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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 



BY 

GEORGE WILLIAM HUNTER, Pii.D. 

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 



Copyright, 1914, by 
GEORGE WILLIAM HUNTER. 

Copyright, 1914, in Great Britain. 



HUNTER, CIVIC BIOLOGY. 

W. p. 12 



DeMcateb 

TO MY 

FELLOW TEACHERS 

OF THE DEPARTMENT OF BIOLOGY 

IN THE DE WITT CLINTON HIGH SCHOOL 

WHOSE CAPABLE, EARNEST, UNSELFISH 

AND INSPIRING AID HAS MADE 

THIS BOOK POSSIBLE 




17530 



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 unkno^\Ti 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 naind of the teacher because of his wider horizon, mijan 



HOfERTY LIBURY 



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-laboratory 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 Hfe. 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 accomphsh 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. H. 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 Awitten. 
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. WllHam 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, m.ade many of the fine dra^vings 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, 
pubHshed 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 PAGB 

Foreword to Teachers 7 



15 

19 

'28 
47 



I. Some Reasons for the Study of Biology 
II. The Environment of Plants and Animals . 

III. The Interrelations of Plants and Animals 

IV. The Functions and Composition of Living Things 
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 
XI. Plants without Chlorophyll in their Relation to 

Man 180 

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 .... 2(56 

XIX. Foods and Dietaries 272 

XX. Digestion and Absorption 296 

18 



14 CONTENTS 

CHAPTEB PA3E 

XXL The Blood and its Circulation 313 

XXII. Respiration and Excretion 329 

XXIII. Body Control and Habit Formation .... 348 

XXIV. Man's Improvement of his Environment . . . 373 
XXV. Some Great Names in Biology 398 

APPENDIX 407 

Suggested Course with Time Allotment and Sequence 

OP 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 Tempp:ratures . . . 417 

Suggestions for Laboratory Equipment . . . 418 

INDEX c 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. 

15 



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. Phmts furnish man with the greater part of his food 
in the form of grains and cereals, fruits and nuts, edible roots and 
h'aves ; they provide his domesticated animals with food ; they 
giv(» 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 i^lants vitall}^ 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 
])utter ; 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 olj^ier 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,~^nd are in many places barren. On the forests 
depend our supply of timber, our future Avater power, and the 
future commercial importance of cities which, like New York, are 
located at the mouths of our navigable rivers. 

HUNTER. CIV. BI. — 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 livjB. 
Thus the application of biological principles will benefit society. 



11. THE ENVIRONMENT OF PLANTS AND ANIMALS 



Problem, — To discover some of tlie factors of the environ- 
ment of plants and animals. 
(a) Environment of a plant. 
ib) Environment of an animal. 
(c) Hojne 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 Hves, 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 
well, are surrounded by and use prac- 
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- 

19 




An unfavorable city environ- 
ment. 



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 cheynical com- 
poimd. The oxygen and nitrogen of 
the air are not so united, but exist as 
separate gases. If we were to study 





1 




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 

PHOSPHORU5I 
CALCIUM 




NITROGEN 
3.7s Iks. 



0.031U %,o% 
SiGXts. y-jir 



HYDROGEN 

I3.65\bs. 

9.1^ 



CARBON 

13.5^ 




OXYGEN 

I08.l5lb5. 



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 and 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. 
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 



<f^ 



Chart to show the percentage 
of chemical elements in the 
human body. 



22 ENVIRONMENT OF PLANTS AND ANIMALS 




TliL' effect of water upon the growth of trees. These trees were all planted at the 
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 
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 




The effect of light upon a growing plant. 



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 



FmrERTY UBRART 



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, ^ ^^^^^^j ^^^^.^^ ^^^ ^ ^t,^^,,, 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-ot-door ,. i . 

sleeping porch. plied m 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. 

(b) 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. 

28 



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 less 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 

^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 nei'ds, 

^ ^ ■ on grass, or on flowering plants we may count on 

finding members from six groups or orders of insects. These may 

be kno^vn 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 
Orthoptera; o, the egg-layer, about natural size. B, the honey bee, one of 
the Htjmenovtera, about natural size. C, a bug, one of the Heyniptera, 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 pairt-j 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 
to follow her instinct 
to deposit her eggs on 
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 




Monarch butterfly: adults, larvse, and pupa on their 
food plant, the milkweed. (From a photograph 
loaned by the American Museum of Natural 
History.) 



34 INTERRELATIONS OF PLANTS AND ANIMALS 




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



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 
dogs 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 
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 |)etals 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 structured, the 
stamens; the knobs at tlie end 
contain pollen. The outer circles 
of parts arc 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 filaw,ent. 
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, a, queen; 6, 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 honej^ 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 witli 
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 
eggs." 

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 its head and shoulders against 
the stamens. It may then, as it 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 (A^) it brushes against the stit-ima (.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 a7ither 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 neetar 
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 the 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 o^vn 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 




The condition of stamens and pistils on the spiked 
loosestrife {Lythrum salicaria). 



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 thtee 
lengths. Pollen only 
grows on pistils of the 
same length as the 
stamens from which it 
came. 

The milkweed or 
butterfly weed already 
mentioned is another example of a flower adapted to insect pol- 
lination.^ 

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- 




The pronuba moth within the 
yucca flower. 



^ For an excellent account of cross-pollination of this 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. 



INTERRELATIONS OF PLANTS AND ANIMALS 43 





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 "f^^^ *^^ p^*^ 

^ of the yucca. 

growers of California have 
T, , . , . discovered that the fertilization of the female 

Pod of yucca showing 

where the young pro- flowcrs 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 ^ ^^^^^,,^ bird about to cross-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 becoms 
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-polUnation. 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 inay 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, pages 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 Comstock Publishing Company. 
Newell, A Reader in Botany, Part II, pages 1-96. Ginn and Company. 
Sharpe, A Laboratory Manual in Biology, pages 43-48. American Book Company. 

ADVANCED 

BaUey, 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 Floioers 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 

rroblems. — To discover the functions of living matter. 
(a) In a living plant, 
(6) 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 matm'e 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 i)lants and 

animals are spoken of as living organisms. 

47 



48 



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 



49 



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.^ — The cells which 
form certain parts of the veins, 
the flat blade, or other portions 
of the plant, are often found in 
groups or collections, the cells 
of which are more or less alike 




Several cells of Elodea, a water plant. 
chl., chlorophyll bodies; c.s., cell sap; 
C.W., cell wall ; n., nucleus ; p. proto- 
plasm. The arrows show the direc- 
tion of the protoplasmic movement. 



^ 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 ca." 
be demonstrated. 

HUNTER, CIV. BI. — 4 



50 FUNCTIONS OF LIVING THINGS 

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 protoplasrro (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," however, is really a plant cell 



-CltA. 




iT'V:.-v. ■ • "(iv- :•; ••••':K 
ivX'afe-" .■•-■••.':■; •.■':'.-'V-.J 



A ceu. ch., chromo- bounded by a thin Wall. If we look carefully, 

somes; c.«\, celJ wall ; "^ ... . 

n., nucleus ; p., proto- we Can See that the material inside of this wall 
^ ^^' 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 



51 





Stages in the division of one cell to form two. 
Which part of the cell diAddes first ? What seems 
to become of the chromosomes ? 



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 
can easily be seen with 
the unaided eye ; for 
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 fcells. 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 fresli 
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 coid, 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. 

Protoplasrn 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 limng 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 the kidneys. 

Protoplasm can reproduce, that is, form other matter 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 



53 



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 i)ollen 
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 L5 
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. 




A pollen grain greatly magnified. 
Two nuclei are found {n, n) at 
this stage of its growth. 



FUNCTIONS OF LIVING THINGS 




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 syenn 

Three stages in the germination of the pollen UUCieus. 

grain. The nuclei in the tube in (3) are Fertilization of the 
the sperm nuclei. Drawn under the com- 
pound microscope. Flower. — It 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. A flower 
, , ^ cut down lengthwise (only one 

through the spongy center of the side shown). The pollen tube is 

style, follows the path of least resist- ^f^"" entering the ovule, a, an- 

. , 1 . , , . , , ther ; /, filament ; pg, pollen gram; 

ance to the space Wlthm the ovary, s, stigmatic surface ; pt, poUen 

and there enters the ovule. It is tube ; sf, style ; o, ovary ; m, micro- 

. . . ^ pyle; sp, space withm ovary; 

believed that some chemical influ- e, egg cell ; P, petal ; s, sepal. 




FUNCTIONS OF LIVING THINGS 



55 



ence thus attracts the pollen tube. When it reaches the ovaiy, 
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 ovide 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 



s — 




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



56 



FUNCTIONS OF LIVING THINGS 



ovary and its contents together with any parts of the flower that may 
he 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 
9,id 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 jjlant to grow ? 
(a). The relation of the young plant to its food supply, 
ih) The outside conditions ivecessary for germination. 

(c) What the young plant does with its food supply. 

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

(e) How a plant or aniinal prepare 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, 

5S 



PLANT GROWTH AND NUTllITION 



59 



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 tirfy 
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 above 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 (CeHioOs 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, 
Starcii grains in the cells proteins, are the most complex of all in 

of a potato tuber. , i • • , • i i i • 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,^ 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 



61 




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. 




V^ V^ 



Test for protein. 



62 



PLANT GROWTH AND NUTRITION 



If the protein is in a liquid state, its presence may be proT^ed 
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.^ 

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 



Food Materials as Purchased 



Kidney beans, dried 

Lima beans, fresh, shelled . . . 

Lima beans, dried 

String beans, fresh, 30 cents per 

peck 

Beans, baked, canned . . . . 

Lentils, dried 

Peas, green, in pod, 30 cents per 

peck 

Peas, dried 



Prices 

PER 

Pound 



Cents 

5 

8 
6 

3 

5 

10 

3 
4 



Ten Cents will pay- fob — 



Total 

Food 

Material 



Pounds 

2.00 
1.25 
1.67 

3.33 
2.00 
1.00 

3.33 
2.50 



Proteid 



Pounds 

0.45 
.04 
.30 

.07 
.14 
.26 

.12 
.62 



Fat 



Pounds 

0.04 

.03 

.01 
.05 
.01 

.01 
.03 



Carbo- 
hydrates 



Pounds 

1.19 

.12 

1.10 

.23 
.39 
.59 

.33 
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 



63 



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 

. 1 ^ mi J. Bean seedlings. The older seedlings at 

cotyledons. The stem, as ^^^ ^^^^ ^^^^ ^sed 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- 
hke 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 ^\ ^e then Carefully test the air in the jar 
tube at the right shows with a substance known as limewater,^ the 
dioxide.^ ° ^ ^^^ °^ latter, when 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 



65 





Diagram to show that when a piece of 
wood is burned it forms water and 
carbon dioxide. 



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 
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 



66 



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- 
])on 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- 
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. 



Experiment that shows the necessity for air in 
germination. 




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



PLANT GROWTH AND NUTRITION 



67 



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 Longitudinal section of 
growing. This is noticed in sprouting barley young ear of corn, 
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. 




stigmas : SH, the 
sheath-like leaves : 
ST, the flower stalk. 
(After Sargent.) 



68 



PLANT GROWTH AND NUTRITION 




+ 

Test for grape sugar. 



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/ 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 

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



PLANT GROWTH AND NUTRITION 



69 




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.h., 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 CandoUe, 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 (i plant takes froin the soil and how it gets 
it. 

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

(h) Hoiv is the root built ? 

(c) How does a root absorh water ? 

id) What is in tl%e soil that a root might tahe owt ? 

{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 gfravity 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 ^\^th 
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 sho^vn 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 ichere 
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- 

71 



72 



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 *!^"^^ ^^ *^^^ arrows t^ see if 

^ the roots of the radish re- 

by the force of gravity. spond to gravity. 



^^^^^^^^^^^^^^^^^^^^^r k- ^^^^^B 


■ < 




m 





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 ^ 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.- — 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 cnt four thin strips of 
wood to fit on the glass just outside of the paper. Next moisten th(^ blotter, place 
on it some well-soaked radish, nmstard seeds or barley grains, and cover with the 
other glass. The whole box thus made should be l)ound 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. 



74 



SOIL AND ITS RELATION TO ROOTS 




Cross section of a young taproot; 
a, a, root hairs ; b, outer layer of 
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- 
13orting woody cells together make 
up what are known as fihrovascular 
bundles. 

Root Hairs. — Careful examina- 
tion of the root of one of the seed- 
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 
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 




Young embryo of corn, show- 
ing root hairs (R. H.) and 
growing stem (P.)- 



SOIL AND ITS RELATION TO ROOTS 



75 




Diagram of a root hair; CS, cell sap; CW, cell 
wall ; P, protoplasm ; A^, 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 fnade 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 
hy 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 



7G 



SOIL AND ITS RELATION TO ROOTS 



the same process. It is by osmosis. The white of the egg is the 
best possible substitute for Uviiig matter ; the celloidin membrane 
separating the egg from the water is much hke the dehcate mem- 
brane-hke 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.^ 

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 

^ 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 



77 



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. 



78 



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, 




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



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 
forms the portion called 
humus. 

Humus contains Or- 
ganic Matter. — It is an 




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



SOIL AND ITS RELATION TO ROOTS 79 




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 phenolphthalein 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? 



80 



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 gro\vth of seed- 
lings in a so-called nutrient solution.^ 
Such a solution contains all the mineral 
matter that a plant uses for food. If 
certain ingredients are left out of this 
I^M WB solution, the plants placed in it will not 

VT^ ^w live. 

i"-^-"^ — -^ r — -^rrzz a — 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 mtrogeu. 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 

^ 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 
i? heated artificially or treated with antiseptics so as to kill the protozoa, the bac- 
teria which escape mxiltiply so rapidly as to make the land much richer than before- 




SOIL AND ITS RELATION TO ROOTS 



81 



Relation of Bacteria to Free Nitrogen. — It Las 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 
of these nitrogen-fixing bac- 
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 




Diagram to show how the nitrogen-fixing 
bacteria prepare nitrogen for use by 
plants; t, tubercles. 



82 



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. ^ 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 




Nitrogen in the soil is necessary for plants. 
Explain from this diagram how nitro- 



gen is put into the soil by some plants which contain nitrogen in the 
and taken out by others. . , . i 

form oi 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 mankmd. 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 Manvxxl 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, wlien, and how green plants malce food ? 

(a) How and why is moisture given off from leaves ? 

(b) W1^at is the reaction of leaves to light ? 

(c) What is 'made iiv green I eaves in the sunlight? 

id) 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 FOOD 



85 



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. Obvi- 
ously the loss 
comes from the 





Experiment to prove that water 
is given off through the leaves 
of a green plant. 



The skeleton of a leaf. M.R., 
the midrib; P., the leafstalk; 
v., the veins. 



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 hlade^ 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 
under surface of a leaf seen under the 



8G 



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.r., breath- 
ing hole (stoma); E, outer 
layer of cells; P, green cells. 



PLANTS MAKE FOOD 



87 



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 ^ — 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 ofif. 



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 

1 The "rubber plant" leaf is ap easily obtainable and excellent demonstration. 



88 



PLANTS MAKE FOOD 



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





a 




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 Hnes indicate the closed position of the guard cells, the heavy Hnes 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 li^ht comes. 



PLANTS MAKE FOOD 



89 



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 gro^vth 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. 
Lewes are often definitely arranged, fitting in between one 



90 



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 



91 



ceived from the sun, manufacture starch out of certain raw materials. 
These raw materials are soil water, which is passed up througli 
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 Hght (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 



92 



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), 




ogoo^O 




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 
mill) is also given out. This 
by-product is oxygen. To 




Diagram to illustrate the formation of 
starch in a leaf. 



Sugar is first manufactured and then transformed into starch. 



PLANTS MAKE FOOD 



93 



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 

LIGHT 



I 





Soil water 



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. 



94 



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 



95 



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.^ 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- ^^^^^^^ , ^^ ^-^^^^^^ ,^f 

^ '^ ^ ^ green plants in the sun- 

ing spaces." The green covering of the light. 

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 heli:)fulness exists between 

plants and animals. 

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




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 5-40. D. Appleton and Company. 
Covilter, 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 Mj*cmillan Company. 
Goodale, Physiological Botany, pages 337-353 and 409^24. 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 Agricultuie, 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 thei 
niahe. 

id) What are the organs of circulation ? 

{h) 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 hark. 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 hast 
fibers. The most important parts of this inner bark, so far as the 
plant is concerned, are many tubelike structures known as sieve 
tuhes. These are long rows of living cells, having perforated 

HUNTER, CIV. BI. — 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, 
we find so-called annual rings. 
The distance between one ring 
and the next (see Figure) usu- 
ally represents the amount of 
growi^h in one year. Growth 
takes place from an actively dividing layer of cells, knowTi 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 



Section of a twig of box elder three years 
old, showing three annual growth rings. 
The radiating lines (m) 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.) 



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 ^^dll 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 




Experiment to show that 
food material passes 
down in the inner bark. 



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, 
one with starch and water, the other with 
sugar and water, and a piece of parchment 
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 

. (right hand tube) and non-osmoses 

corn by the action of a substance of starch (left hand tube). 




CIRCULATION AND USES OF FOOD BY PLANTS 101 



(an enzyme) oalled 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 
a captured insect. 



The Venus fly trap, showing open 
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 





The embryos of (a) the morning glory, (b) 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 Probleyns 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 Macmillan 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, t 
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 

Proble^n. —Man's relations to forests. 

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

(Jb) What can inan 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. '6.) 

105 



i06 



OUR FORESTS 




Working to prevent erosion after the removal 
of the forest in the French Alps. 



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 
streams surrounded by 
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 
debris that the ship 
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 




V^i^: 




/ 



#- 



,/-' 



■ -^^ 






-■' -• 




,'t 



^: 



/^ 



..c- 



Erosion at Sayre, Pennsylvania, by the Chemung 
River. (Photograph by W. C. Barbour.) 



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 
httle 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." ^ 

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 

1 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. 




The forest regions of the United States. 

In winter they moderate the cold, and 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 ] umber in the West. 
A logging train. 



OUR FORESTS 



HI 



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. 




a 



Methods of cutting Timber. — A Diagrams of sections of timber. 

glance at the diagram of the sections ^' ^/^f %^*^°^: .^' ^^^f jl' a''r.^''T 
„ . . gential. (From Pmchot, U. S. Dept. 

of timber shows us that a tree may be of Agriculture.) 

cut radiallj^ 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 




Section of a tree trunk 
showing knot. 



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 eUip- 
tical markings. Quite a difference in color and 
structure is often seen between the heartwood, 
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 
their outward growth and were for some reason 
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 
from Tipio-hhnrine- trpp^ arp thinned out so as to allow the young trees 

irom neignoormg irees are ^^ ^^^ ^ ^^^^^ 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 ^s 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. 

(b) For clothing. 

(c) Other uses. 

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 
wriich 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 

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 : — 



Potato . . 

Carrot . . 

Parsnip . . 

Turnip . . 

Onion . . . 
Sweet potato 

Beet . . . 



Water 


Proteins 


Carbo- 
hydrates 


Fat 


75 


1.2 


18 


0.3 


89 


0.5 


5 


0.2 


81 


1.2 


8.7 


1.5 


92.8 


0.5 


4. 


0.1 


91 


1.5 


4.8 


0.2 


74 


1.5 


20.2 


0.1 


82.2 


0.4 


13.4 


0.1 



Mineral 
Matter 



1.0 
1.0 
1.0 
0.8 
0.5 
1.5 
0.9 



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, 
'' 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 much 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 com 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 



"^^ 




/ ^"L 



CORN 

640 to 3200 bushels per saaare mile 
oyer 3200 „ „ » » 




Indian Corn Production — Percentage 



10 
1 I 


20 


30 


40 


50 


60 70 


80 


9.0 , 


w///////////m\ 




V////WM 


v/mm 


^W//////A 


V//MW/M 




, .w/mm 



Illinois 



Iowa 



Mo. 



Neb. Ind. Kan. Tex. Ohio 



Rest of 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, oi young wheat plartt, is sifted out during 
this process and made into breakfast foods. Flour making forms 



U/ ^ 




v,^ 



/60 to 640 bushe/s per sauare mile \ 

over 640 



\W' 



10 

I 



Wheat Crop in United States — Percentage Source 

20 30 4.0 50 60 






JR. 



80 
_1 



90 



J 



± 



J. 



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



Other States 



the chief industry of Minneapolis, Minnesota, and of several oltier 
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 alcohoU 



ECONOMIC IMPORTANCE OF GREEN PLANTS 123 




A field of rice, showing tlie 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 hy 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 
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. 




Picking apples, an important crop in some 
parts of the United States. 



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 

^3 /to BO bales persaaare mile 
\over£0 . 



Cotton Crop in United States — Percentage Source 



'1.0 



20 



I^MJM^^^dmm^J^mi^ 



3.0 



40 
I 



5.0 



60 
_i_ 



7.0 



80 

_l 



90 



WWM ML 



Texas 



Georgia 



Miss. 



Alabama S.Car. 



Ark. Okla. N.C. La. Otli. 
Sta. 



[ir.'.^iy.vy//'/'/'/'^-''- 



Cotton Crop in United States — Percentage Consumption 

10 20 30 M 50 60 70 80 90 



V^//^,i//^^/ \ ' ■ I 



r ] 



J± 



United States 
North South 



Great Britain & Ireland 



Germany France It. Rest ol 

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 ME 



c o 



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 




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 




-.•DJiSP-^- 



WW" 





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 jives. 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 Companv. 



HUNTER, CIV. BT. 9 



XI. PLANTS WITHOUT CHLOROPHYLL IN THEIR 

RELATION TO MAN 

Problems, — (a) How molds and otlver saprophytic fungi do 
harm to man. 

(5) What yeasts do for mankind. 

(c) A study of bacteria with reference to 

(1) Conditions favorable and unfavorable to growth. 
(^) Their relations to manhind. 

{8) 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 experiinent 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 aniinal 
which lives at the expense of 
another living plant or ani- * 

mat 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. 
Once 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 
nimiber 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.^ 




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



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



PLANTS WITHOUT CHLOROPHYLL 



133 




Bread mold ; r, rhizoids ; s, fruiting 
bodies containing spores. 



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, cheese, 
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.^ — As we have seen, moisture is favorable 
for mold gro^vth ; 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 spores. 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. 

* 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.^ 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, (C6H12O6), into alcohol, 2 (C2H6O), and carbon dioxide, 
2(002). This chemical process is known as fermentation. 

1 See Goff and Mayne, First Principles of Agriculture, page 50, for formula of 
Bordeaux mixture. 



136 



PLANTS WITHOUT CHLOROPHYLL 




Apparatus to show effect of 
fermentation. N, molasses, 
water and yeast plants ; C, 
bubbles of carbon dioxide. 



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 
the liquid from the fermentation tube 
which contains the settlings be drawn 
off, 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- 
pearance of the protoplasm of 

which it is formed. Look for 

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 




Yeast and starch grains. Notice that the 
starch grains around which are clustered 
yeast cells have been rounded off by the 
yeast plants. How do you account 
for this ? 



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 ^vine 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 wdld 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 wdnes 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 h 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 (CO2) 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 alcohcl, 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 




STERiLizirrc 



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. 

(c) exposed in the halls of the school when pupils are not moving. 




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. 

(^) 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 
begiii 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.^ 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. 

^ 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 



PLA.NTS 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 
^^^^^C^y^^'^'^:^^^ entering. When we have suc- 
• ^^S»§A*^2.1? ^."*4t,-^ ^r^^ 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 twoo of ^^ i^^^h in 
length, and perhaps s^fo o^ ^^ 
inch in diameter. Some species 
are much larger, others smaller. A common spherical form is 
-g^^o of an inch 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, sl rod-shaped bacterium, the bacillus, and a 
spiral form, the spirillurn. 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 
GSiWed 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. 










figure to show the relative size and shape of 
(1) a black mold, (2) yeast cells, and (3) dififer- 
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 black 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 
broken down by the action of 
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 sldns, 
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 daj^s, 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. 




Growth of bacteria in a drop of impure 
water allowed to run down a sterilized 
cultvure in a dish. 



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 dra^vn 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 

BUNTEB, 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 
at long distances 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 




Pasteurizing milk. Why should this 
be done ? 



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.^ — 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 

tiie 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 
sohitions. 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 wdll 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.^ — Frequently it becomes necessary to destroy 
bacteria which cause diseases of various kinds. This process is 
called dismfeding . The substances commonly used are carbolic 
acid, formalin or formaldehyde, lysol, and bichloride of mercury, 

• 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 



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 O O I^ X T B I^ H^ 

directly influence man 1n[ I '^ !R J^^!1l E^ S 

upon the earth.. Have This shows how organic matter is broken down 

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 




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 ilegree, 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 ('()m])ounds 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, 

Microscopic appearance of ordinary milk, Continue the proceSS of fer- 

v^hTch"^.,^' th^^"^'' ^""f ^-^v""'^ mentation begun by the yeasts. 

v/nich cause the souring of milk. ^ o j j 

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 




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, 




TuljL-rck'S on tlic 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, diarrhea, 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 
cither enter the body by way of the mouth, nose, or other body 



PLANTS WITHOUT CHLOROPHYLL 



153 




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. 



openings, or through a 
break in the skin. They 
maybe 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 

Deaths from tuberculosis compared with other cQnifQrv livinff it will 
contagious diseases in the city of New York ^ ^^' 

in 1908. be almost extinct. 




154 



PLANTS WITHOUT CHLOROPHYLL 



Tuberculosis is caused by the growth of bacteria, called the 
tubercle baciUi, 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 



-400 
-300- 

- 100- 


\ 


















^ 


\ 














\ 




































18 


50 18(oO 1870 1880 1890 1900 19 


06 



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 imj^ortant not to close up mth 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 



H 



H] 



J. 



/ 



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\ 



/ 



m 



\ 



/ 
/ 



\ 



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r^'.i-4 



HYOE PARK 



DORCHESTER 






P ^ 


Ll 


i / 


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1* " 


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MILTON 



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. 
Grippe, pneumonia, 



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- 

fZ^JrvL^l^ZlT^^amm:. ^Ho°w whoopingrcough, and 

would you explain this ? Certain kinds of colds, 

all undoubtedly germ 
diseases, are contracted in a similar manner. Contact with the 
bacteria causing the disease must occur in order that a person 
take the disease. This may mean actual contact with the sick 
person or an indirect transfer of the germs by the means men- 
tioned above. The germs which cause diarrhea of babies, a disease 



PLANTS WITHOUT CHLOROPHYLL 157 

which takes such a toll of death each summer, may be prevented 
by pasteurizing the milk before using, so as to kill the harmful 
bacteria. Other diseases, as malaria, yellow fever, sleeping sick- 
ness, 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 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 after 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. 

Pruddon, Dust and its Dangers. G. P. Putnam's Sons. 

Pruddcn, The Story of the Bacteria. G. P. Putnam's Sons. 

Ritchie, Primer of Sanitation. World Book Company. 

Sharpe, Laboratory Manualin 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 Bar>', 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. 

(b) As shown in hay infusion. 

Suggestions for 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. -7- 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 bj-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 swiirtfiing 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 



Ll^ 




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- 
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 
and Animals. — What goes on in 
the aquarium is an example of the 
relation existing between all green 
plants and all animals. Every- 
where in the world green plants 
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 



This diagram shows that plants and 
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. 




Energy 
(itav) 



The carbon and oxygen cycle in the 
balanced aquarium. Trace by 
means of the arrows the carbon 
from the time plants take it in 
as CO2 until animals give it off. 
Show what happens to the ox;ygen. 



162 THE RELATIONS OF PLANTS TO ANIMALS 



directly ii])oii plants, lie eats the flesh of i)lant eating animals, 
which in turn feed directly upon i)lants. And so it is the world 
over; the j^lants are the food makers and supply the animals. 



Carbon dioxide 
(COo) 



Carbon dioxide 
A (COo) 



Water 

v(H«0) 



Water 
(H2O) 




Ammonia 

(nhJ 



Ammonia 



/ t \ 

Energy from sun* 



ids etc 



imal 



/ I \ 

Energy set free 
as heat. 

The relations between green plants and animals. 

Green plants also give a very considerable amount of oxygen lo 
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 
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 




Nitric Bacteria 



The nitrogen 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.^ 

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 the one-celled animals, the paramcecia, are feeding; 
G, gullet; F.V., food vacuole; C.V., contractile vacuole; P, pleurococcu"* 
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 

Eggeriin 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 deterinifie: 

(a) How a one-celled animal is influenced by its environ- 
ment. 

(b) How a single cell performs its functions. 

(c) TJie 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 paramoeicium 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 sunHght. Such a sim- 
ple plant is the pleurococcus, the tiny green plants 
Pieurococcus. A seen on the shady sides of trees, stones, or city 
pb!nt ceiL ^ ^ houses. Thls 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 paramoecia 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 paramoecia shows thousands of tiny whitish bodies 
collected near the surface of the jar. In the paramoecium, as 
in the one-celled plants, the protoplasm composing the cell 
responds to certain agencies acting upon it, coming from ^vithout ; 
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 



c.V: 



co.v 



Tp.a.n 



m. 



yrturvrt !t7?7^-T'.>, 



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- 
i^ paramoecium. c.r,,contrac- side the cell body, the particles of food 

tile vacuole; f.v., food j. • i j.t_ j • j. txxi t- n 

vacuole; m, mouth; ma.n., materials are gathered mto little balls 
macronucieus; mi.n., mi- within the almost transparent proto- 

cronucleus; w.v., water i rm i* i* i j. i 

vacuole. plasm. 1 hese 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. 




fission. M, mouth ; 
MAC, macronucleus ; 
MIC, micronucleus. 
(After Sedgwick and 
Wilson.) 



structure, consisting of one large and one 
small portion, called, respectively, the ma- 
cronucleus and the micronucleus. 

Reproduction of Paramoecium. — Some- 
times a paramoecium 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. 

Amoeba.^ — In order to understand more 
fully the life of a simple bit of protoplasm, 
let us take up the study of the amceha, a 
tjqje 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 {F.) ex- 
tended ; EC, ectoplasm ; END, en- to gO, the rest ot the body tollow- 
doplasm; the dark area (A^.) is l^„ J^ the Central part of the 
the nucleus. (From a photograph ii . i mi • 
loaned by Professor G.N. Calkins.) Cell IS the nUCleUS. I hlS 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 amoeba 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 
return. Thus the cell 



m 

" 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 amoeba, like other one- 
celled organisms, reproduces 
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 amoeba, they each in 
turn divide. This is a kind of asexual reproduction. 

When conditions unfavorable for life come, the amoeba, 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 




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. 



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 paramoecium 
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, 
part of the cell has become 
elongated and is contractile. 
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. Thi« is known as physiological division of labor. 




Vorticella. e, gullet; n, nucleus; cv, con- 
tractile vacuole ; a, axis ; s, sheath ; fv, 
food vacuole. (From Herrick's General 
Zoology.) 



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 mjTiads 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.^ (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, LessoTis 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 chara^eters 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. 

In a simple plant like the pond scum, 

, • ni i. r 11 • ^ J A cell of pond scum. How 

a strmg or filament of cells is formed ^.^^^ -^ ^^^^^ ^^ ^^^^ ^ i^^g 
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 
fcough covering protects it from unfavorable changes in the sur- 

173 




174 



DIVISION OF LABOR 




Foundings. 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 \vill 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 fertilized 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 



perature, and sunlight, the 
seedlings that develop will 
each differ one from an- 
other in a slight degree.^ 
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- 




A colony of trilliums, a flowering plant. 
(Photograph by W. C. Barbour.) 



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 : — 



1. Spermatophytes. 



Angiosperms, true flowering plants. 
Gymnosperms, the pines and their allies. 

2. Ptendophytes. The fern plants and their allies. 

3. Bryophytes. The moss plants and their allies. 




Rockweed, a brown algse, showing its distribution on rocks below highwater mark. 

4. Thallophytes. The Thallophytes form two groups : the 
Algse and the Fungi ; the algse 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 algae. 

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 hlastula 
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. (J, the luoss body; 
S, the spore-bearing stalk 
(fruiting body). 



178 



DIVISION OF LABOR 



Physiological Division of Labor. — If we compare the amoeba 
and the parama?fium, 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 paramoecium has a definite gullet ; the amoeba 

may use any part of the 
body for locomotion; the 
paramoecium has definite 
parts of the cell, the cilia, 
fitted for this work. Since 
the structure of the para- 
moecium 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- 

Photo^^ruph of a living vorticella, showing the • ui fl j x, . pprtflin 

contractile stalk and the cilia around th ^ ^laDiy nno tnaL certam 

mouth. Compare this figure with that of the parts of a plant or animal 

paramoecium. Which cell shows greater , i. 4. j 

division of labor ? are Set apart to do cer- 

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; A'', 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, rnuscles; 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 






ri 



c.c. 



erid. 



TJli-S 



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 w^hich 
are f)ossible. The most 

Part of a sponge, showing how cells perform extreme division of labor 

division of labor, ect, ectoderm; 7nes, meso- . • j.u 

derm; emd, endoderm ; c.c, ciliated cells, IS Seen m the Orgamsm 

which take in food by means of their fla- which has the mOSt COm- 
gellae or large cilia {fla), , , . , » 

plex actions to periorm 
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 







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. 




The giasslike skeleton of h radiolarian, 
a protozoan. (From model at Ameri- 
can Museum of Natural History.) 



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 



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 Hve 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 '^ coelenterate" 
(coelom = body cavity, en- 
ter on = 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 smm- 
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 somet imes 

parasitic, examples being the 

tapeworm and liver fluke. 

They are usually small, ribbon- 

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. 

(c) Segmented worms are long, jointed creatures composed of 




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 
contracted. (From model at the Ameri- 
can Museum of Natural History.) 



184 



ANIMALS CLASSIFIED 



body rings or segments. Examples are the earth- 
worm, the sandworm (known to New York boya 
as the fishworm), and the leeches or bloodsuckers. 



A jointed worm. 
The sandworm. 
Slightly reduced. 



^^^^^^^^^^^^^^^^^^^^^V^v'^^^^^^^^^^^^^^^^^^^^^^^^^H 


^■1 


^^^^^^^^^^^f ( '^^^^^^^^^^^^^^1 


^^^H 


^^^^^^^^^^^^^^'< .' ; ^^^^^^^^^^^^^1 


^^H 


F^^Br vim 


,,J3H 




^^g^^^^m 


BI^B 


1 


^^^^E^^^^^^^^^^^H 


^1 



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 




The crayfish, a crustacean. A, antenna; AI, mouth; E, compound stalked eye; 
Ch, pincher claw; C.P., cephalothorax ; Ab, abdomen; C.F., caudal fin. A 
Uttle 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 havmg 
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 Inseda, 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 log 
The skeleton of a dog ; a typical vertebrate. bone will groW tO- 




186 



ANIMALS CLASSIFIED 



get her. 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 flexil)le 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 sUts 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 ElasmobrancJis. 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 throu<>;h life. Examples : iiiud puppy, newt, salamander. 

Ordkr II. Anura. Tailless Amphibia, which undergo a metamorphosis, breath- 
ing Ijy 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. 



P^^ 


(»i.'. -. '^'^>'^ v^^ 




■'^' '^' '' v^&"^/ii 




^^^^^^St^^^9r : 



The leopard frog, an amphibian. 



Classification of Reptiles 



Order I. Chelonia (turtles and tortoises), 
in bony case. No teeth or sternum 
turtle, box tortoise. 

Order II. Lacertilia (lizards). Body 
covered with scales, usually having 
two-paired appendages. Breathe 
by lungs. Examples : fence lizard, 
horned toad. 



Flattened reptiles with body inclosed 
(breastbone). Examples: snapping 





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 larvae 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 u\) in the release of energy, and a means of rapid excretion 
of the wastes resulting from the process of oxidation. Birds are 




Common torn 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. 



Examples : 




Classification of Birds 

Order I. Cursores. Running birds with no keeled breastbone. 

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. 
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 

backward, and adaptation for 

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 XL 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. Tliey also 
have a hairy covering and bear young developed to a form sirnilar to 
their own,^ and nurse them with milk secreted by glands known 
as the mammary glands ; hence the term '' mammal." 

^ With the exception of the mouotremes. 



African ostrich, one of the largest 
living birds. 



192 



EVOLUTION 




The bisoD, 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 are 
provided with hairy covering like other mammals. Such are the Aus- 
tralian spiny anteater and the duck mole. 

All other mammals bring forth their j^oung 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 




=Musnei>^anctrIt'T-t:e/t3i 



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. 1? 



194 



EVOLUTION 



Mammals 



"Birds 
13000 



Reptiles 
03500 

Amphibians 
/l400 



Fishes 
13000 



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 showSc 




Crustacea f 16 000 



Myrh 

4000\fooO. 

Annelids ' 

Echinoderms^^^^f^^\ J 

Flat ^ormsSOQLj^ 

Sponges 

' "^2500/ 



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 

Sponges 

Coelenterates 

Echinoderms 

Flatworms 

Roundworms 

Annelids 

Insects . . 

Myriapods . 



8,000 


Arachnids . 


2,500 


Crustaceans 


4,500 


MoUusks . 


4,000 


Fishes . . 


5,000 


Amphibians 


1,500 


Reptiles 


4,000 


Birds . . 


360,000 


Mammals . 


2,000 


Total . 



16,000 

16,000 

61,000 

13,000 

1,400 

3,500 

13,000 

3,500 

518,900 



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 the3^ 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 
Uttle 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. 
Sharpe, 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 

rroblems. — I, To deterinine the uses of animals. 
{a) Indirectly as food. 

(b) Directly as food. 

(c) As doinesticated, animals, 
id) For clothing. 

(e) Other direct economic uses. 

(/) Destj^uction of harmful plants and animals. 

II* To determine the harm done hy animals. 
ia) Animals destructive to those used for food. 

(b) Animals harmful to crops and gardens. 

(c) Animals harmful to fruit and forest trees. 

(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 



98 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 
5,000,000. Laws have been enacted in New York and other 
states against overfishing. Egg-carrjdng 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 











%. 


••^■^^ '- 


;^- 



The edible blue crab. (From a photograph 
loaned by the American Museum of 
Natural History.) 



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 
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. 

MoUusks 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 oj^sters. 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 
moUusks used for food are 
clams and scallops. Two 
species of the former are 
known to New Yorkers, 
one as the " round," an- 
other as the " long " or 
''soft-sheUed" clams. The 
former ( Venus mercenaria) 
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 




This diagram shows how cases of intestinal disease 
(typhoid and diarrhea) have been traced to 
oysters from a locality where they were " fat- 
tened " in water contaminated with sewage. 
(Loaned by American Museum of Natural 
History.) 




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 I^ake 
region, form important fish- 
eries. But by far the most 
important food fishes are 
those which ^re 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 



m*- 



^ 



"S2S 





Globe P'isheries. 



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-Avater 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, Feeding silkworms. The -caterpillars are 
1 , -1 1 . J 1 • 1 1 the white objects in the trays. 

leather, skms, and hides used 

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 each 
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 
liair 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 

tive. 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, S2500 
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 hving 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 hving 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 carefuUy, it is found to be 
a deposit of the mother-of-pearl layer of the shell around some central 
structure. It has been beUeved 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 ^ 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 pjTogaliic 
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 Uve 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 dietarv. 
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 bv 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 




The common toad, an insect cater. 



HUNTER, CIV. BI. 



14 




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.^ 

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 Hiourning dove, bobwhite, and 
of the above birds should be pro- other birds feed largely upon the 

tected by man and why ? i r r 

seeds oi many oi our common 
weeds. This fact alone is sufficient to make birds of vast eco- 
nomic importance. 



AMERICAN CROW 



ENGLISH SPARROW 



' 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 1874-1877, 
Professor Samuel Aughey saw a long-billed marsh wren carry thirty locusts to her 
young in an hour. At this rate, for sevei 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 



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 numl:)er 
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 SIO 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 Uttle 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. 
'' The common schools of the 
country cost in 1902 the sum 
of $235,000,000, and all higher 






This shows how sonu^ siuikos (constric- 
tors) kill and eat their prey. (Series 
photographed by C. W. Beebe and 
Claxence 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 3^early 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 larviB 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 
as the potato, and came 
north upon the introduc- 
tion of the potato into 




Cott(Mi-l)oll weevil, a, larva ; h, pupa ; c, adult. 
Enlarged about four times. (Photographed 
by Davison.) 



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 cotton 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, hving 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 

Davison.) 




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 larvse 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 
hirvae 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 breadstuff s. The carpet beetle 
is a recognized foe of the housekeeper, the larvse feeding upon all 
sorts of woolen material. The larvse 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.^ 

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 fertihzer. 

' 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 



^L 



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- 
larice. 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 




■I t 






The life history of th3 malarial parasite. This cut of the 
malarial parasite shows parts of th^ body of the mosquito 
and of man. To understand the liie history begin at the 
point where the mosquito injects the crescent-shaped 
bodies into the blood of man. Notice that 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 larvse 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 pupse 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 

















J 


^ 


m^ 


^^'^ 


-*«5L-««.. 


■ fi^ ■z:iiJ9aKmtm 


la 






i 
-J 


i 


^^« 




















1 


"■■"^^wL 


% 




1 


1^ 


j 


1 



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 carried] 

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 XTflVflTia For vpars Hfl- 
the American occupation of Havana. navana. i^ or years Jia- 

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 



YEAR 


250 

1 _ _ 


500 750 1000 1250 1500 


1871 




kUi^^HH 


\m^. iHHslU-^H 


.A7^ ^m^^^rLtma^mmtm 


1874 


I4Z5 




1-375 




■ [•^^■^■l 


1876 




1619 1 


1877 


1374 ^^^ 


1878 


1559 ^ 


1879 


1444 


1 


I860 


6 


1 ^ 


1881 


■CE& 


■1 


I88^ 


7 


p^x^^^mm^i 


1885 




■.{.L^HH 


ititi'^w^^mmm 


1885 


\l^ 




1886 


um 




1867 ■■•iit^H 


1666 


^IKTrf*! 


!■ 


1669 


Hc7*l(fll 




1890 


Kj^fl 




lAqi ^JiTM 


I89^ ^^91 


1895 


^HEiLii 


^M 


1694 


KESi 


1 


IHMK HHkk«.^ 


1896 


1282 ^^^Hl 


1897 


— 


iiL-4:B^HH | 


1898 m 


1899 m 


1900 


KUiB 




1901 


18 


Carrier of Yelloar Teuer discoimred 


\90l 


NONE 


1903 


NONE 


1 


1904 


NONE 


1905 


1 £4 Tirst Cuban R-ule. 


1906 


1 l£ 


1907 


3 


1908 


3 


1909 


NONE 


1910 


NONE 



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 amoeba-like animal in the 
digestive tract which comes usually 

through an impure water supply. s^^^T^;. *(lftrHowid.r"°" 
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 bacterial 
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 




Life history of house flies, showing from left to right the eggs, larvse, 
pupse, 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, 
a.nd 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, wuth 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 filtliy habits, 
but it is more recently that the 

Colonies of bacteria which have developed ^ gerioUS charge of spread of 
in a culture medium upon which a ♦^ . , 

fly was allowed to walk. diseases, caused by bacteria, has 




224 THE ECONOMIC IMPORTANCE OF ANIMALS 




II- ilUUIIIIIIIIIIIil1lll|i-U!" -It 

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 
6,000,000 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, 
covering of all food when not 
in use and especially the care- 
ful screening of windows and 
doors during the breeding 



cAses 


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MAR 


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hAX 


MHL 


JULY 


AUS 


S£PT 


PtT. 


NOV. 


OiC. 


leo 














^ 












90 














/^ 


^ 










80 














/ 


\ 










70 














' 


\ 










^ 












i 




\ 










SO 
















\ 










40 










1910 


1 






I 








30 










/ 
















20 










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J9II 












lO 








J 




^"v 


.1912 


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There were 329 t^T^hoid cases in Jackson- 
ville, Florida, in 1910, 158 in 1911, 87 
first 10 months of 1912. 80 to 85 



in 



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 larvae may be hid are ^^°^" ^'^^"^ ^'^^^ "^* 

•^ ^ 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 ^tcps all over the world. Starting from 
bubonic plague is carried China, it Spread to eastem Europe, thence 

diagTam'. ^''''^^''' *^' ^^ 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 w^orms, 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 220 

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 l)y 
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 
saciificed. 



230 THE ECONOMIC IMPORTANCE OF ANIMALS 

" The hookworm is not a bit spectacular : it doesn't get itseK 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 
Uving 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 fift}^ thousand persons 
killed in the last thirtj^- 
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. 

Q)) Frogs. 

(c) Other aniinals. 

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 Oi^g. 

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.^ 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 nQiicb 
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 mpst 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 




J^ 



H 



Diagram of the gills of a fish. (H), the 
heart which forces the blood into the 
tubes (F), which run out into the gill 
filaments. A gill bar (G) 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 organisms found by millions near the surface of 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 fonns 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 H 



A fish opened to show H, the heart ; G, the gills ; L, the liver ; S, the stoinach ; 
/, the intestine ; 0, 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 
chameter, 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 reheved 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 fives, 
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. CeUs of the central nervous system, in turn, send 
out messages which result in the movement of muscles. 

Skeleton. — In the vertebrates, of which the bonj^ 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 1 (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 
visually 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 spa^vns. The salmon begin 
to pass up the rivers in early spring, and reach the spav/ning 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 
mamier 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 




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 arc 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 memhrane, 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 

Inis diagram snows ^ 

how the frog uses becomes colder than that of the water. 

its tongue to catch 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. 




THE FROG 



243 



The Food Tube and its Glands. — Tho mouth loads liko a funnel 
into a short tube, tho gdllel. On the lower floor of the mouth can 
be seen the slitlike glottis leading to the lungs. The guUot widens 
almost at once into a long stomach, which in turn loads into a much 
coiled intestine. This widens abruptly at tho 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 internal organs of a frog: M, mouth; T, tongue; Lu. 
right auricle from all parts lungs; H, heart; St, stomach; I, small intes- 

f ,1 1 1 •, ,1 tine;, L, liver; G. gallbladder; P, pancreas; C, 

of the body ; it then con- ^^^^;^. ^ ^^.^^^^ ^^^^^^^ . g, ^pieen; K. kidney. 

tains considerable carbon Od, oviduct; O, ovary; Br, brain; Sc; spinal 

dioxide; the blood enter- cord; Ba, back bone. 

ing the left auricle comes 

from the lungs, hence it contains a considerable amount of oxygen. Blood 

leaves the heart through the ventricle, which thus pumps some blood 




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 deUcate 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 jelly like 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 








5 









if w Mr - ' .■'■^- 



**- ¥" 







Development of a frog. 1, two cell stage ; 2, four cell stage ; 3, 8 cells are formed, 
notice the upper cells are 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; C, 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, liitid legs 
beginning to form; 11, the hind legs show plainly; 12, i:j. 14, la^or stages in 
development; 15, the adult frog. Figures 1, 2, .S. 4. .'>, (\, 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 algae. 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 tli«^ left is ahfii's c^k, opened to show the embryo during the paSSage of 
at the center (tlie spot surrounded by a hghter ^^e real egg (which is 
area). At the right is an Ji.nghsh sparrow one . "^ ^ 

day after hatching. in the yoke or yellow 







W^M 


fi 


^^--^ 


v'^fl 


1 J 


BHK^-' m 


V '^^^i 


^5 




^^^^ "^^^^K^^^M 



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 lying 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 wall 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 rabbit, showing the ab- 
TYiflk rfrom flbniit thrpp sorbing organ; the branch-Uke processes 

mais {nom aoouL tnree ^^.^^^ ^,^^^^j^ ,^j^^^ ^^^^^^^ ^^^ mother 

weeks in a guinea pig to being shown at (v) -, ct, the tul>e connect- 

twenty-two months in an "^ f^t^^ll^^^lfu-' Hareke,'.;'''''" ""'"' 
elephant), the young ani- 
mal leaves the protecting body of the mother, or is ])orn. 
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- 
inals 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. 

ib) By hybridizing. 

(c) By other T)%ethods. 

To learn about some methods of improving the human race. 

{a) By eugenics. 

ib) By euthenics. 

Suggestions for Laboratory Work 

Laboratory exercise. — • On variation and heredity among members of a 
class in the schoob^oom. 

Laboratory exercise. — On construction of curve of variation in measure- 
ments from given plants or animals. 

Laboratory demonstration. — Stained Qgg eel's (ascaris) to show chromo- 
somes. 

Laboratory demonstrations. — To illustrate the part played in plant or 
animal breeding by 

(a) selection. 

(6) hybridizing. 

(c) budding and grafting. 

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. Heredity 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 



ifl 




Variations in the Cataipa caterpillar. (Photographed, natural ^ize, 

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, is 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 grandmotlier. 
Indeed, as far back as we are able to go, ancestors have added 
something. 



252 



HEREDITY AND VARIATION 




sp.n. 
- cent. 



--•/ — e.n 



COMPARISON 

OF 

SEXUAL AND ASEXUAL 
CELL "REPROLUCTION 








HEREDITY AND VARIATION 



253 



Charles Darwin and Natural Selection. — The grciit English- 
man Charles Darwin was one of the first scicuitists to realize how 
this great force of heredity applied to the development or (evolu- 
tion of plants and animals. He knew that although animals 
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 origiiuil 

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 
test 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. LiitluT Burbaiik, 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 countrj^ 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 flo\v(>r 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 



eml)('(l(locl 1)11(1 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- 



VI 



f 



I 



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 producc at will, trees bearing choice 

two branches to be formed ; 
b, a tongue cut in each ; c, fit- 
ted together ; d, method of 

wrappmg. plant propagation are by means of run- 

ners, as when strawberry plants strike root from long stems that 
run along the gJOund ; 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 

^ 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 169-17&. 



varieties of fruit. ^ 

Other Methods. — Other methods 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 

PUNTER, CIV. BI. 17 



258 



HEREDITY AND VARIATION 



9jQ 



A: 






/. 






Q 



\ 






OO 



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 dominanty 
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 recess've 
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 
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 




Illustration of Mendel's Law. 



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 
^, , , . r X, X . animals about the size of 

The four-toed ancestor of the present horse, t t 

restored from a study of its fossil skeleton, a foX. The earliest horse 

(After Knight in American Museum of Nat- ^^ have knowledge of had 

ural History.) r ^ ^^ r i 

tour toes on the tore 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 2G1 

improved the various types of horses famihar 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 sinc(; 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, that dread white 
plague which is still responsible for almost one seventh of all 
deaths, 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 ditferent 
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 Icnown as 



202 



HEREDITY AND VARIATION 



" Margaret, the mother of criminals." In seventy-five years the 
progenj^ of the original generation has cost the state of New York 
over a million and a quarter of dollars, besides giving over 



A* 

X 





K 



©H®ET®~iT© 



N 



®® 



N 



li 



hhSW^ 



N 

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. 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 Daven- 
port.) 

to the care of prisons and asylums considerably over a hun- 
dred feeble-minded, alcoholic, immoral, or criminal persons. 
Another case recently studied is the " Kallikak " family.^ This 
family has been traced to the union of Martin Kallikak, a young 
soldier of the War of the Revolution, with a feeble-minded girl. 




I^^^^T<^ 



N 



d. C. d. 




m 

d. d. d. I 
l-nj.ln/.lnj.l 



This chart shows that feeble-mindedness is a characteristic 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. 
The 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 countr^^ 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 pul)lic 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 



N 



264 HEREDITY AND VARIATION 

D wight, president of Yale ; Sereno Edwards D wight, president of 
Hamilton College ; Theodore Dwight Woolsey, for twenty-five 
years president of Yale College ; Sarah, wife of Tapping Reeve, 

\Sh0 BtO 

This record shows the inheritance of artistic ability (black circles and 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 AVilliam 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. Macmilian and Company. 
Harwood, New Creations in Plant Life, The MacmUIan 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 RelatioJi to Eugenics. Henry Holt and Company. 
De Vries, Plant Breeding. Open Court Publishing Company. 
Goddard, The Kallikak Family. The Macmilian Company. 
Kellicott, The Social Direction of Human Evolution. Appleton Company. 
Punnet, Mendelism. The Macmilian Company. 

Richards, Helen M. Euthenics, the Science of Controllable Environment. 
Walter, Genetics. The Macmilian 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 ot 
cells. 

Laboratory demonstration by means of (a) human skeleton and (6) 
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 paramoecium 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 paramoecium. It is the cells of the body working together 

266 



THE HUMAN MACHINE 



2r,7 



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 macliine 
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 The human body seen from 

products of oxidation must be carried the side in iongitudin:U 

section. 

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. 




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. 
~p/ Bones also protect the nervous 
system and other delicate organs. 
Thej^ 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 




cramum ; 
sternum ; 
vertebral 



Skeleton of a man. CR 
CL., clavicle ; ST., 
H., humerus; V.C., 
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. 
Prawing, 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 
tend to straighten the body, 
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 




Diagram showing action of biceps muscle. 
a, contracted; 6, extended; h, humerus; 
s, scapula. 




w 



F 



4 





A B C 

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 lengtlien the spinid 
column. 

It is the duty of every girl and boy to have good posture and 



270 



THE HUMAN MACHINE 




Bad posture iu 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 cells, 
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, 
e^ch 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 Sedgwicic, 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. 



y 



XIX. FOODS AND DIETARIES 

Prohle^ns, — A study of foods to determine: — 

(a) Their nutritive value. 

(b) The relation of worh, environment, age, sex, and digef<- 
tihility of foods to diet. ■ ' 

(c) Their relative cheapness. 

id) The daily Calorie requirement. 

ie) Food adulteration. 

(/) TJie 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, {g) 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 Qgg. 

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 he 
defined as something that releases energy or that forms material for 

272 




water 



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 ^f^r^sr^Asuaar 
matter and water. B^^^Kprotoid 

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- ThcTcomiiosition of 
tains by eating the flesh of animals, and some niiik. why is it 

11.. ]• xi r 1 J. /r 1 considered a good 

he obtams directly irom plants (tor example, food? 

peas and beans). Proteins are the only foods 

directly 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 



r cr)m 
%. meaJ 
\ 2lbs. 





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 
Ycents^ v^^^ '\r 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 j^gj^^ 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 : ^ — 

^ 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 Ume, 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 



DIGESTIBLE NUTRIENTS 



INDIGESTIBLE 
NUTRIENTS 



HON NUTRIENTS 



PROTEIN 

MUSCLE 
MAKING 



FATS 



CARBO- MINERAL 
HYDRATE^ MATTERS 



WATER REFUSE 



^ FUEL VALUE 
CALORIES 



FUEL INGREDIENTS 



NUTRIENTS, ETC., 
PER CENT. 



FUEL VALUE OP 

1 LB. ("-ALriRIEs) 



Milk, 
unskimmed 

Butter 



■White bread 



Oat meal 



Corn meal 



Rice 



10 

— 1 — 



20 



30 



40 



50 



60 



70 



80 

— r- 



90 



100 



400 



800 



1,200 2.000 2.200 2,400 2,800 3,200 3,600 4.000 




m 





Tabic of food values. Determine the percentage of water in codfish, loin of beef, 
mUk, 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 ^ 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 carbohvdrates, i.e. 4 Calories 
to a gram.^ 

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 w^ho 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 



O^ict of CwcrimtAi Stittoni 
A.C. True- Difcctor 



9ttp«rta oj 

C. f.WAHGWORTHY 

tapert in Cha<«c 0' Nutr>t>or> Inveshjitictns 



COMPOSITION OF FOOD MATERIALS. 



■■ I I I I r~ 1 fts?! 



SHELLED BEAN, FRESH 

'jter 58.9 
fit.0.6 



Pruu;n9.4 




lOOO Catoi 



NAVY BEAN, DRY 

Waierl?6 

bohydrite&.29.l 

. t.ojj Carbohydrates 59.6 




STRING BEAN, GREEN. 

^Csrbohydrates: 7.'t >"«? Aih'.O.B 

Water.89.? 




Wsier75.4 



l90c*i.oii(» PtnPouiiD 
CORN, GREEN. 

tOlBLt PORTION 

P^olelr^ 3 I - 




Carbohyorales: 19.7 
(JM -Ash;0.7 



Fat-.l.l 



U.S.Oep^rmcAi of Agriculture 

Officf o1 Ei^Mhnicnt Sulior\$ 

AC. True, director 



Prepared bj 
C. f. imiswoaTHY 
Eipert In Chir9e of Nulriljon Intestigitiot^s 



COMPOSITION OF FOOD MATERIALS. 



r^t Cjrbohyd'4U3 



Fuel Vatut 

b Sq.ln.EQutJf 

000 Calortvt 




P<atnr> r^t Cjfbohyd<*l« A»h Water 

WHITE BREAD WHOLE WHEAT BREAD 

_Waier:35.3 Water 

^Protein: 9 2 Protein 

Carbo- Carfao 

hydrates: 63. r hydrate 



fl«i ViiuE: 



OAT 
BREAKFAST FOOD 




Fufl WLUE: 



lieOaLomj Water-84.5 
Protein;2.8 

TOASTED BREAD 

Ash-.O 





I t t CALOftltS 
>C>I POUiO 

.Fat:0.5 

Carbohydrates' 11.5 

CORN BREAD 



FufL 



280cALORr£S 

PER POUND 



Water: ?4.0 Waler:38.9 
Proteiri: 11.5 Protein: 7 9 




_arbo- Carbo- — ' \----:y---''.':'-l Ash: 

(hydrate3:6l.2 hydrate5:*63 \sizzZ^z^z&^ i 2 

Fut^rjLut: MACARONI Futi_«u,E, 

^^^H COOKED 

1^1 Fat. 1.6^ Proteln:3.0 
t380c4LO»'ES 

PfBPOWO ^ ■ 

Ash: 1.3;^ '" 
.•^ F, 



-Water-78.4 



1 1 75cj»L0B(ia 

PfR POUIO 



Carbo' 
hydrates: 15.8 



VALUE 



c 



400uu)Bies 
peopouHt} 



U. J. tk^A'tmeol o' AfliScwHwie Prepared br 

OH.ce ot (*p**imefil StJl'Ofti C. F. LJltGWORTHY 

K C. True: C^'eetc Cipct in Charqe ol Mutritior^ Investiqatiom 

COMPOSITION OF FOOD MATERIALS 

^^ rniTmiii rm ^^ ^a 

Prott-n Fat Carbohydrate AiK Water 



^tSq In Equals 
1000 Calone: 




ONION 




Carbohydrates:9 9- 
-Water 83 Fuji „ius, 



Prole!n:1.6 
F8t.0.5 
arboKydrates;l3.5 



«!.hl4 



PARSNIP 




Water945 



Carbohydrates: I3 4 ^Waier:78 3 

FueiMLUf: Protein: 1.1 

I J Carbohydrates: 3.4 

37j caLoails Pfer>ouaO A^:|.0 




li. S. Department ot Agriculture 
Oftite ot f xpetiment Stations 
A. C. True; Director 



Prepared by 

C. F.UUIGWOSIMY 

I spert in Cturge ot Notrrtion InvestlgatioBS 



COMPOSITION OF FOOD MATERIALS. 



F'at Carbohydrate) Ash 



JCarboh^drates lOO-O 




■ Cual Value 
'^fcSq lr>.Equdlj 
1000 Calpnas 

MOLASSES 



Prote;n:2.4 



Water:2J.I 



Carbohydrates 693 



STICK CANDY 




1810 CAtooits ^ Carbohydrates: % 5 



FufL vAiuC: 



I300CAL0HIES 

PfRPOUIP 



Watet:3.0 



MAPLE SUGAR 



FOEL VaiuE: 



1745 aLoitiES 

PEH POUND 



Ash: 0.5 



HONEY 



Ash:0.9^ 



-Water:|6.3 Water:l8.2- 
Protein:0. 



Carbo- ■ Carbo.- 

hydrates:82.8 hydrates.! 




1500 



(JLORICSPCOPOUIID 



F uel v*lu E: 
1475 c«io«iESPfPPoun& 



Ash- 0.2 



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 



U.S. OtpittmenX of AgricuHure 

Office ol Etpntfneni Sution» 

A.C. true 0>rectoi 



Prepartd b7 

C.r. lAH&WOHTHY 
I ipe't in Chifgt of Nutntron imesbqiiioos 



COMPOSITION OF FOOD MATERIALS. 



ES3 




' (000 Ciiorm 



SALT COD 



H|Water:5J5, 



OYSTER 

Water86 9 



400 CAIOBIIS 
*f« POUPiO _ 

fatO J — 




\[^\/ Ash. 12 

bohydfa(es*3. ^ 



SMOKED HERRING 



MACKEREL 

Fat F'ih 




.Wat<rr 3* 6 

Protetn:36.4 

FuK viiuf: 



1305 CALOHiEi 



Ash: 1 3.2' 




230 WLOOiti 



6?0 (jilorics 



U. S. OtM^THm of Afficuriwa 
Office of fiH^Woint $riii«ns 



CF.UifGwOfiTNT 

(lpert>nCHV9< 0> HutnMn ln«cst>^4 



COMPOSITION OF FOOD MATERIALS. 

CTiin rrn r*^ rri ^ fv..-.!- 



t>arf»'n 



^^" iOOOC«io«« 

LAMB CHOP PORK CHOP 



tO'»lf (>0«''0^ 



fjtJO-l 




'^ '5 ciiioBiej 
PfaDOuaD 



BEEF STEAK 

CUBIC Oo«T>CN 

Wdter:6 



furi 

V*IU£ 



Ash. 4 a 

1875 wtoffics 

DRIED BEET 

Water 54 ? y.r>w^^prot».A: 




F«t:t8.5 



8iO uc<*o 
Ptaeogae 



CF.LANGWOBTHY 



U.S-0«P"'1'"Cnt of Agriculture 

Oflit* of I «p«fimeftt S'lt'ons 

A.C ^rue: Direttor 

COMPOSITION OF FOOD MATERIALS 

Protein Fdt Cirb«hjd'«te» Ash W*ler ^^| *qqq c«ioriei 

WHOLE EGG EGG 

WHITE UDTOIK 




Protein 

'♦•8 
fat:lO 

Ash: I 

FuFL V«LUf Of 

WHOLE 166'. 




Fof I vAiut ot vouc 



695 ulorics 

Pt»P0UI*O 



CREAM CHEESE 
Water 34 2 



I bio c«io«it5 

PIR POUND 



Futl VALUE OF wmiTE: 

c 

?45 CALOPlfS 
PER POUND 



COTTAGE CHEESE 



Protein: 20 9 




1665 OLORICSPERPOUIIO 



495 oioditspeRPOuiio 



U.S. Oep»lm«m ;>( Agr'KuihM PrepMrd ») 

Off'Ct of Eiotfimenl Sulioii C.f . iWCwOBTMt 

A.C. Irut' Diftctoi (t^rl in D^arge ol Mulr>t«n in*t3liCJt>eas 

COMPOSITION OF FOOD MATERIALS. 

^^ fmiiii r-n E';;^m E3 ^. f-i *•'- 

P'ote-r. ft\ C«rtohydr«tw Ash Vat«i 



lOOO C«ion« 



VEGETABLE OILS, AS 
OLIVE , 
PEANUT, 
COTTONSEED 



FatlOOO 




BACON 
Protein;9 4^ ^Fat:6'« 



Water I&8 





Fat 81,8 



4080 C'L08>E5 PER POVID 



BUTTER 

1 ^"'° ^ ■ Vx ^Wa.enl3.0 



J090 uumri »• Pow« 
Water II? 
P.oleiO:4 7 



-A»h;0.3 



34?5 c-*Lo«iis pm poupo 



LARD 




Ptolein; 1.0 




3405c«jnnj PER 



♦060 oiiiiKJ "-1" ■^I'C 



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 



4 C. True: DifCCUr 



Prepvedby 

C. F. muGWORTHY 

U^n In Cunie ol Nutrition Invuti^rton) 



COMPOSITION OF FOOD MATERIALS. 









1000 Ca(on«i 



WHOLE MILK 



SKtMMILK 




-Water:870 



Protein: 3.3 



Carbohydrjtes:5.0 




Vater-90.S 



Protein: 3.4 



^Ufl ■<UU(; 3l5cUOIIISP(BP0UIID 



BUTTERMILK 



CarbohydrJtes:5.l 

c 

Fltl »illUt: l65c<L0«ltSPfI'»0U»B 



CREAM 




^Water 91.0 



Carbohydrates:4.8 

D 

Fuel vuuE; l60ciL0Bies re»PouiB 



Protein: 3.0 Fat: 18.5- 
Ash:05' 



^Water:74.0 
Protein:2.5 



Carbo^^vdrates:4 5 



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 gro^\i:h 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 




fufL VillK: 880 OILOBlFS "tO PflUPlO 



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 ])ro])or- 
tion of the daily dietary should be meat. Many ])c()])le 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 DTETARTER 



29,:^ 



PROTEIN 



FATS CARBOHYDRATES FUEL VALUE 



FOOD 

MATERIALS 



Beef, round 



Beef, sirloin 



Beef, shoulder 



Mutton, leg 



Pork, loin 



Pork, salt, fat 



Ham, smoked 



Codfish, fresh, 
dressed 



Oysters 35 cents 
per quart 



Milk, 6 cents 
per quart 



Butter 



Cheese 



Eggs, 24 cents 
per dozen 



Corn meal 



Oat meal 



Beans, white, dried 



Rice 



Potatoes, 60 cents 
per bushel 



Sugar 



Ho 

QjD. 

a. 



14 



20 



12 



16 



12 



12 



18 



10 



18 



25 



16 



16 



5 « 



POUNDS 



.71 



.50 



.83 



.63 



.83 



.83 



.56 



1.00 



.56 



3.33 



.40 



.63 



.63 



2.50 



2.00 



1.25 



10.00 



1.67 



POUNDS OF NUTRIENTS AND CALORIES OP FUEL VALUE 
IN 10 CENTS WORTH 



1 LB. 

J 



2 LBS. 



3 LBS. 

_i 



2,000 CAL. 



4.000 CAL. 



6.000 CAL. 




m^ 



y//////////.m'A 



I 



Table showing the cost of various foods. Using this table, make up an ccunuinical 
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 
])roteins, 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 Calor 

2. For child from 2-5 years 1200 Calor 

3. For child from 6-9 years 1500 Calor 

4. For child from 10-12 years 1800 Calor 

5. For child from 12-14 (woman, light work, also) . . 2100 Calor 

6. For boy (12-14), girl (15-16), man, sedentary . . . 2400 Calor 

7. For boy (15-16) (man, light muscular work) . . . 2700 Calor 

8. For man, moderately active muscular work .... 3000 Calor 

9. For farmer (busy season) 3200 to 4000 Calor 

10. For ditchers, excavators, etc 4000 to 5000 Calor 

11. For lumbermen, etc 5000 and more Calor 



es 
es 
es 
es 
es 
es 
es 
es 
es 
es 
es 



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 ot the average normal grown person when asleep 
and awake, at Wv^rk or at rest : — 

Average Normal Output of Heat from the Body 



Conditions of Muscular Activity 



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 . . . . 
Man at very severe muscular exercise . . 



Average 


Calories 


PER Hour 


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 

works at desk 9 hours 

reads, writes, or studies 4 hours . 
walks or does light exercise 2 hours 



X 65 Calories = 


585 


X 100 Calories = 


900 


X 100 Calories = 


400 


X 170 Calories = 


340 



2225 



This comes out, as we see, very close to example 6 of the table ^ 
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 



_ ._- . ^_^__-^^— ^—^^^ 


Port, containing 




Cal. 


Furnished 


Price 




►jr 




a 




. 


Food 


100 Calories 


Wt. in 
100 Cai 
Port. 


49 


% 
f^ 


1 ^ 


n 

I-H 


ij 
o . 

§1 


Oysters . . . 


1 doz. 


6.8 


22 


29 


.175 


.07 


Bean soup . . 


1 small serving 


2.6 


24 


12 


64 




.007 


Cream of corn . 


f ordin. serv. 


3.1 


11 


58 


31 




.02 


Vegetable soup . 


§ ordin. serv. 


2.4 


8 


89 


3 




.01 


Cod fish (fresh) 


ordin. serv. 


5 


95 


5 





.12 


.04 


Salmon (canned) 


small serv. 


1.75 


45 


55 





.22 


.03 


Chicken . . . 


^ large serv. 


1.75 


39 


56 


5 


.22 


.05 


Veal cutlet . . 


f large serv. 


2.4 


54 


46 





.28 


.045 


Beef, corned . . 


1 large serv. 


1.0 


15 


85 





.16 


.01 


Beef, sirloin . . 


small serv. 


1.6 


33 


67 





.34 


.04 


Beef, round . . 


small serv. 


1.8 


39 


61 





.24 


.025 


Ham, lean . . 


ordin. serv. 


1.1 


28 


72 





.22 


.015 


Lamb chops . . 


1 ordin. serv. 


1.0 


24 


76 





.20 


.013 


Mutton, leg . . 


ordin. serv. 


1.2 


35 


65 





.20 


.015 


Eggs, boiled . . 


1 large egg 


2.1 


32 


68 





.30 doz. 


.025 


Eggs, scrambled . 


1| ordin. serv. 


2.5 


37 


58 


5 


.30 doz 


.03 


Beans, baked . . 


side dish 


2.66 


21 


18 


61 


.08 


.013 


Potatoes, mashed 


ordin. serv. 


3.2 


10 


25 


65 


.02 


.005 


Macaroni . . 


^ large serv. 


.95 


15 


3 


82 


.10 


.01 


Potato salad . . 


ordin. serv. 


2.25 


10 


57 


33 


.20 


.025 


Tomatoes, sliced 


4 large serv. 


15. 


15 


16 


69 


.10 


.10 


Rolls, plain . . 


1 large roll 


1.2 


12 


7 


81 


.10 doz. 


.01 


Butter . . . 


ordin. pat 


.44 


5 


99.5 




.35 


.01 


Wheat bread 


1 small slice 


.96 


15 


5 


80 


.07 


.005 


Chocolate cake . 


1 ord. sq. piece 


.98 


7 


22 


71 


.32 


.02 


Gingerbread 


^ ord. sq. piece 


.96 


6 


23 


71 


.16 


.01 


Custard pudding 


ordin. serv. 


3.25 


18 


42 


40 


.15 


.03 


Rice pudding . . 


very small serv. 


2.65 


8 


13 


79 


.13 


.02 


Apple pie . . 


I piece 


1.3 


5 


32 


63 




.013 


Cheese, American 


1| cu. in. 


.77 


25 


73 


2 


.19 


.01 


Crackers (soda) . 


2 crackers 


.9 


10 


20 


70 


.10 


.007 


Currant jelly . . 


2 heap, spoons 


1.1 


2 





98 


.40 


.025 


Sugar .... 


3 teaspoons 


.86 








100 


.06 


.003 


Milk as bought . 


small glass 


4.9 


19 


52 


29 


.05 


.015 


Milk, cond., sweet 


4 teaspoons 


1.06 


10 


23 


67 




.01 


Oranges . . . 


1 large one 


9.4 


6 


3 


91 




.025 


Peanuts . . . 


13 double ones 


.62 


20 


63 


17 




.004 


Almonds, shelled 


8-15 


.53 


13 


77 


10 




.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 be 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 candj^' 
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 lie 
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 l^oth 
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 im{:)ortance 
among physiologists. A few years ago Dr. Atwater performed a 
series of very careful experiments by means of the resi3iration 
calorimeter, to ascertain whether alcohol is of use to the body as 
food.i 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 verj' 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. 
HX7NTER, CIV. BI. 19 



290 FOODS AND DIETARIES 

a bottle of light wine.^ 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 follo\ving 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, ox 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 tAqihoid 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 DEATHS 



Sceptre 

Life Insurance 

Cornparo) 
1884^1909. 



MODERATE DRINKERS 



ABSTAINERS 



79.7 
I 



United Kvn^doYYi 
Temperance ^'^^ 

General Provldertt 

Irtstitution 
1866-1909. 



MODERATE DRINKERS 



ABSTAINERS 



|93| 

J' 
7D, 



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 tromi)ling 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 pow(.'r, 
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 sufficitMit 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 




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 % ; /, g, h, much-advertised nerve tonics, 
20 %, 21 %, 25 % ; i, another much-advertised sarsaparilla, 27 %; 
y, 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 Minneapohs 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 acetanilid. 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 and 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. 

Olsen, 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 InstitutioJis. 
Reprint from Yearbook, 1902, Milner, Cost of Food related to its Nutritive Vaho 
Experiment Station, Circular 46, Langworthy, Functions and Uses of Food. 



XX. DIGESTION AND ABSORPTION 

Problems, — To determine where digestion takes place hy ex- 
amining : — 
ia) The functions of glands. 

(b) The ivorh done in the mouth. 

(c) The worJc done in the stomach. 

id) The ivorh done in the small intestine. 

ie) 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 shoA\dng 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, 

296 



DIGESTION AND ABSORPTION 



297 



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- q « 

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 mesenkry 
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 projicr, wo 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; L, liver; G, gall bladder; P, pancreas; 
Sp, spleen ; SI, small intestine ; LI, large in- 
testine ; V, appendix; .-1, 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. The}^ 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 prol)ably 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 ^ 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 ofif the secretions formed in 
the cells lining the cavity c ; o, 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 alkahne surrounding in the 
mouth to that of an acid in the stomach. Enzj^mes seem to be 
able to work indefinitely, providing the surroundings are favorable. 
A small amount of digestive fluid, if it liad Icjng 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 muams 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 
alwaj^s 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 wliich emj^ty 
into the mouth, and which are called, according to their position, 
the parotid (beside the ear), the suhmaxillary (under the iawbone), 
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 sahva 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. 
_ . , . . . This ferment acts only in an alka- 

Expenment showing non-osmosis ot 

starch in tube A, and osmosis of line medium, at about the tempera- 
sugar in tube B. |yj.g Qf ^ijg ]30(jy^ 




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 ear. 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. 
The mucus secreted from 
gland cells in this lining 
makes a slippery surface so 




The mouth cavity of man. e, Eustachian 
tube ; hp, hard palate ; sp, soft palate ; 
ut, upper teeth ; be, buccal cavity ; It, lower 
teeth ; t, 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 tlu; 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 papillce. 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 
of man are divided, ac- 
cording to their func- 
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 sharj) i)uiuts and are 
called the canines. Then come two teeth on each side, eight in 




I. Teeth of the upper jaw, from below 



in- 



cisors; 3, canine; 4,5, premolars; 0, 7, 8, molars. 
II. longitudinal section of a tooth. E, enamel ; 
D, dentine ; C, cement ; P, pulp cavity. 



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 " hurr}^ 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 

b}^ the presence of food in the tube, push the food down to the 
stomach by a series of contractions until it reaches the stom.'ich. 
These wavelike movements (called peristaltic movements) are 
characteristic of other parts of the food tube, food bein^ ])uslied 
along in the stomach and 
the small intestine by a 
series of slow-moving mus- 
cular waves. Peristaltic 
movement is caused by bolus ojjood 

muscles which are not Peristaltic waves on the gullet of maa. 

(A bolus means little ball.) 

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 l)e 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 fomid 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 ^j-^^t organ. Here, as elsewhere in the digestive 
magrTified.^ a! central t^act, the muscles are involuntary, muscular action 
or chief cell, which being under the control of the so-called sympathetic 

makes pepsm ; B, bor- ^i^j-pQus system. Food material in the stomach 

der cells, which make , , i j • •, i • ii 

acid. (From Miller's makes several complete cn-cuits durmg 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 ringhke 

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 



30rj 



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 whicli was churned into a 
soft mass was only permitted to leave the stomach when it })ecame 
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 opc^iing 
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. 




% J. 

ooc*" 






'i*^ 

' '<.*.. 



A 



Appearance of milk under the mitToscope, showing th<> 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. Gl.) 

HUNTER, CIV. BI. — 20 



306 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 whicli can pass through the wails 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 lands 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 
alkahne 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 sligh{ 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 Hver 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 ^^^^^^^ greatly magnifiod. a, mouths of 

intestinal glands; o, villus cut lengthwise 
IS supplied by blood from to show blood vessels and lacteal (in center) ; 

two sources. The greater ': ^.^f^^! sending branches to other villi; 

® , I, intestinal glands; tn, artery; v, vein; 

amount of blood received l, t, muscular coats of intestine wall. 

by the liver comes directly 

from the walls of the stomach and intestine to this organ. It 
normafly 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.^ Glycogen is stored 
in the liver until such a time as a food is needed that can be quickly 




1 It is known that glycogen may be formed in the body from protein, and possibly 
from fatty foods. 



308 DIGESTXON 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 Uttle 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 



iH^m to 
arm 



vessels, while inside of these, occupying the core of the vilhis, are 
found spaces which, because of their white appearance after 
absorption of fats, have been called ladeals. (See figure*, i)age 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 tlie 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 




Diagram to show how the 
nutrients reach the blood. 



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 whicli make and give olT 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 v^e 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 ay 
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 


is Lb. Meat with Water 


is Lb. Meat with Dilute 
Alcohol 


XVII 


a 9 : 15 A.M. 


Digested in 3 hours 




XVII 


/3 3 : 00 P.M. 




Digested in 3:15 hours 


XVIII 


a 8 :30 a.m. 


Digested in 2 : 30 hours 




XVIII 


^ 2 : 10 P.M. 




Digested in 3 : 00 hours 


XIX 


« 9 : 00 A.M. 


Digested in 2 : 30 hours 




XIX 


/3 2 : 30 P.M. 




Digested in 3 : 00 hours 


XX 


a 9 : 15 A.M. 




Digested in 2 : -45 hours 


XX 


/3 2 : 30 P.M. 


Digested in 2 : 15 hours 




VI 


a. 9; 15 A.M. 




Digested in 3 : 45 hours 


VI 


/3 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. : — 



Deaths by: 


10 20 30 40 50 60 70 80 90 
1 1 i 1 1 1 1 ' ■ ' 


Accidents. tea 4587 1 


Hul. luoerculosis 


EH*! 29.832 


Heart Disease 


RW*! 13225 1 


A"po-plex^ 


2585 


9163 1 


ParaVs Wk^ 1817 1 


"HneuTTLonia 


3090 


10.954 1 


Arterial Disease ^^^SKM 2158 1 


Suiacle 


1388 


1 4647 1 


Brigkts DisPasfi. 


^RMMM \ZZ5S 1 


Cirrlaosisof Liver. 


Z7GZ UtMESMMl 


AlcoWolisra. 


zozs J 


TOTAL 


26507 


96,063 1 



Proportion of deaths from disease in a certain area due to alcohol. The black 

area shows deaths due to alcohol. ^ 



" AlcohoUc 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. 

^ 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. 



XXL THE BLOOD AND ITS CIRCULATION 

rrohlems, — To discover the coinpositioii ami uses of the (Uf- 
f event 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 absor])ed 
through the walls of the food tube and become part of the blood. ^ 

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 pum])(Ml to the body 
cells where, as work is performed, oxidation takes i)lace 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 tht' nutrii'iit.s in va- 
rious foods. But we also find that peptones are changed back again to proteins wlu-n 
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 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 that about five 
million are found in a cubic millimete:* of normal blood. They 
make up almost one half the total volume of the blood. The 
color, which is found to be a dirty yellow when separate cor- 
puscles are viewed under the microscope, is due to a protein 
material called hoemoglohin. Haemoglobin contains a large amount 
of iron. It has the power of uniting Yerj 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 lungs. 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 
clot 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 i)an and briskly 
whipped with a bundle of httle 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 witliin 
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 A^Sl 
eventually cause this en- <3^ 
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 



.x'Tr)o 




A small artery (A) breaking up into capillaries 
(c) which unit3 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 ])elieved that the colorless 
corpuscles ot the blood have somewhat the same function. This 

he later proved to be true. Like the 
amoeba, 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 

A colorless corpuscle catching i ,1 • • xi, rni, 

and eating germs. phagocytes by poisonmg 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 



© o 
o 



oa 






J 




Course y Pla^ijifi 



^^W}0i^y>J^^P^' 



Dissolved I 
NiitrJejit 




■=- lyymah Space ^^ 






^zJ^' -- Leucocyte 




LYMPH 



T^uiij- 



1 



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 SLoS)^ 
cells, which are bathed by YmE^ 
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 hlood 
plasma plus some colorless 
corpuscles. It acts as the 
medium of exchange between 
the hlood proper and the cells 
in the tissues of the body. 
By means of the food sup- 



ply thus brought, the cells ^^^^ 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 oxygon passed 

over by the lymph, oxidation may take place within the cells. 

Lymph not only gives food to the cells of the body, ])ut also takes 

away carbon dioxide and otherwaste 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 tliese 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 



319 




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 thc^ 
heart is on the left side of the ])ody. The hcnirt is surrounded 
by a loose membranous bag called tlu^ 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 midlipe, 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 
muscular walls, the ventricle. Com- 
munication between auricles and 
ventricles is guarded by little flaps 
or valves. The auricles receive blood 
from the veins. The ventricles pump 
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 l^lood 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. Tlicn. 
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 



the heart cut away : a, aorta ; 
I, arteries to the lungs; la, left 
auricle ; Iv, left ventricle ; tti, tri- 
cuspid valve open ; n, bicuspid 
or mitral valve closed ; p and r, 
veins from the lungs; ra, right 
auricle ; rv, right ventricle ; 
V, vena cava. Arrows show di- 
rection of circulation. 



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 ; C, capillaries oi the body. Notice the two- 

chambered heart. 

II. The circulation in a frog. L, the lungs ; C, the capillaries. Notice the hearf, 
has three chambers. What is the condition of blood leaving the ventricle to 
go to the cells of the body ? 

III. The circulation in man. //, head ; ^.arrns; L, lungs; *S, stomach ; Lz, 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 ; d, dorsal aorta ; 6, 
vein to lungs. 



THE BLOOD AND ITS CIRCULATION 321 




'^wW 



HUNTER, CIV. BI. 21 



322 



THE BLOOD AND ITS CIRCULATION 



the right auricle through two large vessels known as the vence 
cavcB. 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.^ 

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 Uver, 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- 




■d 



Capillary circulation in the web of a frog's foot, as seen under the compound micro- 
scope, a, b, 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. 



i 



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 'puhe, 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 im]ior- 
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 piiss 
to the tissues, and carbon dioxide is given up to the plasma. Tliey 
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 j^our 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 breathine) are the chief factors 

V 1 ■ 

veirf "no- which cause a steady flow of blood through the veins in 
tice the thin the body. 

vein. Lymph Vessels. — The lymph is collected from 

the various tissues of the body by means of a number 
of very thin-walled tubes, which are 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 



32.^ 



directly into the blood throup;h the walls of the villi and carried to 

the liver. Fat, however, is passed into the spaces in th<' central 

part of the villi, and from there into otlier spactes Ixitween the 

tissues, known as the ladcals. 

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 shouUl 
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. 



320 



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 tmirmnupt mimt hp tied 

applying a tight bandage (ligature) be- ^^ ^ lOUrmquei muSI DC Ilea 

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, — A 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 ivhich 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 
throat." The bronchi end 
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 hoBmo- 




Air passages in the human lungs, a, larynx ; 
6, trachea (or windpipe) ; c, d, bronchi ; 
e, bronchial tubes ; /, cluster of air cells. 



RESPIRATION AND EXCRETION 



331 



glohin 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. -c ^ ■, 

JjToncmal 

of oxygen, 45 to 50 c.c. of Tixbe 

carbon dioxide, and 1 to 2 c.c. 



rroYn. 



^ Jo 
piumonary 




Diagram to show what the blood loses and 
gains in one of the air sacs of the lungs. 



of nitrogen. The same amount fi^'^nonaTy 

artery 

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 mostlj^ 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- 
tains a considerable amount 
of moisture, as may be proved by breathing on a cold 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 
bv the limewater 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 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 amceba, 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 





diaphragm] 



Breathing. — In every 
Ml 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 diaphragm 
ribs, together with the 
contraction of the dia- 
phragm, the muscular 
wall just below the heart ^^Xf'^t ""^^'^^ ^""^ ^^^^^ ^'"^^^^ f Ml breath ; 

•• , {o), alter an expiration. Explain now 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 
rubber over the large end of a bell 
jar. Pass a glass Y-tube through a 




Apparatus to show the mechanics of 
breathing. 



334 



RESPIRATION AND EXCRETION 




i^Gomplemcntal 



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. 





TAir= 
WfCFO^cii=ir^ 



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 ^. ,, i ,, , ^ c l^ -n 
the average lung capacity ^lon 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 



O I-,'.'. V_l?!rl---Iv} : 1 :t ' - ^ J i 



■- -it~' -' 



— _. -^ ^ 



a 



o 



a room (as through the use of electric 
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 WS tttV brrt'^dt, 

other impurities. A good method ventilation? Explain. 






] 



o 






.'. '*- ------i^---- 



1 



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 fine. 

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.^ 

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 




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. 



i 



^ 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 ? 



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 ill 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 arc on the streets. 
The old myth of " night air " 
being injurious 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 anns downward, and press them against the chest, 
thus forcing the air cut 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 bj^ 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 

—Cortex 

—-Medulla 

i^Pyramids 



- Pelvis 



- Ureter 



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; 

°«f:".hll;f :Vr™: third, salts and other waste organic sub- 
lus and tubule: a, artery stanccs, uric acid among them. 

bringing blood to part ; 

h, capillary bringing blood These waste products, together with the 

to glomerulus; h', vessel -^ater containing them, are known as urine. 
continuing with blood to „, , , , , e • , x i • 

vein ; c, vein ; t, tubule ; The total amount 01 nitrogenous waste leavmg 

G, glomerulus. the body each day is about twenty grams. It 




342 



RESPIRATION AND EXCRETION 



is passed through the ureter to the urinanj 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 



Sweatiytict 

Uomy layer 
Figment layer i [M^ 



Sebaceous Gland 



Tactile Organs^ 
Nerve—" 
Blood Vessels - 

Sweat Gland-'Jl^- 
Fat 




> Epiderm.13 



) Dermis 



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 sj^m- 
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 




.^o 



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. Ginn 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 jnaintained f 

(a) What is the inechanisiiv of direction and control ? 

(b) What is the method of direction and control? 

(c) What are habits ? How are they formed and how brohen ? 

(d) Wh(t,t are the organs of sense? What are their uses? 
ie) 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 cerebrospinal 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. Oar 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 pathwa^^s 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 



"-.Dendrites 




Axon 



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-enda 



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, hes the httle 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. 



1 



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 



^t^ Qioisr 



Cerebrum 



Cerebellum 

Medulla 

Spinal Cord 




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. BI. 23 



354 BODY CONTROL AND HABIT FORMATION 




Diagram of the nerve 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 sdme 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 dereUction 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, ad on every opportunity. Second, make a strong start. 
Third, allow no exception. Fourth, for the had 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 oi 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, 
golf, baseball, and other outdoor sports 
combine muscular exercise with brain 




a 




The effect of fatigue on nerve activity of a different sort from that of 

cells. a, healthy brain r • v, i i 

6, fatigued brain cell, busmess or School WOrk. 



cell 



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 oiit from the body covering. At the base of these hairs 
are found neurones which send axons inward to the central nervous sj^stem. 
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- _6 
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 
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 2V of ^^ iiich 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. 




Nerves in the skin: a, nerve fiber; 6, tactile 
papillae, containing a tactile corpuscle ; 
c, papillae containing blood vessels. 
(After Benda.) 



358 BODY CONTROL AND HABIT FORMATION 



Taste Cells 

^Supporting 
' Cells 





c 

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 
Httle 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 beheve 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 hning the upper 
part of the nose. Here are found a large number of rod-shaped cells wliich 
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 ceUs. 

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 irmer end by a tightly stretched mem- 
brane, the tympajiic 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 comphcated apparatus found in the middle ear, to the real organ of 
hearing located in the inner ear. 



BODY CONTROL AND HABIT FORMATION 359 



J^ail. 



JEJ.M. 



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 compHcated organ is lined 
with sensory cells provided with ciUa. 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 filUng 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 
coat, in front, the eye bulges outward 
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 ^ 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 




■Muscle 



Sclerotic Coat 



Longitudinal section through 
the eye. 



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 hujnor. 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 ej^es 
which do not focus clearly 
on objects near at hand are 

said to be farsighted. Still ^^ ^ ,,,,.« 

. , How far away can you read these letters: 

another eye detect is astig- 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 COJNTUOL 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, 




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 amputation 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 | 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, 



Average yvuyY{\)e'r ji^ures 



Conditions, 



3ix 

TiorvalcolaoL 
days. 



1280.66 



Twelve 
alcokol 
days. 



I06J.3 



non-aLcokol 

Two 

alcoViol 
days. 



1086 



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 com.plex 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, 









1 






,OfNUDiTIONS 



10 days 

WITHOUT 
alcohol 



BdBijs 



Average ixme in Tninutes 

no 20 30 

f y f 



IQrmn.Zsec, 



WITH, 
alec 



alcohol 



30min48sec 



4£ days 

WITHOUT 
alcohol 



£6 days 
alcokol 



♦ 



Z\yri\nA7sec. 



Z^mnmlGsec, 



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 : 
' 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 3G7 

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 Tolnian, 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 



10 

9 

8 

7 
6 

4 
3 



M0 N.TUE:5.WED.THUR.TRI. 5AT. 5U N. 




% 
I 




Z 



"A 



ssaul ^ 



# 



/ 



e 



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 Piister made a studj^ 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 LiverCirrhosis 


33.139 


22,211 1 


Typhoid 
~| 2214 

Smallpox 



with other statistics we have been quoting. — Fromihe 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 



Country 



PERCENTAGE. 
10 20 50 40 50 60 tO 80 90 100 



Belgium 




,N GLAND 



Fr, 



ANCE 



Germany 



United 5tate5 



Holland 



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. 

Refebence 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 ive improve our home conditions of 
living ? 

How may we help improve our conditions at school? 

How does the city care for the improvement of our environ- 
ment ? 

(a) In inspection of buildings, etc. 

(&) In inspection of food supplies. 

(c) In inspection of milh. 

(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 darnp 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 




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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 
fiom 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 



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The culture (A) was exposed to the air of a dirty street in the crowded part 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 OF 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 your 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 
proper fire protection. Tene- 
ment inspection should be 

thorough and should aim to provide safe and sanitary homes. 




Dust exhausts on grinding wheels protect 
lungs of the workmen. 



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 and 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 
^, • , , -.u , n J Milk. — Milk when drawn 

Clean cows in 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 also 
known that the tubercle bacillus of cattle and man are much 
ahke in form and action and that the germ from cattle would 
cause tuberculosis in man. Fortunately, the tuberculosis germ 
does not groiv 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 



J L 



J L 



J L 



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[ 




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- 
ample, is very unsafe. 

The waters from deep 
wells or springs if properly 




New York City is spending 8350,000,000 to 
have a pure and abundant water supply. 
This is the tunnel which will bring the 
water from the Catskill Mountains to New 
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 IN 

NORTH OCLMSrORO 






FCSULTtNG CA^r. -^ 



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The city of Lowell in 1891 took its water without filter i7ig, 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 



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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, 
Fa., 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 sewors. A sanitary car toilet is the only remedy. 

HUNTER, CIV. BI. 25 



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Cases of typhoid per 100,000 inhabitants before filtering 
water supply (solid) and after (shaded) in A, Water- 
town, N.Y.; Z?, Albany, N . Y. ; C, Lawrence, Mass.: 
D, Cincinnati, Ohio. What is the effect of filtering 
the water supply ? 



386 MAN'S niPROVEMEXT OF HIS ENVIRONMENT 



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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 mto 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 
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. 



Collecting ashes. 



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- 
roundings made as 
sanitary as possible. 
In the adjoining block 
conditions were left 
unchanged. During 
the summer as flies 
began to breed in the 
manure heaps near the 
stables all manure was 

disiTifepted T^hns the 
The upper picture shows the stables where millions 

of flies were bred ; the lower picture, the disinfec- breeding of flieS WaS 

tion of manure so as to prevent the breeding of 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 




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. 

The Functions of a 
City Board of Health. 
— 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 




In the upper picture a little girl can be seen dump- 
ing garbage from the fire escape. She was a 
foreigner and knew no better. The picture below 
shows the result of such garbage disposal. 



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 tlie person having the disease. So the board of 
health at once isolates any case of disease which may be communi- 



DI5EASFS 


FILTHY AREA 


CLEANED-UPAREA 


TOTAL 
5ICKNE55 


165 1 


MO 1 


COMMUNI CABLC ^tUSM 


36 1 


COMMUNICABLE 


lEB^^^^H 


74 1 


POSSIBLY j^vq^VH 

FLY- BORNE P*a2^B 


m 



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 

Manoeuver 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 



Z Ni3 Il,v. 7^At^my Corp5 
Jacksonvi lleTla.- June-Oct I8S>3 



Nance uvER Div.-5an Ah4TONio 
Texas. Mah.io-JulvIi ,1911. 



MEAN 
STRENGTH 



I0>759 



] 



ia.8oi 



CASES OP 
TYPHOID 



TYPHOID 
DEATHS 



r 



DEATHS 
ALLDISEASES 



2693 

eei 



ONE 

NONE 
11 



Comparison of cases of and death from typhoid in 1898 and 1911. What have we 

learned about combating typhoid since 1898 ? 

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 toTVTis 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 Hfe 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 
beUeved 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 
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. 



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 (w), 
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. 



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 vac- 
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. 



(102 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. 

i 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- 
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 able 




Robert Koch. 



404 



SOME GREAT NAMES IN BIOLOGY 



research work has given the world a much better understanding of 
the problem of acquired immunity. 

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 verv 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 name 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 tivo half cells, one from each parent. The chromosomes 
within the nucleus, we remember, are beheved 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 pupUs 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 o\aile 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 o! 
foods, (b) 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 for Digestion. The com grain. Parts, growth, food 
supply outside body of plant, how does it get inside. Digestion, need for. 
Tost 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 soU. 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. 



i 



APPENDIX 409 

Conditions Favorable and Unfavorable for Growth of 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 HCl 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 100-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 well 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'a 
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, (b) 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, (b) 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, (h) 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 of 
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, (h) 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 r61e 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 Paramecium. 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), 
(d) an insect, (e) a moUusk 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 industries, 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, role 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, (b) 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 of 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 A^aste 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, iron 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 
Enghsh 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. 


2\ pounds 


Gram . . 


gm. 


15J grains avoir- 
dupois. 

^ of an ounce 
avoirdupois. 



Capacity 







61 cubic inches, or 






a little more than 






1 'quart, U. S. 


Licer . . 


1. 


measure. 


Cubic cen- 






timeter . 


cc. 


Ib of a cubic inch. 



Metric 


English Equivalents 


Kilometer 


km. 


f of a mile. 


Meter . . 


m. 


39 inches. 


Decimeter 


dm. 


4 inches. 


Centimeter 


cm. 


f of an inch. 


Millimeter 


mm. 


^ 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 . . 


14 


- 100 . . . - 148 


80 . 


. . 176 

. 158 


30 . , 
20 . . 


. 86 
. 68 


-20 . . 
-30 . . 


. - 4 
. -22 




70 . 


Absolute zero 


60 . . 


. 140 


10 . . 


. 50 


-40 . . 


. -40 


- 273 . . . - 459 




HUNTER, 


CIV. BI 


. — 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 |". 
50 test tubes on base (excellent for denaonstrations). 

2 graduated cylinders, one to 100 c.c, one to 500 c.c. 

1 package filter paper 3(X) 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 | 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. | lb. copper sulphate. 

10 scapels. 1 liter formol. ^ lb. sodium hydroxide. 

12 mason jars, pints. 1 oz. iodine cryst. | lb. 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 diflicult 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 tj'pe.) 



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. 
AlgsD, 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. 
AnvU, 359. 



419 



420 



INDEX 



Aorta, 320. 
Apoplexj% 328. 
Appendages of the fisii, 233. 
Appendicular 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 ; 



4 



I 



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. 
CapiUaries, 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. 

ChlorophyU 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 ; 

structm^e, 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 kilHng 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. 
CrocodUe, 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. 



i 



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 nose 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 ; 

ckculation, 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. 
Fimctions, 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. 
GiUs 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. 
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. 

Hiluin, 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; 

?^nd foods, 370 J 



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. 
Jjength 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, 2G8. 
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. 

VEacNichol, 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; 

yelloAv 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 malariae, 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. 
PoUen, 36 ; 

germination of, 53, 54. 
PoUination, 36, 40 ; 

cross and self, 40 ; 

wind, 44. 
Pond scum, 173. 
Pons, 352. 
Porifera, 182. 

Portal cu-culation, 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. 
Prologs, 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, 309. 
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 casca, 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 Paramcecium, 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 gra\'ity, 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. 
Salivarj^ glands, 299 ; 

glands of frog, 243. 
Salmon, 201, 241. 
Sand shark, 186. 
Sandworm, 184. 

Sanitarium for tuberculosis, 394. 
Sanitation, 27. 
Saprophytes, 131. 
Seavangers, 150. 
Schleiden and Schwann, 398. 
Schultz, Max, 398. 
Sclerotic coat, 360. 
Sea anemones, 183. 
Secretion, 299, 306. 
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, 206. 
Spore, 131, 173; 

plants, 174. 
Sporozoa, 182. 
Sprengel, Conrad, 40. 
Squash bug, 215. 
Stables, clean and filthy, 388. 
Stamens, 36. 
Starch, action of diastase, 60 ; 

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. 
StuTup, 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. 
Systematic circulation, 320. 



Table of cost of food, 

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. 



276, 



432 



INDEX 



Tidal air, 334. 

Timber, methods of cutting. 111. 

Tissue cells, 49, 179. 

Toad, use of, 209. 

Tobacco and oirculation, 328; 

and respiration, 34(3 ; 

users of, 293. 
Tortoise, 188. 
Touch, 357. 
Tourniquet, 326. 
Toxin, 152, 31(3. 
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. 
T^vig, 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, 1 17 ; 

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, 186. 
Vertebrates, breathing of, 232. 
Villi, 308. 

Virginia creeper, 128. 
Virus, 392. 
Vitreous humor, 361. 
Vorticella, 171, 178. 
Vries, Hugo de, 253, 406. 

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. 



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S. C. State CoUegt 






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