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Full text of "Animal biology; Human biology. Parts II & III of First course in biology"

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ANIMAL BIOLOGY 
HUMAN BIOLOGY 



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THE MACMILLAN COMPANY 

NEW YORK BOSTON CHICAGO 
ATLANTA SAN FRANCISCO 

MACMILLAN & CO., LIMITED 

LONDON BOMBAY CALCUTTA 
MELBOURNE 

THE MACMILLAN CO. OF CANADA, LTD. 

TORONTO 




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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 



i rs 

^ ^$^f,r^'- |J IF 







^$B^VN** T : 

: ' :^^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 







rfm ' 

* '$* , E 
..'&& 

^3 


1:^ 

f^-' 


- " ' V^^ ; >. 


,- 




Uro^; 




Vj *X: 
- TVV 



:*?/ 



CD 1 



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, 

13 full-page plates). 60 cents net. 

In Lessons in Hygienic Physiology the study of physiology 
is simplified without weakening the presentation of its three 
essential principles - - the biological principle of environment, 
the chemical principle of oxidation, and the physical principle 
of energy. The subject is approached throughout from the 
standpoint of health, because this is the most useful as well as 
the most interesting point of view. The question of temper- 
ance is treated fully, but at the same time in a conservative 
manner. The book is fully illustrated, one hundred and ninety- 
eight figures being furnished, sixteen of which are colored. 
The Lessons is suited to the needs of teachers who may find 
the Elements somewhat too advanced for their classes. 



ELEMENTS OF PHYSIOLOGY 

By W. M. COLEMAN. xii + 364 pages. A very full course in Physiology 
and Hygiene. Profusely illustrated in black and white and in 
colors. 90 cents net. 

This book has an exceptionally large number of illustrations 
two hundred and forty-eight, of which eight are full-page 
colored plates. The need for a compound microscope is 
largely obviated by sixty microscopic views of cells and tissues. 
The Elements is provided with a Colored Manikin arranged to 
show every important organ in its natural position with refer- 
ence to the organs before it, behind it, and around it. Since 
every pupil has the manikin while studying each lesson, it is 
really more serviceable than the manikins usually found in 
schools. This book contains twenty-five Thought Lessons 
of about ten questions each, logically developing different 
lines of thought ; also three hundred questions in Applied 
Physiology. 



THE MACMILLAN COMPANY 

Sixty-four and Sixty- six Fifth Avenue, New York 



BOTANY 

An Elementary Text for Schools. By L. II. BAILEY, Director of the Col- 
lege of Agriculture, and Professor of Rural Economy in Cornell 
University. Revised and enlarged. Illustrated. I2mo. Half 
leather, xiv + 355 pages. $1.10 net. 

The subjects treated are four in number : the nature of the 
plant itself, the relation of the plant to its surroundings, the 
minute structures of plants, and the determination of the kinds 
of plants. Each of these subjects is practically distinct, so that 
the teacher may begin where he will. 

Theyfe? hundred illustrations in the book are an important 
as well as an attractive feature. They are not pictures merely 
they are illustrations of the subject-matter; many of them 
are reproductions of photographs. 

A flora containing descriptions of more than six hundred 
common wild and cultivated plants, with keys to the natural 
orders, completes the book. 



LESSONS WITH PLANTS 

Suggestions for Seeing and Interpreting Some of the Common Forms of 
Vegetation. By Professor L. H. BAILEY. Illustrated. 121110. 
Half leather, xxxi + 491 pages. $1.10 net. 

The book is based upon the idea that the proper way to 
begin the study of plants is by means of plants, instead of 
formal ideas or definitions. Instead of a definition as a model 
telling the pupil what he is to see, the plant shows him what 
there is to be seen, and the definition follows. In this way the 
pupil soon begins to generalize, and the conclusion reached is 
the true definition. 



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