Chapter I: Part 1

A CIVIC BIOLOGY

Presented in Problems

BY

GEORGE WILLIAM HUNTER, A.M.

HEAD OF THE DEPARTMENT OF BIOLOGY, DE WITT CLINTON
HIGH SCHOOL, CITY OF NEW YORK.

AUTHOR OF "ELEMENTS OF BIOLOGY," "ESSENTIALS OF
BIOLOGY," ETC.

AMERICAN BOOK COMPANY

NEW YORK CINCINNATI CHICAGO

COPYRIGHT, 1914, BY
GEORGE WILLIAM HUNTER.
COPYRIGHT, 1914, IN GREAT BRITAIN.

* * * * *

HUNTER, CIVIC BIOLOGY.
W. P. 3

Dedicated
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

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 secondary 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 pedagogic 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 meaning of some of his concepts. Therefore, the first science of the secondary school, elementary biology, should be primarily the vehicle by which the child is taught to solve problems and to think straight in so doing. No other subject is more capable of logical development. No subject is more vital because of its relation to the vital things in the life of the child. A series of experiments and demonstrations, discussed and applied as definite concrete problems which have arisen within the child's horizon, will develop power in thinking more surely than any other subject in the first year of the secondary school.

But in our eagerness to develop the power of logical thinking we must not lose sight of the previous training of our pupil. Up to this time the method of induction, that handmaiden of logical thought, has been almost unknown. Concepts have been formed deductively by a series of comparisons. All concepts have been handed down by the authority of the teacher or the text; the inductive search for the unknown is as yet a closed book. It is unwise, then, to directly introduce the pupil to the method of induction with a series of printed directions which, though definite in the mind of the teacher because of his wider horizon, mean 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 conclusion, 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 instance, 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 usually
are so planned as to anticipate any ideas that might
naturally crop up in the pupil's mind during the drawing
exercise.

"Such an abuse of the laboratory idea is all wrong and
should be avoided. The ideal laboratory ought to be a
retreat for rainy days; a substitute for out of doors; a
clearing house of ideas brought in from the outside. Any
course in biology which can be confined within four walls,
even if these walls be of a modern, well-equipped
laboratory, is in some measure a failure. Living things, to
be appreciated and correctly interpreted, must be seen and
studied in the open where they will be encountered
throughout life. _The place where an animal or plant is
found is just as important a characteristic as its shape or
function._ Impossible field excursions with large classes
within school hours, which only bring confusion to
_inflexible_ school programs, are not necessary to
accomplish this result. Properly administered, it is without
doubt one of our most efficient devices 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 biological 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 biological science, the interests of the children have been kept in the foreground. In a recent questionnaire sent out by the author and answered by over three thousand children studying biology in the secondary schools of Connecticut, Massachusetts, New Jersey, and New York by far the greatest number gave as the most interesting topics those relating to the care and functions of the human body and the control and betterment of the environment. As would be expected, boys have different biological interests from girls, and children in rural schools wish to study different topics from those in congested districts in large communities. The time has come when we must frankly recognize these interests and adapt the content of our courses in biology to interpret the _immediate_ world of the pupil.

With this end in view the following pages have been written. This book shows boys and girls living in an urban community how they may best live within their own environment and how they may cooperate with the civic authorities for the betterment of their environment. A logical course is built up around the 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 preparation 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 connection with their relations to green plants and especially in their relation 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 mankind, 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 subject 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 phenomena and of the needs of organisms for oxygen, food, and reproduction 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 knowing 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 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 Department of Biology in the Stuyvesant High School; George E. Hewitt, George T. Hastings, John D. McCarthy, and Frank M. Wheat, all of the Department of Biology in the De Witt Clinton High School.

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

At the end of each of the following chapters is a list of books which have proved their use either as reference reading for students or as aids to the teacher. Most of the books mentioned are within the means of the small school. Two sets are expensive: one, _The Natural History of Plants_, by Kerner, translated by Oliver, published by Henry Holt and Company, in two volumes, at $11; the other, _Plant Geography upon a Physiological Basis_, by Schimper, published by the Clarendon Press, $12; but both works are invaluable 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, _General 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 Company; and McMurry's _How to Study_, Houghton Mifflin Company.

CONTENTS

CHAPTER PAGE

FOREWORD TO TEACHERS 7

I. SOME REASONS FOR THE STUDY OF BIOLOGY 15

II. THE ENVIRONMENT OF PLANTS AND ANIMALS 19

III. THE INTERRELATIONS OF PLANTS AND ANIMALS 28

IV. THE FUNCTIONS AND COMPOSITION OF LIVING THINGS 47

V. PLANT GROWTH AND NUTRITION--THE CAUSES OF GROWTH 58

VI. THE ORGANS OF NUTRITION IN PLANTS--THE SOIL AND
ITS RELATION TO ROOTS 71

VII. PLANT GROWTH AND NUTRITION--PLANTS MAKE FOOD 84

VIII. PLANT GROWTH AND NUTRITION--THE CIRCULATION AND
FINAL USES OF FOOD BY PLANTS 97

IX. OUR FORESTS, THEIR USES AND THE NECESSITY OF THEIR
PROTECTION 105

X. THE ECONOMIC RELATION OF GREEN PLANTS TO MAN 117

XI. PLANTS WITHOUT CHLOROPHYLL IN THEIR RELATION TO
MAN 130

XII. THE RELATIONS OF PLANTS TO ANIMALS 159

XIII. SINGLE-CELLED ANIMALS CONSIDERED AS ORGANISMS 166

XIV. DIVISION OF LABOR, THE VARIOUS FORMS OF PLANTS AND
ANIMALS 173

XV. THE ECONOMIC IMPORTANCE OF ANIMALS 197

XVI. AN INTRODUCTORY STUDY OF VERTEBRATES 232

XVII. HEREDITY, VARIATION, PLANT AND ANIMAL BREEDING 249

XVIII. THE HUMAN MACHINE AND ITS NEEDS 266

XIX. FOODS AND DIETARIES 272

XX. DIGESTION AND ABSORPTION 296

XXI. 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
OF TOPICS FOR COURSE BEGINNING IN FALL 407

SUGGESTED SYLLABUS FOR COURSE IN BIOLOGY BEGINNING
IN FEBRUARY AND ENDING THE NEXT JANUARY 411

HYGIENE OUTLINE 415

WEIGHTS, MEASURES, AND TEMPERATURES 417

SUGGESTIONS FOR LABORATORY EQUIPMENT 418

INDEX 419

A CIVIC BIOLOGY

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

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

Why study Biology?--Although biology is a very modern science, it has found its way into most high schools; and an increasingly 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. We do not always realize that if it were not for the green plants, there would be no animals on the earth. Green plants furnish food to animals. Even the meat-eating animals feed upon those that feed upon plants. How the plants manufacture this food and the relation they bear to animals will be discussed in later chapters. Plants furnish man with the greater part of his food in the form of grains and cereals, fruits and nuts, edible roots and leaves; they provide his domesticated animals with food; they give him timber for his houses and wood and coal for his fires; they provide him with pulp wood, from which he makes his paper, and oak galls, from which he may make ink. Much of man's clothing and the thread with which it is sewed together come from fiber-producing plants. Most medicines, beverages, flavoring extracts, and spices are plant products, while plants are made use of in hundreds of ways in the useful arts and trades, producing varnishes, dyestuffs, rubber, and other products.

Bacteria in their Relation to Man.--In still another way, certain plants vitally affect mankind. Tiny plants, called _bacteria_, so small that millions can exist in a single drop of fluid, exist almost everywhere about us,--in water, soil, food, and the air. They play a tremendous part in shaping the destiny of man on the earth. They help him in that they act as scavengers, causing things to decay; thus they remove the dead bodies of plants and animals from the surface of the earth, and turn this material back to the ground; they assist the tanner; they help make cheese and butter; they improve the soil for crop growing; so the farmer cannot 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 diseases, 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 disappear 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 important part in the world in causing and carrying disease. Animals that cause disease are usually tiny, and live in other animals as _parasites_; that is, they get their living from their hosts on which they feed. Among the diseases caused by parasitic animals are malaria, yellow fever, the sleeping sickness, and the hookworm disease. Animals also _carry_ disease, especially the flies and mosquitoes; rats and other animals are also well known as spreaders of disease.

From a money standpoint, animals called insects do much harm. It is estimated that in this country alone they are annually responsible 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, tortoise shell, corals, and mother-of-pearl; from animals come perfumes 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 understandingly 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 subject to floods, and are in many places barren. On the forests depend our supply of timber, our future water power, and the future commercial importance of cities which, like New York, are located at the mouths of our navigable rivers.

Plants and Animals mutually Helpful.--Most plants and animals 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 temperature, 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 society 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. Animals, lowly and complex, sacrifice their comfort and their very lives for their young. In the insect communities the welfare of the individual is given up for the best interests of the community. The law of mutual give and take, of sacrifice for the common good, is seen everywhere. This should teach us, as we come to take our places in society, to be willing to give up our individual pleasure or selfish gain for the good of the community in which we live. Thus the application of biological principles will benefit society.

II. THE ENVIRONMENT OF PLANTS AND ANIMALS

_Problem.--To discover some of the factors of the environment of plants and
animals._
_(a) Environment of a plant._
_(b) Environment of an animal._
_(c) Home 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
environment and how I can aid in their control.

Environment.--Each one of us, no matter where he lives, comes in contact with certain surroundings. Air is everywhere around us; light is necessary to us, so much so that we use artificial light at night. The city street, with its dirty and hard paving stones, has come to take the place of the soil of the village or farm. Water and food are a necessary part of our surroundings. 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 practically the same things from their environment 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 environment 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 elements, _oxygen_ and _nitrogen_. Water, by means of an electric current, may be broken up into two elements, _oxygen_ and _hydrogen_. The elements in water are combined to make a _chemical compound_. The oxygen and nitrogen of the air are not so united, but exist as separate gases. If we were to study 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 elements 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 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 wonderful manner build up their own bodies from the materials found in their environment. 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 important 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 indifferent 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 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 intensity of light and heat. Look at the shady side of a city street on any hot day to prove this statement.

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 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 animals, cannot stand great changes without discomfort and sometimes 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 deg. Fahrenheit.

The Environment determines the Kind of Animals and Plants within It.--In our study of geography we learned that certain 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 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, 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 execute 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 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 structures, to do that work. It is because of these adaptations that living things are able to do their work within their particular environment.

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 something that the fish needs. Each plant and animal is limited to a certain environment because of certain individual needs which make the surroundings fit for it to live in.

Changes in Environment.--Most plants and animals do not change their environment. Trees, green plants of all kinds, and some animals remain 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 environment. Men who lived on the earth thousands of year ago did not wear clothes or have elaborate 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 environment from that of other animals. The living together of men in communities has caused certain needs to develop. Many things can be supplied in common, as water, milk, foods. Wastes of all kinds have to be disposed of in a town or city. Houses have come to be placed close together, or piled on top of each other, as in the modern apartment. Fields and trees, all outdoor life, has practically disappeared. Man has come to live in an artificial environment.

Care and Improvement of One's Environment.--Man can modify or change his surroundings by making this artificial environment 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 _sanitation_, while the care of the _individual_ for himself within the environment 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_. American 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 general 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.

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. Everywhere 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_, 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 recognize a few examples of the common forms that might be met on a field trip. In the fields, on grass, or on flowering plants we may count on finding members from six groups or _orders_ of insects. These may be known by the following characters.

The order _Hymenoptera_ (membrane wing) to which the bees, wasps, and ants belong is the only insect 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 characteristics, 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.

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

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

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

Other forms of life, especially _spiders_, which have four pairs of walking legs, _centipedes_ and _millepedes_, both of which are wormlike 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 wormlike 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 caterpillar legs. The animal at this stage is known as a _larva_.

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 caterpillar 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 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 insects 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 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 interrelations between insects and flowers. It is easy on a field trip to find insects lighting upon flowers. They evidently have a reason for doing this. To find out why they go there and what they do when there, it will be first necessary for us to study flowers with the idea of finding out what the insects get from them, and what the flowers get from the insects.

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

The Floral Envelope.--In a flower the expanded portion of the flower stalk, which holds the parts of the flower, is called the _receptacle_. _The green leaflike parts covering the unopened flower are called the sepals._ Together they form the _calyx_.

_The more brightly colored structures are the petals._ Together they form the _corolla_. The corolla is of importance, as we shall see later, in making the flower conspicuous. Frequently the petals or corolla have bright marks or dots which lead down to the base of the cup of the flower, where a sweet fluid called _nectar_ is made and secreted. It is principally this food substance, later made into honey by bees, that makes flowers attractive to insects.

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

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

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

Field Work.--Is Color or Odor in a Flower an Attraction to an Insect?--Sir John Lubbock tried an experiment which it would pay a number of careful pupils to repeat. He placed a few drops of honey on glass slips and placed them over papers of various colors. In this way he found that the honeybee, for example, could evidently distinguish different colors. Bees seemed to prefer blue to any other color. Flowers of a yellow or flesh color were preferred by flies. It would be of considerable interest for some student to work out this problem with our native bees and with other insects by using paper flowers and honey or sirup. Test the keenness 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.