Full text of "A civic biology : presented in problems"

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Compare the unfavorable artificial environment of a crowded city with the more
favorable environment of the country.

A CIVIC BIOLOGY

Presented in Problems

GEORGE WILLIAM HUNTER, A.M.

HEAD OF THE DEPARTMENT OF BIOLOGY, DE WITT CLINTON

HIGH SCHOOL, CITY OF NEW YORK.
AUTHOR OF "ELEMENTS OF BIOLOGY," "ESSENTIALS OF

BIOLOGY," ETC.

AMERICAN BOOK COMPANY

NEW YORK CINCINNATI CHICAGO

HUNTER, CIVIC BIOLOGY.
W. P. 3

TO MY

FELLOW TEACHERS

OF THE DEPARTMENT OF BIOLOGY 4

IN THE DE WITT CLINTON HIGH SCHOOL

WHOSE CAPABLE, EARNEST, UNSELFISH

AND INSPIRING AID HAS MADE

THIS BOOK POSSIBLE

FOREWORD TO TEACHERS

A COURSE in biology given to beginners in the secondary school
should have certain aims. These aims must be determined to a
degree, first, by the capabilities of the pupils, second, by their
native interests, and, third, by the environment of the pupils.

The boy or girl of average ability upon admission to the second
ary school is not a thinking individual. The training given up to
this time, with but rare exceptions, has been in the forming of
simple concepts. These concepts have been reached didactically
and empirically. Drill and memory work have been the peda
gogic vehicles. Even the elementary science work given has
resulted at the best in an interpretation of some of the common
factors in the pupil's environment, and a widening of the mean
ing of some of his concepts. Therefore, the first science of the
secondary school, elementary biology, should be primarily the
vehicle by which the child is taught to solve problems and to think
straight in so doing. No other subject is more capable of logical
development. No subject is more vital because of its relation
to the vital things in the life of the child. A series of experiments
and demonstrations, discussed and applied as definite concrete
problems which have arisen within the child's horizon, will develop
power in thinking more surely than any other subject in the first
year of the secondary school.

But in our eagerness to develop the power of logical thinking
we must not lose sight of the previous training of our pupil. Up
to this time the method of induction, that handmaiden of logical
thought, has been almost unknown. Concepts have been formed
deductively by a series of comparisons. All concepts have been
handed down by the authority of the teacher or the text; the
inductive search for the unknown is as yet a closed book. It is
unwise, then, to directly introduce the pupil to the method of in
duction with a series of printed directions which, though definite
in the mind of the teacher because of his wider horizon, mean

8 FOREWORD TO TEACHERS

little or nothing as a definite problem to the pupil. The child
must be brought to the appreciation of the problem through the
deductive method, by a comparison of the future problem with
some definite concrete experience within his own field of vision.
Then by the inductive experiment, still led by a series of oral
questions, he comes to the real end of the experiment, the conclu
sion, with the true spirit of the investigator. The result is tested
in the light of past experiment and a generalization is formed which
means something to the pupil.

For the above reason the laboratory problems, which naturally
precede the textbook work, should be separated from the subject
matter of the text. A textbook in biology should serve to verify
the student's observations made in the laboratory, it should round
out his concept or generalization by adding such material as he
cannot readily observe and it should give the student directly
such information as he cannot be expected to gain directly or
indirectly through his laboratory experience. For these reasons
the laboratory manual has been separated from the text.

" The laboratory method was such an emancipation from the old-time
bookish slavery of pre-lab oratory days that we may have been inclined
to -overdo it and to subject ourselves to a new slavery. It should never
be forgotten that the laboratory is simply a means to the end ; that the
dominant thing should be a consistent chain of ideas which the laboratory
may serve to elucidate. When, however, the laboratory assumes the first
place and other phases of the course are made explanatory to it, we have
taken, in my mind, an attitude fundamentally wrong. The question is,
not what types may be taken up in the laboratory to be fitted into the
general scheme afterwards, but what ideas are most worth while to be
worked out and developed in the laboratory, if that happens to be the
best way of doing it, or if not, some other way to be adopted with perfect
freedom. Too often our course of study of an animal or plant takes the
easiest rather than the most illuminating path. What is easier, for in
stance, particularly with large classes of restless pupils who apparently
need to be kept in a condition of uniform occupation, than to kill a supply
of animals, preferably as near alike as possible, and set the pupils to work
drawing the dead remains ? This method is usually supplemented by a
series of questions concerning the remains which are sure to keep the
pupils busy a while longer, perhaps until the bell strikes, and which usu
ally are so planned as to anticipate any ideas that might naturally crop
up in the pupil's mind during the drawing exercise.

FOREWORD TO TEACHERS 9

" Such an abuse of the laboratory idea is all wrong and should be avoided.
The ideal laboratory ought to be a retreat for rainy days ; a substitute
for out of doors ; a clearing house of ideas brought in from the outside.
Any course in biology which can be confined within four walls, even if
these walls be of a modern, well-equipped laboratory, is in some measure
a failure. Living things, to be appreciated and correctly interpreted,
must be seen and studied in the open where they will be encountered
throughout life. The place where an animal or plant is found is just as
important a characteristic as its shape or function. Impossible field excur
sions with large classes within school hours, which only bring confusion to
inflexible school programs, are not necessary to accomplish this result.
Properly administered, it is without doubt one of our most efficient de
vices for developing biological ideas, but the laboratory should be kept in
its proper relation to the other means at our disposal and never be allowed
to degenerate either into a place for vacuous drawing exercises or a bio
logical morgue where dead remains are viewed." Dr. II. E. Walter.

For the sake of the pupil the number of technical and scientific
terms has been reduced to a minimum. The language has been
made as simple as possible and the problems made to hinge upon
material already known, by hearsay at least, to the pupil. So far
as consistent with a well-rounded course in the essentials of bio
logical science, the interests of the children have been kept in the
foreground. In a recent questionnaire sent out by the author and
answered by over three thousand children studying biology in the
secondary schools of Connecticut, Massachusetts, New Jersey,
and New York by far the greatest number gave as the most
interesting topics those relating to the care and functions of the
human body and the control and betterment of the environment.
As would be expected, boys have different biological interests from
girls, and children in rural schools wish to study different topics
from those in congested districts in large communities. The time
has come when we must frankly recognize these interests and
adapt the content of our courses in biology to interpret the
immediate world of the pupil.

With this end in view the following pages have been written.
This book shows boys and girls living in an urban community
how they may best live within their own environment and how
they may cooperate with the civic authorities for the betterment
of their environment. A logical course is built up around the

10 FOREWORD TO TEACHERS

topics which appeal to the average normal boy or girl, topics given
in a logical sequence so as to work out the solution of problems
bearing on the ultimate problem of the entire course, that of prep
aration for citizenship in the largest sense.

Seasonal use of materials has been kept in mind in outlining
this course. Field trips, when properly organized and later used
as a basis for discussion in the classroom, make a firm foundation
on which to build the superstructure of a course in biology. The
normal environment, its relation to the artificial environment of
the city, the relations of mutual give and take existing between
plants and animals, are better shown by means of field trips than
in any other way. Field and museum trips are enjoyed by the
pupils as well. These result in interest and in better work. The
course is worked up around certain great biological principles ;
hence insects may be studied when abundant in the fall in connec
tion with their relations to green plants and especially in their re
lation to flowers. In the winter months material available for the
laboratory is used. Saprophytic and parasitic organisms, wild
plants in the household, are studied in their relations to man
kind, both as destroyers of food, property and life and as man's
invaluable friends. The economic phase of biology may well be
taken up during the winter months, thus gaining variety in sub
ject matter and in method of treatment. The apparent emphasis
placed upon economic material in the following pages is not real.
It has been found that material so given makes for variety, as it
may be assigned as a topical reading lesson or simply used as
reference when needed. Cyclic work in the study of life phenom
ena and of the needs of organisms for oxygen, food, and reproduc
tion culminates, as it rightly should, in the study of life-processes
of man and man's relation to his environment.

In a course in biology the difficulty comes not so much in know
ing what to teach as in knowing what not to teach. The author
believes that he has made a selection of the topics most vital in a
well-rounded course in elementary biology directed toward civic
betterment. The physiological functions of plants and animals,
the hygiene of the individual within the community, conservation
and the betterment of existing plant and animal products, the

FOREWORD TO TEACHERS 11

big underlying biological concepts on which society is built, have
all been used to the end that the pupil will become a better,
stronger and more unselfish citizen. The " spiral " or cyclic
method of treatment has been used throughout, the purpose being
to ultimately build up a number of well-rounded concepts by
constant repetition but with constantly varied viewpoint.

The sincere thanks of the author is extended to all who have
helped make this book possible, and especially to the members
of the Department of Biology in the De Witt Clinton High School.
Most of the men there have directly or indirectly contributed
their time and ideas to help make this book worth more to teachers
and pupils. The following have read the manuscript in its entirety
and have offered much valuable constructive criticism : Dr. Herbert
E. Walter, Professor of Zoology in Brown University ; Miss Elsie
Kupfer, Head of the Department of Biology in Wadleigh High
School; George C. Wood, of the Department of Biology in the
Boys' High School, Brooklyn ; Edgar A. Bedford, Head of Depart
ment of Biology in the Stuyvesant High School ; George E. Hew
itt, George T. Hastings, John D. McCarthy, and Frank M. Wheat,
all of the Department of Biology in the De Witt Clinton High
School.

Thanks are due, also, to Professor E. B. Wilson, Professor G. N.
Calkins, Mr. William C. Barbour, Dr. John A. Sampson, W. C.
Stevens, and C. W. Beebe, Dr. Alvin Davison, and Dr. Frank
Overton ; to the United States Department of Agriculture ; the
New York Aquarium ; the Charity Organization Society ; and the
American Museum of Natural History, for permission to copy and
use certain photographs and cuts which have been found useful in
teaching. Dr. Charles H. Morse and Dr. Lucius J. Mason, of the
De Witt Clinton High School, prepared the hygiene outline in the
appendix. Frank M. Wheat and my former pupil, John W. Teitz,
now a teacher in the school, made many of the line drawings and
took several of the photographs of experiments prepared for this
book. To them especially I wish to express my thanks.

At the end of each of the following chapters is a list of books
which have proved their use either as reference reading for students
or as aids to the teacher. Most of the books mentioned are within

12 FOREWORD TO TEACHERS

the means of the small school. Two sets are expensive : one, The
Natural History of Plants, by Kerner, translated by Oliver, pub
lished by Henry Holt and Company, in two volumes, at $11 ; the
other, Plant Geography upon a Physiological Basis, by Schimper,
published by the Clarendon Press, $12 ; but both works are inval
uable for reference.

For a general introduction to physiological biology, Parker,
Elementary Biology, The Macmillan Company; Sedgwick and
Wilson, General Biology, Henry Holt and Company; Verworn,
General Physiology, The Macmillan Company ; and Needham, Gen
eral Biology, Comstock Publishing Company, are most useful and
inspiring books.

Two books stand out from the pedagogical standpoint as by far
the most helpful of their kind on the market. No teacher of
botany or zoology can afford to be without them. They are :
Lloyd and Bigelow, The Teaching of Biology, Longmans, Green,
and Company, and C. F. Hodge, Nature Study and Life, Ginn and
Company. Other books of value from the teacher's standpoint
are : Ganong, The Teaching Botanist, The Macmillan Company ;
L. H. Bailey, The Nature Study Idea, Doubleday, Page, and Com
pany ; and McMurry's How to Study, Houghton Mifflin Company.

CONTENTS

CHAPTER

FOREWORD TO TEACHERS ....... 7

I. SOME REASONS FOR THE STUDY OF BIOLOGY. ... 15

II. THE ENVIRONMENT OF PLANTS AND ANIMALS ... 19

III. THE INTERRELATIONS OF PLANTS AND ANIMALS . . 28

IV. THE FUNCTIONS AND COMPOSITION OF LIVING THINGS . 47
V. PLANT GROWTH AND NUTRITION THE CAUSES OF GROWTH 58

VI. THE ORGANS OF NUTRITION IN PLANTS THE SOIL AND

ITS RELATION TO ROOTS , ..... 71

VII. PLANT GROWTH AND NUTRITION PLANTS MAKE FOOD . 84
VIII. PLANT GROWTH AND NUTRITION THE CIRCULATION AND

FINAL USES OF FOOD BY PLANTS .... 97

IX. OUR FORESTS, THEIR USES AND THE NECESSITY OF THEIR

PROTECTION ......... 105

X. THE ECONOMIC RELATION OF GREEN PLANTS TO MAN . 117
XL PLANTS WITHOUT CHLOROPHYLL IN THEIR RELATION TO

MAN ........... 130

XII. THE RELATIONS OF PLANTS TO ANIMALS .... 159

XIII. SINGLE-CELLED ANIMALS CONSIDERED AS ORGANISMS . 166

XIV. DIVISION OF LABOR, THE VARIOUS FORMS OF PLANTS AND

ANIMALS .......... 173

XV. THE ECONOMIC IMPORTANCE OF ANIMALS .... 197

XVI. AN INTRODUCTORY STUDY OF VERTEBRATES . . . 232

XVII. HEREDITY, VARIATION, PLANT AND ANIMAL BREEDING . 249

XVIII. THE HUMAN MACHINE AND ITS NEEDS .... 266

XIX. FOODS AND DIETARIES ........ 272

XX. DIGESTION AND ABSORPTION. ...... 296

14 CONTENTS

CHAPTER

XXL THE BLOOD AND ITS CIRCULATION

PAGE

. 313

XXII. RESPIRATION AND EXCRETION
XXIII. BODY CONTROL AND HABIT FORMATION
XXIV. MAN'S IMPROVEMENT OF HIS ENVIRONMENT

. 329
. 348
. 373

. 398

APPENDIX

407

SUGGESTED COURSE WITH TIME ALLOTMENT AND SEQUENCE

OF TOPICS FOR COURSE BEGINNING IN FALL . . 407
SUGGESTED SYLLABUS FOR COURSE IN BIOLOGY BEGINNING

IN FEBRUARY AND ENDING THE NEXT JANUARY . 411

HYGIENE OUTLINE 415

WEIGHTS, MEASURES, AND TEMPERATURES . . . 417

SUGGESTIONS FOR LABORATORY EQUIPMENT . . . 418

INDEX , 419

A CIVIC BIOLOGY

I. THE GENERAL PROBLEM SOME REASONS FOR
THE STUDY OF BIOLOGY

What is Biology? Biology is the study of living beings, both
plant and animal. Inasmuch as man is an animal, the study of
biology includes the study of man in his relations to the plants
and the animals which surround him. Most important of all
is that branch of biology which treats of the mechanism we call
the human body, of its parts and their uses, and its repair.
This subject we call human physiology.

Why study Biology? Although biology is a very modern
science, it has found its way into most high schools ; and an in
creasingly large number of girls and boys are yearly engaged in its
study. These questions might well be asked by any of the students :
Why do I take up the study of biology ? Of what practical value
is it to me ? Besides the discipline it gives me, is there anything
that I can take away which will help me in my future life ?

Human Physiology. The answer to this question is plain.
If the study of biology will give us a better understanding of our
own bodies and their care, then it certainly is of use to us. That
phase of biology known as physiology deals with the uses of the
parts of a plant or animal; human physiology and hygiene deal
with the uses and care of the parts of the human animal. The
prevention of sickness is due in a large part to the study of hygiene.
It is estimated that over twenty-five per cent of the deaths that
occur yearly in this country could be averted if all people lived in
a hygienic manner. In its application to the lives of each of us, as
a member of our family, as a member of the school we attend,
and as a future citizen, a knowledge of hygiene is of the greatest
importance.

Relations of Plants to Animals. But there are other reasons
why an educated person should know something about biology.

16 SOME REASONS FOR STUDYING BIOLOGY

We do not always realize that if it were not for the green plants,
there would be no animals on the earth. Green plants furnish
food to animals. Even the meat-eating animals feed upon those
that feed upon plants. How the plants manufacture this food
and the relation they bear to animals will be discussed in later
chapters. Plants furnish man with the greater part of his food
in the form of grains and cereals, fruits and nuts, edible roots and
leaves; they provide his domesticated animals with food; they
give him timber for his houses and wood and coal for his fires;
they provide him with pulp wood, from which he makes his paper,
and oak galls, from which he may make ink. Much of man's cloth
ing and the thread with which it is sewed together come from
fiber-producing plants. Most medicines, beverages, flavoring ex
tracts, and spices are plant products, while plants are made use of
in hundreds of ways in the useful arts and trades, producing var
nishes, dyestuffs, rubber, and other products.

Bacteria in their Relation to Man. In still another way, cer
tain plants vitally affect mankind. Tiny plants, called bacteria,
so small that millions can exist in a single drop of fluid, exist
almost everywhere about us, in water, soil, food, and the air.
They play a tremendous part in shaping the destiny of man on
the earth. They help him in that they act as scavengers, causing
things to decay ; thus they remove the dead bodies of plants and
animals from the surface of the earth, and turn this material back
to the ground ; they assist the tanner ; they help make cheese and
butter ; they improve the soil for crop growing ; so the farmer can
not do without them. But they likewise sometimes spoil our meat
and fish, and our vegetables and fruits; they sour our milk, and
may make our canned goods spoil. Worst of all, they cause dis
eases, among others tuberculosis, a disease so harmful as to be
called the " white plague." Fully one half of all yearly deaths are
caused by these plants. So important are the bacteria that a sub
division of biology, called bacteriology, has been named after them,
and hundreds of scientists are devoting their lives to the study of
bacteria and their control. The greatest of all bacteriologists,
Louis Pasteur, once said, " It is within the power of man to cause
all parasitic diseases (diseases mostly caused by bacteria) to disap-

SOME REASONS FOR STUDYING BIOLOGY 17

pear from the world." His prophecy is gradually being fulfilled,
and it may be the lot of some boys or girls who read this book to
do their share in helping to bring this condition of affairs about.

The Relation of Animals to Man. Animals also play an im
portant part in the world in causing and carrying disease. Ani
mals that cause disease are usually tiny, and live in other
animals as parasites ; that is, they get their living from their hosts
on which they feed. Among the diseases caused by parasitic
animals are malaria, yellow fever, the sleeping sickness, and the
hookworm disease. Animals also carry disease, especially the
flies and mosquitoes ; rats and other animals are also well known
as spreaders of disease.

From a money standpoint, animals called insects do much harm.
It is estimated that in this country alone they are annually re
sponsible for $800,000,000 worth of damage by eating crops, forest
trees, stored food, and other material wealth.

The Uses of Animals to Man. We all know the uses man
has made of the domesticated animals for food and as beasts of
burden. But many other uses are found for animal products,
and materials made from animals. Wool, furs, leather, hides,
feathers, and silk are examples. The arts make use of ivory, tor
toise shell, corals, and mother-of-pearl ; from animals come per
fumes and oils, glue, lard, and butter; animals produce honey,
wax, milk, eggs, and various other commodities.

The Conservation of our Natural Resources. Still another
reason why we should study biology is that we may work under-
standingly for the conservation of our natural resources, especially
of our forests. The forest, aside from its beauty and its health-
giving properties, holds water in the earth. It keeps the water
from drying out of the earth on hot days and from running off on
rainy days. Thus a more even supply of water is given to our
rivers, and thus freshets are prevented. Countries that have been
deforested, such as China, Italy, and parts of France, are now sub
ject to floods, and are in many places barren. On the forests
depend our supply of timber, our future water power, and the
future commercial importance of cities which, like New York, are
located at the mouths of our navigable rivers.

HUNTER, CIV. DI. 2

18 SOME REASONS FOR STUDYING BIOLOGY

Plants and Animals mutually Helpful. Most plants and ani
mals stand in an attitude of mutual helpfulness to one another,
plants providing food and shelter for animals ; animals giving off
waste materials useful to plants in the making of food. We also
learn that plants and animals need the same conditions in their
surroundings in order to live : water, air, food, a favorable temper
ature, and usually light. The life processes of both plants and
animals are essentially the same, and the living matter of a tree is
as much alive as is the living matter in a fish, a dog, or a man.

Biology in its Relation to Society. Again, the study of biology
should be part of the education of every boy and girl, because so
ciety itself is founded upon the principles which biology teaches.
Plants and animals are living things, taking what they can from
their surroundings ; they enter into competition with one another,
and those which are the best fitted for life outstrip the others.
Animals and plants tend to vary each from its nearest relative in all
details of structure. The strong may thus hand down to their
offspring the characteristics which make them the winners. Health
and strength of body and mind are factors which tell in winning.

Man has made use of this message of nature, and has developed
improved breeds of horses, cattle, and other domestic animals.
Plant breeders have likewise selected the plants or seeds that have
varied toward better plants, and thus have stocked the earth with
hardier and more fruitful domesticated plants. Man's dominion
over the living things of the earth is tremendous. This is due to his
understanding the principles which underlie the science of biology.

Finally the study of biology ought to make us better men
and women by teaching us that unselfishness exists in the natural
world as well as among the highest members of society. Ani
mals, lowly and complex, sacrifice their comfort and their very
lives for their young. In the insect communities the welfare of
the individual is given up for the best interests of the community.
The law of mutual give and take, of sacrifice for the common good,
is seen everywhere. This should teach us, as we come to take our
places in society, to be willing to give up our individual pleasure
or selfish gain for the good of the community in which we live.
Thus the application of biological principles will benefit society.

II. THE ENVIRONMENT OF PLANTS AND ANIMALS

Problem. To discover some of the factors of the environ
ment of plants and animals.
(a) Environment of a plant.
(&) Environment of an animal.
(c) Howie environment of a girl or boy.

LABORATORY SUGGESTIONS

Laboratory demonstrations. Factors of the environment of a living
plant or animal in the vivarium.

Home exercise. The study of the factors making up my own environ
ment and how I can aid in their control.

Environment. Each one of us, no matter where he lives, comes
in contact with certain surroundings. Air is everywhere around

us ; light is necessary to us, so much so
that we use artificial light at night. The
city street, with its dirty and hard paving
stones, has come to take the
place of the soil of the village
or farm. Water and food are
a necessary part of our sur
roundings. Our clothing,
useful to maintain a certain
temperature, must also be
included. All these things
air, light, heat, water, food together
make up our environment.

All other animals, and all plants as

An unfavorable city environ- Well > are surrounded by and US6 prac-

ment. tically the same things from their en

vironment as we do. The potted plant

in the window, the goldfish in the aquarium, your pet dog at
home, all use, as we will later prove, the factors of their environ-

20 ENVIRONMENT OF PLANTS AND ANIMALS

ment in the same manner. Air, water, light, a certain amount of
heat, soil to live in or on, and food form parts of the surroundings
of every living thing.

The Same Elements found in Plants
and Animals as in their Environment.
- It has been found by chemists that
the plants and animals as well as their
environment may be reduced to about
eighty very simple substances known
as chemical elements. For example,
the air is made up largely of two ele
ments, oxygen and nitrogen. Water,
by means of an electric current, may
be broken up into two elements, oxygen
and hydrogen. The elements in water
are combined to make a chemical com
pound. The oxygen and nitrogen of
the air are not so united, but exist as
separate gases. If we were to study

An experiment that shows the
air contains about four fifths
nitrogen.

Apparatus for separating
water by means of an
electric current into the
two elements, hydrogen
and oxygen.

the chemistry of the bodies of plants and animals and of their
foods, we would find them to be made up of certain chemical
elements combined in various complex compounds. These ele
ments are principally carbon, hydrogen, oxygen, nitrogen, and
perhaps a dozen others in very minute proportions. But the
same elements present in the living things might also be found

ENVIRONMENT OF PLANTS AND ANIMALS 21

SULPHUR

PHOSPHORUjsTTl

CALCIUM f~n

HYDROGEN
I3.651ts.

CARBON

OXYGEN

108.15 Its.

in the environment, for example, water, food, the air, and the soil.
It is logical to believe that living things use the chemical elements
in their surroundings arid in some won
derful manner build up their own bodies
from the materials found in their en
vironment. How this is done we will
learn in later chapters.

What Plants and Animals take from
their Environment. Air. It is a self-
evident fact that animals need air.
Even those living in the water use the
air dissolved in the water. A fish
placed in an air-tight jar will soon die.
It will be proven later that plants also
need air in order to live.

Water. We all know that water
must form part of the environment of
plants and animals. It is a matter of
common knowledge that pets need
water to drink ; so do other animals.
Every one knows we "must water a

potted plant if we expect it to grow. Chart to show the percentage

Water is of so much importance to man

that from the time of the Caesars until

now he has spent enormous sums of money to bring pure water

to his cities. The United States government is spending millions

of dollars at the present time to bring by irrigation the water

needed to support life in the western desert lands.

Light as Condition of the Environment. Light is another im
portant factor of the environment. A study of the leaves on any
green plant growing near a window will convince one that such
plants grow toward the light. All green plants are thus influenced
by the sun. Other plants which are not green seem either indif
ferent or are negatively influenced (move away from) the source
of light. Animals may or may not be attracted by light. A
moth, for example, will fly toward a flame, an earthworm will
move away from light. Some animals prefer a moderate or

of chemical elements in the
human body.

22 ENVIRONMENT OF PLANTS AND ANIMALS

The effect of water upon the growth of trees. These trees were all planted at th^
same time in soil that is sandy and uniform. They are watered by a small
stream which runs from left to right in the picture. .Most of the water soaks
into the ground before reaching the last trees.

weak intensity of light and live in shady forests or jungles,
prowling about at night. Others seem to need much and strong

light. And man himself
enjoys only moderate in
tensity of light and heat.
Look at the shady side of
a city street on any hot
day to prove this state
ment.

Heat. Animals and
plants are both affected
by heat or the absence of

The effect of light upon a growing plant.

it. In cold weather green
plants either die or their

life activities are temporarily suspended, the plant becomes
dormant. Likewise small animals, such as insects, may be killed
by cold or they may hibernate under stones or boards. Their
life activities are stilled until the coming of warm weather. Bears

ENVIRONMENT OF PLANTS AND ANIMALS 23

and other large animals go to sleep during the winter and awake
thin and active at the approach of warm weather. Animals or
plants used to certain temperatures are killed if removed from
those temperatures. Even man, the most adaptable of all ani
mals, cannot stand great changes without discomfort and some
times death. He heats his houses in winter and cools them in
summer so as to have the amount of heat most acceptable to him,
i.e. about 70 Fahrenheit.

The Environment determines the Kind of Animals and Plants
within It. In our study of geography we learned that certain

Vegetation in Northern Russia. The trees in this picture are nearly one hundred
years old. They live under conditions of extreme cold most of the year.

luxuriant growths of trees and climbing plants were characteristic
of the tropics with its moist, warm climate. No one would expect
to find living there the hardy stunted plants of the arctic region.
Nor would we expect to find the same kinds of animal life in warm
regions as in cold. The surroundings determine the kind of living
things there. Plants or animals fitted to live in a given locality
will probably be found there if they have had an opportunity to

24 ENVIRONMENT OF PLANTS AND ANIMALS

reach that locality. If, for example, temperate forms of life were
introduced by man into the tropics, they would either die or they
would gradually change so as to become fitted to live in their new
environment. Sheep with long wool fitted to live in England,
when removed to Cuba, where conditions of greater heat exist,

Plant life in a moist tropical forest. Notice the air plants to the left and the
resurrection ferns on the tree trunk.

soon died because they were not fitted or adapted to live in their
changed environment.

Adaptations. Plants and animals are not only fitted to live
under certain conditions, but each part of the body may be fitted to
do certain work. I notice that as I write these words the fingers
of my right hand grasp the pen firmly and the hand and arm exe
cute some very complicated movements. This they are able to
do because of the free movement given through the arrangement
of the delicate bones of the wrist and fingers, their attachment
to the bones of the arm, a wonderful complex of muscles which
move the bones, and a directing nervous system which plans
the work. Because of the peculiar fitness in the structure of the

ENVIRONMENT OF PLANTS AND ANIMALS 25

hand for this work we say it is adapted to its function of grasping
objects. Each part of a plant or animal is usually fitted for some
particular work. The root of a green plant, for example, is fitted
to take in water by having tiny absorbing organs growing from it,
the stems have pipes or tubes to convey liquids up and down and
are strong enough to support the leafy part of the plant. Each
part of a plant does work, and is fitted, by means of certain struc
tures, to do that work. It is because of these adaptations that
living things are able to do their work within their particular en
vironment.

Plants and Animals and their Natural Environment. Those
of us who have tried to keep potted plants in the schoolroom
know how difficult it is to keep them healthy. Dust, foreign
gases in the air, lack of moisture, and other causes make the
artificial environment in which they are placed unsuitable for
them.

A goldfish placed in a small glass jar with no food or no green
water plants soon seeks
the surface of the water,
and if the water is not
changed frequently so as
to supply air the fish will
die. Again the artificial
environment lacks some
thing that the fish needs.
Each plant and animal is
limited to a certain en
vironment because of cer
tain individual needs which
make the surroundings fit
for it to live in.

Changes in Environ
ment. Most plants and
animals .do not change
their environment. Trees,
green plants of all kinds, A natural barrier on a stream No trout

and some animals remain would be found above this fall. Why not ?

26 ENVIRONMENT OF PLANTS AND ANIMALS

fixed in one spot practically all their lives. Certain tiny plants
and most animals move from place to place, either in air, water,
on the earth or in the earth, but they maintain relatively the
same conditions in environment. Birds are perhaps the most
striking exception, for some may fly thousands of miles from
their summer homes to winter in the south. Other animals, too,
migrate from place to place, but not usually where there are
great changes in the surroundings. A high mountain chain with
intense cold at the upper altitudes would be a barrier over which, for
example, a bear, a deer, or a snail could not travel. Fish like trout
will migrate up a stream until they come to a fall too high for them
to jump. There they must stop because their environment limits
them.

Man in his Environment. Man, while he is like other animals
in requiring heat, light, water, and food, differs from them in that

he has come to live in a
more or less artificial en
vironment. Men who
lived on the earth thou
sands of year ago did not
wear clothes or have elab
orate homes of wood or
brick or stone. They did
not use fire, nor did they
eat cooked foods. In
short, by slow degrees,
civilized man has come to
live in a changed environ
ment from that of other
animals. The living to
gether of men in com
munities has caused cer
tain needs to develop.
Many things can be sup-

A new apartment house, with out-of-door ~

sleeping porch. plied in common, as water,

milk, foods. Wastes of all
kinds have to be disposed of in a town or city. Houses have come

ENVIRONMENT OF PLANTS AND ANIMALS 27

to be placed close together, or piled on top of each other, as in the
modern apartment. Fields and trees, all outdoor life, has practi
cally disappeared. Man has come to live in an artificial envi
ronment.

Care and Improvement of One's Environment. Man can
modify or change his surroundings by making this artificial en
vironment favorable to live in. He may heat his dwellings in
winter and cool them in summer so as to maintain a moderate and
nearly constant temperature. He may see that his dwellings have
windows so as to let light and air pass in and out. He may have
light at night and shade by day from intense light. He may have
a system of pure water supply and may see that drains or sewers
carry away his wastes. He may see to it that people ill with
" catching " or infectious diseases are isolated or quarantined from
others. This care of the artificial environment is known as sanita
tion, while the care of the individual for himself within the environ
ment is known as hygiene. It will be the chief end of this book to
show girls and boys how they may become good citizens through
the proper control of personal hygiene and sanitation.

REFERENCE BOOKS

ELEMENTARY

Hunter, Laboratory Problems in Civic Biology. American Book Company.
Hough and Sedgwick, Elements of Hygiene and Sanitation. Ginn and Company.
Jordan and Kellogg, Animal Life. Appleton.

Sharpe, A Laboratory Manual for the Solution of Problems in Biology, p. 95. Amer
ican Book Company.
Tolman, Hygiene for the Worker. American Book Company.

ADVANCED

Allen, Civics and Health. Ginn and Company.

III. THE INTERRELATIONS OF PLANTS AND ANIMALS

Problem. To discover the general interrelations of green
plants and animals.

(a) Plants as homes for insects.
(#) Plants as food for insects.
(c) Insects as pollinating agents.

LABORATORY SUGGESTIONS

A field trip: Object : to collect common insects and study their gen
eral characteristics ; to study the food and shelter relation of plant and
insects. The pollination of flowers should also be carefully studied so as
to give the pupil a general viewpoint as an introduction to the study of
biology.

Laboratory exercise. Examination of simple insect, identification of
parts drawing. Examination and identification of some orders of
insects.

Laboratory demonstration. Life history of monarch and some other
butterflies or moths.

Laboratory exercise. Study of simple flower emphasis on work of
essential organs, drawing.

Laboratory exercise. Study of mutual adaptations in a given insect
and a given flower, e.g. butter and eggs and bumble bee.

Demonstration of examples of insect pollination.

The Object of a Field Trip. Many of us live in the city, where
the crowded streets, the closely packed apartments, and the city
playgrounds form our environment. It is very artificial at best.
To understand better the normal environment of plants or animals
we should go into the country. Failing in this, an overgrown city
lot or a park will give us much more closely the environment as it
touches some animals lower than man. We must then remember
that in learning something of the natural environment of other
living creatures we may better understand our own environment
and our relation to it.

INTERRELATIONS OF PLANTS AND ANIMALS 29

On any bright warm day in the fall we will find insects swarming
everywhere in any vacant lot or the leas cultivated parts of a city
park. Grasshoppers, butterflies alighting now and then on the
flowers, brightly marked hornets, bees busily working over the
purple asters or golden rod, and many other forms hidden away
on the leaves or stems of plants may be seen. If we were to select
for observation some partially decayed tree, we would find it also
inhabited. Beetles would be found boring through its bark and
wood, while caterpillars (the young stages of butterflies or moths)
are feeding on its leaves or building homes in its branches. Every
where above, on, and under ground may be noticed small forms of
life, many of them insects. Let us first see how we would go to
work to identify some of the common forms we would be likely to
find on plants. Then a little later we will find out what they are
doing on these plants.

How to tell an Insect. A bee is a good example of the group
of animals we call insects. If we examine its body carefully, we
notice that it has three regions, a
front part or head, a middle part
called the thorax, and a hind portion,
jointed and hairy, the abdomen. We
cannot escape noting the fact that this
insect has wings with which it flies
and that it also has legs. The three
pairs of legs, which are jointed and
provided with tiny hooks at the end,
are attached to the thorax. Two
pairs of delicate wings are attached
to the upper or dorsal side of the
thorax. The thorax and indeed the
entire body, is covered with a hard
shell of material similar to a cow's
horn, there being no skeleton inside for
the attachment of muscles. If we
carefully watch the abdomen of a

living bee, we notice it move up and down quite regularly. The
animal is breathing through tiny breathing holes called spiracles,

An insect viewed from the side.
Notice the head, thorax, and
abdomen. What other char
acters do you find ?

30 INTERRELATIONS OF PLANTS AND ANIMALS

placed along the side of the thorax and abdomen. Bees also have
compound eyes. Wings are not found on all insects, but all the
other characters just given are marks of the
great group of animals we call insects.

Forms to be looked for on a Field Trip. -
Inasmuch as there are over 360,000 different
species or kinds of insects, it is evident that it
would be a hopeless task for us even to think of
recognizing all of them. But we can learn to

Part of the com- / -, /. ,-, f

pound eye of an recognize a few examples of the common forms

insect (highly mag- that might be met on a field trip. In the fields,
on grass, or on flowering plants we may count on
finding members from six groups or orders of insects. These may
be known by the following characters.

The order Hymenoptera (membrane wing) to which the bees,
wasps, and ants belong is the only insoct group the members of
which are provided with true stings. This sting is placed in a
sheath at the extreme hind end of the abdomen. Other charac
teristics, which show them to be insects, have been given above.

Butterflies or moths will be found hovering over flowers. They
belong to the order Lepidoptera (scale wings). This name is
given to them because their wings are covered with tiny scales,
which fit into little sockets on the wing much as shingles are placed
on a roof. The dust which comes off on the fingers when one
catches a butterfly is composed of these scales. The wings are
always large and usually brightly colored, the legs small, and one
pair is often inconspicuous. These insects may be seen to take
liquid food through a long tubelike organ, called the proboscis,
which they keep rolled up under the head when not in use. The
young of the butterfly or moth are known as caterpillars and feed
on plants by means of a pair of hard jaws.

Grasshoppers, found almost everywhere, and crickets, black
grasshopper-like insects often found under stones, belong to the
order Orthoptera (straight wings). Members of this group may
usually be distinguished by their strong, jumping hind legs, by
their chewing or biting mouth parts, and by the fact that the hind
wings are folded up under the somewhat stiffer front wings.

INTERRELATIONS OF PLANTS AND ANIMALS 31

Another group of insects sometimes found on flowers in the fall
are flies. They belong to the order Diptera (two wings). These
insects are usually rather small and have a single pair of gauzy

Forms of life to be met on a field trip. A, The red-legged locust, one of the
Orthopterctr o, the egg-layer, about natural size. B, the honey bee, one of
the Hymsnoptera, about natural size. C, a bug, one of the Hemiptera, about
natural size. D, a butterfly, an example of the Lepidoptera, slightly reduced.
E, a house fly, an example of the Diptera, about twice natural size. F, an
orb-weaving spider, about half natural size. (This is not an insect, note the
number of legs.) G, a beetle, slightly reduced, one of the Coleoptera.

32 INTERRELATIONS OF PLANTS AND ANIMALS

wings. Flies are of much importance to man because certain of
their number are disease carriers.

Bugs, members of the order Hemiptera (half wings), have a
jointed proboscis which points backward between the front legs.
They are usually small and may or may not have wings.

The beetles or Coleoptera (sheath wings), often mistaken for
bugs by the uneducated, have the first pair of hardened wings
meeting in a straight line in the middle of the back, the second
pair of wings being covered by them. Beetles are frequently found
on goldenrod blossoms in the fall.

Other forms of life, especially spiders, which have four pairs of
walking legs, centipedes and millepedes, both of which are worm-
like and have many pairs of legs, may be found.

Try to discover members of the six different orders named
above. Collect specimens and bring them to the laboratory for
identification.

Why do Insects live on Plants ? We have found insect life
abundant on living green plants, some visiting flowers, others
hidden away on the stalks or leaves of the plants. Let us next
try to find out why insects live among and upon flowering green
plants.

The Life History of the Milkweed Butterfly. If it is possible
to find on our trip some growing milkweed, we are quite likely to
find hovering near, a golden brown and black butterfly, the monarch
or milkweed butterfly (Anosia plexippus). Its body, as in all
insects, is composed of three regions. The monarch frequents
the milkweed in order to lay eggs there. This she may be found
doing at almost any time from June until September.

Egg and Larva. The eggs, tiny hat-shaped dots a twentieth of
an inch in length, are fastened singly to the underside of milkweed
leaves. Some wonderful instinct leads the animal to deposit the
eggs on the milkweed, for the young feed upon no other plant.
The eggs hatch out in four or five days into rapid-growing worm-
like caterpillars, each of which will shed its skin several times
before it becomes full size. These caterpillars possess, in addition
to the three pairs of true legs, additional pairs of prolegs or cater
pillar legs. The animal at this stage is known as a larva.

INTERRELATIONS OF PLANTS AND ANIMALS 33

Formation of Pupa. After a life of a few weeks at most, the
caterpillar stops eating and begins to spin a tiny mat of silk upon
a leaf or stem. It attaches itself to this web by the last pair of
prolegs, and there hangs in the dormant stage known as the
chrysalis or pupa. This is a resting stage during which the body
changes from a cater
pillar to a butterfly.

The Adult. After
a week or more of
inactivity in the pupa
state, the outer skin
is split along the
back, and the adult
butterfly emerges. At
first the wings are soft
and much smaller
than in the adult.
Within fifteen minutes
to half an hour after
the butterfly emerges,
however, the wings
are full-sized, having
been pumped full of
blood and air, and the
little insect is ready

after her Wedding flight Monarch butterfly: adults, larvse, and pupa on their

to follow her instinct food plant, the milkweed. (From a photograph

., ! loaned by the American Museum of Natural

to deposit her eggs on History.)
a milkweed plant.

Plants furnish Insects with Food. Food is the most important
factor of any animal's environment. The insects which we have
seen on our field trip feed on the green plants among which they
live. Each insect has its own particular favorite food plant or
plants, and in many cases the eggs of the insect are laid on the
food plant so that the young may have food close at hand. Some
insects prefer the rotted wood of trees. An American zoologist,
Packard, has estimated that over 450 kinds of insects live upon

HUNTER, CIV. BI. 3

34 INTERRELATIONS OF PLANTS AND ANIMALS

oak trees alone. Everywhere animals are engaged in taking their
nourishment from plants, and millions of dollars of damage is done

every year to gardens,
fruits, and cereal crops
by insects.

All Animals depend on
Green Plants. But in
sects in their turn are the
food of birds ; cats and
clogs may kill birds ; lions
or tigers live on still larger
defenseless animals as deer
or cattle. And finally
comes man, who eats the
bodies of both plants and
animals. But if we reduce

Damage done by insects. These trees have
been killed by boring insects.

this search after food to its final limit, we see that green plants
provide all the food for animals. For the lion or tiger eats the
deer which feeds upon grass or green shoots of young trees, or
the cat eats the bird that lives on weed seeds. Green plants
supply the food of the world. Later by experiment we will prove
this.

Homes and Shelter. After a field trip no one can escape the
knowledge that plants often give animals a home. The grass
shelters millions of grasshoppers and countless hordes of other small
insects which can be obtained by sweeping through the grass with
an insect net. Some insects build their homes in the trees or
bushes on which they feed, while others tunnel through the wood,
making homes there. Spiders build webs on plants, often using
the leaves for shelter. Birds nest in trees, and many other wild
animals use the forest as their home. Man has come to use all
kinds of plant products to aid him in making his home, wood and
various fibers being the most important of these.

What do Animals do for Plants ? So far it has seemed that
green plants benefit animals and receive nothing in return. We
will later see that plants and animals together form a balance of life
on the earth and that one is necessary for the other. Certain

INTERRELATIONS OF PLANTS AND ANIMALS 35

substances found in the body wastes from animals are necessary
to the life of a green plant.

Insects and Flowers. Certain other problems can be worked
out in the fall of the year. One of these is the biological interre
lations between insects and flowers. It is easy on a field trip to
find insects lighting upon flowers. They evidently have a reason
for doing this. To find out why they go there and what they do
when there, it will be first necessary
for us to study flowers with the idea
of finding out what the insects get
from them, and what the flowers
get from the insects.

The Use and Structure of a
Flower. It is a matter of common
knowledge that flowers form fruits
and that fruits contain seeds. They
are, then, very important parts of
certain plants. Our field trip shows
us that flowers are of various shapes,
colors, and sizes. It will now be
our problem first to learn to know
the parts of a flower, and then find
out how they are fitted to attract
and receive insect visitors.

The Floral Envelope. In* a
flower the expanded portion of the
flower stalk, which holds the parts
of the flower, is called the receptacle.
The green leaflike parts covering the
unopened flower are called the sepals.
Together they form the calyx.

The more brightly colored structures
are the petals. Together they form
the corolla. The corolla is of importance, as we shall see later,
in making the flower conspicuous. Frequently the petals or
corolla have bright marks or dots which lead down to the base of
the cup of the flower, where a sweet fluid called nectar is made and

A section of a flower, cut lengthwise.
In the center find the pistil with
the ovary containing a number of
ovules. Around this organ notice
a circle of stalked structures, the
stamens; the knobs at the end
contain pollen. The outer circles
of parts are called the petals and
sepals, as we go from the inside
outward.

36 INTERRELATIONS OF PLANTS AND ANIMALS

secreted. It is principally this food substance, later made into
honey by bees, that makes flowers attractive to insects.

The Essential Organs. A flower, however, could live without
sepals or petals and still do the work for which it exists. Certain
essential organs of the flower are within the so-called floral envelope.
They consist of the stamens and pistil, the latter being in the center
of the flower. The structures with the knobbed ends are called
stamens. In a single stamen the boxlike part at the end is the
anther; the stalk which holds the anther is called the filament.
The anther is in reality a hollow box which produces a large
number of little grains called pollen. Each pistil is composed of
a rather stout base called the ovary, and a more or less lengthened
portion rising from the ovary called the style. The upper end of
the style, which in some cases is somewhat broadened, is called the
stigma. The free end of the stigma usually secretes a sweet fluid
in which grains of pollen from flowers of the same kind can grow.

Insects as Pollinating Agents. Insects often visit flowers to
obtain pollen as well as nectar. In so doing they may transfer
some of the pollen from one flower to another of the same kind.
This transfer of pollen, called pollination, is of the greatest use to
the plant, as we will later prove. No one who sees a hive of bees
with their wonderful communal life can fail to see that these insects
play a great part in the life of the flowers near the hive. A famous
observer named Sir John Lubbock tested bees and wasps to see
how many trips they made daily from their homes to the flowers,
and found that the wasp went out on 116 visits during a working
day of 16 hours, while the bee made but a few less visits, and
worked only a little less time than the wasp worked. It is evident
that in the course of so many trips to the fields a bee must light on
hundreds of flowers.

Adaptations in a Bee. If we look closely at the bee, we find the
body and legs more or less covered with tiny hairs ; especially are
these hairs found on the legs. When a plant or animal structure
is fitted to do a certain kind of work, we say it is adapted to do that
work. The joints in the leg of the bee adapt it for complicated
movements; the arrangement of stiff hairs along the edge of a
concavity in one of the joints of the leg forms a structure well

INTERRELATIONS OF PLANTS AND ANIMALS 37

adapted to hold pollen. In this way pollen is collected by the bee
and taken to the hive to be used as food. But while gathering
pollen for itself, the dust is caught on the hairs and other pro-

Bumblebees. , queen; b, worker; c, drone.

jections on the body or legs and is thus carried from flower to
flower. The value of this to a flower we will see later.

Field Work. Is Color or Odor in a Flower an Attraction to an Insect?

Sir John Lubbock tried an experiment which it would pay a number of
careful pupils to repeat. He placed a few drops of honey on glass slips
and placed them over papers of various colors. In this way he found that
the honeybee, for example, could evidently distinguish different colors.
Bees seemed to prefer blue to any other color. Flowers of a yellow or
flesh color were preferred by flies. It would be of considerable interest
for some student to work out this problem with our native bees and with
other insects by using paper flowers and honey or sirup. Test the keen
ness of sight in insects by placing a white object (a white golf ball will do)
in the grass and see how many insects will alight on it. Try to work out
some method by which you can decide whether a given insect is attracted
to a flower by odor alone.

The Sight of the Bumblebee. The large eyes located on the
sides of the head are made up of a large number of little units,
each of which is considered to be a very simple eye. The large
eyes are therefore called the compound eyes. All insects are pro
vided with compound eyes, with simple eyes, or in most cases
with both. The simple eyes of the bee may be found by a careful
observer between and above the compound eyes.

38 INTERRELATIONS OF PLANTS AND ANIMALS

Insects can, as we have already learned, distinguish differences
in color at some distance; they can see moving objects, but they

do not seem to be able
to make out form well.
To make up for this,
they appear to have
an extremely well-
developed sense of
smell. Insects can dis
tinguish at a great dis
tance odors which to the
human nose are indis
tinguishable. Night-
flying insects, espe
cially, find the flowers
by the odor rather
than by color.

Mouth Parts of the
Bee. The mouth of
the bee is adapted to
take in the foods we

have mentioned, and is used for the purposes for which man
would use the hands and fingers. The honeybee laps or sucks
nectar from flowers, it chews the pollen, and it uses part of the
mouth as a trowel in making the honeycomb. The uses of the
mouth parts may be made out by watching a bee on a well-opened
flower.

Suggestions for Field Work. In any locality where flowers are abun
dant, try to answer the following questions: How many bees visit the
locality in ten minutes? How many other insects alight on the flowers?
Do bees visit flowers of the same kinds in succession, or fly from one
flower on a given plant to another on a plant of a different kind ? If the
bee lights on a flower cluster, does it visit more than one flower in the
same cluster? How does a bee alight? Exactly what does the bee do
when it alights?

Butter and Eggs (Linaria vulgaris). From July to October
this very abundant weed may be found especially along roadsides

The head of a bee. A, antennae or "feelers";
E, compound eye; S, simple eye; M, mouth
parts; T, tongue.

INTERRELATIONS OF PLANTS AND ANIMALS 39

and in sunny fields. The flower cluster
forms a tall and conspicuous cluster of
orange and yellow flowers.

The corolla projects into a spur on
the lower side ; an upper two-parted
lip shuts down upon a lower three-
parted lip. The four stamens are in
pairs, two long and two short.

Certain parts of the corolla are more
brightly colored than the rest of the

Flower cluster of " butter and

flower. This color is a
guide to insects. But
ter and eggs is visited
most by bumblebees,
which are guided by
the orange lip to alight
just where they can
push their way into
the flower. The bee,
seeking the nectar secreted in the spur,
brushes his head and shoulders against
the stamens. He may then, as he pushes
down after nectar, leave some pollen upon
the pistil, thus assisting in self-pollination.
Visiting another flower of the cluster, it
would be an easy matter accidentally to transfer

Diagram to show how the bee pollinates "butter and eggs."
The bumblebee, upon entering the flower, rubs its head against the long pair of
anthers (a), then continuing to press into the flower so as to reach the nectar
at (AO it brushes against the stigma (<S), thus pollinating the flower. Inasmuch
as bees visit other flowers in the same cluster, cross-pollination would also be
likely. Why?

40 INTERRELATIONS OF PLANTS AND ANIMALS

this pollen to the stigma of another flower. In this way pollen
is carried by the insect to another flower of the same kind. This
is known as cross-pollination. By pollination we mean the transfer
of pollen from an anther to the stigma of a flower. Self-pollination is
the transfer of pollen from the anther to the stigma of the same flower;
cross-pollination is the transfer of pollen from the anthers of one
flower to the stigma of another flower on the same or another plant
of the same kind.

History of the Discoveries regarding Pollination of Flowers.
Although the ancient Greek and Roman naturalists had some vague

ideas on the subject of pollina
tion, it was not until the first
part of the nineteenth century
that a book appeared in which
a German named Conrad
Sprengel worked out the facts
that the structure of certain
flowers seemed to be adapted
to the visits of insects. Cer
tain facilities were offered to
an insect in the way of easy
foothold, sweet odor, and
especially food in the shape of
pollen and nectar, the latter a
sweet-tasting substance manu
factured by certain parts of the
flower known as the nectar
glands. Sprengel further dis
covered the fact that pollen
could be and was carried by
the insect visitors from the
anthers of the flower to its
stigma. It was not until the middle of the nineteenth century,
however, that an Englishman, Charles Darwin, applied Sprengel's
discoveries on the relation of insects to flowers by his investiga
tions upon cross-pollination. The growth of the pollen on the
stigma of the flower results eventually in the production of seeds,

A wild orchid, a flower of th3 typ3 from
which Charles Darwin worked out his
theory of cross-pollination by insects.

INTERRELATIONS OF PLANTS AND ANIMALS 41

and thus new plants. Many species of flowers are self-pollinated
and do not do so well in seed production if cross-pollinated, but
Charles Darwin found that some flowers which were self-pollinated
did not produce so many seeds, and that the plants which grew from
their seeds were smaller and weaker than plants from seeds pro
duced by cross-pollinated flowers of the same kind. He also found
that plants grown from cross-pollinated seeds tended to vary more
than those grown from self-pollinated seed. This has an important
bearing, as we shall see later, in the production of new varieties
of plants. Microscopic examination of the stigma at the time of
pollination also shows that the pollen from another flower usually
germinates before the pollen which has fallen from the anthers of
the same flower. This latter fact alone in most cases renders it
unlikely for a flower to produce seeds by its own pollen. Darwin
worked for years on the pollination of many insect-visited flowers,
and discovered in almost every case that showy, sweet-scented,
or otherwise attractive flowers were adapted or fitted to be cross-
pollinated by insects. He also found that, in the case of flowers
that were inconspicuous in appearance, often a compensation
appeared in the odor which rendered them attractive to certain
insects. The so-called carrion flowers, pollinated by flies, are
examples, the odor in this case being like decayed flesh. Other
flowers open at night, are white, and provided with a powerful
scent. Thus they attract night-flying moths and other insects.

Other Examples of Mutual Aid between Flowers and Insects. -
Many other examples of adaptations to secure cross-pollination
by means of the visits of insects might be given. The mountain
laurel, which makes our hillsides so beautiful in late spring, shows
a remarkable adaptation in having the anthers of the stamens
caught in little pockets of the corolla. The weight of the visiting
insect on the corolla releases the anther from the pocket in which
it rests so that it springs up, dusting the body of the visitor with
pollen.

In some flowers, as shown by the primroses or primula of our
hothouses, the stamens and pistils are of different lengths in different
flowers. Short styles and long or high-placed filaments are found
in one flower, and long styles with short or low-placed filaments

42 INTERRELATIONS OF PLANTS AND ANIMALS

in the other. Pollination will be effected only when some of the
pollen from a low-placed anther reaches the stigma of a short-
styled flower, or when the pollen from a high anther is placed upon

a long-styled pistil.
There are, as in the
case of the loosestrife,
flowers having pistils
and stamens of three
lengths. Pollen only
grows on pistils of the
same length as the
stamens from which it

The condition of stamens and pistils on the spiked
loosestrife (Lythrum salicarid).

came.

The milkweed or

butterfly weed already
mentioned is another example of a flower adapted to insect pol
lination. 1

A very remarkable instance of insect help is found in the polli
nation of the yucca, a semitropical lily
which lives in deserts (to be seen in
most botanic gardens). In this flower
the stigmatic surface is above the
anther, and the pollen is sticky and
cannot be transferred except by insect
aid. This is accomplished in a re
markable manner. A little moth,
called the pronuba, after gathering
pollen from an anther, deposits an egg-
in the ovary of the pistil, and then
rubs its load of pollen over the stigma
of the flower. The young hatch out
and feed on the young seeds which have grown because of the
pollen placed on the stigma by the mother. The baby cater-

1 For an excellent account of cross-pollination of thii flower, the reader is re
ferred to W. C. Stevens, Introduction to Botany. Orchids are well known to botan
ists as showing some very wonderful adaptations. A classic easily read is Darwin,
On the Fertilization of Orchids.

The pronuba moth within the
yucca flower.

INTERRELATIONS OF PLANTS AND ANIMALS 43

nating the pistil
of the yucca.

pillars eat some of the devel
oping seeds and later bore
out of the seed pod and
escape to the ground, leav
ing the plant to develop
the remaining seeds without
further molestation.

The fig insect (Blastophaga
grossorum) is another mem
ber of the insect tribe that
is of considerable economic
importance. It is only in The pronuba polli
recent years that the fruit
growers of California have
discovered that the fertilization of the female

Pod of yucca showing .

where the young pro- flowers is brought about by a gallfly which

nubas escaped. bores into the young fruit. By importing

the gallflies it has been possible to grow figs where for many
years it was believed that the climate prevented figs from
ripening.

Other Flower Visitors. Other insects besides those already
mentioned are pollen carriers for flowers. Among the most use
ful are moths and butterflies. Projecting from each side of the
head of a butterfly is a fluffy structure, the palp. This collects
and carries a large amount
of pollen, which is deposited
upon the stigmas of other
flowers when the butterfly
pushes its head down into
the flower tube after nectar.
The scales and hairs on the
wings, legs, and body also
carry pollen.

Flies and some other in
sects are agents in cross-

pollination. Humming birds A humming Mrd about to crosa . pollinate
are also active agents in a lily.

44 INTERRELATIONS OF PLANTS AND ANIMALS

some flowers. Snails are said in rare instances to carry pollen.
Man and the domesticated animals undoubtedly frequently
pollinate flowers by brushing past them through the fields.

Pollination by the Wind. Not all flowers are dependent upon
insects or other animals for cross-pollination. Many of the earliest
of spring flowers appear almost before the insects do. Such flowers
are dependent upon the wind for carrying pollen from the stamens

A cornfield showing staminate and pistillate flowers, the latter having become
grains of corn. An ear of corn is a bunch of ripened fruits.

of one flower to the pistil of another. Most of our common trees,
oak, poplar, maple, and others, are cross-pollinated almost en
tirely by the wind.

Flowers pollinated by the wind are generally inconspicuous
and often lack a corolla. The anthers are exposed to the wind
and provided with much pollen, while the surface of the stigma
may be long and feathery. Such flowers may also lack odor, nectar,
and bright color. Can you tell why ?

Imperfect Flowers. Some flowers, the wind-pollinated ones
in particular, are imperfect; that is, they lack either stamens

INTERRELATIONS OF PLANTS AND ANIMALS 45

or pistils. Again, in some cases, imperfect flowers having stamens
only are alone found on one plant, while those flowers having
pistils only are found on another plant of the same kind. In such
flowers, cross-pollination must of necessity follow. Many of our
common trees are examples.

Other Cases. The stamens and pistil ripen at different times
in some flowers. The "Lady Washington" geranium, a common

The flower of " Lady Washington " geranium, in which stamens and pistil ripen
at different times, thus insuring cross-pollination. A, flower with ripe
stamens; B, flower with stamens withered and ripe pistil.

house plant, shows this condition. Here also cross-pollination must
take place if seeds are to be formed.

Summary. If we now collect our observations upon flowers
with a view to making a summary of the different devices flowers
have assumed to prevent self-pollination and to secure cross-
pollination, we find that they are as follows :

(1) The stamens and pistils may be found in separate flowers }
either on the same or on different plants.

(2) The stamens may produce pollen before the pistil' is ready to
receive it, or vice versa.

(3) The stamens and pistils may be so placed with reference to each
other that pollination can be brought about only by outside assistance.

46 INTERRELATIONS OF PLANTS AND ANIMALS

Artificial Cross-pollination and its Practical Benefits to Man.
Artificial cross-pollination is practiced by plant breeders and can
easily be tried in the laboratory or at home. First the anthers
must be carefully removed from the bud of the flower so as to elim
inate all possibility of self-pollination. The flower must then be
covered so as to prevent access of pollen from without ; when the
ovary is sufficiently developed, pollen from another flower, having
the characters desired, is placed on the stigma and the flower
again covered to prevent any other pollen reaching the flower.
The seeds from this flower when planted may give rise to plants
with the best characters of each of the plants which contributed
to the making of the seeds.

REFERENCE BOOKS

ELEMENTARY

Hunter, Laboratory Problems in Civic Biology. American Book Company.
Andrews, A Practical Course in Botany, pages 214-249. American Book Company.
Atkinson, First Studies of Plant Life, Chaps. XXV-XXVI. Ginn and Company.
Coulter, Plant Life and Plant Uses, pagas 301-322. American Book Company.
Dana, Plants and their Children, pages 187-255. American Book Company.
Lubbock, Flowers, Fruits, and Leaves, Part I. The Macmillan Company.
Needham, General Biology, pages 1-50. The Cornstalk Publishing Company.
Newell, A Reader in Botany, Part II, pages 196. Ginn and Company.
Sharpe, A Laboratory Manual in Biology, pages 43-48. American Book Company.

ADVANCED

Bailey, Plant Breeding. The Macmillan Company.

Campbell, Lectures on the Evolution of Plants. The Macmillan Company.

Coulter, Barnes, and Cowles, A Textbook of Botany, Part II. American Book Com
pany.

Darwin, Different Forms of Floivers on Plants of the Same Species. D. Appleton
and Company.

Darwin, Fertilization in the Vegetable Kingdom, Chaps. I and II. D. Appleton
and Company.

Darwin, Orchids Fertilized by Insects. D. Appleton and Company.

Lubbock, British Wild Flowers. The Macmillan Company.

Miiller, The Fertilization of Flowers. The Macmillan Company.

IV. THE FUNCTIONS AND COMPOSITION OF LIVING

THINGS

Problems. To discover the functions of living matter.
(a} In a living plant.
(#) In a living animal.

LABORATORY SUGGESTIONS

Laboratory study of a living plant. Any whole plant may be used ; a
weed is preferable.

Laboratory demonstration or home study. The functions of a living
animal.

Demonstration. The growth of pollen tubes.

Laboratory exercise. The growth of the mature ovary into the fruit,
e.g. bean or pea pod.

A Living Plant and a Living Animal Compared. A walk into
the fields or any vacant lot on a day in the early fall will give us
first-hand acquaintance with many common plants which, be
cause of their ability to grow under somewhat unfavorable condi
tions, are called weeds. Such plants the dandelion, butter and
eggs, the shepherd's purse are particularly well fitted by na
ture to produce many of their kind, and by this means drive out
other plants which cannot do this so well. On these or other
plants we find feeding several kinds of animals, usually insects.

If we attempt to compare, for example, a grasshopper with the
plant on which it feeds, we see several points of likeness and dif
ference at once. Both plant and insect are made up of parts,
each of which, as the stem of the plant or the leg of the insect,
appears to be distinct, but which is a part of the whole living plant
or animal. Each part of the living plant or animal which has a
separate work to do is called an organ. Thus plants and
animals are spoken of as living organisms.

FUNCTIONS OF LIVING THINGS

Functions of the Parts of a Plant. We are all familiar with
the parts of a plant, the root, stem, leaves, flowers, and fruit.
But we may not know so much about their uses to the plant. Each
of these structures differs from every other
part, and each has a separate work or func
tion to perform for the plant. The root
holds the plant firmly in the ground and takes
in water and mineral matter from the soil;
the stem holds the leaves up to the light and
acts as a pathway for fluids between the root
and leaves; the leaves, under certain condi
tions, manufacture food for the plant and
breathe; the flowers form the fruits; the fruits
hold the seeds, which in turn hold young
plants which are capable of reproducing adult
plants of the same kind.

The Functions of an Animal. As we
have already seen, the grasshopper has a
head, a jointed body composed of a middle
and a hind part, three pairs of jointed legs,
and two pairs of wings. Obviously, the
wings and legs are used for movement ; a
careful watching of the hind part of the
animal shows us that breathing movements
are taking place ; a bit of grass placed before it may be eaten,
the tiny black jaws biting little pieces out of the grass. If
disturbed, the insect hops away, and if we try to get it, it jumps
or flies away, evidently seeing us before we can grasp it. Hundreds
of little grasshoppers on the grass indicate that the grasshopper
can reproduce its own kind, but in other respects the animal seems
quite unlike the plant. The animal moves, breathes, feeds, and
has sensation, while apparently the plant does none of these. It
will be the purpose of later chapters to prove that the functions
of plants and animals are in many respects similar and that both
plants and animals breathe, feed, and reproduce.

Organs. If we look carefully at the organ of a plant called a
leaf, we find that the materials of which it is composed do not ap-

A weed notice the un
favorable environment.

FUNCTIONS OF LIVING THINGS

pear to be everywhere the same.
The leaf is much thinner and
more delicate in some parts
than in others. Holding the
flat, expanded blade away from
the branch is a little stalk,
which extends into the blade of
the leaf. Here it splits up into
a network of tiny " veins "
which evidently form a frame
work for the flat blade some
what as the sticks of a kite
hold the paper in place. If we
examine under the compound
microscope a thin section cut
across the leaf, we shall find
that the veins as well as the

Section through the blade of a leaf, e,
cells of the upper surface ; d, cells of the
lower surface ; i, air spaces in the leaf ;
v, vein in cross sections ; p, green cells.

other parts are made up of many tiny boxlike units of various
sizes and shapes. These smallest units of building material of the

plant or animal disclosed by the
compound microscope are called
cells. The organs of a plant or
animal are built of these tiny
structures.

Tissues. 1 -- The cells which
form certain parts of the veins,
the flat blade, or other portions

Several cells of Elodea, a water plant.

chl, chlorophyll bodies; c.s., cell sap; of the plant, are often found in

c.w., cell wall; n., nucleus ; p. proto- groups or collections, the Cells
plasm. The arrows show the direc- & *^

tion of the protoplasmic movement. of which are more or less alike

1 To the Teacher. Any simple plant or animal tissue can be used to demon
strate the cell. Epidermal cells may be stripped from the body of the frog or
obtained by scraping the inside of one's mouth. The thin skin from an onion
stained with tincture of iodine shows well, as do thin sections of a young stem, as
the bean or pea. One of the best places to study a tissue and the cells of which
it is composed is in the leaf of a green water plant, Elodea. In this plant the cells
are large, and not only their outline, but the movement of the living matter within
the cells, may easily be seen, and the parts described in the next paragraph can
be demonstrated.

HUNTER, CIV. BI. 4

FUNCTIONS OF LIVING THINGS

A cell. ch.,

somes ; c.w., cell wall ;
n., nucleus ; p., proto-

in size and shape. Such a collection of cells is called a tissue.
Examples of tissues are the cells covering the outside of the human
body, the muscle cells, which collectively allow of movement, bony
tissues which form the framework to which the muscles are at
tached, and many others.

Cells. A cell may be defined as a tiny mass of living matter
containing a nucleus, either living alone or forming a unit of
the building material of a living thing. The
living matter of which all cells are formed is
known as protoplasm (formed from two Greek
words meaning first form). If we examine
under a compound microscope a small bit of
the water plant Elodea, we see a number of
structures resembling bricks in a wall. Each
" brick, 7 ' however, is really a plant cell
c j) m ; bounded by a thin wall. If we look carefully,
we can see that the material inside of this wall
plasm * is slowly moving and is carrying around in its

substance a number of little green bodies. This moving substance
is living matter, the protoplasm of the cell. The green bodies
(the chlorophyll bodies) we shall learn more about later ; they are
found only in plant cells. All plant and animal cells appear
to be alike in the fact that every living cell possesses a structure
known as the nucleus (pi. nuclei), which is found within the body
of the cell. This nucleus is not easy to find in the cells of Elodea.
Within the nucleus of all cells are found certain bodies called
chromosomes. These chromosomes in a given plant or animal are
always constant in number. These chromosomes are supposed to
be the bearers of the qualities which we believe can be handed
down from plant to plant and from animal to animal, in other
words, the inheritable qualities which make the offspring like its
parents.

How Cells form Others. Cells grow to a certain size and then
split into two new cells. In this process, which is of very great
importance in the growth of both plants and animals, the nucleus
divides first. The chromosomes also divide, each splitting length
wise and the parts going in equal numbers to each of the two cells

FUNCTIONS OF LIVING THINGS

formed from the old cell. In this way the matter in the chromosomes
is divided equally between the two new cells. Then the rest of
the protoplasm separates, and two new cells are formed. This
process is known as fis
sion. It is the usual
method of growth found
in the tissues of plants

and animals.

Cells of Various Sizes
and Shapes. - - Plant
cells and animal cells are
of very diverse shapes
and sizes. There are
cells so large that they J> f

Can easily be seen with Stages in the division of one cell to form two.
the Unaided eve * for Which part of the cell divides first ? What seems
y ' to become of the chromosomes ?

example, the root hairs

of plants and eggs of some animals. On the other hand, cells
may be so minute, as in the case of the plant cells named bacteria,
that several million might be present in a few drops of milk. The
forms of cells may be extremely varied in different tissues ; they
may assume the form of cubes, columns, spheres, flat plates, or
may be extremely irregular in shape. One kind of tissue cell,
found in man, has a body so small as to be quite invisible to the
naked eye, although it has a prolongation several feet in length.
Such are some of the cells of the nervous system of man and other
large animals, as the ox, elephant, and whale.

Varying Sizes of Living Things. Plant cells and animal cells
may live alone, or they may form collections of cells. Some
plants are so simple in structure as to be formed of only one kind
of cells. Usually living organisms are composed of several groups
of different kinds of cells. It is only necessary to call attention
to the fact that such collections of cells may form organisms so
tiny as to be barely visible to the eye ; as, for instance, some of the
small flowerless plants or many of the tiny animals living in fresh
water or salt water. On the other hand, among animals, the bulk
of the elephant and whale, and among plants the big trees of Cali-

52 FUNCTIONS OF LIVING THINGS

fornia, stand out as notable examples. The large plants and ani
mals are made up of more, not necessarily larger, cells.

What Protoplasm can Do. It responds to influences or stimu
lation from without its- own substance. Both plants and animals
are sensitive to touch or stimulation by light, heat or cold, certain
chemical substances, gravity, and electricity. Green plants turn
toward the source of light. Some animals are attracted to light
and others repelled by it; the earthworm is an example of the
latter. Protoplasm is thus said to be irritable.

Protoplasm has the power to contract and to move. Muscular
movement is a familiar instance of this power. Movement
may also take place in plants. Some plants fold up their leaves
at night ; others, like the sensitive plant, fold their leaflets when
touched.

Protoplasm can form new living matter out of food. To do this,
food materials must be absorbed into the cells of the living
organism. To make protoplasm, it is evident that the same chem
ical elements must enter into the composition of the food sub
stances as are found in living matter. The simplest plants and
animals have this wonderful power as certainly developed as the
most complex forms of life.

Protoplasm, be it in plant or animal, breathes and throws off waste
materials. When a living thing does work oxygen unites with food
in the body ; the food is burned or oxidized and work is done by
means of the energy released from the food. The waste materials
are excreted or passed out. Plants and animals alike pass off the
carbon dioxide which results from the oxidation of food and of
parts of their own bodies. Animals eliminate wastes containing
nitrogen through the skin and tho kidney s%

Protoplasm can reproduce, that is, form other matier like itself.
New. plants are constantly appearing to take the places of those
that die. The supply of living things upon the earth is not de
creasing; reproduction is constantly taking place. In a general
way it is possible to say that plants and animals reproduce in a
very similar manner.

The Importance of Reproduction. Reproduction is the final
process that plants and animals are called upon to perform.

FUNCTIONS OF LIVING THINGS

Without the formation of new living things no progress would be
possible on the earth. We have found that insects help flowering
plants in this process. Let us now see exactly what happens
when pollen is placed by the bee on the stigma of another flower
of the same kind. To understand this process of reproduction in
flowers, we must first study carefully pollen grains from the anther
of some growing flower.

Pollen. Pollen grains of various flowers, when seen under the
microscope, differ greatly in form and appearance. Some are rela
tively large, some small, some rough, others smooth, some spherical,

Pollen grains of different shapes and sizes.

and others angular. They all agree, however, in having a thick
wall, with a thin membrane under it, the whole inclosing a mass
of protoplasm. At an early stage the pollen grain contains but a
single cell. A little later, however, two nuclei may be found in the
protoplasm. Hence we know that at least two cells exist there, one
of which is called the sperm cell ; its nucleus is the sperm nucleus.
Growth of Pollen Grains. Under certain conditions a pollen
grain will grow or germinate. This
growth can be artificially produced in
the laboratory by sprinkling pollen
from well-opened flowers of sweet pea
or nasturtium on a solution of 15
parts of sugar to 100 of water. Left
for a few hours in a warm and moist
place and then examined under the
microscope, the grains of pollen will
be found to have germinated, a long,
threadlike mass of protoplasm grow-
ing from it into the sugar solution. this stage of its growth.

FUNCTIONS OF LIVING THINGS

Three stages in the germination of the pollen
grain. The nuclei in the tube in (3) are
the sperm nuclei. Drawn under the com
pound microscope.

The presence of this sugar
solution was sufficient to
induce growth. When the
pollen grain germinates,
the nuclei enter the thread
like growth (this growth is
called the pollen tube ; see
Figure) . One of the nuclei
which grows into the pollen
tube is known as the sperm
nucleus.

Fertilization of the
Flower. If we cut the
pistil of a large flower (as a

lily) lengthwise, we notice that the style appears to be composed

of rather spongy material in the in
terior; the ovary is hollow and is

seen to contain a number of rounded

structures which appear to grow out

from the wall of the ovary. These

are the ovules. The ovules, under

certain conditions, will become seeds.

An explanation of these conditions

may be had if we examine, under

the microscope, a very thin section

of a pistil, on which pollen has be
gun to germinate. The central part

of the style is found to be either

hollow or composed of a soft tissue

through which the pollen tube can

easily grow. Upon germination,

the 'pollen tube grOWS downward Fertilization of the ovule.

through the spongy center of the
style, follows the path of least resist
ance to the space within the ovary,
and there enters the ovule. It is
believed that some chemical influ-

A flower

cut down lengthwise (only one
side shown). The pollen tube is
seen entering the ovule, a, an
ther ; /, filament ; pg, pollen grain;
s, stigmatic surface ; pt , pollen
tube ; st, style ; o, ovary ; m, micro-
pyle; sp, space within ovary;
e, egg cell ; P, petal ; *S, sepal.

FUNCTIONS OF LIVING THINGS

ence thus attracts the pollen tube. When it reaches the ovary,
the sperm cell penetrates an ovule by making its way through a
little hole called the micropyle. It then grows toward a clear
bit of protoplasm known as the embryo sac. The embryo sac is
an ovoid space, microscopic in size, filled with semifluid protoplasm
containing several nuclei. (See Figure.) One of the nuclei, with
the protoplasm immediately surrounding it, is called the egg cell. It
is this cell that the sperm nucleus of the pollen tube grows to
ward ; ultimately the sperm nucleus reaches the egg nucleus and
unites with it. The two nuclei, after coming together, unite to form
a single cell. This process is known as fertilization. This single
cell formed by the union of the pollen tube cell or sperm and the
egg cell is now called a fertilized egg.

Development of Ovule into Seed. The primary reason for
the existence of a flower is that it may produce seeds from which future
plants will grow. After fertilization the ovule grows into a seed.
The first beginning of the growth of the seed takes place at the
moment of fertilization. From that time on there is a growth
of the fertilized egg within the ovule which makes a baby plant
called the embryo. The embryo will give rise to the adult plant.

A Typical Fruit, the Pea or Bean Pod. -
If a withered flower of any one of the pea or
bean family is examined carefully, it will be
found that the pistil of the flower continues to
grow after the rest of the flower withers. If
we remove the pistil from such a flower and
examine it carefully, we find that it is the
ovary that has enlarged. The space within
the ovary has become nearly filled with a
number of nearly ovoid bodies, attached
along one edge of the inner wall. These we
recognize as the young seeds.

The pod of a bean, pea, or locust illustrates
well the growth from the flower. The pod,
which is in reality a ripened ovary with other
parts of the pistil attached to it, is considered
as a fruit. By definition, a fruit is a ripened

The fruit of the locust,
a bean-like fruit.
p, the attachment
to the placenta; s,
the stigma.

FUNCTIONS OF LIVING THINGS

ovary and its contents together with any parts of the flower that may
be attached to it. The chief use of the fruit to the flower is to
hold and to protect the seeds ; it may ultimately distribute them
where they can reproduce young plants.

The Necessity of Fruit and Seed Dispersal to a Plant. We
have seen that the chief reason for flowers, from the plant's stand
point, is to produce fruits which contain seeds. Reproduction
and the ultimate scattering of fruits and seeds are absolutely neces-

The development of an apple. Notice that in this fruit additional parts besides
the ovary (o) become part of the fruit. Certain outer parts of the flower, the
sepals (s) and receptacle, become the fleshy part of the fruit, while the ovary
becomes the core. Stages numbered 1 to 7 are in the order of development.

sary in order that colonies of plants may reach new localities. It
is evident that plants best fitted to scatter their seeds, or place
fruits containing the seeds some little distance from the parent
plants, are the ones which will spread most rapidly. A plant, if
it is to advance into new territory, must get its seeds there first.
Plants which are best fitted to do this are the most widely dis
tributed on the earth.

How Seeds and Fruits are Scattered. Seed dispersal is accom
plished in many different ways. Some plants produce enormous
numbers of seeds which may or may not have special devices to
aid in their scattering. Most weeds are thus started " in pastures

FUNCTIONS OF LIVING THINGS 57

new." Some prolific plants, like the milkweed, have seeds with a
little tuft of hairlike down which allows them to be carried by the
wind. Others, as the omnipresent dandelion, have their fruits
provided with a similar structure, the pappus. Some plants, as
the burdock and clotbur, have fruits provided with tiny hooks
which stick to the hair of animals, thus proving a means of trans
portation. Most fleshy fruits contain indigestible seeds, so that
when the fruits are eaten by animals the seeds are passed off from
the body unharmed and may, if favorably placed, grow. Nuts of
various kinds are often carried off by animals, buried, and for
gotten, to grow later. Such are a few of the ways in which seeds
are scattered. All other things being equal, the plants best
equipped to scatter seeds or fruits are those which will drive out
other plants in a given locality. Because of their adaptations
they are likely to be very numerous, and when unfavorable con
ditions come, for that reason, if for no other, are likely to survive.
Such plants are best exemplified in the weeds of the grassplots
and gardens.

REFERENCE BOOKS

ELEMENTARY

Hunter, Laboratory Problems in Civic Biology. American Book Company.
Andrews, A Practical Course in Botany, pages 250-270. American Book Company.
Atkinson, First Studies of Plant Life, Chaps. XXV-XXVI. Ginn and Company.
Bailey, Lessons with Plants, Part III, pages 131-250. The Macmillan Company.
Coulter, Plant Life and Plant Uses. American Book Company.
Dana, Plants and their Children, pages 187-255. American Book Company.
Lubbock, Flowers, Fruit, and Leaves, Part I. The Macmillan Company.
Newell, A Reader in Botany, Part II, pages 1-96. Ginn and Company.

ADVANCED

Bailey, Plant Breeding. The Macmillan Company.

Campbell, Lectures on the Evolution of Plants. The Macmillan Company.

Coulter, Barnes, and Cowles, A Textbook of Botany, Part II. American Book

Company.

Darwin, Different Forms of Flowers on Plants of the Same Species. Appleton.
Darwin, Fertilization in the Vegetable Kingdom, Chaps. I and II. Appleton.
Darwin, Orchids Fertilized by Insects. D. Appleton and Company.
Miiller, The Fertilization of Flowers. The Macmillan Company.

V. PLANT GROWTH AND NUTRITION. CAUSES OF

GROWTH

Problem. What causes a young plant to grow ?

(a} The relation of the young plant to its food supply.

(#) The outside conditions necessary for germination.

(d) How a plant or animal is able to use its food supply.

(e} How a plant or animal prepares food to use in various
parts of the body.

LABORATORY SUGGESTIONS

Laboratory exercise. Examination of bean in pod. Examination and
identification of parts of bean seed.

Laboratory demonstration. Tests for the nutrients : starch, fats or
oils, protein.

Laboratory demonstration. Proof that such foods exist in bean.

Home work. Test of various common foods for nutrients. Tabulate
results.

Extra home work by selected pupils. Factors necessary for germina
tion of bean. Demonstration of experiments to class.

Demonstration. Oxidation of candle in closed jar. Test with lime
water for products of oxidation.

Demonstration. Proof that materials are oxidized within the human
body.

Demonstration. Oxidation takes place in growing seeds. Test for
oxidation products. Oxygen necessary for germination.

Laboratory exercise. Examination of corn on cob, the corn grain,
longitudinal sections of corn grain stained with iodine to show that embryo
is distinct from food supply.

Demonstration. Test for grape sugar.

Demonstration. Grape sugar present in growing corn grain.

Demonstration. The action of diastase on starch. Conditions neces
sary for action of diastase.

What makes a Seed Grow. The general problem of the pages
that follow will be to explain how the baby plant, or embryo,

PLANT GROWTH AND NUTRITION

formed in the seed as the result of the fertilization of the egg cell,
is able to grow into an adult plant. Two sets of factors are neces
sary for its growth : first, the presence of food to give the young
plant a start ; second, certain stimulating factors outside the young
plant, such as water and heat.

If we open a bean pod, we find the seeds lying along one edge of
the pod, each attached by a little stalk to the inner wall of the
ovary. If we pull a single bean from its attachment, we find that
the stalk leaves a scar on the
coat of the bean ; this scar is
called the hilum. The tiny
hole near the hilum is called
the micropyle. Turn back to
the figure (page 54) showing
the ovule in the ovary. Find
there the little hole through
which the pollen tube reached
the embryo sac. This hole is
identical with the micropyle
in the seed. The thick outer
coat (the testa) is easily re
moved from a soaked bean,
the delicate coat under it
easily escaping notice. The
seed separates into two parts ;
these are called the cotyledons.
If you pull apart the coty
ledons very carefully, you find certain other structures between
them. The rodlike part is called the hypocotyl (meaning under
the cotyledons). This will later form the root (and part of the
stem) of the young bean plant. The first true leaves, very tiny
structures, are folded together between the cotyledons. That
part of the plant abo/e the cotyledons is known as the plumule
or epicotyl (meaning above the cotyledons). All the parts of the
seed within the seed coats together form the embryo or young
plant. A bean seed contains, then, a tiny plant protected by a
tough coat.

Three views of a kidney bean, the lower
one having one cotyledon removed to
show the hypocotyl and plumule.

60 PLANT GROWTH AND NUTRITION

Food in the Cotyledons. The problem now before us is to find
out how the embryo of the bean is adapted to grow into an adult
plant. Up to this stage of its existence it has had the advantage
of food and protection from the parent plant. Now it must begin
the battle of life alone. We shall find in all our work with plants
and animals that the problem of food supply is always the most
important problem to be solved by the growing organism. Let
us see if the embryo is able to get a start in life (which many
animals get in the egg) from food provided for it within its own
body.

Organic Nutrients. Organic foods (those which come from
living sources) are made up of two kinds of substances, the nutri
ents or food substances and wastes or refuse. An egg, for example,
contains the white and the yolk, composed of nutrients, and the
shell, which is waste. The organic nutrients are classed in three
groups.

Carbohydrates, foods which contain carbon, hydrogen, and
oxygen in a certain fixed proportion (C 6 Hi O 5 is an example).
They are the simplest of these very complex chemical compounds
we call organic nutrients. Starch and sugar
are common examples of carbohydrates.

Fats and Oils. These foods are also com
posed of carbon, hydrogen, and oxygen in a
proportion which enables them to unite
readily with oxygen.

Proteins. A third group of organic foods,
Starch grains in the cells proteins, are the most complex of all in

of a potato tuber. , . . . . , i_ i

their composition, and have, besides carbon,
oxygen, and hydrogen, the element nitrogen and minute quantities
of other elements.

Test for Starch. If we boil water with a piece of laundry starch
in a test tube, then cool it and add to the mixture two or three
drops of iodine solution, 1 we find that the mixture in the test tube

1 Iodine solution is made by simply adding a few crystals of the element iodine
to 95 per cent alcohol ; or, better, take by weight 1 gram of iodine crystals, f gram
of iodide of potassium, and dilute to a dark brown color in weak alcohol (35 per
cent) or distilled water.

PLANT GROWTH AND NUTRITION

Test for starch.

turns purple or deep blue. It has been discovered by experiment

that starch, and no other known substance, will be turned purple or

dark blue by iodine. Therefore, iodine

solution has come to be used as a test

for the presence of starch.

Starch in the Bean. If we mash

up a little piece of a bean cotyledon

which has been previously soaked in

water, and test for starch with iodine

solution, the characteristic blue-black

color appears, showing the presence of

the starch. If a little of the stained

material is mounted in water on a glass

slide under the compound microscope,

you will find that the starch is in the

form of little ovoid bodies called starch grains. The starch grains

and other food products are made use of by the growing plant.

Test for Oils. If the substance
believed to contain oil is rubbed on
brown paper or is placed on paper and
then heated in an oven, the presence
of oil will be known by a translucent
spot on the paper.

Protein in the Bean. Another
nutrient present in the bean cotyledon
is protein. Several tests are used to
detect the presence of this nutrient.
The following is one of the best
known :

Place in a test tube the substance
to be tested; for example, a bit of
hard-boiled egg. Pour over it a little
strong (60 per cent) nitric acid and heat
gently. Note the color that appears

a lemon yellow. If the egg is washed in water and a little

ammonium hydrate added, the color changes to a deep orange,

showing that a protein is present.

Test for protein.

PLANT GROWTH AND NUTRITION

If the protein is in a liquid state, its presence may be proved
by heating, for when it coagulates or thickens, as does the white
of an egg when boiled, protein in the form of an albumin is present.

Another characteristic protein test easily made at home is
burning the substance. If it burns with the odor of burning feath
ers or leather, then protein forms part of its composition. 1

A test of the cotyledon of a bean for protein food with nitric
acid and ammonium hydrate shows us the presence of this food.
Beans are found by actual test to contain about 23 per cent of
protein, 59 per cent of carbohydrates, and about 2 per cent oils.
The young plant within a pea or bean is thus shown to be well
supplied with nourishment until it is able to take care of itself.
In this respect it is somewhat like a young animal within the egg,
a bird or fish, for example.

Beans and Peas as Food for Man. So much food is stored in
legumes (as beans and peas) that man has come to consider them
a very valuable and cheap source of food. Study carefully the
following table :

NUTRIENTS FURNISHED FOR TEN CENTS IN BEANS AND PEAS AT
CERTAIN PRICES PER POUND

PRICES

TEN

CENTS w

ILL PAY F(

FOOD MATERIALS AS PURCHASED

PER

POUND

Total
Food
Material

Proteid

Fat

Carbo
hydrates

Kidney beans dried

Cents

Pounds

2 00

Pounds

1 19

Ijinut beans fresh shelled

1 9^

Lima beans, dried

1 67

1 10

String beans, fresh, 30 cents per
peck .

333

Beans, baked, canned ....
Lentils, dried
Peas, green, in pod, 30 cents per
peck .

5
10

2.00
1.00

3 33

.14
.26

.05
.01

.39
.59

Peas, dried

2 50

1 55

1 Other tests somewhat more reliable, but much more delicate, are the biuret
test and test with Millon's reagent.

PLANT GROWTH AND NUTRITION

Germination of the Bean. If dry seeds are planted in sawdust
or earth, they will not grow. A moderate supply of water must be

A series of early stages in the germination of the kidney bean.

given to them. If seeds were to be kept in a freezing tempera
ture or at a very high temperature, no growth would take place.
A moderate temperature and
a moderate water supply are
most favorable for their de
velopment.

If some beans were planted
so that we might make a record
of their growth, we would find
the first signs of germination
to be the breaking of the testa
and the pushing outward of
the hypocotyl to form the first
root. A little later the hypo
cotyl begins to curve down
ward. A later stage shows
the hypocotyl lifting the coty
ledon upward. In consequence
the hypocotyl forms an arch,
dragging after it the bulky

. i i r Bean seedlings. The older seedlings at

cotyledons^ The stem, as the left ha * e used up all of the food
soon as it is released from the supply in the cotyledons.

64 PLANT GROWTH AND NUTRITION

ground, straightens out. From between the cotyledons the bud-
like plumule or epicotyl grows upward, forming the first true
leaves and all of the stem above the cotyledons. As growth con
tinues, we notice that the cotyledons become smaller and smaller,
until their food contents are completely absorbed into the young
plant. The young plant is now able to care for itself and may
be said to have passed through the stages of germination.

What makes an Engine Go. If we examine the sawdust or
soil in which the seeds are growing, we find it forced up by the
growing seed. Evidently work was done ; in other words, energy
was released by the seeds. A familiar example of release of
energy is seen in an engine. Coal is placed in the firebox and
lighted, the lower door of the furnace is then opened so as to make
a draft of air which will reach the coal. You know the result.
The coal burns, heat is given off, causing the water in the boiler
to make steam, the engine wheels to turn,
and work to be done. Let us see what
happens from the chemical standpoint.

Coal, Organic Matter. Coal is made
largely from dead plants, long since pressed
into its present hard form. It contains a
large amount of a chemical element called
carbon, the presence of which is character
istic of all organic material.

Oxidation, its Results. When things con
taining carbon are lighted, they burn. If we
place a lighted candle which contains carbon
in a closed glass jar, the candle soon goes out.
The limewater test. The If we then carefully test the air in the jar
tube at the right shows with a substance known as limewater, 1 the
dtxide. Ct the Carb n latter > wh en shaken up with the air in the
jar, turns milky. This test proves the pres
ence in the jar of a gas, known as carbon dioxide. This gas is
formed by the carbon of the candle uniting with the oxygen in

1 Limewater can be made by shaking up a piece of quicklime the size of your
fist in about two quarts of water. Filter or strain the limewater into bottles and
it is ready for use.

PLANT GROWTH AND NUTRITION

the air. When the oxygen of the air in the jar was used up,
the flame went out, showing that oxygen is necessary to make a
thing burn. This uniting of
oxygen with some other sub
stance is called oxidation.

Oxidation possible without a
Flame. But a flame is not
necessary for oxidation. Iron,
if left in a damp place, becomes
rusty. A union between the
oxygen in the water or air and

the iron makes what is known Diagram to show that when a piece of

" f rmS "*" ^

as iron oxide or rust. This is
an example of slow oxidation.

Oxidation in our Bodies. If we expel the air from our lungs
through a tube into a bottle of limewater, we notice the lime-
water becomes milky. Evidently carbon dioxide is formed in our
own bodies and oxidation takes place there. Is it fair to believe
that the heat of our body (for example, 98.6 Fahrenheit under the
tongue) is due to oxidation within the body, and that the work
we do results from this chemical process. If so, what is oxidized?

Energy comes from Foods. From the foregoing experiment
it is evident that food is oxidized within the human body to re
lease energy for our daily work. Is it not logical to suppose that
all living things, both plant and animal, release energy as the re
sult of oxidation of foods within their cells ? Let us see if this is
true in the case of the pea.

Food oxidized in Germinating Seeds. If we take equal
numbers of soaked peas, placed in two bottles, one tightly stop
pered, the other having no stopper, both bottles being exposed to
identical conditions of light, temperature, and moisture, we find
that the seeds in both bottles start to germinate, but that those
in the closed bottle soon stop, while those in the open jar continue
to grow almost as well as similar seeds placed in an open dish would.

Why did not the seeds in the covered jar germinate? To
answer this question, let us carefully remove the stopper from the
stoppered jar and insert a lighted candle. The candle goes out

HUNTER, CIV. BI. 5

PLANT GROWTH AND NUTRITION

at once. The surer test of limewater shows the presence of car
bon dioxide in the jar. The carbon of the foodstuffs of the pea

united with the oxygen
of the air, forming car
bon dioxide. Growth
stopped as soon as the
oxygen was exhausted.
The presence of carbon
dioxide in the jar is an
indication that a very
important process which
we associate with animals
rather than plants, that
of respiration, is taking
place. The seed, in order
to release the energy
locked up in its food
supply, must have oxy-

gen, so that the oxida-

Experiment that shows the necessity for air in
germination.

tion of the food may take

place. Hence a constant supply of fresh air is an important factor
in germination. It is important that air should penetrate between
the grains of soil around a seed. The frequent stirring of the soil
enables the air to reach the seed. Air also acts
upon some materials in the soil and puts them
in a form that the germinating seed can use.
This necessity for oxygen shows us at least
one reason why the farmer plows and harrows
a field and one important use of the earthworm.
Explain.

Structure of a Grain of Corn. Examination
of a well-soaked grain of corn discloses a difference
in the two flat sides of the grain. A light-colored
area found on one surface marks the position of
the embryo; the rest of the grain contains the
food supply. The interesting thing to remember here is that the
food supply is outside of the embryo.

A grain of corn
cut lengthwise.
C, cotyledon ;
E, endosperm;
H, hypocotyl;
P, plumule.

PLANT GROWTH AND NUTRITION

A grain cut lengthwise perpendicular to the flat side and then
dipped in weak iodine shows two distinct parts, an area containing
considerable starch, the endosperm, and the embryo or young
plant. Careful inspection shows the hypo-
cotyl and plumule (the latter pointing toward
the free end of the grain) and a part surround
ing them, the single cotyledon (see Figure).
Here again we have an example of a fitting
for future needs, for in this fruit the one seed
has at hand all the food material necessary
for rapid growth, although the food is here
outside the embryo.

Endosperm the Food Supply of Corn.
We find that the one cotyledon of the corn
grain does not serve the same purpose to
the young plant as do the two cotyledons of
the bean. Although we find a little starch
in the corn cotyledon, still it is evident from
our tests that the endosperm is the chief source
of food supply. The study of a thin section
of the corn grain under the compound micro
scope shows us that the starch grains in the
endosperm are large and regular in size.
When the grain has begun to grow, examina
tion shows that the starch grains near the
edge of the cotyledon are much smaller and
quite irregular, having large holes in them.
We know that the germinating grain has a
much sweeter taste than that which is not
growing. This is noticed in sprouting barley
or malt. We shall later find that, in order
to make use of starchy food, a plant or animal
must in some manner change it over to sugar.
This change is necessary, because starch will
not dissolve in water, while sugar will; in this form substances
can pass from cell to cell in the plant and thus distribute the food
where it is needed.

Longitudinal section of
young ear of corn.
0, the fruits; S, the
stigmas ; SH, the
sheath-like leaves :
ST, the flower stalk.
(After Sargent.)

PLANT GROWTH AND NUTRITION

A Test for Grape Sugar. Place in a test tube the substance to
be tested and heat it in a little water so as to dissolve the sugar.

Add to the fluid twice its bulk of
Fehling's solution, 1 which has been
previously prepared. Heat the mix
ture, which should now have a blue
color, in the test tube. If grape sugar
is present in considerable quantity, the
contents of the tube will turn first a
greenish, then yellow, and finally a
brick-red color. Smaller amounts will
show less decided red. No other sub
stance than sugar will give this reac
tion. If Benedict's test * is used, a
colored precipitate will appear in the
test tube after boiling.

Starch changed to Grape Sugar in
the Corn. That starch is being
changed to grape sugar in the germi
nating corn grain can easily be shown if we cut lengthwise through
the embryos of half a dozen grains of corn that have just begun
to germinate, place them in a test tube with some Fehling's solu
tion, and heat almost to the boiling point. They will be found
to give a reaction showing the presence of sugar along the edge
of the cotyledon and between it and the endosperm.

Digestion. This change of starch to grape sugar in the corn
is a process of digestion. If you chew a bit of unsweetened cracker
in the mouth for a little time, it will begin to taste sweet, and if
the chewed cracker, which we know contains starch, is tested
with Fehling's solution, some 'of the starch will be found to have
changed to grape sugar. Here, again, a process of digestion has
taken place. In both the corn and in the mouth, the change is
brought about by the action of peculiar substances known as
digestive ferments, or enzymes. Such substances have the power
under certain conditions to change insoluble foods solids into

Test for grape sugar.

1 Directions for making these solutions will be found in Hunter's Laboratory
Problems in Civic Biology.

PLANT GROWTH AND NUTRITION

d.s.

p.r.

soluble substances liquids. The result is that substances which
before digestion would not dissolve in water now will dissolve.

The Action of Diastase on Starch. The enzyme found in the
cotyledon of the corn, which changes starch to grape sugar, is
called diastase. It may be separated from
the cotyledon and used in the form of a
powder.

To a little starch in half a cup of water
we add a very little (1 gram) of diastase
and put the vessel containing the mixture
in a warm place, where the temperature
will remain nearly constant at about 98
Fahrenheit. On testing part of the con
tents at the end of half an hour, and the
remainder the next morning, for starch and
for grape sugar, we find from the morning
test that the starch has been almost com
pletely changed to grape sugar. Starch
and warm water alone under similar con
ditions will not react to the test for grape
sugar.

Digestion has the Same Purpose in Plants
and Animals. In our own bodies we
know that solid foods taken into the mouth are broken up by the
teeth and moistened by saliva. If we could follow that food, we
would find that eventually it became part of the blood. It was
made soluble by digestion, and in a liquid form was able to reach
the blood. Once a part of the body, the food is used either to
release energy or to build up the body.

Summary. We have seen :

1. That seeds, in order to grow, must possess a food supply
either in or around their bodies.

2. That this food supply must be oxidized before energy is
released.

3. That in cases where the food is not stored at the point
where it is to be oxidized the food must be digested so that it
may be transported from one part to another in the same plant.

A germinating corn grain.
C, cotyledon; H, grow
ing root (hypocotyl) ; P,
growing stem (plumule) ;
S, endosperm; d.s., di
gested starch; p.r., pri
mary root; s.r., second
ary root; r.k., root hairs.

70 PLANT GROWTH AND NUTRITION

The life processes of plants and animals, so far, may be con
sidered as alike; they both feed, breathe (oxidize their food), do
work, and grow.

REFERENCE BOOKS

ELEMENTARY

Hunter, Laboratory Problems in Civic Biology. American Book Company.

Andrews, A Practical Course in Botany, pages 1-21. American Book Company.

Atkinson, First Studies of Plant Life, Chap. XXX. Ginn and Company.

Bailey, Botany, Chaps. XX, XXX. The Macmillan Company.

Beal, Seed Dispersal. Ginn and Company.

Bergen and Davis, Principles of Botany, Chaps. XX, XXX. Ginn and Company.

Coulter, Plant Life and Plant Uses. American Book Company.

Dana, Plants and their Children. American Book Company.

Mayne and Hatch, High School Agriculture. American Book Company.

Lubbock, Flowers, Fruits, and Leaves. The Macmillan Company.

Newell, Reader in Botany, pages 24-49. Ginn and Company.

Sharpe, A Laboratory Manual in Biology, pages 55-65. American Book Company.

ADVANCED

Bailey, The Evolution of our Native Fruits. The Macmillan Company.

Bailey, Plant Breeding. The Macmillan Company.

Coulter, Barnes, and Cowles, A Textbook of Botany, Vol. I. American Book Com
pany.

De Candolle, Origin of Cultivated Plants. D. Appleton and Company.

Duggar, Plant Physiology. The Macmillan Company.

Farmers' Bulletins, Nos. 78, 86, 225, 344. U. S. Department of Agriculture.

Hodge. Nature Study and Life, Chaps. X, XX. Ginn and Company.

Kerner (translated by Oliver), Natural History of Plants. Henry Holt and Com
pany, 4 vols. Vol. II, Part 2.

Sargent, Corn Plants. Houghton, Mifflin, and Company.

VI. THE ORGANS OF NUTRITION IN PLANTS THE
SOIL AND ITS RELATION TO THE ROOTS

Problem, What a plant takes from the soil and how it gets
it.

(a) What determines the direction of growth of roots ?

(6) How is the root built?

(d) What is in the soil that a root might take out ?

(e) Why is nitrogen necessary, and how is it obtained ?

LABORATORY SUGGESTIONS

Demonstration. Roots of bean or pea.

Demonstration or home experiment. Response of root to gravity and to
water. What part of root is most responsive ?

Laboratory work. Root hairs, radish or corn, position on root, gross
structure only. Drawing.

Demonstration. Root hair under compound microscope.

Demonstration. Apparatus illustrating osmosis.

Demonstration or a home experiment. Organic matter present in soil.

Demonstration. Root tubercles of legume.

Demonstration. Nutrients present in some roots.

Uses of the Root. If one of the seedlings of the bean spoken of
in the last chapter is allowed to grow in sawdust and is given
light, air, and water, sooner or later it will die. Soil is part of
its natural environment, and the roots which come in contact with
the soil are very important. It is the purpose of this chapter to
find out just how the young plant is fitted to get what it needs
from this part of its environment ; namely, the soil.

The development of a bean seedling has shown us that the root
grows first. One of the most important functions of the root to a young
seed plant is that of a holdfast, an anchor to fasten it in the place where
it is to develop. It has many other uses, as the taking in of water
with the mineral and organic matter dissolved therein, the stor-

SOIL AND ITS RELATION TO ROOTS

A root system, showing primary
and secondary roots.

age of food, climbing, etc. All
functions other than the first one
stated arise after the young plant
has begun to develop.

Root System. If you dig up a
young bean seedling and carefully
wash the dirt from the roots, you
will see that a long root is devel
oped as a continuation of the hy-
pocotyl. This root is called the
primary root. Other smaller roots
which grow from the primary root
are called secondary, or tertiary,
depending on their relation to the
first root developed.

Downward Growth of Root.
Influence of Gravity. Most of

the roots examined take a more or less downward direction. We

are all familiar with the fact that the force we call gravity influences

life upon this earth to a great degree. Does gravity act on the

growing root? This question may be

answered by a simple experiment.
Plant mustard or radish seeds in a

pocket garden, place it on one edge

and allow the seeds to germinate until

the root has grown to a length of about

half an inch. Then turn it at right

angles to the first position and allow it

to remain for one day undisturbed.

The roots now will be found to have

turned in response to the change in

position, that part of the root near

the growing point being the most

sensitive to the change. This ex
periment seems to indicate that the Revolve this figure in the direc-

roots are influenced to grow downward *| n of * he Arrows to see if

c the roots of the radish re-

by the force of gravity, spond to gravity.

SOIL AND ITS RELATION TO ROOTS 73

Experiments to determine the Influence of Moisture on a Grow
ing Root. The objection might well be interposed that possibly
the roots in the pocket garden 1 grew downward after water. That
moisture has an influence on the growing root is easily proved.

Plant bird seed, mustard or radish seed in the underside of a
sponge, which should be kept wet, and may be suspended by a
string under a bell jar in the schoolroom window. Note whether
the roots leave the sponge to grow downward, or if the moisture
in the sponge is sufficient to counterbalance the force of gravity.

Water a Factor which determines the Course taken by Roots.
Water, as well as the force of gravity, has much to do with the direction
taken by roots. Water is always found below the surface of the
ground, but sometimes at a great depth. Most trees, and all
grasses, have a greater area of surface exposed by the roots than
by the branches. The roots of alfalfa, a cloverlike plant used for
hay in the Western states, often penetrate the soil after water for
a distance of ten to twenty feet below the surface of the ground.

Fine Structure of a Root. 2 When we examine a delicate root
in thin longitudinal section under the compound microscope,
we find the entire root to be made up of cells, the walls of which
are uniformly rather thin. Over the lower end of the root is
found a collection of cells, most of which are dead, loosely arranged
so as to form a cap over the growing tip. This is evidently an
adaptation which protects the young and actively growing cells
just under the root cap. In the body of the root a central cylinder
can easily be distinguished from the surrounding cells. In a
longitudinal section a series of tubelike structures may be found
within the central cylinder. These structures are cells which have
grown together at the small end, the long axis of the cells running

1 The Pocket Garden. A very convenient form of pocket germinator may be
made as follows. Obtain two cleaned four by five negatives (window glass will
do) ; place one flat on the table and place on this half a dozen pieces of colored
blotting paper cut to a size a little less than the glass. Now cut four thin strips of
wood to fit on the glass just outside of the paper. Next moisten the blotter, place
on it some well-soaked radish, mustard seeds or barley grains, and cover with the
other glass. The whole box thus made should be bound together with bicycle tape.
Seeds will germinate in this box and with care may live for two weeks or more.

2 Sections of tradescantia roots are excellent for demonstration of these structures.

SOIL AND ITS RELATION TO ROOTS

bark ; c, inner layer of bark ;
d, wood or central cylinder.

the length of the main root. In their development the cells men
tioned have grown together in such a manner as to lose their small

ends, and now form continuous
hollow tubes with rather strong
walls. Other cells have come to
develop greatly thickened walls ;
these cells give mechanical sup
port to the tubelike cells. Col
lections of such tubes and sup
porting woody cells together make
up what are known as fibrovascular
bundles.

Root Hairs. Careful examina-

~ tion of the root of one of the seed-

Cross S3ction of a young taproot;

a, a, root hairs ; b, outer layer of lings of mustard, radish, or barley

grown in the pocket germinator
shows a covering of tiny fuzzy
structures. These structures are very minute, at most 3 to 4 milli
meters in length. They vary in length
according to their position on the root,
the most and the longest root hairs
being found near the point marked
R. H. in the figure. These structures
are outgrowths of the outer layer of the
root (the epidermis), and are of very
great importance to the living plant.

Structure of a Root Hair. A single
root hair examined under a compound
microscope will be found to be a long,
round structure, almost colorless in ap
pearance. The wall, which is very flexi
ble and thin, is made up of cellulose, a
substance somewhat like wood in chemi
cal Composition, through which fluids Young embryo of corn, show-
may easily pass. Clinging close to the
cell wall is the protoplasm of the cell.
The interior of the root hair is more or less filled with a fluid

ing root hairs (R. H.) and
growing stem (P.)-

SOIL AND ITS RELATION TO ROOTS

Diagram of a root hair; CS, cell sap; CW, cell
wall ; P, protoplasm ; N, nucleus ; S, particles
of soil.

called cell sap. Forming a part of the living protoplasm of the

root hair, sometimes in the hairlike prolongation and sometimes

in that part of the cell which forms the epidermis, is found a

nucleus. The protoplasm and nucleus are alive ; the cell wall

formed by the living matter in the cell is dead. The root hair is a

living plant cell with a wall

so delicate that water and

mineral substances from

the soil can pass through

it into the interior of the

root.

How the Root absorbs
Water. The process by
which the root hair takes
up soil water can better
be understood if we make
an artificial root hair large enough to be easily seen. An egg with
part of the outer shell removed so as to expose the soft skinlike
membrane underneath is an example. Better, an artificial root
hair may be made in the following way. Pour some soft celloidin
into a test tube ; carefully revolve the test tube so that an even
film of celloidin dries on the inside. This membrane is removed,
filled with white of egg, and tied over the end of a rubber cork in
which a glass tube has previously been inserted. When placed
in water, it gives a very accurate picture of the root hair at
work. After a short time water begins to rise in the tube, having
passed through the film of celloidin. If grape sugar, salt, or some
other substance which will dissolve in water were placed in the
water outside the artificial root hair, it could soon be proved by
test to pass through the wall and into the liquid inside.

Osmosis. To explain this process we must remember that
gases and liquids of different densities, when separated by a mem
brane, tend to flow toward each other and mingle, the greater flow
always being in the direction of the denser medium. The process
by which two gases or fluids, separated by a membrane, tend to pass
through the membrane and mingle with each other, is called osmosis.
The method by which the root hairs take up soil water is exactly

76 SOIL AND ITS RELATION TO ROOTS

the same process. It is by osmosis. The white of the egg is the
best possible substitute for living matter ; the celloidin membrane
separating the egg from the water is much like the delicate mem
brane-like wall which separates the protoplasm of the root hair
from the water in the soil surrounding it. The fluid in the root
hair is denser than the soil water ; hence the greater flow is toward
the interior of the root hair. 1

Passage of Soil Water within the Root. We have already seen
that in an exchange of fluids by osmosis the greater flow is always
toward the denser fluid. Thus it is that the root hairs take in
more fluid than they give up. The cell sap, which partly fills
the interior of the root hair, is a fluid of greater density than the
water outside in the soil. When the root hairs become filled with

The soil particles are each surrounded with a delicate film of water.
How might the root hairs take up this water ?

water, the density of the cell sap is lessened, and the cells of the
epidermis are thus in a position to pass along their supply of water
to the cells next to them and nearer to the center of the root.
These cells, in turn, become less dense than their inside neighbors,
and so the transfer of water goes on until the water at last reaches
the central cylinder. Here it is passed over to the tubes of the
woody bundles and started up the stem. The pressure created

1 For an excellent elementary discussion of osmosis see Moore, Physiology oj
Man and Other Animals. Henry Holt and Company.

SOIL AND ITS RELATION TO ROOTS

by this process of osmosis is sufficient to send water up the stem
to a distance, in some plants, of 25 to 30 feet. Cases are on
record of water having been raised in the birch a distance of 85
feet.

Physiological Importance of Osmosis. It is not an exaggera
tion to say that osmosis is a process not only of great importance
to a plant, but to an animal as well. Foods are digested in the
food tube of an animal ; that is, they are changed into a soluble
form so that they may pass through the walls of the food tube and
become part of the blood. The inner lining of part of the food
tube is thrown into millions of little fingerlike projections which
look somewhat, in size at least, like root hairs. These fingerlike
processes are (unlike a root hair) made up of many cells. But
they serve the same purpose as the root hairs, for they absorb
liquid food into the blood. This process of absorption is largely
by osmosis. Without the process of osmosis we should be unable
to use much of the food we eat.

Composition of Soil. If we examine a mass of ordinary loam
carefully, we find that it is composed of numerous particles of vary
ing size and weight. Between these particles, if the soil is not caked
and hard packed, we can find tiny spaces. In well-tilled soil these
spaces are constantly be
ing formed and enlarged.
They allow air and water
to penetrate the soil. If
we examine soil under the
microscope, we find con
siderable water clinging to
the soil particles and form
ing a delicate film around
each particle. In this
manner most of the water
is held in the soil.

How Water is held in

Soil. To understand what comes in with the soil water, it will
be necessary to find out a little more about soil. Scientists who
have made the subject of the composition of the earth a study,

Inorganic soil is being formed by weathering.

SOIL AND ITS RELATION TO ROOTS

tell us that once upon a time at least a part of the earth was molten.
Later, it cooled into solid rock. Soil making began when the ice

and frost, working al
ternately with the heat,
chipped off pieces of
rock. These pieces in
time became ground in
to fragments by action
of ice, glaciers, running
water, or the atmos
phere. This process
is called weathering.
Weathering is aided by
oxidation. A glance
at almost any crum
bling stones will con
vince you of this,
because of the yellow
oxide of iron (rust)
disclosed. So by slow
degrees this earth be
came covered with a
coating of what we call
inorganic soil. Later,
generation after generation of tiny plants and animals which lived
in the soil died, and their remains formed the first organic materials
of the soil.

You are all familiar with
the difference between the
so-called rich soil and poor
soil. The dark soil con
tains more dead plant and
animal matter, which
foflrns the portion called
humus.

Humus contains Or
ganic Matter. It is an

This picture shows how the forests help to cover
the inorganic soil with an organic coating.
Explain how.

Apparatus for testing the capacity of soils
to take in and r.etain moisture.

SOIL AND ITS RELATION TO ROOTS

easy matter to prove that black soil contains organic matter, for if

an equal weight of carefully dried humus .and soil from a sandy road

is heated red-hot for some time and

then re weighed, the humus will be

found to have lost considerably in

weight, and the sandy soil to have

lost very little. The material left

after heating is inorganic material,

the organic matter having been

burned out.

Soil containing organic materials
holds water much more readily than
inorganic soil, as a glance at the
accompanying figure shows. If we
fill each of the vessels with a given
weight (say 100 grams each) of
gravel, sand, barren soil, rich loam,
leaf mold, and 25 grams of dry,
pulverized leaves, then pour equal
amounts of water (100 c.c.) on each
and measure all that runs through, the water that has been re
tained will represent the water supply that plants could draw on
from such soil.

The Root Hairs take more than Water out of the Soil. If a
root containing a fringe of root hairs is washed carefully, it will be
found to have little particles of soil still clinging to it. Examined
under the microscope, these particles of soil seem to be cemented
to the sticky surface of the root hair. The soil contains, besides
a number of chemical compounds of various mineral substances,
lime, potash, iron, silica, and many others, a considerable amount
of organic material. Acids of various kinds are present in the soil.
These acids so act upon certain of the mineral substances that
they become dissolved in the water which is absorbed by the root
hairs. Root hairs also give off small amounts of acid. An in
teresting experiment may be shown (see Figure on page 80) to
prove this. A solution of phenolphthaldn loses its color when an
acid is added to it. If a growing pea be placed in a tube contain-

Soil particles cling to root hairs.
Why?

SOIL AND ITS RELATION TO ROOTS

ing some of this solution the latter will quickly change from a rose
pink to a colorless solution.

A Plant needs Mineral Matter to Make Living Matter. Liv
ing matter (protoplasm), besides containing the chemical elements

carbon, hydrogen, oxygen, and nitrogen,
contains a very minute proportion of
various elements which make up the
basis of certain minerals. These are
calcium (lime), sulphur, iron, potassium,
magnesium, phosphorus, sodium, and
chlorine.

That plants will not grow well with
out certain of these mineral substances
can be proved by the growth of seed
lings in a so-called nutrient solution. 1
Such a solution contains all the mineral
matter that a plant uses for food. If
certain ingredients are left out of this
solution, the plants placed in it will not
live.

Nitrogen in a Usable Form necessary
Effect of root hairs on phenol- for Growth of Plants. A chemical
phthaiein solution. The element needed by the plant to make

change of color indicates , ... ,,

the presence of acid. protoplasm is nitrogen. The air can

be proven by experiment to be made

up of about four fifths nitrogen, but this element cannot be taken
from either soil water or air in a pure state, but is usually ob
tained from the organic matter in the soil, where it exists with
other substances in the form of nitrates. Ammonia and other
organic compounds which contain nitrogen are changed by two
groups of little plants called bacteria, first into nitrites and then
nitrates. 2

1 See Hunter's Laboratory Problems in Civic Biology for list of ingredients.

2 It has recently been discovered that under some conditions these bacteria are
preyed upon 'by tiny one-celled animals (protozoa) living in the soil and are so re
duced in numbers that they cannot do their work effectively. If, then, the soil
is heated artificially or treated with antiseptics so as to kill the protozoa, the bac
teria which escape multiply so rapidly as to make the land much richer than before.

SOIL AND ITS RELATION TO ROOTS

Relation of Bacteria to Free Nitrogen. It has been known
since the time of the Romans that the growth of clover, peas,
beans, and other legumes in soil causes it to become more favorable
for growth of other plants. The reason for this has been dis
covered in late years. On the
roots of the plants mentioned
are found little swellings or
nodules ; in the nodules exist
millions of bacteria, which take
nitrogen from the atmosphere
and fix it so that it can be used
by the plant ; that is, they as
sist in forming nitrates for the
plants to use. Only these
bacteria, of all the living plants,
have the power to take the free
nitrogen from the air and make
it over into a form that can be
used by the roots. As all the
compounds of nitrogen are used
over and over again, first by
plants, then as food for animals,
eventually returning to the soil
again, or in part being turned
into free nitrogen, it is evident
that any new supply of usable

nitrogen must Come by means Diagram to show how the nitrogen-fixing
,. ,1 ., f. . -, bacteria prepare nitrogen for use by

of these nitrogen-fixing bac- plants; tubercles,
teria.

Rotation of Crops. The facts mentioned above are made use
of by careful farmers who wish to make as much as possible from
a given area of ground in a given time. Such plants as are hosts
for the nitrogen-fixing bacteria are planted early in the season.
Later these plants are plowed in and a second crop is planted.
The latter grows quickly and luxuriantly because of the nitrates
left in the soil by the bacteria which lived with the first crop.
For this reason, clover is often grown on land in which it is pro-

HUNTER, CIV. BI. 6

SOIL AND ITS RELATION TO ROOTS

posed to plant corn, the nitrogen left in the soil thus giving nourish
ment to the young corn plants. In scientifically managed farms,
different crops are planted in a given field on different years so that
one crop may replace some of the elements taken from the soil by
the previous crop. This is known as rotation of crops. 1 The
annual yield of the average farm may thus be greatly increased.

Five of the elements necessary to the life of the plant which
may be taken out of the soil by constant use are calcium, nitrogen,
phosphorus, potassium, and sulphur. Several methods are used

by the farmer to prevent the
exhaustion of these and other
raw food materials from the soil.
One method known as fallowing
is to allow the soil to remain
idle until bacteria and oxidation
have renewed the chemical ma
terials used by the plants. This
is an expensive method, if land
is dear. The most common
method of enriching soil is by
means of fertilizing material
rich in plant food. Manure is
most frequently used, but many
artificial fertilizers, most of
which contain nitrogen in the

Nitrogen in the soil is necessary for plants.
Explain from this diagram how nitro
gen is put into the soil by some plants
and taken out by others.

form of some nitrate, are used,
because they can be more easily transported and sold. Such are
ground bone, guano (bird manure), nitrate of soda, and many
others. These also contain other important raw food materials
for plants, especially potash and phosphoric acid. Both of these
substances are made soluble so as to be taken into the roots by
the action of the carbon dioxide in the soil.

The Indirect Relation of this to the City Dweller. All of us
living in the city are aware of the importance of fresh vegetables,

1 That crop rotation is not primarily a process to conserve the fertility of the
soil, but is a sanitary measure to prevent infection of the soil, is the latest belief
of the scientist.

SOIL AND ITS RELATION TO ROOTS 83

brought in from the neighboring market gardens. But we some
times forget that our great staple crops, wheat and other cereals,
potatoes, fruits of all kinds, our cotton crop, and all plants we make
use of grow directly in proportion to the amount of raw food ma
terials they take in through the roots. When we also remember
that many industries within the cities, as mills, bakeries, and the
like, as well as the earnings of our railways and steamship lines, are
largely dependent on the abundance of the crops, we may recognize
the importance of what we have read in this chapter.

Food Storage in Roots of Commercial Importance. Some plants,
as the parsnip, carrot, and radish, produce no seed until the second
year, storing food in the roots the first year and using it to get an
early start the following spring, so as to be better able to produce
seeds when the time comes. This food storage in roots is of much
practical value to mankind. Many of our commonest garden
vegetables, as those mentioned above, and the beet, turnip, oyster
plant, sweet potato and many others, are of value because of the
food stored. The sugar beet has, in Europe especially, become
the basis of a great industry.

REFERENCE BOOKS
ELEMENTARY

Hunter, Laboratory Problems in Civic Biology. American Book Company.
Bigelow, Applied Biology. The Macmillan Company.

Coulter, Plant Life and Plant Uses, Chaps. Ill, IV. American Book Company.
Mayne and Hatch, High School Agriculture. American Book Company.
Moore, The Physiology of Man and Other Animals. Henry Holt and Company.
Sharpe, Laboratory Manual in Biology, pp. 73-87. American Book Company.

ADVANCED

Coulter, Barnes, and Cowles, A Textbook of Botany, Part II. Amer. Book Co.
Duggar, Plant Physiology. The Macmillan Company.
Goodale, Physiological Botany. American Book Company.
Green, Vegetable Physiology, Chaps. V, VI. J. and A. Churchill.
Kerner-Oliver, Natural History of Plants. Henry Holt and Company.
MacDougal, Plant Physiology. ' Longmans, Green, and Company.

VII. PLANT GROWTH AND NUTRITION PLANTS
MAKE FOOD

Problem. Where, when, and how green plants make food ?
(a} How and why is moisture given off from leaves?
(6) What is the reaction of leaves to light ?

(d) What by-products are given off in the above process ?

(e) Other functions of leaves.

LABORATORY SUGGESTIONS

Demonstration. Water given off by plant in sunlight. Loss of weight
due to transpiration measured.
Laboratory exercise.

(a) Gross structure of a leaf.

(6) Study of stoma and lower epidermis under microscope.

(c) Study of cross section to show cells and air spaces.
Demonstration. Reaction of leaves to light.
Demonstration. Light necessary to starch making.
Demonstration. Air necessary to starch making.
Demonstration. Oxygen a by-product of starch making.

What becomes of the Water taken in
by the Roots? We have seen that
more than pure water has been absorbed
through the root hairs into the roots.
What becomes of this water and the
other substances that have been ab
sorbed? This question may be partly
answered by the following experiments.

Passage of Fluids up the Stem. If
any young growing shoots (young seed
lings of corn or pea, or the older stems
of garden balsam, touch-me-not, or sun
flower) are placed in red ink (eosin),
and left in the sun for a few hours, the
red ink will be found to have passed up
the stem. If such stems were examined
84

Apple twigs split to show the
course of colored water up
the stem.

PLANTS MAKE POOD

carefully, it would be seen that the

colored fluid is confined to collections

of woody tubes immediately under the

inner bark. Water evidently rises in

that part of the stem we call the wood.
Water given off by Evaporation from

Leaves. -- Take some well-watered

potted green plant, as a geranium or

hydrangea, cover the pot with sheet

rubber, fastening the rubber close to

the stem of the plant. Next weigh

the plant with the pot. Then cover

it with a tall bell jar and place the ap
paratus in the sun. In a few minutes

drops of moisture are seen to gather

on the inside of the jar. If we now
weigh the pot
ted plant, we
find it weighs
less than be
fore.

ously the loss
comes from the

water lost, and evidently this water escapes
as vapor from either the stem or leaves.

The Structure of a Leaf. In the ex
periment with the red ink mentioned
above we will find that the fluid has gone
out into the skeleton or framework of
the leaf. Let us now examine a leaf
more carefully. It shows usually (1) a
flat, broad blade, which may take almost
any conceivable shape ; (2) a stem which
spreads out in the blade (3) in a number
of veins.

The Cell Structure of a Leaf. The

V., the veins. ' under surface of a leaf seen under the

O b V 1- Experiment to prove that water
is given off through the leaves
of a green plant.

PLANTS MAKE FOOD

microscope usually shows numbers of tiny oval openings. These
are called stomata (singular stoma). Two cells, usually kidney-
shaped, are found, one on each side of the opening. These are
the guard cells. By change in shape of these cells the opening
of the stoma is made larger or smaller. Larger irregular cells
form the epidermis, or outer covering of the leaf. Study of the

leaf in cross section shows that these
stomata open directly into air chambers
which penetrate between % and around
the loosely arranged cells composing
the underpart of the leaf. The upper
surface of leaves sometimes contains
stomata, but more often they are lack
ing. The under surface of an oak leaf
of ordinary size contains about 2,000,000
stomata. Under the upper epidermis
is a layer of green cells closely packed
together (called collectively the palisade
layer). These cells are more or less
columnar in shape. Under these are
several rows of rather loosely placed
cells just mentioned. These are called
collectively the spongy tissue. If we
happen to have a section cut through
a vein, we find this composed of a

number of tubes made up of, and strengthened by, thick-walled
cells. The veins are evidently a continuation of the tubes of the
stem out into the blade of the leaf.

Evaporation of Water. During the day an enormous amount
of water is taken up by the roots and passed out through the
leaves. So great is this excess at times that a small grass plant
on a summer's day evaporates more than its own weight in water.
This would make nearly half a ton of water, delivered to the air
during twenty-four hours by a grass plot twenty-five by one hun
dred feet, the size of the average city lot. According to Ward,
an oak tree may pass off two hundred and twenty-six times its
own weight in water during the season from June to October.

Section through the blade of a
leaf as seen under the com
pound microscope. S, air
spaces, which communicate
with the outside air; V, vein
in cross section; S.T., breath
ing hole (stoma); E, outer
layer of cells; P, green cells.

PLANTS MAKE FOOD

From which Surface of the Leaf is Water Lost ? In order to find out
whether water is passed out from any particular part of the leaf, we may
remove two leaves of the same size and weight from some large-leaved
plant x a mullein was used for the illustrations given below and cover
the upper surface of one leaf and the lower surface of the other with vase
line. The leaf stalks of each should be covered with wax or vaseline, and
the two leaves exactly balanced on the pans of a balance which has pre
viously been placed in a warm and sunny place. Within an hour the leaf
which has the upper surface covered with vaseline will show a loss of

Experiment to show through which surface of a leaf water passes off.

weight. Examination of the surface of a mullein leaf shows us that the
lower surface of the leaf is provided with stomata. It is through these organs,
then, that water is passed out from the tissues of the leaf.

Factors in Transpiration. The amount of water lost from a
plant varies greatly under different conditions. The humidity
of the air, its temperature, and the temperature of the plant all
affect the rate of transpiration. The stomata also tend to close
under some conditions, thus helping to prevent evaporation. But
there seems to be no certain regulation of this water loss. Conse
quently plants droop or wilt on hot dry days because they cannot

i The "rubber plant" leaf is an easily obtainable and excellent demonstration,

PLANTS MAKE FOOD

obtain water rapidly enough from the soil to make up for the loss
through the leaves.

Diagrams of a stoma. a, surface view of a closed stoma; b, the same stoma
opened. (After Hanson.) c, diagrams of a transverse section through a stoma,
dotted lines indicate the closed position of the guard cells, the heavy lines the
open condition. (After Schwendener.)

Green Plants Food Makers. We have previously stated
that green plants are the great food makers for themselves and
for animals. We are now ready to attack the problem of how
green plants make food.

The Sun a Source of Energy. We all know the sun is a source
of most of the energy that is released on this earth in the form of
heat or light. Every boy knows the power of a " burning glass."
Solar engines have not come into any great use as yet, because
fuel is cheaper, but some day we undoubtedly will directly harness
the energy of the sun in everyday work. Actual experiments
have shown that vast amounts of energy are given to the earth.
When the sun is highest in the sky, energy equivalent to one hun
dred horse power is received by a plot of land twenty-five by one
hundred feet, the size of a city lot. Plants receive and use much
of this energy by means of their leaves.

Effect of Light on Plants. In young plants which have been
grown in total darkness, no green color is found in either stems
or leaves, the latter often being reduced to mere scales. The
stems are long and more or less reclining. We can explain the
changed condition of the seedling grown in the dark only by as
suming that light has some effect on the protoplasm of the seedling
and induces the growth of the green part of the plant. If seedlings
have been growing on a window sill, or where the light comes in
from one side, you have doubtless noticed that the stem and leaves
of the seedlings incline in the direction from which the light comes.

PLANTS MAKE FOOD

The experiment pictured shows this effect of light very plainly.
A hole was cut in one end of a cigar box and barriers were erected
in the interior of the box so that the seeds planted in the sawdust
received their light by an indirect course. The young seedling
in this case responded to the influence of the stimulus of light so
as to grow out finally through the hole in the box into the open

Two stages in an experiment to show that green plants grow
toward the light.

air. This growth of the stem to the light is of very great impor
tance to a growing plant, because, as we shall see later, food mak
ing depends largely on the amount of sunlight the leaves receive.
Effect of Light on Leaf Arrangement. It is a matter of common
knowledge that green leaves turn toward the light. Place grow
ing pea seedlings, oxalis, or any other plants of rapid growth near
a window which receives full sunlight. Within a short time the
leaves are found to be in positions to receive the most sunlight
possible. Careful observation of any plant growing outdoors
shows us that in almost every case the leaves are so disposed as
to get much sunlight. The ivy climbing up the wall, the morning-
glory, the dandelion, and the burdock all show different arrange
ments of leaves, each presenting a large surface to the light.
Leaves are often definitely arranged, fitting in between one

PLANTS MAKE FOOD

another so as to present their upper surface to the sun. Such an
arrangement is known as a leaf mosaic. In the case of the dande
lion, a rosette or whorled cluster of leaves is found. In the horse-
chestnut, where the leaves come out opposite each other, the. older
leaves have longer petioles than the young ones. In the mullein
the entire plant forms a cone. The old leaves near the bottom
have long stalks, and the little ones near the apex come out close

A lily, showing long narrow
leaves.

The dandelion, showing a whorled ar
rangement of long irregular leaves.

to the main stalk. In every case each leaf receives a large amount
of light. Other modifications of these forms may easily be found
on any field trip.

Starch made by a Green Leaf. If we examine the palisade
layer of the leaf, we find cells which are almost cylindrical in form.
In the protoplasm of such cells are found a number of little green-
colored bodies, which are known as chloroplasts or chlorophyll
bodies. If we place the leaf in wood alcohol, we find that the
bodies still remain, but that the color is extracted, going into the
alcohol and giving to it a beautiful green color. The chloroplasts
are, indeed, simply part of the protoplasm of the cell colored green.
These bodies are of the greatest importance directly to plants and
indirectly to animals. The chloroplasts, by means of the energy re-

PLANTS MAKE FOOD

ceived from the sun, manufacture starch out of certain raw materials.
These raw materials are soil water, which is passed up through
the bundles of tubes into the veins of the leaf from the roots, and
carbon dioxide, which is taken in through the stomata or pores,
which dot the under surface of the leaf. A plant with variegated
leaves, as the coleus, makes starch only in the green part of the
leaf, even though these raw materials reach all parts of the leaf.

Light and Air necessary for
Starch Making. If we pin strips
of black cloth, such as alpaca, over
some of the leaves of a growing
hydrangea which has previously
been placed in a dark room for a

An experiment to show the effect of ex
cluding light (but not air) from the
leaves of a green plant. The result of
this experiment is seen in the next
picture. (Experiment performed by
C. Dobbins and A. Schwartz.)

Starchless area in a leaf caused
by excluding sunlight by
means of a strip of black
cloth.

few hours, and then put the plant in direct sunlight for an hour
or two, we are ready to test for starch. We then remove some of
the covered leaves and extract the chlorophyll with wood alcohol
(because the green color of the chlorophyll interferes with the blue
color of the starch test). A test then shows that starch is present
only in the portions of the leaves exposed to sunlight. From this
experiment we infer that the sun has something to do with starch
making in a leaf. The necessity of a part of the air (carbon
dioxide) for starch making may also easily be proved, for the

PLANTS MAKE FOOD

parts of leaves covered with vaseline will be found to contain no
starch, while parts of the leaf without vaseline, but exposed to the
sun and air, do contain starch.

Air is necessary for the process of starch making in a leaf,
not only because carbon dioxide gas is absorbed (there are from
three to four parts in ten thousand present in the atmosphere),

Diagram to show starch making. Read the text carefully and then explain

this diagram.

but also because the leaf is alive and must have oxygen in order to
do work. This oxygen it takes from the air around it.

Comparison of Starch Making and Milling. The manufacture

of starch by the green leaf
is not easily understood.
The process has been com
pared to the milling of
grain. In this case the
mill is the green part of the
leaf. The sun furnishes the
motive power, the chloro-
plasts constitute the ma
chinery, and soil water and
carbon dioxide are the raw
products taken into the
mill. The manufactured
product is starch, and a
certain by-product (corre
sponding to the waste in a

Diagram to illustrate the formation of mil1 ) is als & veu Out ' This

starch in a leaf. by-product is oxygen. To

PLANTS MAKE FOOD

understand the process fully, we must refer to a small portion
of the leaf shown below. Here we find that the cells of the green
layer of the leaf, under the upper epidermis, perform most of
the work. The carbon dioxide is taken in through the stomata
and reaches the green cells by way of the intercellular spaces and
by osmosis from cell to cell. Water reaches the green cells
through the veins. It then passes into the cells by osmosis, and
there becomes part of the cell sap. The light of the sun easily
penetrates to the cells of the palisade layer, giving the energy

Diagram (after Stevens) to illustrate the processes of breathing and food
making in the cells of a green leaf in the sunlight.

needed .to make the starch. This whole process is a very delicate
one, and will take place only when external conditions are favorable.
For example, too much heat or too little heat stops starch making
in the leaf. This building up of food and the release of oxygen
by the plant in the presence of sunlight is called photosynthesis.

Manufacture of Fats. Inasmuch as tiny droplets of oil are
found inside the chlorophyll bodies in the leaf, we believe that fats,
too, are made there, probably by a transformation of the starch
already manufactured.

Protein Making and its Relation to the Making of Living Matter.
Protein material is a food which is necessary to form protoplasm.

PLANTS MAKE FOOD

Protein food is present in the leaf, and is found in the stem or root
as well. Proteins can apparently be manufactured in any of the
cells of green plants, the presence of light not seeming to be a nec
essary factor. How it is manufactured is a matter of conjecture.
The minerals brought up in the soil water form part of its composi
tion, and starch or grape sugar give three elements (C, H, and 0).
The element nitrogen is taken up by the roots as a nitrate (nitrogen
in combination with lime or potash). Proteins are probably not

made directly into protoplasm
in the leaf, but are stored by
the cells of the plant and used
when needed, either to form
new cells in growth or to re
pair waste. While plants and
animals obtain their food in
different ways, they probably
make it into living substance
(assimilate it) in exactly the
same manner.

Foods serve exactly the same
purposes in plants and in ani
mals ; they either build living
matter or they are burned
(oxidized) to furnish energy
(power to do work). If you
doubt that a plant exerts
energy, note how the roots of
a tree bore their way through

the hardest soil, and how stems or roots of trees often split open
the hardest rocks, as illustrated in the figure above.

Starch-Making and its Relation to Human Welfare. Leaves
which have been in darkness show starch to be present soon after
exposure to light. A corn plant sends 10 to 15 grams of reserve
material into the ears in a single day. The formation of fruit, and
especially the growth of the grain fields, show the economic im
portance of this fact. Not only do plants make their own food
and store it away, but they make food for animals as well. And

An example of how a tree may exert
energy. This rock has been split by
the growing tree.

PLANTS MAKE FOOD

the food is stored in such a stable form that it may be sent to all
parts of the world in the form of grain or other fruits. Animals,
herbivorous and flesh-eating, man himself, all are dependent upon
the starch-making processes of the green plant for the ultimate
source of their food. When we remember that in 1913 in the
United States the total value of all farm crops was over
$6,000,000,000, and when we realize that these products came from
the air and soil through the energy of the sun, we may begin to
realize why as city boys and girls the study
of plant biology is of importance to us.

Green Plants give off Oxygen in Sun
light. In still another way green plants
are of direct use to us in the city. Dur
ing this process of starch-making oxygen
is given off as a by-product. This may
easily be proven by the following experi
ment. 1 Place any green water plant in a
battery jar partly filled with water, cover
the plants with a glass funnel and mount
a test tube full of water over the mouth of
the funnel. Then place the apparatus in a
warm sunny window. Bubbles of gas are
seen to rise from the plant. After two or
three hours of hot sun, enough of the gas
can be obtained by displacement of the
water to make the oxygen test.

That oxygen is given off as a by-product

by green plants is a fact of far-reaching Experiment to show that
importance. City parks are true " breath
ing spaces." The green covering of the
earth is giving to animals an element that

they must have, while the animals in their turn are supplying to
the plants carbon dioxide, a compound used in food-making.
Thus a widespread relation of mutual helpfulness exists between
plants and animals.

1 Immediate success with this experiment will be obtained if the water has been
previously charged with carbon dioxide.

oxygen is given off by
green plants in the sun
light.

96 PLANTS MAKE FOOD

Respiration by Leaves. All living things require oxygen. It
is by means of the oxidation of food materials within the plant's
body that the energy used in growth and movement is released.
A plant takes in oxygen largely through the stomata of the leaves,
to a less extent through the lenticels or breathing holes in the stem,
and through the roots. Thus rapidly growing tissues receive the
oxygen necessary for them to perform their work. The products
of oxidation in the form of carbon dioxide are also passed off
through these same organs. It can be shown by experiment that
a plant uses up oxygen in the darkness ; in the light the amount
of oxygen given off as a by-product in the process of starch-making
is, of course, much greater than the amount used by the plant.

Summary. From the above paragraphs it is seen that a leaf
performs the following functions : (1) breathing, or the taking in
of oxygen and passing off of carbon dioxide ; (2) starch-making,
with the incidental passing out of oxygen ; (3) formation of proteins,
with their digestion and assimilation to form new tissues; and
(4) the transpiration of water.

REFERENCE BOOKS

ELEMENTARY

Hunter, Laboratory Problems in Civic Biology. American Book Company.
Andrews, A Practical Course in Botany, pages 160-177. American Book Company.
Coulter, A Textbook of Botany, pages 540. D. Appleton and Company.
Coulter, Plant Life and Plant Uses. American Book Company.
Dana, Plants and their Children, pages 135-185. American Book Company.
Sharpe, A Laboratory Manual in Biology, pages 90-102. American Book Company.
Stevens, Introduction to Botany, pages 81-99. D. C. Heath and Company.

ADVANCED

Clement, Plant Physiology and Ecology. Henry Holt and Company.

Coulter, Barnes, and Cowles, A Textbook of Botany, Part II, and Vol. II. American

Book Company.

Darwin, Insectivorous Plants. D. Appleton and Company. \~

Duggar, Plant Physiology. The Macmillan Company.
Goodale, Physiological Botany, pages 337-353 and 409-424. American Book

Company.

Green, Vegetable Physiology. J. and A. Churchill.

Lubbock, Flowers, Fruits, and Leaves, last part. The Macmillan Company.
MacDougal, Practical Textbook of Plant Physiology. Longmans, Green, and

Company.

Report of the Division of Forestry, U. S. Department of Agriculture, 1899.
Ward, The Oak. D. Appleton and Company.

VIII. PLANT GROWTH AND NUTRITION THE CIR
CULATION AND FINAL USES OF FOOD BY PLANTS

Problem. How green plants store and use the food they
make.

(a) What are the organs of circulation ?
(6) How and where does food, circulate ?
(c) How does the plant assimilate its food ?

LABORATORY SUGGESTIONS

Laboratory exercise. The structure (cross section) of a woody stem.
Demonstration. To show that food passes downward in the bark.
Demonstration. To show the condition of food passing through the
stem.

Demonstration. Plants with special digestive organs.

The Circulation and Final Uses of Foods in Green Plants. We
have seen that cells of green plants make food and that such cells
are mostly in the leaves. But all parts of the bodies of plants grow.
Roots, stems, leaves, flowers, and fruits grow. Seeds are store
houses of food. We must now examine the stem of some plant in
order to see how food is distributed, stored, and finally used in the
various parts of the plant.

The Structure of a Woody Stem. If we cut a cross section
through a young willow or apple stem, we find it shows three
distinct regions. The center is occupied by the spongy, soft pith;
surrounding this is found the rather tough wood, while the outer
most area is bark. More careful study of the bark reveals the
presence of three layers an outer layer, a middle green layer,
and an inner fibrous layer, the latter usually brown in color. This
layer is made up largely of tough fiberlike cells known as bast
fibers. The most important parts of this inner bark, so far as the
plant is concerned, are many tubelike structures known as sieve
tubes. These are long rows of living cells, having perforated

HUNTER, CIV. HI. 7 97

98 CIRCULATION AND USES OF FOOD BY PLANTS

sievelike ends. Through these cells food materials pass downward
from the upper part of the plant, where they are manufactured.

In the wood will be noticed (see Figure) a number of lines radiat
ing outward from the pith toward the bark. These are thin plates
of pith which separate the wood into a number of wedge-shaped
masses. These masses of wood are composed of many elongated

cells, which, placed end to end,
form thousands of little tubes
connecting the leaves with the
roots. In addition to these are
many thick-walled cells, which
give strength to the mass of
wood. The bundles of tubes
with their surrounding hard
walled cells are the continua
tion of the bundles of tubes
which are found in the root.
In sections of wood which have
taken several years to grow,

Section of a twig of box elder three years
old, showing three annual growth rings.
The radiating lines (ra) which cross the
wood (w) represent the pith rays, the
principal ones extending from the pith
in the center to the cortex or bark.
(From Coulter's Plant Relations.)

we find so-called annual rings.
The distance between one ring
and the next (see Figure) usu
ally represents the amount of
growth in one year. Growth
takes place from an actively dividing layer of cells, known as the
cambium layer. This layer forms wood cells from its inner surface
and bark from its outer surface. Thus new wood is formed as a
distinct ring around the old wood.

Use of the Outer Bark. The outer bark of a tree is protective.
The cells are dead, the heavy woody skeletons serving to keep out
cold and dryness, as well as prevent the evaporation of fluids from
within. The bark also protects the tree from attack of other
plants or animals which might harm it. Most trees are provided
with a layer of corky cells. This layer in the cork oak is thick
enough to be of commercial importance. The function of the
corky layer in preventing evaporation is well seen in the case of
the potato, which is a true stem, though found underground. If

CIRCULATION AND USES OF FOOD BY PLANTS 99

two potatoes of equal weight are balanced on the scales, the skin
having been peeled from one, the peeled potato will be found to
lose weight rapidly. This is due to loss of water, which is held in
by the skin of the unpeeled potato (see right hand figure below).

There are also small breathing holes known as lenticels scattered
through the surface of the bark. These can easily be seen in a
young woody stem of apple, beech, or horse-chestnut.

Experiment to show that the skin of the potato (a stem) retards evaporation.

Proof that Food passes down the Stem. If freshly cut willow
twigs are placed in water, roots soon begin to develop from that
part of the stem which is under water. If now the stem is girdled
by removing the bark in a ring just above where the roots are
growing, the latter will eventually die, and new roots will appear
above the girdled area. The food material necessary for the out
growth of roots evidently comes from above, and the passage of
food materials takes place in a downward direction just outside
the wood in the layer of bark which contains the bast fibers and
sieve tubes. This experiment with the willow explains why it is
that trees die when girdled so as to cut. the sieve tubes of the inner
bark. The food supply is cut off from the protoplasm of the cells
in the part of the tree below the cut area. Many of the canoe
birches of our Adirondack forest are thus killed, girdled by thought-

100 CIRCULATION AND USES OF FOOD BY PLANTS

less visitors. In the same manner mice and other gnawing ani
mals kill fruit trees. Food substances are also conducted to a
much less extent in the wood itself, and food
passes from the inner bark to the center of
the tree by way of the pith plates. This can
be proved by testing for starch in the pith
plates of young stems. It is found that
much starch is stored in this part of the tree
trunk.

In what Form does Food pass through
the Stem ? We have already seen that
materials in solution (those substances which
will dissolve in the water) will pass from cell
to cell by the process of osmosis. This is
shown in the experiment illustrated in the
figure. Two thistle tubes are partly filled,
Experiment to show that one with starch and water, the other with
food material passes SU nr ar an j wa ter, and a piece of parchment

down in the inner bark.

paper is tied over the end of each. The
lower ends of both tubes are placed in a glass dish under water.
After twenty-four hours, the water in the dish is tested for starch,
and then for sugar. We find that only the sugar, which has been
dissolved by the water, can pass
through the membrane.

Digestion. Much of the food
made in the leaves is stored in
the form of starch. But starch,
being insoluble, cannot be passed
from cell to cell in a plant. It
must be changed to a soluble
form, for otherwise it could not
pass through the delicate cell
membranes. This is accomplished
by the process of digestion. We
have already seen that starch is

Changed to grape SUgar in the Experiment to show osmosis of sugar

O ^^ O **1 ^ ^ O /Virrlif ViQTirl -fnKrA cmrl n nY_nam r>ai a

corn by the action of a substance

(right hand tube) and non-osmosis
of starch (left hand tube).

CIRCULATION AND USES OF FOOD BY PLANTS 101

(an enzyme) called diastase. This process of digestion seemingly
may take place in all living parts of the plant, although most of
it is done in the leaves. In the bodies of all animals, including
man, starchy foods are changed in a similar manner, but by
other enzymes, into soluble grape sugar.

The food material may be passed in a soluble form until it comes
to a place where food storage is to take place, then it can be trans
formed to an insoluble form (starch, for example) ; later, when
needed by the plant in growth, it may again be transformed and sent
in a soluble form through the stem to the place where it will be used.

In a similar manner, protein seems to be changed and trans
ferred to various parts of the plant. Some forms of protein sub
stance are soluble and others insoluble in water. White of egg, for
example, is slightly soluble, but can be rendered insoluble by heat
ing it so that it coagulates. Insoluble proteins are digested within
the plant ; how and where is but slightly understood. In a plant,
soluble proteins pass down the sieve
tubes in the bast and then may be stored
in the bast or medullary rays of the wood
in an insoluble form, or they may pass
into the fruit or seeds of a plant, and be
stored there.

What forces Water up the Stem. We
have seen that the process of osmosis is
responsible for taking in soil water, and
that the enormous absorbing surface ex
posed by the root hairs makes possible
the absorption of a large amount of water.
Frequently this is more than the weight
of the plant in every twenty-four hours.

Experiments have been made which
show that at certain times in the year
this water is in some way forced up the
tiny tubes of the stem. During the

spring season, in young and rapidly growing trees, water has been
proved to rise to a height of nearly ninety feet. The force that
causes this rise of water in stems is known as root pressure.

Diagram to show the areas
in a plant through which
the raw food materials pass
up the stem and food ma
terials pass down.

102 CIRCULATION AND USES OF FOOD BY PLANTS

The greatest factor, however, is transpiration of water from
leaves. This evaporation of water in the form of vapor seems to
result in a kind of suction on the column of water in the stem. In
the fall, after the leaves have gone, much less water is taken in by
roots, showing that an intimate relation exists between the leaves
and the root.

Summary of the Functions of Green Plants. The processes
which we have just described (with the exception of food making)
are those which occur in the lives of any plant or animal. All
plants and animals breathe, they oxidize their foods to release
energy, carbon dioxide being given off as the result of the union of
the carbon in the foods with the oxygen of the air. Both plants
and animals digest their food ; plants may do this in the cells of
the root, stem, and leaf. Digestion must always occur so that food
can be moved in a soluble condition from cell to cell in the plant's
body.

Plants with Special Digestive Organs. Some plants have
special organs of digestion. One of these, the sundew, has leaves
which are covered on one side with tiny glandular hairs. These

Leaf of sundew closing over The Venus fly trap, showing open

a captured insect. and closed leaves.

attract insects and later serve to catch and digest the nitrogenous
matter of these insects by means of enzymes poured out by the
same hairs. Another plant, the Venus fly trap, catches insects
in a sensitive leaf which folds up and holds the insect fast until
enzymes poured out by the leaf slowly digest it. Still others,

CIRCULATION AND USES OF FOOD BY PLANTS 103

called pitcher plants, use as food the decayed bodies of insects
which fall into their cuplike leaves and die there. In this respect
plants are like those animals which have certain organs in the
body set apart for the digestion of food.

Assimilation. The assimilation of foods, or making of foods
into living matter, is a process we know very little about. We
know it takes place in the living cells of plants and animals. But
how foods are changed into living matter is one of the mysteries
of life which we have not yet solved.

Excretion. The waste and repair of living matter seems to
take place in both plants and animals. When living plants
breathe, they give off carbon dioxide. In the process of starch-
making, oxygen might be considered the waste product. Water
is evaporated from leaves and stems. The leaves fall and carry
away waste mineral substances which they contain.

Reproduction. Finally, both plants and animals have organs
of reproduction. We have seen that the flower gives rise, after
pollination, to a fruit which holds the seeds. These seeds hold

(a) (6) (c) (d)

The embryos of (a) the morning glory, (6) the barberry, (c) the potato, (d) the
four o'clock, showing the position of their food supply. (After Gray.)

the embryo. Thus the young plant is doubly protected for a time
and is finally thrown off in the seed with enough food to give it a
start in life. In much the same way we will find that animals
reproduce, either by laying eggs which contain an embryo and food
to start it in life or, as in the higher animals, by holding and pro
tecting the embryo within the body of the mother until it is born,
a helpless little creature, to be tenderly nourished by the mother
until able to care for itself.

The Life Cycle. Ultimately both plants and animals grow
old and die. Some plants, for example the pea or bean, live but

104 CIRCULATION AND USES OF FOOD BY PLANTS

a season ; others, such as the big trees of California, live for hun
dreds of years. Some insects exist as adults but a day, while the
elephant is said to live almost two hundred years. The span of
life from the time the plant or animal begins to grow until it dies
is known as the life cycle.

REFERENCE BOOKS
ELEMENTARY

Hunter, Laboratory Problems in Civic Biology. American Book Company.
Andrews, A Practical Course in Botany, pages 112-127. American Book Company.
Atkinson, First Studies of Plant Life, Chaps. IV, V, VI, VIII, XXI. Ginn.
Coulter, Plant Life and Plant Uses, Chap. V. American Book Company.
Dana, Plants and their Children, pages 99-129. American Book Company.
Mayne and Hatch, High School Agriculture. American Book Company.
Hodge, Nature Study and Life, Chaps. IX, X, XI. Ginn and Company.
MacDougal, The Nature and Work of Plants. The Macmillari Company.

ADVANCED

Apgar, Trees of the United States, Chaps. II, V, VI. American Book Company.
Coulter, Barnes, and Cowles, A Textbook of Botany, Vol. I. American Book

Company.

Duggar, Plant Physiology. The Macmillan Company.
Ganong, The Teaching Botanist. The Macmillan Company.
Goebel, Organography of Plants, Part V. Clarendon Press.
Goodale, Physiological Botany. American Book Company.
Gray, Structural Botany, Chap. V. American Book Company.
Kerner-Oliver, Natural History of Plants. Henry Holt and Company.
Strasburger, Noll, Schenck, and Karston, A Textbook of Botany. The Macmillan

Company.

Ward, The Oak. D. Appleton and Company.
Yearbook, U. S. Department of Agriculture, 1894, 1895, 1898-1910.

IX. OUR FORESTS, THEIR USES AND THE NECES
SITY FOR THEIR PROTECTION

Problem. Man's relations to forests.

(a) What is the value of forests to man?

(&) What can man do to prevent forest destruction ?

LABORATORY SUGGESTIONS

Demonstration of some uses of wood. Optional exercise on structure
of wood. Method of cutting determined by examination. Home work
on study of furniture trim, etc.

Visit to Museum to study some economic uses of wood.

Visit to Museum or field trip to learn some common trees.

The Economic Value of Trees. Protection and Regulation of
Water Supply. Trees form a protective covering for parts of

A forest in North Carolina. (U. S. G. S.)
105

106

OUR FORESTS

the earth's surface. They prevent soil from being washed away,
and they hold moisture in the ground. The devastation of im
mense areas in China and
considerable damage by
floods in parts of Switzer
land, France, and in Penn
sylvania has resulted where
the forest covering has
been removed. No one
who has tramped through
our Adirondack forest can
escape noticing the differ
ences in the condition of

Working to prevent erosion after the removal streams surrounded by
of the forest in the French Alps. forest and those which

flow through areas from

which trees have been cut. The latter streams often dry up
entirely in hot weather, while the forest-shaded stream has a
never failing supply of crystal water.

The city of New York owes much of its importance to its posi
tion at the mouth of a great river with a harbor large enough to
float the navies of the
world. This river is
supplied with water
largely from the Adi
rondack and Catskill
forests. Should these
forests be destroyed, it
is not impossible that
the frequent freshets
which would follow
would so fill the Hud
son River with silt and _

Erosion at Sayre, Pennsylvania, by the Ohemnng
debris that the ship River. (Photograph by W. C. Barbour.)

channels in the bay,

already costing the government hundreds of thousands of dollars

a year to keep dredged, would become too shallow for ships. If

OUR FORESTS 107

this should occur, the greatest city in this country would soon
lose its place and become of second-rate importance.

The story of how this very thing happened to the old Greek
city of Poseidonia is graphically told in the following lines :

" It was such a strange, tremendous story, that of the Greek Poseidonia,
later the Roman Psestum. Long ago those adventuring mariners from
Greece had seized the fertile plain, which at that time was covered with
forests of great oak and watered by two clear and shining rivers. They
drove the Italian natives back into the distant hills, for the white man's
burden even then included the taking of all the desirable things that were
being wasted by incompetent natives, and they brought over colonists
whom the philosophers and moralists at home maligned, no doubt,
in the same pleasant fashion of our own day. And the colonists cut
down the oaks, and plowed the land, and built cities, and made harbors,
and finally dusted their busy hands and busy souls of the grime of labor and
wrought splendid temples in honor of the benign gods who had given them
the possessions of the Italians and filled them with power and fatness.

" Every once in so often the natives looked lustfully down from the hills
upon this fatness, made an armed snatch at it, were driven back with bloody
contumely, and the heaping of riches upon riches went on. And more and
more the oaks were cut down mark that ! for the stories of nations
are so inextricably bound up with the stories of trees until all the plain
was cleared and tilled ; and then the foothills were denuded, and the wave
of destruction crept up the mountain sides, and they, too, were left naked
to the sun and the rains.

" At first these rains, sweeping down torrentially, unhindered by the
lost forests, only enriched the plain with the long-hoarded sweetness of
the trees ; but by and by the living rivers grew heavy and thick, vomiting
mud into the ever shallowing harbors, and the land soured with the un-
drained stagnant water. Commerce turned more and more to deeper
ports, and mosquitoes began to breed in the brackish soil that was making
fast between the city and the sea.

" Who of all those powerful landowners and rich merchants could ever
have dreamed that little buzzing insects could sting a great city to death ?
But they did. Fevers grew more and more prevalent. The malaria
haunted population went more and more languidly about their business.
The natives, hardy and vigorous in the hills, were but feebly repulsed.
Carthage demanded tribute, and Rome took it, and changed the city's
name from Poseidonia to Psestum. After Rome grew weak, Saracen

108

OUR FORESTS

corsairs came in by sea and grasped the slackly defended riches, and the
little winged poisoners of the night struck again and again, until grass
grew in the streets, and the wharves crumbled where they stood. Finally,
the wretched remnant of a great people wandered away into the more
wholesome hills, the marshes rotted in the heat and grew up in coarse
reeds where corn and vine had flourished, and the city melted back into
the wasted earth." 1

Prevention of Erosion by Covering of Organic Soil. We have
shown how ungoverned streams might dig out soil and carry it

Result of deforestation in China. This land has been ruined by erosion.
(Carnegie Institution Research in China.)

far from its original source. Examples of what streams have done
may be seen in the deltas formed at the mouths of great rivers.
The forest prevents this by holding the water supply and letting it
out gradually. This it does by covering the inorganic soil with
humus or decayed organic material. In this way the forest floor

l . Elizabeth Bisland and Anne Hoyt, Seekers in Sicily. John Lane Company.

OUR FORESTS

109

becomes like a sponge, holding water through long periods of
drought. The roots of the trees, too, help hold the soil in place.
The gradual evaporation of water through the stomata of the leaves
cools the atmosphere, and this tends to precipitate the moisture
in the air. Eventually the dead bodies of the trees themselves are
added to the organic covering, and new trees take their place.

Other Uses of the Forest. In some localities forests are used
as windbreaks and to protect mountain towns against avalanches.

FOREST REGIONS \ /S^ ml Forest regions

I Heaviest forests

The forest regions of the United States.

In winter they moderate the cold, ard in summer reduce the heat
and lessen the danger from storms. Birds nesting in the woods
protect many valuable plants which otherwise might be destroyed
by insects.

Forests have great commercial importance. Pyrogallic and
other acids are obtained from trees, as are tar, creosote, resin, tur
pentine, and many useful oils. The making of maple sirup and
sugar forms a profitable industry in several states.

The Forest Regions of the United States. The combined area
of all the forests in the United States, exclusive of Alaska, is about
500,000,000 acres. This seemingly immense area is rapidly de-

110

OUR FORESTS

creasing in acreage and in quality, thanks to the demands of an
increasing population, a woeful ignorance on the part of the owners
of the land, and wastefulness on the part of cutters and users alike.
A glance at the map on page 109 shows the distribution of
our principal forests. Washington ranks first in the produc
tion of lumber. Here the great Douglas fir, one of the " ever
greens," forms the chief source of supply. In the Southern states,
especially Louisiana and Mississippi, yellow pine and cypress are
the trees most lumbered.

Which states produce the most hardwoods ? From which states
do we get most of our yellow pine, spruce, red fir, redwood ?
Where are the heaviest forests of the United States ?

Uses of Wood. Even in this day of coal, wood is still by far
the most used fuel. It is useful in building. It outlasts iron

under water, in addition to
being durable and light.
It is cheap and, with care
of the forests, inexhaust
ible, while our mineral
wealth may some day be
used up. Distilled wood
gives wood alcohol. Par
tially burned wood is char
coal. In our forests much
of the soft wood (the cone-
bearing trees, spruce, bal
sam, hemlock, and pine),

and poplars, aspens, basswood, with some other species, make paper
pulp. The daily newspaper and cheap books are responsible for in
roads on our forests which cannot well be repaired. It is not nec
essary to take the largest trees to make pulp wood. Hence many
young trees of not more than six inches in diameter are sacrificed.
Of the hundreds of species of trees in our forests, the conifers are
probably most sought after for lumber. Pine, especially, is prob
ably used more extensively than any other wood. It is used in
all heavy construction work, frames of houses, bridges, masts,
spars and timber of ships, floors, railway ties, and many other

Transportation of 1 umber in the West.
A logging train.

OUR FORESTS

111

purposes. Cedar is, used for shingles, cabinetwork, lead pencils,
etc. ; hemlock and spruce for heavy timbers and, as we have seen,

Transportation of lumber in the East. Logs are mostly floated down rivers

to the mills.

for paper pulp. Another use for our lumber, especially odds and
ends of all kinds, is in the packing-box industry. It is estimated
that nearly 50 per cent of all lumber cut ultimately finds its way
into the construction of boxes.
Hemlock bark is used for tanning.
The hard woods ash, bass-
wood, beech, birch, cherry, chest
nut, elm, maple, oak, and walnut
are used largely for the "trim"
of our houses, for manufacture of
furniture, wagon or car work, and
endless other purposes.

Diagrams of sections of timber.
a, cross section; b, radial; c, tan
gential. (From Pinchot, U. S. Dept.
of Agriculture.)

Methods of cutting Timber. A
glance at the diagram of the sections
of timber shows us that a tree may be
cut radially through the middle of

the trunk or tangentially to the middle portion. Most lumber is cut
tangentially. In wood cut in this manner the yearly rings take a more
or less irregular course. The grain in wood is caused by the fibers not

112 OUR FORESTS

taking straight lines in their course in the tree trunk. In many cases the
fibers of the wood take a spiral course up the trunk, or they may wave
outward to form little projections. Boards cut out of such a piece of
wood will show the effect seen in many of the school
desks, where the annual rings appear to form ellip
tical markings. Quite a difference in color and
structure is often seen between the heart wood,
composed of the dead walls of cells occupying the
central part of the tree trunk, and the sapwood,
the living part of the stem.

Knots. Knots, as can be seen from the dia
gram, are branches which at one time started in
S3ction of ateee trunk their outward growth and were for some reason
showing knot. killed. Later, the tree, continuing in its outward

growth, surrounded them and covered them up.

A dead limb should be pruned before such growth occurs. The markings
in bird's-eye maple are caused by buds which have not developed, and
have been overgrown with the wood of the tree.

Destruction of the Forest. By Waste in Cutting. Man is
responsible for the destruction of one of this nation's most valuable
assets. This is primarily due to wrong and wasteful lumbering.
Hundreds of thousands of dollars' worth of lumber is left to rot
annually because the lumbermen do not cut the trees close enough
to the ground, or because through careless felling of trees many
other smaller trees are injured. There is great waste in the mills.
In fact, man wastes in every step from the forest to the finished
product.

By Fire. Indirectly, man is responsible for fire, one of the
greatest enemies of the forest. Most of the great forest fires of
recent years, the losses from which total in the hundreds of mil
lions, have been due either to railroads or to carelessness in making
fires in the woods. It is estimated that in forest lands traversed
by railroads from 25 per cent to 90 per cent of the fires are caused
by coal-burning locomotives. For this reason laws have been made
in New York State requiring locomotives passing through the
Adirondack forest preserve to burn oil instead of coal. This
has resulted in a considerable reduction in the number of fires. In
addition to the loss in timber, the fires often burn out the organic

OUR FORESTS

113

matter in the soil (the " duff ") forming the forest floor, thus pre
venting the growth of forest there for many years to come. In
New York and other states fires are fought by an organized corps

A forest in the far west totally destroyed by fire and wasteful lumbering.

of fire wardens, whose duty it is to watch the forest and to fight
forest fires.

Other Enemies. Other enemies of the forest are numerous
fungus plants, insect parasites which bore into the wood or destroy
the leaves, and grazing animals, particularly sheep. Wind and
snow also annually kill many trees.

Forestry. In some parts of central Europe, the value of the
forests was seen as early as the year 1300 A.D., and many towns
consequently bought up the surrounding forests. The city of
Zurich has owned forests in its vicinity for at least 600 years and
has found them a profitable investment. In this country only
recently has the importance of preserving and caring for our
forests been noted by our government. Now, however, we have a
Forest Survey of the Department of Agriculture and numerous
state and university schools of forestry which are rapidly teach-

HUNTER, CIV. BI. 8

114

OUR FORESTS

The forest primeval. Trees are killing
each other in the struggle for light
and air.

ing the people of this country the
best methods for the preserva
tion of our forests. The Federal
government has set aside a num
ber of tracts of mountain forest
in some of the Western states,
making a total area of over
167,000,000 acres. New York
has established for the same pur
pose the Adirondack Park, with
nearly 1,500,000 acres of timber-
land. Pennsylvania has one of
700,000 acres, and many other
states have followed their ex
ample.

Methods for Keeping and Pro
tecting the Forests. Forests

should be kept thinned. Too many trees are as bad as too few.
They struggle with one another for foothold and light, which only
a few can enjoy. In cutting
the forest, it should be con
sidered as a harvest. The
oldest trees are the " ripe
grain," the younger trees
being left to grow to matur
ity. Several methods of re
newing the forest are in use
in this country. (1) Trees
may be cut down and young
ones allowed to sprout from
cut stumps. This is called
coppice growth. This growth
is well seen in parts of New
Jersey. (2) Areas or strips

may be Cut OUt SO that Seeds A German beech forest. The trees are kept
frnm npio-Vihnrincr tr^oa aro thinned out so as to allow the young trees

to get a start. Contrast this with the

carried there to start new picture above.

OUR FORESTS

115

growth. (3) Forests may be artificially
planted. Two seedlings planted for every
tree cut is a rule followed in Europe. (4)
The most economical method is that shown
in the lower picture on page 114, where the
largest trees are thinned out over a large
area so as to make room for the younger
ones to grow up. The greatest dangers
to the forests are from fire and from care
less cutting, and these dangers may be
kept in check by the efficient work of our
national and state foresters.

A City's Need for Trees. The city of
Paris, well known as one of the most
beautiful of European capitals, spends
over $100,000 annually in caring for and
replacing some of the 90,000 trees owned
by. the city. All over the United States
the city governments are beginning to
realize what European cities have long
known, that trees are of great value to a

city. They are now following the example of European cities by
planting trees and by protecting the trees after they are planted.
Thousands of city trees are annually killed by horses which
gnaw the bark. This may be prevented by proper protection of
the trunk by means of screens or wire guards. Chicago has
appointed a city forester, who has given the following excellent
reasons why trees should be planted in the city :

(1) Trees are beautiful in form and color, inspiring a constant appreci
ation of nature.

(2) Trees enhance the beauty of architecture.

(3) Trees create sentiment, love of country, state, city, and home.

(4) Trees have an educational influence upon citizens of all ages,
especially children.

(5) Trees encourage outdoor life.

(6) Trees purify the air.

(7) Trees cool the air in summer and radiate warmth in winter

(8) Trees improve climate and conserve soil and moisture.

We must protect our city
trees. This tree was
badly wounded by be
ing gnawed by a horse.

116 OUR FORESTS

(9) Trees furnish resting places and shelter for birds.

(10) Trees increase the value of real estate.

(11). Trees protect the pavement from the heat of the sun.

(12) Trees counteract adverse conditions of city life.

Let us all try to make Arbor Day what it should be, a day for
caring for and planting trees, for thus we may preserve this most
important heritage of our nation.

REFERENCE BOOKS

ELEMENTARY

Hunter, Laboratory Problems in Civic Biology. American Book Company.
Mayne and Hatch, High School Agriculture. American Book Company.
Murrill, Shade Trees, Bui. 205, Cornell University Agricultural Experiment Station.
Pinchot, A Primer of Forestry, Division of Forestry, U. S. Department of Agri
culture.

ADVANCED

Apgar, Trees of the United States, Chaps. II, V, VI. American Book Company.
Coulter, Barnes, and Cowles, A Textbook of Botany, Part I and Vol. II. American

Book Company.

Goebel, Organography of Plants, Part V. Clarendon Press.
Strasburger, Noll, Schenck, and Karston, A Textbook of Botany. The Macmillan

Company.

Ward, Timber and Some of its Diseases. The Macmillan Company.
Yearbook, U.S. Department of Agriculture, Division of Forestry, Buls. 7, 10, 13,

16, 17, 18, 20, 26, 27.

X. THE ECONOMIC RELATION OF GREEN PLANTS

TO MAN

Problems. How green plants are useful to man.

(a) As food.

(&) For clothing.

How green plants are harmful to man.

SUGGESTED LABORATORY WORK

If a commercial museum is available, a trip should be planned to work
over the topics in this chapter. The school collection may well include
most of the examples mentioned, both of useful and harmful plants.

A study of weeds and poisonous plants should be taken up in actual
laboratory work, either by collection and identification or by demon
stration.

Green Plants have a " Dollar and Cents " Value. To the girl
or boy living in the city green plants seem to have little direct
value. Although we see vegetables for sale in stores and we know
that fruits have a money value, we are apt to forget that the wealth
of our nation depends more upon its crops than it does on its
manufactories and business houses. The economic or " dollars
and cents " value of plants is enormous and far too great for us
to comprehend in terms of figures.

We have already seen some of the uses to mankind of the
products of the forest; let us now consider some other plant
products.

Leaves as Food. Grazing animals feed almost entirely on
tender shoots or leaves, blades of grass, and other herbage.
Certain leaves and buds are used by man as food. Lettuce,
beet tops, kale, spinach, broccoli, are examples. A cabbage
head is nothing but a big bud which has been cultivated by

117

118 ECONOMIC IMPORTANCE OF GREEN PLANTS

man. An onion is a compact budlike mass of thickened leaves
which contain stored food.

Cabbage

Onions
Leaves used as food.

Lettuce

Stems as Food. A city child would, if asked to name some
stem used as food, probably mention asparagus. We sometimes

^^___ t forget that one of our

greatest necessities, cane
sugar, comes from the
stem of sugar cane. Over
seventy pounds of sugar
is used each year by every
person in the United
States. To supply the
growing demand beets are
now being raised for their
sugar in many parts of
the world, so that nearly
half the total supply of
sugar comes from this
source. Maple sugar is
a well-known commodity
which is obtained by boil
ing the sap of sugar maple until it crystallizes. Over 16,000 tons
of maple sugar is obtained every spring, Vermont producing about
40 per cent of the total output. The sago palm is another stem

Celery

Kohl-rabi Potato
Stems used as food.

Sugar cane

ECONOMIC IMPORTANCE OF GREEN PLANTS 119

which supports the life of many natives in Africa. Another stem,
living underground, forms one of man's staple articles of diet.
This is the potato.

Roots as Food. Roots which store food for plants form im
portant parts of man's vegetable diet. Beets, radishes, carrots,
parsnips, sweet potatoes, and many others might be mentioned.

The following table shows the proportion of foods in some of
the commoner roots and stems :

WATER

PROTEINS

CARBO
HYDRATES

FAT

MINERAL
MATTER

Potato . . .

1.2

0.3

Carrot

Parsnip

1.2

8.7

1.5

1.0

Turnip . . . .

92.8

0.5

0.1

Onion

1 5

Sweet potato ....
Beet

82.2

1.5
0.4

20.2
134

0.1
0.1

1.5
09

Fruits and Seeds as Foods. Our cereal crops, corn, wheat,
etc., have played a very great part in the civilization of man and
are now of so much importance to him as food products that bread

Wheat

Nuts Pear

Seeds and fruits used for food.

Melon

made from flour from the wheat has been called the " staff of life."
Our grains are the cultivated progeny of wild grasses, Domesti-

120 ECONOMIC IMPORTANCE OF GREEN PLANTS

cation of plants and animals marks epochs in the advance of civili
zation. The man of the stone age hunted wild beasts for food,
and lived like one of them in a cave or wherever he happened to
be ; he was a nomad, a wanderer, with no fixed home. ' He may
have discovered that wild roots or grains were good to eat ; per
haps he stored some away for future use. Then came the idea of
growing things at home instead of digging or gathering the wild
fruits from the forest and plain. The tribes which first cultivated
the soil made a great step in advance, for they had as a result a
fixed place for habitation. The cultivation of grains and cereals
gave them a store of food which could be used at times when other
food was scarce. The word " cereal " (derived from Ceres, the
Roman Goddess of Agriculture) shows the importance of this crop
to Roman civilization. From earliest times the growing of grain
and the progress of civilization have gone hand in hand. As
nations have advanced in power, their dependence upon the cereal
crops has been greater and greater.

" Indian corn," says John Fiske, in The Discovery of America,
11 has played a most important part in the history of the New
World. It could be planted without clearing or plowing the soil.
There was no need of threshing or winnowing. Sown in tilled land,
it yields more than twice as much food per acre as any other kind
of grain. This was of incalculable advantage to the English
settlers in New England, who would have found it mnch harder
to gain a secure foothold upon the soil if they had had to begin by
preparing it for wheat or rye."

To-day, in spite of the great wealth which comes from our
mineral resources, live stock, and manufactured products, the
surest index of our country's prosperity is the size of the corn
and wheat crop. According to the last census, the amount of
capital invested in agriculture was over $20,000,000,000, while
that invested in manufacture was less than one half that amount.

Corn. About three billion bushels of corn were raised in the
United States during the year 1910. This figure is so enormous
that it has but little meaning to us. In the past half century
our corn crop has increased over 350 per cent. Illinois and Iowa
are the greatest corn-producing states, each having a yearly record

ECONOMIC IMPORTANCE OF GREEN PLANTS 121

of over four hundred million bushels. The figure on this page
shows the principal corn-producing areas in the United States.

Indian corn is put to many uses. It is a valuable food. It con
tains a large proportion of starch, from which glucose (grape sugar)
and alcohol are made. Machine oil and soap are made from it.
The leaves and stalk are an excellent fodder; they can be made
into paper and packing material. Mattresses can be stuffed with

Indian Corn Production Percentage

30 40 50 6f 7 t O

Illinois

Mo.

Neb. Ind. Kan. Tex. Ohio

Rest oi United States

the husks. The pith is used as a protective belt placed below the
water line of our huge battleships. Corn cobs are used for fuel,
one hundred bushels having the fuel value of a ton of coal.

Wheat. Wheat is the crop of next greatest importance in size.
Nearly seven hundred millions of bushels were raised in this
country in 1910, representing a total money value of over $700,-
000,000. Seventy-two per cent of all the wheat raised comes from
the North Central states and California. About three fourths of
the wheat crop is exported, nearly one half of it to Great Britain,
thus indirectly giving employment to thousands of people on rail
ways and steamships. Wheat has its chief use in its manufacture

122 ECONOMIC IMPORTANCE OF GREEN PLANTS

into flour. The germ, or young wheat plant, is sifted out during
this process and made into breakfast foods. Flour making forms

WHEAT

Rs^i 160 to 640 bushels per sauare mile
K%%3 oyer 640 ,

Wheat Crop in United States Percentage Source

20 30 <W 50 60 7 80

Minnesota Kansas N.Dak. Neb. Ind. S.D. Wash. O. Mo.

Other States

the chief industry of Minneapolis, Minnesota, and of several other
large and wealthy cities in this country.

Other Grains. Of the other grain and cereals raised in this
country, oats are the most important crop, over one billion bushels
having been produced in 1910. Barley is another grain, a staple
of some of the northern countries of Europe and Asia. In this
country, it is largely used in making malt for the manufacture of
beer. Rye is the most important cereal crop of northern Europe,
Russia, Germany, and Austro-Hungary producing over 50 per
cent of the world's supply. One of the most important grain crops
for the world (although relatively unimportant in the United
States) is rice. The fruit of this grasslike plant, after thrashing,
screening, and milling, forms the principal food of one third of the
human race. Moreover, its stems furnish straw, its husks make
a bran used as food for cattle, and the grain, when fermented and
distilled, yields alcohol.

ECONOMIC IMPORTANCE OF GREEN PLANTS 123

A field of rice, showing the conditions of culture.

Garden Fruits. Green plants and especially vegetables have
come to play an important part in the dietary of man. The
diseases known as scurvy and beri-beri, the latter the curse of the
far Eastern navies, have been largely prevented by adding vege
tables and fruit juices to the dietary of the sailors. People in
this country are beginning to find that more vegetables and less
meat are better than the meat diet so often used. Market gar
dening forms the lucrative business of many thousands of people
near our great cities. Some of the more important fruits- are
squash, cucumbers, pumpkins, melons, tomatoes, peppers, straw
berries, raspberries, and blackberries. The latter fruits bring in
an annual income of $25,000,000 to our market gardeners. Beans
and peas are important as foods because of their relatively large

124 ECONOMIC IMPORTANCE OF GREEN PLANTS

amount of protein. Canning green corn, peas, beans, and toma
toes has become an important industry.

Orchard and Other Fruits. In the United States over one
hundred and seventy-five million bushels of apples are grown every
year. Pears, plums, apricots, peaches, and nectarines also form
large orchards, especially in California. Nuts form one of our

important articles of food,
largely because of the large
amount of protein contained
in them.

The grape crop of the
world is commercially valu
able, because of the raisins
and wine produced. The
culture of lemons, oranges,
and grapefruit has come
in recent years to give a
living to many people in
this country as well as in
other parts of the world.
Figs, olives, and dates are
staple foods in the Mediter
ranean countries and are
sources of wealth to the
people there, as are coco
nuts, bananas, and many

Picking apples, an important crop in some .

parts of the United States. other fruits in tropical

countries.

Beverages and Condiments. The coffee and cacao beans, and
leaves of the tea plant, products of tropical regions, form the basis
of very important beverages of civilized man. Pepper, black and
red, mustard, allspice, nutmegs, cloves, and vanilla are all products
manufactured from various fruits or seeds of tropical plants.

Alcoholic liquors are produced from various plants in different
parts of the world, the dried fruit of the hop vine being an
important product of New York State used in the making of
beer.

ECONOMIC IMPORTANCE OF GREEN PLANTS 125

Raw Materials. Besides use as food, green plants have many
other uses. Many of our city industries would not be in existence,
were it not for certain plant products which furnish the raw ma
terials for many manufacturing industries. Many cities of the
east and south, for example, depend upon cotton to give employ
ment to thousands of factory hands.

Cotton. Of our native plant products cotton is probably of
the most importance to the outside world. Over eleven million
bales of five hundred pounds each are raised annually.

COTTON

ES3 / to 20 bales per square mile

Cotton Crop in United States Percentage Source

*1|) 20 M 40 &Q 60 70 JK>

Texas

Georgia

Miss. Alabama S.Car. Ark. Okla. N.C.La.Oth.

Sta.

Cotton Crop in United States Percentage Consumption

, ? 3 . . *. ' *-

United States
North South

Great Britain & Ireland

Germany France It. Rest of

World

The cotton plant thrives in warm regions. Its commercial
importance is gained because the seeds of the fruit have long fila
ments attached to them. Bunches of these filaments, after treat
ment, are easily twisted into threads from which are manufactured
cotton cloth, muslin, calico, and cambric. In addition to the

126 ECONOMIC IMPORTANCE OF GREEN PLANTS

fiber, cottonseed oil, a substitute for olive oil, is made from the
seeds, and the refuse remaining makes an excellent cattle fodder.
Cotton Boll Weevil. The cotton crop of the United States has
rather recently been threatened with destruction by a beetle called
the cotton boll weevil. This insect, which bores into the young

GULF OF MEXICO

Map showing the spread of the cotton boll weevil. It was introduced from Mexico
about 1894. What proportion of the cotton raising belt was infected in 1908 ?

pod of the cotton, develops there, stunting the growth of the fruit
to such an extent that seeds are not produced. The loss in Texas
alone is estimated at over $10,000,000 a year. The boll weevil,
because of the protection offered by the cotton boll, is very diffi
cult to exterminate. The weevils are destroyed by birds, the
infected bolls and stalks are burnt, millions are killed each winter

ECONOMIC IMPORTANCE OF GREEN PLANTS 127

by cold, other insects prey on them, but at the present time they
are one of the greatest pests >the south knows.

The control of this pest seems to depend upon early planting so
that the crop has an opportunity to ripen before the insects in the
boll grow large enough to do harm. Ultimately the boll weevil

Ifi

Mexican cotton boll weevil. Much enlarged, above; natural
size, below. (Herrick.)

may do more good than harm by bringing into the market a type
of cotton plant that ripens very early.

Vegetable Fibers. Among the most important are Manila
hemp, which comes from the leaf-stalks of a plant of the banana
family and true hemp, which is the bast or woody fiber of a plant
cultivated in most warm parts of the earth. Flax is also an im
portant fiber plant, grown largely in Russia and other parts of
Europe (see picture on next page) . From the bast fibers of the
stem of this herb linen cloth is made.

Vegetable Oils. Some of the same plants which give fiber
also produce oil. Cotton seed oil pressed from the seeds, linseed
oil from the seeds of the flax plant, and coconut oil (the covering
of the nut here producing the fiber) are examples.

Some Harmful Green Plants. We have seen that on the whole
green plants are useful to man. There are, however, some that

128 ECONOMIC IMPORTANCE OF GREEN PLANTS

are harmful. For example, the
poison ivy is extremely poison
ous to touch. The poison ivy
is a climbing plant which at
taches itself to the trees or
walls by means of tiny air
roots which grow out from the
stem. It is distinguished from
its harmless climbing neighbor,
the Virginia Creeper, by the
fact that its leaves are notched
in threes instead of fives. Every
boy and girl should know
poison ivy.

Numerous other poisonous
common plants are found, but
one other deserves special
notice because of its presence
in vacant city lots. The Jim-

Flax grown for fiber.

son Weed (Datura) is a bushy plant,
from two to five feet high, bearing
large leaves. It has white or pur
plish flowers, and later bears a four-
valved seed pod containing several
hundred seeds. These plants con
tain a powerful poison, and people
are often made seriously ill by
eating the roots or other parts by
mistake.

Weeds. From the economic
standpoint the green plants which

Poison ivy, a climbing plant which
is poisonous to touch. Notice the
leaves in threes.

ECONOMIC IMPORTANCE OF GREEN PLANTS 129

do the greatest damage are weeds.- Those plants which provide
best for their young are usually the most successful in life's
race. Plants which combine with- the ability to scatter many
seeds over a wide territory the additional characteristics of rapid
growth, resistance to dangers of extreme cold or heat, attacks of
enemies, inedibility, and peculiar adaptations to cross-pollina
tion or self-pollination, are usually spoken of as weeds. They
flourish in the sterile soil of the roadside and in the fertile soil of
the garden. By means of rapid growth they kill other plants of
slower growth by usurping their territory. Slow-growing plants
are thus actually exterminated. Many of our common weeds
have been introduced from other countries and have, through
their numerous adaptations, driven out other plants which stood
in their way. Such is the Russian Thistle. A single plant of
this kind will give rise to over 20,000 seeds. First introduced from
Russia in 1873, it spread so rapidly that in twenty years it had
appeared as a common weed over an area of some twenty-five
thousand square miles. It is now one of the greatest pests in our
Northwest.

REFERENCE BOOKS

ELEMENTARY

Hunter, Laboratory Problems in Civic Biology. American Book Company.

Gannet, Commercial Geography. American Book Company.

Sargent, Plants and their Uses. Henry Holt and Company.

Toothaker, Commercial Raw Materials. Ginn and Company.

U. S. Dept. of Agriculture, Farmers' Bulletin 86, Thirty Poisonous Plants of the

United States, V. K. Chestnut. Bulletin 17. Two Hundred Weeds, How to

Know Them and How to Kill Them, L. H. Dewey.

ADVANCED

Bailey, Cyclopedia of American Agriculture. The Macmillan Company.

HUNTER, CIV. BT. 9

XL PLANTS WITHOUT CHLOROPHYLL IN THEIR
RELATION TO MAN

Problems. (a) How molds and other saprophytic fungi do
harm to man.

(&) What yeasts do for manlcind.

(1) Conditions favorable and unfavorable to growth.
(2} Their relations to mankind.

{3} Some methods of fighting harmful bacteria and
diseases caused by them.

LABORATORY SUGGESTIONS

Field work. Presence of bracket fungi and chestnut canker.

Home experiment. Conditions favorable to growth of mold.

Laboratory demonstration. Growth of mold, structure, drawing.

Home experiment or laboratory demonstration. Conditions unfavorable
for growth of molds.

Demonstration. Process of fermentation.

Microscopic demonstration. Growing yeast cells. Drawing.

Home experiment. Conditions favorable for growth of yeast.

Home experiment. Conditions favorable for growth of yeast in bread.

Demonstration and experiment. Where bacteria may be found.

Demonstration. Methods of growth of bacteria, pure cultures and col
onies shown.

Demonstration. Foods preferred by bacteria.

Demonstration. Conditions favorable for growth of bacteria.

Demonstration. Conditions unfavorable for growth of bacteria.

Demonstration by charts, diagrams, etc. The relation of bacteria to
disease in a large city.

COLORLESS PLANTS ARE USEFUL AND HARMFUL TO MAN

The Fungi. We have found that green plants on the whole
are useful to mankind. But not all plants are green. Most of
us are familiar with the edible mushroom sold in the markets or

130

PLANTS WITHOUT CHLOROPHYLL

131

the so-called " toadstools " found in parks or lawns. These
plants contain no chlorophyll and hence do not make their own
food. They are members of the plant group called fungi. Such
plants are almost as much dependent upon the green plants for
food as are animals. But the fungi require for the most part
dead organic matter for their food. This may be obtained from
decayed vegetable or animal material in soil, from the bodies of
dead plants and animals, or even from foods prepared for man.
Fungi which feed upon dead organic material are known as sap
rophytes. Examples are the mushrooms, the yeasts, molds, and
some bacteria, of which more will be learned later.

Some Parasitic Fungi. Other fungi (and we will find this
applies to some animals as well) prefer living plants or animals
for their food. Thus a tiny
plant, recently introduced
into this country, known
as the chestnut canker, is
killing our chestnut trees by
the thousands in the eastern
part of the United States.
It produces millions of tiny
reproductive cells known as
spores; these spores, blown
about by the wind, light on
the trees, sprout, and send
in under the bark a thread
like structure which sucks
in the food circulating in
the living cells, eventually
causing the death of the
tree. A plant or animal
which lives at the expense of
another living plant or ani
mal is called a parasite. The chestnut canker is a dangerous
parasite. Later we shall see that animal and plant parasites de
stroy yearly crops and trees valued at hundreds of millions of
dollars and cause untold misery and suffering to humanity.

Chestnut trees in a New York City park ;
killed by a parasite, the chestnut canker.

132

PLANTS WITHOUT CHLOROPHYLL

Another fungus which does much harm to the few trees found
in large towns and cities is the shelf or bracket fungus. The part
of the body visible on the tree looks like a shelf or bracket, hence

the name. This bracket is in
reality the reproductive part of
the plant; on its lower surface
are formed millions of little
bodies called spores. These
spores are capable, under favor
able conditions, of reproducing
new plants. The true body of
the plant, a network of threads,
is found under the bark. This
fungus begins its life as a spore
in some part of the tree which
has become diseased or broken.
Cnce established, it spreads
rapidly. There is no remedy
except to kill the tree and burn
it, so as to destroy the spores.
Many fine trees, sound except
for a slight bruise or other in
jury, are annually infected and eventually killed. In cities thou
sands of trees become infected through careless hitching of horses
so that the horse may gnaw the tree, thus exposing a fresh surface
on which spores may obtain lodgment and grow (see page 115).

Suggestions for Field Work. A field trip to a park or grove near
home may show the great destruction of timber by this means. Count the
number of perfect trees in a given area. Compare it with the number of
trees attacked by the fungus. Does the fungus appear to be transmitted
from one tree to another near at hand ? In how many instances can you
discover the point where the fungus first attacked the tree ?

Fungi of our Homes. But not all fungi are wild. Some have
become introduced into our homes and these live on food or other
materials. These plants are very important because of their relation
to life in a town or crowded city. 1

1 Experiments on conditions favorable to growth of mold should be introduced here.

Shelf fungi.
(Photographed by W. C. Barbour.)

PLANTS WITHOUT CHLOROPHYLL 133

The Growth of Bread Mold. If a piece of moist bread is
exposed to the air of the schoolroom, or in your own kitchen for a
few minutes and then covered with a glass tumbler and kept in a
warm place, in a day or two a fuzzy whitish growth will appear on
the surface of the bread. This growth shortly turns black. If we
now examine a little piece of the
bread with a lens or low-powered
microscope, we find a tangled
mass of .threads (the mycelium)
covering the surface of the bread.
From this mass of threads pro
ject tiny upright stalks bearing
round black bodies, the fruit.
Little rootlike structures known
as rhizoids dip down into the
bread, and absorb food for its
threadlike body. The upright
threads with the balls at the end contain many tiny bodies
called spores. These spores have been formed by the division of
the protoplasm making up the fruiting bodies into many separate
cells. When grown under favorable conditions, the spores will
produce more mycelia, which in turn bear fruiting bodies.

Physiology of the Growth of Mold. Molds, in order to grow
rapidly, need oxygen, moisture, and moderate heat. They seem
to prefer dark, damp places where there is not a free circula
tion of air, for if the bell jar is removed from growing mold
for even a short time, the mold wilts. Too great or very little
heat will prevent growth and kill everything except the spores.
They obtain their food from the material on which they live.
This they are able to do by means of digestive enzymes given out
by the rootlike parts, by means of which the molds cling to the
bread. These digestive enzymes change the starch of the bread to
sugar and the protein to a soluble form which will pass by osmosis
into cells of the mold. Thus the mold is able to absorb food
material. These foods are then used to supply energy and make
protoplasm. This seems to be the usual method by which sapro
phytes make use of the materials on which they live.

134 PLANTS WITHOUT CHLOROPHYLL

What can Molds live On? We have seen that black mold
lives upon bread. We would find that it or some other mold
(e.g. green or blue mold) live upon decaying or overripe fruit,
apples, peaches, and plums being especially susceptible to their
growth. Molds feed upon all cakes or breads, upon meat, chees-e,
and many raw vegetables. They are almost sure to grow upon
flour if it is allowed to get damp. Moisture seems necessary for
their growth. Jelly is a substance particularly favorable to molds
for this reason. Shoes, leather, cloth, paper, or even moist wood
will give food enough to support their growth. At least one
troublesome disease, ringworm, is due to the growth of molds
in the skin.

What Mold does to Foods. Mold usually changes the taste
of the material it grows upon, rendering it " musty " and some
times unfit to eat. Eventually it will spoil food completely be
cause decay sets in. Decay, as we will see later, is not entirely
due to mold growth, but is usually caused by another group of
organisms, the bacteria. Molds, however, in feeding do cause
chemical changes which result in decay or putrefaction. Some
molds are useful. They give the flavor to Roquefort, Gorgonzola,
Camembert, and Brie cheeses. But on the whole molds are pests
which the housekeeper wishes to get rid of.

How to prevent Molds. 1 As we have seen, moisture is favorable
for mold growth ; conversely, dryness is unfavorable. Inasmuch
as the spores of mold abound in the air, materials which cannot be
kept dry should be covered. Jelly after it is made should at once
be tightly covered with a thin layer of paraffin, which excludes the
air and possible mold spore's. Or waxed paper may be fastened
over the surface of the jelly so as to exclude the spores. To pre
vent molds from attacking fresh fruit, the surface of the fruit
should be kept dry and, if possible, each piece of fruit should be
wrapped in paper. Why? Heating with dry heat to 212 for
a few moments will kill any mold spores that happen to be in
food. Moldy food, if heated after removing surface on which the
mold grew, is perfectly good to eat.

1 An experiment to show conditions unfavorable for growth of molds should be
shown at this point.

PLANTS WITHOUT CHLOROPHYLL 135

Dry dusting or sweeping will raise dust, which usually contains
mold spores. Use a dampened broom or dust cloth frequently in
the kitchen if you wish to preserve foods from molds.

Other Moldlike Fungi. Mildews are near relatives of the
molds found in our homes. They may attack leather, cloth, etc.,
in a damp house. Other allied forms may do damage to living
plants. Some of these live upon the lilac, rose, or willow. These
fungi do not penetrate the host plant to any depth, for they obtain
their food from the outer layer of cells in the leaf of their host and
cover the leaves with the whitish threads of the mycelium.
Hence they may be killed by means of applications of some
fungus-killing fluid, as Bordeaux mixture. 1 Among the useful
plants preyed upon by mildews are the plum, cherry, and peach
trees. (The diseases known as black knot and peach curl are
thus caused.) Another important member of this group is the
tiny parasite found on rye and other grains, which gives us the
drug ergot.

Among other parasitic fungi are rusts and smuts. Wheat rust
is probably the most destructive parasitic fungus. Indirectly this
parasite is of considerable importance to the citizen of a great city
because of its effect upon the price of wheat.

YEASTS IN THEIR RELATION TO MAN

Fermentation. It is of common knowledge to country boys
or girls that the juice of fresh apples, grapes, and some other
fruits, if allowed to stand exposed to the air for a short time will
ferment. That is, the sweet juice will begin to taste sour and
to have a peculiar odor, which we recognize as that of alcohol.
The fermenting juice appears to be full of bubbles which rise to
the surface. If we collect enough of these bubbles of gas to make
a test, we find it to be carbon dioxide.

Evidently something changed some part of the apple or grape,
the sugar, (C 6 Hi 2 O 6 ), into alcohol, 2 (C 2 H 6 O), and carbon dioxide,
2 (CO 2 ) . This chemical process is known as fermentation.

1 See Goff and Mayne, First Principles of Agriculture, page 59, for formula of
Bordeaux mixture.

136

PLANTS WITHOUT CHLOROPHYLL

Yeast causes Fermentation. Let us now take a compressed
yeast cake, shake up a small portion of it in a solution of mo
lasses and water, and fill a fermentation
tube with the mixture. Leave the tube
in a warm place overnight. In the
morning a gas will be found to have
been collected in the closed end of the
tube (see Figure on page 138). The
taste and odor of the liquid shows
alcohol to be present, and the gas, if
tested, is proven carbon dioxide.
Evidently yeast causes fermentation.
What are Yeasts ? If now part of

Apparatus to show effect of

fermentation. N, molasses, the liquid from the fermentation tube
water and yeast plants ; c, which con tains the settlings be drawn

bubbles of carbon dioxide.

on, a drop placed on a slide and a little

weak iodine added and the mixture examined under the compound
microscope, two kinds of structures will be found (see Figure below),
starch grains which are stained
deep blue, and other smaller
ovoid structures of a brownish
yellow color. The latter are
yeast plants.

Size and Shape, Manner of
Growth, etc. The common
compressed yeast cake contains
millions of these tiny plants.
In its simplest form a yeast
plant is a single cell. The
shape of such a plant is ovoid,
each cell showing under the
microscope the granular ap- Yeast and starch s rains - Notice that the

. starch grains around which are clustered

pearance OI the protoplasm OI yeast cells have been rounded off by the

which it is formed. Look for yeast P lants - How do you account

,. ,. for this?

tiny clear areas in the cells ;

these are vacuoles, or spaces filled with fluid. The nucleus is hard

to find in a yeast cell. Many of the cells seem to have others

PLANTS WITHOUT CHLOROPHYLL 137

attached to them, sometimes there being several in a row. Yeast
cells reproduce very rapidly by a process of budding, a part of the
parent cell forming one or more smaller daughter cells which even
tually become free from the parent.

Conditions favorable to growth of Yeast. Experiment. Label three
pint fruit jars A, B, and C. Add one fourth of a compressed yeast cake to
two cups of water containing two tablespoonfuls of molasses or sugar.
Stir the mixture well and divide it into three equal parts and pour them
into the jars. Place covers on the jars. Put jar A in the ice box on the
ice, and jar B over the kitchen stove or near a radiator ; pour the contents
of jar C into a small pan and boil for a few minutes. Pour back into C,
cover and place it next to B. After forty-eight hours, look to see if any
bubbles have made their appearance in any of the jars. If the experiment
has been successful, only jar B will show bubbles. After bubbles have
begun to appear at the surface, the fluid in jar B will be found to have a
sour taste and will smell unpleasantly. The gas which rises to the surface,
if collected and tested, will be found to be carbon dioxide. The contents
of jar B have fermented. Evidently, the growth of yeast will take place
only under conditions of moderate warmth and moisture.

Carbohydrates necessary to Fermentation. Sugar must be
present in order for fermentation to take place. The wild yeasts
cause fermentation of the apple or grape juice because they live
on the skin of the apple or grape. Various peoples recognize
this when they collect the juice of certain fruits and, exposing
it to the air, allow it to ferment. Such is the saki or rice wine of
the Japanese, the tuba or sap of the coconut palm of the Filipinos
and the pulque of the Mexicans.

Beer and Wine Making. Brewers' yeasts are cultivated with
the greatest care; for the different flavors of beer seem to de
pend largely upon the condition of the yeast plants. Beer is
made in the following manner. Sprouted barley, called malt, in
which the starch of the grain has been changed to grape sugar by
digestion, is killed by drying in a hot kiln. The malt is dissolved
in water, and hops are added to give the mixture a bitter taste.
Now comes the addition of the yeast plants, which multiply rapidly
under the favorable conditions of food and heat. Fermentation
results on a large scale from the breaking down of the grape sugar ;

138 PLANTS WITHOUT CHLOROPHYLL

the alcohol remaining in the fluid, and the carbon dioxide passing
off into the air. At the right time the beer is stored either in
bottles or casks, but fermentation slowly continues, forming car
bon dioxide in the bottles. This gives the sparkle to beer when it
is poured from the bottle.

In wine making the wild yeasts growing on the skin of the grapes
set up a slow fermentation. It takes several weeks before the
wine is ready to bottle. In sparkling wines a second fermentation
in the bottles gives rise to carbon dioxide in such quantity as to
cause a decided frothing when the bottle is opened.

Commercial Yeast. Cultivated yeasts are now supplied in
the home as compressed or dried yeast cakes. In both cases the
yeast plants are mixed with starch and other substances and
pressed into a cake. But the compressed yeast cake must be used
fresh, as the yeast plants begin to die rapidly after two or three
days. The dried yeast cake, while it contains a much smaller
number of yeast plants, is nevertheless probably more reliable if
the yeast cannot be obtained fresh.

The cut illustrates
an experiment that
shows how yeast
plants depend upon
food in order to grow.
In each of three fer
mentation tubes were
placed an equal
amount of a com
pressed yeast cake.
Then tube a was
filled with distilled
water, tube b with a
solution of glucose
and water, and tube
c with a nutrient solution containing nitrogenous matter as well
as glucose. The quantity of gas (CO 2 ) in each tube is an index of
the amount of growth of the yeast cells. In which tube did the
greatest growth take place ?

PLANTS WITHOUT CHLOROPHYLL 139

Bread Making. Most of us are familiar with the process of
bread making. The materials used are flour, milk or water or
both, salt, a little sugar to hasten the process of fermentation, or
" rising" as it is called, some butter or lard, and yeast.

After mixing the materials thoroughly by a process called " knead
ing, "the bread is put aside in a warm place (about 75 Fahrenheit)
to " rise." If we examine the dough at this time, we find it filled
with holes, which give the mass a spongy appearance. The yeast
plants, owing to favorable conditions, have grown rapidly and filled
the cavities with carbon dioxide. Alcohol is present, too, but this
is evaporated when the dough is baked. The baking cooks the
starch of the bread, drives off the carbon dioxide and alcohol, and
kills the yeast plants, besides forming a protective crust on the loaf.

Sour Bread. If yeast cakes are not fresh, sour bread may result
from their use. In such yeast cakes there are apt to be present
other tiny one-celled plants, known as bacteria. Certain of these
plants form acids after fermentation takes place. The sour taste
of the bread is usually due to this cause. The remedy would
be to have fresh yeast, to have good and fresh flour, and to have
clean vessels with which to work.

Importance of Yeasts. Yeasts in their relation to man are
thus seen to be for the most part useful. They may get into
canned substances put up in sugar and cause them to " work,"
giving them a peculiar flavor. But they can be easily killed by
heating to the temperature of boiling. On the other hand, yeast
plants are necessary for the existence of all the great industries
which depend upon fermentation. And best of all they give us
leavened bread, which has become a necessity to most of mankind.

BACTERIA IN THEIR RELATION TO MAN

What Bacteria do and Where They May be Found. A walk
through a crowded city street on any warm day makes one fully
alive to odors which pervade the atmosphere. Some of these un
pleasant odors, if traced, are found to come from garbage pails,
from piles of decaying fruit or vegetables, or from some butcher
shop in which decayed meat is allowed to stand. This character
istic phenomena of decay is one of the numerous ways in which

140

PLANTS WITHOUT CHLOROPHYLL

we can detect the presence of bacteria. These tiny plants, " man's
invisible friends and foes," are to be found " anywhere, but not
everywhere," in nature. They swarm in stale milk, in impure
water, in soil, in the living bodies of plants and animals and in
their dead bodies as well. Most " catching " diseases we know
to be caused directly by them ; the processes of decay, souring of
milk, acid fermentation, the manufacture of nitrogen for plants

are directly or indirectly due to
their presence. It will be the pur
pose of the next paragraphs to
find some of the places where
bacteria may be found and how
we may know of their presence.

How we catch Bacteria to Study
Them. To study bacteria it is
first necessary to find some ma
terial in which they will grow, then
kill all living matter in this food
material by heating to boiling
point (212) for half an hour or
more (this is called sterilization),
and finally protect the culture
medium, as this food is called, from
other living things that might
grow upon it.

One material in which bacteria seem to thrive is a mixture of
beef extract, digested protein and gelatine or agar-agar, the latter
a preparation derived from seaweed. This mixture, after ster
ilization, is poured into flat dishes with loose-fitting covers.
These petri dishes, so called after their inventor, are the traps
in which we collect and study bacteria.

Where Bacteria might Grow. Expose a number of these steril
ized dishes, each for the same length of time, to some of the fol
lowing conditions :

(a) exposed to the air of the schoolroom.

(6) exposed in the halls of the school while pupils are passing.

A steam sterilizer.

PLANTS WITHOUT CHLOROPHYLL

141

(d) exposed at the level of a dirty and much-used city street.

(e) exposed at the level of a well-swept and little-used city street.
(/) exposed in a city park.

(g) exposed in a factory building.

(h) dirt from hands placed in dish.

(i) rub interior of mouth with finger and touch surface of dish.

(j) touch surface of dish with decayed vegetable or meat.

(k) touch surface of dish with dirty coin or bill.

(I) place in dish two or three hairs from boy's head.

This list might be prolonged indefinitely.

Now let us place all of the dishes together in a moderately warm
place (a closet in the schoolroom will do) and watch for results.
After a day or two little spots,
brown, yellow, white, or red, will
begin to appear. These spots, which
grow larger day by day, are colonies
made up of millions of bacteria.
But probably each colony arose
from a single bacterium which got
into the dish when it was exposed
to the air.

How we may isolate Bacteria of
Certain Kinds from Others. In
order to get a number of bacteria
of a given kind to study, it becomes
necessary to grow them in what is

known as a pure culture. This is done by first growing the
bacteria in some medium such as beef broth, gelatin, or on
potato. 1 Then as growth follows the colonies of bacteria appear
in the culture media or the beef broth becomes cloudy. If now
we wish to study one given form, it becomes necessary to isolate
them from the others. This is done by the following process :
a platinum needle is first passed through a flame to sterilize it ;
that is, to kill all living things that may be on the needle point.

1 For directions for making a culture medium, see Hunter, Laboratory Problems
in Civic Biology. Culture tubes may be obtained, already prepared, from Parke,
Davis, and Company or other good chemists.

Colonies of bacteria growing in
a petri dish.

142

PLANTS WITHOUT CHLOROPHYLL

A pure culture of bacteria. Notice
that the bacteria are all the same
size and shape.

Then the needle, which cools very quickly, is dipped in a colony
containing the bacteria we wish to study. This mass of bacteria

is quickly transferred to another
sterilized plate, and this plate is
immediately covered to prevent
any other forms of bacteria from
entering. When we have suc
ceeded in isolating a certain kind of
bacterium in a given dish, we are
said to have a pure culture. Hav
ing obtained a pure culture of
bacteria, they may easily be studied
under the compound microscope.

Size and Form. In size, bac
teria are the most minute plants
known. A bacterium of average
size is about ywoo of an inch in
length, and perhaps Broriinr of an
inch in diameter. Some species

are much larger, others smaller. A common spherical form is
STrhrTr f an mc h in diameter. They are so small that several million
are often found in a single drop of impure water or sour milk.
Three well-defined forms of bacteria are recognized : a spherical
form called a coccus, a rod-shaped bacterium, the bacillus, and a
spiral form, the spirillum. Some bacteria are capable of move
ment when living in a fluid. Such movement is caused by tiny
lashlike threads of protoplasm called flagella. The flagella pro
ject from the body, and by a rapid movement cause locomotion
to take place. Bacteria reproduce with almost incredible rapidity.
It is estimated that a single bacterium, by a process of division
called fission, will give rise to over 16,700,000 others in twenty-four
hours. Under unfavorable conditions they stop dividing and form
rounded bodies called spores. This spore is usually protected by
a wall and may withstand very unfavorable conditions of dryness or
heat ; even boiling for several minutes will not kill some forms.

Where Bacteria are most Numerous. As the result of our
experiments, we can make some generalizations concerning the

PLANTS WITHOUT CHLOROPHYLL

143

presence of bacteria in our own environment. They are evidently
present in the air, and in greater quantity in air that is moving
than quiet air. Why?
That they stick to par
ticles of dust can be
proven by placing a
little dust from the
schoolroom in a culture
dish. Bacteria are pres
ent in greater numbers
where crowds of people
live and move, the air
from dusty streets of a
populous city contains
many more bacteria
than does the air of a
village street. The air
of a city park contains
relatively few bacteria
as compared with the
near-by street. The air
of the woods or high
mountains fewer still.
Why ? Our previous
experiment has shown
that dirt on our hands,
the mouth and teeth,
decayed meat and vege
tables, dirty money, the
very hairs of our head are
all carriers of bacteria.

Fluids the Favorite Home of Bacteria. Tap water, stand
ing water, milk, vinegar, wine, cider all can be proven to con
tain bacteria by experiments similar to those quoted above.
Spring or artesian well water would have very few, if any,
bacteria, while the same quantity of river water, if it held any
sewage, might contain untold millions of these little organisms.

A figure to show the relative size and shape of
(1) a green mold, (2) yeast cells, and (3) differ
ent forms of bacteria; B, bacillus; C, coccus;
S, spirillum forms. The yeast and bacteria are
drawn to scale, they are much enlarged in pro
portion to the green mold, being actually much
smaller than the mold spores seen at the top of
the picture.

144 PLANTS WITHOUT CHLOROPHYLL

Foods preferred by Bacteria. If bacteria are living and
contain no chlorophyll, we should expect them to obtain protein
food in order to grow. Such is not always the case, for some
bacteria seem to be able to build up protein out of simple inorganic
nitrogenous substances. If, however, we take several food sub
stances, some containing much protein and others not so much, we

will find that the bacteria cause
decay in the proteins almost
at once, while other food sub
stances are not always attacked
by them.

What Bacteria do to Foods.
When bacteria feed upon a
protein they use part of the
materials in the food so that it
falls to pieces and eventually
rots. The material left behind
after the bacteria have finished
their meal is quite different
from its original form. It is

Growth of bacteria in a drop of impure .

water allowed to run down a sterilized broken down by the action ol

culture in a dish. the bacteria into gases, fluids,

and some solids. It has a characteristic " rotten" odor and it
has in it poisons which come as a result of the work of the bac
teria. These poisonous wastes, called ptomaines, we shall learn
more about later.

Conditions Favorable and Unfavorable to the Growth of Bacteria.
Moisture and Dryness. Experiment. Take two beans, remove the skins ,
crush one, soak the second bean overnight and then crush it. Place in
test tubes, one dry, the second with water. Leave in a warm place two
or three days, then smell each tube. In which is decay taking place ? In
which tube are bacteria at work ? How do you know ?

Moisture. Moisture is an absolute need for bacterial growth,
consequently keeping material dry will prevent the growth of
germs upon its surface. Foods, in order to decay, must contain
enough water to make them moist. Bacteria grow most freely
in fluids.

PLANTS WITHOUT CHLOROPHYLL 145

Light. If we cover one half of a petri dish in which bacteria
are growing with black paper and then place the dish in a light
warm place for a few days, the growth of bacteria in the light part
of the dish will be found to be checked, while growth continues in
the covered part. It is a matter of common knowledge that disease
germs thrive where dirt and darkness exist and are killed by any
long exposure to sunlight. This shows us the need of light in our
homes, especially in our bedrooms.

Air. We have seen that plants need oxygen in order to per
form the work that they do. This is equally true of all animals.
But not all bacteria need air to live ; in fact, some are killed by
the presence of air. Just how these organisms get the oxygen
necessary to oxidize their food is not well understood. The fact
that some bacteria grow without air makes it necessary for us to
use the one sure weapon we have for their extermination, and that
is heat.

Heat. Experiment, Take four cultures containing bouillon, in
oculate each tube with bacteria and plug each tube with absorbent cotton.
Place one tube in the ice box, a second tube in a dark closet at a moderate
temperature, a third in a warm place (about 100 Fahrenheit), and boil the
contents of the fourth tube for ten minutes, then place it with tube num
ber two. In which tubes does growth take place most rapidly? Why?

Bacteria grow very slowly if at all in the temperature of an ice
box, very rapidly at the room temperature of from 70 to 90
and much less rapidly at a higher temperature. All bacteria
except those which have formed spores can be instantly killed as
soon as boiling point is reached, and most spores are killed by a few
minutes boiling.

Sterilization. The practical lessons drawn from sterilization
are many. We know enough now to boil our drinking water if
we are uncertain of its purity ; we sterilize any foods that we
believe might harbor bacteria, and thus keep them from spoiling.
The industry of canning is built upon the principle of sterilization.

Canning. Canning is simply a method by which first the
bacteria in a substance are killed by heating and then the
substance is put into vessels into which no more bacteria may
gain entrance. This is usually done at home by boiling the fruit

HUNTER, CIV. BI. 10

146

PLANTS WITHOUT CHLOROPHYLL

or vegetable to be canned either in salt and water or with sugar
and water, either of which substances aids in preventing the growth
of bacteria. The time of boiling will be long or short, depending
upon the materials to be canned. Some vegetables, as peas, beans,
and corn, are very difficult to can, probably because of spores of
bacteria which may be attached to them. Fruits, on the other
hand, are usually much easier to preserve. After boiling for the
proper time, the food, now free from all bacteria, must be put into
jars or cans that are themselves absolutely sterile or free from
germs. This is done by first boiling the jars, then pouring the
boiling hot material into the hot jars and sealing them so as to
prevent the entrance of bacteria later.

Uses of Canning. Canning as an industry is of immense im
portance to mankind. Not only does it provide him with fruits
and vegetables at times when he could not otherwise get them,
but it also cheapens the cost of such things. It prevents the waste

of nature's products at a time
when she is most lavish with
them, enabling man to store
them and utilize them later.
Canning has completely
changed the life of the sailor
and the soldier, who in former
times used to suffer from vari
ous diseases caused by lack of
a proper balance of food.

Pasteurization. Milk is one
of the most important food
supplies of a great city. It is
also one of the most difficult
supplies to get in good condi
tion. This is in part due to
the fact that milk is produced

Pasteurizing milk .^Why should this ^ 1()ng distanceg from the city

and must be brought first from

farms to the railroads, then shipped by train, again taken to the
milk supply depot by wagon, there bottled, and again shipped

PLANTS WITHOUT CHLOROPHYLL 147

by delivery wagons to the consumers. When we remember that
much of the milk used in New York City is forty-eight hours
old and when we realize that bacteria grow very rapidly in milk,
we see the need of finding some way to protect the supply so as
to make it safe, particularly for babies and young children.

This is done by pasteurization, a method named after the
French bacteriologist Louis Pasteur. To pasteurize milk we
heat it to a temperature of not over 170 Fahrenheit for from
ten minutes to half an hour. By such a process all harmful germs
will be killed and the keeping qualities of the milk greatly length
ened. Most large milk companies pasteurize their city supply by
a rapid pasteurization at a much higher temperature, but this
method slightly changes the flavor of the milk.

Cold Storage. Man has also come to use cold to keep bacteria
from growing in foods. The ice box at home and cold storage on a
larger scale enables one to keep foods for a more or less lengthy
period. If food is frozen, as in cold storage, it might keep without
growth of bacteria for years. But fruits and vegetables cannot
be frozen without spoiling their flavor. And all foods after freez
ing seem particularly susceptible to the bacteria of decay. For
that reason products taken from cold storage must be used at once.

Ptomaines. Many foods get their flavor from the growth of
molds or bacteria in them. Cheese, butter, the gamey taste of
certain meats, the flavor of sauerkraut, are all due to the work of
bacteria. But if bacteria are allowed to grow so as to become
very numerous, the ptomaines which result from their growth in
foods may poison the person eating such foods. Frequently
ptomaine poisoning occurs in the summer time because of the rapid
growth of bacteria. Much of the indigestion and diarrhoea which
attack people during the summer is doubtless due to this kind of
poisoning.

Preservatives. 1 This leads us to ask if we may not preserve
food in ways other than those mentioned so as to protect our
selves from danger of ptomaine poisoning. Many substances
check the development of bacteria and in this way they preserve

1 Perform experiment here to determine the value of different preservatives.
Use sugar, salt, vinegar, boracic acid, benzoic acid, formaldehyde, and alcohol.

148 PLANTS. WITHOUT CHLOROPHYLL

the food. Preservatives are of two kinds, those harmless to man
and those that are poisonous. Of the former, salt and sugar are
examples ; of the latter, formaldehyde and possibly benzoic acid.

Sugar. We have noted the use of sugar in canning. Small
amounts of sugar will be readily attacked by yeasts, molds, and
bacteria, but a 40 to 50 per cent solution will effectually keep out
bacteria. Preserves are fruits boiled in about their own weight of
sugar. Condensed milk is preserved by the sugar added to it ; so
are candied and, in part, dried fruits.

Salt. Salt has been used for centuries to keep foods. Meats
are smoked, dried, and salted ; some are put down in strong salt
solutions. Fish, especially cod and herring, are dried and salted.
The keeping of butter is also due to the salt mixed with it. Vine
gar is another preservative. It, like salt, changes the flavor of
materials kept in it and so cannot come into wide use. Spices
are also used as preservatives.

Harmful Preservatives. Certain chemicals and drugs, used as
preservatives, seem to be on the border line of harmfulness.
Such are benzoic acid, borax, or boracic acid. Such drugs may
be harmless in small quantities, but unfortunately in canned goods
we do not always know the amount used. The national govern
ment in 1906 passed what is known as the Pure Food Law, which
makes it illegal to use any of these preservatives (excepting ben
zoic acid in very small amounts). Food which contains this
preservative will be so labeled and should not be given to chil
dren or people with weak digestion. Unfortunately people do
not always read the labels and thus the pure food law is ineffec
tive in its working. Infrequently formaldehyde or other pre
servatives are used in milk. Such treatment renders milk unfit
for ordinary use and is an illegal process.

Disinfectants. 1 Frequently it becomes necessary to destroy
bacteria which cause diseases of various kinds. This process is
called disinfecting. The substances commonly used are carbolic
acid, formalin or formaldehyde, lysol, and bichloride of mercury.

1 Experiment to determine the most effective disinfectants. Use tubes of
bouillon containing different strength solutions of formaldehyde, lysol, iodine, car
bolic acid, and bichloride of mercury. Results. Conclusions.

PLANTS WITHOUT CHLOROPHYLL

149

ORGANIC

Of these, the- last named is the most powerful as well as the most
dangerous to use. As it attacks metal, it should not be used in a
metal pail or dish. It is commonly put up in tablets which are
mixed to form a 1 to 1000 solution. Such tablets should be care
fully safeguarded because of possible accidental poisoning.

Formaldehyde used in liquid form is an excellent disinfectant.
When burned in a formalin candle, it sets free an intensely
pungent gas which is often used for disinfecting sick rooms after
the patient has been removed.

Carbolic acid is perhaps the best disinfectant of all. If used
in a solution of about 1 part to 25 of water, it will not burn the skin.
It is of particular value
to disinfect skin wounds,
as it heals as well as
cleanses when used in a
weak solution. Its rather
pleasant odor makes it
useful to cover up un
pleasant smells of the
sick room.

The fumes of burning
sulphur, which are so
often used for disinfect
ing, are of little real
value.

Bacteria cause Decay.
Let us next see in
what ways the bacteria
directly influence man
upon the earth. Have
you ever stopped to con
sider what life would be
like on the earth if things did not decay? The sea would soon be
filled and the land covered with dead bodies of plants and animals.
Conditions of life would become impossible and living things on
the earth would cease to exist.

Fortunately, bacteria cause decay. All organic matter, in

This shows how orgaui3 matter is broken down
by bacteria so it may be used again by green
plants.

150

PLANTS WITHOUT CHLOROPHYLL

whatever form, is sooner or later decomposed by the action of
untold millions of bacteria which live in the air, water, and soil.
These soil bacteria are most numerous in rich damp soils contain
ing large amounts of organic material. They are very numerous
around and in the dead bodies of plants and animals. To a con
siderable degree, then, these bacteria are useful in feeding upon
these dead bodies, which otherwise would soon cover the surface
of the earth to the exclusion of everything else. Bacteria may
thus be scavengers. . They oxidize organic materials, changing
them to compounds that can be absorbed by plants and used

in building protoplasm. With
out bacteria and fungi it would
be impossible for life to exist
on the earth, for green plants
would be unable to get the
raw food materials in forms
that could be used in making
food and living matter. In
this respect bacteria are of the
greatest service to mankind.

Relation to Fermentation.
They may incidentally, as a
result of this process of decay,
continue the process of fer
mentation begun by the yeasts.
In making vinegar the yeasts
first make alcohol (see page 135) which the bacteria change to
acetic acid. The lactic acid bacteria, which sour milk, changing
the milk sugar to an acid, grow very rapidly in a warm tempera
ture ; hence milk which is cooled immediately and kept cool or
which is pasteurized and kept in a cool place will not sour readily.
Why? These same lactic acid bacteria may be useful when they
sour the milk for the cheese maker.

Other Useful Bacteria. Certain bacteria give flavor to cheese
and butter, while still other bacteria aid in the " curing " of
tobacco, in the production of the dye indigo, in the preparation of
certain fibers of plants for the market, as hemp, flax, etc., in the

*&** O_ V c

Microscopic appearance of ordinary milk,
showing fat globules and bacteria
which cause the souring of milk.

PLANTS WITHOUT CHLOROPHYLL

151

rotting of animal matter from the skeletons of sponges, and in the
process of tanning hides to make leather.

Nitrogen-fixing Bacteria. Still other bacteria, as we have
seen before, " change over " nitrogen in organic material in the
soil and even the free nitrogen of the air so that it can be used by
plants in the form of a compound of nitrogen. The bacteria

living in tubercles on the

roots of clover, beans, peas,
etc., have the power of
thus " fixing " the free
nitrogen in the air found
between particles of soil.
This fact is made use of by
farmers who rotate their
crops, growing first a crop
of clover or other plants
having root tubercles,
which produce the bac
teria, then plowing these
in and planting another
crop, as wheat or corn, on
the same area. The latter
plants, making use of the
nitrogen compounds there,
produce a larger crop than
when grown in ground
containing less nitrogenous
material.

Bacteria cause Disease. The most harmful bacteria are those
which cause diseases of plants and animals. Certain diseases of
plants blights, rots, and wilts are of bacterial nature. These
do much annual damage to fruits and other parts of growing
plants useful to man as food. But by far the most important
are the bacteria which cause disease in man. They accomplish
this by becoming parasites in the human body. Millions upon
millions of bacteria exist in the human body at all times in the
mouth, on the teeth, in the blood, and especially in the lower

A field of alfalfa, a plant which harbors the
nitrogen-fixing bacteria.

152 PLANTS WITHOUT CHLOROPHYLL

part of the food tube. Some in the food tube are believed to be
useful, some harmless, and some harmful ; others in the mouth
cause decay of the teeth, while a few kinds, if present in the
body, may cause disease.

It is known that bacteria, like other living things, feed and give
off organic waste from their own bodies. This waste, called a toxin,

Tubercles on the roots of the soy bean. They contain the nitrogen-fixing bacteria.
(Fletcher's Soils.) Copyright by Doubleday, Page and Company.

is poison to the host on which the bacteria live, and it is usually
the production of this toxin that causes the symptoms of disease.
Some forms, however, break down tissues and plug up the small
blood vessels, thus causing disease.

Diseases caused by Bacteria. It is estimated that bacteria
cause annually over 50 per cent of the deaths of the human race.
As we will later see, a very large proportion of these diseases
might be prevented if people were educated sufficiently to
take the proper precautions to prevent their spread. These pre
cautions might save the lives of some 3,000,000 of people yearly
in Europe and America. Tuberculosis, typhoid fever, diphtheria,
pneumonia, blood poisoning, syphilis, and a score of other germ
diseases ought not to exist. A good deal more than half of the
present misery of this world might be prevented and this earth
made cleaner and better by the cooperation of the young people
now growing up to be our future home makers.

How we take Germ Diseases. Germ or contagious diseases
either enter the body by way of the mouth, nose, or other body

PLANTS WITHOUT CHLOROPHYLL

153

openings, or through a

break in the'skin. They

may be carried by means

of air, food, or water,

but are usually trans

mitted directly from the

person who has the

disease to a well per

son. This may be done

through personal con

tact or by handling

articles used by the

sick person or by drink

ing or eating foods

which have received

some of the germs.

From this it follows

that if we know the

methods by which a

given disease is communicated, we may protect ourselves from it

and aid the civic authorities in preventing its spread.

Tuberculosis. The one disease responsible for the greatest

number of deaths perhaps one seventh of the total on the

globe is tuberculosis.
It is estimated that of
all people alive in the
United States to-day,
5,000,000 will die of
this disease. But this
disease is slowly but
surely being overcome.
It is believed that
within perhaps one
hundred years, with the
aid of good laws and

livino- it will
living, it Will

A single cell scraped from the roof of the mouth
and highly magnified. The little dots are
bacteria, most of which are harmless. Notice
the comparative size of bacteria and cell.

Deaths from tuberculosis compared with other
contagious diseases in the city of New York

in 1908,

be almost extinct.

154

PLANTS WITHOUT CHLOROPHYLL

-400

-300

Tuberculosis is caused by the growth of bacteria, called the
tubercle bacilli, within the lungs or other tissues of the human body.
Here they form little tubers full of germs, which close up the deli
cate air passages in the lungs, while in other tissues they give rise
to hip-joint disease, scrofula, lupus, and other diseases, depending
on the part of the body they attack. Tuberculosis may be con
tracted by taking the bacteria into the throat or lungs or possi-

bly by eating meat or

drinking milk from
tubercular cattle. Es
pecially is it communi
cated from a consump
tive to a well person by
kissing, by drinking or
eating from the same
cup or plate, using the
same towels, or in com
ing in direct contact
with the person having
the germs in his body.
Although there are al
ways some of the germs
in the air of an ordinary
city street, and though
we may take some of
these germs into our
bodies at any time, yet
the bacteria seem able
to gain a foothold only
under certain conditions. It is only when the tissues are in a
worn-out condition, when we are " run down," as we say, that
the parasite may obtain a foothold in the lungs. Even if the
disease gets a foothold, it is quite possible to cure it if it is
taken in time. The germ of tuberculosis is killed by exposure
to bright sunlight and fresh air. Thus the course of the disease
may be arrested, and a permanent cure brought about, by
a life in the open air, the patient sleeping out of doors, taking

too

1850 I860 18TO 1880 1890 19001906

This curve shows a decreasing death rate from
tuberculosis. . Explain.

PLANTS WITHOUT CHLOROPHYLL

155

plenty of nourishing food and very little exercise. See also
Chapter XXIV.

Typhoid Fever. One of the most common germ diseases in
this country and Europe is typhoid fever. This is a disease which
is conveyed by means of water and food, especially milk, oysters,
and uncooked vegetables. Typhoid fever germs live in the intes
tine and from there get into the blood and are carried to all parts
of the body. A poison which they give off causes the fever so
characteristic of the disease. The germs multiply very rapidly

This figure shows how sewage from a cesspool (c) might get into the
water supply: Im, layer of rock; w, wash water.

in the intestine and are passed off from the body with the excreta
from the food tube. If these germs get into the water supply
of a town, an epidemic of typhoid will result. Among the recent
epidemics caused by the use of water containing typhoid germs
have been those in Butler, Pa., where 1364 persons were made ill;
Ithaca, N. Y., with 1350 cases ; and Watertown, N. Y., where
over 5000 cases occurred. Another source of infection is milk.
Frequently epidemics have occurred which were confined to users
of milk from a certain dairy. Upon investigation it was found
that a case of typhoid had occurred on the farm where the milk
came from, that the germs had washed into the well, and that this
water was used to wash the milk cans. Once in the milk, the bac
teria multiplied rapidly, so that the milkman gave out cultures of

156

PLANTS WITHOUT CHLOROPHYLL

typhoid in his milk bottles. Proper safeguarding of our water and
milk supply is necessary if we are to keep typhoid away.

Blood Poisoning. The bacterium causing blood poisoning
is another toxin-forming germ. It lives in dust and dirt and is
often found on the skin. It enters the body through cuts or bruises.
It seems to thrive best in less oxygen than is found in the air. It
is therefore important not to close up with court-plaster wounds
which such germs may have entered. It, with typhoid, is respon
sible for four times as many deaths as bullets and shells in time
of battle. The wonderfully small death rate of the Japanese army
in their war with Russia was due to the fact that the Japanese
soldiers always boiled their drinking water before using it, and
their surgeons always dressed all wounds on the battlefield, using
powerful antiseptics in order to kill any bacteria that might have
lodged in the exposed wounds.

Other Diseases. Many other diseases have been traced to
bacteria. Diphtheria is one of the best known. As it is a throat

disease, it may easily

be conveyed from
one person to another
by kissing, putting
into the mouth ob
jects which have
come in contact with
the mouth of the
patient, or by food
into which the germs
have been carried.
Another disease
which probably
causes more misery
in the world than any

other germ disease is syphilis. Hundreds of thousands of new
born babies die annually or grow up handicapped by deformities
from this dread scourge. Syphilis and gonorrhea, both diseases
of the same sort and contracted in the same manner, hand down
to innocent wives and still more innocent children a heritage of

...-

? G

F ^

P o

P \

P ^

]

i %s,

4 /

Jv< /

\ ",

x '

V /

This figure shows how a milk route might be instru
mental in spreading diphtheria. X is a farm on
which a case of diphtheria occurred that was re
sponsible for all the cases along milk routes A and
F in Hyde Park, Dorchester, and Milton. How
would you explain this ?

PLANTS WITHOUT CHLOROPHYLL 157

disease " even unto the third and fourth generation." Grippe,
pneumonia, whooping cough, and colds are believed to be caused
by bacteria. Other diseases, as malaria, yellow fever, sleeping
sickness, and probably smallpox, scarlet fever, and measles, are
due to the attack of one-celled animal parasites. Of these we
shall learn later in Chapter XV.

Immunity. It has been found that after an attack of a germ
disease the body will not soon be again attacked by the same
disease. This immunity, of which we will learn more later, seems
to be due to a manufacture in the blood of substances which
fight the bacteria or their poisons. If a person keeps his body
in good physical condition and lives carefully, he will do much
toward acquiring this natural immunity.

Acquired Immunity. Modern medicine has discovered means
of protecting the body from some contagious diseases. Vaccina
tion as protection against smallpox, the use of antitoxins (of which
more later) against diphtheria, and inoculation against typhoid
are all ways in which we may be protected against diseases.

Methods of fighting Germ Diseases. As we have seen, dis
eases produced by bacteria may be caused by the bacteria being
directly transferred from one person to another, or the disease
may obtain a foothold in the body from food, water, or by taking
them into the blood through a cut or a wound or a body opening.

It is evident that as individuals we may each do something to
prevent the spread of germ diseases, especially in our homes. We
may keep our bodies, especially our hands and faces, clean. Sweep
ing and dusting may be done with damp cloths so as not to raise a
dust ; our milk and water, when from a suspicious supply, may be
sterilized or pasteurized. Wounds through which bacteria might
obtain foothold in the body should be washed with some antiseptic
such as carbolic acid (1 part to 25 water), which kills the germs.
In a later chapter we shall learn more of how we may cooperate
with the authorities to combat disease and make our city or town
a better place in which to live. 1

1 Teachers may take up parts or all of Chapter XXIV at this point. I have
found it advisable to repeat much of the work on bacteria afar the students have
taken up the study of the human organism.

158 PLANTS WITHOUT CHLOROPHYLL

REFERENCE BOOKS

ELEMENTARY

Hunter, Laboratory Problems in Civic Biology. American Book Company.

Bigelow, Introduction to Biology. The Macmillan Company.

Conn, Bacteria, Yeasts, and Molds in the Home. Ginn and Company.

Conn, Story of Germ Life. D. Appleton and Company.

Davison, The Human Body and Health. American Book Company.

Frankland, Bacteria in Daily Life. Longmans, Green, and Company.

Overton, General Hygiene. American Book Company.

Prudden, Dust and its Dangers. G. P. Putnam's Sons.

Prudden, The Story of the Bacteria. G. P. Putnam's Sons.

Ritchie, Primer of Sanitation. World Book Company.

Sharpe, Laboratory Manual in Biology, pages 123-132. American Book Company.

ADVANCED

Conn, Agricultural Bacteriology. P. Blakiston's Sons and Company.

Coulter, Barnes, and Cowles, A Textbook of Botany, Vol. I. American Book Com
pany

De Bary, Comparative Morphology and Biology of the Fungi, Mycetozoa, and Bacteria.
Clarendon Press.

Duggar, Fungous Diseases of Plants. Ginn and Company.

Hough and Sedgwick, The Human Mechanism. Ginn and Company.

Hutchinson, Preventable Diseases. Houghton, Mifflin and Company.

Lee, Scientific Features of Modern Medicine. Columbia University Press.

Muir and Ritchie, Manual of Bacteriology. The Macmillan Company.

Newman, The Bacteria. G. P. Putnam's Sons.

Sedgwick, Principles of Sanitary Science and Public Health. The Macmillan Com
pany.

XII. THE RELATIONS OF PLANTS TO ANIMALS

Problems. To determine the general biological relations ex
isting between plants and animals.
(a) As shown in a balanced aquarium.
(&) As shown in hay infusion.

SUGGESTIONS FOB LABORATORY WORK

Demonstration of life in a "balanced" and "unbalanced" aquarium.
Determination of factors causing balance.

Demonstration of hay infusion. Examination to show forms of animal
and plant life.

Tabular comparison between balanced aquarium and hay infusion.

Some Ways in which Plants affect Animals. We have been
studying the life of plants in order better to understand the life
of animals and men. We have seen first that green plants play
indirectly a tremendous part in man's welfare by supplying him
with food. We have found that the colorless plants directly
affected his welfare by causing disease, and by causing decay,
thus making usable the nitrogen locked up in dead bodies of plants
and animals, and by some even supplying nitrogen from the at
mosphere. The dependence of animals upon plants has been
shown and the interdependence of plants on animals has also been
seen in cross-pollination and in the supply of raw food materials
to plants by animals.

Study of a Balanced Aquarium. Perhaps the best way for us
to understand the interrelation between plants and animals is to
study an aquarium in which plants and animals live and in which
a balance has been established between the plant life on one side
and animal life on the other. Aquaria containing green pond
weeds, either floating or rooted, a few snails, some tiny animals
known as water fleas, and a fish or two will, if kept near a light
window, show this relation.

159

160 THE RELATIONS OF PLANTS TO ANIMALS

We have seen that green plants under favorable conditions of
sunlight, heat, moisture, and with a supply of raw food materials,
give off oxygen as a by-product while manufacturing food in their
green cells. We know the necessary raw materials for starch
manufacture are carbon dioxide and water, while nitrogenous
material is necessary for the making of proteins within the plant.

A balanced aquarium. Explain the term "balanced."

In previous experiments we have proved that carbon dioxide is
given off by any living thing when oxidation occurs in the body.
The crawling snails and the swimming fish give off carbon dioxide,
which is dissolved in the water ; the plants themselves, at all times,
oxidize food within their bodies, and so must pass off some car
bon dioxide. The green plants in the daytime use up the carbon
dioxide obtained from the various sources and, with the water

THE RELATIONS OF PLANTS TO ANIMALS 161

taken in, manufacture starch. While this process is going on, oxy

gen is given off to the water of the aquarium, and this free oxygen

is used by the animals there.

But the plants are continually growing larger. The snails and

fish, too, eat parts of the plants. Thus the plant life gives food

to the animals within the aquarium.

The animals give off certain ni

trogenous wastes of which we shall

learn more later. These materials,

with other nitrogenous matter from

the dead parts of the plants or

animals, form part of the raw

material used for protein manu

facture in the plant. This nitrog

enous matter is prepared for use

by several different kinds of bac- This diagram shows that plants and

teria which first break the dead

bodies down and then give it to

the plants in the form of soluble

nitrates. The green plants manu

facture food, the animals eat the plants and give off organic waste,

from which the plants in turn make their food and living matter.

The plants give off oxygen to the
animals, and the animals give car
bon dioxide to the plants. Thus a
balance exists between the plants
and animals in the aquarium. Make
a table to show this balance.

Relations between Green Plants

The carbon and oxygen cycle in the aild Animals. What goes on in

balanced aquarium. Trace by the aquarium is an example of the

relation existing between all green
plants and all animals. Every-

where ^ the WQM green plantg

are making food which becomes, sooner or later, the food of
animals. Man does not feed to a great extent upon leaves, but
he eats roots, stems, fruits, and seeds. When he does not feed

HUNTER, CIV. BI. 11

animals on the earth hold the
same relation to each other as
plants and animals in a balanced
aquarium. Explain the diagram
in your notebook.

as CO 2 until animals give it off.

Show what happens to the oxygen.

162 THE RELATIONS OF PLANTS TO ANIMALS

directly upon plants, he eats the flesh of plant eating animals,
which in turn feed directly upon plants. And so it is the world
over; the plants are the food makers and supply the animals.

Carbon dioxide
I (C0 2 )

Carbon dioxide
(C0 2 )

Water

Simple Salts

Water
X(H 2 0)

Ammonia]
(NH?

Plants

with chlorophyll

buildup complex

organic substances

They store up

energy from the sun

in the process

and

form

Animals
and plants without

chlorophyll

[which tear down complex 1 Ammonia
organic substances I (NH 3 )
and set free energy
in the process in
form of heat

I \

Energy from sun. Energy set free

as heat.
The relations between green plants and animals.

Green plants also give a very considerable amount of oxygen to
the atmosphere every day, which the animals may use.

The Nitrogen Cycle. The animals in their turn supply much
of the carbon dioxide that the plant uses in starch making. They

also supply some of the
nitrogenous matter used by
the plants, part being given
the plants from the dead
bodies of their own rela
tives and part being pre
pared from the nitrogen of

the air through the agency
^-so-

<%>m

Animal Life

soil)

Nitrites
'Nitric Bacteria

of bacteria, which live
upon the roots of certain
plants. These bacteria are
the only organisms that
can take nitrogen from
the air. Thus, in spite of all the nitrogen of the atmosphere,
plants and animals are limited in the amount available. And the

Th3 nitrogsn cycle. Trace the nitrogen from
its source in the air until it gets back again
into the air.

THE RELATIONS OF PLANTS TO ANIMALS 163

available supply is used over and over again, perhaps in nitrog
enous food by an animal, then it may be given off as organic
waste, get into the soil, and be taken up by a plant through the
roots. Eventually the nitrogen forms part of the food supply in
the body of the plant, and then may become part of its living
matter. When the plant dies, the nitrogen is returned to the soil.
Thus the usable nitrogen is kept in circulation. 1

Symbiosis. We have seen that in the balanced aquarium
the animals and plants, in a wide sense, form a sort of unconscious
partnership. This process of living together for mutual advantage
is called symbiosis. Some animals thus combine with plants;
for example, the tiny animal known as the hydra with certain of
the one-celled algae, and, if we accept the term in a wide sense, all
green plants and animals live in this relation of mutual give and
take. Animals also frequently live in this relation to each other,
as the crab, which lives within the shell of the oyster; the sea
anemones, which are carried around on the backs of some hermit
crabs, aiding the crab in protecting it from its enemies, and being
carried about by the crab to places where food is plentiful.

A Hay Infusion. Still another example of the close relation
between plants and animals may be seen in the study of a hay
infusion. If we place a wisp of hay or straw in a small glass jar
nearly full of water, and leave it for a few days in a warm room,
certain changes are seen to take place in the contents of the jar;
after a little while the water gets cloudy and darker in color, and a
scum appears on the surface. If some of this scum is examined
under the compound microscope, it will be found to consist almost
entirely of bacteria. These bacteria evidently aid in the decay
which (as the unpleasant odor from the jar testifies) is beginning
to take place. As we have learned, bacteria flourish wherever the
food supply is abundant. The water within the jar has come to
contain much of the food material which was once within the
leaves of the grass, organic nutrients, starch, sugar, and pro
teins, formed in the leaf by the action of the sun on the chlorophyll

1 A small amount of nitrogen gas is returned to the atmosphere by the action of
the decomposing bacteria on the ammonia compounds in the soil. (See figure of
nitrogen cycle.)

164 THE RELATIONS OF PLANTS TO ANIMALS

of the leaf, and now released into the water by the breaking down
of the walls of the cells of the leaves. The bacteria themselves
release this food from the hay by causing it to decay. After a
few days small one-celled animals appear; these multiply with
wonderful rapidity, so that in some cases the surface of the water
seems to be almost white with active one-celled forms of life. If
we ask ourselves where these animals come from, we are forced

Life in the late stage of a hay infusion. B, bacteria, swimming or forming masses
of food upon which th3 one-celled animals, the paramcecia, are feeding;
G, gullet; F.V., food vacuols; C.V., contractile vacuole; P, pleurococcus;
P.D., pleurococcus dividing. (Drawn from nature by J. W. Teitz.)

to the conclusion that they must have been in the water, in the
air, or on the hay. Hay is dried grass and may have been cut
in a field near a pool containing these creatures. When the
pool dried up, the wind may have scattered some of these little
organisms in the dried mud or dust. Some may have existed in
a dormant state on the hay and the water awakened them to active

THE RELATIONS OF PLANTS TO ANIMALS 165

life. In the water, too, there may have been some living cells,
plants and animals,

At first the multiplication of the tiny animals within the hay
infusion is extremely rapid ; there is food in abundance and near
at hand. After a few days more, however, several kinds of one-
celled animals may appear, some of which prey upon others. Con
sequently a struggle for life takes place, which becomes more and
more intense as the food from the hay is used up. Eventually
the end comes for all the animals unless some green plants obtain
a foothold within the jar. If such a thing happens, food will be
manufactured within their bodies, a new food supply arises for the
animals within the jar, and a balance of life may result.

REFERENCE BOOKS

ELEMENTARY

Hunter, Laboratory Problems in Civic Biology. American Book Company.
Sharpe, A Laboratory Manual for the Solution of Problems in Biology, pp. 133-138.
American Book Company.

ADVANCED

Eggerlin and Ehrenberg, The Fresh Water Aquarium and its Inhabitants. Henry

Holt and Company.

Furneaux, Life in Ponds and Streams. Longmans, Green, and Company.
Parker, Biology. The Macmillan Company.
Sedgwick and Wilson, Biology. Henry Holt and Company.

XIII. SINGLE-CELLED ANIMALS CONSIDERED AS

ORGANISMS

Problems. To determine :

(a) .How a one-celled animal is influenced by its environ
ment.

(&) How a single cell performs its functions.
(c} The structure of a single-celled animal,

LABORATORY SUGGESTIONS

Laboratory study. Study of paramoecium under compound microscope
in its relation to food, oxygen, etc. Determination of method of move
ment, turning, avoiding obstructions, sensitiveness to stimuli. Drawings
to illustrate above points.

Laboratory demonstration. Living paramrecium to show structure of
cell. Demonstration with carmine to show food vacuoles, and action of
cilia. Use of charts and stained specimens to show other points of cell
structure. Laboratory demonstration of fission.

The Simplest Plants. We have seen that perhaps the simplest
plant would be exemplified by one of the tiny bacteria we have
just read about. A typical one-celled plant, however, would
contain green coloring matter or chlorophyll, and would have the
power to manufacture its own food under conditions
giving it a moderate temperature, a supply of water,
oxygen, carbon dioxide, and sunlight. Such a
simple plant is the pleurococcus, the " green slime "
Pieurococcus. A seen on the shady sides of trees, stones, or city
plant eel 1 * * houses. This plant would meet one definition of a
cell, as it is a minute mass of protoplasm contain
ing a nucleus. It is surrounded by a wall of a woody material
formed by the activity of the living matter within the cell. It also
contains a little mass of protoplasm colored green. Of the work
of the chlorophyll in the manufacture of organic food we have

166

SINGLE-CELLED ANIMALS AS ORGANISMS 167

already learned. Such is a simple plant cell. Let us now
examine a simple animal cell in order to compare it with that
of a plant.

Where to find Paramoecium. If we examine very carefully
the surface of a hay infusion, we are likely to notice in addition to
the scum formed of bacteria, a mass of whitish tiny dots collected
along the edge of the jar close to the surface of the water. More
attentive observation shows us that these objects move, and that
they are never found far from the surface.

The Life Habits of Paramoecium. If we place on a slide a drop
of water containing some of these moving objects and examine
it under the compound microscope, we find each minute whitish
dot is a cell, elongated, oval, or elliptical in outline and somewhat
flattened. This is a one-celled animal known as the paramoecium
or the slipper animalcule (because of its shape) .

Seen under the low power of the microscope, it appears to be
extremely active, rushing about now rapidly, now more slowly,
but seemingly always taking a definite .course. The narrower end
of the body (the anterior) usually goes first. If it pushes its way
past any dense substance in the water, the cell body is seen to
change its shape temporarily as it squeezes through.

Response to Stimuli. Many of these little creatures may be
found collected around masses of food, showing that they are at
tracted by it. In another part of the slide we may find a number
of the paramcecia lying close to the edge of an air bubble with
the greatest possible amount of their surface exposed to its
surface. These animals are evidently taking in oxygen by
osmosis. They are breathing. A careful inspection of the jar
containing paramcecia shows thousands of tiny whitish bodies
collected near the surface of the jar. In the paramcecium, as
in the one-celled plants, the protoplasm composing the cell
responds to certain agencies acting upon it, coming from without ;
these agencies we call stimuli. Such stimuli may be light, differ
ences of temperature, presence of food, electricity, or other factors
of its surroundings. Plant and animal cells may react differently
to the same stimulus. In general, however, we know that proto
plasm is irritable to some of these factors. To severe stimuli,

168 SINGLE-CELLED ANIMALS AS ORGANISMS

protoplasm usually responds by contracting, another power which
it possesses. We know, too, that plant and animal cells take in
food and change the food to protoplasm, that is, that they assimi
late food ; and that they may waste away and repair themselves.
Finally, we know that new plant and animal cells are reproduced
from the original bit of protoplasm, a single cell.

The Structure of Paramoecium. The cell body is almost
transparent, and consists of semifluid protoplasm which has a

granular grayish appearance under the
microscope. This protoplasm appears to
be bounded by a very delicate membrane
through which project numerous delicate
threads of protoplasm called cilia. (These
are usually invisible under the micro
scope).

The locomotion of the paramoecium is
caused by the movement of these cilia,
which lash the water like a multitude of
tiny oars. The cilia also send particles
of food into a funnel-like opening, the
gullet, on one side of the cell. Once in-
A paramoecium. c.v.,contrac- side the cell body, the particles of food

tile vacuole; f.v., food , ,-, -, . , ,., ,, ,

vacuole; m, mouth; ma.n., materials are gathered into little balls
macronucleus; mi.n., mi- within the almost transparent proto-

cronucleus; w.v., water i mi r ,

vacuole. plasm. These masses of food seem to be

inclosed within a little area containing

fluid, called a vacuole. Other vacuoles appear to be clear ; these
are spaces in which food has been digested. One or two larger
vacuoles may be found; these are the contractile vacuoles; their
purpose seems to be to pass off waste material from the cell
body. This is done by pulsation of the vacuole, which ultimately
bursts, passing fluid waste to the outside. Solid wastes are passed
out of the cell in somewhat the same manner. No breathing
organs are seen, because osmosis of oxygen and carbon dioxide
may take place anywhere through the cell membrane. The
nucleus of the cell is not easily visible in living specimens.
In a cell that has been stained it has been found to be a double

SINGLE-CELLED ANIMALS AS ORGANISMS 169

MAC.
MIC

structure, consisting of one large and one
small portion, called, respectively, the ma-
cronucleus and the micronucleus.

Reproduction of Paramoecium. Some
times a paramcecium may be found in the
act of dividing by the process known as
fission, to form two new cells, each of which
contains half of the original cell. This is a
method of asexual reproduction. The origi
nal cell may thus form in succession many
hundreds of cells in every respect like the Paramoecium dividing by
original parent cell. *?? M > mo , uth ;

MAC., macronucleus ;

Amoeba. 1 -- In order to understand more MIC., micronucleus.

fully the life of a simple bit of protoplasm, ^^ n) Sedg1 ^ and

let us take up the study of the amceba, a

type of the simplest form of animal life. Unlike the plant and

animal cells we have examined, the amoeba has no fixed form.

Viewed under the compound micro
scope, it has the appearance of an
irregular mass of granular proto
plasm. Its form is constantly
changing as it moves about. This
is due to the pushing out of tiny
projections of the protoplasm of
the cell, called pseudopodia (false
feet). The locomotion is accom
plished by a streaming or flowing
of the semifluid protoplasm. The
pseudopodia are pushed forward in
the direction which the animal is

Amoeba, with pseudopodia (P.) ex

tended ; EC, ectoplasm ; END, en- to go, the rest oi the body lollow-

doplasm; the dark area (AT.) is j ng j n the centra l part of the

the nucleus, (r rom a photograph

loaned by Prof essorG.N. Calkins.) Cell IS

the nucleus. This im-

1 Amoebae may be obtained from the hay infusion, from the dead leaves in the bot
tom of small pools, from the same source in fresh-water aquaria, from the roots of
duckweed or other small water plants, or from green algae growing in quiet localities.
No sure method of obtaining them can be given.

170 SINGLE-CELLED ANIMALS AS ORGANISMS

portant organ is difficult -to see, except in cells that have been
stained.

Although but a single cell, still the amceba appears to be aware
of the existence of food when it is near at hand. Food may be
taken into the body at any point, the semifluid protoplasm simply
rolling over and engulfing the food material. Within the body,
as in the paramoecium, the food becomes inclosed within a fluid
space or vacuole. The protoplasm has the power to take out such
material as it can use to form new protoplasm or give energy.

Circulation of food material is
accomplished by the constant
streaming of the protoplasm
within the cell.

The cell absorbs oxygen
from the water by osmosis
through its delicate mem
brane, giving up carbon dioxide
in return. Thus the cell
" breathes " through any part
of its body covering.

Waste nitrogenous products
formed within the cell when
work is done are passed out
by means of the contractile
vacuole.

The amceba, like other one-
celled organisms, reproduces

Amoeba, showing the changes which take
place during division of the cell. The
dark body in each figure is the nu
cleus ; the transparent circle, the con
tractile vacuole ; the large granular
masses, the food vacuoles. Much
magnified.

by the process of fission. A
single cell divides by splitting
into two others, each of which

resembles the parent cell, except that they are of less bulk.
When these become the size of the parent amceba, they each in
turn divide. This is a kind of asexual reproduction.

When conditions unfavorable for life come, the amceba, like
some one-celled plants, encysts itself within a membranous
wall. In this condition it may become dried and be blown
through the air. Upon return to a favorable environment, it

SINGLE-CELLED ANIMALS AS ORGANISMS 171

begins life again, as before. In this respect it resembles the
spore of a plant.

The Cell as a Unit. In the daily life of a one-celled animal we
find the single cell performing all the general activities which we
shall later find the many-celled animal is able to perform. In the
amoeba no definite parts of the
cell appear to be set off to per
form certain functions ; but
any part of the cell can take in
food, can absorb oxygen, can
change the food into proto
plasm, and excrete the waste
material. The single cell is, in
fact, an organism able to carry
on the business of living almost
as effectually as a very com
plex animal.

Complex One-celled Ani
mals. In the paramcecium
we find a single cell, but we
find certain parts of the cell
having certain definite func
tions : the cilia are used for
locomotion ; a definite part of
the cell takes in food, while the
waste passes out at another
definite spot. In another one-
celled animal called vorticella,

Vorticella. e, gullet ; n, nucleus ; cv, con-
part of the Cell has become tractile vacuole ; a, axis ; s, sheath ; fv,
elongated and is Contractile. food vacuole. (From Herrick's General

Zoology.)

By this stalk the little animal

is fastened to a water plant or other object. The stalk may be said
to act like a muscle fiber, as its sole function seems to be move
ment ; the cilia are located at one end of the cell and serve to
create a current of water which will bring food particles to the
mouth. Here we have several parts of the cell, each doing a dif
ferent kind of work. This is known as physiological division of labor.

172 SINGLE-CELLED ANIMALS AS ORGANISMS

Habitat of Protozoa. Protozoa are found almost everywhere
in shallow water, especially close to the surface. They appear
to be attracted near to the surface by the supply of oxygen.
Every fresh-water lake swarms with them; the ocean contains
countless myriads of many different forms.

Use as Food. They are so numerous in lakes, rivers, and the
ocean as to form the food for many animals higher in the scale of
life. Almost all fish that do not take the hook and that travel
in schools, or companies, migrating from one place to another,
live partly on such food. Many feed on slightly larger animals,
which in turn eat the Protozoa. Such fish have on each side of the
mouth attached to the gills a series of small structures looking like
tiny rakes. These are called the gill rakers, and aid in collecting
tiny organisms from the water as it passes over the gills. The
whale, the largest of all mammals, strains protozoans and other
small animals and plants out of the water by means of hanging
plates of whalebone or baleen, the slender filaments of which form
a sieve from the top to the bottom of the mouth.

Protozoa cause Disease. Protozoa of certain kinds play an
important part in causing malaria, yellow fever, and other diseases,
as we shall see later. 1 (See page 217.)

REFERENCE BOOKS

ELEMENTARY

Hunter, Laboratory Problems in Civic Biology. American Book Company.
Davison, Human Body and Health. American Book Company.
Jordan, Kellogg and Heath, Animal Studies. D. Appleton and Company.
Sharpe, Laboratory Manual, pp. 140-143. American Book Company.

ADVANCED

Calkins, The Protozoa. Macmillan Company.

Jennings, Study of the Lower Organisms. Carnegie Institution Report.

Parker, Lessons in Elementary Biology. The Macmillan Company.

Wilson, The Cell in Development and Inheritance. The Macmillan Company.

1 Teachers may find it expedient to take up the study of protozoan diseases at
this point.

XIV. DIVISION OF LABOR. THE VARIOUS FORMS OF
PLANTS AND ANIMALS

Problems. The development and forms of plants.
The development of a simple animal.
What is division of labor ? In what does it result ?
How to know the ehief characters of some great animal
groups.

LABORATORY SUGGESTIONS

A visit to a botanical garden or laboratory demonstration. Some of the
forms of plant life. Review of essential facts in development of bean
or corn embryo.

Demonstration. Charts or models showing the development of a many-
celled animal from egg through gastrula stage.

Demonstration. Types which illustrate increasing complexity of body
form and division of labor.

Museum trip. To afford pupil a means of identification of examples
of principal phyla. This should be preceded by objective demonstration
work in school laboratory.

Reproduction in Plants. Although there are very many
plants and animals so small and so simple as to be composed of
but a single cell, by far the greater part of the animal and plant
world is made up of individuals which __________________________

are collections of cells living together.

T 1 1 J. 1*1 J.1_ 1

In a simple plant like the pond scum,

a string or filament of cells is formed f t ^L toTo .

by a single cell dividing crosswise, the thread made up of cells ?
two cells formed each dividing into two

more. Eventually a long thread of cells is thus formed. At times,
however, a cell is formed by the union of two cells, one from each
of two adjoining filaments of the plant. At length a hard coat
forms around this cell, which has now become a spore. The
tough covering protects it from unfavorable changes in the sur-

173

174

DIVISION OF LABOR

roundings. Later, when (conditions become favorable for its

germination, the spore may form a new filament of pond scum.
In molds, in yeasts, and in the bacteria we also
found spores could be formed by the protoplasm
of the plant cutting up into a number of tiny
spores. These spores are called asexual (without
sex) because they are not formed by the union
of two cells, and may give rise to other tiny
plants like themselves. Still other plants, mosses
and ferns, give rise to two kinds of spores, sexual
and asexual. All of these collectively are called
spore plants.

Reproduction in Seed Plants. Another great
group of plants we have studied, plants of varied
shapes and sizes, produce
seeds. They bear flowers
and fruits.

The embryo develops
from a single fertilized
" egg," growing by cell
division into two, four,

eight, and a constantly increasing number

of cells until after a time a baby plant is

formed, which as in the bean, either con
tains some stored food to give it a start

in life, or, as in the corn, is surrounded

with food which it can digest and absorb

into its own tiny body. We have seen

that these young plants in the seed are

able to develop when conditions are favor
able. Furthermore, the young of each

kind of plant will eventually develop into

the kind of plant its parent was and into

no other kind. Thus the plant world is

divided into many tribes or groups.

Plants are placed in Groups. If we plant a number of peas so

that they will all germinate under the same conditions of soil, tem-

The formation of
spores in pond
scum, zs, zygo-
spore; /, fusion
in progress.

The formation and growth of
a plant embryo. 1, the
?perm and egg cell uniting;
2, a fertilizad egg; 3, two
cells formed by division;
4, four cells formed from
two ; 5, a many-celled
embryo; 6, young plant;
H, hypocotyl; P, plumule;
C, cotyledons.

DIVISION OF LABOR

175

A colony of trilliums, a flowering plant.
(Photograph by W. C. Barbour.)

perature, and sunlight, the
seedlings that develop will
each differ one from an
other in a slight degree. 1
But in a general way they
will have many characters
in common, as the shape
of the leaves, the posses
sion of tendrils, form of
the flower and fruit. A
species of plants or animals
is a group of individuals so
much alike in their char
acters that they might have had the same parents. Individuals of
such species differ slightly ; for no two individuals are exactly alike.

Species are grouped to
gether in a larger group
called a genus. For ex
ample, many kinds of peas
the wild beach peas, the
sweet peas, and many
others are all grouped in
one genus (called Lathyrus,
or vetchling) because they
have certain structural
characteristics in common.
Plant and animal genera
are brought together in still
larger groups, the classifica
tion based on general like
nesses in structure. Such
groups are called, as they
become successively larger,

Rock fern, polypody. Notice the underground
stem giving off roots from its lower surface,
and leaves (C), (>S), from its upper surface.

Family, Order, and Class. Thus both the plant and animal king
doms are grouped into divisions, the smallest of which contains

1 NOTE TO TEACHERS. A trip to the Botanical Garden or to a Museum should
be taken at this time.

176

PLANTS CLASSIFIED

individuals very much alike ; and the largest of which contains
very many groups of individuals, the groups having some char
acters in common. This is called a system of classification.

Classification of the Plant Kingdom. The entire plant king
dom has been divided into four sub-kingdoms by botanists :

f Angiosperms, true flowering plants.
1. SpermatophytesA . V , . .

I (Jymnosperms, the pines and their allies.

2. Pteridophytes.

3. Bryophytes.

The fern plants and their allies.
The moss plants and their allies.

Rockweed, a brown algae, showing its distribution oa rocks below highwator mark.

4. Thallophytes. The Thallophytes form two groups : the
Alga3 and the Fungi ; the algae being green, while the fungi have
no chlorophyll.

The extent of the plant kingdom can only be hinted at ; each
year new species are added to the lists. There are about 110,000
species of flowering plants and nearly as many flowerless plants.
The latter consist of over 3500 species of fernlike plants, some
16,500 species of mosses, over 5600 lichens (plants consisting of a

DIVISION OF LABOR

177

partnership between algae and fungi), approximately 55,000 species
of fungi, and about 16,000 species of algse.

Development of a Simple Animal. Many-celled animals are
formed in much the same way as are many-celled seed plants. A
common bath sponge, an earthworm, a fish, or a dog, each and
all of them begin life in the same
manner. In a many-celled animal the
life history begins with a single cell,
the fertilized egg. As in the flowering
plant, this cell has been formed by
the union of two other cells, a tiny
(usually motile) cell; the sperm, and a
large cell, the egg. After the egg is
fertilized by a sperm cell, it splits into
two, four, eight, and sixteen cells;
as the number of cells increases, a
hollow ball of cells called the blastula
is formed ; later this ball sinks in on
one side, and a double-walled cup of
cells, now called a gastrula, results.
Practically all animals pass through
the above stages in their development
from the egg, although these stages
are often not plain to see because of
the presence of food material (yolk)
in the egg.

In animals the body consists of
three layers of cells : those of the
outside, developed from the outer
layer of the gastrula, are called ecto
derm, which later gives rise to the skin, nervous system, etc. ; an
inner layer, developed from the inner layer of the gastrula, the
endoderm, which forms the lining of the digestive organs, etc. ; a
middle layer, called the mesoderm, lying between the ectoderm
and the endoderm, is also found. In higher animals this layer
gives rise to muscles, the skeleton, and parts of other internal
structures.

HUNTER, CIV. BI. 12

A moss plant. G, the moss body;
S, the spore-bearing stalk
(fruiting body).

178

DIVISION OF LABOR

Physiological Division of Labor. If we compare the amoeba
and the paramcecium, we find the latter a more complex organism

Stages in the development of a fertilized egg into the gastrula stage. Read your
text, then draw these stages and name each stage.

than the former. An amoeba may take in food through any part
of the body ; the paramcecium has a definite gullet ; the amoeba

may use any part of the
body for locomotion; the
paramcecium has definite
parts of the cell, the cilia,
fitted for this work. Since
the structure of the para
mcecium is more complex,
we say that it is a " higher "
animal. In the vorticella, a
still more complex cell, part
of the cell, has grown out
like a stalk, has become
contractile, and acts like
muscle.

As we look higher in the
scale of life, we inva-

Photogrnph of a living vorticella, showing the , i r> j 41 .

contractile stalk and the cilia around the ^lably find that Certain
mouth. Compare this figure with that of the parts of a plant or animal
paramoecium. Which cell shows greater , _ , , ,

division of labor?

tain work, and only that

work. Just as in a community of people, there are some
men who do rough manual work, others who are skilled work
men, some who are shopkeepers, and still others who are profes-

DIVISION OF LABOR

179

sional men, so among plants
and animals, wherever col
lections of cells live together
to form an organism, there
is division of labor, some
cells being fitted to do
one kind of work, while
others are fitted to do work
of another sort. This

Different forms of tissue cells.
C, bone making cells ; E, epi
thelial cells; F, fat cells; L, liver
cells ; M , muscle cell ; i, invol
untary; v, voluntary; N, nerve
cell; C B, cell body; N.F., nerve
fiber ; T.B., nerve endings ;
W, colorless blood cells.

Enlarged lengthwise section of the hydra, a
very simple animal which shows slight
division of labor. ba, base ; b, bud ;
m, mouth; ov, ovary; sp, spermary.

is called physiological division of
labor.

As we have seen, the higher' plants
are made up of a vast number of cells
of many kinds. Collections of cells
alike in structure and performing the
same function we have called a tissue.
Examples of animal tissues are the
highly contractile cells set apart for
movement, muscles; those which
cover the body or line the inner parts
of organs, the skin, or epithelium; the
cells which form secretions or glands
and the sensitive cells forming the
nervous tissues.

Frequently several tissues have cer-

180

DIVISION OF LABOR

Flo.

tain functions to perform in conjunction with one another. The
arm of the human body performs movement. To do this, several
tissues, as muscles, nerves, and bones, must act together. A col
lection of tissues performing certain work we call an organ.

In a simple animal like a sponge, division of labor occurs be
tween the cells ; some cells which line the pores leading inward
create a current of water, and feed upon the minute organisms
which come within reach, other cells build the skeleton of the
sponge, and still others become eggs or sperms. In higher animals

more complicated in struc
ture and in which the
tissues are found working
together to form organs,
division of labor is much
more highly specialized.
In the human arm, an
organ fitted for certain
movements, think of the
number of tissues and the
complicated actions which
are possible. The most
extreme division of labor
is seen in the organism
which has the most com
plex actions to perform
and whose organs are fitted for such work, for there the cells or
tissues which do the particular work do it quickly and very well.

In our daily life in a town or city we see division of labor between
individuals. Such division of labor may occur among other ani
mals, as, for example, bees or ants. But it is seen at its highest
in a great city or in a large business or industry. In the stockyards
of Chicago, division of labor has resulted in certain men performing
but a single movement during their entire day's work, but this
movement repeated so many times in a day has resulted in wonder
ful accuracy and speed. Thus division of labor obtains its end.

Organs and Functions Common to All Animals. The same
general functions performed by a single cell are performed by a

ec6

Part of a sponge, showing how cells perform
division of labor, ect, ectoderm; mcs, meso-
derm ; end, endoderm ; c.c., ciliated cells,
which take in food by means of their fla-
gellse or large cilia (fla).

DIVISION OF LABOR 181

many-celled animal. But in the many-celled animals the various
functions of the single cell are taken up by the organs. In a com
plex organism, like man, the organs and the functions they per
form may be briefly given as follows :

(1) The organs of food taking : food may be taken in by indi
vidual cells, as those lining the pores of the sponge, or definite
parts of a food tube may be set apart for this purpose, as the mouth
and parts which place food in the mouth.

(2) The organs of digestion : the food tube and collections of
cells which form the glands connected with it. The enzymes in
the fluids secreted by the latter change the foods from a solid form
(usually insoluble) to that of a fluid. Such fluid may then pass by
osmosis, through the walls of the food tube into the blood.

(3) The organs of circulation : the tubes through which the blood,
bearing its organic foods and oxygen, reaches the tissues of the
body. In simple animals, as the sponge and hydra, no such organs
are needed, the fluid food passing from cell to cell by osmosis.

(4) The organs of respiration : the organs in which the blood
receives oxygen and gives up carbon dioxide. The outer layer of
the body serves this purpose in very simple animals ; gills or lungs
are developed in more complex animals.

(5) The organs of excretion : such as the kidneys and skin, which
pass off nitrogenous and other waste matters from the body.

(6) The organs of locomotion: muscles and their attachments
and connectives ; namely, tendons, ligaments, and bones.

(7) The organs of nervous control: the central nervous system,
which has control of coordinated movement. This consists of
scattered cells in low forms of life; such cells are collected into
groups and connected with each other in higher animals.

(8) The organs of sense: collections of cells having to do with
the reception and transmission of sight, hearing, smell, taste, touch,
pressure, and temperature sensations.

(9) The organs of reproduction : the sperm and egg-forming
organs.

Almost all animals have the functions mentioned above. In
most, the various organs mentioned are more or less developed,
although in the simpler forms of animal life some of the organs

182

ANIMALS CLASSIFIED

mentioned above are either very poorly developed or entirely
lacking. But in the so-called " higher " animals each of the
above-named functions is assigned to a certain organ or group of
organs. The work is done better and more quickly than in the
" lower " animals. Division of labor is thus a guide in helping
us to determine the place of animals in the groups that exist on the
earth.

The Animal Series. We have found that a one-celled animal
can perform certain functions in a rather crude manner. Man

can perform these same functions
in an extremely efficient manner.
Division of labor is well worked
out, extreme complexity of struc
ture is seen. Between these two
extremes are a great many groups
of animals which can be arranged
more or less as a series, showing
the gradual evolution or develop
ment of life on the earth. It
will be the purpose of the follow
ing pages to show the chief char
acteristics of the great groups of
the animal kingdom.

I. Protozoa. Animals composed of a single cell, reproducing
by cell division.

The following are the principal classes of Protozoa, examples of which we may

have seen or read about :

CLASS I. Rhizopoda (Greek for root-footed). Having no fixed form, with pseudo-
podia. Either naked as Amoeba or building limy (Foraminifera) or glasslike
skeletons (Radiolaria) .

CLASS II. Infusoria (in infusions') . Usually active ciliated Protozoa. Examples,
Paramcecium, Vorticella.

CLASS III. Sporozoa (spore animals). Parasitic and usually nonactive. Exam
ple, Plasmodium malarioe.

II. Sponges. Because the body contains many pores through
which water bearing food particles enters, these animals are called
Porifera. They are classed according to the skeleton they possess
into limy, glasslike, and horny fiber sponges. The latter are

The glasslike skeleton of a radiolarian,
a protozoan. (From model at Ameri
can Museum of Natural History.)

ANIMALS CLASSIFIED

183

A horny fiber sponge. Notice that it is a
colony. One fourth natural size.

the sponges of commerce.
With but few exceptions
sponges live in salt water
and are never free swim
ming.

III. Coelenterates. -
The hydra and its salt
water allies, the jellyfish,
hydroids, and corals, be
long to a group of animals
known as the Coelenterata.
The word " coslenterate "
(ccelom = body cavity, en-
teron = food tube) explains

the structure of the group. They are animals in which the real
body cavity is lacking, the animal in its simplest form being little
more than a bag. Some examples are the hydra, shown on page
179, salt-water forms known as hydroids, colonial forms which have

part of their life free swim
ming as jellyfish ; sea anemones
and coral polyps, tiny colonial
hydra like forms which build
a living or secreted covering.

IV. Worms. The worm-
like animals are grouped into
flatworms, roundworms, and
segmented or jointed worms.

(a) Flatworms are sometimes
parasitic, examples being the
tapeworm and liver fluke.

Sea anemones. One half natural size. The
right hand specimen is expanded and
shows the mouth surrounded by the

tentacles. The left hand specimen is Th usually small, ribbon-

contracted. (From model at the Ameri- J

can Museum of Natural History.) or leaf -like and flat and live in

water.

(6) Roundworms, minute threadlike creatures, are not often
seen by the city girl or boy. Vinegar eels, the horsehair worm,
the pork worm or trichina and the dread hookworm are examples.

184

ANIMALS CLASSIFIED

body rings or segments. Examples are the earth
worm, the sandworm (known to New York boys
as the fish worm), and the leeches or bloodsuckers.

A jointed worm.
The sandworm.
Slightly reduced.

The common starfish seen from below to show
the tube feet. About one half natural size.

V. Echinoderms. These are spiny-skinned animals, which
live in salt water. They are still more complicated in structure

Ab.

The crayfish, a crustacean. A, antenna; M, mouth; E, compound stalked eye;
Ch, pincher claw ; C.P., cephalothorax ; Ab, abdomen ; C.F., caudal fin, A
little reduced,

ANIMALS CLASSIFIED

185

A common snail, a
mollusk. (From a
photograph by
Davison.)

than the worms and may be known by the spines in their skin.
They show radial symmetry. Starfish or sea urchins are examples.

VI. Arthropods. These animals are distinguished by having
jointed body and legs. They form two great groups. The higher
forms of the Crustacea have only two regions in the body, a fused
head and thorax, called the cephalothorax, and an abdominal
region. A second group is the Insecta, of which we know some
thing already. Crustacea breathe by means

of gills, which are structures for taking oxygen
out of the water, while adult insects breathe
through air tubes called trachea.

Two smaller groups of arthropods also exist,
the Arachnida, consisting of spiders, scorpions,
ticks, and mites, and the Myriapoda, examples
being the " thousand leggers" found in some
city houses.

VII. Mollusca. Another large group is the
Mollusca. This phylum gets its name from
the soft, unsegmented body (mollis = soft).

Mollusks usually have a shell, which may be of one piece, as a
snail, or two pieces or valves, as the clam or oyster.

VIII. The Vertebrates. All of the animals we have studied
thus far agree in having whatever skeleton or hard parts they
possess on the outside of the body. Collectively, they are called
Invertebrates. This exoskeleton differs from the main or axial

skeleton of the higher
animals, the latter be
ing inside of the body.
The exoskeleton is
dead, being secreted
by the cells lining the
body, while the endo-
skeleton is, in part at
least, alive and is
capable of growth, e.g.
a broken arm or leg

The skeleton of a aog ; a typical vertebrate. bone Will grow to-

186

ANIMALS CLASSIFIED

gether. But a man has certain parts of the skeleton, as nails or
hair, formed by the skin and in addition possesses inside bones to
which the muscles are attached. Some of the bones are arranged
in a flexible column in the dorsal (the back) side of the body.
This vertebral column, as it is called, is distinctive of all vertebrates.
Within its bony protection lies the delicate central nervous system,
and to this column are attached the big bones of the legs and
arms. The vertebrate animals deserve more of our attention than
.other forms of life because man himself is a vertebrate.

The sand shark, an elasmobranch. Note the slits leading from the gills. (From
a photograph loaned by the American Museum of Natural History.)

Five groups or classes of vertebrates exist. Fishes, Amphibians,
Reptiles, Birds, and Mammals. Let us see how to distinguish one
class from another.

Fishes. Fishes are familiar animals to most of us. We know
that they live in the water, have a backbone, and that they have
fins. They breathe by means of gills, delicate organs fitted for
taking oxygen out of the water. The heart has two chambers, an
auricle and a ventricle. They have a skin in which are glands

The sturgeon, a ganoid fish.

ANIMALS CLASSIFIED

187

secreting mucus, a slimy substance which helps them go through
the water easily. They usually lay very many eggs.

CLASSIFICATION OF FISHES

ORDER I. The Elasmobranchs. Fishes which have a soft skeleton made of cartilage

and exposed gill slits. Examples : sharks, skates, and rays.
ORDER II. The Ganoids. Fishes which once were very numerous on the earth, but

which are now almost extinct. They are protected by platelike scales. Ex
amples : gars, sturgeon, and bowfin.
ORDER III. The Teleosts, or Bony Fishes.

They compose 95 per cent of all living

fishes. In this group the skeleton is

bony, the gills are protected by an

operculum, and the eggs are numerous.

Most of our common food fishes belong

to this class.
ORDER IV. The Dipnoi, or Lung Fishes.

This is a very small group. In many A bony fish.

respects they are more like amphibians

than fishes, the swim bladder being used as a lung. They live in tropical

Africa, South America, and Australia, inhabiting the rivers and lakes there.

Characteristics of Amphibia. The frog belongs to the class of
vertebrates known as Amphibia. As the name indicates (amphi,
both, and bia, life), members of this group live both in water and
on land. In the earlier stages of their development they take
oxygen into the blood by means of gills. When adult, however,
they breathe by means of lungs. At all times, but especially
during the winter, the skin serves as a breathing organ. The

Newt.

(From a photograph loaned by the American Museum of Natural
History.) About natural size.

skin is soft and unprotected by bony plates or scales. The heart
has three chambers, two auricles and one ventricle. Most am
phibians undergo a complete metamorphosis, or change of form,
the young being unlike the adults.

188

ANIMALS CLASSIFIED

CLASSIFICATION OF AMPHIBIA

ORDER I. Urodela. Amphibia having usually poorly developed appendages.
Tail persistent through life. Examples : mud puppy, newt, salamander.

ORDER II. Anura. Tailless Amphibia, which undergo a metamorphosis, breath
ing by gills in larval state, by lungs in adult state. Examples : toad and frog.

Characteristics of Reptilia.

- These animals are char
acterized by having scales
developed from the skin. In
the turtle they have become
bony and are connected with
the internal skeleton. Rep
tiles always breathe by means
of lungs, differing in this
respect from the amphibians.
They show their distant re
lationship to birds in that
their large eggs are incased
in a leathery, limy shell.

The leopard frog, an amphibian.

CLASSIFICATION OF REPTILES

ORDER I. Chelonia (turtles and tortoises). Flattened reptiles with body inclosed

in bony case. No teeth or sternum (breastbone). Examples: snapping

turtle, box tortoise.
ORDER II. Lacertilia (lizards). Body

covered with scales, usually having

two-paired appendages. Breathe

by lungs. Examples : fence lizard,

horned toad.

Box tortoise, a land reptile. (From
photograph loaned by the Ameri
can Museum of Natural History.)
About one fourth natural size.

The gila monster, a
poisonous lizard.
About one twelfth
natural size.

ANIMALS CLASSIFIED

189

ORDER III. Ophidia (snakes). Body
elongated, covered with scales. No
limbs present. Examples : garter
snake, rattlesnake.

ORDER IV. Crocodilia. Fresh-water
reptiles with elongated body and
bony scales on skin. Two-paired
limbs. Examples : alligator, crocodile.

The common garter snake. Reduced
to about one tenth natural size.

Birds. Birds among all other
animals are known by their cov
ering of feathers and the presence of wings. The feathers are de
veloped from the skin. These aid in flight, and protect the body
from the cold.

Adaptations in the bills of birds. Could we tell anything about the food of a bird
from its bill ? Do these birds all get their food in the same manner ? Do
they all eat the same kind of food ?

The form of the bill in particular shows adaptation to a wonder
ful degree. A duck has a flat bill for pushing through the mud and
straining out the food ; a bird of prey has a curved or hooked beak
for tearing ; the woodpecker has a sharp, straight bill for piercing
the bark of trees in search of the insect larva? which are hidden
underneath. Birds do not have teeth.

190

ANIMALS CLASSIFIED

The rate of respiration, of heartbeat, and the body temperature
are all higher in the bird than in man. Man breathes from twelve
to fourteen times per minute. Birds breathe from twenty to sixty
times a minute. Because of the increased activity of a bird,
there comes a necessity for a greater and more rapid supply of
oxygen, an increased blood supply to carry the material to be
used up in the release of energy, and a means of rapid excretion
of the wastes resulting from the process of oxidation. Birds are

Common tern and young, showing nesting and feeding habits. (From group
at American Museum of Natural History.)

large eaters, and the digestive tract is fitted to digest the food
quickly, by having a large crop in which food may be stored in a
much softened condition. As soon as the food is part of the blood,
it may be sent rapidly to the places where it is needed, by means
of the large four-chambered heart and large blood vessels.

The high temperature of the bird is a direct result of this rapid
oxidation; furthermore, the feathers and the oily skin form an
insulation which does not readily permit of the escape of heat.
This insulating cover is of much use to the bird in its flights at

ANIMALS CLASSIFIED 191

high altitudes, where the temperature is often very low. Birds
lay eggs and usually care for their young.

CLASSIFICATION OF BIRDS
ORDER I. Cursores. Running birds with no keeled breastbone. Examples :

ostrich, cassowary.
ORDER II. Passeres. Perching birds ;

three toes in front, one behind.

Over one half of all species of

birds are included in this order.

Examples : sparrow, thrush,

swallow. H

ORDER III. Gallince. Strong legs ;

feet adapted to scratching. Beak

stout. Examples : jungle fowl,

grouse, quail, domestic fowl.
ORDER IV. Raptores. Birds of prey.

Hooked beak. Strong claws.

Examples : eagle, hawk, owl.
ORDER V. Grallatores. Waders.

Long neck, beak, and legs. Ex
amples : snipe, crane, heron.
ORDER VI. Natatores. Divers and

swimmers. Legs short, toes -..,. >

webbed. Examples : gull, duck,

albatross.
ORDER VII. Columbince. Like Gal-

linse, but with weaker legs. Ex
amples : dove, pigeon.
ORDER VIII. Pici. Woodpeckers.

Two toes point forward, two African ostrich, one of the largest

backward, and adaptation for living birds.

climbing. Long, strong bill.

ORDER IX. Psittaci. Parrots, hooked beak and fleshy tongue.
ORDER X. Coccyges. Climbing birds, with powerful beak. Examples : king
fisher, toucan, and cuckoo.
ORDER XI. Macrochires. Birds having long-pointed wings, without scales on

metatarsus. Examples : swift, humming bird, and goatsucker.

Mammals. Dogs and cats, sheep and pigs, horses and cows,
all of our domestic animals (and man himself) have characters of
structure which cause them to be classed as mammals. They, like
some other vertebrates, have lungs and warm blood. They also
have a hairy covering and bear young developed to a form similar to
their own, 1 and nurse them with milk secreted by glands known
as the mammary glands ; hence the term " mammal."

1 With the exception of the monotremes.

192

EVOLUTION

The bison, an almost extinct mammal.

Adaptations in Mammalia. Of the thirty-five hundred species,
most inhabit continents; a few species are found on different islands,
and some, as the whale, inhabit the ocean. They vary in size from
the whale and the elephant to tiny shrew mice and moles. Adapta
tions to different habitat
and methods of life abound ;
the seal and whale have
the limbs modified into
flippers, the sloth and
squirrel have limbs pecul
iarly adapted to climbing,
while the bats have the
fore limbs modeled for
flight.

Lowest Mammals. The
lowest are the monotremes,
animals which lay eggs like
the birds, although they arc

provided with hairy covering like other mammals. Such are the Aus
tralian spiny anteater and the duck mole.

All other mammals bring forth their young developed to a form simi
lar to their own. The kangaroo and opossum, however, are provided
with a pouch on the under side of the body in which the very immature,
blind, and helpless young are nourished until they are able to care for
themselves. These pouched animals are called marsupials.
The other mammals may be briefly classified as follows :

CLASSIFICATION OF HIGHER MAMMALS

ORDER I. Edentata. Toothless or with very simple teeth. Examples: anteater,
sloth, armadillo.

ORDER II. Rodentia. Incisor teeth chisel-shaped, usually two above and two
below. Examples : beaver, rat, porcupine, rabbit, squirrel.

ORDER III. Cetacea. Adapted to marine life. Examples : whale, porpoise.

ORDER IV. Ungulata. Hoofs, teeth adapted for grinding. Examples : (a) odd-
toed, horse, rhinoceros, tapir ; (6) even-toed, ox, pig, sheep, deer.

ORDER V. Carnivora. Long canine teeth, sharp and long claws. Examples : dog,
cat, lion, bear, seal, and sea lion.

ORDER VI. Insectivora. Example : mole.

ORDER VII. Cheiroptera. Fore limbs adapted to flight, teeth pointed. Example: bat.

ORDER VIII. Primates. Erect or nearly so, fore appendage provided with hand.
Examples : monkey, ape, man.

EVOLUTION

193

Increasing Complexity of Structure and of Habits in Plants and
Animals. In our study of biology so far we have attempted to
get some notion of the various factors which act upon living things.
We have seen how plants and animals interact upon each other.
We have learned something about the various physiological pro
cesses of plants and animals, and have found them to be in many
respects identical. We have found grades of complexity in plants
from the one-celled plant, bacterium or pleurococcus, to the com
plicated flowering plants of considerable size and with many

formations inWestern United States and Characteristic Type cf 'Horse in each

The geological history of the horse. (After Mathews, in the American Museum
of Natural History.) Ask your teacher to explain this diagram.

organs. So in animal life, from the Protozoa upward, there is
constant change, and the change is toward greater complexity of
structure and functions. An insect is a higher type of life than a
protozoan, because its structure is more complex and it can per
form its work with more ease and accuracy. A fish is a higher
type of animal than the insect for these same reasons, and also for
another. The fish has an internal skeleton which forms a pointed
column of bones on the dorsal side (the back) of the animal. It is
a vertebrate animal.

HUNTER, CIV. BI. 13

194

EVOLUTION

"Birds
13000

Reptiles
3500

Amphibians
/1400

Fishes
13OOO

The Doctrine of Evolution. We have now learned that animal
forms may be arranged so as to begin with very simple one-celled
forms and culminate with a group which contains man himself.
This arrangement is called the evolutionary series. Evolution means

change, and these groups
are believed by scientists
to represent stages in com
plexity of development of
life on the earth. Geology
teaches that millions of
years ago, life upon the
earth was very simple,
and that gradually more
and more complex forms
of life appeared, as the
rocks formed latest in time
show the most highly de
veloped forms of animal
life. The great English
scientist, Charles^ Darwin,
from this and other evi
dence, explained the theory
of evolution. This is the
belief that simple forms of life on the earth slowly and gradually
gave rise to those more complex and that thus ultimately the most
complex forms came into existence.

The Number of Animal Species. Over 500,000 species of
animals are known to exist to-day, as the following table shows.

16,000
16,000
61,000
13,000
1,400
3,500
13,000
3,500
518,900

Sponges

r ^25001

Coelenterates
4500

Protozoa 8000

The evolutionary tree. Modified from Gal
loway. Copy this diagram in your note
book. Explain it as well as you can.

Protozoa . .

. . 8,000

Arachnids . .

Sponges . .

. . 2,500

Crustaceans . . .

Coalenterates .

. . 4,500

Mollusks . . . .

Echinoderms .

. . 4,000

Fishes ......

Flatworms

. . 5,000

Amphibians . . -,

Roundworms .

. . 1,500

Reptiles . . . .

Annelids . .

. . 4,000

Birds . . .

Insects .

360 000

Mammals

Myriapods . .

. . 2,000

Total . .

EVOLUTION 195

Man's Place in Nature. Although we know that man is
separated mentally by a wide gap from all other animals, in our
study of physiology we must ask where we are to place man. If we
attempt to classify man, we see at once he must be placed with
the vertebrate animals because of his possession of a vertebral
column. Evidently, too, he is a mammal, because the young are
nourished by milk secreted by the mother and because his body
has at least a partial covering of hair. Anatomically we find that
we must place man with the apelike mammals, because of these
numerous points of structural likeness. The group of mammals
which includes the monkeys, apes, and man we call the primates.

Although anatomically there is a greater difference between
the lowest type of monkey and the highest type of ape than there
is between the highest type of ape and the lowest savage, yet there
is an immense mental gap between monkey and man.

Instincts. Mammals are considered the highest of vertebrate
animals, not only because of their complicated structure, but be
cause their instincts are so well developed. Monkeys certainly
seem to have many of the mental attributes of man.

Professor Thorndike of Columbia University sums up their habits
of learning as follows :

" In their method of learning, although monkeys do not reach the
human stage of a rich life of ideas, yet they carry the animal method of
learning, by the selection of impulses and association of them with differ
ent sense-impressions, to a point beyond that reached by any other of
the lower animals. In this, too, they resemble man ; for he differs from
the lower animals not only in the possession of a new sort of intelligence,
but also in the tremendous extension of that sort which he has in common
with them. A fish learns slowly a few simple habits. Man learns quickly
an infinitude of habits that may be highly complex. Dogs and cats learn
more than the fish, while monkeys learn more than they. In the number
of things he learns, the complex habits he can form, the variety of lines
along which he can learn them, and in their permanence when once formed,
the monkey justifies his inclusion with man in a separate mental genus."

Evolution of Man. Undoubtedly there once lived upon the
earth races of men who were much lower in their mental organiza
tion than the present inhabitants. If we follow the early history

196 EVOLUTION

of man upon the earth, we find that at first he must have been
little better than one of the lower animals. He was a nomad,
wandering from place to place, feeding upon whatever living things
he could kill with his hands. Gradually he must have learned to
use weapons, and thus kill his prey, first using rough stone im
plements for this purpose. As man became more civilized, im
plements of bronze and of iron were used. About this time the
subjugation and domestication of animals began to take place.
Man then began to cultivate the fields, and to have a fixed place
of abode other than a cave. The beginnings of civilization were
long ago, but even to-day the earth is not entirely civilized.

The Races of Man. At the present time there exist upon the
earth five races or varieties of man, each very different from the
other in instincts, social customs, and, to an extent, in structure.
These are the Ethiopian or negro type, originating in Africa ; the
Malay or brown race, from the islands of the Pacific ; the Amer
ican Indian ; the Mongolian or yellow race, including the natives
of China, Japan, and the Eskimos ; and finally, the highest type
of all, the Caucasians, represented by the civilized white in
habitants of Europe and America.

REFERENCE BOOKS

ELEMENTARY

Hunter, Laboratory Problems in Civic Biology, American Book Company.

Bulletin of U.S. Department of Agriculture, Division of Biological Survey, Nos. 1,

6, 13, 17.

Davison, Practical Zoology. American Book Company.

Ditmars, The Reptiles of New York. Guide Leaflet 20. Amer. Mus. of Nat. History.
S arpe, A Laboratory Manual in Biology, pp. 140-150, American Book Company.
Walker, Our Birds and Their Nestlings. American Book Company.
Walter, H. E. and H. A., Wild Birds in City Parks. Published by authors.

ADVANCED

Apgar, Birds of the United States. American Book Company.

Beebe, The Bird. Henry Holt and Company.

Ditmars, The Reptile Book. Doubleday, Page and Company.

Hegner, Zoology. The Macmillan Company.

Hornaday, American Natural History.

Jordan and Evermann, Food and Game Fishes. Doubleday, Page and Company.

Parker and Haswell, Textbook of Zoology. The Macmillan Company.

Riverside Natural History. Houghton, Mifflin and Company.

Weed and Dearborn, Relation of Birds to Man. Lippincott.

XV. THE ECONOMIC IMPORTANCE OF ANIMALS

Problems. I. To determine the uses of animals.
(a) Indirectly as food.
(6) Directly as food.

(d) For clothing.

(e) Other direct economic uses.

(/) Destruction of harmful plants and animals.

!! To determine the harm done by animals.

(a) Animals destructive to those used for food.

(&) Animals harmful to crops and gardens.

(d} Animals destructive to stored food or clothing.

(e) Animals indirectly or directly responsible for disease.

LABORATORY SUGGESTIONS

Inasmuch as this work is planned for the winter months the laboratory
side must be largely museum and reference work. It is to be expected
that the teacher will wish to refer to much of this work at the time work is
done on a given group. But it is pedagogically desirable that the work as
planned should be varied. Interest is thus held. Outlines prepared by
the teacher to be filled in by the student are desirable because they lead
the pupil to individual selection of what seems to him as important mate
rial. Opportunity should be given for laboratory exercises based on
original sources. The pupils should be made to use reports of the U. S.
Department of Agriculture, the Biological Survey, various States Reports,
and others.

Special home laboratory reports may be well made at this time, for
example : determination at a local fish market of the fish that are cheap
and fresh at a given time. Have the students give reasons for this.
Study conditions in the meat market in a similar manner. Other local
food conditions may also be studied first hand.

197

198 THE ECONOMIC IMPORTANCE OF ANIMALS

USES OF ANIMALS

Indirect Use as Food. Just as plants form the food of ani
mals, so some animals are food for others. Man may make use
of such food directly or indirectly. Many mollusks, as the bar
nacle and mussel, are eaten by fishes. Other fish live upon tiny

organisms, water fleas and other small
crustaceans. These in turn feed upon
still smaller animals, and we may go
back and back until finally we come
to the Protozoa and one-celled water
plants as an ultimate source of food.
Direct Use as Food. Lower Forms.
- The forms of life lower than the
Crustacea are of little use directly as
food, although the Chinese are very
fond of one of the Echinoderms, a
holothurian.

Crustacea as Food. Crustaceans,
however, are of considerable value for
food, the lobster fisheries in particular
being of importance. The lobster is
highly esteemed as food, and is rapidly
disappearing from our coasts as the
result of overfishing. Between twenty
and thirty million are yearly taken on
the North Atlantic coast. This means
a value at present prices of about
$15,000,000. Laws have been enacted in New York and other
states against overfishing. Egg-carrying lobsters must be returned
to the water ; all smaller than six to nine inches in length (the law
varies in different states) must be put back ; other restrictions are
placed upon the taking of the animals, in hope of saving the race
from extinction. Some states now hatch and care for the young
for a period of time ; the United States Bureau of Fisheries is also
doing much good work, in the hope of restocking to some extent
the now almost depleted waters.

North American lobster. This
specimen, preserved at the
U. S. Fish Commission at
Woods Hole, was of unusual
size and weighed over twenty
pounds.

THE ECONOMIC IMPORTANCE OF ANIMALS 199

Several other common crustaceans are near relatives of the crayfish.
Among them are the shrimp and prawn, thin-shelled, active crustaceans
common along our eastern coast. In spite of the fact that they form a
large part of the food supply of many marine animals, especially fish,
they do not appear to be decreasing in numbers. They are also used

as food by man, the shrimp fish-

eries in this country aggregating
over $1,000,000 yearly.

Another edible crustacean of
considerable economic impor
tance is the blue crab. Crabs
are found inhabiting muddy bot
toms ; in such localities they are
caught in great numbers in nets
or traps baited with decaying

The edible blue crab. (From a photograph
loaned by the American Museum of
Natural History.)

meat. They are, indeed, among
our most valuable sea scavengers,
although they are carnivorous
hunters as well. The young crabs differ considerably in form from the
adult. They undergo a complete metamorphosis (change of form).
Immediately after molting or shedding of the outer shell in order to grow
larger, crabs are greatly desired by man as an article of food. They are
then known as " shedders," or soft-shelled crabs.

Mollusks as Food. Oysters are never found in muddy localities, for in
such places they would be quickly smothered by the sediment in the
water. They are found in nature clinging to stones or on shells or other
objects which project a little above the bottom. Here food is abundant

and oxygen is obtained from the water sur
rounding them. Hence oyster raisers throw
oyster shells into the water and the young
oysters attach themselves.

In some parts of Europe and this country
where oysters are raised artificially, stakes
or brush are sunk in shallow water so that
the young oyster, which is at first free-
swimming, may escape the danger of smothering on the bottom. After
the oysters are a year or two old, they are taken up and put down in
deeper water as seed oysters. At the age of three and four years they
are ready for the market.
The oyster industry is one of the most profitable of our fisheries. Nearly

The oyster.

200 THE ECONOMIC IMPORTANCE OF ANIMALS

$15,000,000 a year has been derived during the last decade from such
sources. Hundreds of boats and thousands of men are engaged in dredg
ing for oysters. Three of the most important of our oyster grounds are
Long Island Sound, Narragansett Bay, and Chesapeake Bay.

Sometimes oysters are artificially " fattened " by placing them on beds
near the mouths of fresh-water streams. Too often these streams are the

bearers of much sewage*
and the oyster, which lives
on microscopic organisms,
takes in a number of bac
teria with other food.
Thus a person might be
come infected with the
typhoid bacillus by eating
raw oysters. State and
city supervision of the
oyster industry makes this
possibility very much less
than it was a few years
ago, as careful bacterio
logical analysis of the
surrounding water is con
stantly made by com
petent experts.

Clams. Other bivalve
mollusks used for food are
clams and scallops. Two
species of the former are
known to New Yorkers,

one as the " round," an-
This diagram shows how cases of intestinal disease ,, ,-, ,, , ,,

(typhoid and diarrhea) have been traced to ther as the Ion 8 or
oysters from a locality where they were "fat- " soft-shelled " clams. The
tened" in water contaminated with sewage. f ormer ( Venus mercenaria)

(Loaned by
History.)

American Museum of Natural

was called by the Indians
" quahog," and is still so
called in the Eastern states. The blue area of its shell was used by the
Indians to make wampum, or money. The quahog is now extensively
used as food. The " long " clam (My a arenaria) is considered better
eating by the inhabitants of Massachusetts and Rhode Island. This
clam was highly prized as food by the Indians. The clam industries of

THE ECONOMIC IMPORTANCE OF ANIMALS 201

the eastern coast aggregate nearly $1,000,000 a year. The dredging for
scallops, another molluscan delicacy, forms an important industry along
certain parts of the eastern coast.

Fish as Food. Fish are used as food the world over. From
very early times the herring were pursued by the Norsemen.
Fresh-water fish, such as
whitefish, perch, pickerel,
pike, and the various mem
bers of the trout family, are
esteemed food and, espe
cially in the Great Lake
region, form important fish
eries. But by far the most
important food fishes arc
those which are taken in
salt water. Here we have
two types of fisheries, those

where the fish COmeS Up Salmon leaping a fall on their way to their
a river to spawn, as the spawning beds. (Photographed by Dr.

John A. Sampson.)

salmon, sturgeon, or shad,

and those in which fishes are taken on their feeding grounds in
the open ocean. Herring are the world's most important catch,
though not in this country. Here the salmon of the western

Globe Fisheries.

202 THE ECONOMIC IMPORTANCE OF ANIMALS

coast is taken to the value of over $13,000,000 a year. Cod
fishing also forms an important industry; over 7000 men being
employed and over $2,000,000 of codfish being taken each year
in this country.

Hundreds of other species of fish are used as food, the fish that
is nearest at hand being often the cheapest and best. Why,
for example, is the flounder so cheap in the New York markets?
In what waters are the cod and herring fisheries, sardine, oyster,
sponge, pearl oyster? (See chart on page 201.)

Amphibia and Reptiles as Food. Frogs' legs are esteemed a
delicacy. Certain reptiles are used as food by people of other
nationalities, the Iguana, a Mexican lizard, being an example.
Many of the sea-water turtles are of large size, the leatherback and
the green turtle often weighing six hundred to seven hundred
pounds each. The flesh of the green turtle and especially of the
diamond-back terrapin, an animal found in the salt marshes along
our southeastern coast, is highly esteemed as food. Unfortunately
for the preservation of the species, these animals are usually taken
during the breeding season when they go to sandy beaches to lay
their eggs.

Birds as Food. Birds, both wild and domesticated, form part
of our food supply. Unfortunately our wild game birds are dis
appearing so fast that we should not consider them as a source
of food. Our domestic fowls, turkey, ducks, etc., form an impor
tant food supply and poultry farms give lucrative employment
to many people. Eggs of domesticated birds are of great impor
tance as food, and egg albumin is used for other purposes,
clarifying sugars, coating photographic papers, etc.

Mammals as Food. When we consider the amount of wealth
invested in cattle and other domesticated animals bred and used
for food in the United States, we see the great economic impor
tance of mammals. The United States, Argentina, and Australia
are the greatest producers of cattle. In this country hogs are
largely raised for food. They are used fresh, salted, smoked as
ham and bacon, and pickled. Sheep, which are raised in great
quantities in Australia, Argentina, Russia, Uruguay, and this
country, are one of the world's greatest meat supplies.

THE ECONOMIC IMPORTANCE OF ANIMALS 203

Goats, deer, many larger game animals, seals, walruses, etc.,
give food to people who live in parts of the earth that are less
densely populated.

Domesticated Animals. When man emerged from his savage
state on the earth, one of the first signs of the beginning of civili
zation was the domestication
of animals. The dog, the cow,
sheep, and especially the horse,
mark epochs in the advance of
civilization. Beasts of burden
are used the world over, horses
almost all over the world, cer
tain cattle, as the water buffalo,
in tropical Malaysia; camels,
goats, and the llama are also
used as draft animals in some
other countries.

Man's wealth in many parts
of the world is estimated in
terms of his cattle or herds of
sheep. So many products come
from these sources that a long
list might be given, such as
meats, milk, butter, cheese,
wool, or other body coverings,
leather, skins, and hides used

Feeding silkworms. The caterpillars are
the white objects in the trays.

for other purposes. Great industries are directly dependent upon
our domesticated animals, as the making of shoes, the manu
facture of woolen cloth, the tanning industry, and many others.

Uses for Clothing. The manufacture of silk is due to the pro
duction of raw silk by the silkworm, the caterpillar of a moth.
It lives upon the mulberry and makes a cocoon from which the silk
is wound. The Chinese silkworm is now raised to a slight extent
in southern California. China, Japan, Italy, and France, because
of cheaper labor, are the most successful silk-raising countries.

The use of wool gives rise to many great industries. After the
wool is cut from the sheep, it has to be washed and scoured to

204 THE ECONOMIC IMPORTANCE OF ANIMALS

get out the dirt and grease. This wool fat or lanoline is used in
making soap and ointments. The wool is next " carded," the
fibers being interwoven by the fine teeth of the carding machine
or " combed/' the fibers here being pulled out parallel to eacli
other. Carded wool becomes woolen goods; combed wool,
worsted goods. The wastes are also utilized, being mixed with

" shoddy " (wool from
cloth cuttings or rags)
to make woolen goods
of a cheap grade.

Goat hair, especially
that of the Angora and
the Cashmere goat, has
much use in the cloth
ing industries. Camel's
hair and alpaca are
also used.

Fur. The furs of
many domesticated and
wild animals are of im
portance. The Carniv-
ora as a group are of
much economic importance as the source of most of our fur. The
fur seal fisheries alone amount to many "millions of dollars annu
ally. Otters, skunks, sables, weasels, foxes, and minks are of
considerable importance as fur producers. Even cats are now
used for fur, usually masquerading under some other name. The
fur of the beaver, one of the largest of the rodents or gnawing
mammals, is of considerable value, as are the coats of the
chinchilla, muskrats, squirrels, and other rodents. The fur of the
rabbit and nutria are used in the manufacture of felt hats. The
quills of the porcupines (greatly developed and stiffened hairs)
have a slight commercial value.

Conservation of Fur-bearing Animals Needed. As time goes
on and the furs of wild animals become scarcer and scarcer through
overkilling, we find the need for protection and conservation of
many of these fast-vanishing wild forms more and more impera-

Polar bear, a fur-bearing mammal which is rapidly
being exterminated. Why ?

THE ECONOMIC IMPORTANCE OF ANIMALS 205

live. Already breeding of some fur-bearing animals has been
tried with success, and cheap substitutes for wild animal skins are
coming more and more into the markets. Black-fox breeding has
been tried successfully in Prince Edward Island, Canada, $2500
to $3000 being given for a single skin. Skunk, marten, and mink
are also being bred for the market. Game preserves in this
country and Canada are also helping to preserve our wild fur-
bearing animals.

Animal Oils. Whale oil, obtained from the fat or " blubber "
of whales, is used extensively for lubricating. Neat's-foot oil
comes from the feet of cattle and is also used in lubrication.
Tallow and lard, two fats from cattle, sheep, and pigs, have
so many well-known uses that comment is unnecessary. Cod-
liver oil is used medically and is well known. But it is not
so widely known that a fish called the menhaden or " moss
bunkers " of the Atlantic coast produces over 3,000,000 gal
lons of oil every year and is being rapidly exterminated in
consequence.

Hides, Horns, Hoofs, etc. Leathers, from cattle, horses,
sheep, and goats, are used everywhere. Leather manufacture is
one of the great industries of the Eastern states, hundreds of
millions of dollars being invested in its manufacturing plants.
Horns and bones are utilized for making combs, buttons, handles
for brushes, etc. Glue is made from the animal matter in bones.
Ivory, obtained from elephant, walrus, and other tusks, forms a
valuable commercial product. It is largely used for knife
handles, piano keys, combs, etc.

Perfumes. The musk deer, musk ox, and muskrat furnish a
valuable perfume called musk. Civet cats also give us a somewhat
similar perfume. Ambergris, a basis for delicate perfumes, comes
from the intestines of the sperm whale.

Protozoa. The Protozoa have played an important part in rock
building. The chalk beds of Kansas and other chalk formations are
made up to a large extent of the tiny skeletons of Protozoa, called
Foraminifera. Some limestone rocks are also composed in large part of
such skeletons. The skeletons of some species are used to make a polish
ing powder.

206 THE ECONOMIC IMPORTANCE OF ANIMALS

Sponges. The sponges of commerce have the skeleton composed of
tough fibers of material somewhat like that of cow's horn. This fiber is
elastic and has the power of absorbing water. In a living state, the
horny fiber sponge is a dark-colored fleshy mass, usually found attached to
rocks. The warm waters of the Mediterranean Sea and the West Indies
furnish most of our sponges. The sponges are pulled up from their resting
place on the bottom, by means of long-handled rakes operated by men in
boats or are secured by divers. They are then spread out on the shore in
the sun, and the living tissues allowed to decay; then after treatment
consisting of beating, bleaching, and trimming, the bath sponge is ready

for the market. Some
forms of coral are of com
mercial value. The red
coral of the Mediter
ranean Sea is the best
example.

Pearls and Mother of
Pearl. Pearls are prized
the world over. It is a
well-known fact that even
in this country pearls of
some value are sometimes'
found within the shells of
the fresh-water mussel
and the oyster. Most of
the finest, however, come
from the waters around
Ceylon. If a pearl is cut open and examined carefully, it is found to be
a deposit of the mother-of-pearl layer of the shell around some central
structure. It has been believed that any foreign substance, as a grain
of sand, might irritate the mantle at a given point, thus stimulating it
to secrete around the substance. It now seems likely that most perfect
pearls are due to the growth within the mantle of the clam or oyster
of certain parasites, stages in the development of a flukeworm. The
irritation thus set up in the tissue causes mother of pearl to be deposited
around the source of irritation, with the subsequent formation of a pearl.
The pearl-button industry in this country is largely dependent upon the
fresh-water mussel, the shells of which are used. This mussel is being so
rapidly depleted that the national government is working out a means of
artificial propagation of these animals.

In some countries little metal images of Buddha are
placed within the shells of living pearl oysters or
clams. Over these the mantle of the animal
secretes a layer of mother of pearl as is shown in
the picture.

THE ECONOMIC IMPORTANCE OF ANIMALS 207

Honey and Wax. Honeybees 1 are kept in hives. A colony
consists of a queen, a female who lays the eggs for the colony, the
drones, whose duty it
is to fertilize the eggs,
and the workers.

The cells of the comb
are built by the workers
out of wax secreted
from the under surface
of their bodies. The
wax is cut off in thin
plates by means of the
wax shears between
the two last joints of
the hind legs. These
cells are used to place
the eggs of the queen
in, one egg to each
cell, and the young are
hatched after three
days, to begin life as
footless white grubs.

The young are fed
for several days, then
shut up in the cells
and allowed to form pupae. Eventually they break their cells and
take their place as workers in the hive, first as nurses for the
young and later as pollen gatherers and honey makers.

We have already seen (pages 37 to 39) that the honeybee
gathers nectar, which she swallows, keeping the fluid in her crop
until her return to the hive. Here it is forced out into cells of

1 Their daily life may be easily watched in the schoolroom, by means of one of the
many good and cheap observation hives now made to be placed in a window frame.
Directions for making a small observation hive for school work can be found in
Hodge, Nature Study and Life, Chap. XIV. Bulletin No. 1, U. S. Department of
Agriculture, entitled The Honey Bee, by Frank Benton, is valuable for the amateur
beekeeper. It may be obtained for twenty-five cents from the Superintendent of
Documents, Union Building, Washington, D.C.

Cells of honeycomb, queen cell on right at bottom.

208 THE ECONOMIC IMPORTANCE OF ANIMALS

the comb. It is now thinner than what we call honey. To thicken
it, the bees swarm over the open cells, moving their wings very
rapidly, thus evaporating some of the water. A hive of bees
have been known to make over thirty-one pounds of honey in a
single day, although the average is very much less than this. It
is estimated from twenty to thirty millions of dollars' worth of
honey and wax are produced each year in this country.

Cochineal and Lac. Among other products of insect origin
is cochineal, a red coloring matter, which consists of the dried
bodies of a tiny insect, one of the plant lice which lives on the
cactus plants in Mexico and Central America. The lac insect,
another one of the plant lice, feeds on the juices of certain trees
in India and pours out a substance from its body which after

treatment forms shellac. Shel
lac is of much use as a basis
for varnish.

Gall Insects. Oak galls,
growths caused by the sting of
wasp-like insects, give us prod
ucts used in ink making, in tan
ning, and in making pyrogaliic
acid which is much used in
developing photographs.

Insects destroy Harmful
Plants or Animals. Some
forms of animal life are of great
importance because of their de
struction of harmful plants or
animals.

A near relative of the bee,
called the ichneumon fly, does man indirectly considerable good
because of its habit of laying its eggs and rearing the young in
the bodies of caterpillars which are harmful to vegetation. Some
of the ichneumons even bore into trees in order to deposit their
eggs in the larvae of wood-boring insects. It is safe to say that
the ichneumons save millions of dollars yearly to this country.
Several beetles are of value to man. Most important of these

An insect friend of man. An ichneumon
fly boring in a tree to lay its eggs in
the burrow of a boring insect harmful
to that tree.

THE ECONOMIC IMPORTANCE OF ANIMALS 209

is the natural enemy of the orange-tree scale, the ladybug, or
ladybird beetle. In New York state it may often be found feed
ing upon the plant lice, or aphids, which live on rosebushes. The
carrion beetles and many water beetles act as scavengers. The
sexton beetles bury dead carcasses of animals. Ants in tropical
countries are particularly useful as scavengers.

Insects, besides pollinating flowers, often do a service by eating
harmful weeds. Thus many harmful plants are kept in check.
We have noted that they spin silk, thus forming clothing ; that
in many cases they are preyed upon, and that they supply an
enormous multitude of birds, fishes, and other animals with food.

Use of the Toad. The toad is of great economic importance
to man because of its diet. No less than eighty-three species of
insects, mostly injuri
ous, have been proved
to enter into the dietary.
A toad has been ob
served to snap up one
hundred and twenty-
eight flies in half an
hour. Thus at a low
estimate it could easily
destroy one hundred
insects during a day
and do an immense ser
vice to the garden dur
ing the summer. It has
been estimated by Kirk-
land that a single toad may, on account of the cutworms which
it kills, be worth $19.88 each season it lives, if the damage done
by each cutworm be estimated at only one cent. Toads also
feed upon slugs and other garden pests.

Birds eat Insects. The food of birds makes them of the
greatest economic importance to our country. This is because
of the relation of insects to agriculture. A large part of the diet
of most of our native birds includes insects harmful to vegetation.
Investigations undertaken by the United States Department of

HUNTER, CIV. BI. 14

The common toad, an insect eater.

210 THE ECONOMIC IMPORTANCE OF ANIMALS

Agriculture (Division of Biological Survey) show that a surpris
ingly large number of birds once believed to harm crops really
perform a service by killing injurious insects. Even the much
maligned crow lives to some extent upon insects. Swallows in the
Southern states kill the cotton-boll weevil, one of our worst insect

pests. Our earliest visitor, the
bluebird, subsists largely on injuri
ous insects, as do woodpeckers,
cuckoos, kingbirds, and many
others. The robin, whose pres
ence in the cherry tree we resent,
during the rest of the summer
does much good by feeding upon
noxious insects. Birds use the
food substances which are most
abundant around them at the
time. 1

Birds eat Weed Seeds. Not
only do birds aid man in his
battles with destructive insects,
but seed-eating birds eat the seeds
of weeds. Our native sparrows
(not the English sparrow), the

Food of some common birds. Which mourning dove, bobwhite, and
of the above birds should be pro- other birds feed largely upon the

seeds of many of our common

weeds. This fact alone is sufficient to make birds of vast eco
nomic importance.

1 The following quotation from I. P. Trimble, A Treatise on the Insect Enemies of
Fruit and Shade Trees, bears out this statement : "On the fifth of May, 1864, . . -
seven different birds . . . had been feeding freely upon small beetles. . . . There
was a great flight of beetles that day; the atmosphere was teeming with them.
A few days after, the air was filled with Ephemera flies, and the same species of birds
were then feeding upon them."

During the outbreak of Rocky Mountain locusts in Nebraska in 18741877,
Professor Samuel Aughey saw a long-billed marsh wren carry thirty locusts to her
young in an hour. At this rate, for seven hours a day, a brood would consume 210
locusts per day, and the passerine birds of the eastern half of Nebraska, allowing
only twenty broods to the square mile, would destroy daily 162,771,000 of the

MERICAN CROW CAT BIRO ENGLISH SPARROW

THE ECONOMIC IMPORTANCE OF ANIMALS 211

Not all birds are seed or insect feeders. Some, as the cormorants,
ospreys, gulls, and terns, are active fishers. Near large cities
gulls especially act as scavengers, destroying much floating gar
bage that otherwise might be washed ashore to become a menace
to health. The vultures of India and semitropical countries are
of immense value as scavengers. Birds of prey (owls) eat living
mammals, including many rodents ; for example, field mice, rats,
and other pests.

Extermination of our Native Birds. Within our own times
we have witnessed the almost total extermination of some species
of our native birds. The American passenger pigeon, once very
abundant in the Middle West, is now extinct. Audubon, the
greatest of all American bird lovers, gives a graphic account of
the migration of a flock of these birds. So numerous were they
that when the flock rose in the air the sun was darkened, and
at night the weight of the roosting birds broke down large branches
of the trees in which they rested. To-day not a single wild speci
men of this pigeon can be found, because they were slaughtered
by the hundreds of thousands during the breeding season.
The wholesale killing of the snowy egret to furnish ornaments
for ladies' headwear is another example of the improvidence
of our fellow-countrymen . Charles Dudley Warner said, " Feathers
do not improve the appearance of an ugly woman, and a pretty
woman needs no such aid." Wholesale killing for plumage, eggs,
and food, and, alas, often for mere sport, has reduced the number
of our birds more than one half in thirty states and territories within
the past fifteen years. Every crusade against indiscriminate
killing of our native birds should be welcomed by all thinking

pests. The average locust weighs about fifteen grains, and is capable each day of
consuming its own weight of standing forage crops, which at $10 per ton would be
worth $1743.26. This case may serve as an illustration of the vast good that is
done every year by the destruction of insect pests fed to nestling birds. And it
should be remembered that the nesting season is also that when the destruction of
injurious insects is most needed ; that is, at the period of greatest agricultural
activity and before the parasitic insects can be depended on to reduce the pests.
The encouragement of birds to nest on the farm and the discouragement of nest
robbing are therefore more than mere matters of sentiment ; they return an actual
cash equivalent, and have a definite bearing on the success or failure of the crops.
Year Book of the Department of Agriculture.

212 THE ECONOMIC IMPORTANCE OF ANIMALS

Americans. The recent McLane bill which aims at the protec
tion of migrating birds and the bird-protecting clause of the
recently passed tariff bill shows that this country is awaking to
the value of her bird life. Without the birds the farmer would
have a hopeless fight against insect pests. The effect of killing
native birds is now well seen in Italy and Japan, where insects are
increasing and do greater damage each year to crops and trees.

Of the eight hundred or more species of birds in the United
States, only six species of hawks (Cooper's and the sharp-shinned
hawk in particular), and the great horned owl, which prey upon
useful birds ; the sapsucker, which kills or injures many trees be
cause of its fondness for the growing layer of the tree ; the bobolink,
which destroys yearly $2,000,000 worth of rice in the South ; the
crow, which feeds on crops as well as insects; and the English
sparrow, may be considered as enemies of man.

The English Sparrow. The English sparrow is an example of
a bird introduced for the purpose of insect destruction, that has
done great harm because of its relation to our native birds. In
troduced at Brooklyn in 1850 for the purpose of exterminating
the cankerworm, it soon abandoned an insect diet and has driven
out most of our native insect feeders. Investigations by the
United States Department of Agriculture have shown that in
the country these birds and their young feed to a large extent
upon grain, thus showing them to be injurious to agriculture.
Dirty and very prolific, it already has worked its way from the
East as far as the Pacific coast. In this area the bluebird, song
sparrow, and yellowbird have all been forced to give way, as well
as many larger birds of great economic value and beauty. The
English sparrow has become a pest especially in our cities, and
should be exterminated in order to save our native birds. It is
feared in some quarters that the English starling which has re
cently been introduced into this country may in time prove a
pest as formidable as the English sparrow.

Food of Snakes. Probably the most disliked and feared of all
animals are the snakes. This feeling, however, is rarely deserved,
for, on the whole, our common snakes are beneficial to man. The
black snake and the milk snake feed largely on injurious rodents

THE ECONOMIC IMPORTANCE OF ANIMALS 213

(rats, mice, etc.), the pretty
green snake eats injurious in
sects, and the little DeKay
snake feeds partially on slugs.
If it were not that the rattle
snake and the copperhead are
venomous, they also could be
said to be useful, for they live
on English sparrows, rats, mice,
moles, and rabbits.

Food of Herbivorous Ani
mals. We must not forget
that other animals besides in
sects and birds help to keep
down the rapidly growing weeds.
Herbivorous animals the world
over destroy, besides the grass
which they eat, untold multi
tudes of weeds, which, if un
checked, would drive out the
useful occupants of the pasture,
the grasses and grains.

HARM DONE BY

ANIMALS

Economic Loss from Insects.
- The money value of crops,
forest trees, stored foods, and
other material destroyed annu
ally by insects is beyond belief.
It is estimated that they get
one tenth of the country's crops,
at the lowest estimate a matter
of some $300,000,000 yearly.
:i The common schools of the
country cost in 1902 the sum
of $235,000,000, and all higher

This shows how some snakes (constric
tors) kill and eat their prey. (Series
photographed by C. W. Beebe and
Clarence Halter.)

214 THE ECONOMIC IMPORTANCE OF ANIMALS

institutions of learning cost less than $50,000,000, making the
total cost of education in the United States considerably less than
the farmers lost from insect ravages.

" Furthermore, the yearly losses from insect ravages aggregate
nearly twice as much as it costs to maintain our army and navy ;
more than twice the loss by fire; twice the capital invested in
manufacturing agricultural implements; and nearly three times
the estimated value of the products of all the fruit orchards, vine
yards, and small fruit farms in the country." SLINGERLAND.

The total yearly value of all farm and forest products in New
York is perhaps $150,000,000, and the one tenth that the insects
get is worth $15,000,000.

Insects which damage Garden and Other Crops. The grass
hoppers and the larvae of various moths do considerable harm

here, especially the " cab
bage worm," the cutworm,
a feeder on all kinds of
garden truck, and the corn
worm, a pest on corn, cot
ton, tomatoes, peas, and
beans.

Among the beetles which
are found in gardens is
the potato beetle, which
destroys the potato plant.
This beetle formerly lived
in Mexico upon a wild
plant of the same family

Cotton-boll weevil, a, larva ; &,pupa; c, adult. aS the P otato > and came
Enlarged about four times. (Photographed north upon the introduc
tion of the potato into

Colorado, evidently preferring cultivated forms to wild forms of
this family.

The one beetle doing by far the greatest harm in this country is
the cotton-boll weevil. Imported from Mexico, since 1892 it has
spread over eastern Texas and into Louisiana. The beetle lays
its eggs in the young cottorf fruit or boll, and the larvae feed upon

THE ECONOMIC IMPORTANCE OF ANIMALS 215

the substance within the boll. It is estimated that if unchecked
this pest would destroy yearly one half of the cotton crop,
causing a loss of $250,000,000. Fortunately, the United States
Department of Agriculture is at work on the problem, and, while
it has not found any way of exterminating the beetle as yet, it has
been found that, by planting more hardy varieties of cotton, the
crop matures earlier and ripens before the weevils have increased
in sufficient numbers to destroy the crop (see page 126).

The bugs are among our most destructive insects. The most
familiar examples of our garden pests are the squash bug; the
chinch bug, which yearly does damage estimated at $20,000,000, by
sucking the juice from the leaves of grain; and the plant lice, or
aphids. One, living on the grape, yearly destroys immense num
bers of vines in the vineyards of France, Germany, and California.

Insects which harm Fruit and Forest Trees. Great damage is
annually done trees by the larvae of moths. Massachusetts has

Female tussock moth which has
just emerged from the cocoon
at the left, upon which it has
deposited over two hundred
eggs. (Photograph by
Davis on.)

Caterpillar of tussock moth,
graph by Davison.)

(Photo-

already spent over $3,000,000 in trying to exterminate the imported
gypsy moth. The codling moth, which bores into apples and pears,
is estimated to ruin yearly $3,000,000 worth of fruit in New York
alone, which is by no means the most important apple region of
the United States. Among these pests, the most important to
the dweller in a large city is the tussock moth, which destroys our
shade trees. The caterpillar may easily be recognized by its hairy,

216 THE ECONOMIC IMPORTANCE OF ANIMALS

tufted red head. The eggs are laid on the bark of shade trees in
what look like masses of foam. (See figure on page 215.) By
collecting and burning the egg masses in the fall, we may save
many shade trees the following year.

The larvae of some moths damage the trees by boring into the
wood of the tree on which they live. Such are the peach, apple,
and other fruit-tree borers common in our orchards. Many beetle
larvae also live in trees and kill annually thousands of forest and
shade trees. The hickory borer threatens to kill all the hickory,
trees in the Eastern states.

Among the bugs most destructive to trees are the scale insect
and the plant lice. The San Jose scale, a native of China, was
introduced into the fruit groves of California about 1870 and has
spread all over the country. A ladybird beetle, which has also been
imported, is the most effective agent in keeping this pest in check.

Insects of the House or Storehouse. Weevils are the greatest
pests, frequently ruining tons of stored corn, wheat, and other
cereals. Roaches will eat almost anything, even clothing; they
are especially fond of all kinds of breadstuffs. The carpet beetle
is a recognized foe of the housekeeper, the larvae feeding upon all
sorts of woolen material. The larvae of the clothes moth do an
immense amount of damage, especially to stored clothing. Fleas,
lice, and particularly bedbugs are among man's personal foes.
Besides being unpleasant they are believed to be disease carriers
and as such should be exterminated. 1

Food of Starfish. Starfish are enormously destructive to young clams
and oysters, as the following evidence, collected by Professor A. D.Mead,
of Brown University, shows. A single starfish was confined in an aqua
rium with fifty-six young clams. The largest clam was about the length
of one arm of the starfish, the smallest about ten millimeters in length.
In six days every clam in the aquarium was devoured. Hundreds of
thousands of dollars' damage is done annually to the oysters in Connecti
cut alone by the ravages of starfish. During the breeding season of the
clam and oyster the boats dredge up tons of starfish which are thrown on
shore to die or to be used as fertilizer.

1 Directions for the treatment of these pests may be found in pamphlets issued
by the U. S. Department of Agriculture,

THE ECONOMIC IMPORTANCE OF ANIMALS 217

THE RELATIONS OF ANIMALS TO DISEASE

The Cause of Malaria. The study of the life history and
habits of the Protozoa has resulted in the finding of many parasitic
forms, and the consequent expla
nation of some kinds of disease.
One parasitic protozoan like an
amoeba is called Plasmodium ma
laria. It causes the disease
known as malaria. When a mos
quito (the anopheles) sucks the
blood from a person having mala
ria this parasite passes into the
stomach of the
mosquito. Af
ter completing
a part of its life
history within
the mosquito's
body the para
site establishes
itself within the
glands which
secrete the sa
liva of the mos
quito. After
about eight
days, if the in
fected mosquito
bites a person,
some of the
parasites are
introduced into

the blood along with the saliva. These parasites enter the cor
puscles of the blood, increase in size, and then form spores. The
rapid process of spore formation results in the breaking down
of the blood corpuscles and the release of the spores, and the

The life history of the malarial parasite. This cut of the
malarial parasite shows parts of the body of the mosquito
and of man. To understand the life history begin at the
point where the mosquito injects the crescent-shaped
bodies into the blood of man. Notice tha.t after the spores
are released from the corpuscles of man two kinds of cells
may be formed. These are probably a sexual stage. Devel
opment within the body of the mosquito will only take
place when the parasite is taken into its body at this
sexual stage.

218 THE ECONOMIC IMPORTANCE OF ANIMALS

poisons they manufacture, into the blood. This causes the chill
followed by the fever so characteristic of malaria. The spores
may again enter the blood corpuscles and in forty-eight or
seventy-two hours repeat the process thus described, depending
on the kind of malaria they cause. The only cure for the
disease is quinine in rather large doses. This kills the parasites
in the blood. But quinine should not be taken except under
a physician's directions.

The Malarial Mosquito. Fortunately for mankind, not all
mosquitoes harbor the parasite which causes malaria. The harm
less mosquito (culex) may be usually distinguished from the
mosquito which carries malaria (anopheles) by the position taken

How to distinguish the harmless mosquito (culex), a, from the malarial mosquito
(anopheles), b, when at rest. Notice the position of legs and body.

when at rest. Culex lays eggs in tiny rafts of one hundred or more
eggs in any standing water ; thus the eggs are distinguished from
those of anopheles, which are not in rafts. Rain barrels, gutters,
or old cans may breed in a short time enough mosquitoes to stock
a neighborhood. The larvae are known as wigglers. They breathe
through a tube in the posterior end of the body, and may be rec
ognized by their peculiar movement when on their way to the sur
face to breathe. The pupa, distinguished by a large thoracic
region, breathes through a pair of tubes on the thorax. The fact
that both larvse and pupae take air from the surface of the water
makes it possible to kill the mosquito during these stages by pour
ing oil on the surface of the water where they breed. The intro
duction of minnows, gold fish, or other small fish which feed

THE ECONOMIC IMPORTANCE OF ANIMALS 219

upon the larvae in the water where the mosquitoes breed will do
much to free a neighborhood from this pest. Draining swamps
or low land which holds water after a rain is another method of
extermination. Some of the mosquito-infested districts around
New York City have been almost freed from mosquitoes by
draining the salt marshes where they breed. Long shallow
trenches are so built as to tap and drain off any standing water in
which the eggs might be laid. In this way the mosquito has

been almost exterminated

along some parts of our
New England coast.

Since the beginning of
historical times, malaria
has been prevalent in
regions infested by mos
quitoes. The ancient city
of Rome was so greatly
troubled by periodic out
breaks of malarial fever
that a goddess of fever
came to be worshiped in
order to lessen the severity
of what the inhabitants
believed to be a divine visitation. At the present time the
malaria of Italy is being successfully fought and conquered by
the draining of the mosquito-breeding marshes. By a little care
fully directed oiling of water a few boys may make an almost
uninhabitable region absolutely safe to live in. Why not try it
if there are mosquitoes in your neighborhood ?

Yellow Fever and Mosquitoes. Another disease carried by
mosquitoes is yellow fever. In the year 1878 there were 125,000
cases and 12,000 deaths in the United States, mostly in Alabama,
Louisiana, and Mississippi. During the French occupation of the
Panama Canal zone the work was at a standstill part of the time
because of the ravages of yellow fever. Before the war with Spain
thousands of people were ill in Cuba. But to-day this is changed,
and yellow fever is under almost complete control, both here and

Swamps are drained and all standing water
covered with a film of oil in order to ex
terminate mosquitoes. Why is the oil
placed on the surface of the water ?

220 THE ECONOMIC IMPORTANCE OF ANIMALS

in the Canal zone, where the mosquito (stegomyia) which carries

yellow fever exists.

. This is due to the

experiments during the
summer of 1900 of a
Commission of United
States army officers,
headed by Dr. Walter
Reed. Of these men one,
Dr. Jesse Lazear, gave up
his life to prove experi
mentally that yellow fever
was caused by mosquitoes.
He allowed himself to be
bitten by a mosquito that
was known to have bitten
a yellow fever patient,
contracted the disease,
and died a martyr to
science. Others, soldiers,
volunteered to further test
by experiment how the
disease was spread, so
that in the end Dr. Reed
was able to prove to the
world that if mosquitoes
could be prevented from
biting people who had
yellow fever the disease
could not be spread. The
accompanying illustration
shows the result of this

Notice the difference in the number of yearly knowledge for the city of
deaths from yellow fever before and after Ha van a For VP^TX Ha
the American occupation of Havana. -tiavana. P years ia-

vana was considered one

of the pest spots of the West Indies. Visitors shunned this port
and commerce was much affected by the constant menace of

THE ECONOMIC IMPORTANCE OF ANIMALS 221

yellow fever. At the time of the American occupation after the
war with Spain, the experiments referred to above were under
taken. The city was cleaned Up, proper sanitation introduced,
screens placed in most buildings, and the breeding places of the
mosquitoes were so nearly destroyed that the city was practically
free from mosquitoes. The result, so far as yellow fever was con
cerned, was startling, as you can see by reference to the chart.
Notice also the rise in the death rate when the young Cuban
Republic took control. How do
you account for that ? We all know
what American scientific medicine
and sanitation is doing in Panama
and in the Philippines.

Other Protozoan Diseases.
Many other diseases of man are
probably caused by parasitic pro
tozoans. Dysentery of one kind
appears to be caused by the pres
ence of an amceba-like animal in the
digestive tract which comes usually
through an impure water supply.
Smallpox, rabies, and possibly other
diseases are caused by protozoans. Smallpox, which was once the
most dreaded disease known to man, because of its spread in
epidemics, has been conquered by vaccination, of which we shall
learn more later. The death rate from rabies or hydrophobia has
in a like manner been greatly reduced by a treatment founded on
the same principles as vaccination and invented by Louis Pasteur.

Another group of protozoan parasites are called trypanosomes.
These are parasitic in insects, fish, reptiles, birds, and mammals
in various parts of the world. They cause various diseases of
cattle and other domestic animals, being carried to the animal in
most cases by flies. One of this family is believed to live in the
blood of native African zebras and antelopes ; seemingly it does
them no harm. But if one of these parasites is transferred by the
dreaded tsetse fly to one of the domesticated horses or cattle of
the colonist of that region, death of the animal results.

222 THE ECONOMIC IMPORTANCE OF ANIMALS

Another fly carries a species of trypanosome to the natives of
Central Africa, which causes " the dreaded and incurable sleep
ing sickness." This disease carries off more than fifty thousand
natives yearly, and many Europeans have succumbed to it. Its
ravages are now largely confined to an area near the large Central
African lakes and the Upper Nile, for the fly which carries the
disease lives near water, seldom going more than 150 feet from
the banks of streams or lakes. The British government is now
trying to control the disease in Uganda by moving all the villages
at least two miles from the lakes and rivers. Among other
diseases that may be due to protozoans is kala-agar, a fever in hot
Asiatic countries which is probably carried by the bedbug, and
African tick fever, probably carried by a small insect called the
tick. Bubonic plague, one of the most dreaded of all infectious
diseases, is carried to man by fleas from rats. In this country
many fatal diseases of cattle, as " tick," or Texas cattle fever, are
probably caused by protozoans.

The Fly a Disease Carrier. We have already seen that mos
quitoes of different species carry malaria and yellow fever. An
other rather recent addition to the black list is the house fly or
typhoid fly. We shall see later with what reason this name
is given. The development of the typhoid fly is extremely
rapid. A female may lay from one hundred to two hundred
eggs. These are usually deposited in filth or manure. Dung heaps

d^cJ^

Life history of house flies, showing from left to right the eggs, larvae,
pupae, and adult flies. (Photograph, about natural size, by Overton.)

THE ECONOMIC IMPORTANCE OF ANIMALS 223

The foot of a fly, showing the
hooks, hairs, and pads
which collect and carry
bacteria. The fly doesn't
wipe his feet.

about stables, privy vaults, ash heaps, uncared-for garbage cans,
and fermenting vegetable refuse form the best breeding places for
flies. In warm weather, the eggs hatch a
day or so after they are laid and become
larvae, called maggots. After about one
week of active feeding, these wormlike
maggots become quiet and go into the
pupal stage, whence under favorable con
ditions they emerge within less than an
other week as adult flies. The adults
breed at once, and in a short summer there
may be over ten generations of flies. This
accounts for the great number. Fortu
nately relatively few flies survive the
winter. The membranous wings of the
adult fly appear to be two in number, a
second pair being reduced to tiny knobbed
hairs called balancers. The head is freely
movable, with large compound eyes. The mouth parts form a
proboscis, which is tonguelike, the animal obtaining its food by
lapping and sucking. The foot shows a wonderful adaptation for

clinging to smooth surfaces.
Two or three pads, each of
which bears tubelike hairs that
secrete a sticky fluid, are found
on its under surface. It is by
this means that the fly is able
to walk upside down, and carry
bacteria on its feet.

The Typhoid Fly a Pest. -
The common fly is recognized
as a pest the world over. Flies
have long been known to spoil
food through their filthy habits,
but it is more recently that the

* <**>* ^* f *p* of

fly was allowed to walk. diseases, caused by bacteria, has

THE ECONOMIC IMPORTANCE OF ANIMALS

, i i

1 1 1 1 j^ ' | 1 | 1 | '

H-H

~T~

1 i ' i^T 1 I ' i ' i '

L F ^

1
i

l
^

1 III 1 1 -J
1 1 1 1 1 1

1 I , ' l\ 1 ' 1 ' 1 ' 1

1 III 1 1 [

Showing how flies may spread disease by
means of contaminating food.

been laid at their door. In a
recent experiment two young
men from the Connecticut
Agricultural Station found that
a single fly might carry on its
feet anywhere from 500 to
6,600,000 bacteria, the average
number being over 1,200,000.
Not all of these germs are
harmful, but they might easily
include those of typhoid fever,
tuberculosis, summer com
plaint, and possibly other
diseases. A recent pamphlet
published by the Merchants'
Association in New York City

shows that the rapid increase of flies during the summer months
has a definite correlation with the increase in the number of cases
of summer complaint. Observations in other cities seem to show
the increase in number of typhoid cases in the early fall is due,
in part at least, to the same
cause. A terrible toll of dis
ease and death may be laid at -
the door of the typhoid fly.

Recently the stable fly has
been found to carry the dread
disease known as infantile
paralysis.

Remedies. Cleanliness
which destroys the breeding _
place of flies, the frequent re- _

moval and destruction of gar
bage, rubbish, and manure, There were 329 typhoid cases in Jackson-

covering of all food when not
in use and especially the care
ful screening of windows and

doors during the breeding

ville, Florida, in 1910, 158 in 1911, 87
in first 10 months of 1912. 80 to 85
per cent of outdoor toilets were made fly
proof during winter of 1910. Account
for the decrease in typhoid after the
flies were kept out of the toilets.

THE ECONOMIC IMPORTANCE OF ANIMALS 225

season, will all play a part in the reduction of flies. To the motto
" swat the fly " should be added, "remove their breeding places!"

Other Insect Disease Carriers. Fleas and bedbugs have been
recently added to those insects proven to carry disease to man.
Bubonic plague, which is primarily a disease of rats, is un
doubtedly transmitted from the infected rats to man by the fleas.
Fleas are also believed to transmit leprosy although this is not
proven.

To rid a house of fleas we must first find their breeding places.
Old carpets, the sleeping places of cats or dogs or any dirty un-
swept corner may hold the eggs of the flea. The young breed in
cracks and crevices,, feeding upon organic
matter there. Eventually they come to live
as adults on their warm-blooded hosts, cats,
dogs, or man. Evidently destruction of the
breeding places, careful washing of all in
fected areas, the use of benzine or gasoline Flea which transmits Bu-
in crevices where the larva? may be hid are ^ onic plague from rat

17 to man.

the most effective methods of extermina
tion. Pets which might harbor fleas should be washed frequently
with a weak (two to three per cent) solution of creolin.

Bedbugs are difficult to prove as an agent in the transmission of
disease but their disgusting habits are sufficient reason for their
extermination. It has been proven by experiment that they may
spread typhoid and relapsing fevers. They prefer human blood
to other food and have come to live in bedrooms and beds because
this food can be obtained there. They are extremely difficult to
exterminate because their flat body allows them to hide in cracks
out of sight. Wooden beds are thus better protection for them
than iron or brass beds. Boiling water poured over the cracks
when they breed or a mixture of strong corrosive sublimate four
parts, alcohol four parts and spirits of turpentine one part, are
effective remedies.

How the Harm done by Insects is Controlled. The com
bating of insects is directed by several bodies of men, all of
which have the same end in view. These are the Bureau of
Entomology of the United States Department of Agriculture,

HUNTER, CIV. BI. 15

226 THE ECONOMIC IMPORTANCE OF ANIMALS

the various state experiment stations, and medical and civic
organizations.

The Bureau of Entomology works in harmony with the other
divisions of the Department of Agriculture, giving the time of its
experts to the problems of controlling insects which, for good or
ill, influence man's welfare in this country. The destruction of
the malarial mosquito and control of the typhoid fly; the de
struction of harmful insects by the introduction of their natural
enemies, plant or animal ; the perfecting of the honeybee (see
Hodge, Nature Study and Life, page 240), and the introduction of
new species of insects to pollinate flowers not native to this country
(see Blastophaga, page 43), are some of the problems to which these
men are now devoting their time.

All the states and territories have, since 1888, established state
experiment stations, which work in cooperation with the govern
ment in the war upon injurious insects. These stations are often
connected with colleges, so that young men who are interested in
this kind of natural science may have opportunity to learn and to
help.

The good done by these means directly and indirectly is very
great. Bulletins are published by the various state stations and
by the Department of Agriculture, most of which may be obtained
free. The most interesting of these from the high school stand
point are the Farmers' Bulletins, issued by
the Department of Agriculture, and the
Nature Study pamphlets issued by the
Cornell University in New York state.

Animals Other than Insects may be Dis
ease Carriers. The common brown rat is
an example of a mammal, harmful to civi
lized man, which has followed in his foot-

This diagram shows how ste P s a11 over the world - Starting from
bubonic plague is carried China, it spread to eastern Europe, thence
* ' to western Europe, and in 1775 it had
obtained a lodgment in this country. In
seventy-five years it reached the Pacific coast, and is now fairly
common all over the United States, being one of the most prolific

THE ECONOMIC IMPORTANCE OF ANIMALS 227

of all mammals. Rats are believed to carry bubonic plague, the
" Black Death " of the Middle Ages, a disease estimated to have
killed 25,000,000 people during the fourteenth century. The rat,
like man, is susceptible to plague ; fleas bite the rat and then biting
man transmit the disease to him. A determined effort is now being
made to exterminate the rat because of its connection with
bubonic plague.

Other Parasitic Animals cause Disease. Besides parasitic
protozoans other forms of animals have been found that cause
disease. Chief among these are certain round and flat worms,
which have come to live as parasites on man and other animals.
A one-sided relationship has thus come into existence where the
worm receives its living from the host, as the animal is called on
which the parasite lives. Consequently the parasite frequently
becomes fastened to its host during adult life and often is reduced
to a mere bag through which the fluid food prepared by its host is
absorbed. Sometimes a complicated life history has arisen from
their parasitic habits. Such is seen in the
life history of the liver fluke, a flatworm
which kills sheep, and in the tapeworm.

Cestodes or Tapeworms. These para
sites infest man and many other vertebrate
animals. The tapeworm (Tcenia solium)
passes through two stages in its life history,
the first within a pig, the second within the
intestine of man. The developing eggs are
passed off with wastes from the intestine
of man. The pig, an animal with dirty
habits, may take in the worm embryos
with its food. The worm develops within
the intestine of the pig, but soon makes its
way into the muscle or other tissues. It
is here known as a bladderworm. If man eats raw or undercooked
pork containing these worms, he may become a host for the tape
worm. Thus during its complete life history it has two hosts.
Another common tapeworm parasitic on man lives part of its life as
an embryo within the muscles of cattle. The adult worm consists

The life cycle of a tape
worm. (1) The eggs are
taken in with filthy food
by the pig ; (2) man
eats undercooked pork
by means of which
the bladder worm (3) is
transferred to his own
intestine (4).

228 THE ECONOMIC IMPORTANCE OF ANIMALS

of a round headlike part provided with hooks, by means of which
it fastens itself to the wall of the intestine. This head now buds
off a series of segmentlike structures, which are practically bags
full of sperms and eggs. These structures, called proglottids,
break off from time to time, thus allowing the developing eggs to
escape. The proglottids have no separate digestive systems, but
the whole body surface, bathed in digested food, absorbs it and is
thus enabled to grow rapidly.

Roundworms. Still other wormlike creatures called round-
worms are of importance to man. Some, as the vinegar eel found
in vinegar, or the pinworms parasitic in the
lower intestine, particularly of children, do little
or no harm. The pork worm or trichina, how
ever, is a parasite which may cause serious
injury. It passes through the first part of its
existence as a parasite in a pig or other verte
brate (cat, rat, or rabbit), where it lies, covered
within a tiny sac or cyst, in the muscles of its
hosts. If raw pork containing these worms is
eaten by man, the cyst is dissolved off by the
action of the digestive fluids, and the living
trichina becomes free in the intestine of man.
Here it reproduces and the young bore their way
through the intestine walls and enter the muscles,
causing inflammation there. This causes a pain
ful and often fatal disease known as trichinosis.

The Hookworm. The discovery by Dr. C.
W. Stiles of the Bureau of Animal Industry,
that the laziness and shiftlessness of the " poor whites " of the
South is partly due to a parasite called the hookworm, reads like
a fairy tale.

The people, largely farmers, become infected with a larval stage
of the hookworm, which develops in moist earth. It enters the
body usually through the skin of the feet, for children and adults
alike, in certain localities where the disease is common, go bare
foot to a considerable extent.

A complicated journey from the skin to the intestine now fol-

Trichinella spiralis
imbedded in
human muscle.
(After Leuckart.)

THE ECONOMIC IMPORTANCE OF ANIMALS 229

lows, the larvae passing through the veins to the heart, from there
to the lungs ; here they bore into the air passages and eventually
work their way by way of the windpipe into the intestine. One
result of the injury of the lungs is that many thus infected are
subject to tuberculosis. The adult worms, once in the food tube,
fasten themselves and feed upon the blood of their host by punc
turing the intestine wall. The loss of blood from this cause is
not sufficient to account for the bloodlessness of the person in
fected, but it has been discovered that the hookworm pours out a

A family suffering from hookworm.

poison into the wound which prevents the blood from clotting
rapidly (see page 315) ; hence a considerable loss of blood occurs
from the wound after the worm has finished its meal and gone to
another part of the intestine.

The cure of the disease is very easy ; thymol is given, which
weakens the hold of the worm, this being followed by
Epsom salts. For years a large area in the South undoubtedly
has been retarded in its development by this parasite ; hundreds of
millions of dollars and thousands of lives have been needlessly
sacrificed.

230 THE ECONOMIC IMPORTANCE OF ANIMALS

"The hookworm is not a bit spectacular: it doesn't get itself dis
cussed in legislative halls or furiously debated in political campaigns.
Modest and unassuming, it does not aspire to such dignity. It is satis
fied simply with (1) lowering the working efficiency and the pleasure of
living in something like two hundred thousand persons in Georgia and
all other Southern states in proportion; with (2) amassing a death rate
higher than tuberculosis, pneumonia, or typhoid fever; with (3) stub
bornly and quite effectually retarding the agricultural and industrial de
velopment of the section ; with (4) nullifying the benefit of thousands of
dollars spent upon education ; with (5) costing the South, in the course of
a few decades, several hundred millions of dollars. More serious and
closer at hand than the tariff; more costly, threatening, and tangible
than the Negro problem ; making the menace of the boll weevil laughable
in comparison it is preeminently the problem of the South." - Atlanta
Constitution.

Animals that prey upon Man. The toll of death from animals
which prey upon or harm man directly is relatively small. Snakes
in tropical countries kill many cattle and not a few people.

The bite of the rattlesnake of our own country, although dangerous,
seldom kills. The dreaded cobra of India has a record of over two hundred

and fifty thousand persons
killed in the last thirty-
five years. The Indian
government yearly pays
out large sums for the ex
termination of venomous
snakes, over two hundred
thousand of which have
been killed during a single
year.

Alligators and Croco
diles. These feed on

fishes, but often attack large animals, as horses, cows, and even man.
They seek their prey chiefly at night, and spend the day basking in the
sun. The crocodiles of the Ganges River in India levy a yearly tribute
of many hundred lives from the natives.

Carnivorous animals such as lions and tigers still inflict damage
in certain parts of the world, but as the tide of civilization ad-

A flesh-eating reptile, the alligator.

THE ECONOMIC IMPORTANCE OF ANIMALS 231

vances, their numbers are slowly but surely decreasing so that as
important factors in man's welfare they may be considered almost
negligible.

REFERENCE BOOKS
ELEMENTARY

Hunter, Laboratory Problems in Civic Biology. American Book Company.

Beebe, The Bird. Henry Holt and Company.

Bigelow, Applied Biology. Macmillan and Company

Davison, Practical Zoology. American Book Company.

Herrick, Household Insects and Methods of Control. Cornell Reading Courses.

Hornaday, Our Vanishing Wild Life. New York Zoological Society.

Hodge, Nature Study and Life. Ginn and Company.

Kipling, Captains Courageous. Charles Scribner's Sons.

Sharpe, Laboratory Manual, pp. 157-158, 182-203, 320-341. American Book

Company.

Stone and Cram, American Animals. Doubleday, Page and Company.
Toothaker, Commercial Raw Materials. Ginn and Company.

ADVANCED

Flower, The Horse. D. Appleton and Company.

Hornaday, The American Natural History. Macmillan and Company.

Jordan, Fishes. Henry Holt and Company.

Jordan and Evermann, American Food and Game Fishes. Doubleday, Page and

Company.
Schaler, Domesticated Animals, their Relations to Man and to His Advancement in

Civilization. Charles Scribner's Sons.

XVI. THE FISH AND FROG, AN INTRODUCTORY
STUDY OF VERTEBRATES

Problems. To determine how a fish and a frog are fitted
for the life they lead.

To determine some methods of development in vertebrate
animals.

(a) Fishes.

(6) Frogs. .

LABORATORY SUGGESTIONS

Laboratory exercise. Study of a living fish adaptations for pro
tection, locomotion, food getting, etc.

Laboratory demonstration. The development of the fish or frog egg.

Visit to the aquarium. Study of adaptations, economic uses of fishes,
artificial propagation of fishes.

Two Methods of Breathing in Vertebrates. Vertebrate
animals have at least two methods of getting their oxygen. In
other respects their life processes are nearly similar. Of all
vertebrates fishes are the only ones fitted to breathe all their lives
under water. Other vertebrates are provided with lungs and
take their oxygen directly from the air. 1 We will next take up
the study of a fish to see how it is fitted for its life in the water.

STUDY OF A FISH

The Body. One of our common fresh-water fish is the bream,
or golden shiner. The body of the bream runs insensibly into the
head, the neck being absent. The long, narrow body with its
smooth surface fits the fish admirably for its life in the water.
Certain cells in the skin secrete mucus or slime, another adapta-

1 With the exception of a few lungless salamanders. Most salamanders get much
of their supply of oxygen through their moist skins.

232

THE FISH 233

tion. The position of the scales, overlapping in a backward di
rection, is yet another adaptation which aids in passing through
the water. Its color, olive above and bright silver and gold below,
is protective. Can you see how?

The bream. A, dorsal fin ; B, caudal fin ; C, anal fin ; D, pelvic fin ;
E, pectoral fin.

The Appendages and their Uses. The appendages of the fish
consist of paired and unpaired fins. The paired fins are four in
number, and are believed to correspond in position and structure
with the paired limbs of a man. Note the illustration above
and locate the paired pectoral and pelvic fins. (These are so called
because they are attached to the bones forming the pectoral and
pelvic girdles. (See page 268.) Find, by comparison with the
Figure, the dorsal, anal, and caudal fins. How many unpaired
fins are there?

The flattened, muscular body of the fish, tapering toward the
caudal fin, is moved from side to side with an undulating motion
which results in the forward movement of the fish. This move
ment is almost identical with that of an oar in sculling a boat.
Turning movements are brought about by use of the lateral fins
in much the same way as a boat is turned. We notice the dorsal
and other single fins are evidently useful in balancing and steer
ing.

The Senses. The position of the eyes at the side of the head
is an evident advantage to the fish. Why? The eye is globular

234 A STUDY OF VERTEBRATES

in shape. Such an eye has been found to be very nearsighted.
Thus it is unlikely that a fish is able to perceive objects at any
great distance from it. The eyes are unprotected by eyelids, but
the tough outer covering and their position afford some protection.

Feeding experiments with fishes show that a fish becomes aware
of the presence of food by smelling it as well as by seeing it. The
nostrils of a fish can be proved to end in little pits, one under each
nostril hole. Thus they differ from our own, which are connected
with the mouth cavity. In the catfish, for example, the barbels,
or horns, receive sensations of smell and taste. They do not
perceive odors as we do for a fish perceives only substances that
are dissolved in the water in which it lives. The senses of taste
and touch appear to be less developed than the other senses,

Along each side of most fishes is a line of tiny pits, provided with
sense organs and connected with the central nervous system of the
fish. This area, called the lateral line, is believed to be sensitive
to mechanical stimuli of certain sorts. The " ear " of the fish is
under the skin and serves partly as a balancing organ.

Food Getting. A fish must go after its food and seize it, but
has no structures for grasping except the teeth. Consequently
we find the teeth small, sharp, and numerous, well adapted for
holding living prey. The tongue in most fishes is wanting or
very slightly developed.

Breathing. A fish, when swimming quietly or when at rest,
seems to be biting when no food is present. A reason for this act
is to be seen when we introduce a little finely powdered carmine
into the water near the head of the fish. It will be found that a
current of water enters the mouth at each of these biting move
ments and passes out through two slits found on each side of the
head of the fish. Investigation shows us that under the broad, flat
plate, or operculum, forming each side of the head, lie several long,
feathery, red structures, the gills.

Gills. If we examine the gills of any large fish, we find that a
single gill is held in place by a bony arch, made of several pieces
of bone which are hinged in such a way as to give great flexibility
to the gill arch, as the support is called. Covering the bony
framework, and extending from it, are numerous delicate filaments

THE FISH

235

Diagram of the gills of a fish. (H), the
heart which forces the blood into the
tubes (V), which run out into the gill
filaments. A gill bar (<?) supports
each gill. The blood after exchang
ing its carbon dioxide for oxygen is
sent out to the cells of the body
through the artery (A).

covered with a very thin membrane or skin. Into each of these
filaments pass two blood vessels ; in one blood flows downward and
in the other upward. Blood
reaches the gills and is carried
away from these organs by
means of two large vessels which
pass along the bony arch pre
viously mentioned. In the gill
filament the blood comes into
contact with the free oxygen of
the water bathing the gills. An
exchange of gases through the
walls of the gill filaments results
in the loss of carbon dioxide
and a gain of oxygen by the
blood. The blood carries oxy
gen to the cells of the body
and (as work is done by the
cells as a result of the oxidation of food) brings carbon dioxide
back to the gills.

Gill Rakers. If we open wide the mouth of any large fish and
look inward, we find that the mouth cavity leads to a funnel-like
opening, the gullet. On each side of the gullet we can see the gill
arches, guarded on the inner side by a series of sharp-pointed struc
tures, the gill rakers. In some fishes in which the teeth are not
well developed, there seems to be a greater development of the
gill rakers, which in this case are used to strain out small organisms
from the water which passes over the gills. Many fishes make
such use of the gill rakers. Such are the shad and menhaden,
which feed almost entirely on plankton, a name given to the
small plants and animals found by millions in the water.

Digestive System. The gullet leads directly into a baglike stomach.
There are no salivary glands in the fishes. There is, however, a large
liver, which appears to be used as a digestive gland. This organ, because
of the oil it contains, is in some fishes, as the cod, of considerable economic
importance. Many fishes have outgrowths like a series of pockets from
the intestine. These structures, called the pyloric cceca, are believed to

236 A STUDY OF VERTEBRATES

secrete a digestive fluid. The intestine ends at the vent, which is usually
located on the under side of the fish, immediately in front of the anal fin.
Swim Bladder. An organ of unusual significance, called the swim
bladder, occupies the region just dorsal to the food tube. In young fishes
of many species this is connected by a tube with the anterior end of the
digestive tract. In some forms this tube persists throughout life, but in
other fishes it becomes closed, a thin, fibrous cord taking its place. The
swim bladder aids in giving the fish nearly the same weight as the water

A fish opened to show H, the heart ; G, the gills ; L, the liver ; S, the stomach ;
I, the intestine ; O, the ovary ; K , the kidney, and B, the air bladder.

it displaces, thus buoying it up. The walls of the organ are richly sup
plied with blood vessels, and it thus undoubtedly serves as an organ for
supplying oxygen to the blood when all other sources fail. In some
fishes (the dipnoi, page 187) it has come to be used as a lung.

Circulation of the Blood. In the vertebrate animals the blood is
said to circulate in the body, because it passes through a more or less closed
system of tubes in its course around the body. In the fishes the heart is
a two-chambered muscular organ, a thin-walled auricle, the receiving
chamber, leading into a thick-walled muscular ventricle from which the
blood is forced out. The blood is pumped from the heart to the gills;
there it loses some of its carbon dioxide ; it then passes on to other parts
of the body, eventually breaking up into very tiny tubes called capillaries.
From the capillaries the blood returns, in tubes of gradually increasing
diameter, toward the heart again. The body cells lie between the smallest
branches of the capillaries. Thus they get from the blood food and oxy
gen and return to the blood the wastes resulting from oxidation within
the cell body. During its course some of the blood passes through the
kidneys and is there relieved of part of its nitrogenous waste. Circulation

THE FISH 237

of blood in the body of the fish is rather slow. The temperature of the
blood being nearly that of the surrounding media in which the fish lives,
the animal has incorrectly been given the term " cold-blooded."

Nervous System. As in all other vertebrate animals, the brain and
spinal cord of the fish are partially inclosed in bone. The central nervous
system consists of a brain, with nerves connecting the organs of sight,
taste, smell, and hearing, and such parts of the body as possess the sense of
touch ; a spinal cord ; and spinal nerves. Nerve cells located near the out
side of the body send in messages to the central system, which are there
received as sensations. Cells of the central nervous system, in turn, send
out messages which result in the movement of muscles.

Skeleton. In the vertebrates, of which the bony fish is an example,
the skeleton is under the skin, and is hence called an endoskeleton. It
consists of a bony framework, the vertebral column which protects the
spinal cord and certain attached bones, the ribs, with other spiny bones to
which the unpaired fins are attached. The paired fins are attached to the
spinal column by two collections of bones, known respectively as the
pectoral and pelvic girdles. The bones in the main skeleton serve in the
fish for the attachment of powerful muscles, by means of which locomo
tion is accomplished. In most fishes, the exoskeleton, too, is well developed,
consisting usually of scales, but sometimes of bony plates.

Food of Fishes. We have already seen that in a balanced
aquarium the balance of food was preserved by the plants, which
furnished food for the tiny animals or were eaten by larger ones,
for example, snails or fish. The smaller animals in turn became
food of larger ones. The nitrogen balance was maintained through
the excretions of the animals and their death and decay.

The marine world is a great balanced aquarium. The upper
layer of water is crowded with all kinds of little organisms, both
plant and animal. Some of these are microscopic in size ; others,
as the tiny crustaceans, are visible to the eye. On these little
organisms some fish feed entirely, others in part. Such are the
menhaden l (bony, bunker, mossbunker of our coast), the shad,
and others. Other fishes are bottom feeders, as the blackfish and

1 It has been discovered by Professor Mead of Brown University that the in
crease in starfish along certain parts of the New England coast was in part due
to overfishing of menhaden, which at certain times in the year feed almost entirely
on the young starfish.

238

A STUDY OF VERTEBRATES

the sea bass, living almost entirely upon mollusks and crusta
ceans. Still others are hunters, feeding upon smaller species of
fish, or even upon their weaker brothers. Such are the bluefish,
squeteague or weakfish, and others.

What is true of salt-water fish is equally true of those inhabiting
our fresh- water streams and lakes. It is one of the greatest prob
lems of our Bureau of Fisheries to discover this relation of various
fishes to their food supplies so as to aid in the conservation and
balance of life in our lakes, rivers, and seas.

Migration of Fishes. Some fishes change their habitat at dif
ferent times during the year, moving in vast schools northward
in summer and southward in the winter. In a general way such
migrations follow the coast lines. Examples of such migratory
fish are the cod, menhaden, herring, and bluefish. The migra
tions are due to temperature changes, to the seeking after food,
and to the spawning instinct. Some fish migrate to shallower
water in the summer and to deeper water in the winter ; here the

reason for the migra
tion is doubtless the
change in temperature.
The Egg-laying
Habits of the Bony
Fishes. The eggs of
most bony fishes are
laid in great numbers,
varying from a few
thousand in the trout
to many hundreds of
thousands in the shad
and several millions in
the cod. The time of
egg-laying is usually
spring or early sum
mer. At the time of
spawning the male

usually deposits milt, consisting of millions of sperm cells, in the
water just over the eggs, thus accomplishing fertilization. Some

Development of a trout. 1, the embryo within the
egg ; 2, the young fish just hatched with the yoke
sac still attached ; 3, the young fish.

THE FISH 239

fishes, as sticklebacks, sunfish, toadfish, etc., make nests, but
usually the eggs are left to develop by themselves, sometimes
attached to some submerged object, but more frequently free in
the water. In some eggs a tiny oil drop buoys up the egg to the
surface, where the heat of the sun aids development. They are
exposed to many dangers, and both eggs and developing fish are
eaten, not only by birds, fish of other species, and other water in
habitants, but also by their own relatives, and even parents.
Consequently a very small percentage of eggs ever produce ma
ture fish.

The Relation of the Spawning Habits to Economic Importance
of Fish. The spawning habits of fish are of great importance to
us because of the economic value of fish to mankind, not only
directly as a food, but indirectly as food for other animals in turn
valuable to man. Many of our most desirable food fishes, notably
the salmon, shad, sturgeon, and smelt, pass up rivers from the
ocean to deposit their eggs, swimming against strong currents
much of the way, some species leaping rapids and falls, in order
to deposit their eggs in localities where the conditions of water
and food are suitable, and the water shallow enough to allow
the sun's rays to warm it sufficiently to cause the eggs to develop.
The Chinook salmon of the Pacific coast, the salmon used in the
Western canning industry, travels over a thousand miles up the
Columbia and other rivers, where it spawns. The salmon begin
to pass up the rivers in early spring, and reach the spawning beds,
shallow deposits of gravel in cool mountain streams, before late
summer. Here the fish, both males and females, remain until
the temperature of the water falls to about 54 Fahrenheit. The
eggs and milt are then deposited, and the old fish die, leaving the
eggs to be hatched out later by the heat of the sun's rays.

Need of Conservation. The instinct of this and other species
of fish to go into shallow rivers to deposit their eggs has been
made use of by man. At the time of the spawning migration the
salmon are taken in vast numbers, for the salmon fisheries net
over $16,000,000 annually.

But the need for conservation of this important national asset
is great. The shad have within recent time abandoned their

240

A STUDY OF VERTEBRATES

breeding places in the Connecticut River, and the salmon have been
exterminated along our eastern coast within the past few decades.
It is only a matter of a few years when the Western salmon will
be extinct if fishing is continued at the present rate. More fish
must be allowed to reach their breeding places. To do this a
closed season on the rivers of two or three days out of each seven
while the shad or the salmon run would do much good.

The sturgeon, the eggs of which are used in the manufacture of
the delicacy known as caviar, is an example of a fish that is almost
extinct in this part of the world. Other food fish taken at the
breeding season are also in danger.

Artificial Propagation of Fishes. Fortunately, the govern
ment through the Bureau of Fisheries, and various states by wise
protective laws and by artificial propagation of fishes, are be
ginning to turn the tide. Certain days of the week the salmon
are allowed to pass up the Columbia unmolested. Closed breed
ing seasons protect our trout, bass, and other game fish, also the

catching of fish under
a certain size is pro
hibited.

Many fish hatcheries,
both government and
state, are engaged in
artificially fertilizing
millions of fish eggs of
various species and pro
tecting the young fry
until they are of such
size that they can take

care of themselves, when they are placed in ponds or streams.
This artificial fertilization is usually accomplished by first squeezing
out the ripe eggs from a female into a pan of water ; in a similar
manner the milt or sperm cells are obtained, and poured over the
eggs. The eggs are thus fertilized. They are then placed in re
ceptacles supplied with running water and left to develop under
favorable conditions. Shortly after the egg has segmented (divided
into many cells) the embryo may be seen developing on one side

-=- \M\\v\\\'

Artificial fertilization of fish eggs.

THE FROG 241

of the egg. The rest of the egg is made up of food or yolk,
and when the baby fish hatches it has for some time the yolk
attached to its ventral surface. Eventually the food is absorbed
into the body of the fish. The development of the fish is direct,
the young fish becoming an adult without any great change in
form. The young fry are kept under ideal conditions until later,
when they are shipped, sometimes thousands of miles, to their
new homes.

Early development of salmon. Natural size.

NOTE TO TEACHER. It is suggested that in the spring term the frog be studied,
but if animal biology be taken up during the fall term the fish only might be used.

THE FROG

Adaptations for Life. The most common frog in the eastern
part of the United States is the leopard frog. It is recognized by
its greenish brown body with dark spots, each spot being outlined
in a lighter-colored background. In spite of the apparent lack of
harmony with their surroundings, their color appears to give
almost perfect protection. In some species of frogs the color of
the skin changes with the surroundings of the frog, another means
of protection.

Adaptations for life in the water are numerous. The ovoid
body, the head merging into the trunk, the slimy covering (for
the frog is provided, like the fish, with mucus cells in the skin),
and the powerful legs with webbed feet, are all evidences of the
life which the frog leads.

Locomotion. You will notice that the appendages have the
same general position on the body and same number of parts as
do your own (upper arm, forearm, and hand ; thigh, shank, and
foot, the latter much longer relatively than your own). Note that
while the hand has four fingers, the foot has five toes, the latter
connected by a web. In swimming the frog uses the stroke we

HUNTER, CIV. BI. 16

242

A STUDY OF VERTEBRATES

all aim to make when we are learning to swim. Most of the energy
is liberated from the powerful backward push of the hind legs,
which in a resting position are held doubled up close to the body.
On land, locomotion may be by hopping or crawling.

Sense Organs. The frog is well provided with sense organs.
The eyes are large, globular, and placed at the side of the head.
When they are closed, a delicate fold, or third eyelid, called the
nictitating membrane, is drawn over each eye. Frogs probably
see best moving objects at a few feet from them. Their vision is
much keener than that of the fish. The external ear (tympanum)
is located just behind the eye on the side of the body. Frogs hear
sounds and distinguish various calls of their own kind, as is proved
by the fact that frogs recognize the warning notes of their mates
when any one is approaching. The inner ear
also has to do with balancing the body as it .has
in fishes and other vertebrates. Taste and smell
are probably not strong sensations in a frog or
toad. They bite at moving objects of almost
any kind when hungry. The long flexible
tongue, which is fastened at the front, is used to
catch insects. Experience has taught these
animals that moving things, insects, worms, and
the like, make good food. These they swallow
whole, the tiny teeth being used to hold the
food. Touch is a well-developed sense. They
also respond to changes in temperature under
water, remaining there in a dormant state for
the winter when the temperature of the air

1ms diagram snows

how the frog uses becomes colder than that of the water.

Breathing. The frog breathes by raising
and lowering the floor of the mouth, pulling
in air through the two nostril holes. Then the little flaps over
the holes are closed, and the frog swallows this air, forcing it
down into the baglike lungs. The skin is provided with many
tiny blood vessels, and in winter, while the frogs are dormant
at the bottom of the ponds, it serves as the only organ of respi
ration.

its tongue to catch
insects.

THE FROG

243

The Food Tube and its Glands. The mouth leads like a funnel
into a short tube, the gullet. On the lower floor of the mouth can
be seen the slitlike glottis leading to the lungs. The gullet widens
almost at once into a long stomach, which in turn leads into a much
coiled intestine. This widens abruptly at the lower end to form
the large intestine. The latter leads into the cloaca (Latin,
sewer), into which open the kidneys, urinary bladder, and repro
ductive organs (ovaries or spermaries). Several glands, the func
tion of which is to produce digestive fluids, open into the food
tube. These digestive fluids, by means of the ferments or enzymes
contained in them, change insoluble food
materials into a soluble form. This allows
of the absorption of food material through
the walls of the food tube into the blood.
The glands (having the same names and
uses as those in man) are the sali
vary glands, which pour their juices
into the mouth, the gastric glands
in the walls of the stom
ach, and the liver and
pancreas, which open
into the intestine.

Circulation. The frog
has a well-developed heart,
composed of a thick-walled
muscular ventricle and two
thin-walled auricles. The
heart pumps the blood
through a system of closed
tubes to all parts of the
body. Blood enters the
right auricle from all parts
of the body ; it then con
tains considerable carbon
dioxide ; the blood enter
ing the left auricle comes

from the lungs, hence it contains a considerable amount of oxygen. Blood
leaves jfche heart through the ventricle, which thus pumps some blood

Internal organs of a frog: M, mouth; T, tongue; Lu,
lungs; H, heart; St, stomach; I, small intes
tine; L, liver; G. gall bladder; P, pancreas; C,
cloaca; B, urinary bladder; S, spleen; K, kidney,
Od, oviduct; O, ovary; Br, brain; Sc. spinal
cord; Ba, back bone.

244 A STUDY OF VERTEBRATES

containing much and some containing little oxygen. Before the blood
from the tissues and lungs has time to mix, however, it leaves the ventricle
and by a delicate adjustment in the vessels leaving the heart most of the
blood containing much oxygen is passed to all the various organs of the
body, while the blood deficient in oxygen, but containing a large amount
of carbon dioxide, is pumped to the lungs, where an exchange of oxygen
and carbon dioxide takes place by osmosis.

In the tissues of the body wherever work is done the process of burning
or oxidation must take place, for by such means only is the energy neces
sary to do the work released. Food in the blood is taken to the muscle
cells or other cells of the body and there oxidized. The products of the
burning carbon dioxide and any other organic wastes given off from
the tissues must be eliminated from the body. As we know, the carbon
dioxide passes off through the lungs and to some extent through the skin
of the frog, while the nitrogenous wastes, poisons which must be taken
from the blood, are eliminated from it in the kidneys.

Change of Form in Development of the Frog. Not all verte
brates develop directly into an adult. The frog, for example,
changes its form completely before it becomes an adult. This
change in form is known as a metamorphosis. Let us examine
the development of the common leopard frog.

The eggs of this frog are laid in shallow water in the early
spring. Masses of several hundred, which may be found at
tached to twigs or other supports under water, are deposited at
a single laying. Immediately before leaving the body of the
female they receive a coating of jellylike material, which swells
up after the eggs are laid. Thus they are protected from the
attack of fish or other animals which might use them as food.
The upper side of the egg is dark, the light-colored side being
weighted down with a supply of yolk (food). The fertilized egg
soon segments (divides into many cells), and in a few days, if the
weather is warm, these eggs have each grown into an oblong body
which shows the form of a tadpole. Shortly after the tadpole
wriggles out of the jellylike case and begins life outside the egg. At
first it remains attached to some water weed by means of a pair
of suckerlike projections ; later a mouth is formed, and the tad
pole begins to feed upon algae or other tiny water plants. At
this time, about two weeks after the eggs were laid, gills are

(

Development of a frog. 1, two cell stage ; 2, four cell stage ; 3, 8 cells are formed,
notice the upper cells ars smaller ; in (4) the lower cells are seen to be much
larger because of the yolk ; 5, the egg has continued to divide and has formed
a gastrula ; 6, 7, the body is lengthening, head is seen at the right hand end ;
8, the young tadpole with external gills ; 9, 10, the gills are internal, hind legs
beginning to form; 11, the hind legs show plainly; 12, 13, 14, later stages in
development; 15, the adult frog. Figures 1, 2, 3, 4, 5, 6, and 7 are very
much enlarged. (Drawn after Leukart and Kny by Frank M. Wheat.)

245

246

A STUDY OF VERTEBRATES

present on the outside of the body. Soon after, the external gills
are replaced by gills which grow out under a fold of the skin which
forms an operculum somewhat as in the fish. Water reaches the
gills through the mouth and passes out through a hole on the left
side of the body. As the tadpole grows larger, legs appear, the
hind legs first, although for a time locomotion is performed by
means of the tail. In the leopard frog the change from the egg
to adult is completed in one summer. In late July or early August,
the tadpole begins to eat less, the tail becomes smaller (being
absorbed into other parts of the body), and before long the trans
formation from the tadpole to the young frog is complete. In
the green frog and bullfrog the metamorphosis is not completed
until the beginning of the second summer. The large tadpoles
of such forms bury themselves in the soft mud of the pond bottom
during the winter.

Shortly after the legs appear, the gills begin to be absorbed, and
lungs take their place. At this time the young animal may be
seen coming to the surface of the water for air. Changes in the
diet of the animal also occur ; the long, coiled intestine is trans
formed into a much shorter one. The animal, now insectivorous
in its diet, becomes provided with tiny teeth and a mobile tongue,

instead of keeping the
horny jaws used in
scraping off algse. After
the tail has been com
pletely absorbed and
the legs have become
full grown, there is
no further structural
change, and the meta
morphosis is complete.
Development of
Birds. The white of
the hen's egg is put on

At the left is a hen's egg, opened to show the embryo during the passage of
at the center (the spot surrounded by a lighter th j (which IS

area). At the right is an English sparrow one .

day after hatching. in the yoke or yellow

THE BIRD

247

portion) to the outside of the body. Before the egg is laid a shell
is secreted over its surface. If the fertilized egg of a hen be
broken and carefully examined, on the surface of the yolk will be
found a little circular disk. This is the beginning of the growth of
an embryo chick. If a series of eggs taken from an incubator
at periods of twenty-four hours or less apart were examined, this
spot would be found at first to increase in size ; later the little
embryo would be found tying on the surface. Still later small
blood vessels could be made out reaching into the yolk for food,
the tiny heart beating as early as the second day of incubation.
After about three weeks of incubation the little chick hatches;
that is, breaks the shell, and emerges in almost the same form as
the adult.

Development of a Mammal. In mammals after fertilization
the egg undergoes development within the body of the mother.
Instead of blood vessels
connecting the embryo with
the yolk as in the chick,
here the blood vessels are
attached to an absorbing
organ, known as the pla
centa. This structure sends
branch like processes into
the w r all of the uterus (the
organ which holds the em
bryo) and absorbs nour
ishment and oxygen by
osmosis from the blood
of the mother. After a
length of time which varies

in different Species of mam- The embryo (e) of a mammal, showing the ab-
(from about three sorbing organ in black, the branch-like pro-

-ct

. . . cesses which absorb blood from the mother

weeks in a guinea pig to being shown at 0) ; ct, the tube connecting

twenty-two months in an the embr y with the absorbing organ or

^ . placenta.

elephant), the young ani

mal is expelled by muscular contraction of the uterus, or is born.

The young, usually, are born in a helpless condition, then nour-

248 A STUDY OF VERTEBRATES

ished by milk furnished by the mother until they are able to take
other food. Thus we see as we go higher in the scale of life fewer
eggs formed, but those few eggs are more carefully protected and
cared for by the parents. The chances of their growth into adults
are much greater than in the cases when many eggs are produced.

REFERENCE BOOKS

ELEMENTARY

Hunter, Laboratory Problems in Civic Biology. American Book Company.

Bigelow, Introduction to Biology. The Macmillan Company.

Cornell Nature Study Leaflets. Bulletins XVI, XVII.

Davison, Practical Zoology, pages 185-199. American Book Company.

Hodge, Nature Study and Life, Chaps. XVI, XVII. Ginn and Company.

Sharpe, Laboratory Manual, pp. 195, 204-209. American Book Company.

ADVANCED

Dickerson, The Frog Book. Doubleday, Page and Company.
Holmes, The Biology of the Frog. The Macmillan Company.
Jordan, Fishes. Henry Holt and Company.

Morgan, The Development of the Frog's Egg. The Macmillan Company.
Needham, General Biology. Comstock Publishing Company.

XVII. HEREDITY, VARIATION, PLANT AND ANIMAL

BREEDING

Problems. To determine what makes the offspring of ani
mals or plants tend to be like their parents.

To determine what makes the offspring of animals and
plants differ from their parents.

To learn about some methods of plant and animal breeding.

(a) By selection.

(b) By hybridizing.

To learn about some methods of improving the human race.
(a) By eugenics.
(b} By euthenics.

SUGGESTIONS FOR LABORATORY WORK

Laboratory exercise. On variation and heredity among members of a
class in the schoolroom.

Laboratory exercise. On construction of curve of variation in measure
ments from given plants or animals.

Laboratory demonstration. Stained egg cells (ascaris] to show chromo
somes.

Laboratory demonstrations. To illustrate the part played in plant or
animal breeding by

(a) selection.

(&) hybridizing.

Laboratory demonstration. From charts to illustrate how human char
acteristics may be inherited.

HEREDITY AND EUGENICS

Heredity and what it Means. As I look over the faces of the
boys in my class I notice that each boy seems to be more or less
like each other boy in the class ; he has a head, body, arms, and
legs, and even in minor ways he resembles each of the other boys
in the room. Moreover, if I should ask him I have no doubt

249

250

HEREDITY AND VARIATION

but that he would tell me that he resembled in many respects his
mother or father. Likewise if I should ask his parents whom he
resembled, they would say, " I can see his grandmother or his
grandfather in him."

This wonderful force which causes the likeness of the child to
its parents and to their parents we call heredity. Heredit}^ causes
the plants as well as animals to be like their parents. If we
trace the workings of heredity in our own individual case, we will
probably find that we are molded like our ancestors not only in
physical characteristics but in mental qualities as well. The
ability to play the piano or to paint is probably as much a case of
inheritance as the color of our eyes or the shape of our nose. We
are a complex of physical and mental characters, received in part
from all our ancestors.

Variation. But I notice another thing ; no boy in the class
before me is exactly like any other boy, even twins having minute
differences. In this wonderful mold of nature each one of us

Variations in the Catalpa caterpillar. (Photographed, natural size,
by Davison.)

HEREDITY AND VARIATION 251

tends to be slightly different from his or her parents. Each plant,
each animal, varies to a greater or lesser degree from its immediate
ancestors and may vary to a very great degree. This factor in
the lives of plants and animals is called variation. Heredity and
variation are the cornerstones on which all the work in the improve
ment of plants and animals, including man himself, are built.

The Bearers of Heredity. We have seen that somewhere in
every living cell is a structure known as a nucleus. In this nucleus,
which is a part of the living matter of the cell, are certain very
minute structures always present, known as chromosomes. These
chromosomes (so called because they take up color when stained)
are believed to be the structures which contain the determiners
of the qualities which may be passed from parent plant to offspring
or from animal to animal ; in other words, the qualities that are
inheritable (see page 252).

The Germ Cells. But it has been found that certain cells of
the body, the egg and the sperm cells, before uniting contain only
half as many chromosomes as do the body cells. In preparing
for the process of fertilization, half of these elements have been
eliminated, so that when the egg and sperm cell are united they
will have the full number of chromosomes that the other cells
have.

If the chromosomes carry the determiners of the characters
which are inheritable, then it is easy to see that a fertilized egg must
contain an equal number of chromosomes from the bodies of each
parent. Consequently characteristics from each parent are
handed down to the new individual. This seems to be the way in
which nature succeeds in obtaining variation, by providing cell
material from two different individuals.

Offspring are Part of their Ancestors. We can see that if
you or I receive characteristics from our parents and they received
characteristics from their parents, then we too must have some of
the characteristics of the grandparents, and it is a matter of com
mon knowledge that each of us does have some trait or lineament
which can be traced back to our grandfather or grandmother.
Indeed, as far back as we are able to go, ancestors have added
something.

252

HEREDITY AND VARIATION

COMPARISON

SEXUAL AND ASEXUAL
CELL "REPRODUCTION

HEREDITY AND VARIATION

253

Charles Darwin and Natural Selection. The great English
man Charles Darwin was one of the first scientists to realize how
this great force of heredity applied to the development or evolu
tion of plants and animals. He knew that although animal 3
and plants were like their ancestors, they also tended to vary.
In nature, the variations which best fitted a plant or animal for
life in its own environment were the ones which were handed
down because those having variations which were not fitted for
life in that particular environment would die. Thus nature
seized upon favorable variations and after a time, as the descend
ants of each of these individuals also tended to vary, a new species
of plant or animal, fitted for the place it had to live in, would be
gradually evolved.

Mutations. Recently a new method of variation has been
discovered by a Dutch naturalist, named Hugo de Vries. He
found that new species of plants and animals arise suddenly by
" mutations " or steps. This means that new species instead of
arising from very slight variations, continuing during long periods
of years (as Darwin believed), might arise very suddenly as a very
great variation which would at once breed true. It is easily seen
that such a condition would be of immense value to breeders, as
new plants or animals quite unlike their parents might thus be
formed and perpetuated. It will be one of the future problems
of plant and animal breeders to isolate and breed " mutants,"
as such organisms are
called.

Artificial Selection.
Darwin reasoned that
if nature seized upon
favorable variants, then
man, by selecting the
variations he wanted,
could form new varie
ties of plants or ani
mals much more quickly

than nature. And SO Improvement in corn by selection. To the left, the

corn improved by selection from the original

to-day plant or animal type at the right.

254 HEREDITY AND VARIATION

breeders select the forms having the characters they wish to per
petuate and breed them together. This method used by plant
and animal breeders is known as selection.

Selective Planting. By selective planting we mean choosing
the best plants and planting the seed from these plants with a view of
improving the yield. In doing this we must not necessarily select
the most perfect fruits or grains, but must select seeds from the
best plants. A wheat plant should be selected not from its yield
alone, but from its ability to stand disease and other unfavorable
conditions. In 1862 a Mr. Fultz, of Pennsylvania, found three
heads of beardless or bald wheat while passing through a large
field of bearded wheat. These were probably mutants which had
lost the chaff surrounding the kernel. Mr. Fultz picked them out,
sowed them by themselves, and produced a quantity of wheat now
known favorably all over the world as the Fultz wheat. In select
ing wheat, for example, we might breed for a number of different
characters, such as more starch, or more protein in the grain, a
larger yield per acre, ability to stand cold or drought or to resist
plant disease. Each of these characters would have to be sought
for separately and could only be obtained after long and careful
breeding. The work of Mendel (see page 257) when applied to
plant breeding will greatly shorten the time required to produce
better plants of a given kind. By careful seed selection, some
Western farmers have increased their wheat production by 25
per cent. This, if kept up all over the United States, would mean
over $100,000,000 a year in the pockets of the farmers.

Hybridizing. We have already seen that pollen from one
flower may be carried to another of the same species, thus produc
ing seeds. If pollen from one plant be placed on the pistil of an
other of an allied species or variety, fertilization may take place
and new plants be eventually produced from the seeds. This
process is known as hybridizing, and the plants produced by this
process known as hybrids.

Hybrids are extremely variable, rarely breed from seeds, and often
are apparently quite unlike either parent plant. They must be
grown for several years, and all plants that do not resemble the
desired variety must be killed off, if we expect to produce a hybrid

HEREDITY AND VARIATION

255

that will breed more plants like itself. Luther Burbank, the
great hybridizer of California, destroys tens of thousands of plants
in order to get one or two with the charac
ters which he wishes to preserve. Thus he
is yearly adding to the wealth of this
country by producing new plants or fruits
of commercial value. A number of years
ago he succeeded in growing a new va
riety of potato, which has already en
riched the farmers of this country about
$20,000,000. One of his varieties of black
walnut trees, a very valuable hard wood,
grows ten to twelve times as rapidly as
ordinary black walnuts. With lumber
yearly increasing in price, a quick grow
ing tree becomes a very valuable com
mercial product. Among his famous
hybrids are the plumcot, a cross between
an apricot and a plum, his numerous va
rieties of berries and his splendid " Climax "
plum, the result of a cross between a
bitter Chinese plum and an edible Jap
anese plum. But none of Burbank's
products grow from seeds ; they are all produced asexually, from
hybrids by some of the processes described in the next paragraph.

The Department of Agriculture and its Methods. The Depart
ment of Agriculture is also doing splendid work in producing new
varieties of oranges and lemons, of grain and various garden vege
tables. The greatest possibilities have been shown by department
workers to be open to the farmer or fruit grower through hybrid
izing, and by budding, grafting, or slipping.

Budding. If a given tree, for example, produces a kind of fruit
which is of excellent quality, it is possible sometimes to attach parts
of the tree to another strong tree of the same species that may not
bear good fruit. This is done by budding. A T-shaped incision
is cut in the bark ; a bud from the tree bearing the desired fruit is
placed in the cut and bound in place. When a shoot from the

In hybridizing, all of the
flower is removed at the
line (W) except the pis
til (P). Then pollen
from another flower of a
nearly related kind is
placed on the pistil and
the pollinated flower
covered up with a paper
bag. Can you explain
why ?

256

HEREDITY AND VARIATION

embedded bud grows out the following spring, it is found to have
all the characters of the tree from which it was taken.

Steps in budding, a, twig having suitable buds to use; b, method of cutting
out bud ; c, how the bark is cut ; d, how the bark is opened ; e, inserting
the bud ; /, the bud in place; g, the bud properly bound in place.

Grafting. Of much the same nature is grafting. Here, how
ever, a small portion of the stem of the closely allied tree is fas

tened into the trunk of the growing tree
in such a manner that the two cut layers
just under the bark will coincide. This
will allow of the passage of food into
the grafted part and insure the ultimate
growth of the twig. Grafting and bud
ding are of considerable economic value
to the fruit grower, as it enables him
Steps in tongue grafting, a, the to produce at will, trees bearing choice

two branches to be formed ; ... ,. ,. . , ,

b, a tongue cut in each ; c, fit- Varieties of fruit. 1

Other Methods. Other methods of
plant propagation are by means of run
ners, as when strawberry plants strike root from long stems that
run along the ground ; layering, where roots may develop on
covered up branches of blackberry or raspberry plants ; slips, roots
developing from stems which are cut off and placed in moist
sand ; from tubers, as in planting potatoes ; and by means of

1 For full directions for budding and grafting, see Goff and Mayne, First Princi
ples of Agriculture, Chap. XIX, Mayne and Hatch, High School Agriculture,
pp. 159-165, or Hodge, Nature Study and Life, pages 169-179.

ted together; d, method of

HEREDITY AND VARIATION

257

bulbs, as the tulip or hyacinth. All of the above means of prop
agation are asexual and are of importance in our problem of
plant breeding.

Plant breeding plots. (Minnesota Experiment Station.)

The Work of Gregor Mendel. Fifty years ago, an Austrian
monk, Gregor Mendel, found in breeding garden peas that these
plants passed on certain fixed characters, as the shape of the
seed, the color of the pod when ripe, and others, and that when
two pea plants of different characters were crossed, one of these

HUNTER, CIV. BI. 17

258

HEREDITY AND VARIATION

^^ ^^ ^-X

ooo

characters would be likely to appear in the offspring of the
second generation in the ratio of three to one. Such characters
as would appear to the exclusion of others in the first crossing of

the plants were called dominant,
the ones not appearing, reces
sive characteristics. When these
seeds were again sown the ones
bearing a recessive characteris
tic would produce only peas
with this recessive characteris
tic, but the ones with a domi
nant characteristic might give
rise to a pure dominant or to
offspring having partly a domi
nant and partly a recessive
character ; pure dominants be
ing to the mixed offspring in the
ratio of 1 to 2. The pure domi
nants if bred with others like
themselves would produce only
pure dominants, but the cross
breeds would again produce
mixed offspring of three kinds

Illustration of Mendel's Law. , , , . r ,

in the ratio of one dominant
to two cross breeds and one

recessive. The feature of this work that interests us is that unit
characters are passed along by heredity in the germ cells pure,
that is, unchanged, from one generation to another, and inde
pendently of each other.

Determiners of Character. A child then resembles his par
ents in some definite particulars because certain determiners of
characters have been present in the germ cells of one of the
parents. If the determiner of a certain character is absent
from the germ cells of both parents, it will be absent in all of
their offspring.

These discoveries of Mendel are of the greatest importance in
plant and animal breeding because they enable the breeder to

HEREDITY AND VARIATION

259

isolate certain characters and by proper selection to breed varieties
which have these desired characters, instead of waiting for a chance
union of the desired characters by nature.

Animal Breeding. It has been pointed out that the domesti
cation of wild animals, the horse, cattle, sheep, goats, and the dog,
marked a great advance in civilization in the history of the earth's
peoples. As the young of
these animals came to be
bred in captivity the peo
ples owning them would
undoubtedly pick out the
strongest and best of
the offspring, killing off
the others for food. Thus
they came unconsciously
to select and aid nature
in producing a stronger
and better stock. Later
man began to recognize
certain characters that he
wished to have in horses,
dogs, or cattle, and so by
slow processes of breeding
and " crossing " or hy
bridizing one nearly allied
form with another the
numerous groups of do
mesticated animals began
to appear.

In Darwin's time ani
mal breeding was so far
advanced that he got his
ideas of selection by na
ture in evolution from the artificial selection practiced by animal
breeders. A glance at the pictures will give some idea of the
changes that have taken place in the form of some animals
since man began to breed them a few thousand years ago.

What has resulted from artificial selection
among dogs. (After Romanes.)

260

HEREDITY AND VARIATION

Some Domesticated Animals. Our domesticated dogs are
descended from a number of wolflike forms in various parts of the
world. All the present races of cats, on the other hand, seem to
be traced back to Egypt. Modern horses are first noted in
Europe and Asia, but far older forms flourished on the earth in
former geologic periods. It is interesting to note that America
was the original home of the horse, although at the time of the

earliest explorers the horse
was unknown here, the
wild horse of the Western
plains having arisen from
horses introduced by the
Spaniards. Long ages ago,
the first ancestors of the
horse were probably little
animals about the size of

The four-toed ancestor of the present horse,

restored from a study of its fossil skeleton, a IOX. I he earliest horse

(After Knight in American Museum of Nat- we haye knowledge of had
ural History.) ^

four toes on the fore and

three toes on the hind foot. Thousands of years later we find a
larger horse, the size of a sheep, with a three-toed foot. By
gradual changes, caused by the tendency of the animals to vary
and by the action of the surroundings upon the animal in preserv
ing these variations, there was eventually produced our present
horse, an animal with legs adapted for rapid locomotion, with
feet particularly fitted for the life in open fields, and with teeth
which serve well to seize and grind herbage. Knowledge of this
sort was also used by Darwin to show that constant changes in
the form of animals have been taking place since life began on
the earth.

The horse, which for some reason disappeared in this country,
continued to exist in Europe, and man, emerging from his early
savage condition, began to make use of the animal. We know the
horse was domesticated in early Biblical times, and that he soon
became one of man's most valued servants. In more recent
times, man has begun to change the horse by breeding for certain
desired characteristics. In this manner have been established and

HEREDITY AND VARIATION 261

improved the various types of horses familiar to us as draft horses,
coach horses, hackneys, and the trotters.

It is needless to say that all the various domesticated animals
have been tremendously changed in a similar manner since civilized
man has come to live on the earth. When we realize the very
great amount of money invested in domesticated animals ; that
there are over 60,000,000 each of sheep, cattle, and swine and
over 20,000,000 horses owned in this country, then we may see
how very important a part the domestic animals play in our lives.

Improvement of Man. If the stock of domesticated animals
can be improved, it is not unfair to ask if the health and vigor
of the future generations of men and women on the earth might
not be improved by applying to them the laws of selection. This
improvement of the future race has a number of factors in which
we as individuals may play a part. These are personal hygiene,
selection of healthy mates, and the betterment of the environment.

Personal Hygiene. In the first place, good health is the one
greatest asset in life. We may be born with a poor bodily machine,
but if we learn to recognize its defects and care for it properly,
we may make it do its required work effectively. If certain muscles
are poorly developed, then by proper exercise we may make them
stronger. If our eyes have some defect, we can have it remedied
by wearing glasses. If certain drugs or alcohol lower the efficiency
of the machine, we can avoid their use. With proper care a poorly
developed body may be improved and do effective work.

Eugenics. When people marry there are certain things that
the individual as well as the race should demand. The most
important of these is freedom from germ diseases which might be
handed down to the offspring. Tuberculosis, syphilis, that dread
disease which cripples and kills hundreds of thousands of innocent
children, epilepsy, and feeble-mindedness are handicaps which it
is not only unfair but criminal to hand down to posterity. The
science of being well born is called eugenics.

The Jukes. Studies have been made on a number of different
families in this country, in which mental and moral defects were
present in one or both of the original parents. The "Jukes "
family is a notorious example. The first mother is known as

232

HEREDITY AND VARIATION

" Margaret, the mother of criminals." In seventy-five years the
progenjr of the original generation has cost the state of New York
over a million and a quarter of dollars, besides giving over to the

In this and the following diagrams the circle represents a female, the square a
male. (N) means normal ; Q means feeble-minded ; A, alcoholic ; T, tuber
cular ; Sx, sexually immoral ; Sy, having syphilis. This chart shows the
record of a certain family for three generations. A normal woman married
an alcoholic and tubercular man. He must have been feeble-minded
also as two of his children were born feeble-minded. One of these children
married another feeble-minded woman, and of their five children two died in
infancy and three were feeble-minded. (After Davenport.)

care of prisons and asylums considerably over a hundred feeble
minded, alcoholic, immoral, or criminal persons. Another case
recently studied is the " Kallikak " family. 1 This family has
been traced back to the War of the Revolution, when a young
soldier named Martin Kallikak seduced a feeble-minded girl.

This chart shows that feeble-mindedness is a charactsristic sure to be handed
down in a family where it exists. The feeble-minded woman at the top left
of the chart married twice. The first children from a normal father are all
normal, but the other children from an alcoholic father are all feeble-minded.
Th-3 right-hand side of the chart shows a terrible record of feeble-mindedness.
Should feeble-minded people be allowed to marry? (After Davenport.)

.*The name Kallikak is fictitious.

HEREDITY. AND VARIATION 263

She had a feeble-minded son from whom there have been to the
present time 480 descendants. Of these 33 were sexually immoral,
24 confirmed drunkards, 3 epileptics, and 143 feeble-minded. The
man who started this terrible line of immorality and feeble-minded-
ness later married a normal Quaker girl. From this couple a line
of 496 descendants have come, with no cases of feeble-mindedness.
The evidence and the moral speak for themselves !

Parasitism and its Cost to Society. Hundreds of families
such as those described above exist to-day, spreading disease,
immorality, and crime to all parts of this country. The cost to
society of such families is very severe. Just as certain animals
or plants become parasitic on other plants or animals, these families
have become parasitic on society. They not only do harm to others
by corrupting, stealing, or spreading disease, but they are actually
protected and cared for by the state out of public money. Largely
for them the poorhouse and the asylum exist. They take from
society, but they give nothing in return. They are true parasites.

The Remedy. If such people were lower animals, we would
probably kill them off to prevent them from spreading. Humanity
will not allow this, but we do have the remedy of separating the
sexes in asylums or other places and in various ways preventing
intermarriage and the possibilities of perpetuating such a low and
degenerate race. Remedies of this sort have been tried success
fully in Europe and are now meeting with success in this country.

Blood Tells. Eugenics show us, on the other hand, in a study
of the families in which are brilliant men and women, the fact that
the descendants have received the good inheritance from their
ancestors. The following, taken from Davenport's Heredity in
Relation to Eugenics, illustrates how one family has been famous
in American History.

In 1667 Elizabeth Tuttle, " of strong will, and of extreme
intellectual vigor, married Richard Edwards of Hartford, Conn.,
a man of high repute and great erudition. From their one son
descended another son, Jonathan Edwards, a noted divine, and
president of Princeton College. Of the descendants of Jonathan
Edwards much has been written ; a brief catalogue must suffice :
Jonathan Edwards, Jr., president of Union College; Timothy

264 HEREDITY AND VARIATION

Dwight, president of Yale ; Sereno Edwards Dwight, president of
Hamilton College; Theodore Dwight Woolsey, for twenty-five
years president of Yale College ; Sarah, wife of Tapping Reeve,

6*6

This record shows the inheritance of artistic ability (black circles arid squares).
(After Davenport.)

founder of Litchfield Law School, herself no mean lawyer ; Daniel
Tyler, a general in the Civil War and founder of the iron indus
tries of North Alabama ; Timothy Dwight, second, president of
Yale University from 1886 to 1898 ; Theodore William Dwight,
founder and for thirty-three years warden of Columbia Law
School ; Henrietta Frances, wife of Eli Whitney, inventor of the
cotton gin, who, burning the midnight oil by the side of her ingen
ious husband, helped him to his enduring fame ; Merrill Edwards
Gates, president of Amherst College; Catherine Maria Sedg-
wick of graceful pen; Charles Sedgwick Minot, authority on
biology and embryology in the Harvard Medical School ; Edith
Kermit Carow, wife of Theodore Roosevelt ; and Winston Churchill,
the author of Coniston and other well-known novels."

Of the daughters of Elizabeth Tuttle distinguished descendants
also came. Robert Treat Paine, signer of the Declaration of
Independence; Chief Justice of the United States Morrison R.
Waite ; Ulysses S. Grant and Grover Cleveland, presidents of the
United States. These and many other prominent men and women
can trace the characters which enabled them to occupy the posi
tions of culture and learning they held back to Elizabeth Tuttle.

Euthenics. Euthenics, the betterment of the environment,
is another important factor in the production of a stronger race.
The strongest physical characteristics may be ruined if the sur
roundings are unwholesome and unsanitary. The slums of a city

HEREDITY AND VARIATION 265

are " at once symptom, effect, and cause of evil." A city which
allows foul tenements, narrow streets, and crowded slums to exist
will spend too much for police protection, for charity, and for
hospitals.

Every improvement in surroundings means improvement of the
chances of survival of the race. In the spring of 1913 the health
department and street-cleaning department of the city of New
York cooperated to bring about a " clean up " of all filth, dirt, and
rubbish from the houses, streets, and vacant lots in that city. Dur
ing the summer of 1913 the health department reported a smaller
percentage of deaths of babies than ever before. We must draw
our own conclusions. Clean streets and houses, clean milk and
pure water, sanitary housing, and careful medical inspection all
do their part in maintaining a low rate of illness and death, thus
reacting upon the health of the citizens of the future. It will be
the purpose of the following pages to show how we may best care
for our own bodies and how We may better the environment in
which we are placed.

REFERENCE BOOKS

ELEMENTARY

Hunter, Laboratory Problems in Civic Biology. American Book Company.
Bailey, Plant Breeding. Macmillan and Company.
Harwood, New Creations in Plant Life. The Macmillan Company.
Jordan, The Heredity of Richard Roe. American Unitarian Association.
Sharpe, Laboratory Manual, pp. 64-72, 345-347. American Book Company.

ADVANCED

Allen, Civics and Health. Ginn and Company.

Coulter, Castle, East, Tower, and Davenport, Heredity and Eugenics. University of

Chicago Press.

Davenport, Heredity in Relation to Eugenics. Henry Holt and Company.
De Vries, Plant Breeding. Open Court Publishing Company.
Goddard, The Kallikak Family. The Macmillan Company.
Kellicott, The Social Direction of Human Evolution. Appleton Company.
Punnet, Mendelism. The Macmillan Company.

Richards, Helen M. Euthenics, the Science of Controllable Environment.
Walter, Genetics. The Macmillan Company.

XVIII. THE HUMAN MACHINE AND ITS NEEDS

Problem. To obtain a general understanding of the parts
and uses of the bodily machine.

LABORATORY SUGGESTIONS

Demonstration. Review to show that the human body is a complex of
cells.

Laboratory demonstration by means of (a) human skeleton and (b)
manikin to show the position and gross structure of the chief organs of
man.

Man and his Environment. In the last chapter we saw that
one factor in the improvement of man lies in giving him better
surroundings. It will be the purpose of the following chapters
to show how man is fitted to live in the environment in which
he is placed. He comes in contact with air, light, water, soil,
food, and shelter which make his somewhat artificial environment ;
he must adapt himself to get the best he can out of this environ
ment.

The Needs of Living Things. We have already found that the
primary needs of plants and animals are the same. They both
need food, they both need to digest their food and to have it cir
culate in a fluid form to the cells where it will be used. They
both need oxygen so as to release the energy locked up in their
food. And they both need to reproduce so that their kind may be
continued on the earth. What is true of plants and other animals
is true of man.

The Needs of Simple and Complex Animals the Same.
The simplest animal, a single cell, has the same needs as the most
complex. The cell paramcecium feeds, digests, oxidizes its food,
and releases energy. The cells of the human body built up into
tissues have the same needs and perform the same functions as
the paramcecium. It is the cells of the body working together

266

THE HUMAN MACHINE

267

in groups as tissues and organs that make the complicated actions
of man possible. Division of labor has arisen because of the
complex needs and work of the organism.

The Human Body a Machine. In all animals, and the human
animal is no exception, the body has been likened to a machine
in that it turns over the latent or potential
energy stored up in food into kinetic
energy (mechanical work and heat),
which is manifested when we perform
work. One great difference exists be
tween an engine and the human body.
The engine uses fuel unlike the substance
out of which it is made. The human
body, on the other hand, uses for fuel
the same substances out of which it is
formed ; it may, indeed, use part of its
own substance for food. It must as well
do more than purely mechanical work.
The human organism must be so deli
cately adjusted to its surroundings that
it will react in a ready manner to stimuli
from without ; it must be able to utilize
its fuel (food) in the most economical
manner ; it must be fitted with machinery
for transforming the energy received from
food into various kinds of work ; it must
properly provide the machine with oxygen
so that the fuel will be oxidized, and the
products of oxidation must be carried
away, as well as other waste materials
which might harm the effectiveness of the machine. Most
important of all, the human machine must be able to repair
itself.

In order to understand better this complicated machine, the
human body, let us briefly examine the structure of its parts
and thus get a better idea of the interrelation of these parts and
of their functions.

The human body seen from
the side in longitudinal
section.

268

THE HUMAN MACHINE

The Skin. Covering the body is a protective structure called
the skin. Covered on the outside with dead cells, yet it is provided
with delicate sense organs, which give us perception of touch, taste,

smell, pressure, and temperature.
It also aids in getting wastes out
of the body by means of its sweat
glands and plays an important part
in equalizing the temperature of
the body.

Bones and Muscles. The body
is built around a framework of
bones. These bones, which are
bound together by tough ligaments,
fall naturally into two great groups,
the bones of the body proper, verte
bral column, ribs, breast bone, and
skull, which form the axial skeleton,
and the appendages, two sets of
bones which form the framework
of the arms and legs, which with
the bones which attach them to the
axial skeleton form the appendicular
skeleton.

To the bones are attached the
muscles of the body. Movement
is accomplished by contraction of
muscles, which are attached so as
to cause the bones to act as levers.
Bones also protect the nervous
system and other delicate organs.
They also help to give form and
rigidity to the body.

Hygiene of Muscles and Bones.
Young people especially need to
know how to prevent certain defects
which are largely the result of bad
habits of posture. Standing erect

Skeleton of a man. CR., cranium ;
CL., clavicle ; ST., sternum ;
H., humerus; V.C., vertebral
column ; R., radius; U., ulna ;
P., pelvic girdle ; C., carpals;
M ., metacarpals; Ph., phalanges;
F., femur ; Fi., fibula ; T., tibia ;
Tar., tarsals; MT., metatar-
sals.

THE HUMAN MACHINE

269

is an example of a good habit, round shoulders a bad habit of this
sort. The habit of a wrong position of bones and muscles once
formed is very hard to correct.
This can best be done by certain
corrective exercises at home or
in the gymnasium.

Round shoulders is most com
mon among people whose occu
pation causes them to stoop.
Drawing, writing, and a wrong
position when at one's desk are
among the causes. Exercises
which strengthen the back
muscles and cause the head to
be kept erect are helpful in form
ing the habit of erect carriage.

Slight curvature of the spine
either backward or forward is

helped most by exercises which Diagram showing action of biceps muscle.

tend to Straighten the body,

J '

such as stretching up with the

hands above the head. Lateral curvature of the spine, too often

caused by a " hunched-up " position at the school desk, may also

contracted; b, extended ;

s, scapula.

, humerus;

Three classes of levers in the human body ; bones and muscles act together.
A, a lever of the first class; B, a lever of the second class; C, a lever of the
third class.

be corrected by exercises which tend to lengthen the spinal
column.

It is the duty of every girl and boy to have good posture and

270

THE HUMAN MACHINE

Bad posture in the
schoolroom may
cause permanent
injury to the spine.

erect carriage, not only because of the better
state of health which comes with it, but also
because one's self-respect demands that each
one of us makes the best of the gifts that
nature has given us. An erect head, straight
shoulders, and elastic carriage go far toward
making their owner both liked and respected.

Other Body Structures. In spaces between
the muscles are found various other structures,
blood vessels, which carry blood to and from
the great pumping station, the heart, and
thence to all parts of the body; connective
tissue, which holds groups of muscle or other
cells together ; fat cells, scattered in various parts of the body ;
various gland cells, which manufacture enzymes ; and the cells
of the nervous system, which aid in directing the body parts.

Body Cavity. Within the body . is a cavity, which in life is
almost completely filled with various organs. A thin wall of
muscle called the diaphragm divides the body cavity into two
unequal spaces. In the upper space are found the heart and lungs,
in the lower, the digestive tract with its glands, the liver, kidneys,
and other structures (see page 267).

Digestion, Absorption, and Excretion. Running through the
body is a food tube in which undigested food is placed and from
which digested or liquid food is absorbed into the blood so that the
cells of the various organs which do the work may receive food.
Emptying into this food tube are various groups of gland ceils,
which pour digestive fluids over the solid foods, thus aiding in
changing them to liquids. Solid wastes are passed out through
the posterior end of the food tube, while liquid wastes are excreted
by means of glands called kidneys.

Work done by Cells. Food, prepared in the digestive tract,
and oxygen from the lungs are taken by the blood to the cells.
Bathed in liquid food, the cells do their work; they promote
the oxidization of food and the exchange of carbon dioxide for
oxygen in the blood, while other wastes of the cells are given off,
to pass eventually through the kidneys and out of the body.

THE HUMAN MACHINE 271

The Nervous System. The smooth working of the bodily
machine is due to another set of structures which direct the work
ing of the parts so that they will act in unison. This director is
the nervous system. We have seen that, in the simplest of animals,
one cell performs the functions necessary to its existence. In
the more complex animals, where groups of cells form tissues,
each having a different function, a nervous system is developed.
The functions of the human nervous system are : (1) the providing
of man with sensation, by means of which he gets in touch with the
world about him; (2) the connecting of organs in different parts of
the body so that they act as a united and harmonious whole; (3) the
giving to the human being a will, a provision for thought. Cooper
ation in word and deed is the end attained. We are all familiar
with examples of the cooperation of organs. You see food; the
thought comes that it is good to eat ; you reach out, take it, raise
it to the mouth ; the jaws move in response to your will ; the food
is chewed and swallowed. While digestion and absorption of the
food are taking place, the nervous system is still in control. The
nervous system also regulates pumping of blood over the body,
respiration, secretion of glands, and, indeed, every bodily function.
Man is the highest of all animals because of the extreme develop
ment of the nervous system. Man is the thinking animal, and as
such is master of the earth.

REFERENCE READING FOR THIS AND SUCCEEDING CHAPTERS ON HUMAN BIOLOGY

ELEMENTARY

Hunter, Laboratory Problems in Civic Biology. American Book Company.

Davison, The Human Body and Health. American Book Company.

Gulick, The Gulick Hygiene Series. Ginn and Company.

Overton, General Hygiene. American Book Company.

Ritchie, Human Physiology. World Book Company.

Sharpe, Laboratory Manual in Botany, pages 218-225. American Book Company.

ADVANCED

Halliburton, Kirk's Handbook of Physiology. P. Blakiston's Son and Company.
Hough and Sedgwick, The Human Mechanism. Ginn and Company.
Howell, Physiology, 3d edition. W. B. Saunders Company.
Schafer, Textbook of Physiology. The Macmillan Company.
Stiles, Nutritional Physiology. W. B. Saunders Company.
Verworn, General Physiology. The Macmillan Company.

XIX. FOODS AND DIETARIES

Problems. A study of foods to determine:
(a) Their nutritive value.

(ft) The relation of work, environment, age, sex, and diges
tibility of foods to diet.

(d) The daily Calorie requirement.

(e) Food adulteration.

(/) The relation of alcohol to the human system.

LABORATORY SUGGESTIONS

Laboratory exercise. Composition of common foods. The series of
food charts supplied by the United States Department of Agriculture
makes an excellent basis for a laboratory exercise to determine common
foods rich in (a) water, (6) starch, (c) sugar, (d) fats or oils, (e) protein,
(/) salts, (0) refuse.

Demonstration. Method of using bomb calorimeter.

Laboratory and home exercise. To determine the best individual bal
anced dietary (using standard of Atwater, Chittenden, or Voit) as deter
mined by the use of the 100-Calorie portion.

Demonstration. Tests for some common adulterants.

Demonstration. Effect of alcohol on protein, e.g. white of egg.

Demonstration. Alcohol in some patent medicines.

Demonstration. Patent medicines containing acetanilid. Determina
tion of acetanilid.

Why we Need Food. A locomotive engine takes coal, water,
oxygen, from its environment. A living plant or animal takes
organic food, water, and oxygen from its environment. Both the
living and nonliving machine does the same thing with this fuel
or food. They oxidize it and release the energy in it. But the
living organism in addition may use the food to repair parts that
have broken down or even build new parts. Thus food may be
defined as something that releases energy or that forms material for

272

FOODS AND DIETARIES 273

the growth or repair of the body of a plant or animal. The mil
lions of cells of which the body is composed must be given material
which will form more living matter or material which can be oxi
dized to release energy when muscle cells move, or gland cells
secrete, or brain cells think.

Nutrients. Certain nutrient materials form the basis of food
of both plants and animals. These have been stated to be proteins
(such as lean meat, eggs, the gluten of bread),
carbohydrates (starches, sugars, gums, etc.), fats
and oils (both animal and vegetable), mineral
matter and water.

Proteins. Protein substances contain the
element nitrogen. Hence such foods are called
nitrogenous foods. Man must form the proto
plasm of his body (that is, the muscles, tendons,
nervous system, blood corpuscles, the living parts
of the bone and the skin, etc.) in part at least
from nitrogenous food. Some of this he ob- The""composition of
tains by eating the flesh of animals, and some milk- Why is it

he obtains directly from plants (for example,

peas and beans). Proteins are the only foods

available for tissue building. They may be oxidized to release

energy if occasion requires it.

Fats and Oils. Fats and oils, both animal and vegetable,
are the materials from which the body derives part of its energy.
The chemical formula of a fat shows that, compared with other
food substances, there is very little oxygen present; hence the
greater capacity of this substance for uniting with oxygen. The
rapid burning of fat compared with the slower combustion of a
piece of meat or a piece of bread illustrates this. A pound of butter
releases over twice as much energy to the body as does a pound of
sugar or a pound of steak. Human fatty tissue is formed in part
from fat eaten, but carbohydrate or even protein food may be
changed and stored in the body as fat.

Carbohydrates. We see that the carbohydrates, like the fats,
contain carbon, hydrogen, and oxygen. Carbohydrates are essen
tially energy-producing foods. They are, however, of use in build-

HUNTER, CIV. BI. - 18

274 FOODS AND DIETARIES

ing up or repairing tissue. It is certainly true that in both plants
and animals such foods pass directly, together with foods contain
ing nitrogen, to repair waste in tissues, thus giving the needed
proportion of carbon, oxygen, and hydrogen to unite with the
nitrogen in forming the protoplasm of the body.

Inorganic Foods. Water forms a large part of almost every
food substance. It forms about five sixths of a normal daily diet.

The human body, by weight, is
about two thirds water. About 90
per cent of the blood is water.
Water is absolutely essential in
passing off waste of the body.
When we drink water, we take
with it some of the inorganic salts
used by the body in the making of
Three portions of foods, each of bone and in the formation of proto-
which furnishes about the same p i asm< Sodium chloride (table

amount of nourishment.

salt), an important part of the

blood, is taken in as a flavoring upon our meats and vegetables.
Phosphate of lime and potash are important factors in the forma
tion of bone.

Phosphorus is a necessary substance for the making of living
matter, milk, eggs, meat, whole wheat, and dried peas and beans
containing small amounts of it. Iron also is an extremely impor
tant mineral, for it is used in the building of red blood cells. Meats,
eggs, peas and beans, spinach, and prunes, are foods containing
some iron.

Some other salts, compounds of calcium, magnesium, potassium,
and phosphorus, have been recently found to aid the body in many
of its most important functions. The beating of the heart, the
contraction of muscles, and the ability of the nerves to do their
work appear to be due to the presence of minute quantities of these
salts in the body.

Uses of Nutrients. The following table sums up the uses of
nutrients to man : l

1 Adapted from Atwater, Principles of Nutrition and Nutritive Value of Food,
U.S. Department of Agriculture, 1902.

FOODS AND DIETARIES

275

All serve as
fuel and yield
energy in form
of heat and mus
cular strength.

Protein Forms tissue (mus-

White of eggs (albumen), cles, tendon,

curd of milk (casein), lean and probably

meat, gluten of wheat, etc. fat).

Fats Form fatty tissue.

Fat of meat, butter, olive oil,
oils of corn and wheat, etc.

Carbohydrates Transformed into

Sugar, starch, etc. fat.

Mineral matters (ash). . . Aid in forming bone,
Phosphates of lime, potash, assist in diges-

soda, etc. tion, aid in ab

sorption and in
other ways help
the body parts
do their work.

Water used as a vehicle to carry nutrients, and enters into the compo
sition of living matter.

Common Foods contain the Nutrients. We have already
found in our plant 'study that various plant foods are rich in dif
ferent nutrients, carbohydrates forming the chief nutrient in the
foods we call cereals, breads, cake, fleshy fruits, sugars, jellies, and
the like. Fats and oils are most largely found in nuts and some
grains. Animal foods are our chief supply of protein. White of
egg and lean meat are almost pure protein and water. Proteins
are most abundant, as we should expect, in those plants which are
richly supplied with nitrogen ; peas and beans, and in grains and
nuts. Fats, which are melted into oils at the temperature of the
body, are represented by the fat in meats, bacon, pork, lard,
butter, and vegetable oils.

Water. Water is, as we have seen, a valuable part of food.
It makes up a very high percentage of fresh fruits and vegetables ;
it is also present in milk and eggs, less abundant in meats and fish,
and is lowest in dried foods and nuts. The amount of water in a
given food is often a decided factor in the cost of the given food,
as can easily be seen by reference to the chart on page 283.

Refuse. Some foods bought in the market may contain a
certain unusable portion. This we call refuse. Examples of

276

FOODS AND DIETARIES

INDIGESTIBLE
NUTRIENTS

DIO1 STIBL1 ';: RIHK TO

Z~D GTJ CIU

PROTEIN FATS

CARBO- MINERAL
HYDRATES MATTE
MUSCLE
MAKING FUEL INGREDIENTS

NUTRIENTS, ETC,
PER CENT.

10 20 30 40 50 60 70 80 90

FUEL VALUE OP
1 LB. (CALORIES)

400 800 1.200 2,000 2.200 2,400 2,800 3,200 36004

Mutton, leg
Pork, loin
Codfish, dressed
Beef, loin

Mutton, leg
Ham. smoked

Table of food values. Determine the percentage of water in codfish, loin of beef,
milk, potatoes. Percentage of refuse in leg of mutton, codfish, eggs, and
potatoes. What is the refuse in each case ? Find three foods containing a
high percentage of protein ; of fat ; of carbohydrate. Find some food in
which the proportions of protein, fat, and carbohydrate are combined in a
good proportion.

FOODS AND DIETARIES 277

refuse are bones in meat, shells of eggs or of shellfish, the covering
of plant cells which form the skins of potatoes or other vegetables.
The amount of refuse present also plays an important part in the
values of foods for the table. The table 1 on page 276 gives the per
centages of organic nutrients, water, and refuse present in some
common foods.

Fuel Values of Nutrients. In experiments performed by
Professor Atwater and others, and in the appended tables, the
value of food as a source of energy is stated in heat units called
Calories. A Calorie is the amount of heat required to raise the tem
perature of one kilogram of water from zero to one degree Centigrade.
This is about equivalent to raising one pound four degrees Fahren
heit. The fuel value of different foods may be computed in a
definite manner. This is done by burning a given portion of a
food (say one gram) in the apparatus known as a calorimeter.
By this means may be determined the number of degrees the
temperature of a given amount of water is raised during the process
of burning. It has thus been found that a gram of fat will liber
ate 9.3 Calories of heat, while a gram of starch or sugar only about
4 Calories. The burning value of fat is, therefore, over twice that
of carbohydrates. In a similar manner protein has been shown to
have about the same fuel value as carbohydrates, i.e. 4 Calories
to a gram. 1

The Relation of Work to Diet. It has been shown experimen
tally that a man doing hard, muscular work needs more food
than a person doing light work. The mere exercise gives the
individual a hearty appetite; he eats more and needs more of
all kinds of food than a man or boy doing light work. Especially
is it true that the person of sedentary habits, who does brain work,
should be careful to eat less food and food that will digest easily.
His protein food should also be reduced. Rich or hearty foods
may be left for the man who is doing hard manual labor out
of doors, for any extra work put on the digestive organs takes
away just so much from the ability of the brain to do its
work.

1 W. O. Atwater, Principles of Nutrition and Nutritive Value of Food, U.S. De
partment of Agriculture, 1902.

278

FOODS AND DIETARIES

OHice ol Eper,,,

Preparea D ,
Expert in Charge ot Nutrition Invesri

COMPOSITION OF FOOD MATERIALS.

Protein Fat Carbohydrates Ash Water ^B ,OM citeX.",

SHELLED BEAN, FRESH NAVY BEAN, DRY.

&at ___^ 58.9 ^^Water:l2.6
Fat:0.6

720 CALORICS PERPOUHO 1560 lAlORIf* J>[ I

STRING BEAN, GREEN.

^Carbohydrates: 7.1 *-? _ Ash-.O.B

Water:897 ^

L C. True: Director Expert in Cnarqe of Nutrition Investigations

COMPOSITION OF FOOD MATERIALS.

aa llllliinii i-v;-:^i ^%%i *> ^tue

otein r*t Carboh,d,at.s Ash Water ^1 , M C.^nt?

WHITE BREAD WHOLE WHEAT BREAD

Water: 35.3 Water: 38
^Protein: 9.2 Protein;9.7

Carbo CL

hydrates .'53. 1 hydr,ites:49.7

I. S. Department ot Agriculture Prepared by

OH.ceotI.pfrim.nl Stations C. f. UIGWORTrlY

COMPOSITION OF FOOD MATERIALS.

Prote.r,

Fun nuf: Protein: 1. 1

f Carbohydrates.:

IWrjJbL-, Ash:^ V //

. S. Department of Agriculture

Office ot Experiment Stations

A. C. True: Director

Prepared by
C. F. LANOWORrMY
I <pert in Ctw t)e ol Nutrition lnc:

COMPOSITION OF FOOD MATERIALS.

Carbohydrates 1000

FUR VALUE

IH STICK CANDY

1810 otooifs ^Carbohydrates: 96.5

^~ ^ idT\^

Foods of plant origin. Select 5 foods containing a high percentage of protein,
5 with a high percentage of carbohydrates, 5 with a high percentage of water.
Do vegetable foods contain much fat ? Which of the above-mentioned foods
have the highest burning value ?

FOODS AND DIETARIES

279

AC. True Director . tpert in ClWge of Nuf'rtion

COMPOSITION OF FOOD MATERIALS.

BB^a nim r~n wMk

A. C. True- Oiifcui tlftit in Craig* ol rlulmjon ln*st,it,ons

COMPOSITION OF FOOD MATERIALS.
BBSS minium >:'.: i w//m I

COMPOSITION OF FOOD MATERIALS
BBS9 nii|i!iiin i i VW///A ^^ m v ^

P-ote.n Fjt Ci.bollyd'.Ul Ah Water

WHOLE EGG

C.F. lAflGWORTHY
Elprt in Chjrge of Nutrition Inveitifl

COMPOSITION OF FOOD MATERIALS.

.Foods largely of animal origin. Compare with the previous chart with refer
ence to amount of protein, carbohydrate, and fat in foods. Compare the
burning value of plant and animal foods. Compare the relative percentage
of water in both kinds of foods.

280

FOODS AND DIETARIES

U S Otfttmtnt ot Agriculture Prepared by

Oll.Cf o> Eioer.meni Stlt.ons C. f UNGWORTHY

A. C. True: Director Expert in Charge ot Nutrition Investigations

COMPOSITION OF FOOD MATERIALS.

WHOLE MILK

SKIM MILK

FlXl MUK: l65uiOl[SPfPPOiW>

BUTTERMILK

Proteir>:3.0 Fat: I8.5-, J
Ash:0 5

Carbohydrates:4.8

MLUC: l60cU. IH>MD Fun VUM: 880 OLOI

The Relation of Environment to Diet. We are all aware of the
fact that the body seems to crave more food in winter than in

summer. The temperature of
the body is maintained at 98.6
in winter as in summer, but
much more heat is lost from the
body in cold weather. Hence
feeding in winter should be for
the purpose of maintaining our
fuel supply. We need heat-
producing food, and we need
more food in winter than in
summer. We may use carbo
hydrates for this purpose, as
they are economical and diges
tible. The inhabitants of cold
countries get their heat-releasing
foods largely from fats. In
tropical countries and in hot
weather little protein should
be eaten and a considerable
amount of fresh fruit used.

The Relation of Age to Diet. As we will see a little later, age
is a factor not only in determining the kind but the amount of
food to be used. Young children require far less food than do
those of older growth or adults. The body constantly increases
in weight until young manhood, or womanhood, then its weight
remains nearly stationary, varying with health or illness. It is
evident that food in adults simply repairs the waste of cells and
is used to supply energy. Elderly people need much less protein
than do younger persons. But inasmuch as the amount of food
to be taken into the body should be in proportion to the body
weight, it is also evident that growing children do not, as is popu
larly supposed, need as much food as grown-ups.

The Relation of Sex to Diet. As a rule boys need more food
than girls, and men than women. This seems to be due to, first,
the more active muscular life of the man and, secondly, to the

The composition of milk.

FOODS AND DIETARIES 281

greater amount of fat in the tissues of the woman, making
loss of heat less. Larger bodies, because of greater surface,
give off more heat than smaller ones. Men are usually larger
in bulk than are women, another reason for more food in their
case.

The Relation of Digestibility to Diet. Animal foods in general
may be said to be more completely digested within the body than
plant foods. This is largely due to the fact that plant cells have
woody walls that the digestive juices cannot act upon. Cereals
and legumes are less digestible foods than are dairy products,
meat, or fish. This does not mean necessarily that these foods
would not agree with you or me but that in general the body would
get less nourishment out of the total amount available.

The agreement or disagreement of food with an individual is
largely a personal matter. I, for example, cannot eat raw toma
toes without suffering from indigestion, while some one else Can
digest tomatoes but not strawberries. Each individual should
learn early in life the foods that disagree with him personally
and leave such foods out of his dietary. For " what is one man's
meat may be another man's poison."

The Relation of Cost of Food to Diet. It is a mistaken notion
that the best foods are always the most expensive. A glance at
the table (page 283) will show us that both fuel value and tissue-
building value is present in some foods from vegetable sources, as
well as in those from animal sources, and that the vegetable foods
are much cheaper. The American people are far less economical
in their purchase of food than most other nations. Nearly one
half of the total income of the average workingman is spent on
food. Not only does he spend a large amount on food, but he
wastes money in purchasing the wrong kinds of food. A compari
son of the daily diets of persons in various occupations in this
and other countries shows that as a rule we eat more than is nec
essary to supply the necessary fuel and repair, and that our working-
men eat more than those of other countries. Another waste of
money by the American is in the false notion that a large propor
tion of the daily dietary should be meat. Many people think
that the most expensive cuts of meat are the most nutritious.

282 FOODS AND DIETARIES

The falsity of this idea may be seen by a careful study of the tables
on pages 283 and 286.

The Best Dietary. Inasmuch as all living substance contains
nitrogen, it is evident that protein food must form a part of the
dietary ; but protein alone is not usable. If more protein is eaten
than the body requires, then immediately the liver and kidneys
have to work overtime to get rid of the excess of protein which
forms a poisonous waste harmful to the body. We must take
foods that will give us, as nearly as possible, the proportion of
the different chemical elements as they are contained in proto
plasm. It has been found, as a result of studies of Atwater and
others, that a man who does muscular work requires a little less
than one quarter of a pound of protein, the same amount of fat,
and about one pound of carbohydrate to provide for the growth,
waste, and repair of the body and the energy used up in one day.

The Daily Calorie Requirement. Put in another way, At-
water's standard for a man at light exercise is food enough to
yield 2816 Calories ; of these, 410 Calories are from protein, 930
Calories from fat, and 1476 Calories from carbohydrate. That is,
for every 100 Calories furnished by the food, 14 are from protein,
32 from fat, and 54 from carbohydrate. In exact numbers, the
day's ration as advocated by Atwater would contain about 100
grams or 3.7 ounces protein, 100 grams or 3.7 ounces fat, and 360
grams or 13 ounces carbohydrate. Professor Chittenden of Yale
University, another food expert, thinks we need proteins, fats, and
carbohydrates in about the proportion of 1 to 3 to 6, thus differing
from Atwater in giving less protein in proportion. Chittenden's
standard for the same man is food to yield a total of 2360 Calories,
of which protein furnishes 236 Calories, fat 708 Calories, and car
bohydrates 1416 Calories. For every 100 Calories furnished by
the food, 10 are from protein, 30 from fat, 60 from carbohydrate.
In actual amount the Chittenden diet would contain 2.16 ounces
protein, 2.83 ounces fat, and 13 ounces carbohydrate. A German
named Voit gives as ideal 25 Calories from proteins, 20 from
fat, and 55 from carbohydrate, out of every 100 Calories; this
is nearer our actual daily ration. In addition, an ounce of salt
and nearly one hundred ounces of water are used in a day.

FOODS AND DIETARIES

283

PROTEIN FATS CARBOHYDRATES

FUEL VALUE

go
FOOD

MATERIALS S

TEN CENTS
WILL BUY

POUNDS OF NUTRIENTS AND CALORIES OF FUEL VALUE
IN 10 CENTS WORTH

1 LB. 2 LBS. 3 LBS.

CENTS

POUNDS

2. 000 CAL. 4, 000 CAL. 6. OOO CAL.

Beef, round 14

.71

Beef, sirloin 20

.CO

mmm

Beef, shoulder 12

.83

Mutton, leg 16

.63

mmm

Pork, loin 12

.83

Pork, salt, fat 12

.83

Ham, smoked 18

.56

Codfish, fresh,
dressed

1.00

Oysters 35 cents
per quart

.56

Milk, 6 centa
per quart

3.33

mmmmm

Butter 25

.40

M1MM

Cheese 16

.63

Eggs, 24 cents 1Q
per dozen

.63

Wheat bread 5

2 00

i 1

Corn meal 2%

4.00

113 : ,1

Oat meal 4

2.50

M \ ; \

Beans, white, dried 5

2.00

\\ ' ''/A

Rice 8

1.25

' !

mmmmi^mm^mm

Potatoes, 6O cents i
per bushel

10.00

SJI , 1

Sugar 6

1.C7

Table showing tha cost of various foods. Using this table, make up an economical
dietary for one day, three meals, for a man doing moderate work. Give
reasons for the amount of food used and for your choice of foods. Make up
another dietary in the same manner, using expensive foods. What is the
difference in your bill for the day ?

284 FOODS AND DIETARIES

A Mixed Diet Best. Knowing the proportion of the different
food substances required by man, it will be an easy matter to
determine from the tables and charts shown you the best foods
for use in a mixed diet. Meats contain too much nitrogen in
proportion to the other substances. In milk, the proportion of
proteins, carbohydrates, and fats is nearly right to make proto
plasm ; a considerable amount of mineral matter being also pres
ent. For these reasons, milk is extensively used as a food for
children, as it combines food material for the forming of proto
plasm with mineral matter for the building of bone. Some vege
tables (for example, peas and beans) contain a large amount
of nitrogenous material but in a less digestible form than is found
in some other foods. Vegetarians, then, are correct in theory
when they state that a diet of vegetables may contain every
thing necessary to sustain life. But a mixed diet containing
meat is healthier. A purely vegetable diet contains much waste
material, such as the cellulose forming the walls of plant cells,
which is indigestible. It has been recently discovered that the
outer coats of some grains, as rice, contain certain substances
(enzymes) which aid in digestion. In the case of polished rice,
when this outer coat is removed the grain has much less food value.

Daily Fuel Needs of the Body. It has been pointed out that
the daily diet should differ widely according to age, occupation,
time of year, etc. The following table shows the daily fuel needs
for several ages and occupations : '

DAILY CALORIE NEEDS (APPROXIMATELY)

1. For child under 2 years / . . 900 Calories

2. For child from 2-5 years ' . . 1200 Calories

3. For child from 6-9 years 1500 Calories

4. For child from 10-12 years . ' . 1800 Calories

5. For child from 12-14 (woman, light work, also) . . 2100 Calories

6. For boy (12-14), girl (15-16), man, sedentary . . . 2400 Calories

7. For boy (15-16) (man, light muscular work) . . . 2700 Calories

8. For man, moderately active muscular work .... 3000 Calories

9. For farmer (busy season) 3200 to 4000 Calories

10. For ditchers, excavators, etc 4000 to 5000 Calories

11. For lumbermen, etc 5000 and more Calories

FOODS AND DIETARIES 285

Normal Heat Output. The following table gives the result of
some experiments made to determine the hourly and daily expen
diture of energy of the average normal grown person when asleep
and awake, at work or at rest :

AVERAGE NORMAL OUTPUT OF HEAT FROM THE BODY

CONDITIONS OP MUSCULAR ACTIVITY

AVERAGE
CALORIES
PER HOUR

Man at rest, sleeping . . . ' . . '. . .
Man at rest, awake, sitting up . -. ;.
Man at light muscular exercise , * .?,. ... ..

Man at moderately active muscular exercise
Man at severe muscular exercise . . . f
Man at very severe muscular exercise . i

65 Calories
100 Calories
170 Calories
290 Calories
450 Calories
600 Calories

It is very simple to use such a table in calculating the number
of Calories which are spent in twenty-four hours under different
bodily conditions. For example, suppose the case of a clerk or
school teacher leading a relatively inactive life, who

sleeps for 9 hours .

X 65 Calories 585

works at desk 9 hours . . . . , .

X 100 Calories = 900

reads, writes, or studies 4 hours . ....
walks or does light exercise 2 hours .

X 100 Calories = 400
X 170 Calories = 340

2225

This comes out, as we see, very close to example 6 of the table l
on page 284.

How we may Find whether we are Eating a properly Balanced
Diet. We already know approximately our daily Calorie needs
and about the proportion of protein, fat, and carbohydrate needed.
Dr. Irving Fisher of Yale University has worked out a very easy
method of determining whether one is living on a proper diet. He
has made up a number of tables, in which he has designated
portions of food, each of which furnishes 100 Calories of energy.

1 The above tables have been taken from the excellent pamphlet of the Cornell
Reading Course, No. 6, Human Nutrition.

TABLE OF 100 CALORIE PORTIONS MODIFIED FROM FISHER

FOOD

PORT. CONTAINING
100 CALORIES

2 o,

111

CAL. FURNISHED

PRICE

CARBO
HYDRATE

m
h-J

100 CAL.
POR.

Oysters . . .

1 doz.

6.8

.175

.07

Bean soup . .

\ small serving

2.6

.007

Cream of corn .

f ordin. serv.

3.1

.02

Vegetable soup .

\ ordin. serv.

2.4

.01

Cod fish (fresh)

ordin. serv.

.12

.04

Salmon (canned)

small serv.

1.75

.22

.03

Chicken . . .

\ large serv.

1.75

.22

.05

Veal cutlet . .

f large serv.

2.4

.28

.045

Beef, corned . .

\ large serv.

1.0

.16

.01

Beef, sirloin . .

small serv.

1.6

.34

.04

Beef, round . .

small serv.

1.8

.24

.025

Ham, lean . .

ordin. serv.

1.1

.22

.015

Lamb chops . .

\ ordin. serv.

1.0

.20

.013

Mutton, leg . .

ordin. serv.

1.2

.20

.015

Eggs, boiled . .

1 large egg

2.1

.30 doz.

.025

Eggs, scrambled .

\\ ordin. serv.

2.5

.30 doz.

.03

Beans, baked . .

side dish

2.66

.08

.013

Potatoes, mashed

ordin. serv.

3.2

.02

.005

Macaroni . .

\ large serv.

.95

.10

.01

Potato salad . .

ordin. serv.

2.25

.20

.025

Tomatoes, sliced

4 large serv.

15.

.10

Rolls, plain . .

1 large roll

1.2

.10 doz.

.01

Butter . . .

ordin. pat

.44

99.5

.35

.01

Wheat bread

1 small slice

.96

.07

.005

Chocolate cake .

\ ord. sq. piece

.98

.32

.02

Gingerbread

\ ord. sq. piece

.96

.16

.01

Custard pudding

ordin. serv.

3.25

.15

.03

Rice pudding . .

very small serv.

2.65

.13

.02

Apple pie . .

\ piece

1.3

.013

Cheese, American

1^ cu. in.

.77

.19

.01

Crackers (soda) .

2 crackers

.10

.007

Currant jelly . .

2 heap, spoons

1.1

.40

.025

Sugar ....

3 teaspoons

.86

100

.06

.003

Milk as bought .

small glass

4.9

.05

.015

Milk, cond., sweet

4 teaspoons

1.06

.01

Oranges . . .

1 large one

9.4

.025

Peanuts . . .

13 double ones

.62

.004

Almonds, shelled

8-15

.53

.025

286

FOODS AND DIETARIES 287

The tables show the proportion of protein, fat, and carbohydrate
in each food, so that it is a simple matter by using such a table
to estimate the proportions of the various nutrients in our dietary.
We may depend upon taking somewhere near the proper amount
of food if we take a diet based upon either Atwater's, Chittenden's,
or Voit's standard. One of the most interesting and useful
pieces of home work that you can do is to estimate your own
personal dietary, using the tables giving the 100-Calorie portion
to see if you have a properly balanced diet. From the table on
page 286 make out a simple dietary for yourself for one day,
estimating your own needs in Calories and then picking out 100-
Calorie portions of food which will give you the proper propor
tions of protein, fat, and carbohydrate.

From the preceding table plan a well-balanced and cheap dietary
for one day for a family of five, two adults and three children.
Make a second dietary for the same time and same number of
people which shall give approximately the same amount of tissue
and energy producing food from more expensive materials.

Food Waste in the Kitchen. Much loss occurs in the im
proper cooking of foods. Meats especially, when overdone,
lose much of their flavor and are far less easily digested than when
they are cooked rare. The chief reasons for cooking meats are
that the muscle fibers may be loosened and softened, and that the
bacteria or other parasites in the meat may be killed by the heat.
The common method of frying makes foods less digestible. Stew
ing is an economical as well as healthful method. A good way to
prepare meat, either for stew or soup, is to place the meat, cut in
small pieces, in cold water, and allow it to simmer for several
hours. Rapid boiling toughens the muscle fibers by the too rapid
coagulation of the albuminous matter in them, just as the white
of egg becomes tough when boiled too long. Boiling and roasting
are excellent methods of cooking meat. In order to prevent the
loss of the nutrients in roasting, it is well to baste the meat fre
quently ; thus a crust is formed on the outer surface of the meat,
which prevents the escape of the juices from the inside.

Vegetables are cooked in order that the cells containing starch
grains may be burst open, thus allowing the starch to be more

288 FOODS AND DIETARIES

easily attacked by the digestive fluids. Inasmuch as water may
dissolve out nutrients from vegetable tissues, it is best to boil
them rapidly in a small amount of water. This gives less time
for the solvent action to take place. Vegetables should be cooked
with the outer skin left on when it is possible.

Adulterations in Foods. The addition of some cheaper sub
stance to a food, or the subtraction of some valuable substance
from a food, with the view to cheating the purchaser, is known
as adulteration. Many foods which are artificially manufactured
have been adulterated to such an extent as to bo almost unfit for
food, or even harmful. One of the commonest adulterations is the
substitution of grape sugar (glucose) for cane sugar. Glucose,
however, is not a harmful adulterant. It is used largely in candy
making. Flour and other cereal foods are sometimes adulterated
with some cheap substitutes, as bran or sawdust. Alum is some
times added to make flour whiter. Probably the food which suffers
most from adulteration is milk, as water can be added without
the average person being the wiser. By means of an inexpensive
instrument known as a lactometer, this cheat may easily be de
tected. In most cities, the milk supply is carefully safeguarded,
because of the danger of spreading typhoid fever from impure
milk (see Chapter XX). Before the pure food law was passed in
1906, milk was frequently adulterated with substances like for
malin to make it keep sweet longer. Such preservatives are
harmful, and it is now against the law to add anything whatever
to milk.

Coffee, cocoa, and spices are subject to great adulteration;
cottonseed oil is often substituted for olive oil ; butter is too
frequently artificial ; while honey, sirups of various kinds, cider
and vinegar, have all been found to be either artificially made from
cheaper substitutes or to contain such substitutes.

Pure Food Laws. Thanks to the National Pure Food and
Drug Law passed by Congress in 1906, and to the. activity of
various city and state boards of health, the opportunity to pass
adulterated foods on the public is greatly lessened. This law
compels manufacturers of foods or medicines to state the compo
sition of their products on the labels placed on the jars or bottles.

FOODS AND DIETARIES 289

So if a person reads the label he can determine exactly what he
is getting for his money.

Impure Water. Great danger comes from drinking impure
water. This subject has already been discussed under Bacteria,
where it was seen that the spread of typhoid fever in particular is
due to a contaminated water supply. As citizens, we must aid all
legislation that will safeguard the water used by our towns and
cities. Boiling water for ten minutes or longer will render it
safe from all organic impurities.

Stimulants. We have learned that food is anything that
supplies building material or releases energy in the body; but
some materials used by man, presumably as food, do not come
under this head. Such are tea and coffee. When taken in
moderate quantities, they produce a temporary increase in the
vital activities of the person taking them. This is said to be a
stimulation ; and material taken into the digestive tract, produc
ing this, is called a stimulant. In moderation, tea and coffee
appear to be harmless. Some people, however, cannot use either
without ill effects, even in small quantity. It is the habit formed
of relying upon the stimulus given by tea or coffee that makes
them a danger to man. Cocoa and chocolate, although both
contain a stimulant, are in addition good foods, having from 12
per cent to 21 per cent of protein, from 29 per cent to 48 per cent
fat, and over 30 per cent carbohydrate in their composition.

Is Alcohol a Food ? The question of the use of alcohol has
been of late years a matter of absorbing interest and importance
among physiologists. A few years ago Dr. Atwater performed a
series of very careful experiments by means of the respiration
calorimeter, to ascertain whether alcohol is of use to the body as
food. 1 In these experiments the subjects were given, instead of
their daily allotment of carbohydrates and fats, enough alcohol
to supply the same amount of energy that these foods would
have given. The amount was calculated to be about two and
one half ounces per day, about as much as would be contained in

1 Alcohol is made up of carbon, oxygen, and hydrogen. It is very easily oxidized,
but it cannot, as is shown by the chemical formula, be of use to the body in tissue
building, because of its lack of nitrogen.
HUNTER, CIV. BI. 19

290 FOODS AND DIETARIES

a bottle of light wine. 1 This alcohol was administered in small
doses six times during the day. Professor Atwater's results may
be summed up briefly as follows :

1. The alcohol administered was almost all oxidized in the body.

2. The potential energy in the alcohol was transformed into heat
or muscular work.

3. The body did about as well with the rations including alco
hol as it did without it.

The committee of fifty eminent men appointed to report on the
physiological aspects of the drink problem reported that a large
number of scientific men state that they are in the habit of taking
alcoholic liquor in small quantities, and many report that they do
not feel harm thereby. A number of scientists seem to agree
that within limits alcohol may be a kind of food, although a very
poor food.

On the other hand, we know that although alcohol may techni
cally be considered as a food, it is a very unsatisfactory food and,
as the following statements show, it has an effect on the body
tissues which foods do not have.

Professor Chittenden of Yale College, in discussing the food
problem of alcohol, writes as follows : " It is true that alcohol
in moderate quantities may serve as a food, i.e. it can be oxidized
with the liberation of heat. It may to some extent take the
place of fat and carbohydrates, but it is not a perfect substitute
for them, and for this reason alcohol has an action that can
not be ignored. It reduces liver oxidation. It therefore pre
sents a dangerous side wholly wanting in carbohydrates and fat.
The latter are simply burned up to carbonic acid and water or are
transformed to glycogen and fat, but alcohol, although more easily
oxidized, is at all times liable to obstruct, in a measure at least, the
oxidative processes of the liver and probably of other tissues also,
thereby throwing into the circulation bodies, such as uric acid,
which are harmful to health, a fact which at once tends to draw a
distinct line of demarcation between alcohol and the two non-

1 Alcoholic beverages contain the following proportions of alcohol : beer, from
2 to 5 per cent ; wine, from 10 to 20 per cent ; liquors, from 30 to 70 per cent. Pat
ent medicines frequently contain as high as 60 per cent alcohol. (See page 294.)

FOODS AND DIETARIES 291

nitrogenous foods, fat and carbohydrates. Another matter must
be emphasized, and it is that the form in which alcohol is taken is
of importance. Port wine, for instance, has more influence on the
amount of uric acid secreted than an equivalent amount of alcohol
has in some other form. To conclude : as an adjunct to the ordi
nary daily diet of the healthy man alcohol cannot be considered
as playing the part of a true nonnitrogenous food." Quoted in
American Journal of Inebriety, Winter, 1906.

Effect of Alcohol on Living Matter. If we examine raw white
of egg, we find a protein which closely resembles protoplasm in
its chemical composition ; it is called albumen. Add to a little
albumen in a test tube some 95 per cent alcohol and notice what
happens. As soon as the alcohol touches the albumen the latter
coagulates and becomes hard like boiled white of egg. Shake the
alcohol with the albumen and the entire mass soon becomes a
solid. This is because the alcohol draws the water out of the
albumen. It has been shown that albumen is somewhat like
protoplasm in structure and chemical composition. Strong al
cohol acts in a similar manner on living matter when it is ab
sorbed by the living body cells. It draws water from them and
hardens them. It has a chemical and physical action upon living
matter.

Alcohol a Poison. But alcohol is also in certain quantities a
poison. A commonly accepted definition of a poison is that it is
any substance which, when taken into the body, tends to cause
serious detriment to health, or the death of the organism. That
alcohol may do this is well known by scientists.

It is a matter of common knowledge that alcohol taken in small
quantities does not do any apparent harm. But if we examine the
vital records of life insurance companies, we find a large number of
deaths directly due to alcohol and a still greater number due in
part to its use. In the United States every year there are a third
more deaths from alcoholism and cirrhosis of the liver (a disease
directly caused by alcohol) than there are from typhoid fever. The
poisonous effect is not found in small doses, but it ultimately shows
its harmful effect. Hardening of the arteries, an old-age disease,
is rapidly becoming in this country a disease of the middle aged.

292

FOODS AND DIETARIES

From it there is no escape. It is chiefly caused by the cumulative
effect of alcohol. The diagram following, compiled by two English
life insurance companies that insure moderate drinkers and

COMPANIES

100 EXPECTED HEATHS

Sceptre

Life Insurance
Corar

MODERATE DRINKERS

79.7

1884 M90

ABSTAINERS

United Kingdom
Temperance AND
GeneralProvident

Institution
1866-1909.

MODERATE DRINKERS

ABSTAINERS

Abstainers live longer than moderate drinkers.

abstainers, shows the death rate to be considerably higher among
those who use alcohol.

Dr. Kellogg, the founder of the famous Battle Creek Sanitarium,
points out that strychnine, quinine, and many other drugs are
oxidized in the body but surely cannot be called foods. The
following reasons for not considering alcohol a food are taken
from his writings :

" 1. A habitual user of alcohol has an intense craving for his
accustomed dram. Without it he is entirely unfitted for business.
One never experiences such an insane craving for bread, potatoes,
or any other particular article of food.

"2. By continuous use the body acquires a tolerance for
alcohol. That is, the amount which may be imbibed and the
amount required to produce the characteristic effects first expe
rienced gradually increase until very great quantities are some
times required to satisfy the craving which its habitual use often
produces. This is never the case with true foods. . . . Alcohol
behaves in this regard just as does opium or any other drug. It
has no resemblance to a food.

FOODS AND DIETARIES

293

" 3. When alcohol is withdrawn from a person who has been
accustomed to its daily use, most distressing effects are expe
rienced. . . . Who ever saw a man's hand trembling or his
nervous system unstrung because he could not get a potato or a
piece of cornbread for breakfast? In this respect, also, alcohol
behaves like opium, cocaine, or any other enslaving drug.

" 4. Alcohol lessens the appreciation and the value of brain and
nerve activity, while food reenforces nervous and mental energy.

" 5. Alcohol as a protoplasmic poison lessens muscular power,
whereas food increases energy and endurance.

" 6. Alcohol lessens the power to endure cold. This is true to
such a marked degree that its use by persons accompanying Arctic
expeditions is absolutely prohibited. Food, on the other hand,
increases ability to endure cold. The temperature after taking
food is raised. After taking alcohol, the temperature, as shown by
the thermometer, is lowered.

" 7. Alcohol cannot be stored in the body for future use, whereas
all food substances can be so stored.

" 8. Food burns slowly in the body, as it is required to satisfy
the body's needs. Alcohol is readily oxidized and eliminated, the
same as any other oxidizable drug."

The Use of Tobacco. A well-known authority defines a nar
cotic as a substance " which directly induces sleep, blunts the senses,
and, in large amounts, produces complete
insensibility." Tobacco, opium, chloral,
and cocaine are examples of narcotics.
Tobacco owes its narcotic influence to
a strong poison known as nicotine. Its
use in killing insect parasites on plants
is well known. In experiments with
jellyfish and other lowly organized
animals, the author has found as small
a per cent as one part of nicotine to
one hundred thousand parts of sea
water to be sufficient to profoundly
affect an animal placed within it.
The illustration here given shows the

Experiment (by Davison) to
show how the nicotine in six
cigarettes was sufficient to kill
this fish. The smoke from
the cigarettes was passed
through the water in which
the fish is swimming.

294

FOODS AND DIETARIES

effect of nicotine upon a fish, one of the vertebrate animals.
Nicotine in a pure form is so powerful a poison that two or three
drops would be sufficient to cause the death of a man by its
action upon the nervous system, especially the nerves controlling
the beating of the heart. This action is well known among boys
training for athletic contests. The heart is affected ; boys become
" short-winded " as a result of the action on the heart. It has
been demonstrated that tobacco has, too, an important effect on
muscular development. The stunted appearance of the young
smoker is well known.

Use and Abuse of Drugs. The American people are addicted
to the use of drugs, and especially patent medicines. A glance at

H nnn

IT
uuuullll

The amounts of alcohol in some liquors and in some patent medicines,
a, beer, 5 % ; b, claret, 8 % ; c, champagne, 9 % ; d, whisky, 50 % ;
e, well-known sarsaparilla, 18 % ; /, o, h, much-advertised nerve tonics,
20 %, 21 %, 25 % ; i, another much-advertised sarsaparilla, 27 % ;
j, a well-known tonic, 28 % ; k, I, bitters, 37 %, 44 % alcohol.

the street-car advertisements shows this. Most of the medicines
advertised contain alcohol in greater quantity than beer or wine,
and many of them have opium, morphine, or cocaine in their
composition. Paregoric and laudanum, medicines sometimes given
to young children, are examples of dangerous drugs that contain
opium. Dr. George D. Haggard of Minneapolis has shown

FOODS AND DIETARIES 295

by many analyses that a large number of the so-called " malts/'
" malt extracts," and " tonics," including several of the best known
and most advertised on the market, are simply disguised beers
and, frequently, very poor beers at that. These drugs, in addition
to being harmful, affect the person using them in such a manner
that he soon feels the need for the drug. Thus the drug habit is
formed, a condition which has wrecked thousands of lives. A
number of articles on patent medicines recently appeared in a
leading magazine and have been collected and published under the
title of The Great American Fraud. In this booklet the author
points out a number of different kinds of " cures " and patent
medicines. The most dangerous are those headache or neuralgia
cures containing acstanilid. This drug is a heart depresser and
should not be used without medical advice. Another drug which
is responsible for habit formation is cocaine. This is often found in
catarrh or other cures. Alcohol is the basis of all tonics or
" bracers." Every boy and girl should read this booklet so as to
be forearmed against evils of the sort just described.

REFERENCE READING ON FOODS

Hunter, Laboratory Problems in Civic Biology. American Book Company.

Allen, Civics and Health. Ginn arid Company.

Bulletin 13, American School of Home Economics, Chicago.

Cornell University Reading Course, Buls. 6 and 7, Human Nutrition.

Davison, The Human Body and Health. American Book Company.

Jordan, The Principles of Human Nutrition. The Macmillan Company.

Kebler, L. F., Habit-forming Agents. Farmers' Bulletin 393, U.S. Dept. of Agri.

Lusk, Science and Nutrition. W. B. Saunders Company.

Norton, Foods and Dietetics. American School of Home Economics.

Olscn, Pure Foods. Ginn and Company.

Sharpe, A Laboratory Manual for the Solution of Problems in Biology, pp. 226-240.

American Book Company.

Stiles, Nutritional Physiology. W. B. Saunders Company.
The Great American Fraud. American Medical Association, Chicago.
The Propaganda for Reform in Proprietary Medicines. Am. Medical Association.
Farmers' Bulletin: numbers 23, 34, 42, 85, 93, 121, 128, 132, 142, 182, 249, 295,

298.

Reprint from Yearbook, 1901, Atwater, Dietaries in Public Institutions.
Reprint from Yearbook, 1902, Milner, Cost of Food related to its Nutritive Value.
Experiment Station, Circular 46, Langworthy, Functions and Uses of Food.

XX. DIGESTION AND ABSORPTION

Problems. To determine where digestion takes place by ex
amining :

(a) The functions of glands.

(b) The work done in the mouth.
(#) The work done in the stomach.

(d) The work done in the small intestine.

(e) The function of the liver.

To discover the absorbing apparatus and how it is used.

LABORATORY SUGGESTIONS

Demonstration of food tube of man (manikin). Comparison with food
tube of frog. Drawing (comparative) of food tube and digestive glands
of frog and man.

Demonstration of simple gland. (Microscopic preparation.)

Home experiment and laboratory demonstration. The digestion of
starch by saliva. Conditions favorable and unfavorable.

Demonstration experiment. The digestion of proteins with artificial
gastric juice. Conditions favorable and unfavorable.

Demonstration. An emulsion as seen under the compound microscope.

Demonstration. Emulsification of fats with artificial pancreatic fluid.
Digestion of starch and protein with artificial pancreatic fluid.

Demonstration of "tripe" to show increase of surface of digestive tube.

Laboratory or home exercise. Make a table showing the changes pro
duced upon food substances by each digestive fluid, the reaction (acid or
alkaline) of the fluid, when the fluid acts, and what results from its action.

Purpose of Digestion. We have learned that starch and pro
tein food of plants are formed in the leaves. A plant, however, is
unable to make use of the food in this condition. Before it can
be transported from one part of the plant body to another, it is
changed into a soluble form. In this state it can be passed from
cell to cell by the process of osmosis. Much the same condition
exists in animals. In order that food may be of use to man, it must
be changed into a state that will allow of its passage in a soluble
form through the walls of the alimentary canal, or food tube,

290

DIGESTION AND ABSORPTION

297

Gul

This is done by the enzymes which cause digestion. It will be the
purpose of this chapter to discover where and how digestion takes
place in our own body.

Alimentary Canal. In all vertebrate animals, including
man, food is taken in the mouth and passed through a food tube
in which it is digested. This tube is composed of different por
tions, named, respec
tively, as we pass from
the mouth downward,
the gullet, stomach,
small and large intes
tine, and rectum.

Comparison of Food
Tube of a Frog and
Man. If we compare
the food tube of a dis
sected frog with the
food tube of man (as
shown by a manikin or
chart), we find part for
part they are much the
same. But we notice
that the intestines of
man, both small and
large, are relatively
longer than in the frog.
We also notice in man the body cavity or space in which the
internal organs rest is divided in two parts by a wall of muscle,
the diaphragm, which separates the heart and lungs from the
other internal organs. In the frog no muscular diaphragm exists.
In the frog we can see plainly the silvery transparent mesentery
or double fold of the lining of the body cavity in which the organs
of digestion are suspended. Numerous blood vessels can be found
especially in the walls of the food tube.

Glands. In addition to the alimentary canal proper, we find a
number of digestive glands, varying in size and position, connected
with the canal.

FROG MAN

The digestive tract of the frog and man. Gul, gullet ;
S, stomach; Z/, liver; G, gall bladder; P, pancreas;
Sp, spleen ; SI, small intestine ; LI, large in
testine ; V, appendix; A, anus.

298

DIGESTION AND ABSORPTION

What a Gland Does. Enzymes. In man there are the saliva
gland of the mouth, the gastric glands of the stomach, the pancreas
and liver, the two latter connected with the small intestine, and the
intestinal glands in the walls of the intestine. Besides glands which
aid in digestion there are several others of which we will speak
later. As we have already learned, a gland is a collection of cells

which takes up material

/ood tube from within the body and

manufactures from it some
thing which is later poured
out as a secretion. An
example of a gland in plants
is found in the nectar-
secreting cells of a flower.

Certain substances,
called enzymes, formed by
glands cause the digestion
of food. The enzymes
secreted by the cells of the
glands and poured out into
the food tube act upon
insoluble foods so as to
change them to a soluble
form. They are the prod
uct of the activity of the
cell, although they are not
themselves alive. We do
not know much about
enzymes themselves, but
we can observe what they

do. Some enzymes render soluble different foods, others work
in the blood, still others probably act within any cell of the body
as an aid to oxidation, when work is done. Enzymes are very
sensitive to changes in temperature and to the degree of acidity or
alkalinity l of the material in which they act. We will find that
the enzymes found in glands in the mouth will not act long in the

1 The teacher should explain the meaning of these terms.

Diagram of a gland. i, the common tube
which carries off the secretions formed in
the cells lining the cavity c ; a, arteries
carrying blood to the glands ; v, veins
taking blood away from the glands.

DIGESTION AND ABSORPTION 299

stomach because of the change from an alkaline surrounding in the
mouth to that of an acid in the stomach. Enzymes seem to be
able to work indefinitely, providing the surroundings are favorable.
A small amount of digestive fluid, if it had long enough to work,
could therefore digest an indefinite amount of food.

Gland Structure. The entire inner surface of the food tube
is covered with a soft lining of mucous membrane. This is always
moist because certain cells, called mucus cells, empty out their
contents into the food tube, thus lubricating its inner surface.
When a large number of cells which have the power to secrete
fluids are collected together, the surface of the food tube may be
come indented at this point to form a pitlike gland. Often such
depressions are branched, thus giving a greater secreting surface,
as is seen in the figure on page 298. The cells of the gland are
always supplied with blood vessels and nerves, for the secretions
of the glands are under the control of the nervous system.

How a Gland Secretes. We must therefore imagine that as the
blood goes to the cells of a gland it there loses some substances
which the gland cells take out and make over into the particular
enzyme that they are called upon to manufacture. Under certain
conditions, such as the sight or smell of food, or even the desire
for it, the activity of the gland is stimulated. It then pours out
its secretion containing the digestive enzyme. Thus a gland does
its work.

Salivary Glands. We are all familiar with the substance
called saliva which acts as a lubricant in the mouth. Saliva is
manufactured in the cells of three pairs of glands which empty
into the mouth, and which are called, according to their position,
the parotid (beside the ear), the submaxillary (under the jawbone),
and the sublingual (under the tongue).

Digestion of Starch. If we collect some saliva in a test tube,
add to it a little starch paste, place the tube containing the mixture
for a few minutes in tepid water, and then test with Fehling's
solution, we shall find grape sugar present. Careful tests of the
starch paste and of the saliva made separately will usually show
no grape sugar in either.

If another test be made for grape sugar, in a test tube containing

300

DIGESTION AND ABSORPTION

starch paste, saliva, and a few
drops of any weak acid, the starch
will be found not to have changed.
The digestion or change of starch
to grape sugar is caused by the
presence in the saliva of an enzyme,
or digestive ferment. You will re
member that starch in the grow
ing corn grain was changed to
grape sugar by an enzyme called
diastase. Here a similar action is
caused by an enzyme called ptyalin.

Experiment showing non-osmosis of This ferment acts only in an alka-
starch in tube A, and osmosis of line medium at about the tempera-

sugar in tube B. Q th

Mouth Cavity in Man.
In our study of a frog we
find that the mouth cavity
has two unpaired and four
paired tubes leading from
it. These are (a) the gullet
or food tube, (b) the wind
pipe (in the frog opening
through the glottis), (c) the
paired nostril holes (pos
terior nares), (d) the paired
Eustachian tubes, leading to
the car. All of these open
ings are found in man.

In man the mouth cavity,
and all internal surfaces of
the food tube, are lined

With a muCOUS membrane. T he mouth cavity of man. e,

The mucus secreted from tube; h P> hard palate; 8 p, sott paiate;

ut, upper teeth ; be, buccal cavity ; k, lower

gland cells in this lining
makes a slippery surface so

teeth ; /, tongue ; ph, pharynx ; ep, epiglot
tis ; Ix, voice box ; oe, gullet ; tr, trachea.

DIGESTION AND ABSORPTION

301

that the food may slip down easily. The roof of the mouth is
formed in front by a plate of bone called the hard palate, and a
softer continuation to the back of the mouth, the soft palate. These
separate the nose cavity from that of the mouth proper. The part
of the space back of the soft palate is called the pharynx, or throat
cavity. From the pharynx lead off the gullet and windpipe,
the former back of the latter. The lower part of the mouth
cavity is occupied by a muscular tongue. Examination of its
surface with a looking-glass shows it to be almost covered in places
by tiny projections called papilla?. These papillae contain organs
known as taste buds, the sensory endings of which determine the
taste of substances. The tongue is used in moving food about in
the mouth, and in
starting it on its way
to the gullet; it also
plays an important
part in speaking.

The Teeth. In
man the teeth, unlike
those of the frog, are.
used in the mechanical
preparation of the food
for digestion . Instead
of holding prey, they
crush, grind, or tear
food so that more sur
face may be given for
the action of the diges
tive fluids. The teeth

I. Teeth of the upper jaw, from below. 1, 2, in-

Ol man are divided, ac- cisors ; 3, canine ; 4, 5, premolars ; 6, 7, 8, molars.
COrding to their func- II- longitudinal section of a tooth. E, enamel;

D, dentine ; C, cement ; P, pulp cavity.

tions, into four groups.

In the center of both the upper and lower jaw in front are found
eight teeth with chisel-like edges, four in each jaw; these are
the incisors, or cutting teeth. Next is found a single tooth on
each side (four in all) ; these have rather sharp points and are
called the canines. Then come two teeth on each side, eight in

302 DIGESTION AND ABSORPTION

all, called premolars. Lastly, the flat-top molars, or grinding teetn,
of which there are six in each jaw. Food is caught between
irregular projections on the surface of the molars and crushed
to a pulpy mass.

Hygiene of the Mouth. Food should simply be chewed and rel
ished, with no thought of swallowing. There should be no more ef
fort to prevent than to force swallowing. It will be found that if you
attend only to the agreeable task of extracting the flavors of your
food, Nature will take care of the swallowing, and this will become,
like breathing, involuntary. The instinct by which most people
eat is perverted through the " hurry habit " and the use of abnor
mal foods. Thorough mastication takes time, and therefore one
must not feel hurried at meals if the best results are to be secured.
The stopping point for eating should be at the earliest moment after
one is really satisfied.

Care of the Teeth. It has been recently found that fruit acids
are very beneficial to the teeth. Vinegar diluted to about half
strength with water makes an excellent dental wash. Clean your
teeth carefully each morning and before going to bed. Use dental
silk after meals. We must remember that the bacteria which
cause decay of the teeth are washed down into the stomach and
may do even more harm there than in the mouth.

How Food is Swallowed. After food has been chewed and
mixed with saliva, it is rolled into little balls and pushed by the
tongue into such position that the muscles of the throat cavity
may seize it and force it downward. Food, in order to reach the
gullet from the mouth cavity, must pass over the opening into
the windpipe. When food is in the course of being swallowed,
the upper part of this tube forms a trapdoor over the opening.
When this trapdoor is not closed, and food " goes down the wrong
way," we choke, and the food is expelled by coughing.

The Gullet, or Esophagus. Like the rest of the food tube
the gullet is lined by soft and moist mucous membrane. The
wall is made up of two sets of muscles, the inside ones running
around the tube ; the outer layer of muscle taking a longitudinal
course. After food leaves the mouth cavity, it gets beyond our
direct control, and the muscles of the gullet, stimulated to activity

DIGESTION AND ABSORPTION

303

by the presence of food in the tube, push the food down to the
stomach by a series of contractions until it reaches the stomach.
These wavelike movements (called peristaltic movements) are
characteristic of other parts of tho food tube, food being pushed
along in the stomach and
the small intestine by a
series of slow-moving mus
cular waves. Peristaltic
movement is caused by

Peristaltic waves on the gullet of man.
(A bolus means little ball.)

fcoZus of food.

muscles which are not

under voluntary nervous

control, although anger, fear, or other unpleasant emotions have

the effect of slowing them up or even stopping them entirely.

Stomach of Man. The stomach is a pear-shaped organ
capable of holding about three pints. The end opposite to the
gullet, which empties into the small intestine, is provided with a
ring of muscle forming a valve called the pylorus. There is also
another ring of muscle guarding the entrance to the stomach.

Gastric Glands. If we open the stomach of the frog, and
remove its contents by carefully washing, its wall is seen to be
thrown into folds internally. Between the folds in the stomach of
man, as well as in the frog, are located a number of tiny pits.
These form the mouths of the gastric glands, which pour into the
stomach a secretion known as the gastric juice. The gastric glands
are little tubes, the lining of which secretes the fluid. When we
think of or see appetizing food, this secretion is given out in con
siderable quantity. The stomach, like the mouth, " waters "
at the sight of food. Gastric juice is slightly acid in its chemical
reaction, containing about .2 per cent free hydrochloric acid. It also
contains two very important enzymes, one called pepsin, and an
other less important one called rennin.

Action of Gastric Juice. If protein is treated with artificial
gastric juice at the temperature of the body, it will be found to
become swollen and then gradually to change to a substance
which is soluble in water. This is like the action of the gastric
juice upon proteins in the stomach.

The other enzyme of gastric juice, called rennin, curdles or coag-

304

DIGESTION AND ABSORPTION

ulates a protein found in milk ; after the milk is curdled, the
pepsin is able to act upon it. " Junket" tablets, which contain
rennin, are used in the kitchen to cause this
change.

The hydrochloric acid found in the gastric
juice acts upon lime and some other salts
taken into the stomach with food, changing
them so that they may pass into the blood
and eventually form the mineral part of bone
or other tissue. The acid also has a decided
antiseptic influence in preventing growth of
bacteria which cause decay, and some of which
might cause disease.

Movement of Walls of Stomach. The stomach
walls, provided with three layers of muscle which
run in an oblique, circular, and longitudinal direc
tion (taken from the inside outward), are well
fitted for the constant churning of the food in
A peptic gland, from the t h at organ> Here, as elsewhere in the digestive
stomach, very much , ,. .

magnified. A, central tract, the muscles are involuntary, muscular action

or chief cell, which being under the control of the so-called sympathetic

Food material in the stomach

makes pepsin ;,bor- nervous sys tem.

der cells, which make .

acid. (From Miller's makes several complete circuits during the process

Histology.) of digestion in that organ. Contrary to common

belief, the greatest amount of food is digested

after it leaves the stomach. But this organ keeps the food in it in
almost constant motion for a considerable time, a meal of meat and
vegetables remaining in the stomach for three or four hours. While
movement is taking place, the gastric juice acts upon proteins, softening
them, while the constant churning movement tends to separate the bits
of food into finer particles. Ultimately the semifluid food, much of it still
undigested, is allowed to pass in small amounts through the pyloric valve,
into the small intestine. This is allowed by the relaxation of the ringlike
muscles of the pylorus.

Experiments on Digestion in the Stomach. Some very inter
esting experiments have recently been made by Professor Cannon
of Harvard with reference to movements of the stomach contents.
Cats were fed with material having in it bismuth, a harmless

DIGESTION AND ABSORPTION 305

chemical that would be visible under the X-ray. It was found
that shortly after food reached the stomach a series of waves began
which sent the food toward the pyloric end of the stomach. If
the cat was feeling happy and well, these contractions continued
regularly, but if the cat was cross or bad tempered, the movements
would stop. This shows the importance of cheerfulness at meals.
Other experiments showed that food which was churned into a
soft mass was only permitted to leave the stomach when it became
thoroughly permeated by the gastric juice. It is the acid in
the partly digested food that causes the stomach valve to open and
allow its contents to escape little by little into the small intestine.

The partly digested food in the small intestine almost imme
diately comes in contact with fluids from two glands, the liver and
pancreas. We shall first consider the function of the pancreas.

Position and Structure of the Pancreas. The most important
digestive gland in the human body is the pancreas. The gland
is a rather diffuse structure ; its duct empties by a common opening
with the bile duct into the small intestine, a short distance below
the pylorus. In internal structure, the pancreas resembles the
salivary glands.

Work done by the Pancreas. Starch paste added to artificial
pancreatic fluid and kept at blood heat is soon changed to sugar.
Protein, under the same conditions, is changed to a peptone.

Appearance of milk under the microscope, showing the natural grouping of
the fat globules. In the circle a single group is highly magnified.
Milk is one form of an emulsion. (S. M. Babcock, Wis. Bui. No. 61.)
HUNTER, CIV. BI. 20

30G DIGESTION AND ABSORPTION

Fats, which so far have been unchanged except to be melted by the
heat of the body, are changed by the action of the pancreas into
a form which can pass through the walls of the food tube. If we
test pancreatic fluid, we find it strongly alkaline in its reaction.
If two test tubes, one containing olive oil and water, the other
olive oil and a weak solution of caustic soda, an alkali, be shaken
violently and then allowed to stand, the oil and water will quickly
separate, while the oil, caustic soda, and water will remain for
some time in a milky emulsion. If this emulsion be examined
under the microscope, it will be found to be made of millions of
little droplets of fat, floating in the liquid. The presence of the
caustic soda helped the forming of the emulsion. Pancreatic
fluid similarly emulsifies fats and changes them into soft soaps and
fatty acids. Fat in this form may be absorbed. The process of
this transformation is not well understood.

Conditions under which the Pancreas does its Work. The
secretion from this gland seems to be influenced by the overflow of
acid material from the stomach. This acid, on striking the lining
of the small intestine, causes the formation in its walls of a sub
stance known as secretin. This secretin reaches the blood and
seems to stimulate all the glands pouring fluid into the intestine
to do more work. A pint or more of pancreatic fluid is secreted
every day.

The Intestinal Fluid. Three different pancreatic enzymes do
the work of digestion, one acting on starch, another on protein, and
a third on fats. It has been found that some of these enzymes will
not do their work unless aided by the intestinal fluid, a secretion
formed in glands in the walls of the small intestine. This fluid,
though not much is known about it, is believed to play an important
part in the digestion of all kinds of foods left undigested in the
small intestine.

Liver. The liver is the largest gland in the body. In man, it
hangs just below the diaphragm, a little to the right side of the
body. During life, its color is deep red. It is divided into three
lobes, between two of which is found the gall bladder, a thin-walled
sac which holds the bile, a secretion of the liver. Bile is a strongly
alkalino fluid of greenish color. It reaches the intestine through

DIGESTION AND ABSORPTION

307

the same opening as the pancreatic fluid. Almost one quart of
bile is passed daily into the digestive canal. The color of bile is
due to certain waste substances which come from the destruction
of worn-out red corpuscles of the blood. This destruction takes
place in the liver.

Functions of Bile. The action of bile is not very well known.
It has the very important faculty of aiding the pancreatic fluid in
digestion, though alone it
has slight if any digestive
power. Certain substances
in the bile aid especially in
the absorption of fats.
Bile seems to be mostly a
waste product from the
blood and as such inci
dentally serves to keep the
contents of the intestine in
a more or less soft condi
tion, thus preventing ex
treme constipation.

The Liver a Storehouse.
- Perhaps the most impor
tant function of the liver is
the formation within it of a
material called glycogen, or Diagram of a bit of the wall of the small in-
animal starch. The liver testine ' greatly ma s nified -
is supplied by blood from
two sources. The greater
amount of blood received
by the liver comes directly

from the walls of the stomach and intestine to this organ. It
normally contains about one fifth of all the blood in the body.
This blood is very rich in food materials, and from it the cells of
the liver take out sugars to form glycogen. 1 Glycogen is stored
in the liver until such a time as a food is needed that can be quickly

a, mouths of
intestinal glands; b, villus cut lengthwise
to show blood vessels and lacteal (in center) ;
e, lacteal sending branches to other villi;
i, intestinal glands ; ra, artery ; v, vein ;
I, t, muscular coats of intestine wall.

1 It is known that glycogen may be formed in the body from protein, and possibly
from fatty foods.

308 DIGESTION AND ABSORPTION

oxidized ; then it is changed to sugar and carried off by the blood
to the tissue which requires it, and there used for this purpose.
Glycogen is also stored in the muscles, where it is oxidized to release
energy when the muscles are exercised.

The Absorption of Digested Food into the Blood. The object
of digestion is to change foods from an insoluble to a soluble form.
This has been seen in the study of the action of the various diges
tive fluids in the body, each of which is seen to aid in dissolving
solid foods, changing them to a fluid, and, in case of the bile,
actually assisting them to pass through the wall of the intestine.
A small amount of digested food may be absorbed by the blood
in the blood vessels of the walls of the stomach. Most of the
absorption, however, takes place through the walls of the small
intestine.

Structure of the Small Intestine. The small intestine in man is a
slender tube nearly twenty feet in length and about one inch in diameter.
If the chief function of the small intestine is that of absorption, we must
look for adaptations which increase the absorbing surface of the tube.
This is gained in part by the inner surface of the tube being thrown into
transverse folds which not only retard the rapidity with which food passes
down the intestine, but also give more absorbing surface. But far more
important for absorption are millions of little projections which cover the
inner surface of the small intestine.

The Villi. So numerous are these projections that the whole
surface presents a velvety appearance. Collectively, these struc
tures are called the villi (singular villus). They form the chief
organs of absorption in the intestine, several thousand being
distributed over every square inch of surface. By means of the
folds and villi the small intestine is estimated to have an absorb
ing surface equal to twice that of the surface of the body. Between
the villi are found the openings of the intestinal glands.

Internal Structure of a Villus. The internal structure of a
villus is best seen in a longitudinal section. We find the outer
wall made up of a thin layer of cells, the epithelial layer. It is
the duty of these cells to absorb the semifluid food from within the
intestine. Underneath these cells lies a network of very tiny blood

DIGESTION AND ABSORPTION

309

vein to
arm

vessels, while inside of these, occupying the core of the villas, are
found spaces which, because of their white appearance after
absorption of fats, have been called lacteals. (See figure, page 207.)
Absorption of Foods. Let us now attempt to find out exactly
how foods are passed from the intestines into the blood. Food
substances in solution may be soaked up as a sponge would take up
water, or they may pass by osmosis into the cells lining the villus.
These cells break down the peptones into
a substance that will pass into and be
come part of the blood. Once within the
villus, the sugars and digested proteins
pass through tiny blood vessels into the
larger vessels comprising the portal cir
culation. These pass through the liver,
where, as we have seen, sugar is taken
from the blood and stored as glycogen.
From the liver, the food within the blood
is sent to the heart, from there is pumped
to the lungs, from there returns to the
heart, and is pumped to the tissues of the
body. A large amount of water and
some salts are also absorbed through the
walls of the stomach and intestine as the
food passes on its course. The fats in
the form of soaps and fatty acids pass
into the space in the center of the villus.
Later they are changed into fats again,
probably in certain groups of gland cells
known as mesenteric glands, and eventually reach the blood by
way of the thoracic duct without passing through the liver.

Large Intestine. The large intestine has somewhat the same struc
ture as the small intestine, except that it lacks the villi and has a greater
diameter. Considerable absorption, however, takes place through its
walls as the mass of food and refuse material is slowly pushed along by
the muscles within its walls.

Vermiform Appendix. At the point where the small intestine widens
to form the large intestine, a baglike pouch is formed. From one side of

310 DIGESTION AND ABSORPTION

this pouch is given off a small tube about four inches long, closed at the
lower end. This tube, the rudiment of what is an important part of the
food tube in the lower vertebrates, is called the vermiform appendix It
has come to have unpleasant notoriety in late years, as the site of serious
inflammation.

Constipation. In the large intestine live millions of bacteria,
some of which make and give off poisonous substances known
as toxins. These substances are easily absorbed through the
walls of the large intestine, and, when they pass into the blood,
cause headaches or sometimes serious trouble. Hence it follows
that the lower bowel should be emptied of this matter as fre
quently as possible, at least once a day. Constipation is one of
the most serious evils the American people have to deal with, and
it is largely brought about by the artificial life which we lead, with
its lack of exercise, fresh air, and sleep. Fruit with meals, espe
cially at breakfast, plenty of water between meals and before
breakfast, exercise, particularly of the abdominal muscles, and
regular habits will all help to correct this evil.

Hygienic Habits of Eating ; the Causes and Prevention of Dys
pepsia. From the contents of the foregoing chapter it is evident
that the object of the process of digestion is to break up solid food
so that it may be absorbed to form part of the blood. Any habits
we may form of thoroughly chewing our food will evidently aid
in this process. Undoubtedly much of the distress known as
dyspepsia is due to too hasty meals with consequent lack of proper
mastication of food. The message of Mr. Horace Fletcher in
bringing before us the need of proper mastication of food and the
attendant evils of overeating is one which we cannot afford to
ignore. It is a good rule to go away from the table feeling a little
hungry. Eating too much overtaxes the digestive organs and pre
vents their working to the best advantage. Still another cause of
dyspepsia is eating when in & fatigued condition. It is always a good
plan to rest a short time before eating, especially after any hard man
ual work. We have seen how great a part unpleasant emotions play
in preventing peristaltic movements of the food tube. Conversely,
pleasant conversation, laughter, and fun will help you to digest your
meal. Eating between meals is condemned by physicians because

DIGESTION AND ABSORPTION

311

it calls the blood to the digestive organs at a time when it should be
more active in other parts of the body.

Effect of Alcohol on Digestion. It is a well-known fact that
alcohol extracts water from tissues with which it is in contact.
This fact works much harm to the interior surface of the food tube,
especially the walls of the stomach, which in the case of a hard
drinker are likely to become irritated and much toughened. In
very small amounts alcohol stimulates the secretion of the sali
vary and gastric glands, and thus appears to aid in digestion.

The following results of experiments on dogs, published in the
American Journal of Physiology, Vol. I, Professor Chittenden of
Yale University gives as " strictly comparable," because " they
were carried out in succession on the same day." They show
that alcohol retards rather than aids in digestion :

NUMBER OF EXPERIMENT

la LB. MEAT WITH WATER

10 LB. MEAT WITH DILUTE
ALCOHOL

XVII 9: 15 A.M.

Digested in 3 hours

XVII 3: 00 P.M.

Digested in 3 : 15 hours

XVIII 8: 30 A.M.

Digested in 2 : 30 hours

XVIII ft 2 : 10 P.M.

Digested in 3 : 00 hours

XIX a. 9 : 00 A.M.

Digested in 2 : 30 hours

XIX 2 : 30 P.M.

Digested in 3 : 00 hours

XX a 9: 15 A.M.

Digested in 2 : 45 hours

XX 2 : 30 P.M.

Digested in 2 : 15 hours

VI a 9: 15 A.M.

Digested in 3 : 45 hours

VI ft 1 : 00 P.M.

Digested in 3 : 15 hours

Average

2 : 42 hours

3:09 hours

As a result of his experiments, Professor Chittenden remarks :
" We believe that the results obtained justify the conclusion that
gastric digestion as a whole is not materially modified by the
introduction of alcoholic fluids with the food. In other words,
the unquestionable acceleration of gastric secretion which follows
the ingestion of alcoholic beverages is, as a rule, counterbalanced
by the inhibitory effect of the alcoholic fluids upon the chemical

312

DIGESTION AND ABSORPTION

process of gastric digestion, with perhaps at times a tendency
towards preponderance of inhibitory action." Others have come
to the same or stronger conclusions as to the undesirable action
of alcohol on digestion, as a result of their own experiments.

Effect of Alcohol on the Liver. The effect of heavy drinking
upon the liver is graphically shown in the following table prepared
by the Scientific Temperance Federation of Boston, Mass. :

10 O 30 40 50 60 70 80 90

Proportion of deaths from disease in a certain area due to alcohol. The black
area shows deaths due to alcohol. 1

" Alcoholic indulgence stands almost if not altogether in the
front rank of the enemies to be combated in the battle for health."
PROFESSOR WILLIAM T. SEDGWICK.

1 Does not include deaths from general alcoholic paralysis or other organic
diseases due to alcohol. Liver cirrhosis due to alcohol conservatively estimated
at 75 per cent of total cases.

XXI. THE BLOOD AND ITS CIRCULATION

Problems. To discover the composition and uses of the dif
ferent parts of the blood.

To find out the means by which the blood is circulated
about the body.

LABORATORY SUGGESTIONS

Demonstration. Structure of blood, fresh frog's blood and human
blood. Drawings.

Demonstration. Clotting of blood.

Demonstration. Use of models to demonstrate that the heart is a force
pump.

Demonstration. Capillary circulation in web of frog's foot or tadpole's
tail. Drawing.

Home or laboratory exercise. On relation of exercise on rate of heart
beat.

Function of the Blood. The chief function of the digestive
tract is to change foods to such form that they can be absorbed
through the walls of the food tube and become part of the blood. 1

If we examine under the microscope a drop of blood taken from
the frog or man, we find it made up of a fluid called plasma and two
kinds of bodies, the so-called red corpuscles and colorless corpuscles,
floating in this plasma.

Composition of Plasma. The plasma of blood is found to be
largely (about 90 per cent) water. It also contains a considerable
amount of protein, some sugar, fat, and mineral material. It is,
then, the medium which holds the fluid food that has been ab
sorbed from within the intestine. This food is pumped to the body
cells where, as work is performed, oxidation takes place and heat
is given off as a form of energy. The almost constant temperature

1 This change is due to the action of certain enzymes upon the nutrients in va
rious foods. But we also find that peptones are changed back again to proteins when
once in the blood. This appears to be due to the reversible action of the enzymes
acting upon them. (See page 307.)

313

314

THE BLOOD AND ITS CIRCULATION

Human blood as seen under the
high power of the compound
microscope ; at the extreme
right is a colorless corpuscle.

of the body is also due to the blood, which brings to the surface of
the body much of the heat given off by oxidation of food in the

muscles and other tissues. When
the blood returns from the tissues
where the food is oxidized, the
plasma brings back with it to the
lungs part of the carbon dioxide
liberated where oxidation has taken
place. Some waste products, to be
spoken of later, are also found in
the plasma.

The Red Blood Corpuscle ; its
Structure and ' Functions. -- The
red corpuscle f 'in the blood of the
frog is a true cell of disklike form, containing a.nucleus. The red
corpuscle of man is made in the red marrow of bones and in
its young stages has a nucleus. In its adult form, however,
it lacks a nucleus. Its form is that of a biconcave disk. So
small and so numerous are these corpuscles _ ihsfa over five
million are found in a cubic centimeter of normal bl^>od. They
make up almost one half the total volume of t/he blood. The
color, which is found to be a dirty yellow wheii separate cor
puscles are viewed under the microscope, is due to a protein
material called haemoglobin. Haemoglobin contains a large amount
of iron. It has the power of uniting very readily with oxygen
whenever that gas is abundant, and, after having absorbed it,
of giving it up to the surrounding media, when oxygen is there
present in smaller amounts than in the corpuscle. This function
of carrying oxygen is the most important function ' of the red
corpuscle, although the red corpuscle also removes part of the
carbon dioxide from the tissues on their return to the limgs. The
taking up of oxygen is accompanied by a change in color of the
mass of corpuscles from a dull red to a bright scarlet.

Clotting of Blood. If fresh beef blood is allowed to stand overnight,
it will be found to have separated into two parts, a dark red, almost solid
dot and a thin, straw-colored liquid called serum. Serum is found to
be made up of about 90 per cent water, 8 per cent protein, 1 per cent

THE BLOOD AND ITS CIRCULATION

315

other organic foods, and 1 per cent mineral substances. In these
respects it very closely resembles the fluid food that is absorbed from
the intestines.

If another jar of fresh beef blood is poured into a pan and briskly
whipped with a bundle of little rods (or with an egg beater), a stringy sub
stance will be found to stick to the rods. This, if washed carefully, is
seen to be almost colorless. Tested with nitric acid and ammonia, it is
found to contain a protein substance which is called fibrin.

Blood plasma, then, is made up of a fluid portion of serum, and
fibrin, which, although in a fluid state in the blood vessels within
the body, coagulates when blood is removed from the blood vessels.
This coagulation aids in making a blood clot. A clot is simply a
mass of fibrin threads with a large number of corpuscles tangled
within. The clotting of blood is of great physiological importance,
for otherwise we might bleed to death even from a small wound.

Blood Plates. In blood within the circulatory system of the
body, the fibrin is held in a fluid state called fibrinogen. An
enzyme, acting upon this fibrinogen, the soluble protein in the
blood, causes it to change to an insoluble form, the fibrin of the
clot. This change seems to be due to the action of minute bodies
in the blood known as blood
plates. Under abnormal
conditions these blood
plates break down, releas
ing some substances which
eventually cause this en
zyme to do its work.

The Colorless Corpuscle ;
Structure and Functions.
A colorless corpuscle is a
cell irregular in outline, the
shape of which is constantly
changing. These corpuscles
are somewhat larger than the red corpuscles, but less numerous,
there being about one colorless corpuscle to every three hundred
red ones. They have the power of movement, for they are found
not only inside but outside the blood vessels, showing that they

A small artery (^4) breaking up into capillaries
(c) which unite to form a vein (F). Note
at (P) several colorless corpuscles, which are
fighting bacteria at that point.

316

THE BLOOD AND ITS CIRCULATION

have worked their way between the cells that form the walls of
the blood tubes.

A Russian zoologist, Metchnikoff, after studying a number of
simple animals, such as medusae and sponges, found that in such
animals some of the cells lining the inside of the food cavity take
up or engulf minute bits of food. Later, this food is changed into
the protoplasm of the cell. Metchnikoff believed that the colorless
corpuscles ot the blood have somewhat the same function. This

he later proved to be true. Like the
amceba, they feed by engulfing their
prey. This fact has a very important
bearing on the relation of colorless cor
puscles to certain diseases caused by
bacteria within the body. If, for ex
ample, a cut becomes infected by bac
teria, inflammation may set in. Color
less corpuscles at once surround the
spot and attack the bacteria which
cause the inflammation. If the bac
teria are few in number, they are quickly
eaten by certain of the colorless cor
puscles, which are known as phagocytes.
If bacteria are present in great quan
tities, they may prevail and kill the
phagocytes by poisoning them. The
dead bodies of the phagocytes thus
killed are found in the pus, or matter, which accumulates in
infected wounds. In such an event, we must come to the aid of
nature by washing the wound with some antiseptic, as weak
carbolic acid or hydrogen peroxide.

Antibodies and their Uses. In case of disease where, for
example, fever is caused by poison given off from bacteria we find
the cells of the body manufacture and pour into the blood a
substance known as an antibody. This substance does not of
necessity kill the harmful germs or even stop their growth. It
does, however, unite with the toxin or poison given off by the
germs and renders it entirely harmless.

THE BLOOD AND ITS CIRCULATION

317

s> Course / Plasma
d^ - * - - -_^- -j~^.

Dis$olved(f
<tj$ Q Nutrient^ s
00-^^^

LYMPH

Function of Lymph. The tissues and organs of the body
are traversed by a network of tubes which carry the blood. Inside
these tubes is the blood proper, consisting of a fluid plasma, the
colorless corpuscles, and the red corpuscles. Outside the blood
tubes, in spaces between the cells which form tissues, is found
another fluid, which is in chemical composition very much like
plasma of the blood. This is the lymph. It is, in fact, fluid food
in which some colorless amoeboid corpuscles are found. Blood
gives up its food material to the lymph. This it does by passing it
through the walls of the
capillaries. The food is in
turn given up to the tissue
cells, which are bathed by
the lymph .

Some of the amoeboid
corpuscles from the blood
make their way between
the cells forming the walls
of the capillaries. Lymph,
then, is practically blood
plasma plus some colorless
corpuscles. It acts as the
medium of exchange between
the blood proper and the cells
in the tissues of the body.
By means of the food sup
ply thus brought, the cells _,

* J The exchange between blood and the cells of

of the body are able to grow, the body.

the fluid food being changed

to the protoplasm of the cells. By means of the oxygen passed

over by the lymph, oxidation may take place within the cells.

Lymph not only gives food to the cells of the body, but also takes

away carbon dioxide and other waste materials, which are ultimately

passed out of the body by means of the lungs, skin, and kidneys.

Internal Secretions. In addition to all the functions given
above, the blood has recently been shown to carry the secretions of
a number of glands through which it passes, although these glands

318 THE BLOOD AND ITS CIRCULATION

have no ducts to carry off their secretions. These internal secre
tions seem absolutely necessary for the health of the body.
Several glands, the thyroid, adrenal bodies, the testes, and ovaries,
as well as the pancreas, give off these remarkable substances.

The Amount of Blood and its Distribution. Blood forms, by weight,
about one sixteenth of the body. This would be about four quarts to a
body weight of 130 pounds. Normally, about one half of the blood of
the body is found in or near the organs lying in the body cavity below
the diaphragm, about one fourth in the muscles, and the rest in the
head, heart, lungs, large arteries, and veins.

Blood Temperature. The temperature of blood in the human body
is normally about 98.6 Fahrenheit when tested under the tongue by a
thermometer, although the temperature drops almost two degrees after
we have gone to sleep at night. It is highest about 5 P.M. and lowest
about 4 A.M. In fevers, the temperature of the body sometimes rises to
107 ; but unless this temperature is soon reduced, death follows. Any
considerable drop in temperature below the normal also means death.
Body heat results from the oxidation of food, and the circulation of blood
keeps the temperature nearly uniform in all parts of the body.

Cold-blooded Animals. In animals which are called cold-blooded,
the blood has no fixed temperature, but varies with the temperature of
the medium in which the animal lives. Frogs, in the summer, may sit
for hours in water with a temperature of almost 100. In winter, they
often endure freezing so that the blood and lymph within the spaces
under the loose skin are frozen into ice crystals. This change in body
temperature is evidently an adaptation to the mode of life.

Circulation of the Blood in Man. The blood is the carrying
agent of the body. Like a railroad or express company, it takes
materials from one part of the human organism to another. This
it does by means of the organs of circulation, the heart and
blood vessels. These blood vessels are called arteries where they
carry blood away from the heart, veins where they bring blood back
to the heart, and capillaries where they connect the larger blood
vessels. The organs of circulation thus form a system of con
nected tubes through which the blood flows.

The Heart ; Position, Size, Protection. The heart is a cone-
shaped muscular organ about the size of a man's fist. It is
located immediately above the diaphragm, and lies so that the

THE BLOOD AND ITS CIRCULATION 310

muscular apex, which points downward, moves while beating
against the fifth and sixth ribs, just a little to the left of the
midline of the body. This fact gives rise to the notion that the
heart is on the left side of the body. The heart is surrounded
by a loose membranous bag called the pericardium, the inner
lining of which secretes a fluid in
which the heart lies. When, for any
reason, the pericardial fluid is not
secreted, inflammation arises in that
region.

Internal Structure of Heart. If
we should cut open the heart of a
mammal down the midline, we could
divide it into a right and a left side,
each of which would have no internal
connection with the other. Each side
is made up of an upper thin-walled
portion with a rather large internal

Cavity, the auricle, which Opens into Diagram showing the front half of

a lower smaller portion with heavy the heart cut awa ^ : a - aorta;

/, arteries to the lungs; la, left
muscular walls, the ventricle. Com- auricle; lv, left ventricle ; m.tri-

munication between auricles and cuspid valve open; n, bicuspid

. . Tin or mitral valve closed ; p and r,

ventricles is guarded by little flaps veins from the lungs; m, right
or valves. The auricles receive blood auricle; , right ventricle;

. . v, vena cava. Arrows show di-

trom the veins. The ventricles pump rection of circulation,
the blood into the arteries.

The Heart in Action. The heart is constructed on the same
plan as a force pump, the valves preventing the reflux of blood into
the auricle when it is forced out of the ventricle. Blood enters
the auricles from the veins because the muscles of that part of
the heart relax; this allows the space within the auricles to fill.
Almost immediately the muscles of the ventricles relax, thus allow
ing blood to pass into the chambers within the ventricles. Then,
after a short pause, during which time the muscles of the heart are
resting, a wave of muscular contraction begins in the auricles and
ends in the ventricles, with a sudden strong contraction which
forces the blood out into the arteries. Blood is kept on its course

320

THE BLOOD AND ITS CIRCULATION

by the valves, which act in the same manner as do the valves in a
pump. The blood is thus made to pass into the arteries upon

the contraction of the
ventricle walls.

The Course of the
Blood in the Body.
Although the two sides
of the heart are separate
and distinct from each
other, yet every drop
of blood that passes
through the right heart
likewise passes later
through the left heart.
There are two distinct
systems of circulation
in the body. The pul
monary circulation takes
the blood through the
right auricle and ven
tricle, to the lungs, and passes it back to the left auricle. This
is a relatively short circulation, the blood receiving in the lungs
its supply of oxygen, and there giving up some of its carbon
dioxide. The greater circulation is known as the systemic circu
lation; in this system, the blood leaves the left ventricle through
the great dorsal aorta. A large part of the blood passes directly
to the muscles ; some of it goes to the nervous system, kidneys,
skin, and other organs of the body. It gives up its supply of
food and oxygen in these tissues, receives the waste products of
oxidation while passing through the capillaries, and returns to

The heart is a force pump ; prove it from these
diagrams.

I. Circulation in a fish. G, gills ; (7, capillaries of the body. Notice the two-

chambered heart.

II. The circulation in a frog. L, the lungs ; C, the capillaries. Notice the heart
has three chambers. What is the condition of blood leaving the ventricle to
go to the cells of the body ?

The circulation in man. H, head ; A, arms ; L, lungs ; S, stomach ; Li, liver ;
K, kidney: S.I., small intestine; L.I., large intestine; Le, legs; 1, right
auricle ; 2, right ventricle ; 3, left ventricle ; 4. left auricle ; 5, dorsal aorta ; 6,
vein to lungs.

III.

THE BLOOD AND ITS CIRCULATION

321

HUNTER, CIV. Bl. 21

322

THE BLOOD AND ITS CIRCULATION

the right auricle through two large vessels known as the vence
cavce. It requires only from twenty to thirty seconds for the
blood to make the complete circulation from the ventricle back
again to the starting point. This means that the entire volume of
blood in the human body passes three or four thousand times a
day through the various organs of the body. 1

Portal Circulation. Some of the blood, on its way back to the heart,
passes to the walls of the food tube and to its glands. From there it is sent
with its load of absorbed food to the liver. Here the vein which carries
the blood (called the portal vein) breaks up into capillaries around the
cells of the liver, when it gives up sugar to be stored as glycogen. From
the liver, blood passes directly to the right auricle. The portal circula
tion, as it is called, is the only part of the circulation where the blood
passes through two sets of capillaries on its way from auricle to auricle.

Circulation in the Web of a Frog's Foot. If the web of the foot
of a live frog or the tail of a tadpole is examined under the com-

--...6

Capillary circulation in the web of a frog's foot, as seen under the compound micro
scope, a, 6, small veins ; c, pigment cells in the skin ; d, capillaries in which
the oval corpuscles are seen to follow one another in single series.

1 See Hough and Sedgwick, The Human Mechanism, page 136.

THE BLOOD AND ITS CIRCULATION 323

pound microscope, a network of blood vessels will be seen. In
some of the larger vessels the corpuscles are moving rapidly and
in spurts ; these are arteries. The arteries lead into smaller vessels
hardly greater in diameter than the width of a single corpuscle.
This network of capillaries may be followed into larger veins in
which the blood moves regularly. This illustrates the condition
in any tissue of man where the arteries break up into capillaries,
and these in turn unite to form veins.

Structure of the Arteries. A distinct difference in structure
exists between the arteries and the veins in the human body. The
arteries, because of the greater strain received from the blood which
is pumped from the heart, have thicker muscular walls, and in
addition are very elastic.

Cause of the Pulse. The pulse, which can easily be detected by press
ing the large artery in the wrist or the small one in front of and above the
external ear, is caused by the gushing of blood through the arteries after
each pulsation of the heart. As the large arteries pass away from the
heart, the diameter of each individual artery becomes smaller. At the
very end of their course, these arteries are so small as to be almost mi
croscopic in size and are very numerous. There are so many that if
they were placed together, side by side, their united diameter would be
much greater than the diameter of the large artery (aorta) which passes
blood from the left side of the heart. This fact is of very great impor
tance, for the force of the blood as it gushes through the arteries becomes
very much less when it reaches the smaller vessels. This gushing move
ment is quite lost when the capillaries are reached, first, because there is
so much more space for the blood to fill, and second, because there is
considerable friction caused by the very tiny diameter of the capillaries.

Capillaries. The capillaries form a network of minute tubes
everywhere in the body, but especially near the surface and in the
lungs. It is through their walls that the food and oxygen pass
to the tissues, and carbon dioxide is given up to the plasma. They
form the connection that completes the system of circulation of
blood in the body.

Function and Structure of the Veins. If the arteries are supply
pipes which convey fluid food to the tissues, then the veins may
be likened to drain pipes which carry away waste material from the

324

THE BLOOD AND ITS CIRCULATION

tissues, Extremely numerous in the extremities and in the muscles
and among other tissues of the body, they, like the branches of a

tree, become larger and unite with each other as they

approach the heart.

If the wall of a vein is carefully examined, it will be
found to be neither so thick nor so tough as an artery wall.
When empty, a vein collapses ; the wall of an artery holds
its shape. If you hold your hand downward for a little
time and then examine it, you will find that the veins,
which are relatively much nearer the surface than are the
arteries, appear to be very much knotted. This appear
ance is due to the presence of tiny valves within. These
valves open in the direction of the blood current, but
would close if the direction of the blood flow should be
reversed (as in case a deep cut severed a vein). As the
pressure of blood in the veins is much less than in the
arteries, the valves thus aid in keeping the flow of blood
in the veins toward the heart. The higher pressure in
arteries and the suction in the veins (caused by the enlarge
ment of the chest cavity in breathing) are the chief factors

vein* "NO- wmc h cause a steady flow of blood through the veins in

tice the thin the body.

walls of the ,, , , , ,.

ve i n . Lymph Vessels. Ihe lymph is collected irom

the various tissues of the body by means of a number
of very thin-walled tubes, which arc at first very tiny, but after
repeated connection with other tubes ultimately unite to form
large ducts. These lymph ducts are provided, like the veins,
with valves. The pressure of the blood within the blood vessels
forces continually more plasma into the lymph ; thus a slow
current is maintained. On its course the lymph passes through
many collections of gland cells, the lymph glands. In these glands
some impurities appear to be removed and colorless corpuscles made.
The lymph ultimately passes into a large tube, the thoracic duct,
which flows upward near the ventral side of the spinal column, and
empties into the large subclavian vein in the left side of the neck.
Another smaller lymph duct enters the right subclavian vein.

The Lacteals. We have already found that part of the digested
food (chiefly carbohydrates, proteins, salts, and water) is absorbed

THE BLOOD AND ITS CIRCULATION

325

directly into the blood through the walls of the villi and carried to

the liver. Fat, however, is passed into the spaces in the central

part of the villi, and from there into other spaces between the

tissues, known as the lacteals.

The lacteals carry the fats into

the blood by way of the thoracic

duct. The lacteals and lymph

vessels have in part the same

course. It will be thus seen

that lymph at different parts of

its course would have a very

different composition.

The Nervous Control of the
Heart and Blood Vessels. Al
though the muscles of the heart
contract and relax without our be
ing able to stop them or force them
to go faster, yet in cases of sudden
fright, or after a sudden blow, the
heart may stop beating for a short
interval. This shows that the heart
is under the control of the nervous
system. Two sets of nerve fibers,

both of which are connected with the central nervous system, pass to
the heart. One set of fibers accelerates, the other slows or inhibits, the
heart beat. The arteries and veins are also under the control of the
sympathetic nervous system. This allows of a change in the diameter
of the blood vessels. Thus, blushing is due to a sudden rush of blood to
the surface of the body caused by an expansion of the blood vessels at
the surface. The blood vessels of the body are always full of blood. This
results from an automatic regulation of the diameter of the blood tubes by
a part of the nervous system called the vasomotor nerves. These nerves
act upon the muscles in the walls of the blood vessels. In this way, each
vessel adapts itself to the amount of blood in it at a given time. After
a hearty meal, a large supply of blood is needed in the walls of the stomach
and intestines. At this time, the arteries going to this region are dilated
so as to receive an extra supply. When the brain performs hard work,
blood is supplied in the same manner to that region. Hence, one should
not study or do mental work immediately after a hearty meal, for blood

The lymph vessels; the dark spots are
lymph glands: lac, lacteals; re, tho
racic duct.

326

THE BLOOD AND ITS CIRCULATION

will be drawn away to the brain, leaving the digestive tract with an in
sufficient supply. Indigestion may follow as a result.

The Effect of Exercise on the Circulation. It is a fact familiar
to all that the heart beats more violently and quickly when we are
doing hard work than when we are resting. Count your own pulse
when sitting quietly, and then again after some brisk exercise in the
gymnasium. Exercise in moderation is of undoubted value, be
cause it sends the increased amount of blood to such parts of the
body where increased oxidation has been taking place as the result
of the exercise. The best forms of exercise are those which give
as many muscles as possible work walking, out-of-door sports,
any exercise that is not violent. Exercise should not be attempted
immediately .after eating, as this causes a withdrawal of blood from
the digestive tract to the muscles of the body. Neither should
exercise be continued after becoming tired, as poisons are then
formed in the muscles, which cause the feeling we call fatigue.
Remember that extra work given to the heart by extreme exercise
may injure it, causing possible trouble with the valves.

Treatment of Cuts and
Bruises. Blood which oozes
slowly from a cut will usually
stop flowing by the natural
means of the formation of a
clot. A cut or bruise should,
however, be washed in a weak
solution of carbolic acid or
some other antiseptic in order
to prevent bacteria from ob
taining a foothold on the ex
posed flesh. If blood, issuing
from a wound, gushes in dis
tinct pulsations, then we know
that an artery has been sev
ered. To prevent the flow of
blood, a tight bandage known

Stopping flow of blood from an artery by fnurnimjpf mimt hp fipH

applying a tight bandage (ligature) be- as <OUrniquei

tween the cut and the heart. between the cut and the heart.

THE BLOOD AND ITS CIRCULATION 327

A handkerchief with a knot placed over the artery may stop
bleeding if the cut is on one of the limbs. If this does not serve,
then insert a stick in the handkerchief and twist it so as to make
the pressure around the limb still greater. Thus we may close
the artery until the doctor is called, who may sew up the injured
blood vessel.

The Effect of Alcohol upon the Blood. It has recently been
discovered that alcohol has an extremely injurious effect upon the
colorless corpuscles of the blood, lowering their ability to fight
disease germs to a marked degree. This is well seen in a compari
son of deaths from certain infectious diseases in drinkers and
abstainers, the percentage of mortality being much greater in the
former.

Dr. T. Alexander MacNichol, in a recent address, said :

" Massart and Bordet, Metchnikoff and Sims Woodhead, have
proved that alcohol, even in very dilute solution, prevents the
white blood corpuscles from attacking invading germs, thus de
priving the system of the cooperation of these important defenders,
and reducing the powers of resisting disease. The experiments of
Richardson, Harley, Kales, and others have demonstrated the
fact that one to five per cent of alcohol in the blood of the living
human body in a notable degree alters the appearance of the cor
puscular, elements, reduces the oxygen bearing elements, and pre
vents their reoxygenation."

Alcohol weakens Resistance to Disease. In acute illnesses,
grippe, fevers, blood poisoning, etc., substances formed in the
blood termed " antibodies " antagonize the action of bacteria,
facilitating their destruction by the white blood cells and neutral
izing their poisonous influence. In a person with good " resist
ance" this protective machinery, which we do not yet thoroughly
understand, works with beautiful precision, and the patient " gets
well." Experiments by scientific experts have demonstrated that
alcohol restrains the formation of these marvelous antibodies.
Alcohol puts to sleep the sentinels that guard your body from
disease.

The Effect of Alcohol on the Circulation. Alcoholic drinks
affect the very delicate adjustment of the nervous centers control-

328 THE BLOOD AND ITS CIRCULATION

ling the blood vessels and heart. Even very dilute alcohol acts
upon the muscles of the tiny blood vessels ; consequently, more
blood is allowed to enter them, and, as the small vessels are usually
near the surface of the body, the habitual redness seen in the face
of hard drinkers is the ultimate result.

" The first effect of diluted alcohol is to make the heart beat
faster. This fills the small vessels near the surface. A feeling of
warmth is produced which causes the drinker to feel that he was
warmed by the drink. This feeling, however, soon passes away,
and is succeeded by one of chilliness. The body temperature, at
first raised by the rather rapid oxidation of the alcohol, is soon
lowered by the increased radiation from the surface.

" The immediate stimulation to the heart's action soon passes
away and, like other muscles, the muscles of the heart lose power
and contract with less force after having been excited by alcohol."
MACY, Physiology.

Alcohol, when brought to act directly on heart muscle, lessens the
force of the beat. It may even cause changes in the tissues, which
eventually result in the breaking of the walls of a blood vessel or
the plugging of a vessel with a blood clot. This condition may
cause the disease known as apoplexy.

Effects of Tobacco upon the Circulation. " The frequent use of
cigars or cigarettes by the young seriously affects the quality of the
blood. The red blood corpuscles are not fully developed and
charged with their normal supply of life-giving oxygen. This
causes paleness of the skin, often noticed in the face of the young
smoker. Palpitation of the heart is also a common result, fol
lowed by permanent weakness, so that the whole system is
enfeebled, and mental vigor is impaired as well as physical
strength." MACY, Physiology.

XXII. RESPIRATION AND EXCRETION

Problems. ^ study of respiration to find out:

(a) What changes in blood and air take place within the
lungs.

(b) The mechanics of respiration.

A study of ventilation to discover :

(a) The reason for ventilation.

(b) The best method of ventilation.
A study of the organs of excretion.

LABORATORY SUGGESTIONS

Demonstration. Comparison of lungs of frog with those of bird or
mammal.

Experiment. The changes of blood within the lungs.

Experiment. Changes taking place in air in the lungs.

Experiment. The use of the ribs in respiration.

Demonstration experiment. What causes the filling of air sacs of the
lungs ?

Demonstration experiment. What are the best methods of ventilating
a room?

Demonstration. Best methods of dusting and cleaning.

Demonstration. Beef or sheep's kidney to show areas.

Necessity for Respiration. We have seen that plants and
animals need oxygen in order that the life processes may go on.
Food is oxidized to release energy, just as coal is burned to give
heat to run an engine. As a draft of air is required to make fire
under the boiler, so, in the human body, oxygen must be given so
that food in tissues may be oxidized to release energy used in
work. This oxidation takes place in the cells of the body, be they
part of a muscle, a gland, or the brain. Blood, in its circulation
to all parts of the body, is the medium which conveys the oxygen to
that place in the body where it will be used.

329

330

RESPIRATION AND EXCRETION

The Organs of Respiration in Man. We have alluded to
the fact that the lungs are the organs which give oxygen to the
blood and take from it carbon dioxide. The course of the air
passing to the lungs in man is much the same as in the
frog. Air passes through the nose, and into the windpipe. This
cartilaginous tube, the top of which may easily be felt as the
Adam's apple of the throat, divides into two bronchi. The
bronchi within the lungs break up into a great number of smaller
tubes, the bronchial tubes, which divide somewhat like the small

branches of a tree. The
bronchial tubes, indeed all
the air passages, are lined
with ciliated cells. The
cilia of these cells are con
stantly in motion, beating
with a quick stroke toward
the outer end of the tube,
that is, toward the mouth.
Hence any foreign material
will be raised from the
throat first by the action
of the cilia and then by

COUghing or " clearing the

fU, fta f Thp hrnnr>Vii PnH
tnroat.

in very minute air sacs,
little pouches having elastic walls, into which air is taken when
we inspire, or take a deep breath. In the walls of these pouches
are numerous capillaries, the ends of arteries which pass from the
heart into the lung. It is through the very thin walls of the air sacs
that an interchange of gases takes place which results in the blood
giving up part of its load of carbon dioxide, and taking up oxygen in
its place. This exchange appears to be aided by the presence
of an enzyme in the lung tissues. This is another example of
the various kinds of work done by the enzymes of the body.

Changes in the Blood within the Lungs. Blood, after leaving
the lungs, is much brighter red than just before entering them.
The change in color is due to a taking up of oxygen by the hcemo-

Air passages in the human lungs, a, larynx
b, trachea (or windpipe); c, d, bronchi
e, bronchial tubes ; /, cluster of air cells.

RESPIRATION AND EXCRETION

331

.tal

pvumonary

globin of the red corpuscles. Changes taking place in blood are
obviously the reverse of those which take place in air in the
lungs. Every hundred cubic centimeters of blood going into
the lungs contains 8 to 12 c.c.
of oxygen, 45 to 50 c.c. of
carbon dioxide, and 1 to 2 c.c.
of nitrogen. The same amount
of blood passing out of the
lungs contains 20 c.c. of oxy
gen, 38. c.c. of carbon dioxide,
and 1 to 2 c.c. of nitrogen.
The water, of which about
half a pint is given off daily,
is mostly lost from the blood.

Changes in Air in the Lungs.
Air is much warmer after
leaving the lungs than before
it enters them. Breathe on
the bulb of a thermometer to
prove this. Expired air con- Dia ? ram to show what the blood loses and

v gains in one of the air sacs of the lungs.

tains a considerable amount

of moisture, as may be proved by breathing on a (fold polished
surface. This it has taken up in the air sacs of the lungs. The
presence of carbon dioxide in expired air may easily be detected
by the lime water test. Air such as we breathe out of doors con
tains, by volume :

Nitrogen . . . . . . .-> . '. , ... .' . 76.95

Oxygen .....,..,. . . 20.61

Carbon dioxide 03

Argon . ". . . . . . . ... . . . . . ... . 1-00

Water vapor (average) . . . . :./. _. 1.40

Air expired from the lungs contains :
Nitrogen . . .... . ..'. . . .' . . ... . 76.95

Oxygen . . . . < . .-, . . -. . . . . ... -. . . 15.67

Carbon dioxide . . . . ; . . . . . .. . ... , . .-. ..'. 4.38

Water vapor ...... ...-,. V . . . . ._, . . . 2

Argon 1

332

RESPIRATION AND EXCRETION

In other words, there is a loss between 4 and 5 per cent oxygen,
and nearly a corresponding gain in carbon dioxide, in expired air.
There are also some other organic substances present.

Cell Respiration. It has been shown, in the case of very
simple animals, such as the amoeba, that when oxidation takes
place in a cell, work results from this oxidation. The oxygen
taken into the lungs is not used there, but is carried by the blood
to such parts of the body as need oxygen to oxidize food mate
rials in the cells. Since
work is done in the cells
of the body, food and oxy
gen are therefore required.
The quantity of oxygen
used by the body is nearly
dependent on the amount
of work performed. Oxy
gen is constantly taken
from the blood by tissues
in a state of rest and is
used up when the body is
at work. This is suggested
by the fact that in a given

time a man, when working, gives off more oxygen (in carbon
dioxide) than he takes in during that time.

While work is being done certain wastes are formed in the cell.
Carbon dioxide is given off when carbon is burned. But when
proteins are burned, another waste product containing nitrogen
is formed. This must be passed off from the cells, as it is a poison.
Here again the lymph and blood, the common carriers, take the
waste material to points where it may be excreted or passed out of
the body.

The Mechanics of Respiration. The Pleura. The lungs are
covered with a thin elastic membrane, the pleura. This forms a
bag in which the lungs are hung. Between the walls of the bag
and the lungs is a space filled with lymph. By this means
the lungs are prevented from rubbing against the walls of the
chest.

The respiration of cells.

RESPIRATION AND EXCRETION

333

IS! rl

diaphragm

Breathing. In every
full breath there are two
distinct movements, in
spiration (taking air in)
and expiration (forcing
air out) . In man an in
spiration is produced by
the contraction of the
muscles between the
ribs, together with the
contraction of the . dia
phragm, the muscular

will inst below tho hpart The chest cavit y () at the time of a ful1 breath ;
Wail JUSt heart (fo) aftef an expiration Explain how the

and lungs ; this results cavity for lungs is made larger.

in pulling down the dia
phragm and pulling upward and outward of the ribs, thus making
the space within the chest cavity larger. The lungs, which lie

within this cavity, are filled by
the air rushing into the larger
space thus made. That this
cavity is larger than it was at
first may be demonstrated by a
glance at the accompanying
figure. An expiration is simpler
than an inspiration, for it re
quires no muscular effort ; the
muscles relax, the breastbone
and ribs sink into place, while
the diaphragm returns to its
original position.

A piece of apparatus which illus
trates to a degree the mechanics of
breathing may be made as follows :
Attach a string to the middle of a
piece of sheet rubber. Tie the

Apparatus to show the mechanics of rubber over the lar S e end of a bel1
breathing. jar. Pass a glass Y-tube through a

334

RESPIRATION AND EXCRETION

rubber stopper. Fasten two small toy balloons to the branches of the
tube. Close the small end of the jar with the stopper. Adjust the tube
so that the balloons shall hang free in the jar. If now the rubber sheet is
pulled down by means of the string, the air pressure in the jar is reduced
and the toy balloons within expand, owing to the air pressure down the
tube. When the rubber is allowed to go back to its former position, the
balloons collapse.

Rate of Breathing and Amount of Air Breathed. During quiet
breathing, the rate of inspiration is from fifteen to eighteen times

per minute ; this rate largely depends on
the amount of physical work performed.
About 30 cubic inches of air are taken in
and expelled during the ordinary quiet
respiration. The air so breathed is called
tidal air. In a "long" breath, we take
in about 100 cubic inches in addition to
the tidal air. This is called complemental
air. By means of a forced expiration, it
is possible to expel from 75 to 100 cubic
inches more than tidal air; this air is
called reserve air. What remains in the
lungs, amounting to about 100 cubic
inches, is called the residual air. The
value of deep breathing is seen by a
glance at the diagram. It is only by
this means that we clear the lungs of the
reserve air with its accompanying load of
carbon dioxide.

Tidal Air
30 cu. in.

230
cu. in.

Respiration under Nervous Control. The

muscular movements which cause an inspira-

Diagram showing the relative
amounts of tidal, comple
mental, reserve, and resid
ual air. The brace shows ,. , ,, M1
the average lung capacity tlon are Partly under the control of the will,
for the adult man. but in part the movement is beyond our con
trol. The nerve centers which govern in
spiration are part of the sympathetic nervous system. Anything of
an irritating nature in the trachea or larynx will cause a sudden expiration
or cough. When a boy runs, the quickened respiration is due to the fact
that oxygen is used up rapidly and a larger quantity of carbon dioxide is

RESPIRATION AND EXCRETION

335

formed. The carbon dioxide in the blood stimulates the nervous center
which has control of respiration to greater activity, and quickened inspira
tion follows.

Need of Ventilation. During the course of a day the lungs
lose to the surrounding air nearly two pounds of carbon diox
ide. This means that about three fifths of a cubic foot is given
off by each person during an hour. When we are confined for
some time in a room, it becomes necessary to get rid of this
carbon dioxide. This can be done only by means of proper
ventilation. A considerable amount of moisture is given off from
the body, and this moisture in a crowded room is responsible for
much of the discomfort. The air becomes humid and uncomfort
able. It has been found that by keeping the air in motion in such
a room (as through the use of electric o \ ^^-~'^..-_-_^~-^~~^-^ | ^
fans) much of this discomfort is
obviated.

The presence of impurities in the
air of a room may easily be deter
mined by its odor. The odor of a
poorly ventilated room is due to
organic impurities given off with the
carbon dioxide. This, fortunately,
gives us an index of the amount of
waste material in the air. Among
the factors which take oxygen from
the air in a closed room and produce
carbon dioxide are burning gas or oil
lamps and stoves, and the presence
of a number of people.

Proper Ventilation. Ventilation
consists in the removal of air that
has been used, and the introduction
of a fresh supply to take its place.

Heated air rises, Carrying with it Three ways of ventilating a room.

much of the carbon dioxide and *^hh fe'tto b^m. '
other impurities. A good method ventilation? Explain.

o\s::jri

336

RESPIRATION AND EXCRETION

of ventilation for the home is to place a board two or three
inches high between the lower sash and the frame of a window
or to have the window open an inch or so at the top and the
bottom. An open fireplace in a room aids in ventilation because
of the constant draft up the flue.

Sweeping and Dusting. It is very easy to demonstrate the
amount of dust in the air by following the course of a beam of
light in a darkened room. We have already proved that spores of

mold and yeast exist in
the air. That bacteria
are also present can be
proved by exposing a
sterilized gelatin plate
to the air in a school
room for a few mo
ments. 1

Many of the bacteria
present in the air are
active in causing dis
eases of the respiratory
tract, such as diph
theria, membranous
croup, and tubercu
losis. Other diseases,
as colds, bronchitis
(inflammation of the
bronchial tubes), and

pneumonia (inflammation of the tiny air sacs of the lungs), are
also caused by bacteria.

Dust, with its load of bacteria, will settle on any horizontal sur
face in a room not used for three or four hours. Dusting and
sweeping should always be done with a damp cloth or broom,
otherwise the bacteria are simply stirred up and sent into the air

1 Expose two sterilized dishes containing culture media ; one in a room being
swept with a damp broom, and the other in a room which is being swept in the usual
manner. Note the formation of colonies of bacteria in each dish. In which dish
does the more abundant growth take place ?

Plate culture exposed for five minutes in a school
hall where pupils were passing to recitations.
Each spot is a colony of bacteria or mold.

RESPIRATION AND EXCRETION

337

again. The proper watering of streets before they are swept is
also an important factor in health. Much dust is composed largely
of dried excreta of animals. Soft-coal smoke does its share to
add to the impurities of the air, while sewer gas and illuminating
gas are frequently found in sufficient quantities to poison people.
Pure air is, as can be seen, almost an impossibility in a great city.

How to get Fresh Air. As we know, green plants give off in
the sunlight considerable more oxygen than they use, and they
use up carbon dioxide. The air in the country is naturally purer
than in the city, as smoke and bacteria are not so prevalent there,
and the plants in abundance give off oxygen. In the city the
night air is purer than day air,
because the factories have stopped
work, the dust has settled, and
fewer people are on the streets.
The old myth of "night air"
being inj urious has long since been
exploded, and thousands of people
of delicate health, especially those
who have weak throat or lungs,
are regaining health by sleeping
out of doors or with the windows
wide open. The only essential in
sleeping out of doors or in a room
with a low temperature is that the body be kept warm and the
head be protected from strong drafts by a nightcap or hood.
Proper ventilation at all times is one of the greatest factors in
good health.

Change of Air. Persons in poor health, especially those having
tuberculosis, are often cured by a change of air. This is not always
so much due to the composition of the air as to change of occupa
tion, rest, and good food. Mountain air is dry, and relatively
free from dust and bacteria, and often helps a person having tuber
culosis. Air at the seaside is beneficial for some forms of disease,
especially hay fever and bone tuberculosis. Many sanitariums
have been established for this latter disease near the ocean, and
thousands of lives are being annually saved in this way.

HUNTER, CIV. BI. 22

A sleeping porch, an ideal way to
get fresh air at night.

338

RESPIRATION AND EXCRETION

Ventilation of Sleeping Rooms. Sleeping in close rooms is
the cause of much illness. Beds ought to be placed so that a
constant supply of fresh air is given without a direct draft. This
may often be managed with the use of screens. Bedroom windows
should be thrown open in the morning to allow free entrance of the
sun and air, bedclothes should be washed frequently, and sheets

Unfavorable sleeping conditions. Explain why unfavorable.

and pillow covers often changed. Bedroom furniture should be
simple, and but little drapery allowed in the room.

Hygienic Habits of Breathing. Every one ought to accustom
himself upon going into the open air to inspire slowly and deeply
to the full capacity of the lungs. A slow expiration should follow.
Take care to force the air out. Breathe through the nose, thus
warming the air you inspire before it enters the lungs and chills
the blood. Repeat this exercise several times every day. You
will thus prevent certain of the air sacs which are not often used
from becoming hardened and permanently closed.

RESPIRATION AND EXCRETION 339

Relation of Proper Exercise to Health. We are all aware that
exercise in moderation has a beneficial effect upon the human or
ganism. The pale face, drooping shoulders, and narrow chest of
the boy or girl who takes no regular exercise is too well known.
Exercise, besides giving direct use of the muscles, increases the
work of the heart and lungs, causing deeper breathing and giving
the heart muscles increased work; it liberates heat and carbon
dioxide from the tissues where the work is taking place, thus in
creasing the respiration of the tissues themselves, and aids me
chanically in the removal of wastes from tissues. It is well known
that exercise, when taken some little time after eating, has a very
beneficial effect upon digestion. Exercise and especially games
are of immense importance to the nervous system as a means of
rest. The increasing number of playgrounds in this country is
due to this acknowledged need of exercise, especially for growing
children.

Proper exercise should be moderate and varied. Walking in
itself is a valuable means of exercising certain muscles, so is bicy
cling, but neither is ideal as the only form to be used. Vary your
exercise so as to bring different muscles into play, take exercise
that will allow free breathing out of doors if possible, and the
natural fatigue which follows will lead you to take the rest and sleep
that every normal body requires.

Exercise should always be limited by fatigue, which brings with
it fatigue poisons. This is nature's signal when to rest. If one's
use of diet and air is proper, the fatigue point will be much further
off than otherwise. One should learn to relax when not in activity.
The habit produces rest, even between exertions very close to
gether, and enables one to continue to repeat those exertions for
a much longer time than otherwise. The habit of lying down
when tired is a good one.

The Relation of Tight Clothing to Correct Breathing. It is
impossible to breathe correctly unless the clothing is worn loosely
over the chest and abdomen. Tight corsets and tight belts pre
vent the walls of the chest and the abdomen from pushing outward
and interfere with the drawing of air into the lungs. They may
also result in permanent distortion of parts of the skeleton directly

340 RESPIRATION AND EXCRETION

under the pressure. Other organs of the body cavity, as the stom
ach and intestines, may be forced downward, out of place, and in
consequence cannot perform their work properly.

Suffocation and Artificial Respiration. Suffocation results from the
shutting off of the supply of oxygen from the lungs. It may be brought
about by an obstruction in the windpipe, by a lack of oxygen in the air,
by inhaling some other gas in quantity, or by drowning. A severe electric
shock may paralyze the nervous centers which control respiration, thus
causing a kind of suffocation. In the above cases, death often may be
prevented by prompt recourse to artificial respiration. To accomplish
this, place the patient on his back with the head lower than the body ;
grasp the arms near the elbows and draw them upward and outward until
they are stretched above the head, on a line with the body. By this means
the chest cavity is enlarged and an inspiration produced. To produce
an expiration, carry the arms downward, and press them against the chest,
thus forcing the air out of the lungs. This exercise, regularly repeated
every few seconds, if necessary for hours, has been the source of saving
many lives.

Common Diseases of the Nose and Throat. Catarrh is a disease to
which people with sensitive mucous membrane of the nose and throat are
subject. It is indicated by the constant secretion of mucus from these
membranes. Frequent spraying of the nose and throat with some mild
antiseptic solutions is found helpful. Chronic catarrh should be attended
to by a physician. Often we find children breathing entirely through the
mouth, the nose being seemingly stopped up. When this goes on for
some time the nose and throat should be examined by a physician for
adenoids, or growths of soft masses of tissue which fill up the nose cavity,
thus causing a shortage of the air supply for the body. Many a child,
backward at school, thin and irritable, has been changed to a healthy,
normal, bright scholar by the removal of adenoids. Sometimes the
tonsils at the back of the mouth cavity may become enlarged, thus shut
ting off the air supply and causing the same trouble as we see in a case of
adenoids. The simple removal of the obstacle by a doctor soon cures
this condition. (See page 395.)

Organs of Excretion. All the life processes which take place
in a living thing result ultimately, in addition to giving off of car
bon dioxide, in the formation of organic wastes within the body.
The retention of these wastes which contain nitrogen, is harmful

RESPIRATION AND EXCRETION

341

-Suprarenal
body

Longitudinal section through a
kidney.

to animals. In man, the skin and

kidneys remove this waste from

the body, hence they are called the

organs of excretion.

The Human Kidney. The

human kidney is about four inches

long, two and one half inches wide,

and one inch in thickness. Its

color is dark red. If the structure

of the medulla and cortex (see

figure above) is examined under

the compound microscope, you will

find these regions to be composed

of a vast number of tiny branched

and twisted tubules. The outer

end of each of these tubules opens into the pelvis, the space within

the kidney ; the inner end, in the cortex, forms a tiny closed sac.

In each sac, the outer wall of the tube has grown inward and
carried with it a very tiny artery. This
artery breaks up into a mass of capillaries.
These capillaries, in turn, unite to form a
small vein as they leave the little sac.
Each of these sacs with its contained blood
vessels is called a glomerulus.

Wastes given off by the Blood in the
Kidney. In the glomerulus the blood
loses by osmosis, through the very thin
walls of the capillaries, first, a consider
able amount of water (amounting to
nearly three pints daily) ; second, a nitrog
enous waste material known as urea;
third, salts and other waste organic sub-
lus and tubule: , artery stances, uric acid among them.

bringing blood to part ;

b, capillary bringing blood These waste products, together with the
to glomerulus; &', vessel wa t er containing them, are known as urine.

continuing with blood to ,, . .. L i

vein ; c, vein ; t, tubule ; The total amount of nitrogenous waste leaving
G, glomerulus. the body each day is about twenty grams. It

342

RESPIRATION AND EXCRETION

is passed through the ureter to the urinary bladder; from this reservoir
it is passed out of the body, through a tube called the urethra. After
the blood has passed through the glomeruli of the kidneys it is purer
than in any other place in the body, because, before coming there, it
lost a large part of its burden of carbon dioxide in the lungs. After
leaving the kidney it has lost much of its nitrogenous waste. So de
pendent is the body upon the excretion of its poisonous material that,
in cases where the kidneys do not do their work properly, death may
ensue within a few hours.

Structure and Use of Sweat Glands. If you examine the
palm of your hand with a lens, you will notice the surface is thrown

Sweat-Duct

Sebaceous Gland

Horny layer
Pigment layer i :'':'

= > Epidermis

Subcutaneous layer of
connective tissue and fat

Diagram of a section of the skin. (Highly magnified.)

into little ridges. In these ridges may be found a large number of
very tiny pits; these are the pores or openings of the sweat-
secreting glands. From each opening a little tube penetrates deep
within the epidermis ; there, coiling around upon itself several
times, it forms the sweat gland. Close around this coiled tube are
found many capillaries. From the blood in these capillaries, cells
lining the wall of the gland take water, and with it a little carbon
dioxide, urea, and some salts (common salt among others). This
forms the excretion known as sweat. The combined secretions
from these glands amount normally to a little over a pint during

RESPIRATION AND EXCRETION 343

twenty-four hours. At all times, a small amount of sweat is given
off, but this is evaporated or is absorbed by the underwear; as
this passes off unnoticed, it is called insensible perspiration. In
hot weather or after hard manual labor the amount of perspira
tion is greatly increased.

Regulation of Heat of the Body. The bodily temperature
of a person engaged in manual labor will be found to be but little
higher than the temperature of the same person at rest. We know
from our previous experiments that heat is released. Muscles,
nearly one half the weight of the body, release about five sixths of
their energy as heat. At all times they are giving up some heat.
How is it that the bodily temperature does not differ greatly at
such times ? The temperature of the body is largely regulated by
means of the activity of the sweat glands. The blood carries
much of the heat, liberated in the various parts of the body by
the oxidation of food, to the surface of the body, where it is lost
in the evaporation of sweat. In hot weather the blood vessels of
the skin are dilated ; in cold weather they are made smaller by
the action of the nervous system. The blood thus loses water in
the skin, the water evaporates, and we are cooled off. The object
of increased perspiration, then, is to remove heat from the body.
With a large amount of blood present in the skin, perspiration is
increased ; with a small amount, it is diminished. Hence, we
have in the skin an automatic regulator of bodily temperature.

Sweat Glands under Nervous Control. The sweat glands,
like the other glands in the body, are under the control of the sym
pathetic nervous system. Frequently the nerves dilate the blood
vessels of the skin, thus helping the sweat glands to secrete, by
giving them more blood.

" Thus regulation is carried out by the nervous system deter
mining, on the one hand, the loss by governing the supply of blood
to the skin and the action of the sweat glands ; and on the other,
the production by diminishing or increasing the oxidation of the
tissues." FOSTER AND SHORE, Physiology.

Colds and Fevers. The regulation of blood passing through
the blood vessels is under control of the nervous system. If this
mechanism is interfered with in any way, the sweat glands may not

344

RESPIRATION AND EXCRETION

do their work, perspiration may be stopped, and the heat from
oxidation held within the body. The body temperature goes up,
and a fever results.

If the blood vessels in the skin are suddenly cooled when full of
blood, they contract and send the blood elsewhere. As a result a

congestion or cold may follow.
Colds are, in reality, a conges
tion of membranes lining cer
tain parts of the body, as the
nose, throat, windpipe, or
lungs.

When suffering from a cold,
it is therefore important not
to chill the skin, as a full blood
supply should be kept in it and
so kept from the seat of the
congestion. For this reason
hot baths (which call the
blood to the skin), the avoid
ing of drafts (which chill the
skin), and warm clothing are
useful factors in the care of
colds.

Hygiene of the Skin. The
skin is of importance both as
an organ of excretion and as
a regulator of bodily temper
ature. The skin of the entire

body should be bathed frequently so that this function of excretion
may be properly performed. Pride in one's own appearance for
bids a dirty skin. For those who can stand it, a cold sponge bath
is best. Soap should be used daily on parts exposed to dirt.
Exercise in the open air is important to all who desire a good
complexion. The body should be kept at an even temperature
by the use of proper underclothing. Wool, a poor conductor
of heat, should be used in winter, and cotton, which allows of a
free escape of heat, in summer.

A, blood vessels in skin normal; B, when
congested.

RESPIRATION AND EXCRETION 345

Cuts, Bruises, and Burns. In case the skin is badly broken,
it is necessary to prevent the entrance and growth of bacteria.
This may be done by washing the wound with weak antiseptic
solutions such as 3 per cent carbolic acid, 3 per cent lysol, or per
oxide of hydrogen (full strength). These solutions should be ap
plied immediately. A burn or scald should be covered at once
with a paste of baking soda, with olive oil, or with a mixture of
lime water and linseed oil. These tend to lessen the pain by keep
ing out the air and reducing the inflammation.

Summary of Changes in Blood within the Body. We have
already seen that red corpuscles in the lungs lose part of their load
of carbon dioxide that they have taken from the tissues, replacing
it with oxygen. This is accompanied by a change of color from
purple (in blood which is poor in oxygen) to that of bright red (in
richly oxygenated blood) . Other changes take place in other parts
of the body. In the walls of the food tube, especially in the small
intestine, the blood receives its load of fluid food. In the muscles
and other working tissues the blood gives up food and oxygen,
receiving carbon dioxide and organic waste in return. In the liver,
the blood gives up its sugar, and the worn-out red corpuscles which
break down are removed (as they are in the spleen) from the
circulation. In glands, it gives up materials used by the gland
cells in their manufacture of secretions. In the kidneys, it loses
water and nitrogenous wastes (urea). In the- skin, it also loses
some waste materials, salts, and water.

" The Effect of Alcohol on Body Heat. It is usually believed that
' taking a drink ' when cold makes one warmer. But such is
not the case. In reality alcohol lowers the temperature of the
body by dilating the blood vessels of the skin. It does this
by means of its influence on the nervous system. It is, therefore,
a mistake to drink alcoholic beverages when one is extremely cold,
because by means of this more bodily heat is allowed to escape.

" Because alcohol is quickly oxidized, and because heat is pro
duced in the process, it was long believed to be of value in main
taining the heat of the body. A different view now prevails as
the result of much observation and experiment. Physiologists
show by careful experiments that though the temperature of the

346 RESPIRATION AND EXCRETION

body rises during digestion of food, it is lowered for some hours
when alcohol is taken. The flush which is felt upon the skin after
a drink of wine or spirits is due in part to an increase of heat in
the body, but also to the paralyzing effect of the alcohol upon the
capillary walls, allowing them to dilate, and so permitting more of
the warm blood of the interior of the body to reach the surface.
There it is cooled by radiation, and the general temperature is
lowered." - MACY, Physiology.

Effect of Alcohol on Respiration. Alcohol tends to congest
the membrane of the throat and lungs. It does this by paralyzing
the nerves which take care of the tiny blood vessels in the walls of
the air tubes and air sacs. The capillaries become full of blood,
the air spaces are lessened, and breathing is interfered with. The
use of alcohol is believed by many physicians to predispose a
person to tuberculosis. Certainly this disease attacks drinkers
more readily than those who do not drink. Alcohol interferes
with the respiration of the cells because it is oxidized very quickly
within the body as it is quickly absorbed and sent to the cells.
So rapid is this oxidation that it interferes with the oxidation of
other substances. Using alcohol has been likened to burning kero
sene in a stove ; the operation is a dangerous one.

Effects of Tobacco on Respiration. Tobacco smoke contains
the same kind of poisons as the tobacco, with other irritating sub
stances added. It is extremely irritating to the throat ; it often
causes a cough, and renders it more liable to inflammation. If
the smoke is inhaled more deeply, the vaporized nicotine is still
more readily absorbed and may thus produce greater irritation in
the bronchi and lungs. Cigarettes are worse than other forms
of tobacco, for they contain the same poisons with others in addi
tion.

Effect of Alcohol on the Kidneys. It is said that alcohol is one
of the greatest causes of disease in the kidneys. The forms of
disease known as " fatty degeneration of the kidney " and
" Bright's disease " are both frequently due to this cause. The
kidneys are the most important organs for the removal of nitrog
enous waste.

Alcohol unites more easily with oxygen than most other food

RESPIRATION AND EXCRETION 347

materials, hence it takes away oxygen that would otherwise be
used in oxidizing these foods. Imperfect oxidation of foods
causes the development and retention of poisons in the blood
which it becomes the work of the kidneys to remove. If the kid
neys become overworked, disease will occur. Such disease is likely
to make itself felt as rheumatism or gout, both of which are be
lieved to be due to waste products (poisons) in the blood.

Poisons produced by Alcohol. When too little oxygen enters the
draft of the stove, the wood is burned imperfectly, and there are
clouds of smoke and irritating gases. So, if oxygen unites with the
alcohol and too little reaches the cells, instead of carbon dioxide,
water, and urea being formed, there are other products, some
of which are exceedingly poisonous and which the kidneys handle
with difficulty. The poisons retained in the circulation never fail
to produce their poisonous effects, as shown by headaches, clouded
brain, pain, and weakness of the body. The word " intoxication "
means " in a state of poisoning." These poisons gradually accumu
late as the alcohol takes oxygen from the cells. The worst effects
come last, when the brain is too benumbed to judge fairly of their
harm.

REFERENCE BOOKS
ELEMENTARY

Hunter, Laboratory Problems in Civic Biology. American Book Company.
Davison, Human Body and Health. American Book Company.
Gulick, Hygiene Series, Emergencies, Good Health. Girm and Company.
Hough and Sedgwick, The Human Mechanism. Ginn and Company.
Macy, General Physiology. American Book Company.
Ritchie, Human Physiology. World Book Company.

XXIII. BODY CONTROL AND HABIT FORMATION

Problems. How is body control maintained ?

(a) What is the mechanism of direction and control ?

(&) What is the method of direction and control ?

(c} What are habits ? How are they formed and how broken ?

(d) What are the organs of sense? What are their uses?

(e} How does alcohol affect the nervous system?

LABORATORY SUGGESTIONS

Demonstration. Sensory motor reactions.

Demonstration. Nervous system. Models and frog dissections.

Demonstration. Neurones under compound microscope (optional).

Demonstration. Reflex acts are unconscious acts : show how conscious
acts may become habitual.

Home exercise in habit forming.

The senses. Home exercises. (1) To determine areas most sensitive
to touch. (2) To determine or map out hot and cold spots on an area on
the wrist. (3) To determine functions of different areas on tongue.

Demonstration. Show how eye defects are tested.

Laboratory summary. The effects of alcohol on the nervous system.

The Body a Self-directed Machine. Throughout the preced
ing chapters the body has been likened to an engine, which, while
burning its fuel, food, has done work. If we were to carry our
comparison further, however, the simile ceases. For the engineer
runs the engine, while the bodily machine is self-directive.

Moreover, most of the acts we perform during a day's work are
results of the automatic working of this bodily machine. The
heart pumps ; the blood circulates its load of food, oxygen, and
wastes ; the movements of breathing are performed ; the thousand
and one complicated acts that go on every day within the body are
seemingly undirected.

Automatic Activity. In addition to this, numbers of other of
our daily acts are not thought about. If we are well-regulated

348

BODY CONTROL AND HABIT FORMATION 349

body machines, we
get up in the morn
ing, automatically
wash, clean our
teeth, dress, go to
the toilet, get our
breakfast, walk to
school, even per
form such compli
cated processes as
that of writing,
without thinking
about or directing
the machine. In
these respects we
have become crea
tures of habit.
Certain acts which
once we might
have learned con
sciously, have be
come automatic.

But once at
school, if we are
really making good
in our work in the
classroom, we be
gin a higher con
trol of our bodily
functions. Auto
matic control acts
no longer, and sen
sation is not the
only guide for we now begin to make conscious choice; we weigh
this matter against another, in short, we think.

Parts of the Nervous System. This wonderful self -directive
apparatus placed within us, which is in part under control of our

The central nervous system.

350 BODY CONTROL AND HABIT FORMATION

will, is known as the nervous system. In the vertebrate animals,
including man, it consists of two divisions. One includes the
brain, spinal cord, the cranial and spinal nerves, which together
make up the cerebro-spinal nervous system. The other division is
called the sympathetic nervous system and has to do with those
bodily functions which are beyond our control. Every group of
cells in the body that has work to do (excepting the floating cells
of the blood) -is directly influenced by these nerves. Our bodily
comfort is dependent upon their directive work. The organs
which put us in touch with our surroundings are naturally at the
surface of the body. Small collections of nerve cells, called ganglia,
are found in all parts of the body. These nerve centers are con
nected, to a greater or less degree, with the surface of the body by
the nerves, which serve as pathways between the end organs of
touch, sight, taste, etc., and the centers in the brain or spinal cord.
Thus sensation is obtained.

Sensations and Reactions. We have already seen that simpler
forms of life perform certain acts because certain outside forces act
ing upon them cause them to react to the stimulus from without.
The one-celled animal responds to the presence of food, to heat, to
oxygen, to other conditions in its surroundings. An earthworm is
repelled by light, is attracted by food. All animals, including man,
are put in touch with their surroundings by what we call the or
gans of sensation. The senses of man, besides those we commonly
know as those of sight, hearing, taste, smell, and touch, are those of
temperature, pressure, and pain. It is obvious that such organs,
if they are to be of use to an animal, must be at the outside of the
body. Thus we find eyes and ears in the head, and taste cells
in the mouth, while other cells in the nose perceive odors, and
still others in the skin are sensitive to heat or cold, pressure or
pain.

But this is not all. Strangely enough, we do not see with our
eyes or taste with our taste cells. These organs receive the sensa
tions, and by means of a complicated system of greatly elongated
cell structures, the message is sent inward, relayed by other elon
gated cells until the sensory message reaches an inner station, in
the central nervous system. We see and hear and smell in our

BODY CONTROL AND HABIT FORMATION 351

brain. Let us next examine the structure of the nerve cells or
neurons part of which serve as pathways for these messages.

Neurones. A nerve cell, like other cells in the body, is a mass
of protoplasm containing a nucleus. But the body of the nerve
cell is usually rather irregular in shape, and distinguished from
most other cells by possessing several delicate, branched proto
plasmic projections called dendrites. One of
these processes, the axon, is much longer
than the others and ends in a muscle or
organ of sensation. The axon forms the
pathway over which nervous impulses travel
to and from the nerve centers.

A nerve consists of a bundle of such tiny
axons, bound together by connective tissue.
As a nerve ganglia is a center of activity in
the nervous system, so a cell body is a center
of activity which may send an impulse over
this thin strand of protoplasm (the axon)
prolonged many hundreds of thousands of
times the length of the cell. Some neurones
in the human body, although visible only
under the compound microscope, give rise
to axons several feet in length.

Because some bundles of axons originate
in organs that receive sensations and send
those sensations to the central nervous sys
tem, they are called sensory nerves. Other
axons originate in the central nervous system and pass outward
as nerves producing movement of muscles. These are called
motor nerves.

The Brain of Man. In man, the central nervous system consists of a
brain and spinal cord inclosed in a bony case. From the brain, twelve
pairs of nerves are given off ; thirty-one pairs more leave the spinal cord.
The brain has three divisions. The cerebrum makes up the largest part.
In this respect it differs from the cerebrum of the frog and other verte
brates. It is divided into two lobes, the hemispheres, which are connected
with each other by a broad band of nerve fibers. The outer surface of the

Nerve-end*

Diagram of a neuron or
nerve unit.

352 BODY CONTROL AND HABIT FORMATION

cerebrum is thrown into folds or convolutions which give a large surface,
the cell bodies of the neurons being found in this part of the cerebrum.
Holding the cell bodies and fibers in place is a kind of connective tissue.
The inner part (white in color) is composed largely of fibers which pass
to other parts of the brain and down into the spinal cord. Under the
cerebrum, and dorsal to it, lies the little brain, or cerebellum. The two
sides of the cerebellum are connected by a band of nerve fibers which
run around into the lower hindbrain or medulla. This band of fibers is
called the pons. The medulla is, in structure, part of the spinal cord, and
is made up largely of fibers running longitudinally.

The Sympathetic Nervous System. Connected with the central ner
vous system is that part of the nervous apparatus that controls the mus
cles of the digestive tract and blood vessels, the secretions of gland cells,
and all functions which have to do with life processes in the body. This
is called the sympathetic nervous system.

Functions of the Parts of the Central Nervous System of the
Frog. From careful study of living frogs, birds, and some mam
mals we have learned much of what we know of the functions of
the parts of the central nervous system in man.

It has been found that if the entire brain of a frog is destroyed
and separated from the spinal cord, " the frog will continue to
live, but with a very peculiarly modified activity." It does not
appear to breathe, nor does it swallow. It will not move or croak,
but if acid is placed upon the skin so as to irritate it, the legs make
movements to push away and to clean off the irritating substance.
The spinal cord is thus shown to be a center for defensive move
ments. If the cerebrum is separated from the rest of the nervous
system, the frog seems to act a little differently from the normal
animal. It jumps when touched, and swims when placed in water.
It will croak when stroked, or swallow if food be placed in its mouth.
But it manifests no hunger or fear, and is in every sense a machine
which will perform certain actions after certain stimulations. Its
movements are automatic. If now we watch the movements of
a frog which has the brain uninjured in any way, we find that it
acts spontaneously. It tries to escape when caught. It feels
hungry and seeks food. It is capable of voluntary action. It
acts like a normal individual.

BODY CONTROL AND HABIT FORMATION 353

Functions of the Cerebrum. In general, the functions of the
different parts of the brain in man agree with those functions
we have already observed in the frog. The cerebrum has to do
with conscious activity ; that is, thought. It presides over what
we call our thoughts, our will, and our sensations. A large part
of the area of the outer layer of the cerebrum seems to be given
over to some one of the different functions of speech, hearing,
sight, touch, movements of bodily parts. The movement of the

Diagram to show the parts of the brain and action of the different parts of the

brain.

smallest part of the body appears to have its definite localized
center in the cerebrum. Experiments have been performed on mon
keys, and these, together with observations made on persons who
had lost the power of movement of certain parts of the body,
and who, after death, were found to have had diseases localized
in certain parts of the cerebrum, have given to us our knowledge
on this subject.

Reflex Actions ; their Meaning. If through disease or for
other reasons the cerebrum does not function, no will power is

HUNTER, CIV. Bl. 23

354 BODY CONTROL AND HABIT FORMATION

Diagram of ti

path of a simple reflex action.

exerted, nor are intelligent acts performed. All acts performed in
such a state are known as reflex actions. The involuntary brush
ing of a fly from the face, or the attempt to move away from the

source of annoyance
when tickled with a
feather, are examples
of reflexes. In a
reflex act, a person
does not think before
acting. The nervous
impulse comes from
the outside to cells
that are not in the
cerebrum. The mes
sage is short-circuited
back to the surface

by motor nerves, without ever having reached the thinking
centers. The nerve cells which take charge of such acts are lo
cated in the cerebellum or spinal cord.

Automatic Acts. Some acts, however, are learned by con
scious thought, as writing, walking, running, or swimming. Later
in life, however, these activities become automatic. The actual
performance of the action is then taken up by the cerebellum,
medulla, and spinal ganglia. Thus the thinking portion of the
brain is relieved of part of its work.

Bundles of Habits. It is surprising how little real thinking we
do during a day, for most of our acts are habitual. Habit takes
care of our dressing, our bathing, our care of the body organs, our
methods of eating ; even our movements in walking and the kind
of hand we write are matters of habit forming. We are bundles of
habits, be they good ones or bad ones.

Habit Formation. The training of the different areas in the
cerebrum to do their work well is the object of education. When
we learned to write, we exerted conscious effort in order to make
the letters. Now the act of forming the letters is done without
thought. By training, the act has become automatic. In the
beginning, a process may take much thought and many trials

BODY CONTROL AND HABIT FORMATION 355

before we are able to complete it. After a little practice, the same
process may become almost automatic. We have formed a habit.
Habits are really acquired reflex actions. They are the result of
nature's method of training. The conscious part of the brain has
trained the cerebellum or spinal cord to do certain things that, at
first, were taken charge of by the cerebrum.

Importance of Forming Right Habits. Among the habits early
to be acquired are the habits of studying properly, of concentrating
the mind, of learning self-control, and, above all, of contentment.
Get the most out of the world about you. Remember that the
immediate effect in the study of some subjects in school may not
be great, but the cultivation of correct methods of thinking may be
of the greatest importance later in life. The man or woman who
has learned how to concentrate on a problem, how to weigh all sides
with an unbiased mind, and then to decide on what they believe to
be best and right are the efficient and happy ones of their generation.

" The hell to be endured hereafter, of which theology tells, is no worse
than the hell we make for ourselves in this world by habitually fashioning
our characters in the wrong way. Could the young but realize how soon
they will become mere walking bundles of habits, they would give more
heed to their conduct while in the plastic state. We are spinning our
own fates, good or evil, and never to be undone. Every smallest stroke
of virtue or of vice leaves its never-so-little scar. The drunken Rip Van
Winkle, in Jefferson's play, excuses himself for every fresh dereliction by
saying, ' I won't count this time ! ' Well ! he may not count it, and a
kind Heaven may not count it; but it is being counted none the less.
Down among his nerve cells and fibers the molecules are counting it, regis
tering and storing it up to be used against him when the next temptation
comes. Nothing we ever do is, in strict scientific literalness, wiped out.
Of course this has its good side as well as its bad one. As we become per
manent drunkards by so many separate drinks, so we become saints in the
moral, and authorities in the practical and scientific, spheres by so many
separate acts and hours of work. Let no youth have any anxiety about
the upshot of his education, whatever the line of it may be. If he keep
faithfully busy each hour of the working day, he may safely leave the final
result to itself. He can with perfect certainty count on waking up some
fine morning, to find himself one of the competent ones of his generation,
in whatever pursuit he may have singled out." JAMES, Psychology.

356 BODY CONTROL AND HABIT FORMATION

Some Rules for Forming Good Habits. Professor Home gives
several rules for making good or breaking bad habits. They are :
" First, act on every opportunity. Second, make a strong start.
Third, allow no exception. Fourth, for the bad habit establish a good
one. Fifth, summoning all the man within, use effort of will."
Why not try these out in forming some good habit ? You will
find them effective.

Necessity of Food, Fresh Air, and Rest. The nerve cells, like
all other cells in the body, are continually wasting away and being
rebuilt. Oxidation of food material is more rapid when we do
mental work. The cells of the brain, like muscle cells, are not
only capable of fatigue, but show this in changes of form and of

contents. Food brought to them in the
blood, plenty of fresh air, especially when
engaged in active brain work, and rest
at proper times, are essential in keeping
the nervous system in condition. One
of the best methods of resting the brain
cells is a change of occupation. Tennis,
jf \ 9 \ golf, baseball, and other outdoor sports

b combine muscular exercise with brain

The effect of fatigue on nerve activity of a different sort from that of

business or school work. But change
of occupation will not rest exhausted
neurones. For this, sleep is necessary. Especially is sleep an
important factor in the health of the nervous system of growing
children.

Necessity of Sleep. Most brain cells attain their growth
early in life. Changes occur, however, until some time after the
school age. Ten hours of sleep should be allowed for a child, and
at least eight hours for an adult. At this time, only, do the brain
cells have opportunity to rest and store food and energy for their
working period.

Sleep is one way in which all cells in the body, and particularly
those of the nervous system, get their rest. The nervous system,
by far the most delicate and hardest-worked set of tissues in the
body, needs rest more than do other tissues, for its work directing

BODY CONTROL AND HABIT FORMATION 357

the body only ends with sleep or unconsciousness. The afternoon
nap, snatched by the brain worker, gives him renewed energy for
his evening's work. It is not hard application to a task that
wearies the brain ; it is continuous work without rest.

THE SENSES

Touch. In animals having a hard outside covering, such as certain
worms, insects, and crustaceans, minute hairs, which are sensitive to touch,
are found growing out from the body covering. At the base of these hairs
are found neurones which send axons inward to the central nervous system.
Organs of Touch. In man, the nervous mechanism which governs
touch is located in the folds of the dermis or in the skin. Special nerve
endings, called the tactile corpus
cles, are found there, each in
closed in a sheath or capsule of
connective tissue. Inside is a
complicated nerve ending, and
axons pass inward to the central
nervous system. The number
of tactile corpuscles present in a
given area of the skin determines
the accuracy and ease with which
objects may be known by touch.

If you test the different parts

Nerves in the skin: a, nerve fiber; b, tactile
papillae, containing a tactile corpuscle ;
c, papillae containing blood vessels.
(After Benda.)

of the body, as the back of the

hand, the neck, the skin of the

arm, of the back, or the tip of

the tongue, with a pair of open

dividers, a vast difference in the accuracy with which the two points

may be distinguished is noticed. On the tip of the tongue, the two points

need only be separated by ^ of an inch to be so distinguished. In the

small of the back, a distance of 2 inches may be reached before the dividers

feel like two points.

Temperature, Pressure, Pain. The feeling of temperature, pressure,
and pain is determined by different end organs in the skin. Two kinds
of nerve fibers exist in the skin, which give distinct sensations of heat and
cold. These nerve endings can be located by careful experimentation.
There are also areas of nerve endings which are sensitive to pressure,
and still others, most numerous of all, sensitive to pain.

358 BODY CONTROL AND HABIT FORMATION

Taste Cells

Supporting
Cells

A, isolated taste bud,
from whose upper free
end project the ends of
the taste cells ; B, sup
porting or protecting
cell ; C, sensory cell.

Taste Organs. The surface of the tongue is folded into a number of
little projections known as papillae. These may be more easily found on
your own tongue if a drop of vinegar is placed on its broad surface. In the
folds, between these projections on the top and
back part of the tongue, are located the organs of
taste. These organs are called taste buds.

Each taste bud consists of a collection of
spindle-shaped neurones, each cell tipped at its
outer end with a hairlike projection. These cells
send inward fibers to other cells, the fibers from
which ultimately reach the brain. The sensory
cells are surrounded by a number of projecting
cells which are arranged in layers about them.
Thus the organ in longitudinal section looks
somewhat like an onion cut lengthwise.

How we Taste. Four kinds of substances
may be distinguished by the sense of taste. These

are sweet, sour, bitter, and salt. Certain taste cells located near the
back of the tongue are stimulated only by a bitter taste. Sweet sub
stances are perceived by cells near the tip of the tongue, sour substances
along the sides, and salt about equally all over the surface. A substance
must be dissolved in fluid in order to be tasted. Many things which
we believe we taste are in reality perceived by the sense of smell. Such
are spicy sauces and flavors of meats and vegetables. This may easily
be proved by holding the nose and chewing, with closed eyes, several
different substances, such as an apple, an onion, and a raw potato.

Smell. The sense of smell is located in the membrane lining the upper
part of the nose. Here are found a large number of rod-shaped cells which
are connected with the brain by means of the olfactory nerve. In order
to perceive odors, it is necessary to have them diffused in the air ; hence
we sniff so as to draw in more air over the olfactory cells.

The Organ of Hearing. The organ of hearing is the ear. The outer
ear consists of a funnel-like organ composed largely of cartilage which is
of use in collecting sound waves. This part of the ear incloses the audi
tory canal, which is closed at the inner end by a tightly stretched mem
brane, the tympanic membrane or ear drum. The function of the tym
panic membrane is to receive sound waves, for all sound is caused by
vibrations in the air, these vibrations being transmitted, by the means
of a complicated apparatus found in the middle ear, to the real organ of
hearing located in the inner ear.

BODY CONTROL AND HABIT FORMATION 359

fnc.

Coc.

Middle Ear. The middle ear in man is a cavity inclosed by the tem
poral bone, and separated from the outer ear by the tympanic membrane.
A little tube called the Eustachian tube connects the inner ear with the
mouth cavity. By allowing air to enter from the mouth, the air pressure
is equalized on the ear drum. For this reason, we open the mouth at the
time of a heavy concussion and thus prevent the rupture of the delicate
tympanic membrane.
Placed directly against
the tympanic mem
brane and connecting
it with the inner ear is
a chain of three tiny
bones, the smallest
bones of the body. The
outermost is called the
hammer; the next the
anvil; the third the
stirrup. All three bones
are so called from their
resemblances in shape
to the articles for which
they are named. These
bones are held in place
by very small muscles
which are delicately
adjusted so as to tighten or relax the membranes guarding the middle and
inner ear.

The Inner Ear. The inner ear is one of the most complicated, as
well as one of the most delicate, organs of the body. Deep within the
temporal bone there are found two parts, one of which is called, collec
tively, the semicircular canal region, the other the cochlea, or organ of hear
ing.

It has been discovered by experimenting with fish, in which the semi
circular canal region forms the chief part of the ear, that this region has
to do with the equilibrium or balancing of the body. We gain in part our
knowledge of our position and movements in space by means of the semi
circular canals.

That part of the ear which receives sound waves is known as the cochlea,
or snail shell, because of its shape. This very complicated organ is lined
with sensory cells provided with cilia. The cavity of the cochlea is filled

Section of ear : E.M., auditory canal ; Ty.M., tympanic
membrane ; Eu., Eustachian tube ; Ty, middle ear ;
Coc., A.S.C., E.S.C., etc., internal ear.

360 BODY CONTROL AND HABIT FORMATION

with a fluid. It is believed that somewhat as a stone thrown into water
causes ripples to emanate from the spot where it strikes, so sound waves
are transmitted by means of the fluid filling the cavity to the sensory cells
of the cochlea (collectively known as the organ of Corti) and thence to the
brain by means of the auditory nerve.

The Character of Sound. When vibrations which are received by the
ear follow each other at regular intervals, the sound is said to be musical.
If the vibrations come irregularly, we call the sound a noise. If the vibra
tions come slowly, the pitch of the sound is low ; if they come rapidly, the
pitch is high. The ear is able to perceive as low as thirty vibrations per
second and as high as almost thirty thousand. The ear can be trained to
recognize sounds which are unnoticed in untrained ears.

The Eye. The eye or organ of vision is an almost spherical body which
fits into a socket of bone, the orbit. A stalklike structure, the optic nerve,

connects the eye with the brain. Free
movement is obtained by means of six
little muscles which are attached to
the outer coat, the eyeball, and to the
bony socket around the eye.

The wall of the eyeball is made up
of three coats. An outer tough white
coat, of connective tissue, is called the
sclerotic coat. Under the sclerotic

Longitudinal section through COat > in frOIlt > the e ^ e bul S 6S utward

the eye. a little. Here the outer coat is con

tinuous with a transparent tough layer

called the cornea. A second coat, the choroid, is supplied with blood
vessels and cells which bear pigments. It is a part of this coat which
we see through the cornea as the colored part of the eye (the iris).
In the center of the iris is a small circular hole (the pupil). The iris
is under the control of muscles, and may be adjusted to varying
amounts of light, the hole becoming larger in dim light, and smaller
in bright light. The inmost layer of the eye is called the retina. This
is, perhaps, the most delicate layer in the entire body. Despite the
fact that the retina is less than J ff of an inch in thickness, there are
several layers of cells in its composition. The optic nerve enters the
eye from behind and spreads out to form the surface of the retina.
Its finest fibers are ultimately connected with numerous elongated
cells which are stimulated by light. The retina is dark purple in color,
this color being caused by a layer of cells next to the choroid coat. This

BODY CONTROL AND HABIT FORMATION 361

accounts for the black appearance of the pupil of the eye, when we look
through the pupil into the darkened space within the eyeball. The
retina acts as the sensitized plate in the camera, for on it are received the
impressions which are transformed and sent to the brain as sensations of
sight. The eye, like the camera, has a lens. This lens is formed of
transparent, elastic material. It is found directly behind the iris and is
attached to the choroid coat by means of delicate ligaments. In front of
the lens is a small cavity filled with a watery fluid, the aqueous humor,
while behind it is the main cavity of the eye, filled with a transparent,
almost jelly like, vitreous humor. The lens itself is elastic. This circum
stance permits of a change of form and, in consequence, a change of
focus upon the retina of the lens. By means of this change in form, or
accommodation, we are able to distinguish between near and distant
objects.

Defects in the Eye. In some eyes, the lens is in focus for near objects,
but is not easily focused upon distant objects; such an eye is said to be
nearsighted. Other eyes
which do not focus clearly
on objects near at hand are

said to bs farsighted. Still

, , . . . How far away can you read these letters?

another eye detect IS astlg- Measure the distance. Twenty feet is a
matism, which causes images test for the normal eye.
of lines in a certain direction

to be indistinct, while images of lines transverse to the former are distinct.
Many nervous troubles, especially headaches, may be due to eye strain.
We should have our eyes examined from time to time, especially if we are
subject to headaches.

The Alcohol Question. It is agreed by investigators that in
large or continued amounts alcohol has a narcotic effect ; that it
first dulls or paralyzes the nerve centers which control our judg
ment, and later acts upon the so-called motor centers, those which
control our muscular activities.

The reason, then, that a man in the first stages of intoxication
talks rapidly and sometimes wittily, is because the centers of judg
ment are paralyzed. This frees the speech centers from control
exercised by our judgment, with the resultant rapid and free flow
of speech.

In small amounts alcohol is believed by some physiologists to
have always this same narcotic effect, while other physiologists

Y F E V

362 BODY CONTROL AND HABIT FORMATION

think that alcohol does stimulate the brain centers, especially
the higher centers, to increased activity. Some scientific and pro
fessional men use alcohol in small amounts for this stimulation and
report no seeming harm from the indulgence. Others, and by
far the larger number, agree that this stimulation from alcohol is
only apparent and that even in the smallest amounts alcohol has
a narcotic effect.

The Paralyzing Effects of Alcohol on the Nervous System.
Alcohol has the effect of temporarily paralyzing the nerve centers.
The first effect is that of exhilaration. A man may do more work
for a time under the stimulation of alcohol. This stimulation,
however, is of short duration and is invariably followed by a period
of depression and inertia. In this latter state, a man will do less
work than before. In larger quantities, alcohol has the effect of
completely paralyzing the nerve centers. This is seen in the case
of a man " dead drunk." He falls in a stupor because all of the
centers governing speech, sight, locomotion, etc., have been tem
porarily paralyzed. If a man takes a very large amount of al
cohol, even the nerve centers governing respiration and circulation
may become poisoned, and the victim will die.

Effect on the Organs of Special Sense. Professor Forel, one of
the foremost European experts on the question of the effect of
alcohol on the nervous system, says : " Through all parts of ner
vous activity from the innervation of the muscles and the simplest
sensation to the highest activity of the soul the paralyzing effect
of alcohol can be demonstrated." Several experimenters of un
doubted ability have noted the paralyzing effect of alcohol even
in small doses. By the use of delicate instruments of precision,
Ridge tested the effect of alcohol on the senses of smell, vision, and
muscular sense of weight. He found that two drams of absolute
alcohol produced a positive decrease in the sensitiveness of the
nerves of feeling, that so small a quantity as one half dram of
absolute alcohol diminished the power of vision and the muscular
sense of weight. Kraepelin and Kurz by experiment determined
that the acuteness of the special senses of sight, hearing, touch,
taste, and smell was diminished by an ounce of alcohol, the power
of vision being lost to one third of its extent and a similar effect

BODY CONTROL AND HABIT FORMATION 363

being produced on the other special senses. Other investigators
have reached like conclusions. There is no doubt but that alcohol,
even in small quantities, renders the organs of sense less sensitive
and therefore less accurate.

Effect of Alcohol on the Ability to Resist Disease. Among
certain classes of people the belief exists that alcohol in the form
of brandy or some other drink or in patent medicines, malt tonics,

15-24 25-34 35-44

Table to show a comparison of chances of illness and death in drinkers and
non-drinkers. Solid black, drinkers. (From German sources.)

and the like is of great importance in building up the body so as
to resist disease or to cure it after disease has attacked it. Nothing
is further from the truth. In experiments on a large number of
animals, including dogs, rabbits, guinea pigs, fowls, and pigeons,
Laitenen, of the University of Helsingsfors, found that alcohol, with
out exception, made these animals more susceptible to disease than
were the controls.

One of the most serious effects of alcohol is the lowered
resistance of the body to disease. It has been proved that a
much larger proportion of hard drinkers die from infectious or
contagious diseases than from special diseased conditions due
to the direct action of alcohol on the organs of the body. This

364 BODY CONTROL AND HABIT FORMATION

lowered resistance is shown in increased liability to contract
disease and increased severity of the disease. We have already
alluded to the findings of insurance companies with reference to
the length of life 'the abstainers from alcohol have a much
better chance of a longer life and much less likelihood of infection
by disease germs.

Use of Alcohol in the Treatment of Disease. In the London
Temperance Hospital alcohol was prescribed seventy-five times
in thirty-three years. The death rate in this hospital has
been lower than that of most general hospitals. Sir William
Collins, after serving nineteen years as surgeon in this hospital,
said :

" In my experience, speaking as a surgeon, the use of alcohol is
not essential for successful surgery. ... At the London Tem
perance Hospital, where alcohol is very rarely prescribed, the mor
tality in amputatiori cases and in operation cases generally is re
markably low. Total abstainers are better subjects for operation,
and recover more rapidly from accidents, than those who habitu
ally take stimulants."

In a paper read at the International Congress on Tuberculosis, in
New York, 1906, Dr. Crothers remarked that alcohol as a remedy
or a preventive medicine in the treatment of tuberculosis is a most
dangerous drug, and that all preparations of sirups containing
spirits increase, rather than diminish, the disease.

Dr. Kellogg says : " The paralyzing influence of alcohol upon
the white cells of the blood a fact which is attested by all
investigators is alone sufficient to condemn the use of this drug
in acute or chronic infections of any sort."

The Effect of Alcohol upon Intellectual Ability. With regard
to the supposed quickening of the mental processes Horsley and
Sturge, in their recent book, Alcohol and the Human Body, say :
" Kraepelin found that the .simple reaction period, by which is
meant the time occupied in making a mere response to a signal, as,
for instanc'e, to the sudden appearance of a flag, was, after the in-
gestion of a small quantity of alcohol ( J to J ounce) , slightly accel
erated ; that there was, in fact, a slight shortening of the time, as
though the brain were enabled to operate more quickly than be-

BODY CONTROL AND HABIT FORMATION 365

fore. But he found that after a few minutes, in most cases, a
slowing of mental action began, becoming more and more marked,
and enduring as long as the alcohol was in active operation in the
body, i.e. four to five hours. . . . Kraepelin found that it was
only more or less automatic work, such as reading aloud, which was
quickened by alcohol, though even this was rendered less trust
worthy and accurate." Again : " Kraepelin had always shared
the popular belief that a small quantity of alcohol (one to two
teaspoonfuls) had an accelerating effect on the activity of his mind,

CONDITIONS,

Average -number -figures
-memorized

5 ix

Yion-alcolaoL
days.

1280*66

alcohol
days.

non

,-: alcohol

daijs

alcoTaol
days,

Effect of use of alcohol on memory.

enabling him to perform test operations, as the adding and sub
tracting and learning of figures more quickly. But when he came
to measure with his instruments the exact period and time occupied,
he found, to his astonishment, that he had accomplished these
mental operations, not more, but less, quickly than before. . . .
Numerous further experiments were carried out in order to test
this matter, and these proved that alcohol lengthens the time taken
to perform complex mental processes, while by a singular illusion the
person experimented upon imagines that his psychical actions are
rendered more rapid."

366 BODY CONTROL AND HABIT FORMATION

Attention that is, the power of the mind to grasp and con
sider impressions obtained through the senses is weakened by
drink. The ability of the mind to associate or combine ideas, the
faculty involved in sound judgment, showed that when the persons
had taken the amounts of alcohol mentioned, the combinations of
ideas or judgments expressed by them were confused, foggy, senti
mental, and general. When the persons had taken no alcohol,

COND

ITIONS -

Average time in mainutes
no 20 30

todays
WITHOUT
alcohol

l8Ynin.2sec.

30rnm48sec

4Sdays

WITHOUT
alcohol

24rnml6sec.

The effect of alcohol upon ability to do mental work.

their judgments were rational, specific, keen, showing closer ob
servation.

" The words of Professor Helmholtz at the celebration of his seven
tieth birthday are very interesting in this connection. He spoke of
the ideas flashing up from the depths of the unknown soul, that
lies at the foundation of every truly creative intellectual produc
tion, and closed his account of their origin with these words :
1 The smallest quantity of an alcoholic beverage seemed to frighten
these ideas away.' ' - DR. G. SIMS WOODHEAD, Professor of Pa
thology, Cambridge University, England.

Professor Von Bunge ( Textbook of Physiological and Pathological
Chemistry) of Switzerland says that : " The stimulating action
which alcohol appears to exert on the brain functions is only a para-

BODY CONTROL AND HABIT FORMATION 367

lytic action. The cerebral functions which are first interfered
with are the power of clear judgment and reason. No man ever
became witty by aid of spirituous drinks. The lively gesticula
tions and useless exertions of intoxicated people are due to paraly
sis, the restraining influences, which prevent a sober man from
uselessly expending his strength, being removed."

The Drink Habit. The harmful effects of alcohol (aside from
the purely physiological effect upon the tissues and organs of the
body) are most terribly seen in the formation of the alcohol habit.
The first effect of drinking alcoholic liquors is that of exhilaration.
After the feeling of exhilaration is gone, for this is a temporary
state, the subject feels depressed and less able to work than before
he took the drink. To overcome this feeling, he takes another
drink. The result is that before long he finds a habit formed from
which he cannot escape. With body and mind weakened, he
attempts to break off the habit. But meanwhile his will, too,
has suffered from overindulgence. He has become a victim of the
drink habit !

" The capital argument against alcohol, that which must even
tually condemn its use, is this, that it takes away all the reserved
control, the power of mastership, and therefore offends against the
splendid pride in himself or herself, which is fundamental in every
man or woman worth anything." DR. JOHN JOHNSON, quoting
Walt Whitman.

Self-indulgence, be it in gratification of such a simple desire as
that for candy or the more harmful indulgence in tobacco or al
coholic beverages, is dangerous not only in its immediate effects
on the tissues and organs, but in its more far-reaching effects on
habit formation. Each one of us is a bundle of appetites. If we
gratify appetites of the wrong kind, we are surely laying the
foundation for the habit of excess. Self-denial is a good thing
for each of us to practice at one time or another, if for no
other purpose than to be ready to fight temptation when it
comes.

The Economic Effect of Alcoholic Poisoning. In the struggle
for existence, it is evident that the man whose intellect is the quick
est and keenest, whose judgment is most sound, is the man who is

368 BODY CONTROL AND HABIT FORMATION

most likely to succeed. The paralyzing effect of alcohol upon the
nerve centers must place the drinker at a disadvantage. In a
hundred ways, the drinker sooner or later feels the handicap that
the habit of drink has imposed upon him. Many corporations,
notably several of our greatest railroads (the Pennsylvania and
the New York Central Railroad among them), refuse to employ
any but abstainers in positions of trust. Few persons know the
number of railway accidents due to the uncertain eye of some en
gineer who mistook his signal, or the hazy inactivity of the brain
of some train dispatcher who, because of drink, forgot to send the
telegram that was to hold the train from wreck. In business and
in the professions, the story is the same. The abstainer wins out
over the drinking man.

Effect of Alcohol on Ability to do Work. In Physiological
Aspects of the Liquor Problem, Professor Hodge, formerly of Clark
University, describes many of his own experiments showing the
effect of alcohol on animals. He trained four selected puppies to
recover a ball thrown across a gymnasium. To two of the dogs
he gave food mixed with doses of alcohol, while the others were
fed normally. The ball was thrown 100 feet as rapidly as recov
ered. This was repeated 100 times each day for fourteen suc
cessive days. Out of 1400 times the dogs to which alcohol had
been given brought back the ball only 478 times, while the others
secured it 922 times.

Dr. Parkes experimented with two gangs of men, selected to be as
nearly similar as possible, in mowing. He found that with one
gang abstaining from alcoholic drinks and the other not, the ab
staining gang could accomplish more. On transposing the gangs,
the same results were repeatedly obtained. Similar results were
obtained by Professor Aschaffenburg of Heidelberg University,
who found experimentally that men " were able to do 15 per cent
less work after taking alcohol."

Recently many experiments along the same lines have been
made. In typewriting, in typesetting, in bricklaying, or in the
highest type of mental work the result is the same. The quality
and quantity of work done on days when alcohol is taken is less
than on days when no alcohol is taken.

BODY CONTROL AND HABIT FORMATION 369

The Relation of Alcohol to Efficiency. We have already seen
that work is neither so well done nor is as much accomplished by
drinkers as by non-drinkers.

A Massachusetts shoe manufacturer told a recent writer on
temperance that in one year his firm lost over $5000 in shoes
spoiled by drinking men, and that he had himself traced these
spoiled shoes to the workmen who, through their use of alcoholic
liquors, had thus rendered themselves incapable. This is a serious
handicap to our modern factory system, and explains why so many
factory towns and cities are strongly favoring a policy of " No
license " in opposition to the saloons.

" It is believed that the largest number of accidents in shops and
mills takes place on Monday, because the alcohol that is drunk
on Sunday takes away the skill and attentive care of the work
man. To prove the truth of this opinion, the accidents of the
building trades in Zurich were studied during a period of six
years, with the result shown by this table " :

(From Tolman, Hygiene for the Worker.)
Shaded, non-alcoholic ; black, alcoholic, accidents.

Another relation to efficiency is shown by the following chart.
During the week the curve of working efficiency is highest on
Friday and lowest on Monday. The number of accidents were also
least on Friday and greatest on Monday. Lastly the assaults were
fewest in number on Friday and greatest on Sunday and Monday.
The moral is plain. Workingmen are apt to spend their week's
wages freely on Saturday. Much of this goes into drink, and as a
result comes crime on Sunday because of the deadened moral and

HUNTER, CIV. BI. 24

370 BODY CONTROL AND HABIT FORMATION

7
6

5'
4
3

MQN.TUE5.WED.THUR.TR1. SAT. 5UN

ssaul

Notice that the curve of efficiency is lowest on Monday and that crimes and
accidents are most frequent on Sunday and Monday. Account for this.

mental condition of the drinker, and loss of efficiency on Monday,
because of the poisonous effects of the drug.

Effect of Alcohol upon Duration of Life. Still more serious is
the relation of alcohol as a direct cause of disease (see table).

It is as yet quite impossible, in the United States at least, to tell
just how many deaths are brought about, directly or indirectly, by
alcohol. Especially is this true in trying to determine the number
of cases of deaths from disease promoted by alcohol. In Switzer
land provision is made for learning these facts, and the records of
that country throw some light on the subject.

Dr. Rudolph Pfister made a study of the records of the city of
Basle for the years 1892-1906, finding the percentage of deaths in
which alcohol had been reported by the attending physician as one
cause of death. He found that 18.1 per cent of all deaths of men

BODY CONTROL AND HABIT FORMATION 371

between 40 and 50 years of age were caused, in part at least, by
alcohol, and this at what should be the most active period in a
man's life, the time when he is most needed by his family and
community. Taking all ages between 20 and 80, he found that
alcohol was one cause of death in one man in every ten who died.
Another study was made by a certain doctor in Sweden, from
records of 1082 deaths occurring in his own practice and the local
hospital. No case was counted as alcoholic of which there was the
slightest doubt. Of deaths of adult men, 18 in every 100 were
due, directly or indirectly, to alcoholism. In middle life, between
the ages of 40 and 50, 29 ; and between 50 and 60 years of age, 25.6
out of every 100 deaths had alcohol as one cause, thus agreeing

15721 17418

ALCOHOLISM + ALCOHOLIC LIVER CIRRHOSIS 33,138

TYPHOID

SMALLPOX

with other statistics we have been quoting. From the Metropolitan,
Vol. XXV, Number 11.

The Relation of Alcohol to Crime. A recent study of more
than 2500 habitual users of alcohol showed that over 66 per cent had
committed crime. Usually the crimes had been done in saloons
or as a result of quarrels after drinking. Of another lot of 23,581
criminals questioned, 20,070 said that alcohol had led them to
commit crime.

The Relation of Alcohol to Pauperism. We have already
spoken of the Jukes family. These and many other families of a
similar sort are more or less directly a burden upon the state.
Alcohol is in part at least responsible for the condition of such
families. Alcohol weakens the efficiency and moral courage, and
thus leads to begging, pauperism, petty stealing or worse, and ul-

372 BODY CONTROL AND HABIT FORMATION

PERCENTAGE.
4O 50

The proportion of crime due to alcohol is shown in black.

timately to life in some public institution. In Massachusetts, of
3230 inmates of such institutions, 66 per cent were alcoholics.

The Relation of Alcohol to Heredity. Perhaps the gravest
side of the alcohol question lies here. If each one of us had only
himself to think of, the question of alcohol might not be so serious.
But drinkers may hand down to their unfortunate children ten
dencies toward drink as well as nervous diseases of various sorts ;
an alcoholic parent may beget children who are epileptic, neu
rotic, or even insane.

In the State of New York there are at the present time some
30,000 insane persons in public and private hospitals. It is be
lieved that about one fifth of them, or 6000 patients, owe their
insanity to alcohol used either by themselves or by their parents.
In the asylums of the United States there are 150,000 insane people.
Taking the same proportions as before, there are 30,000 persons
in this country whom alcohol has made or has helped to make
insane. This is the most terrible side of the alcohol problem.

REFERENCE READING
ELEMENTARY

Hunter, Laboratory Problems in Civic Biology. American Book Company.

Overton, General Hygiene. American Book Company.

The Gulick Hygiene Series, Emergencies, Good Health, The Body at Work, Control

of Body and Mind. Ginn and Company.
Ritchie, Human Physiology. World Book Company.
Hough and Sedgwick, The Human Mechanism. Ginn and Company.

XXIV. MAN'S IMPROVEMENT OF HIS ENVIRONMENT

Problems. How may we improve our home conditions of
living?

How may ive help improve our conditions at school?
How does the city care for the improvement of our environ
ment ?

(a) In inspection of buildings, etc.
(6) In inspection of food supplies.

(d) In care of water supplies.
(e~) In disposal of wastes.
(/) In care of public health.

LABORATORY SUGGESTIONS

Home exercise. How to ventilate my bedroom.

Demonstration. Effect of use of duster and damp cloth upon bacteria
in schoolroom.

Home exercise. Luncheon dietaries.

Home exercise. Sanitary map of my own block.

Demonstration. The bacterial content of milk of various grades and
from different sources.

Demonstration. Bacterial content of distilled water, rain water, tap
water, dilute sewage.

Laboratory exercise. Study of board of health tables to plot curves
of mortality from certain diseases during certain times of year.

The Purpose of this Chapter. In the preceding chapters we
have traced the lives of both plants and animals within their own
environment. We have seen that man, as well as plants and other
animals, needs a favorable environment in order to live in comfort
and health. It will be the purpose of the following pages first to
show how we as individuals may better our home environment,
and secondly, to see how we may aid the civic authorities in the
betterment of conditions in the city in which we live.

373

374 MAN'S IMPROVEMENT OF HIS ENVIRONMENT

How I should ventilate my bed
room.

Home Conditions. The Bedroom. We spend about one
third of our total time in our bedroom. This room, therefore,
deserves more than passing attention. First of all, it should have

good ventilation. Two windows
make an ideal condition, especially
if the windows receive some sun.
Such a condition as this is mani
festly impossible in a crowded city,
where too often the apartment
bedrooms open upon narrow and
ill-ventilated courts. Until com
paratively recent time, tenement
houses were built so that the bed
rooms had practically no light or
air ; now, thanks to good tenement-
house laws, wide airshafts and larger windows are required by
statute.

Care of the Bedroom. Since sunlight cannot always be ob
tained for a bedroom, we must so care for and furnish the room
that it will be difficult for germs to grow there. Bedroom furni
ture should be light and easy to clean, the bedstead of iron, the
floors painted or of hardwood. No hangings should be allowed
at the windows to collect dust, nor should carpets be allowed for
the same reason. Rugs on the floor may easily be removed when
cleaning is done. The furniture and woodwork should be wiped
with a damp cloth every day. Why a damp cloth? In certain
tenements in New York City, tuberculosis is believed to have been
spread by people occupying rooms in which a previous tenant has
had tuberculosis. A new tenant should insist on a thorough clean
ing of the bedrooms and removal of old wall paper before occu
pancy.

Sunlight Important. In choosing a house in the country we
would take a location in which the sunlight was abundant. A
shaded location might be too damp for health. Sunlight should
enter at least some of the rooms. In choosing an apartment we
should have this matter in mind, for, as we know, germs cannot
long exist in sunlight.

MAN'S IMPROVEMENT OF HIS ENVIRONMENT 375

[.MM I 6.. ..it J V- & 1^

|. l|IUi HI U L {| I * I4I*>< ^d
I .....tti--.. Jl C.i.i. . . t.i.!3

ESSEX ST.

\ \ | I ... I I. q L _a_ M J

NORFOLK ST.

P"*" 1 3 ri]r.'""M p"

i .Al J [ .. T *ff) U. > I

C M.;J If -"".I

pa -ri

RIDGE ST.

l..t; a r..... I

PITT ST.

WLLETT ST.^
3HER*|FF ST.

COLUMBIA ST.

ri**tti** - i LiJ:

! - : a

li inn nji i L"- "J!:"!| I .' I

This map shows how cases of tuberculosis are found recurring in the same locality
and in the same houses year after year. Each black dot is one case of tubercu
losis.

Heating. Houses in the country are often heated by open
fires, stoves or hot-air furnaces, all of which make use of heated
currents of air to warm the rooms. But in the city apartments,
usually pipes conduct steam or hot water from a central plant to our
rooms. The difficulty with this system is that it does not give us

376 MAN'S IMPROVEMENT OF HIS ENVIRONMENT

fresh air, but warms over the stale air in a room. Steam causes
our rooms to be too warm part of the time, and not warm enough
part of the time. Thus we become overheated and then take cold
by becoming chilled. Steam heat is thus responsible for much
sickness.

Lighting. Lighting our rooms is a matter of much importance.
A student lamp, or shaded incandescent light, should be used for
reading. Shades must be provided so that the eyes are protected
from direct light. Gas is a dangerous servant, because it contains
a very poisonous substance, carbon monoxide. "It is estimated
that 14 per cent of the total product of the gas plant leaks into the
streets and houses of the cities supplied." This forms an unseen
menace to the health in cities. Gas pipes, and especially gas cocks,
should be watched carefully for escaping gas. Rubber tubing
should not be used to conduct gas to movable gas lamps, because
it becomes worn and allows gas to escape.

Insects and Foods. In the summer our houses should be pro
vided with screens. All food should be carefully protected from

During the summer all food should be protected from flies. Why ?

flies. Dirty dishes, scraps of food, and such garbage should be
quickly cleaned up and disposed of after a meal. Insect powder
(pyrethrum) will help keep out "croton bugs" and other undesir
able household pests, but cleanliness will do far more. Most
kitchen pests, as the roach, simply stay with us because they find
dirt and food abundant.

MAN'S IMPROVEMENT OF HIS ENVIRONMENT 377

Use of Ice. Food should be properly cared for at all times, but
especially during the summer. Iceboxes are a necessity, especially
where children live, in order to keep milk fresh. A dirty icebox
is almost as bad as none at all, because food will decay or take on
unpleasant odors from other foods.

Disposal of Wastes. In city houses the disposal of human
wastes is provided for by
a city system of sewers.
The wastes from the kit
chen, the garbage, should
be disposed of each day.
The garbage pail should
be frequently sterilized by
rinsing it with boiling
water. Plenty of lye or
soap should be used. Re
member that flies frequent
the uncovered garbage
pail, and that they may
next walk on your food.
Collection and disposal of
garbage is the work of the
municipality.

School Surroundings.
How to Improve Them.
From five to six hours a
day for forty weeks is
spent by the average boy

or girl in the schoolroom. It is part of our environment and should
therefore be considered as worthy of our care. Not only should
a schoolroom be attractive, but it should be clean and sanitary.
City schools, because of their locations, of the sometimes poor jani
torial service, and especially because of the selfishness and care
lessness of children who use them, may be very dirty and unsani
tary. Dirt and dust breed and carry bacteria. Plate cultures
show greatly increased numbers of bacteria to be in the air when
pupils are moving about, for then dust, bearing bacteria, is stirred up

The wrong and the right kind of garbage cans.

378 MAN'S IMPROVEMENT OF HIS ENVIRONMENT

and circulated through the air. Sweeping and dusting with dry
brooms or feather dusters only stirs up the dust, leaving it to settle
in some other place with its load of bacteria. Professor Hodge
tells of an experience in a school in Worcester, Mass. A health
brigade was formed among the children, whose duty was to clean
the rooms every morning by wiping all exposed surface with a damp

The culture (A) was exposed to the air of a dirty street in the crowded purt of
Manhattan. (B) was exposed to the air of a well-cleaned and watered street in
the uptown residence portion. Which culture has the more colonies of bac
teria ? How do you account for this ?

cloth. In a school of 425 pupils not a single case of contagious
diseases appeared during the entire year. Why not try this in
your own school ?

Unselfishness the Motto. Pupils should be unselfish in the
care of a school building. Papers and scraps dropped by some
careless boy or girl make unpleasant the surroundings for hundreds
of others. Chalk thrown by some mischievous boy and then
tramped underfoot may irritate the lungs of a hundred innocent
schoolmates. Colds or worse diseases may be spread through
the filthy habits of some boys who spit in the halls or on the
stairways.

Lunch Time and Lunches. If you bring your own lunch to
school, it should be clean, tasty, and well balanced as a ration. In
most large schools well-managed lunch rooms are part of the school

MAN'S IMPROVEMENT OP HIS ENVIRONMENT 379

A sensible lunch box, sanitary
and compact.

equipment, and balanced lunches can be obtained at low cost.

Do not make a lunch entirely from cold food, if hot can be obtained.

Do not eat only sweets. Ice cream is a good food, if taken with

something else, but be sure of your ice

cream. " Hokey pokey " cream, tested

in a New York school laboratory,

showed the presence of many more

colonies of bacteria than good milk

would show. Above all, be sure the

food you buy is clean. Stands on the

street, exposed to dust and germs,

often sell food far from fit for human

consumption.

If you eat yoirr lunch on the street

near your school, remember not to

scatter refuse. Paper, bits of lunch,

and the like scattered on the streets around your school show lack

of school spirit and lack of civic pride. Let us learn above all

other things to be good citizens.

Inspection of Factories, Public Buildings, etc. It is the duty

of a city to inspect the condition
of all public buildings and espe
cially of factories. Inspection
should include, first, the super
vision of the work undertaken.
Certain trades where grit, dirt,
or poison fumes are given off
are dangerous to human health,
hence care for the workers be
comes a necessity. Factories
should also be inspected as to
cleanliness, the amount of air
space per person employed,
ventilation, toilet facilities, and

Dust exhausts on grinding wheels protect proper fi re protection. Tene-
lungs of the workmen.

ment inspection should be
thorough and should aim to provide safe and sanitary homes.

380 MAN'S IMPROVEMENT OF HIS ENVIRONMENT

Inspection of Food Supplies. In a city certain regulations for
the care of public supplies are necessary. Foods, both fresh and
preserved, must be inspected and rendered safe for the thousands
of people who are to use them. All raw foods exposed on stands
should be covered so as to prevent insects or dust laden with
bacteria from coming in contact with them. Meats must be in
spected for diseases, such as tuberculosis in beef, or trichinosis in
pork. Cold storage plants must be inspected to prevent the keep
ing of food until it becomes unfit for use. Inspection of sanitary
conditions of factories where products are canned, or bakeries
where foods are prepared, must be part of the work of a city in
caring for its citizens.

Care of Raw Foods. Each one of us may cooperate with the
city government by remembering that fruits arid vegetables can
be carriers of disease, especially if they are sold from exposed stalls
or carts and handled by the passers-by. All vegetables, fruits, or
raw foods should be carefully washed before using. Spoiled or
overripe fruit, as well as meat which is decayed, is swarming with
bacteria and should not be used.

An interesting exercise would be the inspection of conditions
in your own home block. Make a map showing the houses on the
block. Locate all stores, saloons, factories, etc. Notice any cases
of contagious disease, marking this fact on the map. Mark all
heaps of refuse in the street, all uncovered garbage pails, any street

stands that sell uncovered
fruit, and any stores with
an excessive number of
flies.

In addition to food in
spection, two very impor
tant supplies must be ren
dered safe by a city for its
citizens. These are milk
and water.

Care in Production of
Milk. Milk when drawn

Clean cows m clean barns with clean milkers and
clean milk pails means clean milk in the city. from a healthy COW should

MAN'S IMPROVEMENT OF HIS ENVIRONMENT 381

be free from bacteria. But immediately on reaching the air it
may receive bacteria from the air, from the hands of the person
who milks the cows, from the pail, or from the cow herself. Cows
should, therefore, be milked in surroundings that are sanitary,
the milkers should wear clean garments, put on over their ordinary
clothes at milking time, while pails and all utensils used should
be kept clean. Especially the surface exposed on the udder from
which the milk is drawn should be cleansed before milking.

Most large cities now send inspectors to the farms from which
milk is supplied. Farms that do not accept certain standards of
cleanliness are not allowed to have their milk become part of the
city supply.

Tuberculosis and Milk. It is recognized that in some Euro
pean countries from 30 to 40 per cent of all cattle have tuberculosis.
Many dairy herds in this country are also infected. It is alsc
known that the tubercle bacillus of cattle and man are much alike
in form and action and that probably the germ from cattle would
cause tuberculosis in man. Fortunately, the tuberculosis germ
does not grow in milk, so that even if milk from tubercular cattle
should get into our supply, it would be diluted with the milk of
healthy cattle. In order to protect our milk supply from these
germs it would be necessary to kill all tubercular cattle (almost an
impossibility) or to pasteurize our milk so as to kill the germs in it.

Other Disease Germs in Milk. We have already shown
how typhoid may be spread through milk. Usually such out
breaks may be traced to a single case of typhoid, often a person
who is a " typhoid carrier," i.e. one who may not suffer from the
effects of the disease, but who carries the germs in his body, spread
ing them by contact. A recent epidemic of typhoid in New York
City was traced to a single typhoid carrier on a farm far from the
city. Sometimes the milk cans may be washed in contaminated
water or the cows may even get the germs on their udders by wad
ing in a polluted stream. Diphtheria, scarlet fever, and Asiatic
cholera are also undoubtedly spread through milk supplies. Milk
also plays a very important part in the high death rate from diar-
rheal diseases among young children in warm weather. Why?

Grades of Milk in a City Supply. Milk which comes to a city

382 MAN'S IMPROVEMENT OF HIS ENVIRONMENT

A diagram to show how typhoid may be spread in a city through an infected milk
supply. The black spots in the blocks mean cases of typhoid. A, a farm
where typhoid exists ; the dashes in the streets represent the milk route. B is
a second farm which sends part of its milk to A ; the milk cans from B are
washed at farm A and sent back to B. A few cases of typhoid appear along
B's milk route. How do you account for that ?

may be roughly placed in three different classes. The best milk,
coming from farms where the highest sanitary standards exist,
where the cows are all tubercular tested, where modern appliances
for handling and cooling the milk exist, is known as certified or, in
New York City, grade A milk. Most of the milk sold, however,
is not so pure nor is so much care taken in handling it. Such milk,
known in New York as grade B milk, is pasteurized before de
livery, and is sold only in bottles. A still lower grade of milk
(dipped milk) is sold direct from cans. It is evident that such
milk, often exposed to dust and other dirt, is unfit for any purpose
except for cooking. It should under no circumstances be used for
children, A regulation recently made by the New York City

MAN'S IMPROVEMENT OF HIS ENVIRONMENT 383

Department of Health states that milk sold " loose " in restaurants,
lunch-rooms, soda fountains, and hotels must be pasteurized.

Care of a City Milk Supply. Besides caring for milk in its
production on the farm, proper transportation facilities must be
provided. Much of the milk used in New York City is forty-eight
hours old before it reaches the consumer. During shipment it
must be kept in refrigerator cars, and during transit to customers it
should be iced. Why? All but the highest grade milk should be
pasteurized. Why? Milk should be bottled by machinery if
possible so as to insure no personal contact ; it should be kept in
clean, cool places ; and no milk should be sold by dipping from
cans. Why is this a method of dispensing impure milk?

Care of Milk in the Home. Finally, milk at home should re
ceive the best of care. It should be kept on ice and in covered
bottles, because it readily
takes up the odors of other
foods. If we are not cer
tain of its purity or keep
ing qualities, it should be
pasteurized at home.
Why?

Water Supplies. One
of the greatest assets to
the health of a large city
is pure water. By pure
water we mean water free
from all organic impurities,
including germs. Water
from springs and deep
driven wells is the safest
water, that from large
reservoirs next best, while
water that has drainage
in it, river water for ex- XT v .

New York City is spending $350,000,000 to

ample, IS very unsafe. have a pure and abundant water supply.

TViP wot PT-G fmrn rloor This is the tunnel which will bring the

eep water from the Catskill Mountains to New

wells or springs if properly York City.

384 MAN'S IMPROVEMENT OF HIS ENVIRONMENT

protected will contain no bacteria. Water taken from protected
streams into which no sewage flows will have but few bacteria, and
these will be destroyed if exposed to the action of the sun and the
constant aeration (mixing with oxygen) which the surface water
receives in a large lake or reservoir. But water taken from a river

ORIGINAL CASES MM <
NORTH CHELMSFORQ

RESULTING CA .f' ** * 9* *** /' V.

IN LOWELL **> Lr\

The city of Lowell in 1891 took its water without filtering, i.e. from the Merrimack

River at the point shown on the map.
Typhoid fever broke out in North Chelmsford and about two weeks later cases

began to appear in Lowell until a great epidemic occurred. Explain this

outbreak. Each black dot is a case of typhoid.

into which the sewage of other towns and cities flows must be
filtered before it is fit for use.

Typhoid fever germs live in the food tube, hence the excreta of
a typhoid patient will contain large numbers of germs. In a city
with a system of sewage such germs might eventually pass from
the sewers into a river. Many cities take their water supply
directly from rivers, sometimes not far below another large town.
Such cities must take many germs into their water supply. Many
cities, as Cleveland and Buffalo, take their water from lakes into
which their sewage flows. Others, as Albany, Pittsburgh, and Phila
delphia, take their drinking water directly from rivers into which

MAN'S IMPROVEMENT OF HIS ENVIRONMENT 385

Filter beds at Albany, N. Y.

sewage from cities above them on the river has flowed. Filter
ing such water by means of passing the water through settling
basins and sand filters removes about 98 per cent of the germs. The
result of drinking unfiltered and filtered water in certain large cities
is shown graph
ically at right.
In cities which
drain their sewage
into rivers and
lakes, the question
of sewage disposal
is a large one, and
many cities now
have means of dis
posing of their sew
age in some man
ner as to render it
harmless to their
neighbors.

Railroads are often responsible for carrying typhoid and spread
ing it. It is said that a recent outbreak of typhoid in Scranton,
Pa., was due to the fact that the excreta from a typhoid patient
traveling in a sleeping car was washed by rain into a reservoir near
which the train was passing. Railroads are thus seen to be great
open sewers. A sanitary car toilet is the only remedy.

HUNTER, CIV. BI. 25

Cases of typhoid per 100,000 inhabitants before filtering
water supply (solid) and after (shafted) in A t Water-
town, N. Y.; B, Albany, N. Y.; C, Lawrence, Mass.:
D, Cincinnati, Ohio. What is the effect Of filtering
the water supply ?

386 MAN'S IMPROVEMENT OF HIS ENVIRONMENT

This chart shows that during a cholera epidemic in 1892 there were hundreds
of cases of cholera in Hamburg, which used unfiltered water from the Elbe,
but in adjoining Altona, where filtered water was used, the cases were
very few.

Sewage Disposal. Sewage disposal is an important sanitary
problem for any city. Some cities, like New York, pour their
sewage directly into rivers which flow into the ocean. Conse
quently much of the liquid which bathes the shores of Manhattan
Island is dilute sewage. Other cities, like Buffalo or Cleveland, send
their sewage into the lakes from which they obtain their supply of
drinking water. Still other cities which are on rivers are forced to
dispose of their sewage in various ways. Some have a system of

Stone filter beds in a sewage disposal plant.

MAN'S IMPROVEMENT OF HIS ENVIRONMENT 387

filter beds in which the solid wastes are acted upon by the bacteria
of decay, so that they can be collected and used as fertilizer.
Others precipitate or condense the solid materials in the sewage
and then dispose of it. Another method is to flow the sewage over
large areas of land, later using this land for the cultivation of crops.
This method is used by many small European cities.

The Work of the Department of Street Cleaning. In any
city a menace to the health of its citizens exists in the refuse and
garbage. The city streets, when dirty, contain countless millions
of germs which have come from decaying material, or from people
ill with disease. In most
large cities a department
of street cleaning not only
cares for the removal of
dust from the streets, but
also has the removal of
garbage, ashes, and other
waste as a part of its
work. The disposal of

Collecting ashes.

solid wastes is a tremen
dous task. In Manhattan the dry wastes are estimated to be
1,000,000 tons a year in addition to about 175,000 tons of garbage.
Prior to 1895 in the city of New York garbage was not separated
from ashes ; now the law requires that garbage be placed in separate
receptacles from ashes. Do you see why? The street-cleaning
department should be aided by every citizen ; rules for the separa
tion of garbage, papers, and ashes should be kept. Garbage and
ash cans should be covered. The practice of upsetting ash or gar
bage cans is one which no young citizen should allow in his neigh
borhood, for sanitary reasons. The best results in summer street
cleaning are obtained by washing or flushing the streets, for thus
the dirt containing germs is prevented from getting into the air.
The garbage is removed in carts, and part of it is burned in huge
furnaces. The animal and plant refuse is cooked in great tanks ;
from this material the fats are extracted, and the solid matter is
sold for fertilizer. Ashes are used for filling marsh land. Thus
the removal of waste matter may pay for itself in a large city.

388 MAN'S IMPROVEMENT OF HIS ENVIRONMENT

An Experiment in Civic Hygiene. During the summer of 1913
an interesting experiment on the relation of flies and filth to disease
was carried on in New York City by the Bureau of Public Health
and Hygiene of the New York Association for improving the con
dition of the poor.
Two adjoining blocks
were chosen in a
thickly populated part
of the Bronx near a
number of stables
which were the
sources of great num
bers of flies. In one
block all houses were
screened, garbage pails
were furnished with
covers, refuse was re
moved and the sur-
s^lSM^.^ I ' , ii*w**.^. ,. ,

roundmgs made as

sanitary as possible.
In the adjoining block
conditions were left
unchanged. During
the summer as flies
began to breed in the

HpKipft|i| ---1- manure heaps near the

stables all manure was
disinfected. Thus the
breeding of flies was
checked. The cam
paign of education was
continued during the summer by means of moving pictures,
nurses, boy scouts, and school children who became interested.

At the end of the summer it was found that there had been a
considerable decrease in the number of cases of fly-carried diseases
and a still greater decrease in the total days of sickness (especially
of children) in the screened and sanitary block. The table and

The upper picture shows the stables where millions
of flies were bred ; the lower picture, the disinfec
tion of manure so as to prevent the breeding of
flies.

MAN'S IMPROVEMENT OF HIS ENVIRONMENT 389

pictures speak for themselves. If such a small experiment shows
results like this, then what might a general cleanup of a city show ?
Public Hygiene. Although it is absolutely necessary for each
individual to obey the laws of health if he or she wishes to keep
well, it has also be
come necessary, espe
cially in large cities,
to have general super
vision over the health
of people living in a
community. This is
done by means of a
department or board
of health. It is the
function of this de
partment to care for
public health. In ad
dition to such a body
in cities, supervision
over the health of its
citizens is also exer
cised by state boards
of health. But as yet
the government of the
United States has not
established a Bureau
of Health, important
as such a bureau

Would be. In the upper picture a little girl can be seen dump-

The Functions of a in ^ garbage from the fire escape. She was a

foreigner and knew no better. The picture below
City Board Of Health. shows the result of such garbage disposal.

The administration

of the Board of Health in New York City includes a number of
divisions, each of which has a different work to do. Each is in
itself important, and, working together, the entire machine provides
ways and means for making the great city a safe and sanitary
place in which to live. Let us take up the work of each division

390 MAN'S IMPROVEMENT OF HIS ENVIRONMENT

of the health board in order to find out how we may cooperate with
them.

The Division of Infectious Diseases. Infectious diseases are
chiefly spread through personal contact. It is the duty of a gov
ernment to prevent a person having such a disease from spreading
it broadcast among his neighbors. This can be done by quarantine
or isolation of the person having the disease. So the board of
health at once isolates any case of disease which may be communi-

CLEANED-UPAREA

Comparison of cases of illness during the summer of 1913 in two city blocks, one
clean and the other dirty. What are your conclusions ?

cated from one person to another. No one save the doctor or
nurse should enter the room of the person quarantined. After
the disease has run its course, the clothing, bedding, etc., in the
sick room is fumigated. This is usually done by the board of
health. Formaldehyde in the form of candles for burning or in a
liquid form is a good disinfectant. In disinfecting the room should
be tightly closed to prevent the escape of the gas used, as the
object of the disinfection is to kill all the disease germs left in the
room. In some cases of infectious disease, as scarlet fever, it is
found best to isolate the patients in a hospital used for that pur
pose. Examples of the most infectious diseases are measles,
scarlet fever, whooping cough, and diphtheria.

Immunity. In the prevention of germ diseases we must fight
the germ by attacking the parasites directly with poisons that will
kill them (such poisons are called germicides or disinfectants), and
we must strive to make the persons coming in contact with the
disease unlikely to take it. This insusceptibility or immunity may

MAN'S IMPROVEMENT OF HIS ENVIRONMENT 391

be either natural or acquired. Natural immunity seems to be in
the constitution of a person, and may be inherited. Immunity
may be acquired by means of such treatment as the antitoxin
treatment for diphtheria. This treatment, as the name denotes,
is a method of neutralizing the poison (toxin) caused by the bacteria
in the system. It was discovered a few years ago by a German,
Von Behring, that the serum of the blood of an animal immune
to diphtheria is capable of neutralizing the poison produced by
the diphtheria-causing bacteria. Horses are rendered immune by
giving them the diphtheria toxin in gradually increasing doses.

Antitoxin for diphtheria prepared by the New York Board of Health.

The serum of the blood of these horses is then used to inoculate the
patient suffering from or exposed to diphtheria, and thus the dis
ease is checked or prevented altogether by the antitoxin injected
into the blood. The laboratories of the board of health prepare
this antitoxin and supply it fresh for public use.

It has been found from experience in hospitals that deaths from
diphtheria are largely preventable by early use of antitoxin.
When antitoxin was used on the first day of the disease no deaths
took place. If not used until the second day, 5 deaths occurred
in every hundred cases, on the third day 11 deaths, on the 4th
day 19 deaths, and on the 5th day 20 deaths out of every hun
dred cases. It is therefore advisable, in a suspected case of
diphtheria, to have antitoxin used at once to prevent serious
results.

Vaccination. Smallpox was once the most feared disease in
this country ; 95 per cent of all people suffered from it. As late

392 MAN'S IMPROVEMENT OF HIS ENVIRONMENT

as 1898, over 50,000 persons lost their lives annually in Russia
from this disease. It is probably not caused by bacteria, but by
a tiny animal parasite. Smallpox has been brought under abso
lute control by vaccination, the inoculation of man with the
substance (called virus) which causes cowpox in a cow. Cowpox is
like a mild form of smallpox, and the introduction of this virus
gives complete immunity to smallpox for several years after vac
cination. This immunity is caused by the formation of a ger-
micidal substance in the blood, due to the introduction of the
virus. Another function of the board of health is the prepara
tion and distribution of vaccine (material containing the virus
of cowpox).

Rabies (Hydrophobia). This disease, which is believed to be
caused by a protozoan parasite, is communicated from one dog to
another in the saliva by biting. In a similar manner it is trans
ferred to man. The great French bacteriologist, Louis Pasteur,
discovered a method of treating this disease so that when taken
early at the time of the entry of the germ into the body of man,
the disease can be prevented. In some large cities (among them
New York) the board of health has established a laboratory where
free treatment is given to all persons bitten by dogs suspected of
having rabies.

Vaccination against Typhoid. Typhoid fever has within the
past five years received a new check from vaccination which has
been introduced into our army and which is being used with good
effect by the health departments of several large cities.

The following figures show the differences between number of
cases and mortality in the army in 1898 during the war with Spain
and in 1911 during the concentration of certain of our troops at
San Antonio, Texas.

1898 2nd Division, 7th Army Corps, Jacksonville, Florida.
June-October, 1898

Mean strength, 10,759.

Cases of typhoid certain and probable, 2693.

Death from typhoid, 258.

Death from all diseases, 281.

MAN'S IMPROVEMENT OF HIS ENVIRONMENT 393

Manceuver Division, San Antonio, Texas. March 10- July 11,

1911.

Mean strength, 12,801.
Cases of typhoid, 1.
Death from typhoid, 0.
Deaths all diseases, 11.

During this period there were 49 cases of typhoid and 19 deaths
in the near-by city of San Antonio. But in camp, where vaccination

Comparison of cases of and death from typhoid in 1898 and 1911.
learned about combating typhoid since 1898 ?

What have we

for typhoid was required, all were practically immune. In the army
at large, since typhoid vaccination has been practiced, 1908-1909,
the death rate from typhoid has dropped from 2.9 per 1000 to
.03 per 1000, a wonderful record when we remember that during
the Spanish-American War 86 per cent of the deaths in the army
were from typhoid fever.

How the Board of Health fights Tuberculosis. Tuberculosis,
which a few years ago killed fully one seventh of the people who
died from disease in this country, now kills less than one tenth.
This decrease has been largely brought about because of the treat
ment of the disease. Since it has been proved that tuberculosis if
taken early enough is curable, by quiet living, good food, and
plenty of fresh air and light, we find that numerous sanitaria have
come into existence which are supported by private or public
means. At these sanitaria the patients live out of doors, especially
sleep in the air, while they have plenty of nourishing food and
little exercise. The department of health of New York City main-

394 MAN'S IMPROVEMENT OF HIS ENVIRONMENT

tains a sanitarium at Otisville in the Catskill Mountains. Here
people who are unable to provide means for getting away from the

The best cures for tuberculosis are rest, plenty of fresh out-of-door air, and

wholesome food.

city are cared for at the city's expense and a large percentage of
them are cured. In this way and by tenement house laws which
require proper air shafts and window ventilation in dwellings, by
laws against spitting in public places, and in other ways, the boards
of health in our towns and cities are waging war on tuberculosis.

A sanitarium for tuberculosis. Notice the outdoor sleeping rooms.

MAN'S IMPROVEMENT OF HIS ENVIRONMENT 395

Ex-President Roosevelt said, in one of his latest messages to
Congress :

" There are about 3,000,000 people seriously ill in the United
States, of whom 500,000 are consumptives. More than half of
this illness is preventable. If we count the value of each life lost
at only $1700 and reckon the average earning lost by illness at
$700 a year for grown men, we find that the economic gain from
mitigation of preventable disease in the United States would ex
ceed $1,500,000,000 a year. This gain can be had through medical
investigation and practice, school and factory hygiene, restriction
of labor by women and children, the education of the people in
both public and private hygiene, and through improving the effi
ciency of our health service, municipal, state, and national."

Work of the Division of School and Infant Hygiene. Besides
the work of the division of infectious disease, the division of sani
tation, which regulates the general sanitary conditions of houses
and their surroundings and the division of inspection, which looks
after the purity and conditions of sale and delivery of milk and
foods, there is another department which most vitally concerns
school children. This is the division of school and infant hygiene.
The work of this department is that of the care of the children of
the city. During the year 1912, 279,776 visits were made to the
homes of school children of the city of New York by inspectors
and nurses. Besides this, thousands of children in school were
cared for and aided by the city.

Adenoids. Many children suffer needlessly from adenoids,
growths in the back of the nose or mouth which prevent sufficient
oxygen being admitted to the lungs. A child suffering from these
growths is known as a " mouth breather " because the mouth is
opened in order to get more air. The result to the child may be a
handicap of deafness, chronic running of the nose, nervousness,
and lack of power to think. His body cells are starving for oxygen.
A very simple operation removes this growth. Cooperation on the
part of the children and parents with the doctors or nurses of the
board of health will do much in removing this handicap from many
young lives.

Eyestrain. Another handicap to a boy or girl is eyestrain.

396 MAN'S IMPROVEMENT OF HIS ENVIRONMENT

Twenty-two per cent of the school children of Massachusetts
were recently found to have defects in vision. Tests for defective
eyesight may be made at school easily by competent doctors, and
if the child or parent takes the advice given to correct this by
procuring proper glasses, a handicap on future success will be
removed.

Decayed Teeth. Decayed teeth are another handicap, cared
for by this division. Free dental clinics have been established in
many cities, and if children will do their share, the chances of their
success in later life will be greatly aided. Boys and girls, if handi
capped with poor eyes or teeth, do not have a fair chance in life's
competition. In a certain school in New York City there were
236 pupils marked " C " in their school work. These children
were examined, and 126 were found to have bad teeth, 54
defective vision, and 56 other defects, as poor hearing, adenoids,
enlarged tonsils, etc. Of these children 185 were treated for
these various difficulties, and 51 did not take treatment. During
the following year's work 176 of these pupils improved from " C "
to " B " or " A ", while 60 did not improve. If defects are such
a handicap in school, then what would be the chances of success
in life outside.

In conclusion : this department of school hygiene deserves the
earnest aid of every young citizen, girl or boy. If each of us
would honestly help by maintaining quarantine in the case of
contagious disease, by observing the rules of the health depart
ment in fumigation, by acting upon advice given in case of eye-
strain, bad teeth, or adenoids, and most of all by observing the
rules of personal hygiene as laid down in this book, the city in
which we live would, a generation hence, contain stronger, more
prosperous, and more efficient citizens than it does to-day.

REFERENCE BOOKS
ELEMENTARY

Hunter, Laboratory Problems in Civic Biology. American Book Company.
Davison, The Human Body and Health. American Book Company.
Gulick Hygiene Series, Town and City. Ginn and Company.
Hough and Sedgwick, The Human Mechanism, Part II. Ginn and Company.
Overton, General Hygiene. American Book Company.

MAN'S IMPROVEMENT OF HIS ENVIRONMENT 397

Richards, Sanitation in Daily Life. Whitcomb and Barrows.

Richmond and Wallach, Good Citizenship. American Book Company.

Ritchie, Primer of Sanitation. World Book Company.

Sharpe, Laboratory Manual of Biology, pages 320-334. American Book Company.

ADVANCED

Allen, Civics and Health. Ginn and Company.

Chapin, Municipal Sanitation in the United States. Snow and Farnham.

Chapin, Sources and Modes of Infection. Wiley and Sons.

Conn, Practical Dairy Bacteriology. Orange Judd Company.

Hough and Sedgwick, The Human Mechanism. Part II. Ginn and Company.

Hutchinson, Preventable Diseases. The Houghton, Mifflin Company.

Morse, The Collection and Disposal of Municipal Waste. Municipal Journal and

Engineer.
Overlock, The Working People, Their Health and How to Protect It. Mass. Health

Book Publishing Co.

Price, Handbook of Sanitation. Wiley and Sons.
Tolman, Hygiene for the Worker. American Book Company.

REPORTS, ETC.

American Health Magazine.

Annual Report of Department of Health, City of New York (and other cities).

Bulletins and Publications of Committee of One Hundred on National Health.

School Hygiene, American School Hygiene Association.

Grinnell, Our Army versus a Bacillus. National Geographic Magazine.

XXV. SOME GREAT NAMES IN BIOLOGY

If we were to attempt to group the names associated with the
study of biology, we would find that in a general way they were
connected either with discoveries of a purely scientific nature or
with the benefiting of man's condition by the application of the
purely scientific discoveries. The first group are necessary in a
science in order that the second group may apply their work. It
was necessary for men like Charles Darwin or Gregor Mendel to
prove their theories before men like Luther Burbank or any of
the men now working in the Department of Agriculture could
benefit mankind by growing new varieties of plants. The dis
covery of scientific truths must be achieved before the men of
modern medicine can apply these great truths to the cure or pre
vention of disease. Since we are most interested in discoveries
which touch directly upon human life, the men of whom this chap
ter treats will be those who, directly or indirectly, have benefited
mankind.

The Discoverers of Living Matter. The names of a number of
men living at different periods are associated with our first knowl
edge of cells. About the middle of the seventeenth century micro
scopes came into use. Through their use plant cells were first
described and pictured as hollow boxes or " cells." But it was
not until 1838 that two German friends, Schleiden and Schwann
by name, working on plants and animals, discovered that both of
these forms of life contained a jellylike substance that later came
to be called protoplasm. Another German named Max Schultz in
1861 gave the name protoplasm to all living matter, and a little later
still Professor Huxley, a famous Englishman, friend and champion
of Charles Darwin, called attention to the physical and chemical
qualities of protoplasm so that it came to be known as the chemical
and physical basis of life.

398

SOME GREAT NAMES IN BIOLOGY

399

Life comes from Life. Another group of men, after years of
patient experimentation, worked out the fact that life comes from
other life. In ancient times it
was thought that life arose
spontaneously; for example,
that fish or frogs arose out of
the mud of the river bottoms,
and that insects came from the
dew or rotting meat. It was
believed that bacteria arose
spontaneously in water, even
as late as 1876, when Professor
Tyndall proved by experiment
the contrary to be true.

As early as 1651 William
Harvey, the court physician of
Charles I of England, showed
that all life came from the egg.
It was much later, however,
that the part played by the
sperm and egg cell in fertiliza
tion was carefully worked out.
It is to Harvey, too, that we

Prof. Tyndall 's experiment to show that if
air containing germs is kept from or
ganic substances, such substances will
not decay. The box is sterilized; like
wise the tubes (t) containing nutrients.
Air is allowed to enter by the tubes (u),
which are so made that dust is pre
vented from entering. A thermometer
(th) records the temperature. The sub
stances in the tubes do not decay, no
matter how favorable the temperature.

owe the beginnings of our
knowledge of the circulation
of the blood. He showed that
blood moved through tubes in the body and that the heart pumped
it. He might be called the father of modern physiology as well
as the father of embryology. A long list of names might be added
to that of Harvey to show how gradually our knowledge of the
working of the human body has been added to. At the present
time we are far from knowing all the functions of the various parts
of the human engine, as is shown by the number of investigators
in physiology at the present time. Present-day problems have
much to do with the care of the human mechanism and with its
surroundings. The solution of these problems will come from ap
plying the sciences of hygiene, preventive medicine, and sanitation.

400

SOME GREAT NAMES IN BIOLOGY

In the preceding chapters of this book we have learned some
thing about our bodies and their care. We have found that man
is able within limitations to control his environment so as to make
it better to live in. All of the scientific facts that have been of
use to man in the control of disease have been found out by men
who have devoted their lives in the hope that their experiments
and their sacrifices of time, energy, and sometimes life itself might
make for the betterment of the human race. Such men were
Harvey, Jenner, Lister, Koch, and Pasteur.

Edward Jenner and Vaccination. The civilized world owes
much to Edward Jenner, the discoverer of vaccination against
smallpox. Born in Berkeley, a little town of Gloucestershire, Eng-

( land, in 1749, as a boy he

showed a strong liking for nat
ural history. He studied medi
cine and also gave much time to
the working out of biological
problems. As early as 1775 he
began to associate the disease
called cowpox with that of
smallpox, and gradually the

idea of inoculation against this
terrible scourge, which killed or
disfigured hundreds of thou
sands every year in England
alone, was worked out and ap
plied. He believed that if the
two diseases were similar, a per
son inoculated with the mild
disease (cowpox) would after a
slight attack of this disease be

immune against the more deadly and loathsome smallpox. It was
not until 1796 that he was able to prove his theory, as at first few
people would submit to vaccination. War at this time was being
waged between France and England, so that the former country,
usually so quick to appreciate the value of scientific discoveries, was
slow to give this method a trial. In spite of much opposition, how-

Edward Jenner, the discoverer of
cination.

SOME GREAT NAMES IN BIOLOGY

401

ever, by the year 1802, vaccination was practiced in most of the
civilized countries of the world. At the present time the death rate
in Great Britain, the home of vaccination, is less than .3 to every
1,000,000 living persons. This shows that the disease is practically
wiped out in England. An interesting comparison with these
figures might be made from the history of the disease in parts of
Russia where vaccination is not practiced. There, thousands of
deaths from smallpox occur annually. During the winter of
1913-1914 an epidemic of smallpox with more than 250 cases
broke out in the city of Niagara Falls. This epidemic appears
to be due to a campaign conducted by people who do not believe
in vaccination. In cities and towns near by, where vaccination
.was practiced, no cases of smallpox occurred. Naturally if oppo
sition to vaccination is found nowadays, Jenner had a much
harder battle to fight in his day. He also had many failures, due
to the imperfect methods of his time. The full worth of his dis
covery was not fully appreciated until long after his death, which
occurred in 1823.

Louis Pasteur. The one man who, in biological science, did
more than any other to directly benefit mankind was Louis Pasteur.

Born in 1822, in the mountains

near the border of northeastern
France, he spent the early part
of his life as a normal boy, fond
of fishing and not very partial
to study. He inherited from
his father, however, a fine char
acter and grim determination,
so that when he became inter
ested in scientific pursuits he
settled down to work with en
thusiasm and energy.

At the age of twenty-five he
became well known throughout
France as a physicist. Shortly
after this he became interested in the tiny plants we call bac
teria, and it was in the field of bacteriology that he became most

HUNTER, CIV. BI. 26

Louis Pasteur.

402 SOME GREAT NAMES IN BIOLOGY

famous. First as professor at Strassburg and at Lille, later as
director of scientific studies in the Ecole Normale at Paris, he
showed his interest in the application of his discoveries to human
welfare.

In 1857 Pasteur showed that fermentation was due to the pres
ence of bacteria, it having been thought up to this time that it
was a purely chemical process. This discovery led to very
practical ends, for France was a great wine-producing country,
and with a knowledge of the cause of fermentation many of the
diseases which spoiled wine were checked.

In 1865-1868 Pasteur turned his attention to a silkworm dis
ease which threatened to wipe out the silk industry of France and
Italy. He found that this disease was caused by bacteria. After
a careful study of the case he made certain recommendations
which, when carried out, resulted in the complete overthrow of the
disease and the saving of millions of dollars to the poor people of
France and Italy.

The greatest service to mankind came later in his life when he
applied certain of his discoveries to the treatment of disease.
First experimenting upon chickens and later with cattle, he proved
that by making a virus (poison) from the germs which caused
certain diseases he could reduce this virus to any desired strength.
He then inoculated the animals with the virus of reduced strength,
giving the inoculated animals a mild attack of the disease, and
found that this made them immune from future attacks. This
discovery, first applied to chicken cholera, laid the foundation for
all future work in the uses of serums, vaccines, and antitoxins.

Pasteur was perhaps the best known through his study of
rabies. The great Pasteur Institute, founded by popular sub
scriptions from all over the world, has successfully treated over
22,000 cases of rabies with a death rate of less than 1 per cent.
But more than that it has been the place where Roux, a fellow
worker with Pasteur, discovered the antitoxin for diphtheria which
has resulted in the saving of thousands of human lives. Here
also have been established the principles of inoculation against
bubonic plague, lockjaw, and other germ diseases.

Pasteur died in 1895 at the age of seventy-three, " the most

SOME GREAT NAMES IN BIOLOGY

403

perfect man in the realm of science/' a man beloved by his coun
trymen and honored by the entire world.

Robert Koch. Another name associated with the battle
against disease germs is that of Robert Koch. Born in Klausthal,
Hanover, in 1843, he later be
came a practicing physician,
and about 1880 was called to
Berlin to become a member of
the sanitary commission and
professor in the school of medi
cine. In 1881 he discovered
the germ that causes tubercu
losis and two years later the
germ that causes Asiatic chol
era. His later work has been
directed toward the discovery
of a cure for tuberculosis and
other germ diseases. As yet,
however, no certain cure seems
to have been found.

Lister and Antiseptic Treat
ment of Wounds. A third
great benefactor of mankind
was Sir Joseph Lister, an Eng- Robcrt Koch .

lishman who was born in 1827.

As a professor of surgery he first applied antiseptics in the op
erating room. By means of the use of carbolic acid or other
antiseptics on the surface of wounds, on instruments, and on
the hands and clothing of the operating surgeons, disease germs
were prevented from taking a foothold in the wounds. Thus
blood poisoning was prevented. This single discovery has done
more to prevent death after operations than any other of recent
time.

Modern Workers on the Blood. At the present time several
names stand out among investigators on the blood. Paul Ehrlich,
a German born in 1854, is justly famous for his work on the blood
and its relation to immunity from certain diseases. His last

404

SOME GREAT NAMES IN BIOLOGY

great research has given to the world a specific against the dread
disease syphilis.

Another name associated with the blood is that of Elias Metch-
nikoff, a Russian. He was born in 1845. Metchnikoff first
advanced the belief that the colorless blood corpuscles, or phagocytes,
did service as the sanitary police of the body. He has found that
there are several different kinds of colorless corpuscles, each having
somewhat different work to do. Much of the modern work done
by physiologists on the blood are directly founded on the dis
coveries of Metchnikoff.

Heredity and Evolution. Charles Darwin. There is still an
other important line of investigation in biology that we have not
mentioned. This is the doctrine of evolution and the allied dis
coveries along the line of heredity. The development or evolution
of plants and animals from simpler forms to the many and present
complex forms of life have a practical bearing on the betterment

of plants and animals, in
cluding man himself. The
one name indelibly associ
ated with the word evolu
tion is that of Charles
Darwin.

Charles Darwin was born
on February 12, 1809, a son
of well-to-do parents, in the
pretty English village of
Shrewsbury. As a boy he
was very fond of out-of-
door life, was a collector of
birds' eggs, stamps, coins,
shells, and minerals. He
was an ardent fisherman,
and as a young man be
came an expert shot. His studies, those of the English classical
school, were not altogether to his liking. It is not strange, per
haps, that he was thought a very ordinary boy, because his in
terest in the out-of-doors led him to neglect his studies. Later he

Charles Darwin, the grand old man of biology.

SOME GREAT NAMES IN BIOLOGY 405

was sent to Edinburgh University to study medicine. Here the
dull lectures, coupled with his intense dislike for operations, made
him determine never to become a physician. But all this time he
showed his intense interest in natural history and took frequent
part in the discussions at the meetings of one of the student zo
ological societies.

In 1828 his father sent him to Cambridge to study for the
ministry. His three years at the university were wasted so far
as preparation for the ministry were concerned, but they were in
valuable in shaping his future. He made the acquaintance of one
or two professors who were naturalists like himself, and in their
company he spent many happy hours in roaming over the coun
tryside collecting beetles and other insects. In 1831 an event
occurred which changed his career and made Darwin one of the
world's greatest naturalists. He received word through one of
his professional friends that the position of naturalist on her
Majesty's ship Beagle was open for a trip around the world. Dar
win applied for the position, was accepted, and shortly after started
on an eventful five years' trip around the world. He returned to
England a famous naturalist and spent the remainder of his long
and busy life producing books which have done more than those
of any other writer to account in a satisfactory way for the changes
of form and habits of plants and animals on the earth. His
theories established a foundation upon which plant and animal
breeders were able to work.

His wonderful discovery of the doctrine of evolution was due
not only to his information and experimental evidence, but also
to an iron determination and undaunted energy. In spite of
almost constant illness brought about by eyestrain, he accom
plished more than most well men have done. His life should
mean to us not so much the association of his nanie with the
Origin of Species or Plants and Animals under Domestication,
two of his most famous books, but rather that of a patient,
courteous, and brave gentleman who struggled with true English
pluck against the odds of disease and the attacks of hostile critics.
He gave to the world the proofs of the theory on which we to-day
base the progress of the world. Darwin lived long enough to see

406 SOME GREAT NAMES IN BIOLOGY

many of his critics turn about and come over to his beliefs. He
died on the 19th of April, 1882, at seventy-four years of age.

Associated with Darwin's name we must place two other co-
workers on heredity and evolution, Alfred Russel Wallace, an
Englishman who independently and at about the same time
reached many of the conclusions that Darwin came to, and August
Weissman, a German. The latter showed that the protoplasm of
the germ cells (eggs and sperms) is directly handed down from
generation to generation, they being different from the other body
cells from the very beginning. In 1883 a German named Boveri
discovered that the chromosomes of the egg and the sperm cell
were at the time of fertilization just half in number of the other
cells (see page 252) so that a fertilized egg was really a whole cell
made up of two half cells, one from each parent. The chromosomes
within the nucleus, we remember, are believed to be the bearers
of the hereditary qualities handed down from parent to child.
This discovery shows us some of the mechanics of heredity.

Applications to Plant and Animal Breeding. Turning to the
practical applications of the scientific work on the method of
heredity, the name of Gregor Mendel, an Austrian monk, stands
out most prominently. Mendel lived from 1822 until 1884. His
work, of which we already have learned something (see page 258),
remained undiscovered until a few years ago. The application of
his methods to plant and animal raising are of the utmost impor
tance because the breeder is able to separate the qualities he desires
and breed for those qualities only. Another name we have men
tioned with reference to plant breeding is Hugo de Vries, the
Dutchman who recently showed that in some cases plants arise
as new species by sudden and great variations known as mutations.
And lastly, in our own California, Luther Burbank, by careful
hybridizing, is making lasting fame with his new and useful hybrid
plants.

REFERENCES

Conn, Biology. Silver, Burdett & Co.

Darwin, Life and Letters of Charles Darwin. Appletons.

Galton, Hereditary Genius. London (1892).

Thompson, Heredity. John Murray, London England.

Wasmann, Problem of Evolution. Kegan Paul, Trench, Triibner and Co., London, E. C.

APPENDIX

A SUGGESTED OUTLINE FOR BIOLOGY BEGINNING
IN THE FALL

LIST OF TOPICS
FIRST TERM

First week. WHY STUDY BIOLOGY? Relation to human health, hygiene. Rela
tions existing between plants and animals. Relation of bacteria to man.
Uses of plants and animals. Conservation of plants and animals. Relation
to life of citizen in the city. Plants and animals in relation to their environ
ment. What is the environment ; light, heat, water, soil, food, etc. What
plants take out of the environment. What animals take out of the environ
ment. Dependence of plants and animals upon the factors of the environ
ment. Laboratory: Study of a plant or an animal in the school or at
home to determine what it takes from its environment.

Second week. SOME RELATIONS EXISTING BETWEEN PLANTS (GREEN) AND
ANIMALS. Field trip planned to show that insects feed upon plants ; make
their homes upon plants. That flowers are pollinated by insects. Insects
lay eggs upon certain food plants. Green plants make food for animals.
Other relations. (Time allotment. One day trip, collecting, etc. ; two days'
discussion of trip in all its relations.) Make a careful study of the locality
you wish to visit, have a plan that the pupils know about beforehand.
Review and hygiene of pupil's environment, 2 days.

Third week. STUDY OF A FLOWER, PARTS ESSENTIAL TO POLLINATION NAMED.
Adaptations for insect pollination worked out in laboratory. Study of
bee or butterfly as an insect carrier .of pollen. Names of parts of insect
learned. Elementary knowledge of groups of insects seen on field trip.
Bees, butterflies, grasshoppers, beetles, possibly flies and bugs. Drawing
of a flower, parts labeled. Drawing of an insect, outline only, parts labeled.
Careful study of some fall flower fitted for insect pollination with an insect
as pollinating agent. Some examples of cross-pollination explained. Prac
tical value of cross-pollination.

Fourth week. LIVING PLANTS AND ANIMALS COMPARED. Parts of plants, func
tions; organs, tissues, cells. Demonstration cells of onion or elodea. How
cells form others. What living matter can do. Reproduction. Growth of
pollen tube, fertilization. Development of ovule into seed. Fruits, how
formed. Uses, to man.

Fifth week. WHAT MAKES A SEED GROW. Bean seed, a baby plant, and food
supply. Food, what is it? Organic nutrients, tests for starch, protein, oil.
Show their presence in seeds.

407

408 APPENDIX

Sixth week. NEED FOR FOODS. Germination of bean due to (a) presence of
foods, (6) outside factors. What is done with the food. Release of energy.
Examples of engine, plants, human body. Oxidation in body. Proof by
experiment. Test for presence of CO2. Oxidation in growing plant, experi
ment. Respiration a general need for both plants and animals.

Seventh week. NEED TOR DIGESTION. The corn grain. Parts, growth, food
supply outside body of plant, how does it get inside. Digestion, need for.
Test for grape sugar. Enzymes, their function. Action of diastase on starch.

Eighth week. WHAT PLANTS TAKE FROM THE SOIL, How THEY DO THIS. Use of
root. Influence of gravity and water. Why? Absorption a function.
Root hairs. Demonstration. Pocket gardens, optional home work, but each
pupil must work on root hairs from actual specimen. How root absorbs.
Osmosis ; what substances will osmose. Experiments to demonstrate this.

Ninth week. COMPOSITION OF SOIL. What root hairs take out of soil. Plant
needs mineral matter to make living matter. Why? Nitrogen necessary.
Sources of nitrogen, the nitrogen-fixing bacteria. Relation of this to man.
Rotation of crops.

Tenth week. How GREEN PLANTS MAKE FOOD. Passage of liquids up, stem.
Demonstration. Structure of a green leaf. Cellular structure demonstrated.
Microscopic demonstration of cells, stoma, air spaces, chlorophyll bodies.
Evaporation of water from green leaf, regulation of transpiration.

Eleventh week. Midterm Examinations. Sun a source of energy. Effect of
light on green plants. Experimental proof. Starch made in green leaf.
Light and air necessary for starch making. Proof. Protein making in
leaf. By-products in starch making. Proof. Respiration.

Twelfth week. THE CIRCULATION AND DISTRIBUTION OF FOOD IN GREEN PLANTS.
Uses of bark, wood, what part of stem does food pass down. Willow twig
experiment. Summary of functions of living matter in plant. Forestry
lecture. Economic uses of green plants. Reports.

Thirteenth week. PLANTS WITHOUT CHLOROPHYLL IN THEIR RELATION TO MAN.
Saprophytic fungi. Molds. Growth on bread or other substances. Con
ditions most favorable for growth. Favorite foods. Methods of pre
vention. Economic importance.

Fourteenth week. YEASTS IN THEIR RELATION TO MAN. Experiments to show
fermentation is caused by yeasts. Experiments to show conditions
necessary for fermentation. The part played by yeasts in bread making,
in wine making, in other industries. Structure of yeast demonstrated.
Summary.

Fifteenth week. EXPERIMENTS TO SHOW WHERE BACTERIA MAY BE FOUND AND
CONDITIONS NECESSARY TO GROWTH BEGUN. Have cultures collected
and placed in a warm room during the holidays. Suggested experiments
are exposure to air of quiet room and room with persons moving, dust of
floor, knife blade, etc.

Sixteenth, seventeenth, and eighteenth weeks. THE MONTH OF JANUARY SHOULD

BE DEVOTED TO THE STUDY OF BACTERIA IN THEIR GENERAL RELATIONS

TO MAN. Economically, both directly and indirectly. Especial emphasis
placed on the nature and necessity of decay. Bacteria in relation to disease
should also be emphasized. The experiments to be performed and the
topics expected to be covered follow.

APPENDIX 409

CONDITIONS FAVORABLE AND UNFAVORABLE FOR GROWTH OP BACTERIA. (Use
bouillon cultures.) Effect of intense heat, sterile bouillon exposed to air,
effect of boiling, effect of cold, effect of antiseptics (corrosive sublimate,
carbolic acid, boric acid, formalin, etc.), effect of large amounts of sugar and
salt and the relation of this to preserving, etc. Bring out practical appli
cation of principles demonstrated. Discuss sterilization in medicine and
surgery, cold storage, canning, sterilization, e.g. laundries, etc., use of anti
septics, preserving by means of salt and sugar. Microscopic demonstration
of bacteria. Methods of reproduction. Importance in causing organic
decay, fixation of nitrogen, various useful forms in cheese making, butter
ripening, etc. Harmfulness of bacteria as disease producers. Specific dis
eases discussed : tuberculosis, typhoid, infective colds, blood poisoning,
etc. Vaccination. Antitoxins begun continued after knowledge of
human body is gained. Work of Lister and Pasteur.
Nineteenth and twentieth weeks. REVIEW AND EXAMINATIONS.

SECOND TERM

First week. THE BALANCED AQUARIUM. Carbon and nitrogen cycles. Balanced
aquarium and hay infusion compared.

Second week. ONE PROTOZOAN, DEMONSTRATION TO SHOW CHANGES IN SHAPE,
RESPONSE TO STIMULI, SUMMARY OF VITAL PROCESSES IN CELL. Food
getting, digestion, assimilation, oxidation, excretion, growth, reproduction.
Internal structure of protozoan. Protozoa as cause of disease.

Third week. GENERAL SURVEY OF ANIMAL KINGDOM. Survey introduced by
museum trip if possible. Protozoa, worm, insect, fish, mammal. Distinc
tion between vertebrate and invertebrate. Character of mammalia. Divi
sion of labor emphasized. Man's place in nature.

Fourth week. STUDY OF THE FROG. Relation to habitat, adaptations for loco
motion, food getting, respiration, comparison of frog and fish on latter point.
Osmotic exchange of gases emphasized. Cell respiration.

Fifth week. METAMORPHOSIS OF FROG. Fertilization, cell division, and differ
entiation emphasized. Touch on plant and animal breeding. Function
of chromosomes as bearers of heredity. Comparison of bird's egg and mam
mal embryo.

Sixth week. FACTORS IN BREEDING. 1. Variation. 2. Selection. 3. Heredity fixes
variation. 4. Hybridizing. 5. Control of environment. Eugenics in relation
to (a) crime, (6) disease, (c) genius. Continuity of germ plasm. Work of
Darwin, Mendel, De Vries, Burbank.

Seventh week. A BRIEF STUDY OF THE GROSS STRUCTURE OF THE HUMAN BODY.
Skin, muscles, bones. Removal of lime from bone by HC1 to show other
substances and need for lime. Effect of posture, spinal curvature, fractures,
sprains.

Eighth week. NEED FOR FOOD. Nutritive value of food. Use of charts to show
foods rich in carbohydrates, fats, proteins, minerals, water, refuse. The
relation of age, sex, work, and environment to the food requirements. What
is a cheap food. Price list of common foods at present time. Efforts of
government to secure a cheap food supply for the people. Digestibility of
foods.

410 APPENDIX

Ninth week. How THE FUEL VALUE OF FOOD HAS BEEN DETERMINED. Meaning
of calorie. The 10Q-caloric portion, its use in determining a daily or weekly
dietary. Standard dietary as determined by Atwater. Comparison of
standards of Chittenden and Voit with those of Atwater.

Tenth week. STUDY OF PUPIL'S DIETARY. Planning ideal meals. Individual
dietaries for one day required from each pupil. Discussions and corrections.
The family dietary. Relation to cost.

Eleventh week. DIGESTION. The digestive system in the frog and in man com
pared. Drawings of each. Glands and enzymes. Internal secretions and
their importance. Demonstration of glandular tissues. Experiment to
show digestion of starch in mouth.

Twelfth week. DIGESTION CONTINUED. Digestion of white of egg by gastric
juice. Digestion of starch with pancreatic fluid. Functions of pancreatic
juice. Microscopic examination of emulsion. Reasons for digestion.
Part played by osmosis. Demonstration of osmosis. Non-osmosis of non-
digested foods, comparison between osmosable qualities of starch and grape
sugar.

Thirteenth week. ABSORPTION. Where and how foods are absorbed. The
structure of a villus explained. Course taken by foods after absorption.
Function of liver. Blood making the result of absorption. Composition of
blood, red and colorless corpuscles, plasma, blood plates, antibodies.
Microscopic drawing of corpuscles of frog's and man's blood.

Fourteenth week. CIRCULATION OF BLOOD. The heart and lungs of frog demon
strated. Heart of man a force pump, explain with use of force pump.
Demonstration of beef's heart. Circulation and changes of blood in various
parts of body. Work of cells with reference to blood made clear. Capillary
circulation (demonstration of circulation in tadpole's tail or web of frog's
foot).

Fifteenth week. RESPIRATION AND EXCRETION. Necessity for taking of oxygen
to cells and removal of wastes from cells. Part played by blood and lymph.
Mechanics of breathing (use of experiments). Changes of air and blood in
lungs (experiments). Best methods of ventilation (experiments). Elimi
nation of wastes from blood by lungs, skin, and kidneys. Cell respiration.

Sixteenth week. HYGIENE OF ORGANS OF EXCRETION, especially care of skin. The
general structure and functions of the central nervous system. Sensory
and motor nerves. Reflexes, instincts, habits. Habit formation, importance
of right habits. Rules for habit formation. Habit-forming drugs and other
agents. Lecture.

Seventeenth, eighteenth, nineteenth weeks. Civic HYGIENE AND SANITATION.
Hygiene of special senses, eye and ear. A v/ell citizen an efficient citizen.
Public health is purchasable. Improvement of environment a means of
obtaining this. Civic hygiene and sanitation. Cleaning up neighborhood,
inquiry into home and street conditions. Fighting the fly. Conditions of
milk and water supply. Relation of above to disease. Work of Board of
Health, etc. Review and Examinations.

APPENDIX 411

SUGGESTED SYLLABUS FOR COURSE BEGINNING FEB
RUARY 1 AND ENDING THE FOLLOWING JANUARY

FIRST TERM

First week. WHY STUDY BIOLOGY? Relation to human health, hygiene. Rela
tions existing between plants and animals. Relation of bacteria to man.
Uses of plants and animals. Conservation of plants and animals. Relation
to life of citizen in this city. Needs of plants and animals : (1) food, (2)
water, (3) air, (4) proper temperature. Study of a single plant or animal in
relation to its environment. Problems of city government : (a) storage, pres
ervation and distribution of foods, (6) water supply, (c) overcrowded tene
ments, (d) street cleaning, (e) clean schools. Biological problems in city
government.

Second week. INTERRELATIONS BETWEEN PLANTS AND ANIMALS. Plants furnish
food, clothing, shelter, and medicine. Animals use food, shelter. Man's
use of plants as above. Man's use of animals as above. Plant and animal
industries. Use of balanced aquarium as illustrative material.

Third week. DESTRUCTION OF FOOD AND OTHER THINGS BY MOLD. Home exper
iment. Conditions favorable to growth of mold. Food, moisture, tempera
ture. Destruction of commodities by mold : food, leather, clothing.

Fourth week, fifth week. DESTRUCTION OF FOODS BY BACTERIA. Experiment.
To show where bacteria are found. Soil, dust, water, milk, hands, mouth.
Use and harm of decay. Relation to agriculture. Experiment. Conditions
favorable and unfavorable to growth of bacteria : boiling, cold, sugar, salt.
Bacteria in relation to disease briefly mentioned. Bacteria in industries.

Sixth week. USE OF STORED FOOD BY YOUNG GREEN PLANT : (a) for energy, (6) for
construction of tissue. Experiment. Structure of bean seed. Draw to show
outer coat, cotyledon, hypocotyl, and plumule. Test for starch and sugar
(grape). Test for oil, protein, water, mineral matter. Use of all nutrients
to seedling.

Seventh week. OTHER NEEDS OF YOUNG PLANTS. Home experiments to show
(a) temperature, (6) amount of water most favorable to germination.
Experiment. To show need of oxygen. To show that germinating seeds give
off carbon dioxide. Proof of presence of carbon dioxide in breath. The
needs of a young plant compared with those of a boy or girl.

Eighth week. DIGESTION IN SEEDLING. Structure of corn grain. Experiment.
To show that starch is digested in a growing seedling (corn). Experiment.
To show that diastase digests starch. Discussion of experiments.

Ninth week. WHAT PLANTS TAKE FROM THE SOIL AND How THEY DO THIS.
Use of roots. Proof that it holds plant in position, takes in water and
mineral matter, and in some cases stores food. Influence of gravity and
water. Labeled drawing of root hair. Root hair as a cell emphasized.
Osmosis demonstrated.

Tenth week. COMPOSITION OF THE SOIL. Demonstration of presence of mineral
and organic substances in the soil. What root hairs take from the soil.
Mineral matter necessary and why. Importance and sources of nitrogen.
Soil exhaustion and its prevention. Nitrogen-fixing bacteria. Review
bacteria of decay. Rotation of crops.

412 APPENDIX

Eleventh week. UPWARD COURSE OF MATERIALS IN THE STEM. Demonstration
of pea seedlings with eosin to show above. Demonstration of evaporation of
water from a leaf. Action of stomata in control of transpiration. Cellular
structure of leaf. Demonstration of elodea to show cell.

Twelfth week. SUN A SOURCE OF ENERGY. Heliotropism. Demonstration.
Necessity of sunlight for starch manufacture. Necessity of air for starch
manufacture. By-products in starch making. Oil manufacture in leaf.
Protein manufacture in plant. Respiration.

Thirteenth week. REPRODUCTION. Necessity for (a) perpetuation, (fo) regenera
tion. Study of a typical flower to show sepals, petals, stamens, pistil.
Functions of each part. Cross and longitudinal sections of ovary shown
and drawn. Emphasis on essential organs. Pollination, self and cross.
(NOTE. At least one field trip must be planned for the month of May. This
trip will take up the following topics : The relations between flowers and
insects. The food and shelter relation between plants and animals. Recog
nition of 5 to 10 common trees. Need of conservation of forests. An
extra trip could well be taken to give child a little knowledge and love for
spring flowers and awakening nature.)

Fourteenth week. STUDY OF THE BEE OR BUTTERFLY WITH REFERENCE TO
ADAPTATIONS FOR INSECT POLLINATION. Study of an irregular flower to
show adaptations for insect visitors. Fertilization begun. Growth cf
pollen tubes.

Fifteenth week. FERTILIZATION COMPLETED. Use of chart to show part played
by egg and sperm cell. Ultimate result the formation of embryo and its
growth under favorable conditions into young plant. Relation of flower and
fruit, pea, or bean used for this purpose. Development of fleshy fruit. Apple
used for this purpose.

Sixteenth week. MATURING OF PARTS AND STORING OF FOOD IN SEED AND FRUIT.
The devices for scattering the seeds and relation to future plants. Resume
of processes of nutrition to show how materials found in fruit and seed are
obtained by the plant.

Seventeenth week. PLANT BREEDING. Factors : (a) selective planting, (6) cross-
pollination, (c) hybridizing. Heredity and variation begun. Darwin and
Burbank mentioned.

Eighteenth and nineteenth weeks. THE NATURAL RESOURCES OF MAN : SOIL,
WATER, PLANTS, ANIMALS. The relation of plant life to the above factors of
the environment. The relation of insects to plants (forage and other crops)
and the relation of birds to insects. Need for conservation of the helpful
factors in the environment of plants. Attention called to some native birds
as insect and wood destroyers.

Twentieth week. REVIEW AND EXAMINATIONS.

SECOND TERM

First week. THE BALANCED AQUARIUM. Study of conditions producing this.
The role of green plants, the role of animals. What causes the balance.
How the balance may be upset. The nitrogen cycle. What it means in the
world outside the aquarium. Symbiosis as opposed to parasitism. Ex
amples.

APPENDIX 413

Second week. STUDY OF THE PABAMECIUM. Study of a hay infusion to show how
environment reacts upon animals. Relation to environment. Study of
cell under microscope to show reactions. Structure of cell. Response to
stimuli, function of cilia, gullet, nucleus, contractile vacuoles, food vacuoles,
asexual reproduction. Drawings to show how locomotion is performed,
general structure. Copy chart for fine structure.

Third week. A BIRD'S-EYE VIEW OF THE ANIMAL KINGDOM. One day. Develop
ment of a multicellular organism. (Use models.) One day. Physiological
division of labor. Tissues, organs. Functions common to all animals.
Illustrative material. Optional trip to museum for use of illustrative
material to illustrate the principal characteristics of (a) a simple metazoan,
sponge, or hydrazoan, (6) a segmented worm, (c) a crustacean (Decapod),
(</) an insect, (e) a mollusk and echinoderm, (/) vertebrates. (Differences
between vertebrates and invertebrates.) The characteristics of the verte
brates. Distinguish between fishes, amphibia, reptiles, birds, mammals.
Two days for discussion. Man's place in the animal series, elementary dis
cussion of what evolution means.

Fourth week. THE ECONOMIC IMPORTANCE OF ANIMALS. Uses of animals :

(1) As food. Directly : fish, shellfish, birds, domesticated mammals.

(2) Indirectly as food : protozoa, Crustacea. (3) They destroy harmful
animals and plants. Snakes birds; birds insects; birds weed seeds;
herbivorous animals weeds. (4) Furnish clothing, etc. Pearl buttons,
etc. (5) Animal indiistries, silkworm culture, etc. (6) Domesticated
animals.

Animals do harm : (1) To gardens. (2) To crops. (3) To stored food ;
examples, rats, insects, etc. (4) To forest and shade trees. (5) To human
life. Disease : parasitism and its results, examples, from worms, etc. ; dis
ease carriers fly, etc. Preventive measures. Methods of extermination.

References to Toothaker's Commercial Raw Materials. Use one day for
laboratory work from references.

Fifth week. THE STUDY OF A WATER-BREATHING VERTEBRATE. Two days.
The fish, adaptations in body, fins, for food getting, for breathing. Struc
ture of gills shown. Laboratory demonstration to show how water gets to
the gills. Drawings. Outline of fish, gills. Required trip to aquarium.
Object, to see fish in environment. One day. Home work at market.
Why are some fish more expensive than others. Economic importance of
fish. Relation of habits of (a) food getting, (b) spawning to catching and
extermination of fish. Two days. Means of preventing overfishing, stock
ing, fishing laws, artificial fertilization of eggs, methods. Development of
fish egg. Comparison with that of frog and bird.

Sixth week. THE FACTORS UNDERLYING PLANT AND ANIMAL BREEDING. Study
of pupils in class to show heredity and variation. Conclusion. Animals
tend to vary and to be like their ancestors. Heredity, r61e of sex cells,
chromosomes. Principles of plant breeding. Selective planting, hybridiz
ing, work of Darwin, Mendel, De Vries, and Burbank. Methods and results.
Animal breeding, examples given, results. Improvement of man : (1.) by
control of environment, (a) example of clean-up campaign, 1913 ; (2) by con
trol of individual, personal hygiene, and control of heredity. Eugenics.
Examples from Davenport, Goddard, etc.

414 APPENDIX

Seventh week. THE HUMAN MACHINE. Skin, bones and muscles, function of
each. Examples and demonstration with skeleton. Organs of body cavity ;
show manikin. Work done by cells in body.

Eighth week. STUDY OF FOODS to determine : (a) nutritive value. Exercise with food
charts to determine foods rich in water, starch, sugar, fats, proteins, mineral
salts, refuse. One day. (6) Nutritive value of foods as related to work,
age, sex, environment, cost, and digestibility. Foods compared to determine
what is really a cheap food.

Ninth week. How THE FUEL VALUE OF FOOD HAS BEEN DETERMINED. The
dietaries of Atwater, Chittenden, and Voit. The 100-calorie portion table
and its use.

Tenth week. THE APPLICATION OF THE 100-CALORiE PORTION TO THE MAKING
OF THE DAILY DIETARIES. Luncheon dietaries. A balanced dietary for
pupil for one day. Family dietaries. Relation to cost. Reasons for this.

Eleventh week. FOOD ADULTERATIONS. Tests. Drugs and the alcohol question.

Twelfth week. DIGESTION. The alimentary canal of frog and of man compared.
Drawings. (One day.) The work of glands. Work of salivary gland.
Enzymes, internal secretions. Experiments to show (a) digestion of starch
by saliva, (6) digestion of proteins by gastric or pancreatic juice, (c) emulsi-
fication of fats in the presence of an alkaline medium. Functions of other
digestive glands. Movements of stomach and intestine discussed and ex
plained.

Thirteenth week. ABSORPTION. How it takes place, where it takes place. Pas
sage of foods into blood, function of liver, glycogen.

Fourteenth week. THE BLOOD AND ITS CIRCULATION. Composition and functions
of plasma, red corpuscles, colorless corpuscles, blood plates, antibodies.
The lymph and work of tissues. The blood and its method of distribu
tion. Heart a force pump. Demonstration. Arteries, capillaries (demon
stration), veins. Hygiene of exercise.

Fifteenth week. WHAT RESPIRATION DOES FOR THE BODY. The apparatus used.
Changes of blood within lungs, changes of air within lungs. Demonstration.
Cell respiration. The mechanics of respiration. Demonstration. Venti
lation, need for, explain proper ventilation. Demonstration. Hygiene of
fresh air and proper breathing. Dusting, sweeping, etc.

Sixteenth week. EXCRETION, ORGANS OF. Skin and kidneys, regulation of body
heat. Colds and fevers. Proper care of skin, hygiene. Summary of
blood changes in body. Explanation of same.

Seventeenth week. BODY CONTROL AND HABIT FORMATION. Nervous system, nerve
control. The neuron theory, brain psychology explained in brief. Habits
and habit formation. Hygiene of sense organs.

Eighteenth and nineteenth weeks. Civic HYGIENE AND SANITATION. THE IM
PROVEMENT OF ONE'S ENVIRONMENT. Civic conditions discussed. Water,
milk, food supplies. Relation to disease. How safeguarded. How help im
prove conditions in city.

Twentieth week. REVIEW AND EXAMINATIONS.

APPENDIX 415

HYGIENE OUTLINE

(This outline may be introduced with Plant Biology, or, better, may come as application of
the work in Second-term Biology.)

THE ENVIRONMENT. Changes for betterment under control. How a city boy
may improve his environment : by proper clothing, proper food and preparation of
food, by care in home life ; by sanitary conditions in neighborhood and in home.

REVIEW OF ACTIVITIES OP CELL. Irritability, food taking, assimilation, oxidation,
excretion, reproduction. Similarity of functions of plant and animal cells. All
cells perform these functions. Some cells perform functions especially well, e.g.
contracting muscle cells. All cells need food and oxygen. Some must have this
carried to them. A system of tubes carries blood which carries food and oxygen.
Food must be prepared to get into the blood. Digestive system : mouth, teeth,
stomach, intestines, glands, and digestive juices. Uses of above in preparing food
to pass into the blood. Absorption of food into the blood. How oxygen gets to
the cells. Nose, throat, windpipe, lungs ; blood goes to lungs and carries away
oxygen. Excretion. Cells give up wastes to blood and these wastes taken out of
blood by kidneys and other glands and passed out of body. Sweat, urine, carbon
dioxide.

CERTAIN KINDS OF WORK PERFORMED BY CERTAIN KINDS OF CELLS. Advantage
of this. Cells of movement. Muscles, tissues. Bones as levers necessary for some
movements. This especially true for legs and arms. Skeleton also necessary for pro
tection of internal organs and support of body. Making of special things in the
body, e.g. digestive juices given to certain cells called gland cells. Working together
or coordination of different organs provided for by nervous system. This is com
posed of cells which are highly irritable or sensitive. Collections of these nerve
cells give us the power of feeling or sensation and of thinking.

DIETETICS. Diet influenced by age, weight, occupation, temperature or climate,
cheapness of food, digestibility.

NUTRIENTS. List of nutrients found in seeds and fruits, also other common foods.
Need of nutrients for human body. Nitrogenous foods, examples. A mixed diet
best.

DIGESTION AND INDIGESTION. What is digestion? Where does it take place?
Causes of indigestion. Eating too rapidly and not chewing food. Eating foods
hard to digest. Overeating. Eating between meals. Hard exercise immediately
before or after eating.

CONSTIPATION. A condition in which the bowels do not move at least once every
day. Dangers of constipation. Poisonous materials may be absorbed, causing
lack of inclination to work, headache. Importance of regular habits of emptying
the bowels. Each one must try to get at the cause of constipation in his own case.
Causes of constipation. Lack of exercise, improper food, not drinking enough water,
lack of laxative food, as fruits; lack of sleep, lack of regular habits. Remedies.
Avoid use of drugs. Half hour before breakfast a glass of hot water, exercise of
abdominal muscles, laxative foods, form habit of moving bowels after breakfast.

HYGIENE OF CIRCULATION AND ABSORPTION. How digested foods get to the cells.
Absorption. Definition. The passing of the digested food into the blood. How
accomplished. Blood vessels. In walls of stomach and food tube. Membrane
of cells separating food from blood. Food passes by osmosis through the membrane
and by osmosis through the thin walls of the blood vessels.

416 APPENDIX

CIRCULATION OF FOODS. Blood contains foods, oxygen, and .vaste materials.
Heart pumps the blood, blood vessels subdivide until very small and thin, so food,
etc., passes from them to cells. Hygiene of the heart.

TRANSPIRATION AND EXCRETION. Skin, function in excretion. Bathing. Care of
skin. Hot baths. Bathe at least twice a week. Cold baths, how taken. Bath
tub not a necessity. Effect of latter on educating skin to react. Relation to
catching cold.

CARE OF SCALP AND NAILS. Scalp should be washed weekly. If dandruff present,
wash often enough to keep clean. Baldness often results from dandruff. Finger
nails cut even with end of fingers and cleaned daily with scrub brush.

HYGIENE OF RESPIRATION. Definition of respiration. Object of respiration.
(Connection between circulation and respiration.) Necessity of oxygen. Organs
of respiration. Lungs most important. Deep breath, function. Ventilation,
reasons for. Mouth breathing. Results. Lessened mental power, nasal catarrh,
colds easily caught.

PLANTS HARMFUL to MAN. Poison ivy and mushrooms. Treatment. Poisoning.
Send for physician. Cause vomiting by (1) finger, (2) mustard and water. (NOTE.
An unconscious .person should not be given anything by the mouth unless he can
swallow.) Relation of yeasts and bacteria to man. Fermentation a cause of
indigestion. Relation to candy, sirups, sour stomach, formation of gas causes pain.

BACTERIA OF MOUTH AND ALIMENTARY CANAL. Entrance of bacteria by mouth
and nose. Nose : " cold in the head," grippe, catarrh. Mouth : decay of teeth, ton
sillitis, diphtheria. Germs pass from one person to another, no one originates germs
in himself. Precautions against receiving and transferring germs. Common
drinking cups, towels, coins, lead pencils, moistening fingers to turn pages in book or
to count roll of bills. Tuberculosis germs. Entrance by mouth, lungs favorite
place, may be any part of body. Dust of air, sweeping streets, watering a necessity.
Spitting in streets and in public buildings. Germs of typhoid fever. Entrance :
water, milk, fresh uncooked vegetables, oysters. Thrive in small intestines.
Preventable. Typhoid epidemics, methods of prevention of typhoid. Conditions
favorable for growth of specific disease germs. Work of Boards of Health.

Home sanitary conditions, sunlight, air, curtains and blinds, open windows.
Live out of doors as much as possible. Cleanliness. Bare walls well scrubbed
better than carpets and rugs. Lace curtains, iror bedsteads, one thickness of
paper on walls. Open plumbing, dry cellars, all garbage promptly removed.

This outline is largely the work of Dr. L. J. Mason and Dr. C. H. Morse of the
department of biology of the De Witt Clinton High School.

WEIGHTS, MEASURES, AND TEMPERATURES

As the metric system of weights and measures and the Centigrade measurement
of temperatures are employed in scientific work, the following tables showing the
English equivalents of those in most frequent use are given for the convenience of
those not already familiar with these standards. The values given are approximate
only, but will answer for all practical purposes.

WEIGHT

MEASURES OF LENGTH

Kilogram

kg.

1\ pounds

METRIC

ENGLISH EQUIVALENTS

Gram . .

gm.

15j grains avoir
dupois.
2 g of an ounce
avoirdupois.

Kilometer

km.

f of a mile.

Meter . .

39 inches.

CAPACITY

Liter . .

61 cubic inches, or
a little more than
1 quart, U. S.
measure.

Decimeter

dm.

4 inches.

Centimeter

cm.

f of an inch.

Cubic cen
timeter .

cc.

fa of a cubic inch.

Millimeter

mm.

2K of an inch.

The next table gives the Fahrenheit equivalent for every tenth degree Centigrade
from absolute zero to the boiling point of water. To find the corresponding F. for
any degree C., multiply the given C. temperature by nine, divide by five, and add
thirty-two. Conversely, to change F. to C. equivalent, subtract thirty-two, multi
ply by five, and divide by nine.

CENT. FAHR. CENT. FAHR. CENT.

FAHR. CENT.

FAHR.

100 .

. . 212

50 .

. . 122

. .

. 32

- 50 . . . - 58

90 .

. . 194

40 .

. . 104

- 10 . .

- 100 . . . - 148

80 .

. . 176

30 .

. . 86

-20 ..

. - 4

70 .

. . 158

20 .

. . 68

- 30 . .

. -22

Absolute zero

60 .

. . 140

10 .

. . 50

-40 ..

. -40

- 273 . . . - 459

HUNTER, CIV. Bl. 27

417

418 APPENDIX

LABORATORY EQUIPMENT

The following articles comprise a simple equipment for a laboratory class of
ten. The equipment for larger classes is proportionately less in price. The follow
ing articles may be obtained from any reliable dealer in laboratory supplies, such as
the Bausch and Lomb Optical Company of Rochester, N.Y., or the Kny-Scheerer
Company, 404, 410 West 27th Street, New York City :

1 balance, Harvard trip style, with weights on carrier.

1 bell jar, about 365 mm. high by 165 mm. in diameter.
10 wide mouth (salt mouth) bottles, with corks to fit.

10 25 c.c. dropping bottles for iodine, etc.
25 250 c.c. glass-stoppered bottles for stock solutions.
100 test tubes, assorted sizes, principally 6" X f ".
50 test tubes on base (excellent for demonstrations).

2 graduated cylinders, one to 100 c.c., one to 500 c.c.

1 package filter paper 300 mm. in diameter.
10 flasks, Erlenmeyer form, 500 c.c. capacity.

2 glass funnels, one 50, one 150 mm. in diameter.

30 Petri dishes, 100 mm. in diameter, 10 mm. in depth.
10 feet glass tubing, soft, sizes 2, 3, 4, 5, 6, assorted.

1 aquarium jar, 10 liters capacity.

2 specimen jars, glass tops, of about 1 liter capacity.
10 hand magnifiers, vulcanite or tripod form.

2 compound demonstration microscopes or 1 more expensive compound micro
scope.

300 insect pins, Klaeger, 3 sizes assorted.
10 feet rubber tubing to fit glass tubing, size f inch.

1 chemical thermometer graduated to 100 C.
15 agate ware or tin trays about 350 mm. long by 100 wide.
1 gal. 95 per cent alcohol. (Do not use denatured alcohol.)
1 set gram weights, 1 mg. to 100 g. 2 books test paper, red and blue.

1 razor, for cutting sections. 10 Syracuse watch glasses.

1 box rubber bands, assorted sizes. 1 steam sterilizer (tin will do).

1 support stand with rings. 1 spool fine copper wire.

1 test tube rack. 1 alcohol lamp. 6 oz. nitric acid.

5 test tube brushes. 1 gross slides. 6 oz. ammonium hydrate.

10 pairs scissors. 100 cover slips No. 2. 6 oz. benzole or xylol.

10 pairs forceps. 1 mortar and pestle. 6 oz. chloroform.

20 needles in handles. 2 bulb pipettes. ^ Ib. copper sulphate.

10 scapels. 1 liter formol. ? Ib. sodium hydroxide.

12 mason jars, pints. 1 oz. iodine cryst. | Ib. rochelle salts.

12 mason jars, quarts. 1 oz. potassium iodide. 6 oz. glycerine.

The materials for Pasteur's solution Sach's nutrient solution can best be obtained
from a druggist at the time needed and in very small and accurately measured
quantities.

The agar or gelatine cultures in Petri dishes may be obtained from the local
Board of Health or from any good druggist. These cultures are not difficult to
make, but take a number of hours' consecutive work, often difficult for the average
teacher to obtain. Full directions how to prepare these cultures will be found in
Hunter's Laboratory Problems in Civic Biology.

INDEX

(Illustrations are indicated by page numerals in bold-faced type.)

Absorption, definition, 270 ;

of digested foods, 308, 309.
Accommodation of eye, 361.
Acetanilid, 295.
Action of the heart, 319.
Adaptations, 24 ;

in bee, 36 ;

in birds, 189 ;

in fish, 232 ;

in frog, 241 ;

in mammalia, 192.
Adenoids, 340, 395.
Adulteration in foods, 288.
Air, and bacteria, 145 ;

composition of, 20 ;

fresh, 337 ;

needed in germination, 66 ;

necessary in starch making, 91 ;

passages in lungs, 330 ;

use to plants and animals, 21.
Albumin, 62.
Alcohol, a food, 289 ;

a poison, 291.

and ability to resist disease, 363 ;

and ability to work, 368 ;

and body heat, 345 ;

and crime, 371, 372 ;

and digestion, 311 ;

and duration of life, 370 ;

and efficiency, 369 ;

and heredity, 372 ;

and intellectual ability, 364 ;

and kidneys, 346 ;

and living matter, 291 ;

and memory, 365;

and mental ability, 366 ;

and nervous system, 362 ;

and organs of special sense, 362 ;

and pauperism, 371 ;

and resistance, 327 ;

Alcohol, and respiration, 346 ;

and the blood, 327 ;

and treatment of disease, 364 ;

effect on circulation, 327 ;

effect on eye, 361 ;

effect on liver, 312 ;

produces poisons, 347.
Algso, 176.
Alfalfa plant, 151.
Alimentary canal, 297.
Alkali, 306.
Alkalinity, 298.
Alligator, 230.
Ambergris, 205.
Ammonium hydrate, 61.
Amoeba, 170, 182, 332.
Amphibia, 186, 187 ;

as food, 202.
Anal fin of fish, 233.
Angiosperms, 176.
Animals, as disease carriers, 227

breeding of, 259 ;

domesticated, 260 ;

functions of, 48, 180 ;

need plants, 34 ;

oils of, 205 ;

parasitic, 227 ;

series; 182;

that prey upon man, 230 ;

use to man, 17 ;

use to plants, 34.
Annual rings, 98.
Anopheles, 217, 218.
Anosia plexippus, 32.
Anther, 36.

Antibodies, uses of, 316.
Antiseptics, 157.
Antitoxin, 157, 391.
Anura, 188.
Anvil, 359.

419

420

INDEX

Aorta, 320.
Apoplexy, 328.
Appendages of the fish, 233.
Appendieular skeleton, 268.
Appendix, 309.
Apples, 56, 124.
Aqueous humor, 361.
Arachnida, 185.
Arteries, 318 ;

structure of, 323.
Arthropods, 185.
Artificial, cross- pollination, 46;

propagation of fishes, 240 ;

respiration, 340 ;

selection, 253.
Asexual reproduction, 174.
Assimilation in plants, 103.
Attention, effect of alcohol, 364.
Audubon, 211.
Auricle of human heart, 319 ;

of fish heart, 236.
Automatic activity, 348, 354.
Axial skeleton, 268.

Bacillus, 142.
Bacteria, 134;

and fermentation, 150 ;

cause decay, 149 ;

cause disease, 151 ;

effect on food, 144 ;

growth of, 145 ;

isolating a pure culture, 142 ;

nitrogen fixing, 80, 81, 151, 152

of decay, 144 ;

relation to man, 16 ;

size and form, 142, 143 ;

useful, 150;

where found, 139, 141.
Bacteriology, 16.
Bad posture, 270.
Balanced, aquarium, 159, 160;

diet, 285.

Barbels of fish, 234.
Barberry embryo, 103.
Bark, use of, 98.
Barrier, natural, 25.
Bast, 97.

Beans, as food, 62.
Beans, peas, 55.

Beans, seedlings, 63.
Bedroom, care of, 374.
Bee, adaptations, 36 ;

head of, 38 ;

mouth parts, 38.
Beer and wine making, 137.
Benedict's test, 68.
Benzoic acid, 148.
Beverages and condiments, 124.
Biceps, 269.

Bichloride of mercury, 148.
Bile, functions of, 306, 307.
Biology, definition, 15 ;

relation to society, 18.
Birds, 189;

as food, 202 ;

classification, 191 ;

development, 246 ;

eat insects, 209 ;

eat weed seeds, 210 ;

embryo, 246, 247.
Bismuth, 304.
Bison, 192.
Black Death, 227.
Blade of leaf, 85.
Blastula, 177.

Blood, amount and distribution,
318;

changes in lungs, 330 ;

circulation of man, 318 ;

clotting, 314 ;

composition, 314 ;

effect of alcohol, 327 ;

function, 313 ;

plates, 315 ;

poisoning, 156;

temperature, 318 ;

vessel of skin, 344.
Blubber, 205.
Blue crab, 199.

Board of health, functions, 389.
Body, a machine, 348 ;

cavity, 270 ;

heat and alcohol, 345 ;

of fish, 232.
Bony fish, 187.
Boracic acid, 148.
Borax, 148.
Brain, of fish, 237 ;

INDEX

421

Brain, of man, 351.
Bread, making, 139;

mold, 133.
Bream, 233.
Breathing, 333 ;

and tight clothing, 339 ;

hygienic habits, 338 ;

in leaf, 93 ;

of fish, 234 ;

of frog, 242 ;

of vertebrates, 232 ;

rate of, 334.

Breeding of animals, 259.
Bright 's disease, 346.
Bronchi, 330.
Bronchial tubes, 330.
Bruises, 345.
Bryophytes, 176.
Bubonic plague, 227.
Budding, 255, 256.
Bumblebees, 37.
Burbank, Luther, 406.
Burns, treatment of, 345.
Butter and eggs, 38, 39.

Calorie, portion, 286;

requirement, 282.
Calyx, 35.
Cambium layer, 98.
Canning, 145.
Cannon, Prof., 304.
Capillaries, 318, 323 ;

circulation in, 322 ;

of fish, 236.

Carbohydrates, 60, 273.
Carbolic acid, 149.
Carbon and oxygen cycle, 161.
Carbon dioxide, test for, 64.
Care of milk supply, 380, 383.
Carnivorous, 230.
Caudal fin of fish, 233.
Cause of dyspepsia, 310.
Cells, 50 ;

as units, 171 ;

division, 51 ;

mucous, 299 ;

of pond scum, 173 ;

reproduction of, 50 ;

respiration, 332 ;

Cells, tissue, 179;

work of, 270.
Cephalothorax, 185.
Cerebellum, 352.

Cerebro-spinal nervous system, 350.
Cerebrum, 351.
Cestodes, 227.
Changes, of blood in lungs, 330 ;

of air in lungs, 331.
Characters, determiners of, 258.
Chelonia, 188.
Chemical, compounds, 20 ;

elements, 20 ;

of human body, 21.
Chestnut canker, 131.
China, deforestation in, 108.
Chittenden table, 311.
Chloral, 293.

Chlorophyll bodies, 50, 90.
Chloroplasts, 90.
Chromosomes, 50 ;

and heredity, 251.
Chrysalis, 33.
Cilia, 171.
Circulation, effect of alcohol, 327 ;

effect of exercise, 326 ;

effect of tobacco, 328 ;

in fish, frog, man, 321, 322 ;

in stem, 99, 100, 101 ;

of blood of man, 318 ;

of fish, 236 ;

of frog, 243 ;

portal, 322 ;

pulmonary, 320 ;

systemic, 320.
City's need for trees, 115.
Civic hygiene, 388.
Clams, 200.
Classification, of birds, 191 ;

of plants, 176.
Cloaca of frog, 243.
Clothing, 203.
Clotting of blood, 314.
Coal, 64.
Cobra, 230.
Cocaine, 293.
Coccus bacteria, 142.
Cochineal and lac, 208.
Cochlea, 359.

422

INDEX

Codling moth, 215.
Ccelenterates, 183.
Cold-blooded animals, 318 ;

effect of, 23.
Cold storage, 147.
Colds and fevers, 343.
Coleoptera, 32.
Collecting ashes, 387.
Colonies of bacteria, 141 ;

of trilliums, 175.
Colorless corpuscles, 313 ;

structure, 315 ;

function, 316.
Common foods contain nutrients,

275.

Comparison, of food tube of frog and
man, 297 ;

of mold, yeast and bacteria, 143 ;

of starch making and milling,

92.

Complemental air, 334.
Complex one-celled animals, 171.
Composition, of milk, 273, 280 ;

of plasma, 313 ;

of soil, 77.
Compound eyes of bumblebee, 37,

38.
Conservation, of food fish, 239 ;

of fur-bearing animals, 204 ;

of our natural resources, 17.
Constipation, 310.
Constrictor killing a mouse, 213.
Contagious diseases, 152.
Convolutions, 352.
Corn, 120, 121 ;

germinated grain cut lengthwise,
69;

long section of ear, 67 ;

structure of grain, 66.
Cornfield, 44.
Corolla, 35.

Corpuscles, colorless and red, 313.
Cost of food and diet, 281, 283 ;

of parasitism, 263.
Cotton, 125;

boll weevil, 126, 127, 214.
Cotyledons, 59 ;

food in, 60.
Crab, 199.

Crayfish, 184.
Crocodile, 230.
Crocodilia, 189.
Crustacea, 185.
Culex, 218, 218.
Culture medium, 140.
Cuts and bruises, treatment, 326,
345.

Daily calorie requirement, 282 ;

fuel needs of body, 284.
Dandelion, whorled leaves, 90.
Darwin, Charles, 40, 404.
Darwin and natural selection, 253.
Deaths, table, 312.
Decay caused by bacteria, 149.
Decayed teeth, 396.
Defects in eye, 361.
Deforestation in China, 108.
Dendrites, 351.
Department of Agriculture, work of,

255.
Department of street cleaning,

387.
Determiners, 251 ;

of character, 258.
Development, of apple, 56 ;

of bird, 246 ;

of egg, 178 ;

of trout, 238 ;

of mammal, 247 ;

of salmon, 241 ;

of simple animal, 177.
Diagram of frog's tongue, 242 ;

of gills of fish, 235 ;

of neuron, 351 ;

of wall small intestine, 307.
Diaphragm, 270, 297.
Diastase, 101, 300 ;

action on starch, 69.
Diet, and cost of food, 281 ;

and digestibility, 281 ;

balanced, 285 ;

relation of age, 280 ;

relation of environment to, 280 ;

relation to sex, 280 ;

relation of work to, 277 ;

the best, 284.
Dietary, the best, 282.

INDEX

423

Digested food, absorption of, 308.
Digestibility and diet, 281.
Digestion, 68, 100, 181 ;

effect of alcohol, 311;

definition of, 270 ;

in stem, 99 ;

in stomach, 304 ;

of starch, 299 ;

purpose of, 69, 296.
Digestive system of fish, 235.
Digestive tract of frog and man,

297.

Diphtheria, 152.
Dipnoi, 187, 236.
Diptera, 31.

Discoverers of living matter, 398.
Disease, and alcohol, 312 ;

and bacteria, 151 ;

carriers, animals, 226 ; .

carriers, flies, 222 ;

carriers, insects, 225 ;

caused by bacteria, 152 ;

caused by protozoa, 172 ;

effect of alcohol, 327 ;

of noso and throat, 340;

protozoan, 221.
Disinfectants, 148.
Division of labor, 178, 267.
Dog, skeleton, 185.
Domesticated animals, 203, 260.
Dominant characters, 258.
Dormant, 22.
Dorsal, 186;

fin, 233.

Drugs, use and abuse, 294.
Duff, 113.

Dyspepsia, cause and prevention,
310.

Ear, section, 359.
Echinoderms, 184.
Economic value of green plants, 117 ;
importance of spawning habits of

fishes, 239.
Ectoderm, 177.
Effect of light on leaves, 88.
Efficiency of a week, 370.
Egg, 177, 246.
Egg-laying habits of fishes, 238.

Ehrlich, Paul, 403.
Elasmobranchs, 187.
Elements, chemical, 20, 21.
Elodea, 49, 50.
Embryo, 58, 59, 103 ;

of bird, 247 ;

of mammal, 247.
Emulsion, 306.
Endoderm, 177.
Endoskeleton, definition, 237.
Endosperm, 67.
Enemies of forests, 113, 114.
Energy, 64;

of a tree, 94 ;

source of, 88.
English sparrow, 212.
Environment, 19, 19 ;

care and improvement of, 26 ;

changes in, 25 ;

determines kind of plants and
animals, 23, 23, 24 ;

normal, 28 ;

of man, 26, 266 ;

natural, 25 ;

relation to diet, 280 ;

what plants and animals take

from, 21.

Enzymes, 68, 101, 298.
Epicotyl, 59.
Epidermis, 86.
Epithelial layer, 308.
Epithelium, 179.
Erosion, prevention of, 106, 108 ;

at Sayre, Pa., 106.
Essential organs, 36.
Esophagus, 302.
Eugenics, 261.
Eustachian tubes, 300, 359.
Euthenics, 264.
Evaporation, 99;

of water, 85, 86, 87.
Evolution, 194, 195.
Excretion, 181, 270, 332;

organs of, 340 ;

in plants, 103.
Exercise and circulation, 326 ;

and health, 339.
Exoskeleton, 185, 237.
Extermination of birds, 211.

424

INDEX

Eye, compound, 30 ;

defects in, 361 ;

section of, 360.
Eyestrain, 395.

Factory inspection, 379.
Fallowing, 82.
Fatigue, 326 ;

and nerve cells, 356.
Fats and oils, 60, 273.
Fehling's solution, 68, 299.
Fermentation, 135, 136, 150.
Fertilization, of fish eggs, 240 ;

of flower, 54.
Fibers, vegetable, 127.
Fibrin, 315.
Fibrinogen, 315.
Fig insect, 43.
Filament, 36.

Filter beds at Albany, N. Y., 385.
Fins, 233.
Fishes, 186;

artificial propagation, 240 ;

as food, 201 ;

body of, 232 ;

breathing, 234 ;

circulation, 236, 321 ;

digestive system, 235 ;

egg-laying habits, 238 ;

food getting, 234 ;

food of, 237 ;

gills, 234 ;

heart, 236 ;

migration, 238 ;

nervous system, 237 ;

skeleton, 237 ;

senses, 233 ;

swim bladder, 236.
Fission, 170.

Flagella of bacteria, 142.
Flatworms, 183.
Flax, 128.
Flea, 225.

Floral envelope, 35.
Flower, fertilization of, 54 ;

lengthwise section, 35 ;

use and structure, 35.
Fluid, 181.
Fly, a disease carrier, 222 ;

Fly, foot of, 223 ;

life history, 222 ;

typhoid, 223.
Foods, absorption of, 309 ;

adulteration, 288 ;

amphibia as, 202 ;

birds as, 202 ;

cost of, 283 ;

fish as, 201 ;

fruits and seeds, 119;

getting of fish, 234 ;

in cotyledons, 60 ;

inorganic, 274 ;

inspection, 380 ;

is alcohol a food, 289 ;

leaves, 117, 118;

making in green leaf, 93 ;

mammals as, 202 ;

of animal origin, 279 ;

of bacteria, 144 ;

of fishes, 237 ;

of insects, 33 ;

of plant origin, 278 ;

of starfish, 216 ;

reptiles as, 202 ;

roots as, 119;

stems as, 118;

taking, 181 ;

tube of frog, 243 ;

values, tables, 276 ;

waste in kitchen, 287 ;

why we need, 272.
Foraminifera, 182.
Forestry, 113.
Forest destruction, 112, 113;

fires, 112;

of North Carolina, 105 ;

other uses, 109 ;

protecting, 114 ;

regions of United States, 109.
Formaldehyde, 148.
Formation of habits, 354.
Four o'clock embryo, 103.
Fresh air, 337.
Frog, adaptations for life, 241 ;

and man, digestive tract, 297 :

breathing, 242 ;

circulation, 243, 322 ;

development of, 244 ;

INDEX

425

Frog, diagram of tongue, 242 ;

food tube, 243 ;

glands, 243 ;

locomotion of, 241 ;

long section, 243 ;

metamorphosis, 245 ;

nervous system, 352 ;

sense organs, 242.
Fruit, a typical, 55.
Fruit of locust, 55.
Fruits and seeds as foods, 119.
Fruits, how scattered, 56.
Fuel, daily needs, 284.
Fuel values of nutrients, 277.
Functions, of all animals, 180 ;

of an animal, 48 ;

of bile, 307 ;

of blood, 313 ;

of cerebrum, 353 ;

of colorless corpuscle, 316 ;

of lymph, 317 ;

of parts of plant, 48 ;

of red corpuscle, 314.
Fungi, 130, 176;

moldlike, 135;

of our homes, 132.
Fur-bearing animals, 204.

Gall bladder, 306 ;

insects, 208.
Gallflies, 43.
Ganoids, 186, 187.
Garbage cans, 377.
Garden fruits, 123.
Gastric glands, 303 ;

of frog, 243.
Gastric juice, 303.
Gastrula, 177, 178.
Genus, 175.
Geranium, 45.
German forest, 114.
Germ cells, 251.
Germination, of bean, 63 ;

of pollen, 54.
Gills of fish, 234 ;

rakers, 172, 234.
Glands, 297, 298, 299 ;

gastric, 303 ;

lymph, 324 ;

Glands of frog, 243 ;

salivary, 299.
Glomerulus, 341.
Glottis of frog, 243.
Glycogen, 307.
Gonorrhea, 156.
Grafting, 256.
Grains, 122.

Grape sugar, test for, 68.
Gravity, influence on root, 72.
Green plants, economic value, 117

give off oxygen, 95 ;

harmful, 127;

make starch, 90, 92.
Groups of plants, 174.
Guano, 82.
Guard cells, 88.
Gullet, 297, 300, 301, 302, 303 ;

of frog, 243.
Gymnosperms, 176.
Gypsy moth, 215.

Habits, 354.

Habitat of protozoa, 172.

Habit formation, 354.

Haemoglobin, 314, 330.

Hammer, 359.

Hard palate, 301.

Harm done by insects, 34, 225.

Harmful green plants, 127 ;

preservatives, 148.
Hay infusion, 163, 164.
Head of a bee, 38.
Heart a force pump, 320 ;

diagram, 319 ;

in action, 319 ;

internal structure, 319 ;

of fish, 236;

size, position, 318.
Heat, and bacteria, 145 ;

effect of, 22 ;

output, 285.
Heating the house, 375.
Hemiptera, 32.
Hen's egg, 246.
Herbivorous animals, 213. .
Heredity, and evolution, 404 ;

bearers of, 251 ;

definition, 249 ;

426

INDEX

Heredity, relation of alcohol to, 372.

Hervey, William, 399.

Hibernate, 22.

Hides, 205.

Hilum, 59.

Honey and wax, 207.

Hookworm, 183, 228, 229.

Horse, ancestor of, 193, 260.

How food is swallowed, 302.

Human blood, 314.

Human body, a machine, 267 ;

composition of, 21.
Human physiology, definition, 15.
Humming bird, 43. .
Humus, 79.

Hundred calorie portions, 286.
Huxley, 398.
Hybridizing, 254.
Hybrids, 254.
Hydra, 179.
Hydrochloric acid, 303.
Hydrogen of water, 20, 20.
Hydrophobia, 392.
Hygiene, 27 ;

of breathing, 338 ;

of skin, 344 ;

of mouth, 302 ;

of muscles and bones, 268 ;

outline, 415 ;

personal, 261.
Hypocotyl, 59.
Hymenoptera, 30.

Ichneumon fly, 208.
Illness of drinkers, 363.
Imperfect flowers, 44, 45.
Immunity, 157, 390.
Improvement, by selection, 253 ;

of man, 261.
Impure water, 289.
Incisors, 301.

Infectious diseases, 27, 363, 390.
Infusoria, 182.
Inner ear, 359.
Inoculation, 157.
Inorganic soil, 77 ;

foods, 274.
Insects, 185;

and foods, 376 ;

Insects, as disease carriers, 225 ;

as pollinating agents, 36 ;

damage done by, 34, 214 ;

diagram of, 29 ;

food of, 33 ;

of the house, 216 ;

orders of, 30.
Inspection, of factories, 379 ;

of raw food, 380.
Instincts, 195.
Internal secretions, 317.
Intestinal fluid, 306 ;

glands, 308.
Intestine, large, 309.
Invertebrates, 185.
Iris, 360.
Isolation, 390.

Jenner, Edward, 400.
Jimson weed, 128.
Jukes, 261.

Kidney bean, 59, 63.
Kidneys, 181 ;

human, 341 ;

of frog, 243.
Kinetic energy, 267.
Knots, 112.
Koch, Robert, 403.

Labor, division of, 178.
Laboratory equipment, 418.
Lacteals, 309, 324.
Lactic acid, 150.
Lactometer, 288.
Ladybug, 209.
Large intestine, 309 ;

of frog, 243.

Larva of milkweed butterfly, 32.
Latent energy, 267.
Lateral line, 234.
Leaves, as food, 117;

evaporation of water from, 85 ;

cell structure of, 85 ;

mosaic, 90 ;

respiration, 96 ;

section, 49;

skeleton of, 85 ;

structure, 85, 86.
Length measures, 417.

INDEX

427

Leopard frog, 188.
Lepidoptera, 30.
Levers, 269.

Life comes from life, 399.
Life cycle, 104 ;

of plants, 103.

Life history of malarial parasite, 217.
Ligaments, 268.
Ligature, applying, 326.
Light, a condition of environment,
21, 22;

and bacteria, 145 ;

effect of, 22 ;

necessary for starch making, 91.
Lighting the home, 376.
Lily, narrow leaves, 90.
Limewater test, 64.
Lister, Sir Joseph, 403.
Liver, 306 ;

a storehouse, 307 ;

effect of alcohol on, 312 ;

of frog, 243.
Living matter and alcohol, 291 ;

plant and animal compared, 47 ;

things, needs of, 266 ;

things, varying sizes of, 51.
Lizard, 188.
Lobster, 198.
Locomotion, 181 ;

of frog, 241.

Lowell, typhoid area, 384.
Lumber transporting, 110-111.
Lungs, air passages, 330 ;

changes of blood in, 330.
Lymph, function, 317 ;

glands and vessels, 324, 325.
Lysol, 148.

MacNichol, Dr. T. Alexander, 327.

Macronucleus, 169.

Malaria, cause, 217.

Malarial mosquito, 218.

Malarial parasite, life history, 217.

Mammal development, 247 ;

embryo, 247.
Mammals, 191 ;

adaptations, 192 ;

as food, 202 ;

classification, 192.

Mammary glands, 191.

Man, animals that prey upon, 230 ;

and his environment, 266 ;

circulation of blood, 318 ;

improvement of, 261 ;

in his environment, 26 ;

mouth cavity, 300 ;

place in nature, 195 ;

races of, 196 ;

stomach, 303.
Manufacture of fats, 93.
Measures, 417.

Mechanics of respiration, 332, 333.
Membrane, mucous, 299.
Mendel, Gregor, 257, 406.
Mesenteric glands, 309.
Mesentery, 297.
Mesoderm, 177.

Metamorphosis of frog, 244, 245.
Metchnikoff, 316.
Methods, of cutting timber, 111;

of breathing in vertebrates, 232.
Micronucleus, 169.
Micropyle, 59.
Middle ear, 359.
Migration of fishes, 238.
Milk, and tuberculosis, 381 ;

composition of, 273, 280 ;

germs in, 381 ;

grades of, 381 ;

under microscope, 150, 305.
Milkweed, butterfly, 32, 33.
Milling and starch making, 92.
Mink, 205.
Mixed diet, 284.
Moisture, 24, 78.
Mollusca, 185.
Mollusk, 185.
Mold, 133, 134, 135 ;

yeast and bacteria, 143.
Morning glory embryo, 103.
Mosquito, malarial, 218;

yellow fever, 219.
Moss plant, 177.
Mother of pearl, 206.
Motor nerves, 351.
Mouth cavity in man, 300, 300.
Mouth parts of bee, 38.
Mucous membrane, 299.

428

INDEX

Mucus cells, 299.

Muscles and bones, hygiene, 268.

Mutations, 253, 406.

Mutual aid between flowers and

insects, 41.
Mycelium, 133.
Myriapoda, .185.

Natural environment, 25 ;

selection, 253.
Nectar, 35.
Need, of food, 272 ;

of sleep, 356 ;

of ventilation, 335.
Needs of living things, 266.
Nerve cells and fatigue, 356 ;

vasomotor, 325.
Nervous control, 181 ;

of heart, 325 ;

of respiration, 334 ;

of sweat glands, 343.
Nervous system, 271, 349 ;

of frog, 352.
Neuron, diagram, 351.
Newt, 187.
Nicotine, 293.

Nictitating membrane of frog, 242.
Nitrates, 80.
Nitric acid, 61.
Nitrogen, 80 ;

cycle, 162;

fixing bacteria, 80, 81, 151 ;

of air, 20.
Nodules, 81.

Normal heat output, 285.
Nose and throat, diseases, 340.
Nucleus, 50.
Nutrients, 273, 274 ;

fuel values, 277 ;

in common foods, 275.

Object of a field trip, 28.
Oils, test for, 61.
Operculum, 234.
Ophidia, 189.
Orbit of eye, 360.
Orchard fruits, 124.
Organic matter, 64.
Organic nutrients, 60.

Organisms, 47.
Organs, 47, 48, 180 ;

of Corti, 360 ;

of excretion, 340 ;

of hearing, 358 ;

of respiration, 330 ;

of taste, 358 ;

of touch, 357.
Orthoptera, 30.
Osmosis, definition, 75 ;

experiment, 100 ;

physiological importance, 77.
Ostrich, 191.

Outline of courses, 407-414.
Ovaries of frog, 243.
Ovary, 36.
Ovules, 54.
Oxidation, 64 ;

in our bodies, 65.
Oxygen cycle, 161 ;

given off by green plants, 95 ;

of air, 20 ;

of water, 20.
Oyster, 199, 200.

Packard (zoologist), 33.
Palate, hard and soft, 301.
Palisade tissue, 86.
Pancreas, 305 ;

of frog, 243 ;

work of, 305.
Papillae, 301.
Pappus, 57.
Paramoecium, 167, 168, 169;

needs of, 266 ;

response to stimuli, 167.
Parasites, 131.

Parasitic animals cause disease, 227.
Parasitism, cost and remedy, 263.
Parotid, 299.
Pasteur, Louis, 401.
Pasteurization, 146.
Pea pod, 55.
Pearls, 206.
Pectoral fin, 233.
Pelvic fin, 233.
Pepsin, 303.
Peptic gland, 304.
Perfumes, 205.

INDEX

429

Pericardium, 319.

Peristaltic waves, 303.

Personal hygiene, 261.

Perspiration, 343.

Petals, 35.

Petri dishes, 140.

Phagocytes, 316.

Pharynx, 301.

Phenolphthalein, 80.

Phosphoric acid, 82.

Photosynthesis, 92, 93.

Physiology of mold, 133.

Pistil, 36.

Pith, 97.

Placentae of mammal, 247.

Plankton, 235.

Plants, animals depend on, 34 ;

and animals, mutually helpful, 18 ;

classification, 176 ;

food for insects, 33 ;

as food makers, 88 ;

function of parts, 48 ;

groups, 174;

need minerals, 80 ;

need of nitrogen, 80, 82 ;

processes, 103;

reproduction, 173.
Plasma, 313.

Plasmodium malarias, 182, 217.
Pleura, 332.
Pleurococcus, 166.
Plumule, 59.
Pneumonia, 336.
Pocket garden, 73.
Poison, alcohol, 291 ;

ivy, 128;

produced by alcohol, 347.
Polar bear, 204.
Pollen, 36 ;

germination of, 53, 54.
Pollination, 36, 40 ;

cross and self, 40 ;

wind, 44.
Pond scum, 173.
Pons, 352.
Porifera, 182.

Portal circulation, 309, 322.
Portions, hundred calorie, 286.
Potato beetle, 214.

Potato beetle, embryo, 103.
Premolars, 302.
Preservatives, 147.
Prevention -of dyspepsia, 310 ;

of molds, 134.
Proboscis, 30.
Prolegs, 32.
Pronuba, 42, 43.
Protecting forests, 114.
Proteins, 60, 273 ;

making, 93 ;

test for, 61.
Protoplasm, 50 ;

what it can do, 52.
Protozoa, 172, 182, 205.
Protozoan diseases, 221.
Pteridophytes, 176.
Ptomaines, 144, 147.
Ptyalin, 300.
Public hygiene, 389.
Pulmonary circulation, 320.
Pulse, cause, 323.
Pupa of milkweed butterfly, 33.
Pupil of eye, 360.
Pure food laws, 288.
Purpose of digestion, 69, 296.
Pyloric caeca, 235.

Quarantine, 27, 390.

Rabies, 392.

Races of man, 196.

Radiolaria, 182.

Radiolarian skeleton, 182.

Recessive characters, 258.

Rectum, 297.

Red corpuscles, 313, 314.

Reflex actions, 353.

Regulation of heat of body, 343.

Relation, of age to diet, 280 ;

of alcohol to crime, 371 ;

of alcohol to heredity, 372 ;

of alcohol to pauperism, 371 ;

of animals to man, 17 ;

of bacteria to free nitrogen, 81

of bacteria to man, 16 ;

of biology to society, 18 ;

of cost of food to diet, 281 ;

of digestibility to diet, 281 ;

430

INDEX

Relation, of environment to diet,
280;

of green plants and animals, 15,
161, 162;

of sex to diet, 280 ;

of work to diet, 277 ;

of yeasts to man, 135.
Rennin, 303.
Reproduction, 103, 181 ;

importance of, 52 ;

in seed plants, 173, 174 ;

of cells, 50 ;

of Paramoecium, 169.
Reptiles, 186.
Reptilia, 188.
Reserve air, 334.
Residual air, 334.
Respiration, 66, 181 ;

and alcohol, 346 ;

and nervous control, 334 ;

and tobacco, 346 ;

mechanics of, 332, 333;

necessity for, 329 ;

organs of, 330 ;

of cells, 332 ;

of leaves, 96.
Retina, 360.
Rhizoids, 133.
Rhizopoda, 182.
Rice field, 123.
Ringworm, 134.
Roaches, 216.
Rock fern, 175.
Rockweed, 176.
Roots as food, 119;

as food storage, 83 ;

downward growth of, 72 ;

fine structure, 73 ;

give out acid, 79, 80 ;

hairs, 74, 75 ;

influence of gravity, 72 ;

influence of moisture, 73 ;

passage of soil water, 76 ;

pressure, 101 ;

system, primary, secondary, ter
tiary roots, 72 ;

uses of, 71.
Rotation of crops, 81.
Roundworms, 183, 228.

Rules of habit formation, 356.
Russian thistle, 129.

Saliva, 69, 299.
Salivary glands, 299 ;

glands of frog, 243.
Salmon, 201, 241.
Sand shark, 186.
Sandworm, 184.

Sanitarium for tuberculosis, 394.
Sanitation, 27.
Saprophytes, 131.
Scavangers, 150.
Schleiden and Schwann, 398.
Schultz, Max, 398.
Sclerotic coat, 360.
Sea anemones, 183.
Secretion, 299, 308.
Secretions, internal, 317.
Section, of ear, 359 ;

of timber, 111.
Sedgwick, William T., 312.
Seed, 54 ;

how scattered, 56 ;

plants, reproduction, 174 ;

why it grows, 58.
Seedlings of bean, 63.
Segmented worms, 183.
Selection, artificial, 253 ;

natural, 253.
Selective planting, 254.
Semicircular canal, 359.
Sensations, 350.
Sense organs, 181 ;

of fish, 233 ;

of frog, 242.
Senses, 357.
Sensory nerves, 351.
Sepals, 35.
Series, animal, 182.
Serum, 314.
Sewage disposal, 386.
Sex, relation to diet, 280.
Shelf fungi, 132.
Sieve tubes, 97. '
Simple animal, development, 177.
Simplest plants, 166.
Skeleton, of dog, 185 ;

of fish, 237 ;

INDEX

431

Skeleton, of leaf, 85 ;

of man, 268.
Skin, 268 ;

hygiene of, 344.
Skunk, 205.
Sleep, need of, 356.
Small intestine, 307, 308.
Smell, sense of, 358.
Snail, 185.
Snakes, 189;

food of, 212.
Soft palate, 301.
Soil, composition of, 77 ;

how water is held in, 77, 78.
Sound, character of, 360.
Sour bread, 139.
Soy beans, 152.
Sparrow, 246.

Spawning habits, economic impor
tance, 239.
Species, 175, 194.
Sperm, 177.

Spermaries of frog, 243.
Spermatophytes, 176.
Spinal cord of fish, 237.
Spiracles, 29.
Spirillum, 142.
Sponge, 180, 182, 183, 208.
Spore, 131, 173;

plants, 174.
Sporozoa, 182.
Sprengel, Conrad, 40.
Squash bug, 215.
Stables, clean and filthy, 388.
Stamens, 36.
Starch, action of diastase, 69 ;

digestion, 299 ;

grains, 60;

in bean, 61 ;

made by green leaves, 90, 92 ;

test for, 61.

Starch making and milling, 92.
Starfish, 184;

food of, 216.
Stegomyia, 221.
Stems, as food, 118;

passage of fluids up, 84 ;

structure of, 97.
Sterilization, 145.

Sterilizer, 140.
Stigma, 36.
Stimulants, 289.
Stirrup, 359.
Stomata, 86, 88.
Stomach, 297 ;

digestive experiments, 304 ;

of frog, 243 ;

of man, 303.

Street cleaning department, 387.
Structure, colorless corpuscles, 315

of leaf, 85 ;

of red corpuscle, 314 ;

of root, 73 ;

of root hairs, 74.
Sturgeon, 186.
Style, 36.

Sublingual glands, 299.
Submaxillary glands, 299.
Suffocation, 340.
Sulphur, 149.
Sun, source of energy, 88.
Sundew, 102.
Sunlight in home, 374.
Sweat glands, 342.
Sweeping and dusting, 336.
Swim bladder of fish, 236.
Symbiosis, 163.
Sympathetic nerves, 352 ;

nervous system, 304, 350.
Syphilis, 152, 156.
Systemic circulation, 320.

Table of cost of food, 276, 283.
Tactile corpuscles, 357.
Taenia solium, 227.
Tapeworm, 227.
Taproot, cross section, 74.
Taste buds, 301, 358.
Teeth, 301.
Teleosts, 187.
Temperature, 417 ;

of blood, 318.
Tern, 190.
Testa, 59.
Test, for carbon dioxide, 64 ;

nutrients, 61, 68.
Thallophytes, 176.
Thoracic duct, 324.

432

INDEX

Tidal air, 334.

Timber, methods of cutting, 111.

Tissue cells, 49, 179.

Toad, use of, 209.

Tobacco and circulation, 328 ;

and respiration, 346 ;

users of, 293.
Tortoise, 188.
Touch, 357.
Tourniquet, 326.
Toxin, 152, 316.
Trachea, 185.
Transpiration, 85,. 87.
Transportation of lumber, 110, 111.
Treatment of cuts and bruises,

326.
Trees, need of city, 115 ;

preventing erosion, 108 ;

regulate water supply, 105 ;

value of, 105.
Trichina, 228.
Trichinosis, 228.
Trillium, 175.
Trout, development, 238.
Trypanosomes, 221.
Tuberculosis, 152, 153;

and milk, 381 ;

how to fight, 393, 394.
Tussock moth, 215.
Twig, section of, 98.
Tympanic membrane, 358.
Tympanum of frog, 242.
Tyndall box, 399.
Typhoid, 224, 385;

and diarrhea, 200.
Typhoid fever, 152, 155, 382.

Unit characters, 258.
Ureter, 342.
Urethra, 342.
Urine, 341.
Urodela, 188.
Uses, of animals, 198 ;

of antibodies, 316 ;

of green plants, 117 ;

of ice, 377 ;

of nutrients, 274 ;

of protozoa, 172.
Uterus of a mammal, 247.

Vaccination, 157, 221, 391.
Vacuoles, contracting, 168.
Value, of insects, 208 ;

of trees, 105.
Valves, 185, 319 ;

in vein, 324.
Variation, 250.
Vasomotor nerves, 325.
Vegetable fibers and oils, 127.
Veins, 318 ;

function and structure, 323 ;

valves, 324.
Venae cavae, 322.
Ventilation, 335, 338.
Ventricle, 319 ;

of fish heart, 236.
Venus fly trap, 102.
Vermiform appendix, 309.
Vertebral column, 183.
Vertebrates, breathing of, 232.
Villi, 308.

Virginia creeper, 128.
Virus, 392.
Vitreous humor, 361.
Vorticella, 171, 178.
Vries, Hugo de, 253, 403.

Warner, Chas. Dudley, 211.
Waste of food, 287.
Water, 275 ;

composition of, 20 ;

impure, 289 ;

supply, 383.
Weed, 48, 128.
Weights, 417.
Wheat crop, 121, 122.
Wild orchid, 40.
Windpipe, 300, 301.
Wood, uses of, 110.
Work of cells, 270 ;

of Department of Agriculture, 255

relation to diet, 277.
Worms, 183.

Yeasts, 136, 138, 139 ;

relation to man, 135.
Yellow fever mosquito, 219.
Yucca, 42, 43.

Zygospore, 174.