would irritate a delicate
stomach. It is doubtless best to use no stimulant, either
tea or coffee, pepper or alcohol. Some eat fast and drink
freely at meals ; it is better to eat slowly and drink very
little or none at all while eating, nor soon afterwards.
Some eat five meals a day, and between meals if anything
that tastes good is offered them ; others eat only two or
three meals a day, and never between meals, thus allow-
ing the digestive organs time to rest. Some omit break-
fast and some omit supper. Some prepare most of the
food with grease ; this is a tax upon digestion. Physical
workers often believe in eating the peelings and seeds of
fruits, and partaking freely of weedy vegetables, such as
cabbage, turnip tops, string beans. Mental workers usually
try to reject all woody fiber and indigestible pulp from the
food before swallowing it. Some eat large quantities of
food and digest a small portion ; others eat little but digest
nearly all.

The Power of Adaptation of the Digestive Organs. Of course
some habits of eating are better for the health than others, yet the un-
desirable ways often bring so little injury that they are not discontinued.
This shows that the food tube has great powers of adaptation to dif-
ferent conditions. But there are limits to this adaptation ; there is an
old saying that what is one man's meat is another maiVs poison. A
brain worker cannot follow the same diet as a field hand without work-
ing at a disadvantage. An irritable stomach may be injured by coarse
food that would furnish only a healthful stimulus to a less sensitive one.
A business man who has little leisure at noon should take the heaviest
meal after business hours. In general, it may be said that it does not
make so much difference what is eaten as how it is eaten, and how

FOOD AND DIGESTION 1 09

much is eaten. There is a common tendency to exaggerate the im-
portance of dietetics.

THOUGHT QUESTIONS. Indigestion.-- 1. A Fetid Breath. 1. Name
three causes of bad breath. 2. Let us investigate whether indigestion
could cause a bad breath. In what kind (two qualities) of weather
does meat spoil the quickest? 3. Suppose, that meat or other food is
put into a stomach with its gastric glands exhausted and its muscular
walls tired out, what will be the rate of digestion, and what might hap-
pen to the food ? 4. Odorous contents of the stomach (e.g. onion)
can be taken by the blood to the lungs where it will taint the breath.

After answering the above questions, write in a few words how indi-
gestion may cause a bad breath.

II. A Coated or Foul Tongue. 1. When the doctor visits you, at
what does he first look ? 2. What sometimes forms on old bread ?
(p. 158.) 3. Do you think such a growth possible on undigested
bread in the stomach ? 4. The microscope shows the coating on the
bread to be a growth of mold. If it forms on the walls of the stomach,
it may extend to what ?

III. Stomach Ache. 1. How can you tell whether fruit preserved
in a sealed glass jar is fermenting ? 2. What connection is there be-
tween belching after eating too freely of sweet or starchy food, and the
observation above ? 3. A muscle gives pain when it is stretched.
Why does belching sometimes give relief to an uneasy stomach ?
4. Can you, by using these facts, explain a cause of stomach ache ?

For what Kind of Man were the Human Digestive Organs created ? -
That food is best to which the food tube has been longest accustomed.
It would be of the greatest value as a guide to diet if we knew the food
eaten by early man during the many ages when he led a wild life in the
open air. The organs of early man were doubtless perfectly adapted to
the life he led. The food tube is adapted to the needs of those long
ages, for a few centuries of civilization cannot change the nature of the
digestive organs ; yet some people disregard natural appetites and try
to force the digestive organs to undergo greater changes in a few
months than centuries could bring about.

To test whether an Article of Food belonged to Man's Original Diet.
- Scientists agree that the human race began in a warm country :
that early man was without gristmills , stoves, or fire, and ate his food
raw. If an article of food is pleasant to the taste in its raw, pure state,
there is little doubt that it, or a similar food, was eaten by primitive
man before he knew the use of fire in preparing his food. Apply this
test to the following foods, underlining those foods that pass the test :
apples, bananas, lettuce, turnip greens, turnips, fruits, nuts, beef, fowls,

I IO

HUMAN BIOLOGY

Bread

Bananas

c
o

<S)

rt
J

S-i

0)

I)

o

OS

t~l

o

c

'

o

c

O

Q

CQ

UJ

CQ

eggs, oysters, green corn, cabbage, pork,
watermelons, grains, crabs, fish, white or
Irish potatoes, yams, tomatoes.

The Order in which Man increased his Bill
of Fare. Flesh-eating animals have a short
food tube, as their food is digested quickly ;
they have long, pointed teeth for tearing, sharp
claws for holding, and a rough tongue for rasp-
ing meat from the bones. Man's even teeth,
long food tube, soft and smooth tongue, and
flattened nails, indicate that he is suited for a
diet largely vegetable (see Table, p. in). The
race at first probably ate tree fruits?- both nuts
and fleshy fruits (Fig. 101). Because of
famine, or after migration to colder climates,
and after learning the use of fire, the race prob-
ably began to use flesh for food. Afterward
the hunters became farmers and learned to
cultivate grain, which formed a most important
addition to the food supply, and made possible
a dense population. Coarse, woody foods, like
the leaves and stems of herbs, were probably
added last of all. Woody fiber (cellulose) can
be digested by cattle, but it cannot be digested
by man.

The Natural Guide in Eating is Taste.
Man should preserve his taste uncorrupted as,
next to his conscience, his wisest counselor
and friend. It has been developed and trans-
mitted through countless ages as a precious
heritage. Simple food is more delicious to
people with natural tastes than the most arti-
ficial concoctions are to those with perverted
taste.

Lettuce

Animal Food. - The^7^// of animals
furnishes proteid and fat (Fig. 102).
As cooking coagulates and hardens

1 See Genesis i. 29. Some raw food should be
eaten daily. Pecans are the most digestible of all
nuts. A half dozen or more eaten regularly for
breakfast will prevent constipation or cure it in ten
days or less.

FOOD AND DIGESTION

III

albumin, raw or half-cooked meat is said to be more diges-
tible than cooked meat ; but meat that is not thoroughly

1. sirloin

2. loin

3. rump

4. round

5. top sirloin

6. prime ribs

7. blade

8. chuck

9. neck

10. brisket

11. cross-rib

12. plate

13. navel

14. flank

15. shoulder
1 6 leg

FIG. 102. DIAGRAM SHOWING CUTS OF BEEF.

cooked is dangerous because it may . contain trichinae
("Animal Biology," p. 50) and other parasites. Lean meats
contain much proteid. Some persons who cannot easily
digest starch and sugar because of fermentation eat fat
for a fuel food. Beef tea and beef extracts contain but a
small part of the proteid in meat and all of the waste
matter, including urea.

MAMMALS
COMPARED

CARNIVORA, OR
FLESH-EATERS

HERBIVORA, OR
HERB-EATERS

OMNIVORA, OR

ALL-EATERS

FRUGIVORA, OR
FRUIT-EATERS

Examples.

Cat, dog, lion.

Cow, horse.

Hog, peccary.

Man, monkey.

Length of
food tube.

3 times length
of body.

30 times length
of body.

10 times length
of body.

12 times length
of head-trunk.

Teeth.

Pointed for
tearing flesh.
Canine teeth
long.

Layers of
enamel and
dentine form-
ing ridges.

Cutting teeth
project. Ca-
nines form
tusks.

Teeth even,
close together.
Canines not
projecting.

Digits.

Sharp claws.

Hoofs.

Hoofs.

Flattened nails.

Colon.

Smooth.

Sacculated.

Smooth.

Sacculated.

1 1 2 HUMAN BIOL OGY

Milk of cows is improperly called a perfect food by some writers.
Although it contains the four classes of food stuffs, the proteid is in ex-
cess, the fuel food being deficient. Buttermilk is more digestible than
sweet milk. Buttermilk and sugar form a valuable food for infants.
Skimmed milk still contains the proteid, the most nutritious part of
the milk. Sour milk, or " clabber," and curds pressed into "cottage
cheese " are more digestible than sweet milk. Cream is more easily
digested than butter, which is a solid fat. Cheese is a very concentrated
proteid food, and should be eaten sparingly. Eggs are a valuable food.
Is there more proteid or fat in eggs ? (See Table.) Pork and veal
are the most indigestible of meats. Fish is nearly as nutritious as meat.
There used to be a supposition that fish nourished the brain because
it contains phosphates ; but there are more phosphates in meat than
in fish, and more in grains than in meat.

Grains contain considerable proteid (gluten), but they especially
abound in starch. Wheat flour contains more gluten than corn meal,
hence it is more sticky, and retains the bubbles of gas so that the
dough rises well in bread making. Eggs are sometimes added to
corn meal to make it sticky and cause it to rise well. Which grain has
the largest percentage of oil? (See Table.) Of starch ? Of gluten?
Which is poorest in gluten? Grains may be made to resemble fruit
by long cooking at a high temperature (300 Fahr.), for their starch is
thus changed to dextrin, a substance resembling sugar. You learned
that the starch of fruit is turned into sugar as the sun ripens it. Dex-
trin is yellow and gives the dark color to toasted bread. It is changed
to sugar almost instantly when brought in contact with saliva. It is
used as a paste on postage stamps.

Vegetables contain muck water and woody fiber. White potatoes are
underground stems and are one fiftJi starch. Yams, or sweet potatoes,
resemble roots, and contain both starch and sugar. Beans and peas
are very nutritious. They have been called "' the lean meat of the
vegetable kingdom." They require boiling for several hours. If the
skins are removed by pressing them through a colander, they are very
easy of digestion. This puree of beans makes delicious soup. " Hull-
less beans " and " split peas " are also sold by grocers.

PRACTICAL QUESTIONS.--!. Clothing and shelter for man or
beast economize what kind of food? 2. Why should bread remain
longer in the mouth than meat? 3. In snowballing, what is the ap-
pearance of the hands when they itch from cold? Extreme cold irri-
tates and congests the stomach more quickly than it does the hands.
Why is it that ice water does not satisfy the thirst, but often produces
a craving to drink more water? 4. Should biscuits having a yellow

FOOD AND DIGESTION 113

tint or dark spots due to soda be eaten or thrown away? 5. Why,
during an epidemic, are those who have used alcohol as a beverage
usually the first to be attacked? 6. Do you buy more wood (cellulose)
when you buy beans or when you buy nuts? (p. 95.) 7. Do you buy
more water when you buy bread or when you buy meat? 8. Why do
people who live in overheated rooms often have poor appetites ? (p. 90.)
9. Explain how the stomach may be weakened by the eating of predi-
gested foods. 10. Why are deep breathing and exercises that strengthen
weak abdominal walls better for the liver than are drugs? (See p. 58.)
11. Sixty students at the University of Missouri found by doing with-
out supper that their power to work was greater, their health better,
and many of tliem gained in weight. So they ate only two meals
thereafter. If sixty plowboys tried the experiment, would the result
probably have been the same? 12. If a person began to eat less at
each meal, or only ate one meal a day. yet gained in weight, should he
asree with a friend who told him he was starving himself ? Should he

o

agree if, instead of gaining, he lost weight? 13. Why is half-raw or
soggy bread harder to digest than the raw grain itself ? Which would be
thoroughly chewed and cause a great flow of saliva ? 14. Ask a fat person
whether he drinks much water. A lean person. 15. Why is one whose
waist measures more than his chest a bad life insurance risk ? 16. What
changes in habits tend to make a rheumatic middle-aged person more
youthful? 17. How is the ingenious ' fireless cooker " constructed?

Atwater's Experiments with Alcohol. - - A few years ago
Professor Atwater proved that if alcohol is taken in small
quantities, it is so completely burned in the body that not
over two per cent is excreted. He inferred that it is a
food, since it gives heat to the body and possibly gives
energy also. His experiments did not show whether any
organ was weakened or injured by its use. As alcohol is
chiefly burned in the liver, it probably cannot supply
energy as is the case with food burned in nerve cell and
muscle cell. The heat supplied by its burning is largely
lost by the rush of blood to the skin usually caused by
drinking the alcohol. Dr. Beebe, unlike Professor Atwater,
experimented upon persons who had never taken alcohol,
and whose bodies had not had time to become trained to
resist its evil effects. He found that it caused an increased

I 1 4 HUMAN BIOL OGY

excretion of nitrogen. When the body became used to it,
this decreased, but the proteid excreted by the kidneys
contained an abnormal amount of a harmful material called
uric acid. Uric acid, a substance which is present in
rheumatism and other diseases, is usually destroyed by
the liver. As the burden of destroying the alcohol falls
chiefly upon the liver, it is not surprising to find that it is
so weakened and injured by alcoholic drink that it cannot
fully perform its important functions. Bright's disease
and other diseases accompanied by uric acid are more
frequent among persons who use alcoholic drinks.

Definition of Food. A food is anything which, after being absorbed
by the body, nourishes the body without injuring it. Does alcohol or
tobacco come within this definition ?

Advantages of Good Cooking. - - Taste and flavor may be developed ;
parasites are killed ; taste may be improved by combining foods ; starch
grains are burst and the food softened. Thus digestion is aided.

Disadvantages of Bad Cooking. - - Proteid foods are hardened ; flavors
may be driven off; too many kinds of food may be mixed; cooked
vegetables are more likely to ferment than raw vegetables ; palatable
food may be made tasteless or soggy or greasy ; soda and other indiges-
tible ingredients may be added ; food may be so highly seasoned as to
cause catarrh of the stomach ; it may so stimulate the appetite that so
much is eaten as to overload the stomach. Food may be made so soft
that it cannot be chewed and is eaten too rapidly; for instance, bread
shortened with much grease.

The Five Modes of Cooking. -- Food may be cooked (i) by heat
radiating from glowing coals or a flame, as in broiling; (2) by hot
air, as baking in a hot oven ; (3) by boiling in hot water or grease, as
frying; (4) by hot water, not boiling, as in stewing ; (5) by steaming.

Radiant Heat. - - Toasting bread and broiling meat are examples.
The meat should be turned over every ten seconds to send its juices
back and forth, thus preventing their escape, and broiling the meat
in the heat of its own juices. Roasting is an example of this
method combined with the second method. The fire should be hot at
first in order to sear the outside of the meat and prevent the escape of
its juices. If the piece roasted is small, the hot fire may be kept up ;
but if it is large, a longer time is required, and the fire should be
decreased, otherwise the outside will be scorched before the central part

FOOD AND DIGESTION I 15

becomes heated. White, or Irish, potatoes roasted with their skins on
best retain their flavor as well as valuable mineral salts (potash, etc.).

Cooking by hot air can only be used with moist foods. Baking is an
example. Foods only slightly moist are made hard, dry, and unpalatable
if cooked by this method.

Cooking by Boiling. - - To boil potatoes so as to make them mealy
instead of soggy, the water should be boiling when they are put in, and
after they are cooked the water should be poured off and the pot set on the
back of the stove for the potatoes to dry. Boiling onions drives off the
acrid, irritating oil. Rapid boiling of vegetables gives less time for the
water to dissolve out the nutrients. (See Steaming.) Raw cabbage is
treated by the stomach as a foreign substance, and sent promptly to the
intestine ; cabbage boiled with fat may remain in the stomach for five
hours. Instead, it should be boiled in clear water for twenty minutes.
Beans and peas require several hours' boiling.

Cooking in hot liquid below the boiling point is better than boiling.
In frying meat, it should be put in hot grease that a crust may be formed
to prevent the grease from soaking in. Grease much above boiling point
becomes decomposed into fatty acids and other indigestible products.
Hence butter is more digestible than cooked fats. In whatever way
meat is cooked, it should never be salted until the cooking is finished
or the salt will draw out the juices which flavor it. Eggs may be
cooked by placing them in boiling water and setting the kettle off the
stove at once to cool. A finely minced hard-boiled egg is as digestible
as a soft-boiled egg. Since boiling for more than a very few minutes
coagulates and hardens albumin, there is no such thing as boiling meat
without making it tough and leathery throughout. It may be stewed,
a process which belongs to the next method.

In stewing meat, it may be plunged into boiling water for a few min-
utes ; this coagulates the albumin on the surface. The fire should then
be reduced, or the vessel set on the cooler part of the stove, or a metal
plate should be placed beneath it, that the water may barely simmer.
The water should show a temperature of 185 or rgo D if tested with a
thermometer. A piece of meat cooked in this way is tender and juicy.

Cooking by steam requires a double vessel or a vessel with a per-
forated second bottom above the water, through which the steam may
rise to the food that is to be steamed. Steamed vegetables have a better
flavor and are more nutritious than those cooked in any other way. A
steamer is different from a double boiler. Oatmeal should be cooked
for at least forty minutes, and it is more digestible if steamed for several
hours until it is a jelly. To do this, it may be cooked during the prepa-
ration of two meals. Cooking that leaves it lumpy and sticky is a dis-
advantage, and makes it more likely to ferment than if eaten raw.

I 1 6 HUMAN BIOL OG Y

THOUGHT QUESTIONS. Cooking. Meat. 1. In making soup, why
should the meat be put in while the water is cold? 2. In roasting
meat, why should the oven be hot at first, and more moderate after-
ward? How should you regulate the temperature in boiling or stewing
meat? 3. What happens to salt or anything salty on a cloudy, damp
day? This is because the salt attracts - . This shows that meat
should not be salted until after it has been cooked, because if salted be-
fore - . 4. Very tough meat should be b ed or st ed. 5. Meat
may be prevented from becoming grease-soaked when frying by having
the grease very - , use very - , simply greasing the - .

6. Bread. Bread crust causes the - - to be used more and cleans
them. It will not - - together in the stomach like the crumb. It
increases the quantity of the , and is more digestible than the
crumb, since the - has been changed by slow heat to - (p.
112). Therefore loaves or biscuit should be (large or small?) and they
should (touch or be separated?) in a pan. 7. How can you tell
whether the oven has been too hot while the bread was baking? 8.
Why can you tell best about the digestibility of bread when you are
slicing it? 9. Regulating the heat is the greatest art of the cook.
How may the temperature of the oven be lowered by means of the
damper? The draft? The fuel?

EXERCISES IN WRITING. - - Story of a Savage who went to dwell in
a City (his trouble with artificial ways). Is it easier to learn Physi-
ology or to practice it ? How to make Bread. Describe People seen
in an Audience (tell what their appearance suggests). A Scene at a
Dinner Table. Thoughts of a Physician on his Round of Visits.
A Good Cook. A Bad Cook. Is Cooking a Greater Accomplishment
than Piano Playing? Common Causes of Illness. The Influence of
Imperfect Digestion upon the Other Organs. Effect of Lack of
Muscular Activity. The Way of the Transgressor is Hard. What
Fools we Mortals be! Health Fads. Temperance in all Things.
The Right Way the Easiest. Looking Back. Looking Forward.
Hygiene of the Schoolroom. Patent Medicines. Microbes. Mind
Cure. Nervous Women. Dissipated Men. How a Friend of mine
lost his Health. Why a Friend of mine is Sound and Strong. Tobacco.
It never pays to neglect the Health. Which does more Harm, an Ig-
norant Cook or an Ignorant Janitor? A Visit to a Sick Room. Alco-
hol and Crime. Natural Instincts and Appetites; how preserved,
how lost. A Lesson about Alcohol based upon the Morning News.
Effects of Alcohol upon the Greatness of our Country (workmen, voters,
soldiers, children). Adam's Apothecary Shop. Adam's Ale (water).

CHAPTER VIII

THE NERVOUS SYSTEM

Review Questions introducing this Subject. - - What is a cell? What
are the five supporting tissues? What are the two master tissues?
Why are they so called? What kind of cells have many branches?
Does the food ever come in contact with the salivary glands? When
you look at a basket of apples, the sight makes your mouth water. 1 '
Is there a connection between the eye and the mouth? What two tis-
sues enable the skin to blanch and to blush? Do the different organs
share the blood in the same proportions at all times? How can this
proportion be changed? How is the brain protected from injury?
How is the spinal cord protected? Is the hole for the spinal cord
through the main body of the vertebra, or behind the main body?

Harmonious Activity. - - Strike suddenly at the eye of

*

another, and the lids fall to protect it, and the hands rise
to ward off the blow. If a grain of dust gets into the eye,
the tear glands form tears to wash it out. If you touch
the hand unexpectedly to a hot iron, the muscles of the
arm jerk the hand away. If the foot of a sleeping person
is tickled, the muscles of the leg pull it away. Many
muscles cooperate in the act of running. If the human
being were merely an assemblage of working organs, the
organs might act independently, and there would be such
confusion that the body would be powerless, and life could
not be maintained. The nervous system enables the or-
gans to work together for the common good. Why does
an ameba not need a nervous system ?

The Need of Nerve Centers as well as Nerves. - - If there
were no central office in a telephone system of one thou-
sand subscribers, then every subscriber, in order to com-

117

u8

HUMAN BIOLOGY

-/node

Mtfe-

FIG. 103. Showing a NEU-
RON, A, or nerve cell with
all its parts dendrites,
cell body, and axon ; B, a
portion of a white fiber
highly magnified. (Jegi.)

municate with every other sub-
scriber, would need one thousand
wires running into his house ; all
together, there would have to be
several hundred thousand (to be
exact, 499,500) wires. With a cen-
tral office only one thousand are
needed. As a telephone system
has central offices, so the nervous
system has nerve centers. Nerve
centers contain nerve cells. Al-
though there are some subordinate
nerve centers in the spinal cord,
the greatest collection of nerve
centers in our bodies is in the skull,
and is called the brain. Fishes
were the lowest animals studied in
animal biology found to possess a
true brain.

The nervous system, unlike a
telephone system, has other duties
besides allowing communication.
It enables us to think, and, after
reflection, to will and to act by con-
trolling the various organs.

The Units of which the Nervous
System is Constructed. - - A nerve
cell with all its branches, or fibers,
is called a neuron (see Fig. 103);
some neuron branches are several
feet long. Neurons are the units
that compose the nervous system.
The living substance in cells is

THE NERVOUS SYSTEM

119

FIG. 104. LARGE NERVE TRUNK,
such as supplies the muscles.
Cross-section (magnified 6 diam-
eters), showing bundles of nerve
fibers. (Peabody.)

called protoplasm. The protoplasm in nerve cells possesses

the most marvelous and varied powers of any known sub-
stance, for the nerve cells are

the seat of the mind.

Nerve Cells and Fibers.

The many branches of nerve

cells make them the most

remarkable of all cells for

irregularity in shape. Since

the protoplasm of the cell con-
tinues into the fibers, it is

plainly wrong to consider the

nerve cell as something apart

from its fibers. It is not a

complete cell without them.

A cell usually has many short

branches called dcndrons or

dendrites (SQQ Fig. 103) for communicating
with near-by cells, and one long branch
called an axon (Fig. 103) for communicat-
ing with distant parts. The axons form

X \ / I

} I II the fibers that go to the skin, muscles,
and other organs.

A Nerve.- These long branches, or
axons, of nerve cells go all over the body
and are often bound together into visible
cords called nerves, or nerve trunks (Fig.
104).
White and Gray Fibers (Fig. 105).-

6 W

Some fibers have a fatty covering sur-

FlG. 105. c, a white

fiber with its fatty rounding the thread of protoplasm ; they
sheath (dark); d, are w }^ te anc j glistening, and are called

two gray fibers

(without sheath), w kite fibers. Others are without this fatty

I2O

HUMAN BIOLOGY

covering, and are called gray fibers. Both kinds of fibers
have connective tissue on the outside to strengthen them.
If we let a lead pencil represent a white fiber, the lead
corresponds to the axis of protoplasm ; the wood corre-
sponds to the white, shiny fat that surrounds it ; and the
varnish corresponds to connective tissue on the surface
of the fiber. A number of white fibers together makes
a white mass that is called white matter. The axis of a
white fiber, of course, is not white. A mass of cells or of
gray fibers is called gray matter. The oxidation of the
gray matter, or protoplasm, in neurons gives rise to nerve
energy.

Feeling Cells and Working Cells. - - Nerve cells are
divided into two classes : sensory cells, which feel or receive
impressions ; and motor cells, which send out impressions
to the working organs. Those fibers which carry impres-
sions to the receiving cells are called sensory fibers ; those
which carry impulses from the cells to the working organs
are called motor fibers.

Ganglia and Nerve Centers. - - Nerve cells are not scat-
tered uniformly in nervous tissue, but are gathered into
groups. A group of nerve cells is called a
ganglion (Fig. 106). One or more ganglia
having a single function, such as to control
the muscles of breathing, form what is called
a nerve center. The brain consists of a
number of nerve centers with their connect-
ing fibers.

Gross Structure of the Spinal Cord. - The
nerve fibers from nearly all over the body
lead to cells situated in a large cord in the spinal column
called the spinal cord. The spinal cord is separated by
a deep fissure almost into halves (Fig. 107). The cells

FIG. 106. A
GANGLION.

THE NERVOUS SYSTEM

121

are situated in the central portion of each half, and the
two masses of gray matter thus formed are connected by a
narrow isthmus of gray matter.
The outer part of the cord
consists chiefly of white fibers.
The white matter is thus on the
outside of the cord (Fig. 107).
The brain, unlike the cord, has
the gray matter on the outside
and the white matter on the in-
side. For microscopic study of
the spinal cord, see Fig. 108.

FIG. 107. CROSS-SECTION OF
SPINAL CORD, showing area
of gray matter (dark).

The Work of the Spinal Cord.- -There are two functions
of the cord : reflex action and transmission of impulses

from the body to the brain.
Reflex action is action that
takes place without the aid
of the will.

Reflex action never begins
in the cord, but at the outer
end of a sensory fiber, usu-
ally located in the skin.
The impression goes to the
cord along a sensory fiber.
It is received in a sensory
cell and transferred by den-
drons to a motor cell which
sends back an impulse along
a motor fiber to a muscle ;
the muscle contracts and
the action is complete. At
least two nerve cells are necessary for reflex action. The
actions of the lowest animals are almost entirely reflex.

..,..

*.""'*> ?*=.

* ;

.

v. .-

* ., ..

^0:1, .-i. M ..,_- .-- ..-,. .:>.:;

FIG. 108. SECTION OF SPINAL
CORD, showing nerve cells (large
black spots) with their branches
(black dots and lines). Five
bundles of nerve fibers are shown
near upper margin. (Peabody.)

122

HUMAN BIOLOGY

Reflex Action, Consciousness, and Will. - -Usually not all
of the force of the impulse is transferred to the motor cell.
The sensory cell by means of another of its many branches
may transfer part of tJie impulse to a cell which sends it to
the brain. Hence a reflex act is not necessarily an uncon-
scious one. If you unintentionally touch the hand to a
hot stove pipe, you may be conscious of the pain and the
involuntary jerking away of the hand at the same time.
Reflex Action and the Will. - The will may inhibit, or
prevent, an expected reflex act. Yet many reflex acts

occur in spite of the effort of the will to
prevent them. One cannot always keep
from closing the eyes before a threatened
blow even if from the other side of a plate
glass window, and it is known there is no
danger. Sneezing is a reflex act and can-
not always be prevented. The forming of
saliva and other secretions are reflex acts.
Reflex acts are quicker than voluntary acts.
An eighth of a second is about the time
required for a person to press an electric
button after seeing a signal ; a reflex act
may occur in a shorter time.

The Brain consists of Three Chief Parts.
-(i) There is an enlargement at the top
of the spinal cord called the medulla, or
the medulla oblongata. It may be re-
garded as the part of the spinal cord
within the skull (see Figs. 109, no, 114).
(2) Above the medulla is the cerebellum,

or little brain. (3) The cerebrum, or large

tfa gkull except the sma n

CORD. part occupied by the medulla and cere-

I

K

H

FIG. I0 9 . BRAIN brai fin

AND SPINAL

THE NERVOUS SYSTEM

123

bellum. The cerebrum covers the cerebellum. (Fig.
no.) Is this true of the monkey's brain? (See Fig.

US-)
The work of the medulla is chiefly to control the vital

functions (see Figs, no, 114). Here are located the
centers for regulating the
breathing, the heart beat, the
size of the blood vessels (thus
regulating nutrition), and also
the less important centers
that control swallowing, secre-
tion of saliva, and vomiting.

The center for breathing is

FIG. no. --THE BRAIN (cerebrum,
cerebellum, medulla).

sometimes called the vital
knot, because although the
cerebrum and cerebellum may be removed from an animal
without causing immediate death, the slightest injury
to the vital knot kills the animal at once. In cases of

hanging, death is caused by
injury to this center.

Automatic Action.- The
center called the vital knot
is said to regulate the
breathing automatically, not
reflexly. Reflex acts start
in the skin ; automatic acts
start in the interior of the
body. The condition of the blood regulates the breathing
automatically during sleep, and partly regulates it during
waking. If too much carbon dioxid accumulates in the
blood this excites the vital knot, which sends out stronger
impulses to the respiratory muscles. Deeper breathing
follows, which purifies the blood, and the breathing is then

FIG. in. ASSOCIATION FIBERS, con-
necting cells within the cerebrum.
(Jegi.)

124

HUMAN BIOLOGY

shallow or slow until carbon dioxid accumulates again.
The Four Kinds of Nerve Action and the Centers that con-
trol them. The cord controls chiefly reflex action ; the
medulla controls chiefly automatic action ; the cerebellum

controls chiefly coordinate, or
harmonizing, action ; the cere-
brum controls the purely vol-
untary acts, for it is the seat
of consciousness and thought.
The medulla, like the cord,
has the gray matter on the
inside (Fig. 109).

Structure of the Cere-

FlG. 112. SENSORY AND MOTOR

FIBERS. (Jegi.)

bellum. - The cerebellum,
like the cerebrum, has the
gray matter or cells on the outside. The gray matter is
folded into furrows that are not nearly so winding as the
folds in the cerebrum (see Fig. 115). The fibers going
to the surface
cells have a
branched arrange-
ment called the
arbor vita, or tree
of life, which is
shown where the
cerebellum is cut.

FIG. 113. BRAIN OF A MONKEY. Numerals
show location of motor centers. (See Fig. 115.)

The cerebellum,
like the cere-
brum, is deeply
cleft and thus divided into halves, called hemispheres,
connected by a band of white matter.

The work of the cerebellum is to aid the cerebrum in
controlling the muscles. It coordinates the muscular move-

THE NERVOUS SYSTEM

125

ments ; that is, it makes the
muscles act at the right
time and with due force in
complex acts, such as stand-
ing, walking, talking. A
man could strike just as
hard without the action of
the cerebellum, but he would
not be likely to hit what he
aimed at. A drunken
man staggers and fails to
control the muscles in walk-
ing because the alcohol has
caused the blood to collect
and congest around the
cerebellum and press upon
it. One whose cerebellum
has been injured by accident

Cereb^m

FIG. 114. --THE LOBES OF THE RIGHT
SIDE OF BRAIN and their functions.
(Jegi.)

The speech center is true only for left-handed
persons. Medulla is marked " Bulb."

staggers like a drunken man.

Coverings of
the Brain. - - Lin-
ing the skull and
covering the cere-
brum are found
two membranes
which inclose a
lymph-like fluid.
Thus a kind of
water bedis made
which surrounds
the soft and deli-

cate cerebrum
FIG. 115. MOTOR AND SENSORY AREAS OF LEFT

HEMISPHERE. Speech center marked " Lips." P 1

In what region are the motor centers? The sensory centers? I T O IT1 jars. J\

126 HUMAN BIOLOGY

membraneous net, or meshwork, of blood vessels covers
the cerebrum and plentifully supplies it with blood.

Structure of the Cerebrum. - - The gray matter, or cell
mass of the cerebrum, forms a surface layer, called the
cortex (" bark "), about one eighth of an inch thick. This
gray layer is deeply folded, the folds, or convolutions, being
separated by deep furrows, some of them an inch deep
(see Fig. no). Thus the area of the surface layer is
increased to several times what it would be if smooth.
Intelligence increases with increase in the number and
depth of the convolutions. The greater part of the cere-
brum is white matter. This consists largely of associa-
tion aly^r.*- (Fig. in) which connect the cells in the gray
matter with eacJi other and with important interior ganglia
at the base of the cerebrum (Fig. 112). These basal
ganglia are the largest parts of the brains of the lower
vertebrates (Animal Biology, Figs. 222, 259). Why do
these animals not need large cerebrums ? The human
cerebrum comprises nearly seven eighths of the weight
of the brain. A deep fissure divides it into the right and
left cerebral hemispheres. A band of white matter con-
nects the hemispheres.

Functions of the Cerebrum. The cerebrum is the seat of
consciousness and thought, and of all activity controlled by
the will. It also directs the work of tJie lower nerve centers
in the spinal cord, medulla, and cerebellum.

It receives sensory messages from all parts of the skin
and through the special senses. It sends out motor mes-
sages to all the voluntary muscles, and more indirectly
to the involuntary muscles. The cerebral fibers are of
three kinds : sensory, associational (connecting cells in cere-
brum), and motor (Figs. 111,112). It is estimated that the
cerebrum alone contains 9,200,000,000 cells.

THE NERVOUS SYSTEM I2/

Spinal and Cranial Nerves. - - The nerves from the spinal cord go
out through notches between the vertebrae. Since there are tliirty-one
pairs of spinal nerves (Fig. 109) and only twenty-four vertebras, some
of the nerves go out through holes in the sacrum. The cranial nerves
(to eyes, ears, tongue, nose, face, etc.) leave the brain through holes in
the cranium, or skull. There are twelve pairs of them.

Relation of the Cerebrum to the Lower Centers. As already stated,
nerve activities are of four kinds, reflex, automatic, coordinate, and
voluntary. A manufactory has more complex work than a shop. A
man with a shop may enlarge it into a factory and leave trained assist-
ants in charge of the different shops, keeping only the general man-
agement for himself. If he should cease to control his assistants
entirely, the work of the factory would soon be in disorder. If the
manager should try to direct everything, he would become exhausted.
So the cerebrum, the seat of the will and the reason, leaves the reflex
centers in the spinal cord, medulla, and cerebellum to do most of the
work. If the mind wishes the hand to move and grasp the hand of
a friend, the motor center in the cerebrum sends a message to the
cerebellum; and if the cerebellum has been well trained, the act is
accurately performed.

A less imperfect wisdom than that of the mind is in the lower
nerve centers. The reason and will control the lo\ver centers through

O

the cerebrum, but the control is very limited. It is well that this is
so, not only for the relief of the cerebrum, but for the safety of the
body. Can you change the rate of the heart beat by the exercise of
the will? Can you blush at will, or prevent the flushing of the capil-
laries when you are embarrassed, or when you go close to a hot fire?
It is impossible for a person to commit suicide by holding the breath.
What change in the blood would soon force a breath to be taken?
Repeat the two examples of reflex action triumphing over the will
which have already been given. We shall next take up a system of
nerves almost independent of the will.

The ganglionic or sympathetic portion of the nervous
system controls the viscera (vis'se-ra\ or internal organs,
e.g. peristalsis of food tube, tone of arteries. The nerves
that go to the viscera branch off from the spinal nerves
not far from the spinal column, and enter a row of ganglia
on each side of the spine (see Fig. 115). Each ganglion
is connected by nerves with the one above and below it,
so that they appear like two knotted cords suspended one

128

HUMAN BIOLOGY

on each side of the spinal column and tied together below ;
for both chains of ganglia end in the same ganglion in
the pelvis. Some of the fibers from the spinal cord pass
through these ganglia on their way to the viscera, losing
their white sheaths in the ganglia and emerging as gray
fibers. The spinal cord and brain with the fibers which
do not pass through the double chain of ganglia are called

the cerebro - spinal system.
The double chain of ganglia
and the fibers which go
through them are called the
ganglionic or sympathetic
system.

Why these Nerves are
called the Sympathetic
System.- These nerves,
after leaving the double
chain of ganglia, form many
intricate networks of ganglia
and fibers. Each network
is called a plexus (Fig. 116).
The largest of the plexuses
is just back of the stomach,
and is called the solar plexus.
A blow upon the stomach
may paralyze this plexus
and cause sudden death. The plexuses and fibers con-
nect tJie viscera so perfectly tJiat one organ cannot suffer
without the otJiers changing their activity, or sympathizing
with it. An overloaded stomach causes the heart to
beat faster and send it more blood ; a loss of appetite
usually accompanies illness and allows the stomach to
rest. This sympathy is necessary, for if one organ is

FIG. 116. DIAGRAM OF SYMPA-
THETIC SYSTEM showing double
chain of ganglia ; also plexus at
heart and solar plexus.

THE NERVOUS SYSTEM 129

diseased, the others do not continue to work and tax
the strength of the ailing organ.

How the Sympathetic and Cerebro-spinal Nerves Differ.
The ganglionic nerves (i) contain mostly gray fibers ;

(2) pass through ganglia after leaving the spinal cord ;

(3) control the unconscious activities of the body ; (4) pass
to organs which contain slow-acting involuntary muscles,
not to sense organs and quick-acting voluntary muscles ;
(5) transmit impulses sloivly (about 20 ft. instead of 100
ft. per second). Crawfish and insects have hardly more
than the ganglionic system of nerves (Animal Biology,
Figs. 92, 132, 197).

Examples of the Supervisory Functions of the Sympa-
thetic System. - - Regulation of the heart beat and of the
size of the blood vessels ; secretion of sweat glands ; con-
traction of pupils of eyes in a brigrBbght; peristalsis.

Examples of Sympathetic Nerve Impulses reaching Con-
sciousness. Pain in colic and cramps; "heartburn'
(pain in stomach from indigestion); backache (from
nerves in organs prolapsed by tight clothing pulling upon
their attachments at spine) ; hunger ; thirst.

The Mind and Health. --A contented or peaceful mind is indispen-
sable to soundest health. Worry causes difficult breathing with bated
breath. Happiness brings full, easy breathing. Biological study of
physiology shows the futility of making health a care or anxiety, and
teaches "'no meddling 1 ' with the body, whether by stimulating it, drug-
ging it, deforming it, overheating it, half smothering it in close rooms,
cultivating artificial instincts, etc. If the body degenerates through
wrong living, and disease ensues, a new way of living is needed, not
some quick and wonderful remedy. The new life will renew the body
and nothing else can.

HYGIENE OF THE NERVOUS SYSTEM

Necessity of Food, Fresh Air, and Rest for Sound Nerves.
- The health of the nerves depends upon a free supply of
K

130

HUMAN BIOLOGY

B.

pure, nutritious blood. Nearly one fifth of the blood goes
to the brain. It is clear that the brain cannot give out
energy until it has first received it; the blood supplies
energy to the brain. The blood in turn receives the nour-
ishment from food and pure
air. A rested cell is full of
nourishment ; a tired cell is
shriveled (see Fig. 117).

Sleep. During waking
hours energy is used up
faster than it is stored in
the cells, and protoplasm is
oxidized faster than the
cells can replace it. Dur-
ing sleep the opposite is
true ; repair is more rapid
than waste. During sleep
the muscles are strength-
ened, the breathing is less,
the heart beats more slowly,
less heat is produced, diges-
tion is slower, less blood goes to the brain. Why is it
necessary to be more warmly protected by clothing or bed
covering when asleep than when awake ? Above all, the
nervous system has an opportunity to recuperate from the
constant activity of waking hours. The eye and the ear
are rested by darkness and silence. Sleep caused by
morphine or other drug is not normal sleep and brings
little refreshment.

Practical Suggestions. - - Sleep is deepest during the second hour
after going to sleep, and a greater shock is given to the nervous system
by waking a sleeper during that hour than at another time. An alarm
clock is a very unhealthful device. One who cannot trust to nature

FIG. 117. EFFECTS OF FATIGUE ON
NERVE CELLS.

A, resting cell, B, fatigued cell, with its
body and nucleus shrunken.

THE NERVOUS SYSTEM 131

even to awaken has great presumption. If one does not rise promptly
upon waking naturally, the instinct to awake when enough sleep has
been taken will be lost, and the habit of sleeping too much will be
formed, and the brain, like the muscles, will become weak from
inactivity. Infants sleep most of the time, and it is injurious to them to
be waked. Adults usually require about eight hours of sleep. There is
a risk in going to sleep in a warm room, for the bed covering which is
comfortable then may not be enough to prevent taking cold when the
fire goes out. Sleep usually comes more promptly to one who goes to
bed at the same hour each night. The muscles are relaxed in sleep,
and relaxing them perfectly upon lying down and breathing slowly,
tends to bring sleep. One who is sleepless usually finds that he is
breathing fast and is holding the head stiff on the shoulders, the teeth
clenched, and the muscles contracted, even though he is lying down.
Excitement and worry during the day, but especially just before retiring,
tend to produce sleeplessness. One who overworks his mind by too
great attention to business is inviting ruin. A student who loses sleep
while preparing for an examination will probably fail. Rested brain
cells and pure blood are needed for good w r ork.

Rules for Preventing Sleepiness. -- (i) Do not sit close to stove or
especially a fireplace or in very warm room, and do not wear very
warm clothing in the house. (2) Let in fresh air freely. (3) Do not
sit in rocking chair nor with chest flattened. (4) Make the last meal a
very light one.

Habits. - - Our habits of doing and thinking and feeling
really constitute our characters. This shows the impor-
tance of right habits. By gradually changing our habits
we can strengthen our characters and form them somewhat
as we wish. When a muscle contracts in a certain way,
this act makes it easier for the muscle to contract in that
way the next time ; thus great muscular strength may be
developed. When a nerve cell acts, the circulation around
the cell is increased, tJie fibers develop by use, and tlie act
is easier tJie next time. We cannot entirely get rid of our
habits, because we cannot get rid of our brains.

Healthy fatigue is caused by the accumulation of waste
products resulting from the oxidation of substances in
nerve, muscle, and gland cells. The presence of waste in

132

HUMAN BIOLOGY

the tissues affects the nerves. We are rested and strong
when these wastes are removed and the tissues are sup-
plied with fresh food and oxygen. Work causes the ac-
cumulation of carbon dioxid, wJiicJi is nature s narcotic!
The drowsy feeling that ensues is more pleasant than the
drowsy feeling from alcohol or opium. Those who do
not employ nature's narcotic but free themselves of it by
hurried, anxious breathing become restless and crave arti-
ficial narcotics.

Fatigue without work occurs with people who are idle.
The oxidation in their cells is not complete, and poisonous
products of the incomplete burning result. This is known
as self-poisoning (auto-toxemia). The poisons are taken
by the blood to the nerves and brain, and give a tired feel-
ing as effectually as does hard work ; or the food may fer-
ment in the food
tube and form poi-
sons which increase
the tired feeling.
Such persons are
usually irritable,
while persons who
are fatigued by use-
ful labor are likely
to be dull and
drowsy.

Headaches are
caused by poisons

in the blood or by pressure of blood congested in the head.
Like all other pains they should be a source of benefit in

1 It has been found that it is injurious to rebreathe expired air containing
one per cent of carbon dioxid, but a far greater percentage is harmless if intro-
duced into fresh air, thus indicating that the injury from poor ventilation
comes chiefly from the " crowd poison," or organic particles thrown off.

DYSPEPSIA .^fay-^
CONSTIPATION

DISTURBANCES Of

N05, EAR, Af/0
TTH

-MERVQUS EXHAUSTION
-SPINAL MfilTAJKSH

FIG. 118. THE SITUATION OF HEADACHES
with reference to their causes.

THE NERVOUS SYSTEM 133

that they show us ways of living to be shunned in the
future. Many persons, however, not only derive no profit
from a headache, but by unwise efforts to cure the pain,
bring permanent injury to themselves in addition to the
suffering of the headache.

Bromides, opium, and other poisons deaden and weaken
the nervous system while preventing the headache from
being felt. HeadacJie powders, phenacetin, acetanelid, an-
tikamnia, and other vile poisons made from coal tar, shock
and weaken the heart and reduce the vital activities so
that the headache is no longer felt. In consequence of
shocks from repeated doses of such drugs, the heart will
not work so well, and may give way some time in the
future when an effort or strain makes unusual demands
upon it. Their use has made heart disease more preva-
lent. The liver and kidney cells and the white corpuscles
have to destroy and remove the drugs. Many people
are foolish enough to injure their bodies and risk death
rather than suffer pain or avoid pain by prudent living.

Sick headaches are foretold by a dull feeling, sleepiness
after eating, a coated tongue, and constipation. It would
be better to remove the undigested, spoiled food from the
stomach (four glasses of water will cause vomiting) than
to take a drug. At the first indication of trouble, ab-
stain from eating, or use a fruit diet for twenty-four
hours, and drink water freely. This will enable the
body to dispose of the excess of waste matter.

The Highest Living Medical Authority on Drugs. Dr.
Osier, formerly of Johns Hopkins University and now
of Oxford University, says :

" But the new school does not feel itself under obligation to give any
medicines whatever, while a generation ago not only could few phy-
sicians have held their practice unless they did, but few would have

134 HUMAN BIOLOGY

thought it safe or scientific. Of course there are still many cases where
the patient or the patient's friends must be humored by administering
medicine, or alleged medicine, where it is not really needed, and indeed
often where the buoyancy of mind, which is the real curative agent, can
only be created by making him wait hopefully for the expected action
of medicine ; and some physicians still cannot unlearn their old train-
ing. But the change is great. The modern treatment of disease
relies very greatly on the old so-called natural methods, diet and exer-
cise, bathing and massage, in other words giving the natural forces the
fullest scope by easy and thorough nutrition, increased flow of blood,
and removal of obstructions to the excretory systems or the circulation
in the tissues. One notable example is typhoid fever. At the outset of
the nineteenth century it was treated with " remedies 1 ' of the extremest
violence, bleeding and blistering, vomiting and purging, antimony and
calomel, and other heroic remedies. Now the patient is bathed and
nursed and carefully tended, but rarely given medicine. This is there-
suit partly of the remarkable experiments of the Paris and Vienna
schools into the action of drugs which have shaken the stoutest faiths ;
and partly of the constant and reproachful object lesson of homeopathy.
No regular physician would ever admit that the homeopathic " infini-
tesimals " could do any good as direct curative agents ; and yet it was
perfectly certain that homeopaths lost no more of their patients than
others. There was but one conclusion to draw, that most drugs had
no effect whatever on the diseases for which they were administered."
" Encyclopaedia Americana," Vol. X. (Munn & Co., New York.)

Applying Hygienic Tests Systematically. The cause of ill health
(e.g. a headache) should be sought with system and thoroughness, ap-
plying the tests in rotation to every function of the body : Lungs. Is
the air habitually breathed fresh and free from dust? Is the body held
up, and is the chest or waist cramped by clothing? Muscles. Is
enough physical exertion made to cause deep breaths to be drawn?
Food. Is it simple, digestible, and eaten properly? Drink. Is the
water pure? Cleanliness, Work and Rest, Clothing, Ventilation, and
Mental State may be inquired into until the source of trouble is found
and the cause of ill health removed. To give drugs and leave the cause of
ill health untouched, is to fail. There are signs of coming weakness or
illness which, if heeded and the ways of living improved, will usually
prevent illness. Among these signs are headaches, paleness, sensi-
tiveness to cold, heavy feeling or pain after meals, constipation. Huxley
says that young people should so learn physiology and so understand
their bodies that they will heed the first sign of nature^s displeasure,
and not wait for a box on the ear.

THE NERVOUS SYSTEM 135

Nervous Children. A report on the health of the school children in
one of our large cities shows that one third of the children in those schools
have some disorder of the nerves. Nervousness (weakened control of
the nerves) may show itself by sluggishness of mind, great irritability
of temper, frequent spells of the " bluest or by involuntary movements
of a jerky or fidgety kind. Sound development of city children's nerves
is hindered because of the constant noise in cities both day and night ;
by shortening of the hours of sleep ; by excessive use of sugar for food ;
by living much among people with no chance to be alone and let the
nerves rest, and among boys by the use of cigarettes.

How to Prevent the School from injuring Children. -
(i) Ventilation is of first importance. Breathing the
breath of fifty other children does far more harm than
overstudy. (2) The time devoted to work should not be
long, especially in the lower grades (no study out of
school). (3) The work sJiould be diversified; not only
printed words, but pictures, natural objects, and the out-
door world should be studied. (4) The teacher and parent
should see that the habitual poise of the child is favorable
to health. (5) The children should be encouraged to play.
Running games at recess are of the greatest value, and
are as indispensable to the health of a boy or girl as of a
colt. (6) Physical exercise should be provided at short
intervals between lessons, especially stretching exercises
and movements that straighten the spine and hips and ele-
vate the chest.

The Effect of Alcohol upon Nerve Function. - - In attack-
ing the nerve centers, alcohol begins with the cerebrum,
the highest, and proceeds toward the lowest. Hence as a
man becomes drunk he first talks foolishly (cerebrum
affected), then he staggers (cerebellum affected), and he
finally goes to sleep and breathes very hard (medulla
affected) in a drunken stupor. It rarely happens that the
breathing center is completely disabled and the man dies
from the strong poison. The greatest evil of alcohol is

136 HUMAN BIOLOGY

seen in the case of steady drinking. This gradually de-
troys the soundness of the nervous system and weakens
self-control. The tendency with nearly all drinkers is to
increase the amount taken.

Not Total Abstainers, but the Advocates of Universal
Moderation are the Visionaries. The evil results from
alcohol are so great as to be almost incredible. The
plainest statements of its effects are sometimes denounced
as unscientific by persons prejudiced in its favor. A part
of the two billion dollars annually paid for liquors is used
in influencing public opinion through the press.

PRACTICAL QUESTIONS.--!. Why does travel often cure a sick
person when all else fails ? 2. Why is working more healthful than
"taking exercise''? (p. 47.) 3. Is it better for children to play or to
take exercise ? 4. Why can one walk and carry on a conversation at
the same time ? (p. 127.) 5. How does indigestion cause a headache?
(P- I 33-) 6. Does perfectly comfortable clothing from head to foot
help to make one at ease in company ? Does uncomfortable clothing
tend to make one awkward ? 7. Why is it as important to have the
shoes and clothes perfectly comfortable when going out as when stay-
ing at home ? 8. When one's finger is cut, where is the pain ?
9. In what two ways may opening a window when a student is becom-
ing dull and drowsy at his books enable him to wake up and study with
ease? 10. What kinds of cells shrivel like a baked apple when they
become fatigued? (Fig. 117.) 11. A nerve or nerve fiber can hardly
become tired or fatigued, for the nerve cell supplies the energy. What
do we mean when we say the nerves are worn out? (Fig. 117.)
12. Why do you throw cold water upon a fainting person ? 13. Why does
constant, moderate drinking undermine the health more than occasional
intoxication? 14. Why does stoppage of the circulation cause one to
faint ? (See Chap. VI.) 15. Why is grazing the skin often more pain-
ful than cutting it ? (Colored Fig. I.) 16. Why do the lower ani-
mals always act upon sudden impulse ? What part of the brain enables
man to retain sensations and not act upon them until later ? 17. Does
" nervousness " more probably indicate a bright mind or a high temper ?

18. What is the effect of a cold bath upon the nerves ? (Chap. II.)

19. Did you ever know a cigarette smoker whose hand trembled ?

20. Need there be any fear of a sobbing child holding its breath until
it dies ? 21. Why is muscle tone greater in cold weather ?

THE NERVOUS SYSTEM 137

The True Function of Stimulants. - - One whose heart
has nearly given out because of exposure to severe weather
may be temporarily revived by alcohol. It will not be wise
to do so unless it is certain that a warm fire and protection
will be reached before tJie reaction comes. Much less would
be necessary to revive an abstainer than a drunkard. Ha-
bitually disturbing the body with stimulants makes them
ineffective in a time of emergency. A cup of coffee will
not keep a watcher awake if he is used to coffee.

Definitions : Stimulant, Narcotic, Poison. - - A stimulant
is anything that excites the body to activity, but is of no help
or of insignificant help, in replacing the strength used up.

A narcotic is anything that deadens or dulls the nervous
system. It comes from a word meaning " to benumb."

Poisons are active substances, which, taken in quantities,
as man takes food, destroy life ; in smaller quantities they
injure the body and may destroy life. Alcohol is a poison.
Wine, beer, whisky, contain varying quantities of it.

The Narcotic and Stimulant Effects of Poisons. Ex-
amples of poisons are alcohol, nicotin, opium, arsenic,
strychnin. Poisons excite the body when taken in small
doses, while in large doses they produce paralysis and
death. The irritating or stimulating effect is due to de-
rangement of the functions or to the efforts of the cells to
free the body of the destructive substance. The narcotic
effect is due to the poison having so benumbed the nerves
and injured the cells that their activities cease, or become
less for a time. You readily see how the same poison can
be both a stimulant and a narcotic : the stimulating effect
ahvays comes first, followed by the stupefying effect. If the
dose is very small, the stimulating effect will last longer ;
if it is large, the narcotic effect is greater and felt more
quickly. A habit of using stimulants is an invariable sign

138 HUMAN BIOLOGY

of weakness. The first dose of morphine or cocaine may
be the first step in a lifelong blight of strength and happi-
ness. If physicians whose treatment of a case results in
leaving a patient with a drug or alcohol habit were sued
for malpractice, they would be less reckless. The annual
consumption of morphine is estimated at twenty-seven
grains per capita in China, and fifty grains in the United
States.

Reaction.- This is tJie depressed and exhausted condition
that comes on after a period of unnatural activity. It fol-
lows the exciting effects of a stimulant.

Natural Stimulants. - - If there were nothing to arouse
activity, life would be impossible. A cold wind is a
natural stimulant. The activity aroused by a cold wind is
just enough to help the body withstand the cold ; artificial
stimulants cause an expenditure having no relation to the
needs of the body. Hence there is a great waste of energy.
Feelings may stimulate, as love for his family may stimu-
late a man to labor. The desire for knowledge may stimu-
late a boy to study. Hunger may stimulate a man to eat.
Hunger is a natural stimulant, and is not likely to make
him eat to excess ; tea, coffee, pepper, etc., arouse a false
appetite. These things are used chiefly for their stimu-
lant effect, for they contain little or no nourishment. We
will now study about artificial stimulants. Such stimulants
always cause an unregulated and unhealthy action, and are
always follo^cved by reaction,

How much Strength is stored in the Body? Dr. Tanner
of Minnesota believed that most people eat too much.
Another physician said that no human being could go forty
days without food. Dr. Tanner made the experiment.
He lost thirty-six pounds in weight, but he weighed 12 1 J
pounds and had considerable strength at the end of the

THE NERVOUS SYSTEM 139

forty days. The first thing he ate at the close of his fast
was the juice of a ripe watermelon.

Once some miners were shut in by the caving of a part
of a mine. But, unlike the case just described, they were
without water as well as food. When, by digging, the
rescuers reached them seven days after, several were still
found alive, although most of them had died. The miners,
no doubt, had nourishment in their bodies for some weeks
more of life, but the body lacked water to dissolve it and
bring it within the reach of the cells most needing it.

A Stupendous Fact.- These incidents show how wisely
the body is made, and prove that the cells store up nourish-
ment for weeks ahead. The large amount of nourishment
stored in the human body is one of the most striking and
important facts with which the science of physiology has
to deal, and it should be borne in mind, or we may make
great mistakes about some very simple matters and espe-
cially in regard to the effects of stimulants.

Foolisli Rashness. - - Did you ever get so tired that you
had to give up and stop, however much you would have
liked to continue at work or play ? To rest was tJie wise
tiling to do. Because you know there is much energy
stored in the body, this need not tempt you to go on
until you almost break down. Probably you know/^0//*?
who are conceited about their bodies and say they are "made
of cast iron " ; that nothing can hurt them. Such conceit
will be almost sure to get its possessor into trouble.

How a Safeguard may be broken down. - - It is a very
wise arrangement that, under ordinary conditions, we can-
not get at the surplus energy we have. Carbon dioxid and
other wastes accumulate in the tissues and paralyze the
nerves. Fatigue and other feelings compel us to be provi-
dent, as it were ; yet stimulants and narcotics, by irritating

140 HUMAN BIOLOGY

the nerve cells, arouse them and cause us to expend some
of this reserve energy. Thus man is enabled to get at
this precious store which he should save for emergencies,
when he is sick and cannot digest food, or when he is
making some mighty effort. A weak, ill man who has
eaten very little for weeks, when delirious is sometimes so
powerful that it takes several strong men to hold him in
bed. But the delirious mania often uses up the little
energy left, and costs the man his life.

The only source of energy for man's body is the union
of food and oxygen ; he must get his energy from the
same source that the engine does ; and this is from his
food, which serves as fuel, and the oxygen which burns it.
If one has been working hard preparing for examinations,
or gathering hay, or in attending to some important busi-
ness, or has been under the excitement of some pleasure
trip, and feels " blue ' and worn out, tJicn let Jiini bear tJie
result like a man, or like a true boy or girl, as the case
may be. Giving up for a while, or "toughing it out " with
the blues, or losing a little time from business, will not
hurt, but will restore strength, while a stimulant will
leave him less of a man than before.

Nervousness. The attempt to divide the race into brain workers,
muscle workers, and loafers, whether men or women, is a powerful factor
in race degeneration. Leonard Hill says : " Hysteria and nervous
exhaustion are the fruits not of overwork, but of lack of varied and
interesting employment. The absurd opinion that hard work is menial
and low, leads to most pernicious consequences. The girl who, turning
from brain work to manual labor, can cook, scrub, wash, and garden,
invites the bloom of health to her cheeks ; while the fine do-nothing
lady loses her good looks, suffers from the blues, and is a nuisance to
her friends and a misery to herself." A Japanese lady holds views
similar to those of Dr. Hill. Read footnote. 1

1 Statement by Madame Toyi Niku of Yeddo, Japan, after a six months'
visit to the United States. " Worry and inactivity, it seems to me, sharply

THE NERVOUS SYSTEM 141

SUBJECTS FOR DEBATE. - - (i) Does the Chinese woman deform her
body less than the Caucasian woman and suffer less from it ? (2) Does
as much disease originate in the dining room as the barroom ?
(3) Are drugs a necessary evil ? (4) Does pride cause as much illness
as ignorance ? (5) Is it ever right to neglect the health ? (6) Does
the mind or the way of living have more effect upon the health ?

Disuse and Degeneration. Many persons in civilized countries
cherish a vain hope of having sound muscles without habitual use of
them, pure blood without deep breathing, a strong circulation in an
inactive body, a fresh skin without keeping the body sound, a hearty
appetite without enough physical labor to use the food already eaten,
steady nerves with a part of the body overworked and a part stagnating
from disuse. Their flabby muscles, pale skins, highly seasoned food tc
arouse appetite, narcotics to deaden irritable nerves, and the wide use of
drugs as a fancied substitute for right living all show the attempt to be
a miserable failure. If the parents leading such a life escape with fairly
good health and average length of life, they leave a few unhealthy chil-
dren in whom physical degeneration is plain. Complete, balanced liv-
ing only prevents degeneration. Although there are cases of illness
which are not necessarily a disgrace, disease usually originates in weak-
ness of character or lack of common sense. The snob who thinks him-
self above physical labor, the dupes who at the bidding of avaricious
fashion mongers think more of clothes than of a free body, the narrow,
unbalanced man, who concentrates all his energies on one ambition, the
short-sighted one who worries, all grow into a diseased state.

mark the women of your middle classes. I did not attempt to study your
leaders of society, for they are much alike the world over-- the same fuss,
the same display of jewels and finery, the same scandals, the same uselessness.
Your women do not diversify enough. If they are good cooks, they stop
there; perhaps another is a good housekeeper, -another can sew finely; but
doing one thing makes narrow-mindedness. In Japan we strive to do many
things. The worry troubles of your women, it seems to me, come largely from
improper eating and overeating. I have sat at many of your tables and there
is too much food on them and too much variety. First, women overeat, then
they doctor, then they starve, and then they become nervous. A woman's diet,
especially a mother's, should always be simple. Cut down eating and increase
variety of labor and exercise. My own people live that way with a result that
we have better feminine bodies, better skins, and better tempers than your
women. I like the brightness of your young women. Perhaps you will take
the hideous hats off them some day, find a substitute for the bad corset, and
let them wear clothes that are loose, yet are soft and clinging. They are bound
up in their clothes too much now and their judgment of colors and combina-
tions is not good. Their clothing is either garish or very dull in hue. The
simplest girl in Japan knows how to harmonize color with herself. Mother^
Magazine, November, 1907.

CHAPTER IX

THE SENSES

Experiment I. Where are the Nerves of Touch most Abundant?
Open a pair of scissors so that the points are one eighth of an inch
apart, and touch both points to the tip of the finger. Are they felt as
one or as two points ? Find how far they must be separated to be felt
as two points when applied to the back of the neck. Record results.
Caution: The person should be blindfolded, or should look away while
the tests are being made. Two pins stuck in a cork will be more con-
venient to use than scissors.

Experiment 2. Nerves of Temperature, or Thermic Nerves. - - Draw
the end of a cold wire along the skin. Does the wire feel cold all the

time ? Repeat with a hot wire. Do
you conclude that temperature is felt
only in spots ?

Muscular Sense. --Experiment 3.
Make tests of the ability to distin-
guish the weight of objects weighing
nearly the same, when laid by another
in outstretched hand ; also by laying
them in the hand while it rests upon
a table. Which test showed more
delicate distinctions ? In which were
muscles brought into use ? Experi-
ment 4. Close the eyes and let some

one move your left arm to a new position ; then see if you can with the
forefinger of the right hand touch the forefinger of the left hand in its
new position at the first attempt.

Experiment 5. Functions of the Several Parts of the Tongue.
Test the tip, edges, and back of the tongue with sugar, vinegar, qui-
nine, and salt. Where is the taste of each most acute ? Record results.
Flavors. --Experiment 6. Blindfold a member of the class, and
while he holds his nostrils firmly closed by pinching them, have him
place successively upon his tongue a bit of potato and of onion. Can he
distinguish them ? Experiment 7. Mark Rafter each of the following

142

FIG. 119. "COLD" SPOTS (light
shading). " HOT" SPOTS (dark),
skin of thigh.

THE SENSES 143

foods that have a flavor (see text) : vanilla, apple, lemon, beef,
peaches, grapes, coffee, onion, potato, cinnamon.

Experiment 8. A Smelling Contest. - - Place the following and other
things having taste in vials around which paper has been pasted to con-
ceal their contents : pepper sauce, vinegar, kerosene, flavoring extracts
(diluted), several perfumes, iodine, bits of banana, lemon, apple, etc.
Number the vials and have pupils test and write results in a list.
Correct the lists and announce pupil having keenest sense of smell.

Experiment 9. A tasting contest may be arranged in a similar
way. Smelling and tasting tests should be made quickly as these
senses are soon dulled by repeating a sensation.

Experiment 10. Advantage of Two Eyes over One.- -Try to touch
forefinger to something held by another at arm's length from you,
bringing the finger in from the side: (i) with one eye closed;
(2) with both eyes open. Result ? Conclusion ? We tell the dis-
tance of an object by the amount of convergence of the eyeballs needed
to look at it.

Experiment u. Duration of Impression. - -Whirl a stick with a
glowing coal on one end (see Fig. 123).

Experiment 12. Color Blindness. - -Provide a number of yarns of
different tints, and the same tints. Test color blindness by having each
pupil match tints and assort the yarns.

Experiment 13. Fatigue of Optic Nerve. Gaze long and steadily at
a moderately bright object, then close the eyes. Result ? Conclusion ?

Experiment 14. Dissection of Eye.- -The eye of an ox is an in-
teresting subject for dissection. The lens is like a clear crystal. Make
out all parts named in the text (see Fig. 122).

Experiment 15. Image formed by a Convex Lens. --For a few
cents obtain from a jeweler a convex lens, or use a strong pair of
spectacles worn by an old person. Hold the lens a few feet from a
window (darken any other windows near). A little beyond the lens
hold a white card or book open at a blank page to catch the image.
Have some one walk before the window.

Experiment 16. Work of Iris. -- Notice the size of the pupils.
Cover one eye with the hand for a few minutes. Uncover and look in
a mirror. Gaze at bright window and look again in the mirror. Con-
clusion ? Do the two pupils still keep the same size w r hen one eye is
shaded ?

Experiment 17. Accommodation. -- By holding your finger or a
pencil in line with writing on the blackboard, you find that you cannot
see both finger and blackboard distinctly at the same time first one
and then the other is distinct. Explain (see text).

144 HUMAN BIOLOGY

Experiment 18. Astigmatism (effect of unequal curvature of cornea
or lens along certain lines). With end of crayon draw aboti't twelve
straight, even lines crossing at one point on the blackboard. Have
the lines of equal distinctness. How many pupils report that the lines
in certain directions are blurred? Inquire whether these pupils have
frequent headaches from eye strain.

Experiment 19. Can Sound reach the Ear through the Bones?
Hold a watch between the lips and notice its ticking. Close the teeth
down upon it and notice any change in the sound. Cover one, then
both ears, and note the result.

Experiment 20. Test keenness of hearing by having pupils walk
away from a ticking watch until it becomes inaudible. Test each
ear. A " stop " watch is preferable.

Experiment 21 . Advantage of Two Ears over One. - - Have the class
stand in a circle. Blindfold some one and place him in the middle of
the circle. Let various pupils clap the hands as the teacher points to
each. Can the blindfolded one point in the direction whence the sound
comes ? Stop one ear with a handkerchief and repeat. Result? Con-
clusion ? From what two points in the circle does the sound fall upon
both ears alike ?

Experiment 22. The Cause of Nasal Tones. - - Let a pupil go to the
back of the room and read a paragraph, and hold his nose until partly
through the reading. Or the teacher may read with his face and hand
hidden by a large book. Let the other 'pupils raise their hands when
they notice a change in the quality of the reader's voice. Does the
experiment show that a " nasal Vl tone comes partly through the nose
or through the mouth only? Does stoppage of the nostrils by catarrh
cause a nasal tone ?

Five Differences between Special and General Sensation. - - First, the
nerves of special sense all end in special organs at the surface ; for
instance, the touch corpuscles are for touch, the eye is for sight, etc.
There are many nerves in the body that do not end in special organs ;
these nerves give what is called general sensation. A second difference
is that general sensation tells of tJie condition of t lie interior of the body*
while special sensations tell us of the condition of the surface of the
body and of the outside world. Third, general sensations are not so
exact as the reports of the special senses. One can locate a point on
the skin that has been touched much more accurately than he can locate
an internal pain. A fourth difference is that the meaning of each special
sensation must be learned (usually in infancy) ; but the meaning of gen-
eral sensations is inherited. This inherited knowledge of what general
sensations mean is also called instinct. Fifth, the sympathetic nerves

THE SENSES 145

usually bring general sensations ; the spinal and cranial nerves usually
bring special sensations.

Examples of general sensations are hunger, thirst, satiety, nausea,
faintness, giddiness, fatigue, weight, aching, shuddering, restlessness,
blues, creepy feeling, tingling, sleepiness, pain, illness. Any nerve can
convey the general sensation of pain, if injured along its course. If a
nerve of touch is cut, there is no sensation of touch, but of pain. Touch
sensations come only from the ends of the nerves. General sensations
are of many kinds. We are only half conscious of some of them ; many
of them are hard even to describe.

Hygiene of the General Sensations. --General sensation is an invalu-
able aid to the health. Without it as a guide, the body could not
remain alive a single day. Pain should be heeded as our best friend,
and not killed with poisonous drugs as if it were our worst enemy.
We should not deaden the stomach ache with an after-dinner cigar.
If we do not go to bed when sleepy, the desire for sleep may leave us,
and we will undergo untold suffering from sleeplessness. Thirst should
be satisfied with cool water, which quenches it the best ; he who makes
his teeth ache with ice water will inflame his stomach and be continually
thirsty. He who does not stop eating when his hunger is satisfied, will
distend his stomach with food, and the stretched organ will be harder
to satisfy thereafter ; in fact, eating after a feeling of satiety may cause
indigestion so that the cells will not get the food. A dyspeptic is always
hungry, for the cells are starving. Fatigue of body or mind gives us
wise counsel ; but this feeling may be deadened by alcohol or tobacco,
and work continued until the body is injured. We should heed the
warning of pain or fatigue or restlessness as promptly as an engineer
heeds a red flag on the railway track. One who uses narcotics acts
like a reckless engineer who removes the danger signal and goes ahead,
hoping by good luck to escape an accident.

Most of the nerves of touch end in papillae of the dermis
as microscopic, cgg-sJiapcd bodies (Fig. 120). There are
also many in the interior of the mouth, especially on the
tongue. On the palms they are arranged in curved lines,
and on the tips of the fingers they are in circular lines,
with one papilla in the center. The delicacy of the sense
of touch varies very much in different parts of the skin.
This delicacy refers to two tilings : the ability to feel the
slightest pressure and the ability to tell the exact point of

146

HUMAN BIOLOGY

B

A, from cornea of the eye ; B, from the tongue of a
duck ; C, D, E, from the skin of the fingers. (Jegi.)

the skin that is touched. A lighter pressure can be felt
on the forehead and temples than with any part of the

body. (Why is it best
for this to be the
case ?) The greatest
delicacy in locating
the point of the skin
touched is found to be
located in the tip of
the tongue, the lips,
and the ends of the
fingers (Exp. i).
(Why is it best that

this is so ?) This deli-
FIG. 120. DIFFERENT KINDS OF TOUCH

BODIES AT ENDS OF NERVES. cacy is least in the

middle of the back.
The delicacy varies
with the number of touch corpuscles in different parts
of the skin. The sense of touch is capable of great
cultivation, as in the case of the blind.

The temperature sense is given by special nerves called the thermic
nerves (Exp. 2). That the thermic nerves are easily fatigued is noticed
soon after entering a bath of hot water ; it is also shown by the fact
that in cold countries the nose or ears of a person may freeze without
his feeling it.

The Muscular Sense. - - The special sense of touch gives some sense of
weight. A weight upon the skin must be increased by one third before
it feels heavier, but by lifting an object so as to bring into action tlic
muscular sense residing in nerves ending in the muscles an increase of
only one seventeenth of the original weight can be noticed (Exp. 3).
This sense gives us a continual account of the position of the limbs
(Exp. 4).

The end organs of taste are located in the papillae of
the tongue. The tongue has a fuzzy look because of the
numerous papillae.

THE SENSES 147

The principal tastes are only four ; namely, sweet (tasted
chiefly by tip of tongue), sour and saline (sides of tongue),
bitter (tasted on the back of tongue) (Exp. 5).

The nerves of smell end in the mucous membrane of the
upper half of the two nasal chambers ; the fibers are spread
over the upper proportion of the walls. The direct current
of air does not pass as high as these nerve endings ; hence
sniffing aids the perception of odors. This sense is able
to bring up the associations of early life more powerfully
than any of the senses. The odor of a flower like one
that grew in an old garden can almost restore the con-
sciousness of the past. We swell gases only ; solids and
liquids cannot affect this pair of nerves (Exp. 8).

Flavors. - The tastes that we call flavors are really
smells. We confuse them with taste, because they accom-
pany food that is in the mouth. Name some foods that
seem " tasteless" when one has a severe cold in the head.
Why is this ? Some of the most repulsive drugs can be
easily swallowed if the nose is held (Exp. 6 and 7).

Hygiene of the Senses of Taste and Smell. -- A savage or a beast
uses the senses of taste and smell to find out whether things are good
to eat or not. If a civilized man's senses are not perverted, and he eats
only simple foods that have a pleasant taste, they will not injure him or
cause him sickness. Things that are poisonous usually have unpleasant
tastes and often have unpleasant odors. These senses are naturally
of wonderful delicacy. They can be cultivated to a still more remark-
able degree, or they can be blunted and almost destroyed. Chronic
catarrh dulls or destroys the sense of smell. The loss or even the
weakening of the perception of flavors is an injury to the working of
the closely related sense of taste. When a person loses the enjoyment
of delicate flavors, he wants food to have strong seasoning and more
decided taste to prevent it from being insipid. Everything must be
either very greasy or very sweet or very salty or very sour, to please his
degenerate senses. Wheat, corn, and other grains have each its own
pleasant taste, yet such persons must have lard in their bread because
they are not capable of appreciating anything with a delicate taste. In

148 HUMAN BIOLOGY

England, butter is not salted and its delicate taste is enjoyed ; in
America, salt is added to preserve it, and most people have come to
prefer the strong taste of salty butter to the delicate taste of pure butter,
and do not like it unless its true taste is partly hidden by the taste of
salt (Exp. 9).

Deceiving the Sense of Taste. - - The habit of using narcotics like
tea and coffee is usually begun by concealing the repulsive bitter taste
of the substance by mixing sugar, cream, and other agreeable things
with it. Licorice is sometimes mixed with tobacco to weaken its biting
taste. Pure alcohol would never be drunk by any one who had the
least respect for the sense of taste, but the agreeable flavor of grapes,
apples, and other fruit which still remains in wine, cider, and brandy,
conceals the repulsive taste of the alcohol. Beer has the insipid taste
of grain which has undergone decomposition or partial rotting, and
hops are added because the strong bitter taste of hops is needed to
hide the stale, rancid taste of the rotted grain. Eggnog is made of
eggs, a nourishing food ; sugar, which has an agreeable taste ; water, a
refreshing drink, and alcohol, a fiery poison. A very good eggnog is
often made without alcohol, but a good one could hardly be made with
any of the pleasant ingredients left out. The best eggnog is made by
using the fresh juice of lemon, orange, or grape, instead of alcohol.

Effect of Narcotics. Tobacco, alcohol, opium, and other narcotics
dull the senses of taste and smell and prevent the enjoyment of delicate
flavors. They accomplish this as much by their effect upon the brain
as upon the nerves themselves.

It is Wrong to eat Food that is not Relished. - - Unpalatable food is
not likely to be well digested. It is a law of the body that the food
li'/iich is enjoyed the most is digested tJie best. This applies to a hungry
person eating food with its own honest taste, not to food disguised by
the taste of something else. The rule does not apply to a taste per-
verted by having been forced to become accustomed to poisonous
things. People who munch their food slowly enjoy the pleasures of
taste the most, and digest their food the best. The nerves of taste
and smell easily become fatigued. The first whiff from a cologne bottle
is the strongest. Highly flavored foods should be eaten moderately,
if we would obtain the greatest enjoyment from them.

THOUGHT QUESTIONS. 1. Interfering with the Body. What is
the natural direction of growth of the big toe? 2. Think of six evil
results, direct or indirect, which will follow from displacing it by tight
shoes (p. 48). 3. Which part of the spinal column, designed in
infinite wisdom to be most flexible, do some people try to make the
most inflexible? 4. The mobility of the false and floating ribs was

THE SENSES

149

A pressure upon the eye-

intended as a blessing. Some people interpret the blessing as an
opportunity to do what ? 5. Name six articles which warn us to avoid
them by their bitter, burning, or nauseating tastes, yet which are used
by man. 6. Name six feelings which are intended as warnings for our
guidance, but which are commonly disregarded.

The eyes on the rays of the starfish are mere spots of
pigment. Insects have lenses in their eyes. The eyes of
vertebrates are all formed on the same general plan as the
human eye.

The eyeballs are globes about an inch in diameter.
They are placed in deep, bony sockets, called orbits, in
the front part of the skull. The optic nerve, other nerves,
and several large blood vessels pass to the eye through a
hole in the back of the orbit. A soft cushion of fat is in
the orbit behind the eyeball,
ball causes the eye to sink
into the socket, for the fat
yields to the pressure.
This is a protection to the
eye.

The eyelids protect the
eyes from dust, and at
times from the light. They
are aided in this by the
eyelashes.

The tears are formed by tear glands situated above the
eyeball in the portion of the orbit farthest from the nose,
just beneath the bony brow where it feels the sharpest
(Fig. 12 1). They are about the size of almonds. A salt-
ish liquid is continually oozing from the tear glands and
passing over the eyeball ; it is carried into the nose
through the nasal duct (Fig. 121). The tears reach this
duct through two small canals, which open into the eye
in the little fleshy elevation at the inner corners of the

Ducts

Fie. 12;. --TEAR GLANDS AND
DUCTS of right eye. (Jegi.)

ISO

HUMAN BIOLOGY

eye (Fig. 121). The opening of one of the canals may
be seen by looking into a mirror. Sometimes these canals
are stopped up, and what is called a " weeping eye '
results. A temporary stoppage may occur during a cold
in the head.

Tears prevent friction between eye and lid. Winking
applies the tears to the ball. Small glands along the
edges of the lids form a kind of oil which usually prevents
the tears from flowing over the lids. Sometimes this oily
secretion is so abundant, especially during sleep, as to
cause the lids to stick together. The mucous membrane

of the eyelids
continues as a
transparent
membrane (the
c o n j un c t iva)
which passes
over the front of
the ball.

The globe of
the eye consists
of its outer wall
and the soft con-
tents (Fig. 122).
The wall has three layers or coats. The outer coat is the
tough sclerotic (Greek, skleros, hard), composed of dense
connective tissue (Exp. 14). It gives strength and firm-
ness to the eyeball. It shows between the lids as the
''white of the eye." It is white and opaque except in
front; there it bulges out to form the transparent cornea.
This clear portion of the wall may be seen by looking at
the eye of another from the side.

The second coat, called the cJwroid, consists of blood

VITREOUS HUMOR

Iri

''Retina
Chore id
Vclerotic coat

FIG. 122. THE ANATOMY OF THE EYE.

THE SENSES

vessels and a loose connective tissue containing many
dark brown or black pigment granules. The choroid
absorbs superfluous light. Cats' eyes shine at night
because this coat in their eyes reflects some light. The
choroid separates from the sclerotic toward the front of
the eye and forms the colored ins. The iris makes the
eyes beautiful, and it also serves the useful purpose of
regulating the amount of light. The hole in the iris is
called the /;//// (Exp. 15).

The third and innermost coat, the sensitive pinkish layer
called the rcfin-a, is the most important and characteristic
tissue in the eye. It re-
ceives the light rays, and
retains the image for a
fraction of a second (Exp.
n). Hence the pictures
in a kinetoscope (Fig. 123)
appear as one moving pic-
ture. The retina is made
chiefly of the fibers of the
optic nerve. This nerve
contains about five hundred
thousand fibers, and enters
at the back of the ball.
The spot where it enters

contains no nerve endings

FIG. 123. STROBOSCOPE, the original of
the kinetoscope. The observer looks
through the slits of a rapidly revolving
disk and a new image falls on the retina
before the last image has faded. Com-
pare the pictures in the figure.

and is not sensitive to

light. It is called the

blind spot. The spot where the light most often falls is

most sensitive to light. It is the yellow spot (Fig. 122).

Test for the Blind Spot.- -In this experiment shut
the right eye and be careful not to let the left eye
waver.

152 HUMAN BIOLOGY

^ Read this line slowly. Can you see the star all the
time ? (If so, hold the book farther or closer and repeat.)
Within the coats of the ball, like the pulp within the
rind of an orange, are the soft contents, divided into three
parts. The first is a watery liquid in front, which serves
to keep the cornea bulged out (Fig. 122). It is called the
a'qne-oiis humor. The main cavity of the ball is occupied
by a clear, jelly like substance called the vit^re-ous hninor,
which serves to keep the ball distended. Back of the iris,
and separating the two humors just named, is the crystal-
line leus, a beautiful clear lens, convex or rounded out on
both sides (Exp. 14). It serves to bring the light to a
focus on the retina, thereby forming images of outside
objects.

The eye, like a camera, has a dark lining, the choroid;
the retina corresponds to the sensitive plate, and the lens
brings the rays to a focus on it and forms the image.

The Path of Light in the Eye. The light enters through
the transparent cornea and passes through the aqueous

humor. As it goes through
the pupil, the iris shuts off all
the light that is not needed.
The crystalline lens receives
the light that has been al-
lowed to pass, and so bends
the rays that by the time they
FIG. 124. CROSSING OF OPTIC have passed through the vit-

NERVES showing that one nerve ^^ ^^ th ^ R

reaches same half of both eyes.

the retina in just the right

way to form a tiny image of anything outside (Exp. 11).
The choroid absorbs any light that passes the retina.
The iris and choroid of albinos have no pigment; hence
albinos squint their eyes to shut out some of the light.

THE SENSES

153

FlG. 125. Change of lens in accom-
modation. (Jegi.)

Accommodation. - - In order to focus the light upon the
retina, the lens must change shape for every change in the
distance of the object looked
tf/(see Fig. 125). The shape
of the lens can be readily
changed, for it is elastic and
has muscular fibers around
its edges (Exp. 17).

Defects in the Eye.- -Some
eyeballs are too long, and the lens brings the rays to a
focus before they reach the retina. Such eyes are near-
sighted (Fig. 126) and require
glasses that round inward (con-
cave). Some eyeballs are too
flat, and the rays are not brought
to a focus soon enough. Such
eyes are farsighted and require
glasses that round outward
(convex). See Fig. 127. (Re-
peat Exp. 15.)

Care of the Eyes. - - Because
the eyes can do a large amount
of work without giving pain,
they are often abused. When
reading or doing intricate work, turn the eyes from the

work occasionally and look
at some distant object ; stop
work before the eyes are
tired. Twilight of early
evening has ruined many

good eyes. You should
FIG. 127. --FARSIGHTED EYE (ball a] g st work before

too short) which needs convex lens

to focus rays upon retina. the twilight begins, for the

FIG. 126. -- (i) NEARSIGHTED
EYE (ball too long), which only
focuses rays for near objects
(2) when concave glasses are
used (3).

154 HUMAN BIOLOGY

light fades so gradually that you will surely be straining
the eyes before you know it. Do not work with the light
in front ; the glare of the light makes objects appear dim.
The light should come from above, and (for right-handed
people) from the left. Do not read papers or books
printed in fine type. We should not read when convales-
cing from illness ; with the head bent down ; when the
eyes are sore ; in jolting cars. Heating the eyes by a
burner, or drying the eyeballs in a dry, stove-heated at-
mosphere, using a light without a shade, cause trouble
with students' eyes. Of what are blood-shot eyes often a
sign? Our eyes are best suited for seeing at a distance
because primitive man had no houses, books, sewed
clothes. Effort is required to shape the lens for seeing
near objects. Most cases of nearsightedne3s begin when
children are taught to read under eight years old. The
eyes are sometimes injured by the use of tobacco.

THOUGHT QUESTIONS. The Eye. --1. The eye is shielded from
blows by bony projections of , - , and - -. 2. The hairs of
the eyebrows lie inclined toward - , in order to turn - from the
. 3. I find by trying it that I (can or cannot?) see the position
of a window with my eyes closed. 4. The pupil appears to be black,
because no - is - - from the interior wall of the eye. I know that
the iris is partly muscle, because it - the size of the .

Sound. --Anything that is sending off sound does so by
or shaking to and fro, very rapidly. For instance, a vibrating violin
string sets every particle of air near it swinging to and fro. The near-
est particles of air strike the next ones and bounce back, these in turn
strike against others, and thus vibrations called sound waves are sent
through space in all directions from the sounding body. We feel these
waves with the ear.

The ear consists of three portions : the external ear, the
middle ear (or drum), and the internal ear (or lauyrinth,
see Fig. 128). The cranial nerve connecting the ear with
the brain is called the auditory nerve. The outer and

THE SENSES

155

middle ear pass on the vibrations of air to the ends of the
fibers of the auditory nerve in the internal ear.

The external ear consists of a large wrinkled cartilage
on the exterior of the head and a canal leading from it,
called the meatus. This passage is closed at its inner end
by the drum membrane or drum skin. It is often called
the drum, but this name is properly applied to the whole
middle ear. A trial will show that the drum skin cannot

The Hammer
(Malleus).

Moatus

The Drum

of the Ear

(Tympanic

Membrane}.

The . Loops
(jStmirirctilar

The

Shell Tube
[Cochlea).

The Anvi]
(Incus).

The Stirrup
(Stapes).

Eustachian Tube

FIG. 128. MIDDLE AND INTERNAL EAR (greatly enlarged).

be seer even with the aid of a bright light, for the passage
is siifciiJy curved (see Fig. 128). Hence a missile or a
flying insect cannot go straight against the ear drum. The
skin lining this passage contains wax glands > which secrete
a bitter sticky wax, which helps to keep the passage flex-
ible. This wax catches dust and usually stops insects that
may enter. If an insect enters the ear, it may often be
coaxed. out by a bright light held close to the ear. The
ear wax in a healthy ear dries with dust and scales of epi-
dermis and falls out in flakes, thus cleansing the ear. It

156 HUMAN BIOLOGY

is unwise to probe into the ear with a hard object or even
with the corner of a towel. It is not necessary to insert
the finger in the meatus to cleanse it ; it is one inch long,
but only about one fourth inch across. (How large is the
little finger ?) The cartilaginous ears on the sides of the
head should be carefully washed because of their many
crevices. If ear wax is deposited too fast, it will cause
temporary deafness and earache. It may be syringed out
with warm water. Earache is usually caused by a small
boil which requires time to relieve itself by bursting.
Warm water poured into the upturned ear, or hot flannels
or compresses applied to the side of the head will lessen
the suffering. Each ear has three muscles for moving it.
Once they were doubtless useful to all, but like the scalp
muscle they have become so weakened by disuse as to be
useless to most people. They are vestigial organs.

The middle ear, or drum chamber, contains air (Fig.
128). It is separated from the outer ear by the drum
membrane. It contains three bones which stretch across
it and conduct the sound waves from the drum membrane
to the inner ear. State the order in which they are
placed (see Fig. 128). The middle ear is connected with
the pharynx by a tube (the Eustachian tube ; pronounced
yoo-stake'e-an, see Fig. 128). This tube is opened every
time we swallow. It allows the air from the throat to
enter the middle ear and keep the air pressure equal on
each side of the drum skin. This tube and the middle
ear are lined with mucous membrane.

A cold in the head or a sore throat may extend through
this tube to the middle ear and affect the hearing. This
occurs because the tube is closed by congestion of its lin-
ing; the air of the middle ear may be partly absorbed,
and the pressure of the outside air may cause the drum

THE SENSES 157

membrane to bulge inward, and to be stretched so tight
that it cannot vibrate freely.

The inner ear is called the labyrinth^ because of its wind-
ing passages. There is a spiral passage called the snail
shell 23\& three simpler passages called the loops (Fig. 128).
The inner ear is filled with a limpid liquid which conveys
the vibrations to the ends of the auditory newe found in the
snail shell. If the auditory nerve or labyrinth becomes
diseased, the deafness is probably incurable. Quinine and
other drugs may cause deafness.

Sense of Equilibrium. -- Some fibers of the auditory nerve end in the
loops and are not believed to be used in hearing. It is believed that
each loop acts like a carpenter's level, and the varying pressure of the
fluid upon the nerves in the loops tells us the position of the body and
constitutes the sense of equilibrium. There are how many of these
loops in each ear ? (Fig. 128.)

CHAPTER X

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BACTERIA AND SANITATION

Experiment I. Yeast Plants. With a microscope examine a drop
from a glass of water in which you have washed grapes or apples
(Fig. 129).

Experiment 2. Fermentation. Put a tablespoonful of sugar into
this water and set the glass in a warm place for a day or two. Do

you see any bubbles of gas ?
Have the odor and taste
changed ? Does the micro-
scope show that the yeast
plants are now more abun-
dant ? By fermentation, or
the growth of yeast in sugar,
sugar is changed into carbon
dioxid, a gas, and alcohol, a
liquid.

Experiment 3. A Sani-
tary Map. Construct a
sanitary map of the com-
munity. Indicate houses
where consumption, typhoid
fever, or other transmissible
diseases have occurred, with
number of cases. Mark loca-
tion of stagnant waters where
mosquitoes breed, mark

garbage dumps, unclean streets. Suggest where improvements may
be made in drainage, dust, noises, sunshine, shade, etc.

Bacteria, or microbes, the smallest living things, are
visible only under a microscope of high power. (See
"Plant Biology," p. 182.) They obtain food either from
dead tissue or from degenerate tissue of living plants, and

158

FIG. 129. YEAST CELLS magnified 200
diameters, or 40,000 areas). Yeast plants
multiply by budding. Notice small cells
growing on larger and older ones.

BACTERIA AND SANITATION 159

animals. The green plants and the animals now upon the
earth have proved their fitness to survive by successfully
resisting these one-celled vegetable germs, or bacteria.
Microbe diseases attack only the weaker individuals of the
human species, or those who have gone to regions where
there are microbes which their bodies have not yet ac-
quired the power of resisting.

Usefulness of Bacteria. Their chief work is to destroy
dead tissue and return it to the soil and air for the use of
green plants again, otherwise the earth would be filled
with carcasses, etc. They are indispensable in soil forma-
tion. They give the agreeable flavors to butter and cheese,
and cause milk to sour. A rod-shaped bacterium is called
a bacillus (Fig. 130); a spherical one is a coccus.

Multiplication of Bacteria. - This is by division or fis-
sion. Sometimes, instead of dividing, a little rounded mass
known as a spore appears. The spore breaks out and the
bacterium itself perishes. Species which do not produce
spores are readily destroyed, but spores have a hard, tough
shell, and they may be dried or heated even to boiling with-
out being killed. Spores float through the air a*nd start
new colonies. Most common bacteria grow best between 70
and 95 F. They render it difficult to preserve foods, espe-
cially proteid foods (cheese, lean meat, eggs, etc.). Food
decays slowly if at all below 70 and above 125. Direct
sunlight, or the temperature of boiling water (212 F.)
kills bacteria but not spores. Pantries, kitchen, and sick-
rooms should have bright walls and all the light possible.
Boiling water should be poured into the sink, and dish
cloths should be thoroughly washed in boiling water.

Diseases due to Bacteria. A germ disease is usually due
partly or wholly to substances called toxins produced by
the bacteria. Most disease germs attack a single organ

160 HUMAN BIOLOGY

of the body. Diphtheria is caused by a species (Fig. 130)
that grows on the mucous membrane of the throat ; this

germ produces a powerful toxin. The
germs of typhoid fever (Fig. 131) and
Asiatic cholera multiply in the small
intestine. In both these diseases the
source of infection is the diarrhoeal dis-

FIG. 130. BACILLUS charges from the alimentary canal. Flies
OF DIPHTHERIA. . .

may carry the germs on their feet from

the discharge to food. Sometimes typhoid fever cases occur
throughout a town because the water supply has become
contaminated by sewage. Cases may
occur only in families that buy milk
from a certain dairy, because the
milk cans have been washed in con-
taminated water. Jn caring for a ty-
phoid patient all suspicious material
should be disinfected or burned. "'**- ^*^ ^

Germs of tuberculosis (called con- FIG. 131.- BACILLUS OF

TYPHOID FEVER.
sumption if the disease is in the

lungs) may float through the air. Recent investigations
indicate, however, that infection usually occurs through
the alimentary canal, the germs being swallowed, then
absorbed and taken to the lungs in the blood or lymph.
To prevent a patient from reinfecting himself in new
parts of the lungs or elsewhere, he should carefully
cleanse his teeth, mouth, and throat (by gargling with
formal or lysol) before eating.

Mosquito Fevers. Malaria, yellow fever, and probably
dengue are transmitted each by a different genus of
mosquito (Fig. 132). A mosquito of the malarial genus
may bite a patient and suck into its body blood-corpuscles
containing spores of the malarial parasite (a protozoan

BACTERIA AND SANITATION

161

animal, see "Animal Biology," p. 7). Afterwards a spore
(in another stage) may be transmitted by this mosquito
when it bites another person. The
germ enters a red corpuscle, grows,
and finally divides into many little
spores. At this moment the cor-
puscle itself breaks up, setting
free in the blood the spores and
toxin formed. This causes the
chill and fever. This develop-
ment usually takes forty-eight
hours, hence the fever occurs
every other day. These mos-
quitoes begin to fly at dusk. How
are they recognized? (Fig. 132.)
They should be kept out of houses FIG. 132. CULEX OR COM-

, , , , MON MOSQUITO, above (pos-

by screens or from the, beds by sibly carries dengue fever)-
netting. Kerosene should be
poured on breeding places at the
rate of one ounce for fifteen square
feet of standing water. This
should be repeated twice a month.

Cactus macer-

ANOPHELES OR MALARIAL

MOSQUITO, below (not always
infected). Body of malarial
mosquito is never held paral-
lel to the supporting surface
(unless a leg is missing) ; it
has five long appendages to
the head, the culex (above)
has only three. (Draw.)

ated in water

may be used, and forms a permanent

film on the water. Stagnant pools

may be filled or drained (Exp. 4).
FIG. 133. PROTECTIVE . 777 j

WHITE CORPUSCLE Malarial patients should themselves oe

(phagocyte) digesting screened, as the chief source of danger to

a microbe.

others ; tor only mosquitoes who suck
the blood of malarial patients will transmit the disease.
Even then it is only transmitted to those whose white
blood corpuscles are unable to protect them (Fig. 133).

l62

HUMAN BIOLOGY

Further Means of Protection against Disease Germs.

The best protection is physical vigor. There are certain
substances called opsonins which exist in the plasma of the
blood of disease-resisting persons ; these opsonins give the
white corpuscles the power to devour disease germs. The
serum of the blood also develops antitoxins which neutral-
ize the toxins formed in disease. Not only can the white
corpuscles and serum kill bacteria, but most of the secre-
tions of the healthy body (gastric juice, nasal secretions,
etc.) are bacteria-killing as well. Persons in a low state
of health most readily succumb to disease. Excess in eat-
ing may lessen the germicidal power of gastric juice and
inactivity that of the lymph. The same germ disease
does not usually attack the same person twice, as the
body becomes immune; that is, an opsonin, or an anti-
toxin, is developed which cures the first attack and remains
to protect the body in future.

The periods of quarantine or isolation for several com-
mon germ diseases are given in the following table :

FROM EXPOSURE

NAME OF

TILL FIRST

PATIENT is INFECTIOUS

DISEASE

SYMPTOMS

TO OTHERS

Diphtheria

2 days

14 days after membrane disappears.

Mumps

10-22 days

14 days from commencement.

Scarlet fever

4 days

Until all scaling has ceased.

Smallpox

12-17 days

Until all scabs have fallen.

Measles

14 days

3 days before eruption till scaling

and cough cease.

Typhoid fever

ii days

Until diarrhoea ceases.

Whooping cough

14 days

3 weeks before until 3 weeks after

beginning to whoop.

Water Supply. - - Bacteria are more abundant in flowing
streams than in water standing in lakes or reservoirs (con-

BACTERIA AND SANITATION 163

trary to the usual belief). They are most abundant in
rivers that flow through populous regions. They are com-
paratively scarce in dry, sandy soils, and very numerous in
moist, loamy soils. The water of cities should never be
taken from a stream or lake into which sewerage flows
unless it is thoroughly filtered. Filters are constructed
thus : first a layer of small stones, next a layer of coarse
sand, lastly a layer of very fine sand on top, the total thick-
ness being four or five feet. Beneficial microbes live upon
the grains of sand and destroy all, or nearly all, of the
dangerous microbes as the water slowly soaks through.

The construction of such waterworks is left to sanitary
engineers, of course, and the average citizen does not need
to know the details.

The department of street cleaning should receive the
willing cooperation of all citizens. Banana peelings, paper,
etc., should not be thrown upon the street or school
grounds. Garbage, ashes, and rubbish should be placed in
separate cans, as the rules provide. Garbage cans, if not
thoroughly cleaned, acquire unpleasant odors and breed
flies and bacteria. They should be thoroughly washed
with very hot water and sal soda and scalded with boiling
water and scrubbed with an old broom. 1

The chief duties of the Health Department are: quar-
antine isolation and disinfection, with the purpose of pre-
venting or controlling contagious and infectious diseases ;

1 The chief Disinfectants are : fresh air, sunshine, heat, formaldehyde, etc.
Airing and sunning will destroy some germs in bedding and clothing as effec-
tually as chemicals. Boiling and steaming are the best ways of applying heat.
Formaldehyde is a volatile liquid. After room is sealed and strips of paper
pasted all over cracks, a specially constructed generator is applied to keyhole,
and room kept closed for 12 hours. Alercuric chloride (corrosive sublimate)
is used I part to 1000 parts of water for disinfecting soiled clothing, towels,
utensils, surgeon's instruments, and wounds. In place of this, carbolic acid,
5 per cent solution, may be used, but it is not so good a germicide.

1 64 HUMAN BIOLOGY

inspection of dairies, slaughterhouses, and other sanitary
work; inspection of milk 1 and other food stuffs; the de-
partment gathers vital statistics ; it enforces the rules for
disinfection of public buildings.

Importance of Cooperation with the Health Department.
Only an ignorant and short-sighted person' would fail to
cooperate promptly and cheerfully with local or state
health officers. It is for the benefit and protection of
every one that the truth concerning contagious diseases
be reported promptly. Only in this way may outbreaks
of disease be prevented and many lives saved. He is a
bad citizen and a public enemy who will conceal a case of
disease dangerous to the community. Outbreaks of fatal
diseases may be easily prevented or stamped out if the
health officer is sustained and his directions carried out.

1 Milk may be sterilized by boiling, but boiled milk is not digestible nor
nutritious. Milk may be Pasteurized by immersing bottles of milk in water
which is kept nearly (but not quite) at boiling point (160 F.) for five min-
utes. But this makes the milk less valuable than fresh milk, and destroys
beneficent microbes. Buttermilk has many such microbes, which kill injurious
microbes and purify the stomach. Cleanliness, or an aseptic condition, is far
preferable to antiseptics.

LESSONS IN HYGIENIC PHYSIOLOGY

By W. M. COLEMAN. x+2yi pages. 198 illustrations (16 colored,

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In Lessons in Hygienic Physiology the study of physiology
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The subjects treated are four in number : the nature of the
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The book is based upon the idea that the proper way to
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