Biology and human welfare.

Front matter

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Preface

Twenty years ago, the authors, in common with many other earnest teachers of biology, became convinced that much more emphasis should be placed on the functions of living organisms as contrasted with their structure and that a comparative study should be made of plants, animals, and the human body. These two aims were prominent in our Elementary Biology published in 1912, in which Part I was devoted to plants; Part II, to animals; and Part III, to the human body.

Biology and Human Welfare represents the development of our ideas, based on the observation and experience of ten years and more since the publication of the earlier book, of the best means of realizing these aims. This is a new book, made on a new plan of organization, with distinctive features, some of which are as follows:

1. We have become convinced that a given function, for example, digestion or respiration, can be presented more effectively by considering in turn how the process 1s carried on mn plants, in animals, and in the human body than by studying plants, animals, and’man as separate units and completing ithe study of one before taking up the study of the others. Adolescent boys and girls are most interested in those facts and principles of biology that relate closely to themselves. Therefore, to defer a discussion of human biology to the last part of the course results in a distinct loss of interest on the part of the pupils and prevents the immediate and effective application to human life of the various principles derived from a laboratory study of plants and animals. In studying y vi PREFACE the special function in the three spheres, boys and girls are led to see the essential likenesses in the work done by all living things rather than relatively unessential differences in structure.

2. The dominating purpose throughout this book is to show the wntimate relation of biological science to human welfare. This has been the guiding principle both in the selection of topics and in the method of treatment. An examination of the Table of Contents will show that in Part I we have discussed our lifeless and living environment; in Part II, the nutritive and reproductive functions of living organisms; in Part III, plants and animals that are specially related to human welfare. In Part IV we have grouped certain chapters relating to the functions of three groups of animals and certain topics relating to the human body which may well be studied if time allows, but which we do not consider so important for beginners as the topics treated in Parts I, I, and III.

The field of biology is so large and some of its problems are so difficult that a wise selection of topics must be made if a text is to attain its maximum usefulness. Consequently, some topics that are often found in secondary school texts, but that are more suitable for discussion in advanced courses, have been omitted. Among these may be mentioned Mendel’s laws, theories of evolution,! and mitosis. On the other hand, topics of everyday interest and importance, for example, vitamins, insulin, and the newer discoveries relating to health and disease, have been included. The wise and

1“*The prominent evidences of relationship suggesting evolution, within such groups as the decapods, the insects, and the vertebrates, should be demonstrated. A few facts indicating the struggle for existence, adaptation to environment, variations of individuals, and man’s selective influence should be pointed out; but the factors of evolution and the discussion of its theories should not be attempted.’’ — Quoted from the syllabus in advanced zoology published by the College Entrance Examination Board and the New York State Department of Education (1921). This syllabus is based upon the report of a committee of the American Society of Zoologists, Eastern Branch.

PREFACE Vit enthusiastic biology teacher can do much to arouse interest in discoveries like these that mean so much for human welfare.

- The book includes more material than can be taught successfully in a single year under ordinary conditions; hence each teacher is free to select those topics that best fit the needs of the pupils he is instructing. We have indicated our judgment as to the relative importance of the topics not only by the grouping referred to above, but also by the use in the text of smaller type for topics that may be omitted.

3. The material of the book has been carefully tested in the classroom. For five years we have supplied in mimeographed form text and laboratory outlines for the course given to each of the students who studied biology in the high schools in which we teach. In this way we have been able to profit by the criticisms and suggestions of thousands of students and more than thirty teachers of biology. Term by term we have modified this material, adapting it ever more closely to varying conditions of instruction.

4. Laboratory work 1s most wmportant in arousing the inlerest of pupils and in fixing in their minds essential facts and principles. We have chosen for laboratory study plants and animals that are available in most parts of the country. The laboratory exercises have been included in the body of the book, because they constitute an essential part of the course and because they are more convenient for use here than they wculd be if placed in a separate volume or in appendixes.

5. By the use of the summaries and the renew questions

placed at the end of most of the chapters, pupils can be held to a stricter account for preparing their lessons and for retaining in mind the essentials of each vmportant topic. Diagrams, also, like those illustrating the carbon cycle (Fig. 130), vill PREFACE the nitrogen cycle (Fig. 203), the energy: cycle (Fig. 37), and food manufacture and storage (Fig. 44), have been found to make clearer an understanding of these somewhat difficult but essential processes.

We are deeply indebted to many friends and specialists in particular fields for assistance in reviewing the manuscript either as a whole or in parts. Dr. C. Stuart Gager, Director of the Brooklyn Botanic Garden, Dr. Elsie M. Kupfer, Head of the Department of Biology in the Wadleigh High School of New York City, and Mr. Harold E. Foster, Administrative Assistant in the Morris High School, New York City, have carefully read and criticized the manu- ‘script of the whole book. Dr. W. H. Park, Director of the Laboratories of the New York Board of Health, Dr. Hideyo Noguchi of the Rockefeller Institute, and Dr. F. F. Russell of the Rockefeller Foundation have given valuable = assistance in the chapters relating to health and disease. To the following specialists of the United States Government at Washington we are particularly indebted for counsel and help on the chapters named: Dr. E. W. Nelson, the chapter on mammals; Dr. L. O. Howard, on insects; Dr. Harry C. Oberholser, on birds; Dr. Frederick V. Coville and Dr. W. KE. Safford, on plants in relation to human welfare; Dr. Hugh Smith, formerly United States Commissioner of Fisheries, on fish; Mr. Thomas H. Gill of the Forest Service, on forestry. Dr. W. A. Bastedo, author of Materia Medica; Pharmacology; Therapeutics; Prescription Writing has read the chapters on digestion in man and on beverages and drugs; Dr. George H. Parker of Harvard University, the chapter on how our bodies are controlled; Dr. G. N. Calkins of Columbia University, author of Protozoa, on single-celled animals; Dr. Walter H. Eddy, of Columbia University and Major in Charge of Nutrition of the American Expeditionary

PREFACE: | ie

Forces in France, on food and diet; Dr. C.-E. A. Winsiow of Yale University, on breathing in man and animals; Dr. M. A. Bigelow of Teachers College, on reproduction in plants and animals.

To the following persons we are also indebted for much assistance in connection with various chapters: Dr. Jacques Loeb of the Rockefeller Institute; Dr. Herbert E. Walter, Brown University; Dr. W. T. Hornaday of the New York Zoological Park; Dr. Frank M. Chapman, American Museum of Natural History; Mr. Paul B. Mann, Head of the Department of Biology of the Evander Childs High School, New York City; Dr. Walter B. Cannon and Dr. Percy G. Stiles, Harvard Medical School; Dr. Lyda M. Degener of the Wistar Institute, Philadelphia; Dr. Meyer Bodansky of the Medical School of the University of Texas; Dr. H. H. Goddard of the Ohio State University; Dr. Caroline Latimer of Baltimore; Mr. John R. Kissinger; and especially to the many teachers in our own departments.

P. Blakiston’s Son & Co., the publishers of Gager’s Fundamentals of Botany, have been most generous in allowing us to select freely from the wealth of illustrations in Dr. Gager’s book. To Henry Holt and Company we are also deeply indebted for permission to use drawings published in Sargent’s Plants and Their Uses. The World Book Company and Dr. Transeau, the author of General Botany, kindly sent us their original drawings for Figs. 77 and 155. To the American Museum of Natural History, the New York Zoological Society, and especially to Mr. Elwin R. Sanborn, its photographer, to the National Audubon Society, the National Tuberculosis Association, the New York Board of Health, the American Red Cross, and to Dr. L. L. Woodruff of Yale University, and Dr. J. F. Williams of Teachers College, we are indebted for illustrations we have been

1 PREFACE permitted to use. The many new drawings that appear in the book are almost wholly the work of Mr. B. F. Williamson and Mr. J. de Muro.

Jake January 14, 1924 Ay Eero?

Chapter f.

II. TY. by

V.

VI.

VAG VIII.

IX.

xT; XII.

XII.

XLV. nV mmyenotOur voods Ate Made. 2 a. 00600. oe ee 8D How Plants Manufacture Foods. . Ri ee ee How Living Things Are Able To Do Worke Bae tia OU How Living Organisms Are Constructed . . . . . 73 Vena conoid MatrandewWhy 50% es sue SU BY How Drugs and Beverages Affect Us... 102 How Foods Are Prepared for Distribution and le in

Living Things. . 125 How Water and Other ciinetances re peor bod ee

Distributed in Plants... 144 How the Human Body Is Fitted aah Renline Foods Ready

for Distribution and Use... ; 165 How Circulation Is Carried On in Aire Hainan Bode ST tess How Living Organisms Breathe . . . ve, abe How Certain Living Things Carry On Seintatieatien Pee eD How Flowering Plants Reproduce .. . . . . . 244 How Plant Propagation Is Carried On . . . . . . 264

PART III— PLANTS AND ANIMALS IN RELATION TO HUMAN WELFARE How Microscopic Organisms Are Related to Health and

Disease... ereset Ue Dt How Plants Are Santen te Hartan Welfare eh a UO How Fishes Are Related to Human Welfare . . . . 345 How Insects Are Related to Human Welfare . . .. . 366 How Birds Are Related to Human Welfare AE os sel

How Mammals Are Related to Human Welfare... . 481 al

Xll

CONTENTS

Part Iv—additional Biological Studies XXII

OT, XXIV.

XXV.

XXVI.

SORE APPENDIX .

INDEX .

How Single-celled Animals Carry On Their Functions How Crayfishes Carry On Their Functions .

How Frogs Carry On Their Functions ;

How Protection and Locomotion Are Secured .

How Our Bodies Are Controlled .

On What Success in Life Depends

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BIOLOGY AND HUMAN WELFARK

Chapter I The World We Live In

Some questions we might ask about the world in which we live.

How far does this universe of ours extend?

What is the world we live in made of?

How much of the world is alive and how much is lifeless?

Which living things help us and which harm us?

To what extent are we responsible for our health or sickness?

1. What is the use of asking questions? Every normal boy or girl is an animated interrogation point. About as soon as he begins to talk, he asks questions — Why? How? When? Where? If he is brought up properly by parents and teachers, he will continue to ask questions all through childhood and youth, and even through manhood and old age. The growing mind is a mind that is continually eager for new knowledge — a mind that asks questions.

In early childhood, the answers to our questions naturally came from our parents, brothers and sisters, or other relatives and friends. But as we grew older, we learned that we could find answers to our questions elsewhere. Of course we learn much from the printed page. But a better method of acquiring knowledge is to study directly the world about 3 us. ‘‘Study nature, not books,” said Professor Agassiz

(Fig. 1), who was the greatest biology teacher of his time. One of the compelling attractions in the study of science arises from the fact that young people are brought by work along this line into more direct contact with the universe of which they area part. If we wish to study heavenly bodies, we use the telescope; if we are trying to detera ooetey \\\4, , === | mine the minute struc- Se XS Danie ture of plants and Fig. 1. — Louis Agassiz (1807-1873) animals, the hand lens The great teacher of biology. and. c ompoun d microscope (Fig. 48) are available; if we are seeking to understand the chemical composition of various things about us, we make use of chemieals, test tubes, and other pieces of apparatus (Fig. 2). Experiments of one sort or another are continually tried, either in the laboratory or outside. In addition to the absorbing interest in carrying on work of this kind, we find that knowledge gained by direct observation and experiment sticks in our minds far more tenaciously than do facts obtained from books or from questions that are answered by others.

Think what we owe to the great scientists who not only asked questions but also worked out the answers to these questions! When the great. biologist Pasteur (215) was given the problem of saving the grape crop in France, he asked himself so many questions that, before he had answered i ing Galloway

© Ew ical laboratory ined and t

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F tion of foods ty.

ir -puri ts are made for thei es eterm is d si

‘Here the compo half of them, he discovered the cause, prevention, and cure of some of the worst diseases that afflict man and animals. Charles Darwin (Fig. 3), to whom the world owes a great part of its modern progress in biology, spent twenty years in getting answers to puzzling questions as to how plants and animals came to resemble and to differ from each other. He then published one of the epoch-making books of all time, On the Origin of Species. Even if we can not hope to be Pasteurs or Darwins,

_| we can at least keep

Fig. 3. — Charles Darwin (1809-1882) our eyes and ears open: For fifty years a painstaking investigator of problems bearing on the theory of the origin of We Can be constantly

ENED tire | learning new and interesting facts; and we may be able to contribute something of real value to the sum total of human knowledge.

I. Our ENVIRONMENT

2. What is meant by our environment. Ordinarily when we speak of our environment —by which we mean our surroundings — we think of our home and family, our school and schoolmates, and other things both living and lifeless about us. .But we must extend the term “environment”’ if we are to understand its full significance. A number of homes, schoolhouses, and other buildings with their occupants make up a community, a town, or a large city. Air, water, fuel, means of lighting, parks and playgrounds, the fields and woods, all of which are essential to our health and happiness, are parts of our environment. So too are the trolleys, the railroads, and other means of communication.

When we think of our dependence on the grains, vegetables, meats, milk, and butter, which are furnished by farmers who may live hundreds of miles away, we realize that our environment is much wider than we had suspected. Our clothing is made from the cotton or linen fibers obtained from plants (Fig. 201) that grow in widely distant localities or from the wool, hides, fur, or feathers of animals or from the silk spun by the silkworm (Fig. 238). Distant from most of us too are the coal mines of Pennsylvania, the orange groves of California or Florida, and the spice trees of Africa or India. Since the whole earth, therefore, contributes to our comfort and enjoyment, we may rightly claim it all as a part of our environment.

But further study shows us that, were it not for the rays of light and heat from the sun, all life would cease. Scientists tell us that all the food supply of the world is made by green plants and that these green plants, which are our food factories, can not carry on their work without sunlight (26). Hence the sun that is the center of our solar system is a most essential part of our environment.

The sun, however, even though it is 93,000,000 miles away, seems relatively near us when we learn that many of the stars that we see on a clear night, even those that are nearest to us, are in reality so far away that the human mind can not conceive of such distances. Yet all these heavenly bodies are a part of our environment and have to do with human welfare. For instance, the mariner, even in these days, pilots his course over the sea by observing the sun by day and the stars by night. The daily rise and fall of the tides mainly result from the changing position of the moon with reference to the earth. Our environment then in ils broadest sense extends to the farthest confines of the

Photo by Brown Brie: 7 Fig. 4. — Good country environment

Name several respects in which this country environment is far better than that shown in Fig. 5.

universe and includes everything that affects us whether for good or ill.

3. How we can change our environment. Since our lives are affected so greatly by our surroundings, it is important to understand as fully as possible our environment to the end that we may multiply those influences that are beneficial and get rid of those that are harmful. If by bad management we permit house flies to breed, typhoid fever is very likely to increase, since these flies often carry the germs of typhoid fever on their hairy bodies (277). Again, if honeybees are raised in the vicinity of a fruit orchard (Fig. 248), the fruit crop becomes considerably larger because the bees help in fruit production (269). Since a farmer can determine whether he will raise bees or flies, vegetables

Fig. 5. — Bad country environment 4 State several ways in which this slovenly environment could be improved.

or weeds, it is evident that he is responsible largely for the immediate environment in which he lives (Figs. 4, 5). So each one of us is more or less responsible for his surroundings and the more so as he grows older. Even as highschool students we can keep our rooms at home and our desks and lockers at school clean or dirty, and we can see to it that the places we live in are well-ventilated or stuffy. We can and do choose our associates. So we make the environment in which we work and play wholesome (Fig. 6) or unwholesome (Fig. 7) for body and mind.

f & y Photo by Brown Bros.

Fig. 6. — Good city environment

Name as many attractive features of this city yard as you can. Can you suggest any improvements?

Il. Tue Arr as A Part oF OuR ENVIRONMENT 4. How we become conscious of the presence of air. A moment’s thought will convince us that the part of our environment which is nearest to us and most constantly necessary is the air. Under ordinary conditions we are not conscious of this mantle of air everywhere about us since we do not smell it, taste it, see it, or feel it.

When air is set in motion, however, as on a windy day, we have distinct evidence that it is a substance, especially

Photo by Brown Bros.

Fig. 7. — Bad city environment

What objections would you have to living in sight of surroundings like this? How can such conditions be remedied?

when our hats are blown off suddenly or our umbrellas are turned inside out. Let us see whether we can prove by experiments that an invisible gas like air is as real a substance as are water, wood, and soil. We know that each of these substances occupies space and exerts pressure. Is this true of air also? The following experiments will help us to answer this question.

Does air occupy space? Home experiment.

Invert a tumbler in a glass dish, about three inches deep, containing water, and press the glass down to the bottom of the dish.

1. State what you have done.

With what was the apparently empty inverted glass filled? Compare the level of the water inside and outside the glass. What prevents the water from rising into the glass? What proof have you from this experiment that air occupies space.

ne eh

Does air exert pressure? Home experiment.

Fill a tumbler full of water and cover with a piece of paper, pressing down on the paper with the palm of the hand. Remove the hand and quickly invert the tumbler of water. (It is best to perform this experiment over a sink.)

1. Describe what you have done and state the result.

2. What proof have you that air exerts an upward pressure?

x. What the extent of our environment of air is. Air is one of the most immediate parts of our environment. Not only does it surround our bodies and penetrate our clothing, but it also fills spaces between the particles of soil; it is dissolved in water, for we can sometimes see the bubbles of air collecting on the inner side of a glass of water that has been allowed to stand for a time. Air extends outward from the earth’s surface to a distance of perhaps two hundred miles.

At sea level the air is dense enough to press upon every square inch of surface with a weight equal to about fifteen pounds. Scientists have shown that this pressure of the air can support not only the weight of a tumblerful of water but also that of a column of water thirty feet high or of mercury thirty inches high (Fig. 8) in a pipe that is closed at the top, provided the air inside the tube has been removed. 7

If we leave sea level and go up on a mountain top or if we ascend in a balloon or an airplane, the height of the air above us becomes less and less, and consequently its weight and pressure becomes less than fifteen pounds per square inch. At a height of several miles the atmosphere becomes so rarefied, that is, so very thin, that aviators find it necessary to carry oxygen to breathe when they ascend to higher levels. A device has recently been invented by which the airplane engine also may be supplied with oxygen in order to ascend still higher.

Vacuum

Is air composed of more than one kind of gas? Laboratory demonstration.

Pressure of Air

Fasten a three-inch piece of a good-sized candle to a piece of cardboard about three inches square, and place the cardboard beneath the surface of a dish of clear limewater about two inches deep.

Light the candle and quickly invert a pint bottle Fig. 8. — Torricellian containing air over the flame, in such a way that tube only a part of the mouth of the bottle touches What does this exthe cardboard beneath the limewater (Fig. 9). periment demonstrate?

1. Describe the experiment, or draw and label the apparatus.

2. What do you note in regard to the flame after a brief time?

3. Nore! (to be copied in the notebook). The substance in the air that causes the candle to burn is oxygen. 7

4. Why does the candle soon cease to burn?

1 All Norss should be copied by the student into his notebook and should be enclosed in quotation marks,

5. Gently shake the limewater in the bottle. What change do you note in the level and in the appearance of the limewater inside the bottle?

6. Nore (to be copied in the notebook). When the candle burns, a substance known as carbon dioxid is formed by the union of the oxygen of the air with a substance found in the candle. This gas (carbon dioxid) is gradually absorbed by the limewater and so is removed from the air we are testing.

7. Is all the air consumed by the burning of the candle? How do you know?

8. Press the sheet of cardboard against the mouth of the jar and quickly turn it right side up, without losing any of the gas or liquid. Light a splinter of wood, quickly move the cardboard to one side, and instantly thrust the burning splinter into the gas.

Fig. 9. — Burning candle experiment a. Describe what is How long will the candle continue to burn in the done. bottle of air? b. Does the splinter continue to burn? c. What proof have you that a gas other than oxygen is found in the air? This second gas is known as nitrogen. 9. What proof have you, therefore, that air is composed of more than one kind of gas?

6. What the two principal gases found in air are. In ancient times air was thought to be a single substance. Indeed some of the Greek philosophers believed that the universe was made up of four simple “principles,” or substances: earth, air, fire, and water. Early in the seventeenth century, however, it was ascertained, as we have just proved, that the gas which remained in an enclosed space where something had been burned (e.g.1 a candle) could not support burning. The gas now known as nitrogen was then called “‘destroyed air,’ and the original air containing oxygen was spoken of as ‘“‘fire air.’ It was not, however, until the second half of the eighteenth century, just before the American Revolution, that the true nature of the two principal gases in air was revealed by the celebrated French chemist Antoine Lavoisier. By a long series of experiments he proved that about one fifth of the air consists of a gas, oxygen, which supports burning and that four fifths is made up of another gas, nitrogen, which does not support burning.

7. What other substances are found in air. Another substance found in air is water vapor. Ordinarily this is invisible, like oxygen and nitrogen. When the temperature of the air drops sufficiently, however, the vapor condenses in tiny droplets to form fog (Fig. 10), and further condensation brings down the moisture in drops of rain. If the temperature drops still lower, flakes of snow are formed. ‘That water vapor is present even on a clear day can often be proved by looking at the outside surface of an ice pitcher, for we find it covered with beads of moisture. These drops do not come from the water within the pitcher as many people think. Instead, they are formed on the cold surface. by the cooling and condensation of the invisible moisture of the surrounding atmosphere.’

In addition to oxygen, nitrogen, and water vapor, air contains still another very important substance but in relatively minute quantities. When the candle was burned leg. means for example.

2 The presence of moisture in air may be shown even better by the use of a highly polished metal container used in determining the dew point. The advantage of using the highly polished metal surface is that one can see the slightest deposit of moisture.

in the bottle of air, we found that a gas was produced which turned the limewater milky. The name of this gas is carbon dioxid. Since carbon dioxid is the only gas that will

Photo by Ewing Galloway Fig. 10. — Fog, or visible water vapor

Why is the fog in the valley and not on the hilltops?

unite with limewater to form a fine white powder which at first makes the limewater milky, the presence of this gas in ordinary air is easily demonstrated by allowing a dish of clear limewater to stand overnight. On examining this limewater, we notice fine white particles at the bottom of the dish. This proves that air contains carbon dioxid. Another method of showing that this is true is the following:

To prove that carbon dioxid is present in air. Laboratory demonstration.

By means of a bicycle pump force air for at least five minutes through clear limewater that partly fills a tall bottle.

1. Describe the experiment, state the result, and give your conclusion.

2. Do you infer from this experiment that the percentage of carbon dioxid in a quart of air is large or small?

How may carbon dioxid be formed? Laboratory demonstration.

In order to answer this question it is necessary to secure a bottle of pure oxygen (Fig. 11).

This may be done by heating some of the solid substances that contain a large amount of oxygen A common substance that may be used is chlorate of potash. When bottles of oxygen have been obtained, proceed as follows: Hold some charcoal (which is nearly pure carbon) in a flame until it glows; move the cardboard aside sufficiently to thrust the glowing carbon into the bottle of oxygen.