Gornell University Library Ithaca, New York i il on iii ii 4) Cornell University Library The original of this book is in the Cornell University Library. There are no known copyright restrictions in the United States on the use of the text. http://www.archive.org/details/cu31924031721420 ELEMENTARY BIOLOG) ANIMAL AND HUMAN THE MACMILLAN COMPANY NEW YORK + BOSTON - CHICAGO DALLAS + SAN FRANCISCO MACMILLAN & CO., Limirep LONDON - BOMBAY + CALCUTTA MELBOURNE THE MACMILLAN CO. OF CANADA, Lrp, TORONTO YELLOW-BILLED CUCKOOS EATING TENT CATERPILLARS Photographed from exhibit in Brooklyn Museum of Arts and Sciences, by A. E. Rueff. ELEMENTARY BIOLOGY ANIMAL AND HUMAN BY JAMES EDWARD PEABODY, A.M. HEAD OF THE DEPARTMENT OF BIOLOGY, MORRIS HIGH SCHOOL BRONX, NEW YORK CITY, AUTHOR OF “STUDIES IN PHYSI- OLOGY’? AND ‘‘ LABORATORY EXERCISES IN ANATOMY AND PHYSIOLOGY”? AND ARTHUR ELLSWORTH HUNT, Pu.B. HEAD OF THE DEPARTMENT OF BIOLOGY, MANUAL TRAINING HIGH SCHOOL, BROOKLYN, NEW YORK CITY ‘The wild life of today is not wholly ours to dispose of as we please. It has been given to us in trust. re must account for it to those who come after us and audit our records.’’ — Hornavay. New Work THE MACMILLAN COMPANY 1912 All rights reserved Copyrricat, 1912, By THE MACMILLAN COMPANY. Set up and electrotyped. Published November, 1912. TO THE MEMORY OF MARTHA FREEMAN GODDARD WHOSE DEVOTED INSTRUCTION IN BIOLOGY IS A LASTING INFLUENCE FOR GOOD IN THE LIVES OF HUNDREDS OF BOYS AND GIRLS AND WHOSE RARE SKILL IN LEADERSHIP IS AN INSPIRATION TO EVERY TEACHER WHO KNEW HER THIS BOOK IS DEDICATED BY THE AUTHORS PREFACE In the Preface to ‘‘ Plant Biology ”’ we discussed the general point of view that we believed should be emphasized in a course in elementary biology for students of high school age. We there stated that in our judgment the primary emphasis in the whole course should be placed on the many relations of biology to human welfare. Many. of the experiments in that volume, especially those relating to the chemical com- position of lifeless and living things, the tests for the food substances, and the principles of osmosis and of respiration, apply equally well in the discussion of animal and human biology. The method of presentation in “‘ Animal Biology ”’ is some- what different from that employed in ‘ Plant Biology,” for the reason that several widely different types of animals are studied. Limitations of time compel a rigid and somewhat narrow selection of groups for intensive study, and only those functions of each animal are considered which have some relation to human biology, or which have a broad, economic bearing. Thus insects are discussed largely because of their injurious or beneficial effects upon mankind ; birds and fishes, because of their economic importance, and because of the great need for their conservation; and one-celled animals because of the light they throw on cellular processes. Certain other somewhat less important topics are considered inci- dentally ; for example, protective resemblance and metamor- phosis among insects, and the striking adaptations of structure to function in the bills, feet, and feathers of birds. The animals suggested for additional study, if time per- vu viii PREFACE mits, are representative mammals, reptiles, amphibia, arthro- pods, molluscs, worms, and ccelenterates. In many classes there are students who can work faster than the others, or who are interested in pursuing further their biological stud- ies. Such students may be directed in carrying on some of these studies either in class or outside of school hours. In any case, students are likely to acquire considerable infor- mation by reading these textbook descriptions and studying the illustrations. All the work of the year should lead up to and culminate in human biology. Here, too, however, many important top- ics must be treated only superficially, or altogether omitted, on account of lack of time. The authors believe that in this, the most important part of the course, practical hygiene should be taught as effectively as possible, and that the necessity for good food, pure air, varied exercise, and suffi- cient sleep should be continually emphasized. If boys and girls can be led to conform their daily habits to the princi- ples of healthy living, the course in biology will have its highest justification. In the treatment of Stimulants and Narcotics, the authors have tried to state in simple language the conclusions of experts regarding the effect of tobacco and alcohol, and to present the strongest scientific arguments against the use of these substances which are so injurious to growing youths. In our judgment there are few, if any, biological topics that are more important in their practical bearing than is that of bacteria. As commonly studied, the disease-pro- ducing effects of these organisms are emphasized so much that boys and girls do not appreciate that all the work of the higher organisms depends ultimately upon the activity of these low forms of plant life. In order to bring out this aspect of the work of bacteria, we have called special atten- PREFACE ix tion to the structure, physiology, and economic benefit of these organisms. But since so much may be done to prevent disease, we have also considered with some degree of thor- oughness the disease-producing effects of several of the pathogenic forms. No study of human biology should be allowed to leave in the mind of the student the idea that he is merely a chemical engine adapted only for the generation of a certain amount of physical energy. The primary object of all secondary cducation should be the development of character and effi- ciency, and the true teacher ought to find opportunity again and again to touch the individual life of the young student. Especially should this be true in the study of biology. Growing boys and girls ought to come to feel, as they have never felt, that they have in their keeping a most complex and wonderful piece of living machinery which can be easily put out of order or even wrecked. But, on the other hand, they should see that if the bodily machine is well cared for, it is capable of splendid work which may help to increase the sum total of human efficiency and happiness. In the preparation of this volume the authors have re- ceived a great many. suggestions from the teachers in their own departments and those in other schools. We have been especially fortunate in securing the assistance of experts who have read much of the manuscript and many of the proof sheets. Dr. E. P. Felt, New York State Entomologist, Mr. E. R. Root, author of ‘A. B. C. of Bee Culture,” and Professor Glenn W. Herrick of Cornell University, have given us valuable criticism of the chapter on Insects. Dr. W. T. Hornaday, Director of the New York Zodlogical Park, has read the chapters on Birds and Fishes. To Mr. J. M. John- son, Head of Department of Biology of the Bushwick High School, we are also indebted for suggestions relating to Birds. x PREFACE Much of the manuscript of the chapter on Foods received the careful criticism of the late Professor W. O. Atwater. Dr. William H. Park, Director of the Laboratories of the New York Board of Health, and Dr. Thomas Spees Car- rington, Secretary of the National Association for the Study and Prevention of Tuberculosis, have given invaluable assistance in the preparation of the chapter on microérgan- isms. A considerable part of the ‘‘ Human Biology ” was crit- ically read by Dr. F. C. Waite of the Western Reserve Medical School, by Mr. Harold E. Foster of the English Department of the Morris High School, and by the late Miss Martha F. Goddard of the Morris High School, to whose memory these volumes are dedicated. We wish, also, to express our hearty appreciation of the generous permission of Henry Holt & Co. to use some of the material published in Peabody’s ‘‘ Labora- tory Exercises in Anatomy and Physiology.” : Miss Mabelle Baker, a student in the Morris High School, has contributed the drawings on which her initials appear. To Mr. E. R. Sanborn of the New York Zodlogical Park, and to Mr. A. E. Rueff of the Brooklyn Museum, we are indebted for their skillful photography. The American Museum of Natural History, the Brooklyn Museum, the National Audubon Society, Doubleday, Page & Co., Dodd, Mead & Co., Kny-Scheerer Co., Dr. C. F. Hodge of Clark University, Dr. H. A. Kelly of Johns Hopkins Medical School, Mr. C. W. Beebe of New York Zodlogical Park, and others, have permitted us to make use of illustrative material. Cost prices for the items on the list of laboratory appa- ratus and equipment were kindly furnished us by Bausch & Lomb, Kny-Scheerer, and O. T. Louis ; from these prices the estimates on pp. 173 to 177 were prepared. LEP October 31, 1912. A. E. H. PREFACE CHAPTER I. Insects II. III. IV. VL I. Ii. II. IV. Il. III. Iv. Vv. VI. CONTENTS ANIMAL BIOLOGY Butterflies and Moths ‘ Grasshoppers and their Relatives . Bees and their Relatives Mosquitoes and Flies (Optional.) Additional Topics on ‘ ineeets : Characteristics of Structure . Reproduction and Life History Methods of Classification Importance of Birds to Man . Decrease in Bird Life Conservation of Birds FroGs AND THEIR RELATIVES . FIsHEs. I. II. Ill. IV. Vv. Characteristics of Structure . Adaptations for Nutritive Functions Reproduction and Life History Importance of Fishes to Man Conservation of Food Fishes. CRAYFISHES AND THEIR RELATIVES. PARAMECIUM AND ITS RELATIVES I. II. III. IV. Structure and Functions of Paramecium Structure and Functions of Amoeba Cellular Structure of Higher Animals . Importance of Protozoa to Man xi 101 120 120 125 137 141 147 151 164 164 170 172 173 xii CONTENTS OHAPTER PAGE VII. (Oprionau.) ADDITIONAL ANIMAL STUDIES : . 175 I. Porifera : é ‘ : 3 , ‘ . 175 II. Ceelenterata . : : 7 F : F . 176 III. Annelida. , ‘ F A ‘ F . 179 IV. Mollusca ‘i : : 2 Fi 3 . 181 V. Reptiles ‘ . , s . . , . 185 VI. Mammals. , ¥ - P F . 187 VII. Classification of. Acivmals ‘i i ‘ . 190 HUMAN BIOLOGY I. GENERAL STRUCTURE OF THE Human Bopy A 3 1 II. MicroérGAaNnisms AND THEIR RELATION To Human WELFARE . 5 - F . 10 I. Structure and Wacetions of Hitec z - - 10 II. Occurrence of Bacteria . , , i . 14 III. Bacteria as the Friends of Man . - : - 20 IV. Bacteria as the Foes of Man - ‘ : . 28 III. Foops anp THeir Usss . ‘ . 44 I. Food Substances found in the isda Body . 44 II. The Necessity for Foods: . : ; j - 45 III. The Composition of Foods . 3 é : - 46 IV. Uses of the Food Substances , 3 : . 650 V. Cooking of Foods. ‘ : é ‘ - + 652 VI. Food Economy . . : si : . . 56 VII. Daily Diet . : , , 3 ‘ ; - 60 IV. Srimutants anp Narcotics . F : ; . . 64 I. Definitions . 3 - - : ‘ 3 . 64 II. Beverages . ; ; : ; : : . 65 TII. Tobacco 7 ‘ ‘ . 75 IV. Drugs and Patent ‘Medicines ; : ‘i - 78 V. Digestion AND ABSORPTION OF THE NUTRIENTS. & 188 2 I. General Survey of the Digestive System . . 82 OHAPTER CONTENTS The Mouth Cavity and its Functions (Optional.) The Throat canes and Gullet and their Functions The Stomach and its owehens ‘ The Small Intestine and its Functions ° (Optional.) The Large Intestine and its Func- tions . : Absorption non the Ainkeittany Gana ; (Optional.) The Liver and its Functions Hygiene of Digestion VI. CrecuLaTion oF THE NUTRIENTS . I. II. Ii. IV. Vv. VI. Composition of the Blood Circulation and its Organs The Heart The Blood Vessels Circulation of the Blood . Hygiene of the Circulation VII. RespiraTION AND THE PRODUCTION OF ENERGY IN Man Necessity for Respiration . , Adaptations for securing Oxygen andl tor ex- creting Carbon Dioxid . The Process of Breathing Hygiene of the Respiratory evans, VII. (Oprionan.) AppiTionaL Topics In HuMAN BioLoey I. II. IIT. IV. V. VI. The Skin . The Skeleton The Muscles The Nervous System The Eyes . ‘ The Ears .. IX. (Optronat.) GReEaT BIOLOGISTS . xiii PAGE 84 92 93 97 98 98 101 102 107 107 108 109 112 117 119 122 122 124 129 132 139 139 144 150 154 162 166 168 xiv CONTENTS APPENDIX. : , A . I. Laboratory Ranininont II. Order of Topics III. Biology Notebooks : IV. Review Topics in Animal Bioloay) V. Review Topics in Human Biology 5 . VI. List of Suggested Books of Reference in Biology PAGE 171 171 178 181 188 198 198 ELEMENTARY BIOLOGY ANIMAL AND HUMAN ANIMAL BIOLOGY CHAPTER I INSECTS I. Butrerriies anp Morus 1. Insect net. — Since most butterflies and moths are more or less injurious, at least in their caterpillar stage, boys and girls should be taught that they are benefiting their community by catching and killing these insects in a painless manner. For this purpose an insect net and a poison bottle are necessary. An insect net may be made by securing a yard of galvanized iron wire (No. 3), bending it in the form of a ring (thus {?), and inserting the two ends of the wire in one end of a light wooden rod about three feet long. To the wire ring should be sewed a bag about two feet deep made of cheesecloth or bobinet (Fig. 1). To catch a butterfly or other insect, wait until it alights, then quickly place over it the opening of the net, holding up the closed end of the net till the insect flies to the top. Now place beneath the insect the open mouth of a poison bottle prepared as follows, and after the insect is in the bottle quickly replace the cover. 2. Poison bottle. — Secure a pint fruit jar or a wide-mouthed bottle fitted with a cover. Into the bottom put a spoonful of more or less pulverized potassium cyanide. Thoroughly mix some plaster of Paris in water and thus make a thin paste. Carefully pour the liquid into the jar until it forms a layer about an inch thick. When this hardens, it covers and holds the cyanide in place, but it is porous enough to allow fumes to escape, which kill most insects in the closed space ina few moments. The bottles are per- fectly safe in the hands of pupils. Care should be taken, however, not to handle the cyanide or to breathe in the fumes. The bottle B 1 2 ANIMAL BIOLOGY tend the legs and _ proboscis, then put the body of the insect between the two books, thrusting the tip of the pin into the board beneath. Spread out the fore wings on the book covers so that their hind margins are at right angles to the thorax, pull the hind wings outward into their natural position when at rest, and hold the two pairs in place with pieces of glass till the specimen has dried. Butterfly spreading boards may be bought or made (Fig. 3). Fic. 1.— Insect net. should be kept tightly closed when not in use, and should be distinctly labeled “ Poison Bottle” (Fig. 2). If the bottle is broken, the pieces of glass and all the contents should be buried in the earth. 3. Preparation of butterflies for study or for collections. — For laboratory study it is desirable to use the largest butter- flies obtainable. on to much better advantage if there is at least one mounted specimen for each two pupils. pared with the wings fully extended, with the legs spread out as in walking, and with the proboscis partly uncoiled. To get the material in this shape place two books about half an inch apart on a soft board; run an insect pin through the thorax of a freshly killed insect, ex- The work will be carried These should be pre- Fic. 2.— Poison bottle for killing insects. INSECTS 3 Dry specimens may be relaxed by placing a quantity of sand or crumpled paper in a battery jar or other wide-mouthed receptacle that can be tightly covered. Wet the sand or paper thoroughly and then sprinkle over it a little dry sand or cover with blotting- paper. Put in the dried butter- ‘flies about twenty-four hours before they are to be spread, and cover the dish. If the relaxing jar - is kept in a warm place, the process will be has- tened, but care should be taken not to leave the insects in the moist chamber long enough for mold to grow upon them. It is of course better to mount the butterflies as soon as they are killed. Fig. 3. — Insect spreading board. 4. Insect boxes. — A box for displaying a butterfly for class study may be made as described below by any fourteen-year-old boy; these cases will preserve the insects from year to year, thus saving labor as well as insuring good material that pupils can examine from both sides. The boxes may likewise be used as cages for the study of the activities of live grasshoppers, caterpillars, or other insects. After butterflies have been studied they should be transferred to an insect case or other moth-proof box, a piece of cotton soaked in carbon bisulphide should be inserted, and the box kept tightly closed till the butterflies are again needed. “‘ Chiclet ” boxes, since they have glass covers, may be used for storing and dis- playing the insect collections that may be made by pupils. A layer of absorbent cotton over the bottom of the box makes a good back- ground (Fig. 4). To make the insect boxes, secure from a mill or a local carpenter strips of wood 23 inches wide and 3 inch thick, with grooves } inch wide and } inch deep, cut a quarter of an inch from the two margins of one side. About 18 inches will be required for each box. For the sides saw up two pieces each 53 inches long, and for the ends the ANIMAL BIOLOGY ‘uroque 8 “a q Aq poydeisojyoyg (YIB_ [BOIBO[QOT “XN ‘O*— Ao1vayog-AUY Aq poredeig) “‘MWOTJOITJOD JOVSUT — “fF “OI A INSECTS 5 pieces should be 3? inches in length. One of the ends should be planed down to a width of 1? inches (the distance between the grooves). Nail the four pieces together and insert in the grooves on each side a cleaned 4 X 5 picture negative, the gelatin of which may be easily removed with hot water. Glue to the center of one of the glasses a piece of cork to hold the insect pin, and fasten a piece of wood to the narrow end by a wire nail, which will prevent the glasses from slipping out but will still allow the box to be opened. The boxes are made more attractive if they are treated with dark oak jap-a-lac or stain (Fig. 5). Fia. 5. — Insect box. 6. Experiments with living butterflies. — Before trying the feed- ing experiments, the butterflies should be kept for at least twenty- four hours without food. After a butterfly has fed, it should be placed by itself, since the same insect may be unwilling to eat a second time. Have as many students at a time see the feeding as can well do so; this will save time, and fewer butterflies will be needed. The mourning cloak, monarch, and violet tip butterflies are satisfactory for this experiment. Place the butterfly on a stick or other rough object, and put the tiny drop of honey near it. This may be done in a cage, or under a glass jar, or in the open laboratory. 6 ANIMAL BIOLOGY In the latter case the windows should, of course, be closed, and this should also be done while watching the insect fly. The flying and feeding experiments with insects make excellent home work if the pupils can readily obtain the live material. Children in New York City have caught and kept butterflies for several months, feeding them twice or three times a week. 6. Study of a butterfly. — Laboratory study. A. Regions and appendages. Examine a butterfly and distinguish (1) the front or anterior (Latin, ante = before) region called the head; (2) the middle region called the thorax; and (3) the hind or posterior (Latin, post = behind) region known as the abdomen. 1. Which region is the smallest? Which is the widest? Which region is longest? 2.. To which region are the appendages (legs and wings) attached? 3. Which region seems to have no appendages? B. Organs of the head; feeding. 1. Observe two long, slender appendages attached to the head; they are called antenne (singular, antenna). State the position of the antenne on the head. Describe the shape of an antenna, stat- ing where it is the thickest (7.e. at the proximal end, which is next the head, or at the distal end, which is farthest from its attachment to the head). 2. Near the base or proximal end of the antennz find the large eyes. State their position on the head, their shape, and their size (as compared with the rest of the head). 8. Demonstration. Take a living or a relaxed specimen of the butterfly, and with the help of a dissecting needle find a coiled structure on the lower or ven- tral surface of the head. It is the sucking tube or proboscis. Gently uncoil it and describe this feed- ing organ as to position and appearance. 4, 5. INSECTS 7 (Optional demonstration or home work.) Place a tiny drop of honey or molasses diluted with water near a butterfly. If the insect does not seem to realize the presence of the sweet substance, touch the pro- boscis with the needle, or if necessary put the needle into the coil of the proboscis, and gently unroll it. a. Describe what you have done to get the animal to eat. . Describe the movements of the proboscis. . What reason do you find for supposing that the butter- fly is feeding? d. What reason have you for thinking that the proboscis must be hollow? (Optional.) Between the two antenne, and projecting upward in the anterior region of the head, are two slen- der structures covered with hair; they are the labial palps. In some butterflies the labial palps are incon- spicuous. If they show in your specimen, describe them as to their position and appearance. an Organs of the thorax; locomotion. 1. 2. 3. How many pairs of wings has the butterfly? Describe a wing as to comparative length, breadth, and thickness. Hold a butterfly between your eyes and the light, and study carefully the course of the veins in the two wings on one side. In what region of the wings do the main veins meet? Bend the veins and the connecting membrane in a wing that is given you. a. Which is the more rigid? b. What, then, is one use of the veins? Take a small piece of the wing of a butterfly that is given you and rub the surface with your finger tip. a. Describe what you have done, and state how the substance on your finger compares in color with the color of the part of the wing before it was rubbed. 8 ANIMAL BIOLOGY b. (Optional.) Shake some of the powder from a wing upon a glass slide and examine it with a low power of the compound microscope. The bodies that you see are called scales. At one end of each scale you should find a tiny stem by which the scale was attached to the wing, and at the other end usually one or more notches. Describe the shape of the scales that you are studying, and make a sketch of one of them much enlarged. 6. (Optional home work.) Watch a butterfly in the field as it moves the wings in the act of flying. a. Will the downward stroke of the wings tend to lower or to raise the body? ‘ b. What effect will the upward stroke of the wings tend to have? c. In which of these two directions, therefore, must the butterfly strike the harder and more quickly in order to raise the body in the air? d. Since the weight of the body tends to bring the animal to the ground, in which direction must the insect strike with the greater force in order to keep itself at a given level in the air? 7. Some butterflies have a tiny pair of front legs that are usually folded against the thorax; so that you need to look very carefully before deciding as to the number of legs present. . How many pairs of legs has this insect? Are the legs long and slender or short and thick? Is each leg all one piece or is it jointed as in the human body? d. Examine the lower end of a leg and state how the foot is adapted for clinging to flowers. D. Make a drawing, natural size, of the upper or dorsal surface of a butterfly. Label antenne, eyes, proboscis, head, thorax, abdomen, wings, prin- cipal veins of one wing. 9 8 INSECTS 9 7. General characteristics of butterflies. — All butter- flies, as we shall see later, are constructed on much the same general plan as that of other insects; 7.e. their bodies are divided into three re- gions, head, thorax, and abdomen; on the : -.. head are two antenne ere and a pair of large “fe tr minwoea eyes; onthe thorax are — ‘ef. two pairs of wings and three pairs of jointed legs; and the abdomen is composed of a num- ber of parts called rings or segments (Fig. 6). 8. Wings and their scales. — While this general plan of struc- ture is common to all insects, there are cer-. tain marked peculiar- ities that enable one readily to recognize a butterfly. For instance, al- though other insects Adult Stage. havetwo pairs of wings, Fic. 6.— Life history of monarch butter- no others have these aye. (aisedy organs so beautifully colored and relatively large. This color of the wings is due (we proved in 6, C. 5) to tiny bodies called scales. If the wing of a butterfly is rubbed, the color comes off and the wing at that point loses its color. To 10 ANIMAL BIOLOGY the unaided eye this colored substance from the wing ap- pears to have no definite form; in fact, it looks like the pollen from flowers. An examination with the compound microscope, however, shows that each of these tiny bodies has a definite shape (Fig. 7). Each scale has at one end a tiny stem, but in other re- spects they vary considerably in form. The scales are attached in the follow- ing manner. In the membrane of the wing are openings into which fit the stems of the scales. The latter are Fie. 7.— Scales from arranged in rows and overlap some- aca ade lie thing like the shingles on a roof (Fig. 8). In spite of this arrangement it is evident that the scales are not firmly attached, since the slightest touch is sufficient to dislodge many of them. Rough handling was not apparently planned for in the con- struction of these insects. The pres- ence of these scales on the wings of butterflies and of their near relatives, the moths, is so characteristic that these insects have been called the Lepidoptera (Greek, lépido = scale + ptéra = wings). Not only are scales found on the wings but, in the shape : . of hairs, they form a fuzzy growth SRE eee aad over the surface of the whole body. scales. (Coleman.) 9. Proboscis. — Another marked characteristic of butter- flies and moths is the sucking tube, or proboscis. While the proboscis seems to be a single structure, in reality it is com- posed of two slender appendages, each having a groove on INSECTS 11 its inner surface; so that, when the two parts are brought together, they form a tube through which the butterfly sucks nectar from flowers. When the proboscis is not in use, the butter- fly rolls it into a tight coil under- neath the head (Fig. 9). 10. Legs. — The legs of a but- 77 terfly are not very strong, since they are relatively so long and slender. This is perhaps the reason why these insects seldom use them Fic. 9.— Head of butterfly. for walking. They are, however, Coleman.) very useful in clinging to flowers. The two curved claws on the tip of each foot show clearly the means by which the animals are able to hold on to the plants on which they usually alight. 11. Reproduction and life history of butterflies. — As in the reproduction of plants, the development of the butterfly begins with a special cell known as an egg-cell. These egg- cells are formed in the body of the female insect. When these egg-cells have been fertilized by sperm-cells from the male butterfly, which correspond to sperm-cells of the pollen grains (P.B.1, 91), the eggs are deposited on the under side of the leaves of plants on which the young can feed (Fig. 6). These egg-cells divide and subdivide, till at last a many-celled organism is developed that is commonly called a “worm,” but that is more correctly known as a caterpillar (Fig. 6). The tiny caterpillar emerges from the covering of the egg and begins to feed upon the leaf. As it feeds it grows, and 1P.B. = ‘‘ Elementary Plant Biology,” by the authors of this book. 12 ANIMAL BIOLOGY from time to time sheds or molés the more or less hardened skin that covers the whole insect: At last, after several molts, the caterpillar reaches its full size and then stops eating. At no time in the growth of the caterpillar would one be likely to mistake it for a butterfly (Fig. 6). It has no wings, no antenne, and instead of a proboscis one finds a pair of strong jaws with which it eats leaves. The distinc- tion between thorax and abdomen is not at all clear, and at first sight it seems to have more legs than a butterfly. The three front legs are really jointed, but they are so short and thick that there seems to be no resemblance between them and those of a butterfly. The other pairs of legs, varying in number, are not jointed structures, and hence are not really legs at all. The mature caterpillar now attaches itself to some object and, after molting once more, usually assumes quite a different shape from that of the caterpillar, and forms about itself a hardened skin within which a marvellous transforma- tion occurs (Fig. 6). The long, coiled tube takes the place of the jaws as a feeding organ, and long, slender, knobbed antenne appear on the head; two pairs of beautifully colored wings develop on the thorax, as well as the three pairs of slender, jointed legs’; and at last the fully developed butterfly breaks through the covering that held it and flies away. It is evident, then, that a butterfly passes through several fairly distinct stages. First we may distinguish the egg stage, then the caterpillar or larva stage, which is followed by the transformation stage in which it is called a pupa. The pupa of a butterfly is often called a chrysalis (Greek, chrisos = gold) on account of the golden spots of color on many pupa cases. Lastly we have the fully developed or adult insect that emerges from the pupa stage. INSECTS 13 12. Distinguishing characteristics of moths. — The moths and butterflies belong to the same order of insects; that is, the scaly winged insects. But there are some characteristics in which these two kinds of insects differ. For instance, moths when at rest fold the wings horizontally (Fig. 11), while butterflies fold them verti- cally, that is, erect (Fig. 10). The wings, too, of moths are not usually as brilliantly colored. Most moths fly at night, while butterflies are day-flyers. The body of moths is usually relatively broader than that of butterflies. Moth antenne are of various shapes, often like a feather, but never knobbed. In general, the life history of moths is very much the same as that of butterflies, but the larve of many moths spin a more or less silky mass of threads about themselves, as is the case with the silk- worm caterpillar (Fig. 16), and this outside covering of the pupa stage is known as the cocoon. 13. Economic importance of butterflies and moths. — The larve of both butterflies and moths are voracious feeders, as any one knows who has had any experience with caterpillars. In fact, they may be called animated feeding machines, since the animal must not only provide for its own growth, but must also store up enough food to form the new parts such as the wings and the legs. Not all larve of butter- flies and moths are considered harmful, however, since some of them are not prolific enough to have any serious effect upon vegetation, which is the source of food of most caterpillars. This is true of many of the butterfly larve and of some moth larve. Then, too, some of the larve feed on plants that are not useful to man. This is true of the larva of the monarch butterfly (Fig. 6), which feeds upon leaves of the milkweed. The adult butterflies and moths of course are not capable of doing any harm since, when they eat anything at all, they most commonly suck the nectar ‘of flowers. When the flowers are visited in this way, 14 ANIMAL BIOLOGY they are very likely to be cross-pollinated and thus are bene- fited instead of injured. But in general the moths and butterflies play but little part in the very important process of cross-pollination of flowers, most of this work being done, as we shall soon learn, by the bees. The following are a few of the injurious forms of butterfly and moth larve. 14. Cabbage butterfly. — This is one of the few forms of butter- fly larvee that are of sufficient economic importance to be worthy of mention. Any one who has been near a cabbage patch will remember to have seen many rather small white but- terflies (Fig. 10) hovering about among the cabbages. These are the cabbage but- terflies depositing their eggs on the under side of the leaves. The small green caterpillars that develop from the eggs very soon show what they can do in the way of eating. The ragged ap- Fic. 10.— Life history of cabbage butter- pearance of the young leaves fly. (Coleman.) is a warning to the gardener to “get busy” if he desires a crop. The caterpillars do most harm when the cabbages are young, since these plants may be so injured as to be unable to form heads. The caterpillars are often killed by sprinkling with a mixture of Paris green and arsenate of lead in water (47). This mixture should not be used, however, after the heads begin to form, on account of the possibility of the poison collecting between the leaves of the head, with consequent danger to the consumer. 15. Tussock moth. — The caterpillars of the tussock moth attack our shade trees. Where they are unchecked, they will practically INSECTS 15 strip the trees of their leaves. The female moth is wingless (Fig. 11). When she emerges from her cocoon, she lays a mass of eggs upon the Fig. 11.— Life history of tussock moth. (Osborn.) outer surface of the cocoon and secretes about them a white foamy mass which hardens (Fig. 11). If this occurs in the autumn, the eggs 16 ANIMAL BIOLOGY remain during the winter, and the following spring hatch out. The young caterpillars attack the leaves of the tree on which they have hatched out, or if the cocoon was placed elsewhere, they crawl up the nearest tree and start business at once. They are great travel- ers, and this is the way they spread through a neighborhood, since, as already mentioned, the female cannot fly. To capture these insects one may place a band of cotton batting around the trunk of each of the trees one wishes to pro- tect. The larve do not usually crawl over this but will, if mature, pro- ceed to pupate under- neath the band. All pup and egg masses should be collected (Fig. 12) and burned. This is about as much as the individual can do. Where a spraying appa- ratus is available the trees should be sprayed with lead arsenate, thus killing all the caterpil- Fie. 12.— Morris High School boys removing : : = 63,020 eggs of tussock moth from four trees lars. This caterpillar is on school grounds. Work directed by Paul rather handsom a B.Mann. (Photographed by Lewis Enowitz.) © as cat erpillars go, having a bright red head and a series of yellow tufts of hair on the dorsal part of the body (Fig. 11). 16. Gypsy moth and brown tail moth. — The gypsy moth (Fig. 13) was brought into Massachusetts from Europe in 1869 in con- nection with scientific experiments. Some of these specimens acci- INSECTS 17 Lymantria dispar Food plant Femak | Apple-tree Fie. 13.— Life history of gypsy moth. (Prepared by Kny-Scheerer Co. Photographed by E. R. Sanborn, N. Y. Zodélogical Park.) dentally escaped and gradually increased until the damage to fruit, forest, and shade trees caused by the larve was so evident that property owners had to call upon the state to aid in their extermina- ce 18 ANIMAL BIOLOGY tion. Nearly one million dollars was expended during a period of ten years. At the end of this time the number of the insects was so reduced that it was impossible to convince taxpayers of the neces- sity for further appropriations to complete the extermination. ‘Since then the gypsy moths have spread over the whole state of Massachusetts and into the adjoining states. The larve of another moth, the brown tail, has likewise caused great damage in the New England states. The New York State Department of Education is sending out colored pictures of the life history of both of these insects with the following statement regard- ing them. ‘‘ Warning— Take Notice. There is grave danger of both of these dangerous pests being brought into New York State. They have destroyed thousands of trees in Massachusetts, and they will do the same in New York unless checked. All are hereby urged to become familiar with the general appearance and work of these two insects, and to report anything suspicious to the State Entomologist, Albany, N.Y., sending specimens if possible. Abundant hairy caterpillars an inch to two inches long on or in the vicinity of defoliated trees should lead to investiga- tion.” 17. Codling moth.— Every one has eaten into apples that have been in- jured by the “ apple worm,” which is the larva of the codling moth (Fig. 14). The Fig. 14.— Life history of codling moth. 4 (U.S. Dept. of Agriculture.) damage to the fruit crop from this insect in New York State alone is estimated at three: million dollars each year. According to Professor Hodge (‘‘ Nature Study and Life ”) the cod- INSECTS 19 ling moth “ was early imported from Europe and is now at home wherever fruit is cultivated in this country and Canada, causing a loss of from 25 to 75 per cent of the apple crop, as well as that of many other fruits. In the heavy bearing years the wormy apples fall off and are discarded, but the great number of apples serves to rear enormous numbers of the worms, and, according to my observations and experience, in the off years, when apples would be valuable, the worms take the whole crop. “The larve change to pups in May, emerge as moths in late May or June, and lay their eggs for the first brood in June. The larve generally crawl into the calyx cup of the young apples and eat their way to the core, complete their growth in about three weeks, commonly eat their way out through the side of the apple, and either spin to the ground and crawl to the trunk of the tree or crawl down the branches and make their cocoons under the bark again. This occurs with the greater number early in July. This habit affords one of the most vulnerable points of attack. To trap practically all the codling moths in an orchard it is only necessary to scrape all loose bark off from the trees and fasten around the trunks a band of burlap or heavy paper. Remove the bands and collect all larvee once a week during July.” The practice of most commercial grow- ers at the present time, however, is to depend very largely or entirely on spraying with a poison (e.g. arsenate of lead, 47). One applica- tion, even, a week or ten days after the blossoms fall, if thorough, will frequently give 95 per cent to 98 per cent of sound fruit. 18. Clothes moths. — “ The little buff-colored clothes moths (Fig. 15) sometimes seen flitting about rooms, attracted to lamps at night, or dislodged from infested garments or portiéres, are them- selves harmless enough, for their mouth parts are rudimentary, and no food whatever is taken in the winged state. The destruction occasioned by these pests is, therefore, limited entirely to the feed- ing or larval stage. The killing of the moths by the aggrieved 1 The authors are indebted to Mr. E. P. Felt, state entomologist of New York, for this and several other suggestions relating to insects. 20 ANIMAL BIOLOGY housekeeper, while usually based on the wrong inference. that they are actually engaged in eating her woolens, is, nevertheless, a most valuable proceeding, because it checks, in so much, the multi- plication of the species which is the sole duty of the adult insect. “There is no easy method of preventing the damage done by clothes moths, and to maintain the integrity of woolens or other materials which they are likely to attack demands constant vigi- lance, with frequent inspection and treatment. In general, they are liable to’ affect injuriously only articles which are put away and left undisturbed for some little time... . Agitation, such as beating and shaking, or brushing, and exposure to air and F sunlight, are old remedies Fic. 15.— Life history of clothes moth. and still among the best at (U.S. Dept. of Agriculture.) command. Various repel- lants, such as tobacco, cam- phor, naphthalene cones or balls, and cedar chips or sprigs, have a certain value if the garments are not already stocked with eggs or larve. ... Furs and such garments may be stored in boxes or trunks which have been lined with the heavy tar paper used in buildings. New papering should be given to such receptacles every year or two.” 1 19. Silkworms. — One species of moth, the silkworm (Fig. 16), is of great economic importance to man. The larva of this insect feeds upon the leaves of the mulberry tree, and after reaching matur- ity it spins a cocoon, requiring about three days for its completion. The silk is obtained by heating the cocoon in ovens to kill the pupa, and then by reeling off the silk and spinning it into threads. ‘“ For many hundreds of years the cultivation of the silkworm was con- fined to Asiatic countries. It seems to have been an industry in 1 Circular No. 36, Second Series, United States Department of Agriculture. INSECTS 21 Bombyx mori Sik uroathy Food plant. Mulberry leayes Mate Female Fic. 16.— Life history of silkworm moth. (Prepared by Kny-Scheerer Co. Photographed by E. R. Sanborn, N. Y. Zodlogical Park.) China as early as 2600 B.c., and was not introduced into Europe until 530 a.p. After the latter date the culture rapidly increased, and soon became prominent in Turkey, Italy, and Greece, and has 22 ANIMAL BIOLOGY held its own in those countries, becoming of great importance in Italy. ... Japan to-day produces a very considerable proportion of the world’s supply of raw silk. Thus of the $41,000,000 spent by the United States for raw silk in 1902, more than $20,000,000 went to Japan.”1 Many attempts have been made to introduce this industry into the United States, but the experiments thus far made have been rather unsuccessful. II. GRASSHOPPERS AND THEIR RELATIVES 20. Study of the grasshopper. — Itaboratory study. A. Regions and appendages. — Examine a grasshopper and distinguish the three regions of the body proper: (1) the front or anterior region called the head; (2) the middle region called the thorax; and (3) the hind or posterior region known as the ab- domen. (The anterior region of the thorax is covered by a cdpe or collar.) 1. Which region is the smallest? Which is the widest? Which region is the longest? 2. Which region has legs and wings attached to it? 3. Which region is made up of a number of similar rings or segments ? B. Organs of the head; feeding. 1. Notice two long, slender feelers on the head. They are known as antenne (singular, antenna). State the position of the antenne on the head and de- scribe their shape. 2. Describe the shape and position of the large eyes. — their relative size compared to that of the ead. 3. (Optional.) Cut off with a sharp knife a thin slice from the outer surface of one of the large eyes. Remove all the soft, dark material from the inside. Place the 1 Bailey’s Cyclopedia of Agriculture, Vol. III, p. 640. INSECTS 23 cleaned piece on a glass slide and examine the outer (convex) surface with the low power of the compound microscope. Look for the boundary lines of many several-sided areas. Each of these areas is called a facet. Each facet is the covering of one of the parts of which the compound eye is composed. a. Describe the preparation of the slide for examination. b. Describe the shape of each of the facets, and make an out- line drawing of three of them, miueh enlarged, to show the way in which they fit together. . (Optional.) With the aid of a magnifier look for a tiny eye in the middle of the front part of the head. There is a similar eye between each compound eye and the an- tenna of the same side. These eyes are simple eyes. Describe the simple eyes as to location, number, and relative size. . Find the upper lip (labrum) on the lower anterior part of the head. Describe its location and shape. (Demonstration.) Raise the upper lip of a large grass- hopper and find the jaws or mandibles beneath it. With a dissecting needle gently pry the jaws a little way apart. Do the jaws move from side to side or up and down? . (Optional.) Find the lower lip on the under side of the head, ze. next to the thorax. It is divided vertically into two equal parts. Attached to either side are two tiny, jointed structures called labial palps. a. Describe the location of the lower lip (Jabium). b. Describe the position and appearance of the labial palps. . (Optional demonstration.) Between the jaws and the lower lip of a large specimen find a pair of appendages each of which is made up of three parts that are joined together at the base: (1) on the outside is a several- jointed feeler or maxillary palp; (2) next is a spoon- shaped body; and (3) a curved and sharp-pointed 24 ANIMAL BIOLOGY body. It will be necessary to pull sideways on the mouth parts to see this inner part. These three parts form one appendage called the mazilla (plural maxille), or helping jaws. When you have found these three parts of a maxilla, describe them. 9. (Demonstration ‘or home work.) Place several grass- hoppers in a cage or a glass jar with moistened leaves of clover, grass, .or lettuce. If these insects refuse to eat, try others till you find some that will eat. a. Describe the movements of the head and also the movements of the mouth parts while the grass- hopper is eating. b. Which mouth parts must do most of the biting of the leaf? Give reason. 10. (Optional.) Make a drawing, at least four times natural size (X 4) of the face view of a grasshopper. Label antenna, compound eye, simple eye, upper lip. C. Organs of the thorax; locomotion. 1. How many legs has a grasshopper? Which pair is the largest? 2. Make a sketch (X 4) to show the following parts of one of the hind legs: (1) a large segment nearest to the thorax, the thigh or femur; (2) the next segment to the femur, the tibia; (3) the part that rests on the ground when the insect walks, the foot or tarsus. Use a magnifier to see the several segments in the tarsus, the little claws at the tip end. and a little pad be- tween the claws. Label femur, tibia, segments of the tarsus, claws, pads. 3. (Optional.) Make a sketch (X 4) of one of the smaller legs to show the size and shape of the parts. Use the same labels as in the drawing of the hind leg. INSECTS 25 4. Get a grasshopper to climb up a stick or piece of grass. a. Tell what you have done and observed. b. How is the insect able to cling to the stick? 5. (Demonstration or home work.) Place a lively grass- hopper in a clear space on the floor or in a cage. Get it to jump enough times to determine the following points : — a. What is the position of the parts of the hind legs when the animal is ready to leap? b. What is the position of the parts of the hind leg the instant the insect lands? c. What does the grasshopper do to get ready for another jump? d. What movement throws the insect into the air? Is this movement made slowly or quickly? e. In what respects are the hind legs better fitted for jumping than are the two other pairs? What seems to be the use of the smaller pairs of legs when the insect lands on plants? 6. Move the outer wings sideways and forwards at right angles to the body so as to expose the under pair. Spread out or unfold the under wings. (It is an advantage to mount the specimens on cork and pin the wings in the position named above.) a. Which pair of wings is better fitted for flying? Why? b. How are the outer wings fitted to protect the under wings? c. (Optional.) Draw (X 2) the outline of a front wing and of a hind wing, and sketch in the principal veins. Label front wing, hind wing, veins. D. Organs of the abdomen; breathing. 1. You will observe that each of the rings or segments of the abdomen is composed of an upper or dorsal half and an under or ventral half. Make a sketch (x 4) of a side view of four or five seg- ments of the abdomen to show the structures mentioned above. 26 ANIMAL BIOLOGY 2. Secure an active grasshopper, put it in a live cage, and watch the movements of the upper and lower halves of the abdominal segments. De- scribe what you have observed. 3. In each segment, except those at the tip of the ab- domen, there are two breathing pores or spiracles, one on each side. With the aid of a magnifier : look for these breathing pores near the lower margin of the dorsal half of each segment. When you have found the spiracles in four or five segments, show them in your sketch (1, above), and label breathing pores or spiracles. 4. The spiracles lead into tiny elastic breathing tubes or trachee (singular trachea) which extend through- out all parts of the body of the insect even into the wings. The veins that you can see in the wings contain these minute tubes. Describe the trachez and state their extent and their connection with the spiracles (Fig. 17). 5. The trachee have an elastic material in their walls, so that when they have been compressed, they wil spring back to their former shape and size as soon as the pressure is removed. Describe, now, the structure of one of the air tubes, and state what action this struc- ture makes possible. 6. When the under or ventral oe of the abdomen moves up into the dorsal a. pawn a. Will the diameter of the abdomen be increased or decreased ? Fic. 17. — Air tubes (trachez) of an insect. INSECTS 27 b. Will the air tubes be made larger or smaller? Why? c. Will the air now rush into the air tubes or out of them? Why? 7. If the upper and lower halves of the abdomen now move apart — a. Will the diameter of the abdomen be increased or decreased ? b. How will this movement affect the size of the trachee? Why? c. Will the air now move into the trachee or out through the spiracles? Why? 21. Characteristics of grasshoppers. — After studying two or three insects, the student will see that they all re- semble the grasshopper (1) in having three regions of the body (head, thorax; and abdomen), (2) in possessing as appendages one pair of antenne, one pair of compound eyes, two pairs of wings, and three pairs of legs, and (3) in having an abdomen made up of a number of rings or segments. The most distinguishing character- istics of the grasshopper and its rela- tives are found in its mouth parts and wings. Grasshoppers have bit- ing mouth parts throughout their life. These consist of (1) an upper lip that is notched, (2) a pair of horny jaws, or mandibles, (3) a pair of rather complicated helping jaws or maxille, and (4) a lower lip. The two lips move up and down while the two pairs of jaws move from side to side. All these structures are well adapted Fig. 18. Mouth parts of a cockroach. (Parker and Haswell.) for holding and biting off leaves of grass or other plants, and this seems to be the main business of this insect. 28 ANIMAL BIOLOGY Grasshoppers, too, are admirably provided with organs of locomotion. In fact, they derive their name from the ex- traordinary feats of jumping, which they accomplish largely by their long and muscular hind legs. If a boy could jump twenty times the length of his legs, that is, a distance of 50 feet, he would make an athletic record corresponding to that of the common red-legged locust. For the hind legs of an ordinary specimen of this insect are about 2 inches long, and they frequently leap 4 feet. The wings are also of great assistance in enabling the animal to secure its food or to escape its enemies. Flight is accomplished by the help of the hind pair only, and when these are not in use, they are folded like a fan beneath the outer pair. 22. Life history of the grasshopper.— The male grass- hopper may be easily distinguished by the rounded tip. of the abdomen; the abdomen of the female, on the other hand, has at its posterior extremity four movable parts which constitute the egg-laying organ or ovi- positor (Fig. 19). The eggs are pro- duced within the body of the female insect. Before these eggs can develop, however, each must be fertilized by a sperm-cell produced by the male grasshopper, just as an egg-cell of a plant must be fertilized by the sperm- nucleus of a pollen grain (P. B., 91). After the process of fertilization has taken place, the female grasshopper Fic. 19. — Grasshopper laying eggs. (Riley, U. : S. Dept. of Agriculture.) (usually in the fall of the year) bur- rows a hole in the ground by alter- nately bringing together, pushing into the earth, and then spreading apart, the four projections that make up the INSECTS 29 ovipositor (Fig. 19). From 20 to 40 small, banana-shaped eggs are then laid in the bottom of the hole. In the spring each egg hatches into a tiny grasshopper, which much re- sembles the adult, except that it has no wings and its head is relatively large in comparison with the rest of the animal. The insect begins at once to feed and grow, but since its whole exterior is hard and resistant, growth can only take place after this outer covering has been split and the insect has crawled out. This process is known as molting, and takes place five or six times during the life history of the animal. Theinsect then forms a new and larger coat. ok OX At each molt the Fig. 20.— Stages in life history of a grasshopper. wings become more fully developed, until at the last molt the adult insect is produced (Fig. 20). Hence, in the life history of the grasshopper there are three more or less distinct stages: (1) the egg, (2) the developing insect, which is known as the nymph, and (3) the adult grasshopper. This suc- cession of changes in a life history is known as meta- morphosis (Greek, meta = one after another + morphos = form). But, because in the development of the grasshopper thesé changes are not so striking as those that occur in the life history of the butterfly (11), the metamorphosis of the grasshopper is said to be incomplete. It is better, however, to refer to it as a direct metamorphosis, that of the butter- fly being known as an indirect metamorphosis. After reach- ing the adult stage and depositing eggs, the adult insects die. Only a few of the immature grasshoppers survive the winter, and these are the grasshoppers that are seen early in Spring. 30 ANIMAL BIOLOGY 23. Economic importance of grasshoppers. — Our laboratory study of a grasshopper’s mouth parts and our observations of its methods of feeding have shown that these insects resemble cater- pillars, first, in having biting mouth parts (Fig. 18), and second, in being voracious eaters. Hence, as we should expect, a large number of grasshoppers in a given area would mean a considerable destruc- tion of plant life. Many “ plagues of locusts’’ (for grasshoppers are more correctly known as locusts) have been recorded in history. One of the first is that recorded in the Bible, which occurred before the departure or “ Exodus’ of the Children of Israel from Egypt. “ And they (the locusts) did eat of every herb of the land, and all the fruit of the trees . . . and there remained not any green thing in the trees, or in the herbs of the field throughout all the land of Egypt.” (Ex. x. 15.) In our own country during the years 1866 to 1876 there were several plagues of locusts in the grain-producing states of the West, notably in Kansas and Nebraska. The Rocky Mountain grasshoppers during these years migrated in such numbers that the sky was dark- ened during their flight, and the result of their devastation was as serious as that described in Exo- dus. According to one authority this species of insect destroyed $200,000,000 of crops in the west- ern states in the space of four years. No great migrations have occurred since 1876. Locusts have been used as food, and even at the present day they are commonly eaten by the Ara- bians. In the Bible, it is related of John the Baptist, that while Fig. 21.— Four walking sticks on preaching in the wilderness “he did abranch. (Coleman.) eat of locusts and wild honey.” INSECTS 31 24. Relatives of the grasshopper.— Other insects that have structure, habits, and life history similar to those of the grasshopper are the crickets, cockroaches, katydids, and walking sticks. The cockroaches are more commonly known in New York City as “‘ Croton bugs ” from the fact that they frequent places close to water pipes through which Croton water is carried. They are very fast runners, as any one knows who has tried to catch them, and their bodies are so thin that they can easily hide away in narrow cracks. Their sharp jaws enable them to feed upon dried bread and other hard food (Fig. 18). Katydids and walking sticks are striking examples of ‘protective resemblance; that is, they resemble their surroundings in form or color so closely that they may secure protection from their enemies by this means (Fig. 21). . III. Bees AND THEIR RELATIVES 25. A study of the bumblebee. — (Laboratory study.) A. General survey. 1. Give the names of the regions that you find in the body of the bee. (See 20, A.) 2. State the number and situation of the antenna. (See 20, B.) 3. How many compound eyes are present, and where are they situated? (See 20, B, 3.) 4. (Optional.) With the help of a magnifier look for the simple eyes on the top of the head and between the com- pound eyes. How many simple eyes are there, and what is their color? (See 20, B, 4.) 5. Examine the legs and state — a. Their number, and the region of the body to which they are attached. b. The relative size of the different pairs. c. Their adaptations (by structure) for walking. 32 ANIMAL BIOLOGY 6. Examine the wings and state — a. Their number, and the region of the body to which they are attached. b. Their characteristics of texture. c. Their adaptations for flying. 7. Is the abdomen segmented or not? B. Food-getting organs. 1. If the mouth parts do not project from the lower part of the head, you should find them bent back- ward beneath the head and thorax. Use the dissecting needle to straighten them out. Carefully separate these mouth parts and count them. a. How many mouth parts do you find? b. Describe the general shape of all these parts. c. How are the mouth parts fitted to enable the bee to get nectar from flowers? 2. (Optional.) Spread the mouth parts on some white blotting paper and stick pins into the blotting paper so as to keep the parts from coming together. Use the magni- fier to distinguish the following parts :— a. The central, longest part, the tongue. (It has hairs on its surface.) The tongue springs from a broader body, the lower lip. b. Two shorter parts on either side of the tongue, springing also from the lower lip, and called labial palps be- cause they are believed to correspond to the jointed bodies of that name attached to the lower lip of the grasshopper and other insects. (See 20, B, 7.) c. Two broader parts springing from a point farther back than the labial palps and supposed to correspond to the helping jaws of the grasshopper, and hence called mazille. (See 20, B, 8.) Draw a front view of the outline of the head and of these five mouth parts (x 4). Label each part. INSECTS 33 3. (Optional.) The bee also has a pair of small mandibles. They are attached to the head below the compound eyes. They extend forward and are often crossed underneath the lower lip. Separate them carefully with the dissecting needle. When the bee uses them, it bends the other mouth parts back out of the way. a. Are the mandibles hard or soft? b. Describe their color and shape. Note. — The honeybee uses the mandibles in forming the wax cells of the comb, and also at times as organs of defense. 4, Examine the hind leg and find the following parts : — a. A fairly prominent segment nearest the thorax, the femur; b. A segment larger than the femur and just below it, the tibia; c. A broad segment below the tibia, the basal part of the foot or tarsus; d. The remainder of the tarsus or foot consisting of four tiny segments with hooks on the end segment. Make a drawing of one of the hind legs (x 4) to show all these parts in outline and label femur, tibia, basal part of tarsus, hooks, tarsus. 5. Examine the outer surface of the tibia with a magnifier, noticing several rows of hairs around the margin. The portion of the tibia that faces outward, together with the hairs, is called the pollen basket. Locate the pollen basket and show how it is adapted for holding pollen. 26. History of beekeeping. — ‘‘ It is abundantly evident from the records of the remote past that beekeeping has always been a favorite occupation with civilized nations. Egypt, Babylon, As- ‘syria, Palestine, Greece, Rome, and Carthage all had their bee- keepers... . In the days of Aristotle (in Greece) there are said to D 34 ANIMAL BIOLOGY have existed two or three hundred treatises on bees, so that, then as now, beekeeping was a favorite topic with authors. More books have appeared on bees and bee-culture than have ever been published about any domestic animal, not excepting the horse or the dog.” ! Yet from the earliest times until the middle of the last century there was little improvement in the method of keeping bees. They were allowed to build their combs in hollow trunks of trees or in hives so constructed that it was impos- sible to control in any way the work of the bees (Fig. 22). In 1852, however, Rev. Lorenzo Lang- stroth of Philadel- phia invented a hive with movable frames, and his in- vention wholly rev- olutionized the bee- Fic. 22.—Old type of beehive. (From Inter- keeping industry. national Encyclopedia. Dodd, Mead & Co., Practically all mod- mE) ern hives through- out the world are constructed on the plan that he introduced, which is essentially as follows. In a rectangular box are sus- pended eight to ten movable frames, in each of which the bees build their comb, store honey, and develop their young; for this reason this part of the hive is known as the brood chamber. (One of these frames, covered with bees is shown in Fig. 23.) As the season advances, the beekeeper places above the brood chamber successive supers (Latin, super = above), each supplied with little boxes (Fig. 23) which when filled with honeycomb usually weigh about a pound. It is this excess of stored honey that is commonly offered for sale. 1Cyclopedia of American Agriculture, Vol. III, p. 278. INSECTS 35 27. Characteristics and functions of the queen and the drones. — Honeybees, though smaller than bumblebees, resemble them in their general plan of structure; that is, both kinds of insects have a head, thorax, and abdomen, all Fig. 23. — Modern type of beehive. more or less covered with hair, and on the thorax are two pairs of membranous wings and three pairs of jointed legs. In every colony of bees there is, except at rare intervals, only one queen. The queen-bee (Fig. 24) can be readily distinguished from all’ the other individuals in the hive by her long, slender abdomen (Fig. 24). It is her sole busi- 36 ANIMAL BIOLOGY ness to deposit an egg in each of the various wax cells of the brood chamber. Queens have been known to lay 3000 eggs in a single day, and since a queen may live as long as five years, she may lay over 1,000,000 eggs during a lifetime. The queen is therefore the mother of all the bees in a colony. The distinguishing characteristics of drone or male bees (Fig. 24) are their broad abdomens, the absence of a sting, and their very large, compound eyes, which nearly meet on the top of their heads. In numbers they vary at different : Fig. 24. arene) queen, and miGtaer bee. times of the year, but during the summer there are usually 400 to 800°in a hive. We learned in our study of reproduction in plants that egg-cells will not develop into seeds unless they are fertilized by sperm-cells of pollen grains. Now in a beehive, an egg will never develop into a queen-bee or a worker unless it likewise is fertilized by a sperm-cell. The drones or male bees supply these necessary sperm-cells. From the unfer- tilized eggs, which a queen may lay, develop only drone bees. In this respect these egg-cells of bees are strikingly different from those of plants and of most animals. It is clear from the foregoing account that the queen and drones carry on the reproductive functions of the colony, for they are specially adapted to increase the number of bees in a hive. To the workers, on the other hand, as we shall now see, belong most of the nutritive functions of the colony. INSECTS 37 28. Characteristics of worker bees. — While the workers are smaller than either the queen or the drones, they are by’ far the most numerous, there being as many as 50,000 in a good colony in midsummer. In shape they resemble the queen, as one would expect, since they are undeveloped female bees. As was the case with the bumblebee, their mouth parts are very complicated, consisting of a central tongue and two other pairs of appendages, all of which form a hollow tube for sucking up the nectar of flowers (Fig. 25). Above the tongue is a pair of horny jaws that move from side to side, which the bees use main- ly for comb build- ing. On the tibia of each hind leg of a worker bee is likewise a fringe of stiff hairs, which, L«: te Fig. 25.— Mouthparts together with the Frc. 26.— Hind leg of bee of a bee. concave outer sur- with pollen, inner surface. faee of the tibia, forms a pollen basket similar to that of the bumblebee. In this the insect gathers a mass of pollen which may easily be seen when the workers are returning to the hive (Fig. 26). 29. Comb building. — All the work of comb manufacture is carried on by the worker bees, and when one studies this process carefully, it is found to be one of the greatest marvels of animal activity. The cells of the comb are built out horizontally from each side of a central partition in a brood frame or of a super box. To 38 ANIMAL BIOLOGY save the bees’ time and to insure even comb, beekeepers usually insert in the frames or honey boxes thin sheets of wax “ foundation” on which the bases of the cells have been impressed by machinery. Upon this the workers build the comb outward. But without this assistance from man the comb cells are usually remarkably regular and show the greatest economy in the use of wax. The cross section of each cell is a hexagon, and so these compart- ments fit together with- out any spaces between them as would occur if the cells were cylinders. (See Fig. 27.) This hex- agonal shape also permits a single partition wall to serve for two adjacent cells, and it is evident that this shape of cell more closely fits the body of the bee than would a four-sided cell. The worker bees build two different sizes of cells in Fic. 27. — Worker cells and queen cells. the comb. Most of the ee eer pent cells average out twenty-five to a square inch, and in these the fertilized eggs are laid, which, as we have said, develop into workers. The cells in which unfertilized eggs are deposited are somewhat larger. These form the so-called drone comb. The wax from which the comb is produced oozes out from cer- tain glands on the ventral surface of the abdomen of the workers. When producing the wax the bees hang motionless inside the hive for several days, each holding to the bees above. They have al- INSECTS 39 ready gorged themselves with honey, and it is estimated that from seven to fifteen pounds of honey are required to produce one pound of wax. As the little plates of wax are formed, they are seized by a bee and carried with its mandibles or under its ‘“ chin” to the comb where the building is going on. Here the wax is pressed against one of the walls. 30. Honey making. — While studying flowers we learned that they secrete a sweet liquid known as nectar. It is this that the workers use for honey manufacture. The bee inserts into the blossom its sucking tongue and pumps up the nectar into a sac known as the honey stomach (Fig. 28). Here a kind of digestion takes place whereby the nectar is changed to honey. If the worker bee is hungry, it opens a little trapdoor and allows the honey and _ ing pore pollen to pass into the true stomach. But since the insect, usually makes more honey than Fic. 28, — Internal organs of bee. (Lang.) it can use, when it re- turns to the hive it squeezes its tiny honey stomach. and deposits the surplus in the cells of the comb. This honey, when first made, contains a good deal of water; it would there- fore take up too much room in the comb and it would be more likely to run out from the horizontal cells. Hence, some of the workers fan with their wings and evaporate the surplus water. When the cells are completely filled, they are capped over with wax. ---honey scomach i a -- true air sac-- a : stomach 40 ANIMAL BIOLOGY 31. Other duties of worker bees. — Bees, we have also learned (28), bring in large quantities of pollen packed in the pollen baskets of the hind legs, and in gathering pollen a considerable amount clings to the head and other parts of the body. Worker bees also bring in from the buds of trees a brown, gummy substance called bee glue or prépolis which they use to close up crevices in the inside of the hive. In most hives, too, certain bees seem to be detailed to act as soldiers to keep out individuals from another swarm or other marauders which might raid their stores of food. During the busy summer season a worker usually lives only a month or two. Certainly enough has been said to convince any one that a bee colony is a wonderful social community, organized more com- pletely, so far as division of labor is concerned, than many a human community. Is it a monarchy ruled by the queen, or a democracy controlled by the workers? The latter is more probably the case. Yet we can hardly imagine how the thousands of individuals can work together in such a helter-skelter way and accomplish such wondrous results. 32. Life history of the honeybee. — The eggs of the bee are tiny white objects, shaped more or less like a banana. A single egg is fastened by the queen mother at the bottom of each cell in the young larva just hatched from egg broo d comb (Fig. 29). At the end of three days the egg hatches into a mi- nute footless grub or larva (Fig. 29) which is fed for the first few days on rich Fic. 29. — Stages in life history of honeybee. food, produced in (Cheshire). the stomach of the 1¥or interesting descriptions of the work eetried on in beehi see ‘‘A, B, C of Bee Culture,” by A. I. and E. R. Root. ' einen INSECTS 41 workers that are acting as nurses. The grubs are then fed with a mixture of pollen and honey, and at the end of six days after hatching they are supplied with enough of this mixture to last during the rest of the larva stage, and the cells are then capped over with wax by the workers. There the developing bees pass through the third or pupa stage (Fig. 29), and at the end of twelve days bite their way out of their nursery cells and take their share in the busy toil-of the hive. Drones, we have said, develop in somewhat larger cells than worker bees. When the colony wishes to produce a queen, the workers build a cell about as large as the end- joint of one’s little finger (Fig. 27), and as soon as the egg is hatched they stuff the little grub throughout the larval stage with what is called “ royal jelly,’”’ never giving it the undigested pollen mixture that is supplied to the grubs of ‘workers or drones. ‘33. Swarming. — We come now to one of the most interesting events in the story of bee colonies. If several queens emerge from their cells at the same time, they attack each other in a royal battle, for it is said that a queen never uses her sting except against a rival. When the conflict is over, the victorious queen becomes the mother of the hive. For in the meantime the former queen, surrounded by half the drones and workers, has left the old hive, abdicating in her daughter’s favor. After emerging from their old home, the swarm of bees thus formed alights on a neighboring tree, clinging to each other in asolid mass. It is then comparatively easy for a beekeeper to shake the insects from the limb into a new hive, and if the queen is secured, the swarm will usually begin work at once in their new home (Fig. 30). If, however, the bees are not captured, scouts go out to search for a hollow tree; and when satisfactory quarters are found, the whole swarm follows their guides, and build their comb in the home thus secured. 42 ANIMAL BIOLOGY 34. Economic importance of bees. —In our study of flowers we referred frequently to the necessity of the visits of bees to insure cross-pollination. Indeed, Professor Hodge says (‘‘ Nature Study and Life’’) that for all practical purposes Fic. 30.— A swarm of bees on a limb. (Lyons.) so far as man is concerned, the honeybee is sufficient for this purpose (with the exception of securing a red clover crop, which requires the help of the bumblebee). In years to come we may be sure that the most successful fruit farmers will also keep bees. It is estimated that the annual production of honey and wax in the United States amounts to between twenty and thirty millions of dollars, and if scientific management were to be introduced more widely, this output could be raised to fifty million dollars a year without additional investment. Almost any one who is interested can keep bees. During a INSECTS 43 single season the swarm in the observation hive on the fourth floor of the Morris High School in New York City produced fifty-six pounds of honey in the super boxes, besides laying by in the brood chamber a sufficient supply for their winter support. 35. Relatives of the bees. — Wasps and hornets belong to the same order of insects as the bees, and resemble them more or less closely in structure. Some kinds of wasps build paper comb from wood which they chew up with their jaws. Ants, insects with which every one is familiar, are likewise classed with the bees and wasps, and the social communities that they form are marvelous in the degree to which they carry division of labor. In some ant colonies in addition to the workers there are soldiers and slaves. IV. MosquiToEs AND FLIEs 86. Life history of the common inland or house mosquito. — The eggs of the common house mosquito are laid by the female in little rafts that float on the surface of stagnant water. These egg masses look like flecks of black soot, but when examined with a hand lens each is found to consist of 200 to 400 cartridge-shaped eggs standing on end (Fig. 31). If the weather is warm and other conditions are favor- able, the eggs hatch within a day into tiny mosquito larve, which are known as “ wrigglers”’ from their characteristic motion in the water. In the second stage in its life history, which usually lasts about a week, the mosquito larva feeds on the microscopic plants and animals that abound in all stagnant water, and grows rapidly. Just as was the case with the butterfly and moth caterpillars, this rapid growth necessitates the frequent shedding or molting of the outer covering of the larva and the formation of a new and larger coat. Hence, in water 44 ANIMAL BIOLOGY Fig. 31. — Life history of house Fig. 32.— Life history of malaria mosquito (Culex). mosquito (Anopheles). (Howard, U.S. Dept. of Agriculture.) INSECTS 45 where mosquitoes breed, one finds countless “suits of cast-off clothing” which would fit all stages of the young wrigglers. The mosquito larva has a well-developed head, a thorax, and a jointed or segmented abdomen, but legs and wings are wanting. The most striking characteristic of this stage of the mosquito is the breathing tube that projects diag- onally from the hind end of the abdomen. For while the mosquito larva lives in the water, it is obliged to swim to the surface at short intervals to get its necessary supply of air. It then hangs diagonally with the tip of its breathing tube pro- jecting through the surface film into the air above (Fig. 31). This habit frequently proves its undoing, as we shall see when we come to discuss the methods of mosquito extermi- nation. After attaining its full growth as a larva, the insect enters the third or pupa stage (Fig. 31). “‘ The pupa,” says Miss Mitchell in her “‘ Mosquito Life,” ‘is the form intermediate between the larva and the adult. Unlike most pupa, those of the mosquito are very active, but like other pups, they do not eat. They are about the shape of -fat commas, floating quietly at the surface or bobbing crazily downward at the least alarm to hide at the bottom, propelled by back- ward flips of the abdomen. ... The creature no longer breathes through a single tube on the eighth segment of the abdomen but by means of a pair of tubes on the back of the thorax.” During this stage the insect develops its sucking mouth parts, its long, slender legs, and its two deli- cate wings, and all these organs may be seen through the transparent. outer coat, which is composed of a substance known as chitin. At the final molt the mosquito leaves its pupal case in the water and flies into the air, an adult mosquito. If it hatches 46 ANIMAL BIOLOGY during the spring, summer, or early autumn, it usually lives no more than a week or two; but many of the female mosquitoes that develop late in the autumn seek out a protected spot in which to spend the winter, and thus are ready in the spring to perpetuate the species by laying eggs in the stagnant pools formed by early rains. All that the mosquito needs, therefore, in order to develop its offspring from egg to adult stage is a bit of water that will remain relatively undisturbed for about two weeks. Hence, old tomato cans, bits of crockery, and other receptacles carelessly left in many a back yard, furnish breeding places for all kinds of mosquitoes. Truth compels us to remark, in passing, that the male mosquito is a decent sort of fellow, keeping close to his breed- ing place and feeding on plant juices or eating nothing at all during his brief existence in the adult stage. It is the lady mosquito that torments us by singing her piercing song and piercing our suffering skins. But as in most other suffer- ings that we endure, the fault is largely our own. At least we can secure immunity if as communities we but persist in applying the simple methods of extermination outlined in 42. 37. Life history of malaria-transmitting mosquitoes.— The mosquito we have just described, while a nuisance wherever found, does not, so far as is known, cause disease. There are, however, two kinds of mosquitoes that are not only a nuisance but a menace to life and health wherever they are found; namely, those that transmit malaria and yellow fever. The first of these is the Andpheles mosquito, commonly known as the “ malaria mosquito,” for as we shall soon see, malaria cannot be transmitted from one human being to another except through the agency of this species INSECTS 47 of insect. The eggs of the Anopheles mosquito are larger than those of the house mosquito and are laid singly, not in masses (Fig. 32). Inthe larva stage, likewise, the two insects may be easily distinguished from the fact that the “malaria wriggler,” while breathing, lies horizontally just beneath the surface of the water, while the other species hangs downward, with only the tip of the breathing tube projecting to the water level (Figs. 31 and 32). In Figs. 31 and 32 the characteristic position of the adults of the two species is shown. While the body of the house mosquito is usually parallel to the surface on which it alights, that of the malaria-transmitting insect is sharply tilted away from the surface. 38. Occurrence of malaria. — The story of the discovery that a kind of mosquito known as the Anopheles mosquito is the only means, as far as we now know, by which malaria may be transmitted from one individual to another, is one of the most wonderful in all the history of biology. In a guide leaflet on ‘‘ The Malaria Mosquito ” published by the Ameri- can Museum of Natural History, New York City,! the author, B. E. Dahlgren, writes as follows :— “Tt was early observed that ‘malaria’ was apt to be prev- alent during the damp and rainy seasons, and that it oc- curred principally in exactly such places as are now known to furnish ideal breeding grounds for the malaria mosquito. That new cases of malaria appeared at the time of year when the Malaria Mosquito abounded, was also recorded long before it was suspected that the insect was in any way con- 1Every one who visits the American Museum should study care- fully the wonderful set of models that show on a big scale the various stages in the life history of the mosquito. These models are pictured in the bulletin referred to above, which may be ob- tained from the librarian of the Museum for fifteen cents. 48 ANIMAL BIOLOGY nected with the malady; and one of the old medical writers mentions as a characteristic of malaria seasons that ‘gnats and flies are apt to be abundant.’ .. . “Malaria was formerly considered to be a form of ague due to foul air, whence its name, which literally means ‘ bad air’ It was attributed to a sort of ‘miasma.’ Its true nature did not become known till 1880, when Laveran, a French military surgeon, working, at the time, in Algeria, discovered the malarial parasite in human blood.” Major Ross, an English officer in India, later proved the presence of the parasite in the body of the mosquito. 39. Transmission of malaria. — Investigation has shown that the parts of the world where Anopheles abound are the eastern half of the United States and a large part of Europe, together with many regions of the tropics. It is a well- known fact that these are the regions, too, in which malaria is very abundant, and this is the first line of proof that the Anopheles mosquito is always responsible for the trans- mission of malaria. Even more conclusive were the experiments of four investi- gators who spent the fever season in the dreaded malaria district of the Roman Campagna. They built for themselves a carefully screened house in which they remained from sun- set to sunrise, and this was the only precaution that they ob- served. In the daytime they went freely among those who were stricken with the fever, they allowed themselves to be soaked with the falling rains, and at night the air from the swamps came freely into their sleeping quarters. But while hundreds of malaria cases were all about them, not one of the four contracted the disease. Hence, to escape malaria, one has only to make sure that Mrs. Anopheles is prevented from injecting her billful of malaria germs— and this she does E INSECTS 49 only during night time, “ loving darkness, rather than light, because her deeds are evil.” In the year 1890 Dr. Manson and Dr. Warren, two physi- cians in London, allowed themselves to be bitten by Ano- pheles mosquitoes that had previously bitten malaria pa- tients in Italy. In eighteen days both developed malarial fever and in the blood of both, malaria organisms were found, although previous to this infection from the mosquito neither had suffered in any way from the disease. 40. Life history of the malaria parasite. — But yet more wonder- ful proof that the mosquito transmits malaria has been furnished by the microscopes of biologists. The discovery of the malarial parasite by Laveran in 1880 has already been referred to. This resembles in its form and activities a single-celled animal known as the Amoeba (124). When this organism of malaria is present in human blood, it bores its way into a red corpuscle (H. B., 6), feeds upon the contents of this blood cell, and grows at the expense of the corpuscle until the parasite occupies nearly all the space inside it (Fig. 33). The malaria parasite then divides into a number (6-16) of daughter parasites, which rupture the red corpuscle in which they have been developing, and escape into the liquid part of the blood, thus causing the chills so characteristic of malaria. Each new para- site then attacks a new corpuscle and at the end of two or three days produces six to sixteen new spores, and so the organisms multiply. Now here comes the relation of the mosquito to malaria. For when the female Anopheles bites a person having malaria, she is likely to suck up blood that contains malaria organisms in a cer- tain stage of development. These reach the insect’s stomach, where - they pass through a stage known as fertilization. In the stomach of a single mosquito as many as five hundred of these fertilized cells’ have been counted. Each cell then becomes pointed at one end, bores its way through the wall of the mosquito’s stomach, and in fifteen to twenty days produces relatively large swellings on the outer surface, in which are thousands of needle-shaped malaria spores (Fig. 33). E 50 ANIMAL BIOLOGY At length these spores escape through the outer wall of the mosquito’s stomach and many of them find their way to the salivary glands. And so when the infected mosquito bites another person, these parasites are injected with the saliva, and if the conditions are favorable in the blood of the new victim, the spores straightway attack the red corpuscles, and a new case of malaria is the result. For the treatment of malaria quinine is the most effective drug known at present. It should be taken in the quantity and at the times prescribed by the physician. malaria parasite enter- ing a red blood cor- a? puscle and develop- eS r) ing 13 new parasites with malaria spores alae stomach of a mosquito Z > a ee | with swellings filled ae salivary glands of mosquito (much en- malaria spores from larged) Fig. 33. — Life history of the malaria parasite. (Dahlgren, American Museum Natural History.) 41. Transmission of yellow fever. — The proof that malaria can only be transmitted from one human being to another was largely the work of the biologists of England, France, and Italy. The dis- covery that another kind of mosquito (Stegomyia) is responsible for the transmission of the parasite that causes yellow fever is due al- most wholly to the splendid achievements of the Yellow Fever Com- mission appointed by President McKinley. In June, 1900, this commission of five, headed by Dr. Walter Reed (Fig. 34), began its epoch-making experiments in the Island of Cuba, and within six INSECTS 51 months these men demonstrated conclusively that this plague disease of the tropics and of our southern states can, so far as -we know, be communicated only through the agency of the Stegomyia mosquito. This commission, believing in the mosquito theory, at once began experiments to demonstrate its truth. One of the members, Dr. Fic. 34.— Dr. Walter Reed. Lazear (Fig. 35), permitted a mosquito to bite him ; a few days later he contracted the disease and died. The inscription on a tablet erected in his memory reads as follows: ‘‘ With more than the courage and devotion of the soldier, he risked and lost his life to 52 ANIMAL BIOLOGY show how a fearful pestilence is communicated and how its ravages may be prevented.” When Dr. Reed called for volunteers from among the soldiers, the first to respond ‘ was a young private from Ohio, named John R. I'ie. 35. — Dr. Jesse Lazear. Kissinger (Fig. 36), who volunteered for the service, to use his own words, ‘ solely in the interest of humanity and the cause of science.’ When it became known among the troops that subjects were needed for experimental purposes, Kissinger, in company with another young private named John J. Moran, also from Ohio, volunteered their services. Dr. Reed talked the matter over with them, ex- INSECTS 53 plaining fully the danger and suffering involved in the experiment should it be successful, and then, seeing they were determined, he stated that a definite money compensation would be made them. Both young men declined to accept it, making it, indeed, their sole stipulation that they should receive no pecuniary reward, where- upon Major Reed touched his cap, saying respectfully, ‘Gentlemen, I salute you.’ Reed’s own words in his published account of the experiment on Kissinger are: ‘In my opinion this exhibition of moral courage has never been surpassed in the annals of the Army of the United States.’ ” } The object of one of the first experiments was to determine whether or not yellow fever could be contracted from clothing worn by yellow fever patients. A small building was constructed the win- dows and doors of which were carefully screened. Into this were brought chests of clothing that had been taken from the beds of patients who had been sick and in some cases had dicd of yellow fever. Three brave men entered the building, un- packed the boxes, and for twenty nights slept in close contact with yg. 36.— John R. Kissinger, U.S.A. the soiled clothing. ‘ To pass twenty nights in a small, ill-ventilated room, with a temperature over ninety, in close contact with the most loathsome articles of dress and furniture, in an atmosphere fetid from their presence, is an act of heroism which ought to command our highest ad- miration and our lasting gratitude.’’? In spite, however, of their unwholesome surroundings, none of the men contracted yellow 1From “Walter Reed and Yellow Fever,’’ by Dr. H. A. Kelly Doubleday, Page & Co. 2“*Walter Reed and Yellow Fever.” 54 ANIMAL BIOLOGY fever, and so it was proved for all time that this disease cannot be communicated by means of anything that comes from the body of yellow fever patients. Dr. Reed now sought to prove that the Stegomyia mosquito was the means by which the disease was transmitted from one person to another. A second building, the same size as the first, was erected, the room was divided by a wire screen, and all the doors and windows were carefully screened (Fig. 37). Into one of the rooms a number of mosquitoes that had bitten yellow fever patients were freed and a SnfecLid Grrregeule Cecsloling Fnont o Fulding ‘el, i" eee a: & Bek 1 gal. 50 gal. 1The authors are indebted to Professor Glenn W. Herrick of Cornell University for these formulas. CHAPTER II BIRDS 48. Study of a bird. — (Optional home work.) So far as possible the following study should be made from a robin, sparrow, chicken, or other living bird, and the observations should be supplemented by an examination of stuffed specimens, charts, or pictures. A. Regions. In all animals that have internal bony skeletons as do birds, at least two of the following regions may be distinguished; namely, a head, a neck, a trunk, and a tail. Which of the four regions named above can you dis- tinguish in the bird that you are studying? B. Head. 1. Describe the general shape of the beak (or bill), stating whether it is relatively long and slender, or short and thick. State, also, whether the tip of the beak is straight or curved. 2. On what part of the head are the eyes located? In the eyes of a bird the following parts are visible: a central pupil, and around this a colored region known as the iris. State the location and describe the color of each of these parts in the eye of the bird that you are studying. 3. In front of the eyes find two openings, the nostrils. Locate the nostrils with reference to the beak and the eyes. 4. Make a drawing twice natural size of a side view of the head to show the beak, eye, and nostril. Label each part shown. ; 62 BIRDS 63 5. Watch a chicken, canary, sparrow, or other bird while it is eating and drinking, and describe the movements that the bird makes in these acts. C. Organs of locomotion. 1. What is the position of the wings when they are not in use? 2. Note and describe the movements of the wings when the bird is flying. i 8. The only part of the leg that is visible in most birds is the foot, the upper parts being covered with feathers. a. How many toes do you find pointing forward and how many backward? (Be sure to name the kind of bird on which this observation is made.) b. Make a drawing to show the foot and the toes with the claws at the end of each. Label toes and claws. 4, Watch several kind of birds (e.g. robins, sparrows, chickens, starlings), and state whether each of these kinds of birds walks or hops. : 49. What is a bird? — Birds, like fishes, frogs, and man, belong to the group of animals that have a backbone, and hence are known as vertebrates. It is never difficult, however, to distinguish birds from other vertebrates, since every bird has wings either developed or undeveloped (Fig. 46) and a covering of feathers. Birds; too, maintain a body temperature that is higher than that of any other group of animals. The temperature in man, for instance, is normally about 983° F., whereas no bird, so far as we know, has a tempera- ture less than 100° F., and even 111° F. is known to be the temperature of some of the sparrows and warblers. Hence, we may define a bird. as a warm-blooded vertebrate, having wings and a body covering of feathers and usually able to fly. Even a casual examination will show that a bird has a head, neck, and trunk, and two pairs of appendages, namely, the 64 ANIMAL BIOLOGY wings and legs. With the exception of the feet, practically the whole of the animal is covered with feathers (Fig. 46). Mostil UpperMandible On Lower TandiblOX se" epee: F: 5 ; as Heine | Wing Corerts. Throati-* aN -Greater, ss : oR Nov:z Secondaries ! {~~ Ru Least / Hinge Fic. 46. — External structure of a bird. 50. Head. — A closer study of a bird shows that from the front part of the head projects a horny structure known as the beak or bill. ‘Tie a man’s hands and arms tightly behind his back, stand him on his feet, and tell him that he must hereafter find and prepare his food, build his house, defend himself from his enemies and perform all the busi- ness of life in such a position, and what a pitiable object he would present! Yet this is not unlike what birds have to do. Almost every form of vegetable and animal life is used as food by one or another of the species. Birds have most intricately built homes, and their methods of defensé are to be numbered by the score; the care of their delicate plumage BIRDS 65 alone would seem to necessitate many and varied instru- ments: yet all this is made possible, and chiefly executed, by one small portion of the bird — its bill or beak.” ! While the size and shape of the bill varies greatly in differ- ent kinds of birds, it always consists of two parts (mandibles) (Fig. 46), which correspond in position to the upper and lower jaws of man. When the bill is opened, a careful ex- amination shows that a bird has no teeth. Some of the birds that lived ages ago, however, had well-developed teeth in their jaws, as is well shown in (Fig. 47) which is a picture of a bird skeleton re- stored from bones found in the rocks of western Kansas. Near the base of the bill on either side, one can usually see an opening; these open- ings are the nostrils. On the sides of the head are the two eyes, and since they bulge out somewhat, the bird is afforded a wide range of vision. If the feathers below and behind the eye are pushed aside, an opening into the ear may be seen; this may be made out easily in the head of a chicken. Fig. 47.— Skeleton af a fossil bird. 51. Wings. —In Figure 48 are shown the bones that com- pose the wing of an ostrich and the arm of a man, and on com- paring the two one sees a striking resemblance. In both, the upper arm has a single bone, while in the forearm there 1 Beebe, ‘‘The Bird.” 66 ANIMAL BIOLOGY are two bones. In the hand region, though the differences are more striking, the general plan of the two is the same. Unlike the bones of the human skeleton those of most birds are hollow and filled with air. Any one who has eaten a chicken’s wing knows that the bones are covered by muscles; these enable the bird to fold and unfold the parts of the wing, much as the human arm is stretched out or doubled up. On the bird’s body are other powerful mus- cles, which cause the wing as a whole to make the upward and downward strokes in flight. Still another won- derful adaptation of the wing for flight is evident in the arrangement and structure of the feathers (Fig. 49). Fig. 48.— A, skeleton of arm of aman; B, skele- Thefeathers fitover ton of wing of an ostrich. (A. E. Rueff.) each other in such a way! that in the downward and backward stroke of the wing a continuous surface is struck against the air, and this propels the bird upward and forward. In the up- 1 Before assigning these paragraphs the structure of a feather and the arrangement of the feathers on the wing of some bird (e.g. a chicken) should be demonstrated to the class. BIRDS 67 ward wing stroke, on the other hand, the resistance of the air is diminished since the feathers are separated more or Fic. 49. — Wing of Tern. (Photographed by E. R. Sanborn, N. Y. Zoological Park.) less like the slats of a Venetian blind, thus allowing the air to pass between them. zede= barbules ' with | hooks ' barbules /’ y i without ~~~ 1, f hooks i B \ ‘ A va ' i} ' aut t ‘ postese ' ‘ ‘vane ---"" , shaft barb Fic. 50. — Structure of a feather. An examination of a single feather! shows that it consists in the first place of a shaft running through its length (Fig. 1 See footnote, p. 66. 68 _ ANIMAL BIOLOGY 50, A). On the sides of the shaft are the two flat surfaces which make up the vane. This vane is composed of slender parts called barbs that may be easily separated from each other, or when sep- arated may be read- ily united, because . of little hooks (Fig. aa i 50, B). This the Sees, bird does when it smooths or‘‘preens” its feathers. 52. Legs.— On comparing the arm of man with the wing of a bird we found that ee. ; | they were similar in wowes structure, and the same is likewise true of the leg and foot. While the thigh of a bird is much shorter proportionately than PROnes ey is that of man (Fig. ng 51), both have but a single bone. Below the knee of the. bird is the shank or ‘“drum- stick” which consists Fie. 51.— A, skeleton of leg of an ostrich; B, ee < long bene ex: skeleton of leg of aman. (E. R. Sanborn.) tending to the ankle, and beside it is a stehidat bone attached only at the upper end. This region in the leg of man is likewise composed of a relatively thick shin bone, on the outer side of which is a thin bone extending down to the ankle. BIRDS 69 The ankle region of a bird is the joint half-way up the leg (Fig. 51,:A). _What is commonly regarded as the bird’s foot consists often of three toes that point forward, and one that extends backward. Ordinarily the parts of the leg below the ankle are covered with scales, and the tips of the toes are provided with claws. 63. Study of a hen’s egg. — (Optional home work.) Secure the egg of a hen or other domestic bird, and study it as follows :— 1. Describe the difference in the shape and size of the two ends of - the egg. 2. Carefully crack the shell at the larger end and remove the pieces of shell. a. State what you have done and describe the membrane that lines the shell. b. Carefully cut this membrane and note that the liquid con- tents of the egg do not completely fill the eggshell in this region. This cavity is called the air space. Describe the position of this air space. young shell embryo inner membrane outer mem- brane air space Fig. 52. — Egg of a hen. 70 ANIMAL BIOLOGY 3. Pick off the pieces of shell and allow all the contents of the shell to flow out into a cup. or deep saucer, taking care not to break the yolk. a. State what has been done, and describe the position and color of the white and of the yolk of the egg. b. Note two twisted strands extending from the yolk towards each end of the egg. These help to protect the yolk from sudden jars. Describe the position, appearance, and use of these strands. 4, Carefully turn the yolk until you notice a white spot. This spot is the beginning of an embryo chick. Describe the position and appearance of a young chick embryo. 54. Reproduction and life history.—In the preceding section we have seen that a bird’s egg consists of a hard ' shell, 2 membrane, the white f) and the yolk; and that on the outer surface of the latter is a tiny embryo. Let us now see how this egg is formed and developed. In our study of seed-plants we learned that plant em- bryos are formed in the ovary Fic. 53.— Sperm-cells of various of a pistil after an egg-cell poe has been fertilized by a sperm- cell. In the case of insects (22, 27) and the fish (104) we find that egg-cells are produced in organs of the female known as ovaries and that before an egg-cell can develop into an embryo (except in rare cases) it must be fertilized by a sperm-cell (Fig. 53) which has been formed in the spermary of a male. If the ovaries of-a hen are examined, they will be found to consist of a large number of spherical objects, the larger BIRDS vel \ ones being yellow, which vary in size from tiny dots to full- sized yolks (Fig. 54). If any one of these is examined care- fully with a microscope, a single egg-cell may be found. After the yolk has attained its full size and the egg-cell has been M.B.f2 OP ae EE tee Han ve Fic. 54.— Ovary of hen, and egg in egg-tube. fertilized, it receives its coating of white, and the whole is covered with the membranes and the shell. Immediately after fertilization takes place, by the process of cell division many cells areformed. At the time the egg is laid, the chick embryo appears as a tiny white spot on the surface of the yolk when the egg is opened (53, 4). Fur- ther development of this embryo, however, can- not take place unless the egg is kept warm. This is brought about when Fie. 55.—Egg of hen, showing embryo chick on surface of yolk. (Beebe, ‘‘The Bird.’’) 72 ANIMAL BIOLOGY the hen broods over the eggs. Gradually the cells of the different external and internal organs are formed (Fig. 55) from the food material furnished by the yolk and the white of the egg, and at the end of three weeks the young chick breaks through the shell, and soon, under the protection of the mother hen, begins to search for food. When first hatched, the feathers are relatively small and downy. The further development of the chick is largely a matter of growth in size and of change in the character of the feathers. 55. Nests and care of young. — The method of repro- duction in all birds is much the same as that already described Fig. 56.— Comparative size of the eggs of ostrich, hen, and humming bird. (Photographed by E. R. Sanborn, N. Y. Zoélogical Park.) for the chick. Many birds, however, are much more help- * less when they emerge from the egg than are chickens, and so they are sheltered in nests, and the food of the young birds is brought to them by their parents until they are able to fly and for several days afterwards. BIRDS 73 Nests differ greatly in their complexity and in the kind of material used. Some birds, for example the gulls and many other sea-birds, usually deposit their eggs on rocky ledges or in slight depressions in the sand along the shore. On the other hand, the Baltimore oriole constructs out of grasses, plant fibers, and strings a marvelous nest hanging high up in the trees, near the outer ends of branches (Fig. 73). Between these two extremes are all gradations of nest complexity. The eggs laid by birds vary in number, size, and color. The tiny humming bird, for instance, lays two white eggs, each a third of an inch in diameter (Fig. 56) ; three to five greenish blue eggs, each nearly an inch in diameter, are usually found in a robin’s nest, while an ostrich deposits twelve to fourteen eggs, each weigh- ing three to four pounds. 56. Common methods of classification. — One of the simplest ways of classifying birds is that of dividing them into groups according to the kind of food they eat. For instance, we may speak of fish- eating, seed-eating, and insect- eating birds. This, however, is far from being a scientific classification, since birds that differ considerably in struc- ture, and therefore not closely related, frequently live upon the same kind of food. For example, both the pelican (Fig. 57) Fig. 57.— The pelican. (Photo- graphed by E. R. Sanborn.) Fig. 58.— Belted kingfisher. (Wright's ‘‘ Citizen Bird.”’) aN Fic. 59.— Herring gull. (Wright’s ‘ Citizen Bird.’’) BIRDS 15 and kingfisher (Fig. 58) catch and eat fish for food, yet a glance at the two figures shows how unlike in form these two birds are. A second scheme of classification is that based upon their habitat. Thus we may speak of water birds, shore birds, marsh birds, and land birds. This plan, too, may group together birds strikingly unrelated in structure and habits, as becomes clear when we compare two land birds like the hawk (Fig. 64), and the sparrow (Fig. 70). _ 67. Scientific classification of birds. — Modern scientific classi- fication divides the birds of North America into seventeen groups or Fic. 60.— Blue heron. (Wright’s ‘‘ Citizen Bird.’’) orders, all the birds of a given order resembling each other more or less in structure. The common names given to some of these orders are suggested by their habits. As examples we may name diving birds (loon), long-winged swimmers (gulls and terns), scratching birds (hens, turkeys, and quails), birds of prey (eagles, hawks, and owls), and woodpeckers (downy woodpecker). The highest order, known as the perching birds, is divided into twenty families, some of which are the crow family, the sparrow family, the warbler, and the 76 ANIMAL BIOLOGY thrush family. The total number of species of the perching birds is far greater than that of all other species taken together. We shall now group together a few of the more closely related orders, and discuss somewhat their characteristic adaptations of structure. Fic. 61.—Flamingoes. (Photographed in N. Y. Zodlogical Park, by E. R. Sanborn.) 58. Webfooted birds (swimming birds).— In this group we include several orders of birds that have webbed feet, which fit them BIRDS TT for swimming in the water. Common examples of such birds are ducks, geese, albatross, and gulls (Fig. 59). Near the tail region of most of these birds an oil gland is developed, from which the bird obtains the oil that it uses in keeping its feathers from getting water-soaked ; this is likewise true of all other birds. As one would expect, a large number of these species feed upon fish and other water animals. 59. Wading birds.— All the birds in this group have long, slen- der legs, which adapt them for wading out into the water for food. Such birds are the herons (Fig. 60), egrets, storks, and cranes. The flamingoes (Fig. 61) have webbed feet like swimming birds, and so they are regarded as connecting links be- tween swimming and wading birds. . Fig. 62.— Bobwhite. 60. Scratching birds. — This te obwhite group includes the domesticated chicken and turkey and the quail (Fig. 62). All our various forms of chickens are descended from the Fic. 63.— Male and female jungle fowl. (Photographed by E. R. Sanborn, from specimens of the American Museum of Natural History.) 78 ANIMAL BIOLOGY small jungle fowl of India (Fig. 63). The wild turkey still exists in some parts of our country, but it is being rapidly exterminated by hunters. The toes of all the scratching birds are armed with strong, blunt nails, by which they are enabled to dig in the soil for insects and worms. All these birds, too, feed to some extent upon grain, Fic. 64. — Red-shouldered hawk. 61. Birds of prey. — The hawks (Fig. 64), eagles, and owls (Fig. 65), which comprise this group have acquired the name of birds of prey from their habit of catching and feeding on rats, mice, birds, and other animals. Their feet are armed with sharp incurved claws, and the upper part of their bills is hooked ; and so they are specially adapted for seizing and tearing their prey. BIRDS 79 62. Woodpeckers. — These birds are admirably adapted to creep and climb up the trunks of trees, for they have two clawed toes extending forward, and two backward, and their tail feathers are so stiffened that they serve as props against the bark when the bird is resting (Fig. 66). The food of the woodpeckers is largely com- posed of insects, which these birds secure by digging them out of the bark or the wood with their stout, chisel-like bills, and then spearing them with their long tongues. Fig. 65.—Short-eared owl. (Wright.) Se aa aa 63. Perching birds. — This order, as we have said before, con- tains by far the largest number of species of birds. All these birds are specially adapted for holding to the limbs of trees, since the mech- anism of the leg is so arranged that the toes are automatically clutched to the support upon which the bird is sitting. In this group are included practically all of our bird vocalists, hence the perching birds are often called the “ song birds.’’ Among the most beautiful of our songsters are the bobolinks (Fig. 67), catbird, and thrushes (Fig. 68). The young of all the perching birds, for weeks after they are 80 ANIMAL BIOLOGY hatched, are helpless in the nests and are unable to feed themselves. Most of the food of young birds consists of the larve of insects and some of the families, e.g. the fly-catchers (Fig. 69), feed upon insect food through- out their life. The sparrow family (Fig. 70), on the other hand, choose largely a diet of seeds. Almost every kind of food, however, is eaten by some of the perching birds. 64. Migration of birds. — Some of the birds like the chickadee and downy woodpecker, remain in the middle and northern United States throughout the year, and hence are known as permanent residents of these regions. Many birds, however, spend thé winter Fig. 67.— Male and female bobolink. ae ae Seta s Fig. 68. — Wood thrush. in the warmer regions of the South and in the spring months move northward; some of them, like the robin (Fig. 71) and the blue- bird, build their nests, rear their young, and stay all summer in north- ern and middle United States. Such birds are called summer residents. Still other birds rear their young in Canada and even farther north, and come to us only as winter visitants. This BIRDS 81 Fic. 69.— Kingbird. (Courtesy of National Audubon Society.) seasonal movement of birds is known as migration. Migration is Fic. 70.— Tree sparrow. G (Courtesy of National Audubon Society.) 82 ANIMAL BIOLOGY especially characteristic of the perching birds. For this reason, the birds in this, the highest order, are known as “ birds of passage.” Fie. 71.— The robin. OTHER Date Sizz! ComPaRED C NAME OLOR OF | STRIK- WHEN oe ee to Rosin oR rea Breast pS OF SEEN SpaRRow Cotons Birp Mar. 10, 1912 Lower limbs of trees Larger than | Bright | Reddish | Belly |Blue- sparrow blue | brown | white |bird 66. Field work on birds. — Pupils should become familiar with the size, form, colors, and song of as many birds as possible, and should note carefully where each kind of bird is most commonly found (e.g. in marshes, trees, bushes, or on the ground). In this study bird glasses or opera glasses are very useful. Books like: _ 1 Length of robin from tip of bill to tip of tail feathers, about 10 inches; length of sparrow from tip of bill to tip of tail feathers, about 6 inches. BIRDS 83 Chapman’s “ Bird Life,”’ Wright’s “ Citizen Bird ”’ and “ Birderaft,’’ Hornaday’s ‘‘ American Natural History,” should be frequently consulted. In order to record striking characteristics as a help toward identifying birds, it is suggested that eaeh pupil fill out a table as shown on page 82. 66. Importance of birds to man. — Few animals are more beautiful in form and color than are many of our most com- mon birds, and one of the greatest delights of springtime is to greet the return, of the bluebirds, tanagers, thrushes, and others of our feathered friends. ‘‘ To appreciate the beauty of form and plumage of birds, their grace of motion and musical powers, we must know them. . . . Once aware of their existence, and we shall see a bird in every bush and find the heavens their pathway. One moment we may admire the beauty of their plumage, the next marvel at the ease and grace with which they dash by us or circle high over- head. ... The comingsand goings of our migratory birds in springtime and fall, their nest-building and rearing of young, their many regular and beautiful ways as exhibited in their daily lives, stir within us impulses for kindness toward the various creatures which share the world with us... . But birds will appeal to us most strongly through their song. When your ears are attuned to the music of birds, your world will be transformed. Birds’ songs are the most eloquent of Nature’s voices: the gay carol of the grosbeak in the morn- ing, the dreamy, midday call of the pewee, the vesper hymn of the thrush, the clanging of geese in springtime, the farewell of the bluebird in the fall, — how clearly each one expresses the sentiment of the hour or season!’’ — Quoted from Bulletin No. 3 of University of Nebraska, and from Chap- man’s “ Bird Life.” The value of birds to man as objects of beauty cannot be measured, it is true, in dollars and cents; but were we to 84 ANIMAL BIOLOGY lose the birds, we should realize all too well how much they contribute to the happiness of every lover of nature. When, however, we come to discuss the economic value of birds, the good that they do cannot be overestimated. Biologists have carried on long series of studies to determine accurately the food of different kinds of birds. This has been done by watching them while they are eating or while feeding their young, and by examin- ing the contents of birds’ stomachs. The following paragraphs contain descrip- tions of some of the ways in which birds are of inestima- ble use to man. of 67. Birds as destroyers of harmful insects. — Undoubtedly the greatest value of birds to man is the good that they do in ‘destroying injurious insects. In 13-18, 23, . a, and 46, we have described some of the Fie. 72. — Black : and white warbler, ravages made by our insect foes. “But if insects are the natural enemies of vegetation, birds are the natural enemies of insects. . In the air swallows and swifts are coursing rapidly to and fro, ever in pursuit of the insects which constitute their sole food. When they retire, the nighthawks and whip-poor-wills will take up the chase, catching moths and other nocturnal insects which would escape day-flying birds. Fly-catchers (Fig. 69) lie in wait, darting from ambush at passing prey, and with a suggestive click of the bill returning to their post. The warblers (Fig. 72), light, active creatures, flutter about the BIRDS 85 terminal foliage, and with almost the skill of a humming bird, pick insects from the leaf or blossom. The vireos patiently explore the underside of leaves and odd nooks and corners to see that no skulker escapes. The woodpeckers (Fig. 66), nuthatches, and creepers attend to the trunks and limbs, examining carefully each inch of bark for insects’ eggs, and larve, or excavating for the ants and borers they hear within. On the ground the hunt is continued by the thrushes (Fig. 68), sparrows (Fig. 70), and other birds that feed upon the innumerable forms of terrestrial insects. Few places in which insects exist are neglected; even some species which pass their earlier stages or entire lives in the water are preyed upon by aquatic birds.” 1— From Cuap- MAN’s “ Bird Life.” As examples of the number of insects destroyed by in- dividual birds we may give the following: Six robins in Nebraska ate 265 Rocky Mountain locusts; the stomachs of four chickadees contained 1028 eggs.of cankerworms; 101 potato beetles were found in the stomach of a single quail (Fig. 62); and 250 hairy caterpillars, which other birds do not eat, were devoured by a yellow-billed cuckoo. (Frontispiéce.) 68. Birds as destroyers of weed seeds. — Another way in which birds are useful to man is in the destruction of weed seeds. Most perching birds that feed largely upon seeds, e.g. the sparrows and finches, have stout, conical bills (Fig. 70) which are specially adapted for crushing seeds. In one ef the pamphlets of the United States Department of Agri- culture, entitled ‘Some Common Birds and their Relation 1 Before assigning this section for study each of the birds named should if possible be shown to the class, or at least colored pictures of the birds, e.g. in Chapman’s ‘Bird Life.” ANIMAL BIOLOGY rE sg a & 3} 8 os] a eS 8 oO inal E ° 2 o ee 3s ae ro o s | a ° 2 i=l fo} o ix So & = 3 fea} oo fe} oF o Zz Pe id $ g & graphed by A. E. Rueff of the Brooklyn Institute of Arts & Sciences.) BIRDS 87 to Agriculture,” the writer estimated that in the state of Jowa during the six months of fall and winter, tree sparrows . devoured 875 tons of weed seed. An actual count of the stomach contents of a bobwhite showed the presence of 400 pigweed seeds. In the stomach of another were 500 seeds of ragweed. 69. Birds as destroyers of rats and mice. — We learned in 61 that hawks and owls by their hooked bills and claws are admirably fitted to clutch and tear living prey. It has been demonstrated that the food of many of these birds consists almost wholly of small gnawing mammals (e.g. field mice) (Fig. 64) which are exceedingly injurious in fields of grain. An examination of the stomachs of fifty short- eared owls (Fig. 65) showed that 90 per cent of them contained nothing but mice. Forty of the forty-nine stomachs of the rough-legged hawks were found to contain mice, while most of the rest contained injurious animals. 70. Birds as scavengers. — Some birds of prey, like the turkey buzzards of the Southern states, eat animals that are dead. ‘‘ These animals may be seen at all hours of the day sailing through the air in majestic circles or lazily resting on stumps or trees after a feast of their filthy food. They perform an important service as scavengers, disposing of all sorts of animal matter that would pollute the air. On this account they are seldom molested by man and in some States are protected by law. They devour both fresh and putrid meat. ... They are known sometimes to capture live snakes and to attack helpless animals of many kinds. Along the seashore they feed upon dead fish cast up by the waves.” — WreEp and Drarzorn, “ Birds in their Relations to Man.” Gulls (Fig. 59) also serve a useful purpose by 88 ANIMAL BIOLOGY devouring dead fish and other refuse along our coast line and in our harbors. 71. Birds injurious to man. — We have discussed briefly in the preceding sections some of the ways in which birds are of incalculable value to man. It must be admitted, however, that some birds are of doubtful value, while others are positively injurious. As an example of a bird, which, to say the least, is a nuisance, we may mention the common English sparrow. This bird was first introduced from Eng- land into the United States in Brooklyn, N.Y., in 1851, because it was expected to attack some of our injurious in- sects. These sparrows have multiplied so rapidly that now they are found practically everywhere in the United States. ‘As destroyers of noxious insects, the sparrows are worse than useless.’ Thus, for instance, the stomach of a single cuckoo (Frontispiece) was found to contain more insects than did the stomachs of 522 English sparrows. But even more serious are the positive charges that have been proved against this bird. It pecks at and destroys the young buds of trees, and later injures many fruits while they are ripening. It causes great losses in the grain fields from the time of planting to that of harvesting; and worst of all is the fact that it molests and drives away our native song and insect-eating birds. The crow (Fig. 74) is another bird that on the whole is probably more injurious than beneficial for the following reasons: “ (1) Crows seriously damage the corn crop, and injure other grain crops, usually to a less extent. (2) They damage other farm crops to some extent, frequently doing much mischief. (3) They are very destructive to the eggs and young of domesticated fowls. (4) They do incalculable damage to the eggs and young of native birds. (5) They BIRDS 89 do much harm by the distribution of seeds of poison ivy, poison sumach, and perhaps other noxious plants. (6) They do much harm by the destruction of beneficial insects. On the other hand: (1) They do much good by the destruction of injurious insects. (2) They are largely beneficial through their destruction of mice and other. rodents. (3) They are valuable occasionally as scavengers.” —W. B. Barrows, “The Food of Crows.” Fig. 74. — The crow. While most of the hawks are undoubtedly beneficial (69), two species, namely, Cooper’s hawk and the sharp-shinned hawk, must be kept down to limited numbers. Both of these are “ chicken-hawks,” and in addition they ruthlessly destroy great numbers of our most valuable wild birds. 72. Summary of the relation of birds to human welfare. — Library study. For further facts like the following, consult, Weed and Dear- 90 ANIMAL BIOLOGY born’s “Birds and their Relation to Man,” Forbush’s “ Useful Birds and their Protection,’ Hornaday’s “ American Natural History,” pamphlets of Department of Agriculture (which may be obtained free from Washington, D.C., and from State Departments of Agriculture), and articles on birds and insects in. Encyclopedias. TIME oF Kinp or ANIMAL Kinp oF Name oF Birp Visiigioe | “Wood BAvEn ae Foop REMARES Robin Summer | Insects, 42 | Small fruits Beneficial resid. per cent and berries, mostly wild, 58 per cent Phoebe Summer | Insects Wild fruits, Beneficial resid. caught on 7 per cent wing, 93 per cent Hairy wood-| Perm. | Wood-bor- | Wild fruits Beneficial pecker . resid. ing insects and ants Yellow - billed | Summer | Insects, Beneficial cuckoo resid. largely hairy caterpillars Quail or bob-| Perm. | Insects in | Weed seeds Beneficial white . resid. summer during rest of year Tree sparrow .| Winter Weed seeds Beneficial visit. Bobolink Summer | Insects in Rice in South | $2,000,000 resid. North , loss to rice crop Short-eared owl | Perm. | Rats, mice Beneficial resid. and other small mammals BIRDS 91 NAME OF Birp Piha ee Veornasts Foo acid Sparrow-hawk | Summer | Mice and Beneficial resid. insects Cooper’s hawk | Summer | Poultry and Injurious resid. song birds Sharp-shinned | Summer | Poultry and Injurious hawk . . .| resid. song birds Crow. . . .| Perm. | Insects, Corn and Doubtful resid. mice, other crops, value eggs and weed seeds young of other birds English spar-| Perm. | Insects Buds, fruit, Drives row. . . .| resid. rarely grain away useful birds 73. Causes of decrease in bird life. — Certainly enough has been said to show that when all things are considered birds are exceedingly useful to man. One would therefore expect that every possible means would be taken to protect all kinds of valuable birds. Yet what do we find? ‘“ To- day the first thing to be taught is the fact that from this time henceforth all birds must be protected, or they will all be exterminated. To-day, it is a safe estimate that there is a loaded cartridge for every living bird. Each succeeding year produces a new crop of gun-demons, eager to slay, am- bitious to make records as sportsmen or collectors. If a bird is so unfortunate as to possess plumes, or flesh which can be sold for ten cents, the mob of pot-hunters seeks it out, even unto the ends of the earth.” — Hornapay’s ‘‘The American Natural History.” A careful investigation made in 1897 for the New York Zod- 92 ANIMAL BIOLOGY logical Society showed that during the fifteen years between 1883 and 1898 in all but four states! the number of birds had strikingly decreased. For example, in New York State the decrease was 48 per cent, or almost one half; in Florida it was over three fourths, while the average: for the whole country was 46 per cent. Among the principal reasons given by the 180 careful observers who assisted Dr. Hornaday in the foregoing inquiry were the following: “‘ (1) sportsmen and so-called sportsmen, (2) boys who shoot, (3) market hunters and pot-hunters, (4) plume-hunters and milliners’ hunters, . . . (6) egg-collecting, chiefly by small boys, (7) English sparrow, . .. (9) Italians, and others, who devour song birds.” 74. Destruction of birds by cats. — “‘ As the cat is not an actual necessity, and as it is a potent carrier of contagious diseases, which it spreads, particularly among children, it would be far better for the community if most of the bird- killing cats now roaming at large could be painlessly dis-- posed of... .. Where the cat is deemed necessary in farm or village, no family should keep more than one good mouser, which should never be allowed to have its liberty during the breeding season of birds. . . . Cats can be confined during the day in outdoor cages as readily as rabbits, and given the run of the house at night.’ — Forsusu, ‘“ Useful Birds and their Protection.” 75. Destruction of birds by boys. —One‘of the most serious menaces to our native bird life is the small boy who has the “ egg-collecting fever.” All the eggs he can find in his keen-eyed searches through the woods and fields are ‘Kansas, Wyoming, Utah, and Washington were the only states that showed an increase in bird life. oie ? BIRDS 93 destroyed to increase his collection. If this served any really useful purpose, the resulting wholesale destruction of birds might possibly have some justification. But ninety-nine out of a hundred of these collections are soon forgotten and become useless without having made any real contribution to the knowledge of the possessor. The small boy, too, unfortunately carries his destructive work among birds still further, as the following typical inci- dent will show. A biologist reports meeting near Washing- ton, D.C., ‘one such youngster, and upon examining his game bag found it absolutely full of dead bodies of birds which he had killed since starting out in the morning. One item alone consisted of seventy-two ruby and golden-crowned kinglets. The fellow boasted of having slain over one hundred catbirds that season.” 76. Destruction of birds for food. — In the early days of the white settlements in North America, the game birds like the grouse and duck were abundant and they were of neces- sity killed, as were other wild animals, for food. Later on began the killing of birds for sport. As the forests were cut down, the birds had less and less protection, and had not legislation intervened, the game birds would long since have been exterminated. As it is, they have been killed faster than they breed; and this means ultimate extermination. To this destruction of game birds for food, in more recent, times has been added the wholesale slaughter of many of our smaller birds like the thrushes, sparrows, warblers, and woodpeckers. It is claimed that this has been largely due to the demands of our immigrant population in the North and to the negroes in the South. ‘‘ However, there is scarcely a hotel in New Orleans,” says Professor Nehrling, ‘‘ where small birds do not form an item on the bill of fare. At cer- 94 ANIMAL BIOLOGY tain seasons the robin, wood thrush, thrasher, olive-backed thrush, hermit thrush, chewink, flicker, and many of our beautiful sparrows form the bulk of the victims; but cat- birds, cardinals, and almost all small birds, even swallows, can be found in the markets.” 77. Destruction of birds for millinery purposes. — Even more ruthless than the slaughter of birds for food by boys and by menis that caused by the demand for birds for millinery purposes. Here the final responsi- bility rests upon women alone. A single dealer in the South declared that in the course of a single year he handled 30,000 bird skins, the largest part of which were used in the decora- tion of hats. The Florida egret heron (Fig. 75) has been prac- tically exterminated for Tie Te aah, Dat and Zoees, thie purpose. ‘Twenty years ago,” says Chap- man, “it was abundant in the South, now it is the rarest of its family. The delicate ‘ aigrettes’ which it donned as a nuptial dress were its death warrant. Woman demanded from the bird its wedding plumes, and man has supplied the demand. The Florida herons or egrets have gone, and now he is pursuing the helpless birds to the uttermost parts of the earth. Mercilessly they are shot down at their roosts or BIRDS 95 nesting grounds, the coveted feathers are stripped from their backs, the carcasses are left to rot, while the young in the nest above are starving.” “ This slaughter of the innocents is by no means confined to the Southern states. During four months 70,000 bird skins were supplied to the New York trade by one Long Island village. ‘On the coast line of Long Island,’ wrote i = Nog =A Fic. 76. — Tern. Mr. William Dutcher, not long ago, ‘the slaughter has been carried on to such a degree that, where, a few years since, thousands and thousands of terns (Fig. 76) were gracefully sailing over the surf-beaten shore and the wind-rippled bays, now one is rarely to be seen.’ Land birds of all sorts have also suffered in a similar way, both on Long Island and in adjacent localities in New Jersey. Nor have the interior regions of the United States escaped the visits of the milli- 96 ANIMAL BIOLOGY ner’s agent. An Indianapolis taxidermist is on record with the statement that in 1895 there were shipped from that city 5000 bird skins collected in the Ohio Valley. He adds that ‘no county in the state is free from the ornithological mur- derer,’ and prophesies that birds will soon become very scarce in the state. “ These isolated examples can only suggest the enormous number of birds that are sacrificed on the altar of fashion. The universal use of birds for millinery purposes bears suffi- cient testimony to the fact. Yet it is probable that most women who follow the fashion seldom appreciate the suffer- ing and the economic losses that it involves.” — WEED and Derarsorn, “Birds in their Relations to Man.” 78. Effects of bird destruction. — While the szsthetic loss to mankind resulting from the destruction of our wild birds cannot, as we have said, be computed, yet even in the cities this loss is beginning to be realized as we see the song birds in the parks steadily diminishing in number. Every- one, however, is affected by the increasing cost of our food supply, and we have but to review the facts stated in the preceding sections to show that the destruction of our wild birds has a very important bearing on the present situa- tion. : Every farmer knows that it is impossible to raise the crops of a single year without battling with insect pests. The time and expense involved in applying insect-destroying preparations would be difficult to compute, and even after the year’s contest is ended, the insects are often victorious. In ruthlessly destroying the wild birds man has interfered with the “ balance of nature’’ and so has helped the ravaging hordes of insects and gnawing animals to multiply without adequate check. All this means that we, the consumers of BIRDS 97 the fruits, the vegetables, and the grains, must pay higher prices for the food we eat and the clothes we wear. 79. Conservation of birds. — But it is not yet too late to save the remnant of the birds still left to us, and even to increase the bird life of our country. It is evidently neces- sary, however, in the first place, that laws similar to the following should be passed in every state. “The Bird Law of. the American Ornithologists’ Union. — An Act for the Protection of Birds and their Nests and Eggs. “Section 1.— No person shall within the State of —— kill or catch or have in his or her possession, living or dead, any wild bird other than a game bird, nor shall purchase, offer, or expose for sale any such wild bird after it has been killed or caught. No part of the plumage, skin, or body of any bird protected by this section shall be sold or had in possession for sale. Section 2. — No person shall within the State of —— take or needlessly destroy the nest or the eggs of any wild bird nor shall have such nest or the eggs in his or her possession. . . . “ Section 3.—— Any person who violates any of the provisions of this act shall be guilty of a misdemeanor, and shall be liable to a fine of five dollars for each offense, and an additional fine of five dollars for each bird, living or dead, or part of bird, or nest and eggs pos- sessed in violation of this act, or to imprisonment for ten days, or both, at the discretion of the court. “Section 4. — Sections 1, 2, and 3 of this act shall not apply to any person holding a certificate giving the right to take birds and their nests and eggs for scientific purposes, as provided for in Sec- tion 5 of this Act... . — “ Section 7.— The English or European house sparrow (Passer domesticus) is not included among the birds protected by this act.” “In addition to the above, every state that has not already done so, should at once enact laws to prohibit the sale of all wild game at all seasons, and to stop all shooting H 98 ANIMAL BIOLOGY of game in late winter and spring. About one half the states have done this, and the other half should act without delay. The sale of game has almost destroyed our once magnificent supply of game birds. We have no right to hand down to posterity a gameless continent. The wild life of to-day is not wholly ours to dispose of as we please. It has been given to us in trust. We must account for it to those who come after us and audit our records.” ! — Dr. W. T. Hornapay. But laws, however stringent, are of little avail unless there is a healthy public sentiment to bring about their enforce- ment. Thus, for instance, it is evident that laws merely de- signed to prevent the killing of birds for millinery purposes will be ineffective, so long as women are permitted to wear birds. One thing will completely stop the cruelty of bird millinery —the disapprobation of fashion. “It is our women who hold the great power. Let our women say the word, and hundreds of bird lives will be preserved every year. And until woman does use her influence it is vain to hope that this nameless sacrifice will cease until it has worked out its own end and the birds are gone.” — WEED and Drargorn, “ Birds in their Relations to Man.” 80. What boys and girls can do to protect birds. — ‘‘ Now that adequate statutes are either enacted or may reasonably be expected very soon, it remains to scatter information about birds everywhere, so that laws may be respected. . . and it is in this line that those interested in their conservation should work. There must be lectures, short articles of a popular nature in newspapers and magazines, distribution of government and other publications relating to birds, 1 The authors are indebted to Dr. W. T. Hornaday, of the New York Zodlogical Park, for many suggestions relating to conservation of birds and for a careful reading of the chapters on birds and fishes. BIRDS 99 posting bird laws in conspicuous places, and most important of all, systematic bird work in public schools. The impor- tance of engaging the interest of our youth in birds cannot be overestimated. It results in a double benefit, for the birds will be held in higher esteem and the children will become possessed of a source of lasting pleasure. The nest- robbing, bird-shooting boy and the feather-wearing girl may be made the friends and allies of the birds.” — WrxEp and Drarsorn, “ Birds in their Relations to Man.” But not only should the boy cease to destroy nests and shoot birds; not only should the girl cease to wear any part of a wild bird; but boys and girls alike should do all they can to induce others to do_ likewise. Much may also be done, likewise, even in the vicinity of large towns, to attract birds and induce them to nest. In the first place, the nests and eggs of the English sparrow should be destroyed whenever found. Stray cats should be kept from harming birds. Pieces of meat, bones, and suet, when hung in the trees in winter time, and crumbs and grains scattered about, will serve to attract the winter visitants and, when thus at- tracted, these birds devour great numbers of the eggs and insects in the hibernating stages that during the follow- ing season would attack the fruit and shade trees. And finally, any ingenious boy can construct and put in the trees bird houses that in the springtime would become the Fic. 77.— Bird house made by a twelve- year-old boy. ent 100 ANIMAL BIOLOGY nesting places of bluebirds, wrens, tree swallows, and martins.! (Fig. 77.) 1For other methods of encouraging birds see Weed and Dear- born, ‘‘ Birds in their Relations to Man,” pp. 304-315. Trafton, ‘‘Methods of Attracting Birds,”’ and leaflets of National Associa- tion of Audubon Societies, 1974 Broadway, N. Y., e.g. No. 16 (Win- ter Heeding of Wild Birds) and No. 18 (Putting up Bird Boxes), 1 cent each. CHAPTER, IIT FROGS AND THEIR RELATIVES 81. Study of the frog. — Laboratory study. A. Regions and appendages. — The frog’s body consists of two principal parts, or regions ; namely, the head and trunk. The line of union between the two regions is just in front of the anterior append- ages (arms). 1. Locate the appendages (arms and legs) attached to the trunk. 2. Name and locate the organs that you find on the head, giving the number of each. B. Breathing organs. 1. Describe the location of the nostrils on the head. 2. Examine a preserved specimen in which a stiff bristle has been passed through one of the nostrils. a. Tell what was done. b. Into what cavity has the bristle emerged ? c. (Optional.) What is one difference, therefore, between the nostrils of a fish and of a frog? d. In what region (anterior or posterior) of the roof of the mouth cavity are the inner openings of the nostrils located ? 3. (Demonstration.) Just back of the tongue there is a narrow opening that leads into the windpipe (trachea). This opening is called the glottis. a. Locate the glottis. b. Does the glottis extend lengthwise or crosswise of the mouth cavity? c. Into what does the glottis open? 4. Examine a dissected frog prepared in such a way as to show the lungs. 101 102 ANIMAL BIOLOGY a. State the location of the lungs with reference to the head and the cavity of the trunk. b. Describe the appearance of the lungs. c. Insert the end of a glass tube, that has been drawn out to a small diameter, into the glottis opening and blow air into the lungs. Describe what you have done and state the result. 5. Name in order the openings, the cavity, and the tube through which the air must pass in order to reach the lungs. Breathing movements. 1. Place a frog in a glass jar with an inch or two of water and watch the action of the floor of the mouth. This is one of the breathing movements. De- scribe this breathing movement of the frog. 2. There are two breathing movements of the sides of the trunk, one a very active inward and out- ward movement, and the other a very slight inward and outward movement. When you have seen these two kinds of movements of the sides, describe them and state which kind occurs the more frequently. How the frog exhales. 1. What effect will the active inward movement of the sides have upon — 7 a. The size of the body cavity? b. The size of the lungs? c. The pressure of the air in the lungs? 2. When the sides of the trunk move actively inward, will the air move into the lungs or out? Why? 3. Through what passages will the air go from the lungs to the outside of the frog? How the frog inhales. : 1. When the floor of the mouth moves downward — a. Will the size of the mouth cavity be made larger or smaller? b. FROGS AND THEIR RELATIVES 103 If the nostrils are now open will the air move into the mouth cavity or out? Why? 2. When the floor of the mouth is raised — a. b. C. d. Will the size of the mouth cavity be increased or decreased ? Will the pressure of the air in the mouth cavity be increased or decreased ? If .both the nostrils and the glottis are now open, in what directions will air be forced ? What causes the slight outward movements of the sides of the trunk in the region of the lungs? F. How the lungs are fitted for breathing organs. (Suggested as home work.) When the lungs are inflated (see B, 4 above) they look like bags (Fig. 80). The lungs are hollow, and their walls are composed of thin material. In these membranous walls are thin- walled blood vessels known as capillaries. The heart forces blood that has come from the body into these capillaries of the lungs, and then back to the heart. Bearing in mind that respiration in animals is essentially the same as in plants (P. B., 82) — 1. State what waste substance the blood brings to the lungs to be given off from the capillaries. 2. What gas will the blood in the capillaries take up from the air in the lungs? 3. How are the walls of the lungs and of the capillaries of the lungs fitted by structure to make this interchange of gases possible? G. Food-getting. To the Teacher. — Select a number of as large pre- served or freshly killed frogs as you can get. Open the jaws as far as possible and keep them in this position by means of small pieces of wood. 104 ANIMAL BIOLOGY 1. Seize the posterior or hind end of the tongue and pull it forward. a. Tell what you have done and state which end of the tongue is attached to the floor of the mouth. b. Describe the shape of the tip end of the tongue. 2. The living frog can extend its tongue much farther than you have been able to do in the case of the preserved frog, and in the living frog the tongue is covered with a very sticky substance. The tongue is used to catch insects at some distance from the animal (Fig. 79). Tell how you think the frog could use its tongue to catch insects and get them into its mouth.! 3. Look for teeth on the jaws of a skeleton of a frog, or if you cannot obtain a skeleton, rub the finger over the jaws of a preserved specimen. a. Which of the jaws has teeth? b. Describe the location of the teeth on the jaw. c. State the shape and size of the jaw teeth. d. What is the probable use of the jaw teeth? 4. (Optional.) Look on the roof of the mouth for two rela- tively large palate teeth. Rub the fingers over the surface of the palate teeth. a. Tell what you have done. b. What have you found out about the palate teeth? c. What is the probable use of thé palate teeth? H. How a frog swallows. 1. Gently touch the eyes of a living frog until it draws them into the head. Tell what you have done and observed. 2. Look at the roof of the mouth of a preserved speci- men while you push the eyes into the head. Tell what you have done and describe the effect produced in the roof of the mouth. 3. How will the act of pushing the eyes into the head be useful to a frog in swallowing?! _ lIf possible live frogs should be fed on meal worms, or other insects, and the feeding movements observed. FROGS AND THEIR RELATIVES 105 ‘I. (Optional.) Sketch of the mouth cavity. 1. Open wide the mouth of a large frog and make a sketch to show the shape of the mouth cavity twice the natu- ral size, and the shape and thickness of the upper and lower jaws. 2. Draw the following parts to show their location, size, and shape: jaw teeth, palate teeth, tongye, glottis, nostril openings, swellings caused by the eyes. 3. Farthest back in the throat find an opening that extends crosswise. It is the opening into the gullet and is just behind the glottis. Push the handle of the forceps into this opening and draw it (in your sketch) partly opened. 4, Label upper jaw, lower jaw, jaw teeth, palate teeth, tongue, glottis, opening of gullet, nostril openings, swellings caused by eyes. J. Structure of arms and leg Place a frog in a glass jar at least half full of water to cause the animal to extend the hind legs. 1. Make a sketch (natural size) of an arm to show the shape and size of the following parts: upper arm, elbow, forearm, hand, number of fingers. Label each part. 2. Draw one of the legs (natural size) to show the follow- ing parts: thigh (next the body), knee, shank, ankle (elongated region above foot), foot, toes, web between toes. Label each part. K. How a frog swims. Place an active frog in a sink or other receptacle large enough to afford it room to swim. The water should be deep enough so that the frog will not strike the bottom with the legs. Get the frog to swim the full length of 106 ANIMAL BIOLOGY the receptacle as many times as may be neces- sary to answer the following : — Tell what you have done. Describe the movements of the hind legs in swimming. In which of these movements are the toes spread out? In which of these movements, therefore, can the frog get the best hold upon the water? In which direction must the frog push the harder in order to move in the direction that it does? In what respects are the posterior appendages well fitted for swimming? In what respects are the anterior appendages not as well fitted as the legs for swimming? PS ob RAINE L. How a frog jumps. Place a frog where there is plenty of room, and get it to jump as many times as necessary to answer the following : — 1. Tell what you have done. 2. Describe the position of the parts of the legs just before the frog jumps. 3. Describe the two movements made by the parts of | the leg in the act of jumping and when about to land. 4. In which of these two movements must the frog use the greater force? 5. Which movement, therefore, throws the frog into the air? 6. In what respects are the legs better adapted for jump- ing than the arms? N. Internal organs. To the Teacher. — Put into a covered jar enough frogs to supply each two students with a specimen. Put into the jar some ether, or better, saturate a small sponge with the ether and place it in the jar. When the animals are dead, dissect them as follows: lift up the skin of the ventral wall of the abdomen with FROGS AND THEIR RELATIVES 107 the forceps ; carefully insert the point of the scissors near the posterior end of the trunk, and carefully cut forward on one side of the body as far as the tip of the head, and back on the other side of the trunk, until the skin is completely removed from the ventral surface. In a similar manner remove the muscular wall that covers the trunk, being careful not to injure the internal organs. If time allows, remove also the skin from one leg; call attention to the thinness of the skin and to the underlying blood vessels ; show the chara¢teristics and action of the leg muscles. If the specimen isa female, remove nearly all the eggs and throw them away. Insert a blowpipe in the glot- tis and partly inflate the lungs. Wash the specimens thoroughly to remove all traces of blood and cover them with water in a dissecting pan. If the specimens are needed on successive days, they should be wrapped in a wet cloth immediately after the class work of each day and kept in a cold place. Use only specimens that are fresh. 1. Make an outline drawing, natural size (or twice natural size if the frogs are small), of the ventral view of the head and trunk regions of a dissected specimen, together with the base of each of the four appendages, and draw nothing else until directed to do so. 2. The heart is a cone-shaped body midway between the arms. Draw the heart to show its position, shape, and relative size. 3. On either side of the heart are the lungs. Stretch one of them a little by pulling on it ; then letting it go. a. State whether or not the lungs are elastic. Are they hollow or solid? Of what advantage are these two characteristics of structure? b. What is the color of the lungs? State whether or not you find tiny blood vessels on the sur- face. 108 ANIMAL BIOLOGY c. Draw the lungs in position to show their situation, size, and shape. . On the frog’s right side, and behind the heart and lungs is the reddish, several-lobed liver. Lay the liver over to one side and find between the lobes on the underside a thin-walled, green sac, the bile sac (or gall bladder). Sketch in your drawing the liver to show it in this position together with the gall bladder. . On the frog’s left side and under the liver in its natural position is a whitish, oblong body, which narrows at its hinder end. This body is the stomach. Push the handle of the dissecting needle down the gullet into the stomach. a. Tell what you have just done. b. What organ does the handle enter? c. Push.the stomach to the frog’s left and draw it in this position to show its shape and relative size. . Extending from the stomach is a tubular structure of considerable length, the small intestine. At the lower end of the small intestine the tube becomes Jarger and then disappears between the two thighs. This last part of the tube is called the cloaca or large intestine. Draw the small and large intestines. . Between the stomach and the first loop of the small intestine is a thin pink body, the pancreas, which is a very important digestive gland. Draw the pancreas. . Label heart, lungs, liver, stomach, small intestine, large intestine, bile sac, pancreas. . Push the small intestine to one side and find two red bodies on either side of the spinal column. These bodies are the kidneys. The kidneys remove the nitrogenous waste (urea) from the blood. — Make a sketch of the kidneys twice the natural size. FROGS AND THEIR RELATIVES 109 82. Habits of frogs. — There are many kinds of frogs, differing from one another considerably in size and color; but all frogs live in places where water is more or less abundant. Frogs are often found either on the banks of ponds and streams, or floating on the surface of the water with only the tip of the nose above water (Fig. 78). In color they usually resemble their surroundings rather closely, and so secure a certain degree of protection from fishes, snakes, birds, and Fic. 78. — Frogs in their habitat. Four frogs are shown; in the middle of the picture a black snake is preparing to seize the frog. (Part of ar. oxhibit at American Museum of Natural History.) man, which are their more common enemies. When pur- sued, they quickly disappear beneath the water and often bury themselves in the mud at the bottom until the need of air compels them to return to the surface. Late in the autumn they burrow in the mud and remain there until the following spring. The more or less pointed snout of the frog, its slippery skin, its long, muscular legs, and its webbed feet all adapt the animal for rapid swimming through the water. 110 ANIMAL BIOLOGY 83. Food, food-getting, and digestion. — Frogs feed upon insects, fish, and other frogs, and even birds have been found in their stomachs. Insects are caught by the aid of the slimy tongue, the tip of which can be quickly thrust out of the mouth and then drawn back again with the insect adher- ing to it (Fig. 79). The tiny teeth that are found on the upper jaw and the two large teeth in the roof of the mouth are useful only in preventing the escape of the prey from the mouth. Hence the food is swallowed without being chewed, and after passing down the short gullet it enters the tubular stomach (Fig. 80), where it is partially digested by ferments (P. B., 58) secreted by certain cells found in the lining of this organ. When the food leaves the stomach, it enters the coiled small intestine where the process of digestion is continued by the bile secreted in the liver and the Fic. 79.—The method pancreatic juice prepared in the pan- by which @ frog se creas As the digested food slowly moves along the small intestine, it is absorbed by the capillaries (84) in the walls of this tube and so may be carried by the blood to the various cells of which the body is composed. Digestion not only prepares the food for absorption, but as in plants (P. B., 51) or in the fish (98), makes it ready to be used in the cells either for growth and repair or for the production of energy. 84. Blood and circulation.— The blood of the frog, when examined under the microscope, is seen to consist A 1Both of these digestive fluids are carried to the intestine by ucts. FROGS AND THEIR RELATIVES 111 of two kinds of cells (the red and white corpuscles) which are floating in a liquid known as plasma. The plasma con- sists largely of water and the digested foods that have been absorbed from the alimentary canal (83). As in the fish, the circulatory system consists of the heart and three kinds of blood vessels; namely, arteries, veins, and NOYAL Wanewy vat Vung, « . ’ VASE SRETmMary / SEMAN Cord : 1 Awkturnal ~o SVAN VRANCTLAS we \ ral i . smal\"cateAine Fre. 80. — Internal organs of the frog. capillaries. The heart is located in the body cavity just back of the head and consists of two auricles and a ventricle (Fig. 81), instead of a single auricle and ventricle as in the fish (Fig. 100). As might be expected, this makes necessary other differences in the circulatory system of the frog. In the fish we shall see that there is only one stream of blood flowing into the heart, while in the frog there are two. One stream enters the heart from the various organs of the body which the blood has supplied with food and oxygen, and from which the blood has received carbon dioxid. The second blood 112 ANIMAL BIOLOGY stream comes from the lungs where the blood has given off the carbon dioxid and received a fresh supply of oxygen. The right auricle receives the blood brought from the body in three large veins, while two small veins carry into the left auricle the blood from the lungs. Artery toleft fling and. Shin “nd. He in OUD as _Artery toleft arm Fight auricle --------; Hs Sl. .Left auricle Artery torieht a1" ( RL | AJA \- Ventricle Right lung ---+--- Arteries to live, woh = ---- stomachéintesines | = fee \ paaias te -T kanes Jo Kidneys “ARse Arteries lo legs Fia. 81. — Arteries in the circulation of the frog. The blood from both auricles now flows into the single ventricle, which then contracts and pumps the blood into a large artery. Certain branches carry the blood having the larger amounts of oxygen (i.e. the blood from the lungs) to the head, trunk, legs, and other organs of the body, while other branches carry the blood just received from the body, FROGS AND THEIR RELATIVES 113 with its larger amount of carbon dioxid, to the lungs and the skin. In the capillaries which connect the arteries and veins in every part of the body (Fig. 82) all the changes in the com- position of the blood take place, since their thin walls per- mit the food materials and oxygen to enter the cells and the wastes from the cells to enter the blood.!. The capillaries in the lungs likewise permit the interchange of oxygen and carbon dioxid. ve Fic. 82. — Network of cap- ‘ illaries connecting an ar- Dae ia deep waded ei. Fig. 83. Bae ari in web of 85. Respiration and the liberation of energy. — The walls of the frog’s lungs contain a network of capillaries, and in these thin-walled tubes the red corpuscles absorb the oxygen that is forced into these sacs by the upward movement of the floor of the mouth. As we have seen, the blood with a fresh supply of oxygen flows from capillaries of the lungs into 1A tadpole’s tail is excellent for demonstrating the blood current. Wrap a tadpole in wet cloth or cotton and support it so that the tail can be placed between two glass slides on the stage of the micro- scope. The space between the two slides should be kept filled with water. The movement of the corpuscles through the margin of the tail should be examined with the low power of the micro- scope (Fig. 83). I 114 ANIMAL BIOLOGY veins and so finally into the left auricle and thence into the ventricle. Here it tends to become somewhat mixed with the blood from the right auricle which has just returned from the body. However, the structure of the heart and the ar- teries is such that the blood that has come from the lungs with a larger supply of oxygen is sent out by arteries to all parts of the body. In the capillaries the oxygen is absorbed by the cells. Oxidation of the food and protoplasm takes place and en- ergy is thereby released, which enables the frog to carry on locomotion, secure its food, and perform all its destined tasks. The carbon dioxid and other wastes produced by oxidation pass through the capillary walls into the blood and, as we have seen, are carried back to the heart and then to the lungs, where carbon dioxid is excreted. Other wastes are excreted by the kidneys. The skin of the frog is likewise permeated by a network of capillaries so that it acts as do the gills of fishes in ab- sorbing oxygen from the water and in giving off carbon dioxid. While the frog is buried in the mud during the winter it breathes entirely through the skin. So much does the frog depend on the skin as a breathing organ that even in summer, if the skin becomes dry so that air cannot be ab- sorbed, the frog dies. 86. Reproduction and life history.—In the animals studied thus far we have found special organs devoted to the process of reproduction, namely, ovaries for egg production in the female and in the male spermaries that form the sperm-cells. Before the egg-cells can develop into embryos each must be fertilized by a sperm-cell. All the facts we have just stated apply equally well to the frog. Frogs’ eggs are deposited in springtime in masses that FROGS AND THEIR RELATIVES 115 ig C, egg con- . A, eggs before B, eggs after they taining young D, young tadpoles attaching they are laid are laid tadpole themselves to a plant £, young tadpole withex- F, young tadpole with ternal gills internal gills G, young tadpole with hind legs H, tadpole with webbed feet I, tadpole with legs and arms J, young frog Fic. 84. — Life history of frog. O Oo & A, one-celled stage B, two-celled stage C, four-celled stage _D, eight-celled stage E, sixteen-celled F, thirty-two G, sixty-four H, many-celled stage celled stage celled stage stage Fic. 85.— Cell division in a frog’s egg. 116 ANIMAL BIOLOGY float on the surface of the water! (Fig. 84, B). Each fertil- ized egg is a small sphere, black on its upper surface and white beneath, and inclosed in a gelatinous covering. The warmth of the sun causes the one-celled egg to divide verti- cally in half to form the two-celled stage (Fig. 85, B) and the process of division continues until the egg consists of many cells (Fig. 85, H). Food for the development of the embryo is stored in the egg. The many cells of the egg gradually become different in character and so form the various organs of the embryo (Fig. 86). Soon after hatching, the young of the frog, known as tadpoles, secure their food by sucking in tiny water plants Pee Pee ae found on the surface of plants re : and stones (Fig. 84, D). Tad- poles resemble fishes in having gills for breathing, a heart with two chambers instead of three, and a tail for locomotion. At first the gills are on the outside of the body (Fig. 84, £), but later four pairs of internal gills are formed, and the external gills are absorbed. The animal increases in size, the hind legs appear, and the arms are formed beneath the skin. Meanwhile the lungs are being developed, the heart becomes three cham- bered, the legs grow larger, arms appear, and finally the gills and the tail are completely absorbed. The tadpole now leaves the water, since it is an air-breathing animal. This succession of changes after hatching from the egg is known as a metamorphosis. 87. Relatives of the frog. — Much like the frog in structure and life history is the common garden toad. Toads, however, in their 1If possible eggs in different stages of segmentation should be se- cured, preserved in 5 per cent formalin, and used for demonstration. FROGS AND THEIR RELATIVES 117 adult stage cover themselves more or less with dirt in the daytime, and come out at night to feed upon insects, which constitute their sole food. Instead of having a smooth, slimy skin, as does the frog, a toad’s skin (Fig. 87) is dry and covered with elevations com- monly known as “ warts.” These elevations contain cells which secrete an irritating substance that protects the toad from animals Fig. 87.—The toad. Note its resemblance to its surroundings, whereby it is likely to be protected. that would prey upon it. There is no foundation, however, for the popular notion that the warts of human beings are ever caused either by toads or frogs. : In springtime toads seek the water in which to breed. The eggs, covered with a gelatinous substance are laid in long strings instead of in masses, as was the case with frogs. The development and life 118 ANIMAL BIOLOGY history of the toad is much the same as in the case of the frog. As soon as metamorphosis is complete, the little toads leave the water and often are found considerable distances away from water. Less like the frog, at least in its adult stage, are the salamanders and newts (Fig. 88). These are found in damp places or in Fic. 88. — The newt. water and are often called “lizards,” by those who do not know that a lizard has scales, claws on its feet, and breathes throughout its life by means of lungs. Some of the relatives of the frog, even after they have developed lungs, retain gills throughout their life (Fig. 89). GE _ FE Fic. 89. —A mature amphibian (Necturus) with external gills. Because of the ability of the animals described in this chapter to live both on the land and in the water, they are called the amphibia, from Greek amphi = both + bios = life. 88. Economic importance of the amphibia. — None of the amphibia, so far as is known, are harmful to man. On the contrary, all of them are more or less useful because of the insects that they devour. This is especially true of the garden toad. It has been estimated by one author that a toad in a garden is worth nearly twenty dollars a year on account of the cutworms and other injurious insects that it destroys. “In France the gardeners even buy toads to aid them in FROGS AND THEIR RELATIVES 119 keeping obnoxious insects under control.’ — Hr@ner’s “ Col- lege Zodlogy.”’ Frogs, in addition to their value as insect destroyers, are also of some value to man as food. It is said that in the United States about $50,000 is obtained annually by the frog hunters for their catch, and frog farms are now profitably maintained in several states. Frogs are also used as fish bait. CHAPTER IV FISHES 89. What is a fish ?—‘“‘A fish is a backboned animal which lives in the water and cannot ever live very long anywhere else. Its ancestors have always dwelt in water, and likely its descendants will forever follow their example. So, as the . anterior seostev Vor Aorsar Sin Agv Sat Sin Lee ae ar Gere Ny svn. wad&—'—$_Arunk sil Fie. 90.— Yellow perch. water is a region very different from the fields or the woods, a fish in form and structure must be quite unlike all the beasts and birds that walk or creep or fly above ground, breathing air, and being fitted to live in it. There are a 120 FISHES 121 great many kinds of animals called fishes, but in this all of them agree: all have some sort of a backbone, all of them breathe their life long by means of gills, and none have fingers or toes with which to creep about on land.” ! 90. The regions and appendages of a yellow perch. — Study Figure 90 and notice that the body of the yellow perch is divided into three regions; namely, head, trunk, and tail. Unlike the body of many animals, no neck is present, and the head, therefore, is joined directly to the trunk. The line of union of head and trunk is the posterior? margin of movable flaps, called the gill covers, on the sides of the head. Just behind or posterior to the gill cover on each side of the trunk of the fish is a paddle-like organ called the pectoral fin. On the ventral surface, below the pectoral fins, is a second pair which are known as the pelvic fins. The pectoral and pelvic fins are together known as the paired fins of the fish. Besides these this animal has several unpaired fins, which we shall now locate. On the dorsal surface notice two dorsal fins, one behind the other, which project upward. Below the posterior dorsal fin, on the ventral surface, is another single fin called the anal fin. The tail region is considered to begin just in front of the anal fin, since in the fish the body cavity that contains the important organs of digestion, circulation, and reproduction ends at this point (Fig. 98). The anal fin, therefore, and also most of the posterior dorsal fin, are attached to the tail region. At the posterior end of this third region is the broad forked tail jin. 91. Regions and appendages of a goldfish. — Laboratory study. 1 Jordan’s ‘‘ Guide to the Study of Fishes,’ Vol. I, p. 3. 2The meaning of each of these terms is explained in 6. 122 ANIMAL BIOLOGY Materials: A living goldfish in a battery jar for each ivo students. Goldfish may be kept indefinitely in a glass jar with green water plants; the latter supply the fish with food and oxygen. Perch, and if possible the heads of large fishes like the cod, should. be obtained, preserved in formalin (5 per cent), and then thoroughly washed in running water for twenty-four hours before they are used ; materia] treated in this way loses its fishy smell, and may be kept in the formalin solution year after year. A fish skeleton is also needed for demonstration. The Jung charts of the external and internal structure of the perch are useful. Observe a living goldfish and compare it with Figure 90. 1. Name the regions of its body and state, with reference to gill cover and fins, where each region begins and ends. Name and locate all the organs you find on the head. 3. What paired and what unpaired fins are found on the trunk? Using the terms anterior, posterior, dorsal, ventral, median, and lateral, locate each of these fins. 4. Name and locate the fins attached to the tail region of the body. 5. Make an outline sketch about five inches long of the side view of a living goldfish to show the shape and relative size of the three re- gions, the position and shape of the organs of the head and of the various kinds of fins. Label the regions and the organs that you have drawn, in a manner similar to Figure 90. Le 92. Some differences in the form of fishes. - — One can usually tell whether or not an animal is a fish; but in some cases this is Fig. 91.—Sea horse. FISHES 123 extremely difficult. Who would think, for instance, that such ani- mals as the sea horse (Fig. 91) and the pipefish (Fig. 92) would be Fig. 92. — Pipefish. classed with the perch and goldfish? Yet such is the case, since careful study has shown that these forms have all the charac- teristics mentioned in 89. dorsal fin i) i) anal fin pelvic fin Fic. 93. — Flounder. It is evident that the goldfish and perch have bodies that are considerably longer than they are wide or deep, and this is true of most of the common fishes, In the group of fishes known as the eels, 124 ANIMAL BIOLOGY this elongation is so marked that they look more like snakes than they do like fishes. But the eels are not the only fishes that show a striking development in one dimension. The flounders, for example (Fig. 93), exhibit a notable growth in a dorso-ventral direc- Fic. 94.—Sting ray. (Jordan and Evermann. Courtesy of Doubleday, Page & Co.) tion. So far has this been carried that the fish is unable to retain a vertical position, and consequently lies on one of its sides. The eyes, which, in very young flounders, are situated like those of the goldfish, on either side of the head, by a twisting of the bones of the Fie. 95.— Mackerel. (Jordan and Evermann. Courtesy of Doubleday, Page & Co.) skull, both come to lie on the same side of the head. Otherwise, as may be seen, one of the eyes would rest on the sand or mud, when the animal is on the sea bottom. Fishes like the skates and sting rays (Fig. 94) have also a much flattened body, but these animals have FISHES 125 attained this condition by growth from side to side, instead of dorso-ventrally. 93. Some differences in the fins of fishes. — We have seen that the goldfish has one dorsal fin, the perch two, and that both fishes have a single anal fin. A glance at Figure 108 will show that the cod- fish has three dorsal fins and two anal fins. Dorsal and anal fins vary not only in number, but in extent. In some fishes they are very short, as in the mackerel (Fig. 95), while in the flounder (Fig. 93) these fins extend nearly the whole length of the dorsal and ventral surfaces. Most common fishes possess both pectoral and pelvic fins, but in the eels (Fig. 96) the pelvic fins are entirely wanting and the pec- Fic. 96.— Eel. (Jordan and Evermann. Courtesy of Doubleday, Page & Co.) toral fins are very small. The paired fins vary in position as well. In the perch, for example (Fig. 90) the pelvic fins are immediately below the pectorals, while in the cod (Fig. 108) they are anterior to the pectoral fins, and in the salmon (Fig. 107) they are even farther back on the body than in the goldfish. 94, Adaptations for swimming. — Laboratory study. 1. Carefully watch for a time a goldfish when it is swimming around in a large battery jar or aquarium. a. Which of the three regions of the body is principally used in pushing the animal forward? b. Describe the movements of this body region. 2. Which of the paired fins are used in swimming? De- 126 ANIMAL BIOLOGY scribe their movements. State whether or not you see the fish swim backward. 3. If the goldfish strikes backward with the fins against the water, would the fish tend to move forward or backward? 4. Since the goldfish moves the fins both backward and for- ward in the water, in which direction must it strike the harder and more swiftly if it wishes to swim forward? 5. (Optional.) Suppose the fish strikes backward harder with the fins on the right side than it does with those on the left side, how would the direction of its motion be affected? 6. (Optional demonstration.) Place the largest goldfish you can get, in a sink or other large receptacle full of water. Get the fish to swim continuously and rapidly, but not so rapidly that the pupils are unable to see the paired fins. a. What have you seen that leads you to think that the goldfish does not use the paired fins in rapid swimming? b. What parts does the animal use to drive itself rapidly through the water? 7. Why are the broad, flat surfaces of the fins of advantage to the fish in swimming? 8. Study the anterior, dorsal fin of a perch or other fish. Notice that it is composed of stiff fin rays and of thin connecting membrane. Alternately spread out and close the fin, and bend each of the materials of which it is composed. Now describe the struc- ture of this fin. 9. Examine carefully each of the fins of a goldfish. a. State whether or not each consists of fin rays and connecting material. b. What disadvantage to a goldfish in swimming would result from the absence of the rays in a fin? c. State the relative difference in the size of a fin when it is spread open and when it is closed. d. What would be the disadvantage if the open fin had no connecting membrane? FISHES 127 95. The locomotion of fishes. — Many fishes, like the goldfish and perch, are able to maintain a given position in the water while at rest. This is made possible by means of an internal organ known as the swim bladder (Fig. 98). The swim bladder may be compressed, permitting the fish to sink, or it may be expanded, causing the animal to rise. Since, therefore, the fish is poised in a liquid medium, it is only necessary to overcome the resistance of the water about it in order to move in any given direction. This resistance is more easily overcome, first, because the head is somewhat pointed like the prow of a boat, secondly, because the overlapping scales point backward, and third, because the whole body is covered with a slimy mucus. One who is at all familiar with a canoe knows that it is impossible to propel it by the use of a slender rod. One must have a paddle with the lower end broad and flat so that sufficient force may be exerted against the water to propel the canoe. Now, in swimming, the fins of a fish act more or less like paddles. Their broad, flat surfaces press against such an amount of water that the fish is enabled to exert enough force to push its body in any desired direction. If one watches a goldfish swimming slowly about in an aquarium, one would think that the paired fins, especially the pectoral fins, were the important swimming organs. But careful experiments have shown that this is not the case. When the goldfish has occasion to move more rapidly, the paired fins are not used at all, but are pressed close to the sides, the body being driven through the water by the movement of the tail and tail fin. The paired fins, to- gether with the dorsal and anal fins, seem to be used prin- cipally in steering the fish. The energy necessary for swimming is developed in the powerful muscles of the tail and trunk. : 128 ANIMAL: BIOLOGY 96. Adaptations for food getting. — Laboratory study. 1. Open the jaws of a fresh or of a preserved fish. (Fish of large size, e.g. cod, should be used if possible, the jaws being held wide open with pieces of wood.) Look for teeth on the jaws and the roof of the mouth. a. State the location of the teeth and give some idea of their number. b. Rub the fingers gently back and forth over the teeth. Do they point backward or forward? How do you know? Describe any other characteristics of the teeth. c. Of what use would the teeth be in catching other fish for food? d. Why would the shape of the teeth make them of no use in grinding food? 2. Drop some fish food into a jar containing living goldfish.1 Describe all the movements that you see the fish make while feeding. 97. Food ard food getting among fishes. — Unlike plants, fishes cannot make their food from materials found in the water, air, and soil, but must secure it ready-made from plants or other animals. The goldfish, for example, de- pends largely on vegetable food, while the cod? and the perch for the most part feed upon other animals smaller than themselves. Since these fishes must catch and hold their prey, their jaws are provided with many sharp teeth that point backward, and so prevent the escape of any active 1Tf none of the fish eat readily, this experiment should be deferred. 2 “The cod is omnivorous, and feeds upon various kinds of ani- mals, including crustaceans, molluscs, and small fishes, and even browses upon Irish moss and other aquatic vegetation. All sorts of things have been found in cods’ stomachs, such as scissors, oil eans, finger rings, rocks, potato parings, corn cobs, rubber dolls, pieces of clothing, the heel of a boot, as well as other new and rare specimens of mollusks and crustacea.’”’ — Jonpan and EVERMANN, “American Food and Game Fishes.” FISHES 129 animal which may have been caught. The cod, as you may have seen, has teeth in the roof of the mouth and in the throat in addition to those found on the jaws, thus making more secure its hold upon the unfortunate denizen of the deep that it has seized. . Certain fishes depend on minute forms of plants and ani- mals, and therefore some means is needed by which the water taken in with the food may be gotten rid of while at the same time the food is retained. Hence, fishes are provided with a straining apparatus which permits the water to escape when the mouth is closed, and retains within the mouth the minute forms of life that it has secured. Of this adapta- tion for food getting, we shall learn more in our study of the gills. Most of the fishes that prey on other animals secure their victims by dint of their speed; but one form of fish, called Fig. 97. — Deep sea angler. the “deep sea angler” (Fig. 97), has upon the dorsal part of the head a bulbous projection, the tip end of which is lumi- nous. This bright light attracts other fishes, and when they approach near enough, the “ angler” makes a quick dash, closes its big jaws upon the too curious individual, and so K 130 ANIMAL BIOLOGY secures food. But whatever a fish feeds upon, and however it secures its food, it is evident that plants and other animals must furnish the food substance required to make living matter, and so provide for growth and repair of the cells, and also furnish the fuel needed to develop the energy nec- essary for the various activities of the fish. 98. Digestion and digestive organs. — We have seen in plants (P. B., 63, 70, 74) that digestion may take place in any living cell where food is stored or manufactured. Hence plants have no special part devoted to digestion. In fishes however, it is quite different, since a portion of the body, known as a digestive system, is devoted to preparing the food for absorption and use. This digestive system consists of a food tube known as the alimentary canal and certain masses of cells known as digestive glands. When the fish swallows food, this passes from the mouth cavity into a short tube, called the gullet, and thence into a €QAQS In \ ovary ducts Grom | Wriduey and Owacy \ ip - . ° ‘ ° XN wartestime Oe" OAL sac AWN Fig. 98.— Internal organs of a fish. (Carp.) comparatively long wide stomach (Fig. 98), which in the carp extends half the length of the body cavity. From the stomach extends the small intestine, which turns upon itself FISHES 131 several times, thus forming a coil, the posterior end of which finally opens to the exterior just in front of the anal fin. In the inner lining of the stomach and intestine are special cells which make up digestive glands. These have the power to manufacture digestive ferments (P. B., 53), which are forced out into the alimentary canal when food is present. As in plants, these ferments dissolve the foods and make them ready for use in the body. In addition to the digestive glands in the lining of the alimentary canal there are glands outside the digestive tube. One of these is the liver (Fig. 98), which secretes bile. This is carried to the intestines by a tube called the bile duct. In the liver is a sac (bile sac) (Fig. 98) which holds any excess of bile. When the food has been digested it is absorbed by thin-walled blood vessels found in the lining of the alimentary canal, and so passes into the blood to be distributed around the body. 99. Blood and circulation. — Instead of ducts and sieve tubes (P. B., Figs. 14, 15, 16) as in the seed plants we studied, the fish has blood vessels to distribute digested foods to various parts of the body. In addition to these the fish possesses a heart (Fig. 99), which aids in pumping or forcing the blood through blood vessels, thus keeping it in constant motion. The blood vessels are of three kinds; namely, arteries, capil- laries, and veins. The arteries have muscular and elastic walls which contract and so aid the heart in forcing the blood along its course. The arteries always carry the blood away from the heart, and they subdivide into smaller and smaller tubes. At the ends of the smallest arteries are tiny, short, thin-walled blood vessels, known as capillaries. Capillaries permit the digested food to osmose through their walls into the adjacent cells, and, in turn, absorb waste matters from the cells. 132 ANIMAL BIOLOGY \VL2 UJ SCAR MWVaTLES _ Ovn\ t Wir ANA VANS —_ /SrNamcenis : Fic. 100.— Diagram of the circulation of blood in the gill of a fish. 7. Describe the movements of the jaws and gill covers of a living goldfish when it is breathing. (If the fish has been in a jar of water without green plants for some time, these movements will be more pro- nounced.) ; 8. Watch the fish as it opens its mouth. a. Is the size of the mouth cavity now greater or less than it was when closed? b. Why does the water now enter the mouth? (The inward movement of the water may be demonstrated FISHES 135 more easily if some powdered carmine is stirred into the water.) ce What will the incoming current of water bring to the gill filaments ? 9. Watch the fish as it closes its mouth. a. Is the size of the mouth cavity now greater or less than it was before? b. Why do the gill covers now open? c. What will the current of water carry away from the gill filaments? 101. Respiration and the production of energy. — We have just seen that when the goldfish takes in a mouth- ful of water and then closes its mouth, the water is forced over the gills, thus bringing oxygen to the filaments. The capillaries in the filaments absorb the oxygen, and the blood then passes on into other arteries which carry it all over the body of the fish. In the capillaries at the ends of the small- est arteries the oxygen passes into the cells as does the food. Now what becomes of the oxygen? As in plants ( P. B., 80),.the oxygen unites with ele- ments in the foods and in the protoplasm of the cells and produces oxidation and liberation of energy, which gives the fish the power to contract its muscles and so to push against the water with its tail and tail fin, thus propelling the animal in any direction, or to open its jaws and shut them on another fish, thus securing food. In fact, all the work that the fish performs is made possible through the burning of its foods or protoplasm by the oxygen. Since the proteins, fats, carbohydrates, and protoplasm all contain carbon, when these are oxidized, carbon dioxid (CO.) is formed as one of the waste substances. All the waste substances pass out of the cells, through the walls of the capillaries, into the blood, which passes on into the veins and back to the heart. The heart contracts and drives the 136 ANIMAL BIOLOGY blood loaded with carbon dioxid out into the arteries, which carry it to the capillaries of the gills (Fig. 100). Here the waste matters pass out into the water, which is then forced out by the closing of the mouth past the gill covers. 102. Adaptations for sensation. (Optional.) 1. Study the eye of a goldfish. a. Describe its position, shape, and size relative to that of the head. b. Notice that the eye consists of a black center (the pupil) through which light enters the eye, and a colored iris. Add these features to the drawing of the goldfish (91, 5), and label each. 2. The nostrils lie in front of the eyes, and as they are small, a preserved fish head may help in locating them. (In the perch there are two on each side.) a. Show in your drawing the position, shape, and size of the nostril of one side and label. b. Gently probe the nostril of a preserved fish with a stiff bristle. P (1) Do the nostrils open into the mouth or not? (2) Could the nostrils be used in breathing? Give reason for your answer. (3) Bearing in mind the common uses of nostrils of higher animals, state which of these is the probable function of the nostrils of a fish. 103. Senses of fishes. — Fishes are said to possess keen sight. The eyes, however, except in rare cases, are only fitted for seeing while in the water. These organs have no eyelids, so the fish always seems to be wide awake. The sense of smell is located in the nos- trils, and since these do not open into the mouth cavity, this is the only function of the nostrils. The taste sense is said to be located in the outer skin. The fish has no external ears; it has, however, internal ears, but these are supposed to serve as balancing organs, FISHES 1387 rather than as organs of hearing. Fishes from which these internal ears have been removed are unable to maintain their equilibrium. Some fishes have special organs that serve as tactile organs such as are found on the under side of the head of a cod (Fig. 108) and also on the head of bullheads (Fig. 101). Along each side of the body and tail of fishes is a series of little openings or pores which form what is known as the lateral line (Fig. 108). These organs are supposed to be principally organs of touch. Fie. 101.— Bullhead. (Goode.) 104. Reproduction and life history. — The flowers of seed plants are devoted to the production of seeds which, in turn, produce new plants of the same kind (P. B., 83). Likewise in fishes there are special organs the sole function of which is the production of new individuals. The organs of fishes which may be said to correspond in function to the stamens and pistils of flowers are the ovaries (Fig. 98) and spermaries. In the ovaries are produced many egg-cells, and the mass of eggs in the ovary of a fish is often called the roe. In order that an egg may develop it must first be fer- tilized by a sperm-cell from the spermary of a male fish. This process usually occurs in the water after the ripe eggs and sperm-cells have been extruded from the ovaries and sper- maries of the parent fishes. You will recall the fact that the pollen tube containing a sperm-nucleus makes’ its way into an ovule and that the 1388 ANIMAL BIOLOGY egg- ~- nucleus egg-nucleus B, sperm-nucleus approaching the egg-nucleus ~-fertilized egg-nucleus C, sperm-nucleus and D, fertilized egg-nucleus egg-nucleus uniting Fig. 102. — Fertilization of an egg. developing embryo foe eeme A, four-celled stage of B, many-celled stage of embryo embryo ore “ yolk, food Nae Sle C, embryo more fully de- yolk sac veloped D, young, fish with yolk still attached Fie. 103. — Development of a fish egg. FISHES 139 sperm-nucleus is forced into the ovule and unites with the egg-nucleus; this is the process known as fertilization (P.B., 91). In the case of fishes the sperm-cells swim to the eggs, and then force their way into the egg (Fig. 102, A). Fic. 104. — Nest of stickleback. Above, male entering nest with eggs; below, male depositing sperm-cells. The nucleus of the sperm- and egg-cells then unite just as in plants (Fig. 102, B, C, D). The egg nucleus thus fertilized first divides, and then the cell body, and thus are formed two cells. Each of these cells in turn divides, and so four cells are produced (Fig. 103, A, B). The process of 140 ANIMAL BIOLOGY division continues until a many-celled organism is de- veloped. As the cells increase in number, they become different in character and form the various organs of the body. When the little fish first hatches, and begins to swim about, it often has attached to it some of the food substance (yolk) stored in the egg (Fig. 103, D). After this is used up, the young fish must secure its own food. Most fishes do not take any care of their eggs or young, and in some cases the parents die soon after the eggs are laid and fertilized. In the case of the stickleback, however, the male fish makes a nest (Fig. 104) in which the females deposit their eggs. The male then extrudes sperm over the eggs. The male stays about the nest and guards the eggs and also the young sticklebacks when they hatch out. 105. Artificial prop- agation of fishes. — Since, as we have said, most kinds of fishes give no attention to eggs or young, enor- mous numbers of both eggs and young are eaten by other fishes ; hence, only a small pro- Fie. 105.— Artificig] fertilization of eggs. ‘ (Coleman.) portion come to ma- turity. For example, while a codfish lays 8,000,000 eggs, only about two of these eggs on the average come to maturity. Hence, in order to increase to any considerable extent the number of fishes, the eggs are artificially hatched. That is, the fish FISHES : 141 are caught when the eggs are ripe and the eggs are gently squeezed from the ovaries into the water (Fig. 105). Then some of the sperm-cells are similarly squeezed from the male fish and mixed with the eggs. This provides for fertilizing most of the eggs, which would probably not occur in nature. Special apparatus is devised for keeping the eggs supplied with fresh water until they hatch (Fig. 106). When the Fig. 106. — Interior of fish hatchery. young are old enough they are fed for a time, then the young jry, are set free in the waters where more fish are desired. Millions of young fish are every year distributed by the government all over the United States to be placed in ponds, rivers, and lakes where the supply is deficient, or in the ocean along the shore. 106. Economic importance of fishes. — From very ancient times fishes have formed a considerable part of the food of peoples that lived near bodies of water. The importance to 142 ANIMAL BIOLOGY man of fishes as a source of food can scarcely be overesti- mated. Unlike domestic animals, the fishes grow to maturity without any care on the part of man. The fisherman has only to provide the means to gather his harvest, while the herdsman must care for his flocks and herds the year round. Thus we see why fish are cheaper than other forms of flesh food. While fish are most important to man as food, they have other uses. Thus, for instance, the menhaden are caught scarcely at all for food, but for the large quantities of oil extracted from them. ‘The remainder of their bodies is used as fertilizer. It is estimated that about 3,000,000 gallons of oil and 1,000,000 tons of scrap, with a total value of $2,500,000 is obtained annually by American fishermen from this kind of fish. The oil extracted from the livers of cod forms a valuable food preparation for invalids, since it is said to be more easily absorbed and oxidized than any other known fat. The great importance of fishes, however, is due to the fact that they furnish a cheap and wholesome food. Nearly all the parts of a fish are thus used. Not only is the flesh eaten, but also the eggs (roe). The swim bladders, too, of many fishes are made into isinglass which yields the highest grade of gelatin! Fish are eaten not only in a fresh condition, but are also prepared in various ways. Among these methods of preservation are drying, smoking, pickling, and canning. Two of the more important fisheries are those of the salmon and the cod. 107. The salmon. — The salmon (Fig. 107) is doubtless the most important food fish of the world, and the Pacific salmon completely outclasses all other forms. The Atlantic 1 See article on isinglass in Cyclopedia. FISHES 1438 salmon was once very abundant, but is gradually diminishing in numbers for reasons that will be mentioned later (110). “The salmon were made for the millions. The Siwash Indian eats them fresh in summer, dries them, or later on freezes them, for himself and his dogs in winter. The epicure pays for having the fresh fish shipped in ice to his table, wherever that table may happen to be. In mid-ocean, the great American canned salmon is often the best and only fish afloat. In the jungles of the Far East, in the frontier Fig. 107. —The Salmon. (Jordan and Evermann. Courtesy of Doubleday, Page & Co.) bazaar of the enterprising Chinese trader, it ‘bobs up serenely’ to greet and cheer the lonesome white man who is far from home and meat markets. Even in the wilds of Borneo its name is known and respected; and he who goes beyond the last empty salmon tin, truly goes beyond the pale of civilization. The diffusion of knowledge among men is not much greater than the diffusion of canned salmon; and the farther Americans travel from home, the more they re- joice that it follows the flag. : “The common salmon of Europe, and also of Labrador and New England, was accounted a wonderful fish both for sport and for the table, until the discovery of the salmon 144 ANIMAL BIOLOGY millions of the Pacific Coast cheapened:the name. To hold their place in the hearts of sportsmen, game fishes must not inhabit streams so thickly that they are crowded for room, and can be caught with pitchforks. Yet this once was true of the salmon in several streams of the Pacific Coast. The bears of Alaska grow big and fat on the salmon which they catch with the hooks that Nature gave them.” ! The Pacific salmon are caught in the rivers that empty into the Pacific Ocean, such as the Columbia, Sacramento, and Yukon. The salmon reach their maturity in the ocean. When, however, the spawning time approaches, the salmon . make their way in great numbers to the mouths of rivers like the Columbia and proceed up these streams, leaping seemingly impassable waterfalls in order to reach the head- waters. Here the sand is scooped out by the male, and the female salmon deposits her eggs and the male the fertilizing sperm-cells. The fertilized eggs are then covered with sand. The parent fish soon die; none ever reach the ocean again. After the eggs hatch, the young slowly float down the stream to the ocean to repeat the life of their parents. It is when the fish are proceeding up the rivers that they are caught. Sometimes they are so abundant that the river seems to be choked with them. Salmon are shipped fresh in ice. Enormous quantities are alsocanned andsmoked. The estimated value of the annual catch of Pacific salmon varies from $10,000,000 to $15,000,000. 108. The codfish. — Next in importance to the salmon, at least in the United States, is the cod (Fig. 108), for which the fishermen receive about $3,000,000. Other countries engaged in the cod fisheries are Newfoundland, Canada, Nor- "From Hornaday’s ‘‘ American Natural History.’” FISHES 145 way, Sweden, Great Britain, and France. The catch of cod for the world is estimated to be $20,000,000 annually. Codfish are found in the northern part of both the Atlantic and Pacific Oceans, but the Alaskan cod is not considered to be as fine a food fish as the Atlantic species.. Fic. 108.— The codfish. (Goode.) The cod is a deep water fish and is usually caught in from thirty to seventy fathoms (a fathom being six feet). Cod are caught off the coast of Newfoundland, and during the winter as far south as the Middle States. ‘‘ From the earliest settlement of America the cod has been the most valuable of our Atlantic Coast fishes. Indeed the codfish of the Banks of Newfoundland was one of the principal inducements which led England to establish colonies in America, and in the rec- ords of early voyages are many references to the abundance of codfish along our shores. . . . So important was the cod in the early history of this country that it was placed upon the colonial seal of Massachusetts, and it was also placed upon a Nova Scotian bank note, with the legend ‘ Success to the Fisheries.’ ””! The average weight of large cod is said to be from twenty 1From Jordan and Evermann’s ‘“‘American Food and Game Fishes.” Every student of this fish work should read Kipling’s “Captains Courageous’’ for description of the cod fisheries on the Grand Banks. L 146 ANIMAL BIOLOGY to thirty-five pounds, depending on the locality. The aver- age weight of small cod is twelve pounds. Jordan and Ever- mann state that cod weighing 75 pounds are not common, Fic. 109.— The shad. (Goode.) but that one was caught off the New England coast that weighed 2114 pounds. Codfish are marketed fresh, pickled, salted, and dried. Oil and isinglass are also obtained from the cod. Fig. 110.—The herring. (Jordan and Evermann. Courtesy of Doubleday, Page & Co.) 109. Library study of other fishes. — (Optional.) Consult Jordan and Evermann’s ‘‘ American Food and Game Fishes,” Hornaday’s ‘“‘ American Natural History,” and special articles in Cyclopedias or other reference books, on one or more of the following fishes: mackerel (Fig. 95), sardine, shad (Fig. 109), herring (Fig. 110), white fish, smelt, bluefish, halibut, menhaden. Write in your notebook an account of the fishes selected for study, using the following topics as a guide : — FISHES 147 S General appearance (size, color, general form). Geographical distribution (that is, in what waters the fishes * are found). Food and feeding habits. Method of capturing the fish. Amount caught annually and its value in money. . Breeding habits and other general facts of interest. If possible illustrate your composition with any drawings or pic- tures of the fish you are studying. S2 Se 08 110. Visit to a fish market. — (Optional.) In your notebook prepare an account of your visit to some fish- market, using the following topics as a guide. 1. Location of the fish market and the name of its owner. 2. Make a list of the various kinds of fish offered for sale. 3. State the kind of fish that sells at the lowest price per pound at this time of year. 4, State the kind of fish that is most expensive per pound at this season. 5. Name the kind of fish now sold in the greatest quantity. 111. Conservation of food fishes. — A story of reckless waste similar to that recorded in regard to the destruction of our forests may be duplicated here concerning the way men have exploited our abundant natural source of food, the fishes. The Atlantic salmon, which was once “the salmon,” is now of comparatively little commercial importance. “Salmon were marvelously abundant in colo- nial days. ... It is stated that the epicurean apprentices of Connecticut would eat salmon no oftener than twice a week. ... There can be no doubt that one hundred years ago salmon fishing was an important food resource in south- ern New England. ... But at the beginning of this century salmon began rapidly to diminish. Mitchill stated in 1814 that in former days the supply to the New York market 148 ANIMAL BIOLOGY usually came from the Connecticut, but of late years from the Kennebec, covered with ice. Rev. David Dudley Field, writing in 1819, states that salmon had scarcely been seen in the Connecticut for fifteen or twenty years. The cir- cumstances of their extermination in the Connecticut are well known, and the same story, with names and dates changed, serves equally well for other rivers. “Tn 1798 a corporation, known as the ‘ Upper Locks and Canal Company,’ built a dam sixteen feet high at Millers River, 100 miles from the mouth of the Connecticut. For two or three years fish were seen in great abundance below the dam, and for perhaps ten years they continued to appear, vainly striving to reach their spawning grounds; but soon the work of the extermination was complete. When, in 1872, a solitary salmon made its appearance, the Saybrook fishermen did not know what it was.” ? - The Pacific salmon is rapidly disappearing also. ‘ Natu- rally the salmon millions of the Pacific streams early attracted the attention and aroused the avarice of men who exploit the products of nature for gain. As usual, the bountiful supply begat prodigality and wastefulness. The streams nearest to San Francisco were the first to be depleted by reckless overfishing. ... Regarding the conditions that in 1901 prevailed in Alaska, the following notes . . . are of interest: ‘The salmon of Alaska, numerous as they have been and in some places still are, are being destroyed at so wholesale a rate that before long the canning industry must cease to be profitable, and the capital put into the canneries must cease to yield any return.’ “ The destruction of the salmon comes about through the competition between the various canneries. Their greed is so great that each strives to catch all the fish there are, and 1 Jordan ‘and Evermann’s ‘‘ American Food and Game Fishes.” FISHES 149 all at one time, in order that its rivals may secure as few as possible. .. . Not only are salmon taken by the steamer load, but in addition millions of other food fish are captured, killed, and thrown away. At times, also, it happens that far greater numbers of salmon are caught than can be used be- fore they spoil... . In many of the small Alaskan streams the canning companies built dams or barricades to prevent the fish from ascending to their spawning beds, and to catch all of them. In some of the small lakes, the fishermen actu- ally haul their seines on-the spawning grounds. “ The laws passed by Congress to prevent the destruction - of the Alaskan salmon fisheries are ‘ineffective, and there is scarcely a pretense of enforcing them.’ To-day the question is — will lawless Americans completely destroy an industry which if properly regulated, will yield annually $13,000,000 of good food? Will the salmon millions of the Pacific share the fate of the buffalo millions of the Great Plains? At present té seems absolutely certain to come to pass. ... The time for strong, effective, and far-reaching action for the protection of that most valuable source of cheap food for the millions is now!” ! Many of the states have passed laws for the protection and conservation of game fishes such as trout and bass. The sportsmen have seen to this; and while it is desirable that these forms of wild life should be preserved and their number increased in all our waters, it is of much greater importance that the fishes which supply food for the millions should not be left to the mercy of such utterly selfish men as those responsible for the rapid depletion of the Atlantic salmon and the rapid decrease of the Pacific salmon. It is necessary not only that the number of all fish desirable for food should be increased by means of artificial propaga- 1 Hornaday’s ‘‘The American Natural History.” 150 ANIMAL BIOLOGY tion as indicated in 105, but also that wise laws governing the catching of fish should be passed and rigidly enforced. The United States government has done and is still doing splendid work in the artificial propagation and distribution of fishes through the agency of the thirty-nine fish-hatching stations of the Bureau of Fisheries, but has done little or nothing in the regulation of the fish industry. This has been left to the initiative of the states. Following are some of the regulations that many of the states have embodied in laws: (1) There must be no obstruction in rivers that would pre- vent fish from moving freely up and down streams either to spawn or to search for food. If dams are built, runways must also be constructed permitting the free passage of fish. (2) Fish must not be caught at the spawning season, otherwise the future supply is endangered. (3) No methods of fishing should be employed in which immature fish are caught or killed. Such methods are (a) exploding dynamite in the water, thus killing all kinds and sizes of fish indis- criminately; (6) catching fishes with nets the meshes of which are so small that immature fish are caught as well as mature; (c) wholesale and mechanical devices of catching fish such as the fishing wheel, for by this device the fish have no chance for escape. (4) Fishermen must not keep fish even when caught if they are undersized. (5) It should be illegal to destroy any food fish or use it for any purpose other than food. These laws are enforced by state fish and game wardens provided there is public demand for their enforcement. The necessity for the enforcement of these. regulations will be obvious, not only in waters over which the states have jurisdiction, but also in the waters controlled by the United States government. CHAPTER V CRAYFISHES AND THEIR RELATIVES. 112. A study of the crayfish.— Laboratory study. A. Regions.— The body of the crayfish has two distinct regions. The dorsal surface and sides of the anterior region are covered by a cape, consist- ing of a single piece of shell-like material. This region is the cephalothorax (from Greek = head-thorax). The posterior! region is the abdomen. 1. Which region is composed of a number of similar segments ? 2. Which region has the legs, antenne (feelers), and eyes attached to it? B. Adaptations for walking. Place a crayfish in the center of a pan with enough water to cover the animal. If the cray- fish does not walk, touch it with the pincers. How many pairs of legs are used in walking? In what directions (forward, backward, or sideways) are you able to get the crayfish to walk? State whether or not the “ large claws ” are used in walking. Are the walking legs composed of one piece or of several movable parts? Of what advantage is this to the animal? : PO NE 5. (Optional.) Make a sketch (x2) of one of the legs to show its structure. 1 The meaning of each of these terms is explained in 6. 151 152 ANIMAL BIOLOGY C. Adaptations for swimming. Rio 10. Place an active crayfish in a pan nearly filled with water. Use the following means to get it to swim: make a sudden movement toward it with the forceps or pencil; if this does not succéed, take hold of the animal near the anterior end where you can press the large pincers against the body. Do this quickly and release the animal. This action may cause the crayfish to swim in order to escape. If you cannot get this crayfish to swim, try another. In what direction does the crayfish swim? State whether or not the legs are used in swimming. Watch the segments of the abdomen and the large appendages at the posterior end to determine their action in swimming. a. Describe the direction of the movements of these parts. b. Are these movements made slowly or quickly? In what direction will the doubling under of the ab- domen tend to send the animal? In what direction will the straightening out of the abdomen tend to send the animal? In what direction, therefore, must the crayfish strike the harder and quicker in order to swim back- wards? What difference is there in the shape of the ventral surface and the dorsal surface of the abdomen ? Which surface of the abdomen will enable the cray- fish to get the better hold upon the water? (Optional.) Straighten out and double up the segments of the abdomen, noting how the segments are con- nected. Describe now all the adaptations of the abdomen and its appendages for swimming? (Optional.) The first segment of the abdomen (next to the * cephalothorax) fits under the cape; the last is un- like the others in shape, being quite flat. Straighten CRAYFISHES AND THEIR RELATIVES 153 out and double up the parts of the abdomen; of how many segments is it composed? 11. (Optional.) The large appendages (large swimmerets) and the last segment of the abdomen taken together are called the tail fin. Make a sketch (x 2) of the abdo- men and the large swimmerets. Label: first segment, last segment, large swummerets, tail fin. D. Adaptations for breathing. To the Teacher.—Prepare some preserved cray- fishes in the following manner: Insert the point of the scissors beneath the posterior margin of the cape that covers the cephalothorax and halfway between the middle line of the dorsal surface and the lower margin of the cape; cut forward to the front end of the cape and remove the piece of shell. 1. Immerse in water a crayfish prepared as directed above. Examine and describe the structures that you find above the legs on the side where the cape has been partially removed. These struc- tures are the special breathing organs of the crayfish. They are known as gills. 2. Push the gills to one side and find the soft body wall. Higher up find the line of attachment between: the shell and the body wall. You will see that the gills are not inside the body, but in a space between the body of the animal and its shell. This space is called the gill chamber. a. In what region of the crayfish are the gill chambers found? b. ‘What forms the outer wall of each gill chamber? What forms the inner wall ? c. Lift up the cape on the opposite side of the animal ; state where it is free from the body wall. 3. Examine the gills on a leg that has been removed from the thorax and floated on water and note 154 ANIMAL BIOLOGY that it is largely composed of numerous slender divisions, called the gill filaments. Make asketch of the leg (X 2) with the gills at- tached and label gill filaments. 4, The gills are furnished with numerous minute thin- walled blood vessels and the blood in them is separated from the water only by a thin mem- brane. The blood flows into the gills from all parts of the body by one set of blood vessels and leaves the gills by another. Bearing in mind that breathing is essentially the same in animals as in plants (P. B., 82), — a. What gas will the blood bring from the body to be given off in the gills in the process of breath- ing? b. What gas is taken up by the blood in the gills to be carried around the body? c. How are the gill filaments (as stated above) fitted by structure to permit this interchange of gases? d. How are the delicate gill filaments protected from injury? 5. If the same water remained on the gills for some time, what changes in the relative amounts of oxygen and carbon dioxid in the water would occur? Why, then, is it necessary that a current of water should pass over the gills? 6. Do currents of water pass through the gill chamber ? — Demonstration. Inject some harmless coloring matter, such as powdered carmine in water, into the posterior end of the gill chamber. Place the crayfish again in water. State what was done in this experiment. Give your observations and conclusion. c. What will the incoming current of water bring to the gill filaments? d. What will the current of water carry away from the gill filaments? Saas CRAYFISHES AND THEIR RELATIVES 155 7. How the crayfish causes a current of water to pass through the gill chambers. To the Teacher. — Prepare several living crayfish so that the action of the gill bailer may be seen. Todo this carefully cut off a small part of the anterior por- tion of the shell just over the gill scoop. Watch the movements of the small blade-like body in the front of the gill chamber. This body is the gill batler, or gill scoop. a. Describe the movements of the gill scoop, or gill bailer. b. When it moves upward and forward, what effect will the gill bailer have on the water in front of it and in the gill chamber? c. Where can water enter the gill chamber? (See D, 2, ¢.) 8. (Optional.) The gill bailer is a part of one of the crayfish’s mouth parts, known as the second maxilla. Exam- ine a second maxilla that has been removed from the head thorax of a preserved crayfish. Place it in a watch glass half filled with water and make out the following parts : — a. A part shaped something like a bird’s wing, composed of several pieces. b. The gill bailer that you have already seen. c. The part where the second maxilla was torn from the body, clearly shown by the shreds of muscle. When you have made out these parts, make a sketch of the second maxilla (X 4), and label: winglike part, gill bailer, shreds of muscle. 9. How does the shape of the gill bailer fit it for the work it does? E. (Optional.) Adaptations for food getting. 1. Place an earthworm, a piece of beef, or a piece of clam near a crayfish, and describe the way in which he gets the, food to his mouth. 156 ANIMAL BIOLOGY 2. Of what use may the mouth parts (easily seen in a living crayfish) be in getting food into the mouth? 3. Push the outer mouth parts of a living crayfish to one side ‘ with the forceps and find a pair of hard jaws, mandibles. Pry them open a little. a. Do they work from side to side or up and down? b. Describe the cutting edges of the mandibles. c. Of what use would these jaws be in preparing food for swallowing? F. (Optional.) Adaptations for protection. 1. Describe the outer covering of the animal? Of what use is this to the animal? 2. Locate the softer parts -of the crayfish’s armor? How are these protected by their position? 3. Gently touch the eye of a living crayfish. a. Describe the movements of the eye. How might these movements be advantageous to the animal? b. Of what advantage may it be to the crayfish to have its eyes on stalks instead of on the surface of the head? c. Make a sketch (X 4) of one of the eyes on its stalk. Label: fleshy stalk, eye. 4. Of what use may the large pineers be in addition to helping in securing food? Sketch (x1) one of the large pincers complete. G. (Optional.) Additional drawings. 1. Make out the parts of one of the large antenne. Notice the broad finlike part at the base of the antenna, then two segments, and a long lash that arises from the second segment. Sketch (<2) a large antenna. Label. 2. Make a sketch (x 1) of dorsal view of the crayfish. Label the regions, and all the appendages. 113. Habits of crayfishes. — Crayfish are found commonly throughout the United States in rivers and their tributaries CRAYFISHES AND THEIR RELATIVES 157 where limestone is found, since lime is needed in making their hard outer covering. During the day they hide under stones, in the crevices of rocks, in the mud, and sometimes in specially constructed burrows along the banks. Since the animal backs into these hiding places, its big claws are ready for business if an enemy attacks it. Then, too, the colors of crayfishes aid somewhat in pro- tecting them since these colors are usually similar to the color of the bottoms of the streams in which they live. Lastly, the wide range of vision, which the stalked eyes afford must serve to warn the animal of the approach of danger. Never- theless they do not always escape since crayfish are often captured by certain birds and fishes. In fact, crayfishes are often used by man as a bait for catching fishes. 114. Food, food getting, and digestion. — At night cray- fishes crawl about in search of food, concerning which they are not at all fastidious, since dead fish and other dead animals seem to be fully as acceptable as when alive. In fact, they are natural scavengers. Crayfish seize their food with their large claws and with the aid of the small pincers on the front walking legs and with the mouth parts, especially the mandibles, reduce the food to pieces small enough to be eaten. We have seen in plants (P. B., 68, 70, 71) that digestion many take place in any living cell where food is stored or manufactured. Hence, plants have no special part devoted to digestion. In cray- fishes, however, it is quite different, since a part of the body, known as a digestive system, is devoted to preparing the food for absorption and use. This digestive system consists of a food tube known as the alimentary canal and certain masses of cells known as digestive glands. After the food is digested, it can pass into the blood by 158 ANIMAL BIOLOGY osmosis and be carried to the cells 1 of the body. When the digested food reaches the cells, it may be used by the proto- plasm either in making more living matter or, as we shall now see, for the release of energy. 115. Respiration and the production of energy. — In our laboratory study we watched the movements of the gill bailer and saw that it caused a current of water to enter the posterior end of the gill chamber and flow over the gills, . thus bringing oxy- gen to the filaments (Fig. 111). The thin-walled blood vessels in the fila- ments absorb the oxygen, and the blood then passes on into other blood vessels, which carry it back to the heart, whence it is forced all over the body of the crayfish, and so the oxygen in the ‘blood passes into the cells as does the food. Now what becomes of the oxygen? As in plants (P. B.,, 80), the oxygen unites with ele- ments in the foods and protoplasm of the cells and produces oxidation and liberation of energy, which gives the crayfish the power to contract its muscles and so push against the water with its abdomen and tail fin, thus propelling the animal backward, or to open its nippers and shut them and so se- cure food. In fact, all the work that the crayfish performs is made possible through the burning of its foods or proto- plasm by the oxygen: Fie. 111.— Gills of a crayfish. 1 We have shown in plant biology (41) that plants consist of cells which are largely composed of living matter known as protoplasm. This is also true of animals (126). : : CRAYFISHES AND THEIR RELATIVES 159 Since the proteins, fats, carbohydrates, and protoplasm all contain carbon, when these are oxidized, carbon dioxid (COs) will be formed as one of the waste substances. All these waste substances will pass out of the cells into the blood, which finally conveys them to the filaments of the gills. Here the waste matters pass out into the water, which, as we have seen, is then forced out of the front end of the gill chamber. 116. Life history. — As in the seed-producing plants, crayfishes are reproduced by means of special cells known as egg-cells which in crayfishes are formed in the body of the fe- male in organs known as ovaries. Before they can develop, however, these egg-cells, as in the seed plants, must be ferti- lized by sperm-cells, produced in spermaries of the male cray- fish. After extrusion the fertilized eggs are attached by a sticky substance to small appendages, known as swimmerets, on the ventral surface of the abdomen of the female (Fig. 112). Here the fertilized egg-cell develops into a many-celled em- bryo, and finally a tiny crayfish is hatched. At first the young crayfishes are held to the swimmerets by threads; later they cling by means of their pincers, and after some days become independent. At intervals in both young and old crayfishes, the hard outer covering of the body is shed. This shedding of the skin is called molting. But for this process it would be impossible for the young to grow. While the young crayfishes are attached to the parent they are of course protected by their position, and the female looks after them by looking out for herself. The food for the developing embryo is stored in the egg. After hatching, the young must care for themselves, and after they become in- dependent they receive no protection at all. There is, there- 160 ANIMAL BIOLOGY fore, in the case of crayfishes nothing like the parental care of higher animals. Fic. 112. — Female lobster with eggs beneath abdomen. (Herrick’s ‘‘ Amer- ican Lobster ’’ — United States Fish Commission.) 117. Relatives of the crayfish. — One of the relatives of the cray- fish is the lobster (Fig. 112), which is a salt water animal found along the north Atlantic coast. Like the crayfish, its body consists of CRAYFISHES AND THEIR RELATIVES 161 a cephalothorax and a clearly segmented abdomen. The lobster also has two pairs of antennz, a pair of stalked eyes, a number of pairs of mouth parts, a pair of big claws, four pairs of walking legs, to the bases of which gills are attached, and a pair of swimmerets abdomen Fic. 113. —The.crab. on each of the segments of the abdomen except the last. In general, lobsters are very much larger than crayfishes, one of the largest known specimens weighing over twenty-three pounds. Less like the crayfish in appearance are the crabs, yet a care- ful examination shows that these animals have practically all of the characteristics mentioned in the preceding paragraph. The cephalothorax of crabs, however, is usually wider than it is long (Fig. 113), and the abdomen is much reduced and is commonly folded in a groove be- neath the cephalothorax. Few of the crabs are able to swim; usually they crawl sideways by the help of their Fic. 114.—The hermit crab four pairs of walking legs. me one he ape euel “A curious modification of habit is shown in the hermit crab (Fig. 114), which in early life backs into an empty snail shell which aids in protecting it from its enemies. The abdomen, thus covered, becomes soft and flabby. As growth proceeds the necessity arises for-a larger shell, and the ¢rab goes ‘ house-hunting’ among the empty shells along the'shore, or it may forcibly extract the snail or other hermit from the home which strikes its fancy.” — Jorpan and Heats, “ Animal Forms.” M 162 ANIMAL BIOLOGY Among the relatives of the crayfish that live in damp places on land are the pill bug and the sow bug (Fig. 115) which are often found beneath water-soaked wood. All the animals we have described in this chapter belong to the class Crustacea, so-called from the hard outer shell which invests them. 118. Economic importance of the Crus- tacea.— Crayfishes in Europe, particularly in France, are highly esteemed as food, and special efforts are made to increase their number. In this country, however, they have, as yet, been used but little as food. Their principal use is for bait in catching certain kinds of fish. The lobster is to us what the crayfish is to Europeans. While they are not abundant enough to be considered a very important source of food, still the fishermen in 1901 received $1,400,000 for the lobsters bug. Fig. 116. — The shrimp. caught. They are considered rather as a delicacy, since they are too expensive for general use, principally on account of their scarcity. For a number of years the United States government has been making efforts to increase the number of lobsters by artificial propagation. Some states have passed laws forbidding the catching of immature lobsters and lobsters with eggs attached. CRAYFISHES AND THEIR RELATIVES 163 Other crustacea that are used for food are prawns, shrimps (Fig. 116), and certain kinds of crabs. Nearly all the crustacea eat dead animal food; consequently they are useful in keeping the water free from dead material. CHAPTER VI PARAMECIUM AND ITS RELATIVES 119. Study of the paramecium. — Laboratory study. Note to Teacher.— To secure paramecium material, add some chopped hay to a’large jar of water several weeks before the animals are needed. The paramecia develop more rapidly and are of larger size if the water is secured from a stagnant pool. The hay infusion furnishes food for bacteria upon which the single-celled animals feed. To obtain the paramecia, transfer to a glass slide with a pipette a drop from near the surface of the water. A. General appearance of paramecium. 1. Place a drop of water containing many paramecia or other similar forms on a glass slide (with concave depression if possible). Examine with a magni- fier. Describe the appearance of the tiny bodies that you see moving about. 2. Now examine the drop of water with the low power of the compound microscope. Do not allow the water to evaporate entirely, but keep adding a little from time to time. a. Do the paramecia swim slowly or rapidly? b. Is the more pointed end of the animal usually foremost in swimming or the rounded end? B. Structure of paramecium. Secure a stained and mounted specimen of a paramecium, or add a drop of iodine solution to the water containing the living animals, and 164 C. PARAMECIUM AND ITS RELATIVES 165 place a cover glass on top. Examine first with the low power of the microscope and then with the high power. Make a sketch two or three inches long to show the following : — 1. The general shape of one of the paramecia. 2. A fringe of slender hairlike projections around the outer surface. They are called cilia (singular cilium, from Latin, meaning a hair). The cilia are projections of the protoplasm of the cell. They project from the upper and lower surface also, but they cannot be seen readily. 3. A more deeply stained portion of the protoplasm near the center, the nucleus (Fig. 118). The rest of the cell is the cell body. 4. Particles of matter, food particles scattered through the body of the cell. 5. Label: cilia, nucleus, food particles, cell body. Food getting. To the drop of water containing the living paramecia add a little finely powdered carmine, and on the drop place a cover glass. 1. Tell what was done. 2. Throw all the light you can on the paramecia by means of the mirror and use the larger openings in the diaphragm. What evidence have you that the paramecia are feeding on the carmine? Sometimes it is necessary to leave the paramecia for twenty-four hours before they feed. 3. Watch the paramecia swimming through the particles of carmine. What evidence have you that the cilia are in motion? 4. The paramecium has a furrow on one side of its body, and from the furrow a tubular passage or gullet leads into the protoplasm. Both the furrow and the gullet are lined with cilia. a. If you are able to see either the furrow or the gullet, describe them. b. In what direction must the cilia in the furrow and 166 ANIMAL BIOLOGY the gullet strike the swifter and with the more force to bring food particles into the gullet? D. Locomotion. (Optional demonstration.) Examine with a high power a paramecium that is comparatively quiet. the cilia. Focus carefully and look for 1. Describe the cilia and their movements. 2. When the paramecium strikes against the water in one direc- tion, in what direction would its body tend to move? 3. Must the paramecium strike harder toward the blunt end or toward the pointed end when it swims with the blunt end foremost? E. Excretion of liquid waste. (Optional demonstration.) Look at a paramecium . or vorticella with both the low and high power and search for clear circular spots. Watch to see if any of these contract. vacuoles. cilia cilia contractile vacuole ~~~ gullet with ~ food ball food balls B, vorticella Fig. 117. — Protozoa with cilia. If they do, they are contractile There are two in paramecium and one PARAMECIUM AND ITS RELATIVES 167 in vorticella (Fig. 117). The liquid waste flows from the protoplasm into these spaces, the pro- toplasm then pushes together and forces the waste out of the body. 1. Describe the position, appearance, and action of the con- tractile vacuoles. 2. State in your own words the use of the contractile vacuoles. 3. Sketch the contractile vacuoles in your drawing of the para- mecium and label. PF. Reproduction of paramecium. (Optional demonstration.) All the time while you are studying the parame- cium be on the lookout for forms that are dividing. If you do not see any, examine mounted slides that show the paramecium dividing. Make a sketch three inches long of a paramecium dividing, to show how it reproduces. 120. External structure and locomotion.—In form a paramecium resembles somewhat the shape of a slipper, hence it is sometimes called.the “‘slipper-animal” (Fig. 118). : Sood vacuoles contractile yacoole . Re contractile vacuole ™ 2 . ‘: feaftlll nucleus gullet Fig. 118.—The paramecium. (Dahlgren.) Extending from all parts of its outer surface are many tiny projections of protoplasm that look like colorless hairs; these are known as cilia (singular cilium). In locomotion , 168 ANIMAL BIOLOGY the animal usually moves with the blunt end (1.e. heel of the slipper) in front, the paramecium being propelled by the strong backward strokes of the cilia and a slower recovery. When it runs into an obstacle, the cilia are reversed in action and thus the animal is enabled to move with the opposite end (toe of slipper) in front. Most animals that swim (e.g. fishes and frogs) have broad and flat appendages which are com- paratively large. In paramecium, on the other hand, the organs of locomotion (cilia), while slender, are so numerous that they perhaps accomplish the same results as the broad swimming appendages of the frogs and fishes. 121. Food, food getting, and digestion. — Paramecia feed upon one-celled plants and animals. On one side of a para- mecium is a furrow or groove, which is lined with cilia. At the lower end of the groove is an opening, the mouth, which leads into a short, tubular gullet. The rapid motion of the cilia in the groove draws the food toward the mouth opening and other cilia lining the gullet push down the food particles. Small collections of these food particles are made at the lower end of the gullet, and these masses, food balls, are circulated within the cell by the streaming movement of the proto- plasm. Although the paramecium is a single cell, it has cer- tain parts specially developed for securing food, just as the higher animals have special organs for this function. As the food balls circulate through the protoplasm, they are gradually digested, and the food materials thus liquefied are used as in plants and other animals for the production of more protoplasm or for the release of the energy needed for locomotion and for food getting. The indigestible parts of food are forced out through the side of the body. 122. Respiration and the liberation of energy. — The paramecium is surrounded by water that contains oxygen PARAMECIUM AND ITS RELATIVES 169 and this passes into the protoplasm through the thin mem- brane surrounding the animal. When the oxygen combines with the chemical elements found in foods and protoplasm, oxidation is carried on, energy is released, and waste sub- stances are formed which are given off in the process of excretion. 123. Excretion of wastes. — At either end of the animal is a clear space which is sometimes circular and at other times star-shaped. These are the contractile vacuoles. The wastes formed by oxidation (e.g. carbon dioxid and water) collect to form the vacuoles. The protoplasm presses upon the waste materials and periodically squeezes them out of the animal. When this occurs, the contractile vacuole disappears. 124. Reproduction and life history. — In the interior of a paramecium are two nuclei known as the large nucleus and the small nucleus, both of which show readily when the animal is ee stained with iodine or with other chemicals. When the animal re- produces, both the large and small oui, ---¥ nuclei divide in halves (Fig. 119), : a new mouth and gullet areformed, ,,41 and two new contractile vacuoles nucleus appear. The cell body then di- ™™™ ~ vides transversely, the cells sepa- rate fromi each other, and thus from a single individual, two new : : : : Fie. 119.—A paramecium di- paramecia are formed. If condi- ceili, tions are favorable, both animals grow and may in turn reproduce at the end of twenty- four hours. “It has been estimated that one paramecium “large nucleus large nucleus 170 ANIMAL BIOLOGY may be responsible for the production of 268,000,000 offspring in one month.” 125. Study of ameba (plural, amcebe or ameebas). — (Optional laboratory study.) A. Structure of ameba. Examine a living amoeba or a stained specimen on a pre- pared slide. Use a low power of the compound microscope at first, and then as high a power as may be neces- sary. Make a sketch about three inches long to show the following : — 1. An outline to show the shape of the animal, including any projections of the protoplasm, which are called pseudopods (Greek pseudo = false + pod = foot; hence, the name false foot). 2. The main mass of the amceba, clear and jellylike in a living ameeba, slightly stained in a mounted specimen, which is called the cell body. 3. A slightly denser part of the protoplasm in the living form or stained much darker in the preserved animal, the nucleus. 4. Particles of food or one-celled plants scattered through the cell body. 5. Label: false feet or pseudopods, nucleus, cell body, food particles. 6. If time allows, draw several different forms assumed by the specimen. B. Locomotion. In a living amoeba watch with the high power of the microscope the creeping movements, and the projections of the pseudopods. 1. Are the movements slow or rapid ? 2. In your own words give a description of the locomotion of the amceba. PARAMECIUM AND ITS RELATIVES 171 C. Excretion of liquid waste. Look for a clear, roundish spot in the amceba which at intervals disappears. This is the contractile vacuole. The liquid waste flows into this space and then the protoplasm pushes together and forces the waste out of the body. 1. Describe in your own words the appearance and action of the contractile vacuole. 2. Sketch the contractile vacuole in your drawing of the amceba t and label. 126. A comparison of paramecium and amoeba. — Both ameba and paramecium are animals so small that they can barely be seen with the naked eye. Both live in water, both are one-celled animals, and both carry on the same functions, but in a somewhat different manner. While the paramecium main- tains a more or less Pence: fixed form, the vacuole amoeba is capable of assuming almost any shape (Fig. 120). This it does by caus- ing portions of its substance to flow out in many directions. These projections are known as pseudopods which mean false feet. By pushing out these pseudopods in front and pulling up its protoplasm from behind, the amceba slowly flows from one part of the slide to another. Unlike the paramecium an ameceba has no definite part of the body through which it takes in food. When the animal is feeding, jnucleus food vacuoles pseudopod Fig. 120.— The ameeba. 172 ANIMAL BIOLOGY it slowly flows about the one-celled plant or animal and finally ingulfs it. The processes of digestion, assimilation, respiration, excretion, and reproduction (Fig. 121) are much the same in amceba’ asin paramecium. Both these animals belong to a group of animals known as the Protozoa (Greek protos = first or simplest + zoén = animal). Fig. 121.— An ameeba dividing. 127. To show that the higher animals are composed of many cells. — Laboratory study. Frogs are continually shedding parts of their epidermis, and pieces of this thin membrane are likely to be seen cling- ing to a frog in an aquarium or floating in the water. Secure a piece of this membrane, spread it on a slide, add a drop of water and.a cover glass, and examine with the low power of the microscope. 1. Describe the form and color of each cell. 2. In each cell notice a body, usually near the center and slightly more dense than the rest of the cell. This is the cell nucleus. (If the nucleus does not show clearly, add a drop of iodine to the membrane.) The rest of the cell is the cell body. a. Name, now, two parts of a cell of the frog’s epidermis. PARAMECIUM AND ITS RELATIVES 173 b. State the form and position of the cell nucleus. 3. Make a drawing of three of the cells described above, each cell to be represented about an inch in diameter. Label cell body and cell nucleus. 4. (Optional.) Demonstrate by the use of prepared slides, pictures, or charts that the blood, intestine, and other organs of the body of a frog or other higher animal are eomposed of cells. Make a drawing of a single cell in each case. 128. A comparison of Protozoa and the higher animals. — Our study thus far has shown that all animals, including the Protozoa, perform the necessary functions of locomotion, food getting, assimilation, respiration, and reproduction. The adaptations for performing these functions, however, are very diverse. All animals except the Protozoa consist of many cells and the various functions of the higher animals are performed by groups of cells known as organs. For example, certain com- binations of cells carry on locomotion, others digestion, while still others are set apart for breathing. All these functions are performed in a Protozoan by a single cell. 129. Economic importance of Protozoa. — Most of the Protozoa serve as food for other animals that live in the water and these in turn are fed upon by fish, which are eaten by man. Thus the one-celled plants and animals are found to be an important food-basis for human beings. Some of the Protozoa that live in the sea secrete tiny shells (Fig. 122), and when the animals die the shells drop to the bottom. As a result of heat, pressure, and other causes, this bottom ooze is gradually solidified to form chalky rocks, and in the upheavals that have taken place in ages past these rocks have been forced above sea level. The 174 ANIMAL BIOLOGY chalk cliffs of Dover, England, were doubtless formed in this way. While most of the Protozoa are harmless, there are a few forms that have become para- sitic in human beings. We have already discussed the single-celled animal that causes malaria and that is carried from one individual to another by the Anopheles mosquito (39). This parasite resembles an amceba in form. BD SUE Another form of Protozoan Fic. 122.—The shells of one-celled causes the terrible disease azimaly tiny found chalky known as the.sleeping sick- ness of tropical Africa. Many biologists believe that yellow fever (41) is caused by a protozoan that is transmitted by the Stegomyia mosquito. CHAPTER VII ADDITIONAL ANIMAL STUDIES A. Porifera (sponges) 130. Sponges.— The sponges are animals more complex in structure than the Protozoa, for they are composed of many cells; nevertheless, they are comparatively simple in structure since they have no digestive, circulatory, respiratory, or nervous system, and therefore each cell has to carry on practically all the necessary nutritive functions. Sponges differ largely in the kind of skeletons that they possess. In the common bath sponge (Fig. 123) this is composed of a tough, horny material. When sponges are ready for market, only the horny skeleton re- mains, the living cells hav- ing been killed and removed. The sponge skeleton shows a large number of pores in the outer surface, and for this reason the name Porifera (Latin = pore-bearing) is ; B given to this group of ani- Fic. 123.— Bath sponge. mals. The pores lead into canals that run through the body, finally connecting with one or more larger central cavities that lead outward, usually at the top. In certain parts of these canals there are cells with cilia; -their action causes water to rush into the canals through the pores, bringing food and oxygen to all the cells of which the sponge is 175 176 “ANIMAL BIOLOGY composed. The wastes are forced out through the larger canals referred to above. Like the bath sponge, all other Porifera are stationary in their mature form. B. Celenterata 131. Hydra. — A study of a fresh water coelenterate known as hydra will give one a fair idea of the structure and adaptations of this group of animals. Hydra is a small animal found in fresh water attached to water plants, and sometimes to surfaces of stones or tentacle ~~ nettling cells ~ __ Mature sperm-cells young tentacle base of hydra Fie. 124.— Longitudinal section of a hydra. (Hegner.) other objects on the bottom. At the upper end of the tiny cylin- drical column are threadlike bodies known as tentacles (Fig. 125, 1). If the animal is touched with a needle or pencil, it contracts its body and tentacles so much that it can scarcely be seen. But in a short time it expands again. If the hydra happens to be hungry and some small form of animal ADDITIONAL ANIMAL STUDIES 177 comes in contact with the waving tentacles, the hydra ejects micro- scopic threads from certain cells (nettling cells) in the tentacles. The animal thus attacked is benumbed, and the hydra then uses the tentacles to push its prey into a mouth opening in the center of the circular row of tentacles. The food is drawn into the inside of the column, which is simply a hollow tube (Fig. 124). Here certain cells secrete digestive fer-. ments which dissolve the foods that the animal has eaten, and the indi- gestible matter is ejected from the mouth. The digested food is then absorbed by the cells lining the cavity. Since the animal is bathed outside and inside by water contain- ing oxygen, the cells are able to absorb oxygen from the water and to give off carbon dioxid to the water. Hence no breathing organs are needed. It is evident that the tentacles with the nettling cells also serve to protect the hydra from too great familiarity on the part of visitors = that might otherwise use it for food. Frc. 125.—The movements made When the hydra moves from one y hydra in locomotion. (Jen- place to another, it bends over ae until the ends of the tentacles touch the surface on which it rests. The tentacles then adhere to this surface, the bottom of the column lets go, and the animal turns a somersault (Fig. 125) and lands on the lower part of the column; the process may then be again repeated. Like the higher animals the hydra reproduces by means of eggs and sperms. But it also has another interesting way of producing new individuals. On the surface of the column one frequently sees little bunches. These are called buds (Fig. 124). They keep on growing outward till at last little tentacles and a mouth opening are N 178 ANIMAL BIOLOGY formied at the tip of each. It is now evident that we are looking at a very tiny hydra. Finally the new individuals separate from the column and begin an independent life. This method of reproduc- tion is known as budding. y a M4.) v7 NS A, organ-pipe coral B, precious coral C, sea-feather Fig. 126.— Different forms of coral. 132. Suggestions for the study of hydra. —- Laboratory study. Pupils should be supplied with living hydra if possible. The column and tentacles should be observed by the aid of a magnifier, described and drawn. The animal should be touched and the action of the column and tentacles noted and de- scribed. If the hydra moves from place to place, the method of locomotion should also be described. 133. Relatives of hydra. — Among the relatives of hydra are the corals (Fig. 126), sea-anemones, and jellyfish (Fig. 127). One form of coral, the red coral, is of considerable economic importance. In all the corals the column secretes a mineral sub- Fig. 127.— Jellyfish. (Hargitt.) ADDITIONAL ANIMAL STUDIES 179 stance within which the animal can withdraw when danger threatens. In the case of the red coral this material is horny. It is used for decoration, and some communities on the Mediterranean are devoted largely to the gathering of this coral, and to making it into various forms of jewelry. C. Annelida 134. Earthworm.— The most common representative of the annelida is the earthworm (Fig. 128). The general form of this ani- mal is long and cylindrical. If one places an earthworm on the Matyi "rent Girdle 2. Mouth ge ' Qnerng AON. Fie. 128.— The earthworm. (Sedgwick and Wilson.) ground, it will start to crawl away or bore into the soil. Observe that the end that is foremost is tapering. This is the anterior end. The opposite or posterior end is broader and considerably flattened. The part of the body on which the worm crawls is the ventral sur- face, which is somewhat flattened, while the dorsal surface is rounded. The whole body is composed of rings or segments. About one third of the distance from the anterior end of the worm several of the seg- ments are usually somewhat enlarged and form the girdle. At the anterior end toward the ventral surface, there is a small opening. This is the mouth, and through it the earthworm sucks in its food which consists not only of dirt, but of leaves of various kinds. Overhanging the mouth is a tiny projection, the lip. The animal has no special breathing organs. The skin, however, is permeated with capillaries, and thus serves as a breathing organ. Locomotion is brought about by alternately lengthening and then 180 ANIMAL BIOLOGY shortening one portion of the body after another. On the ventral region of the body are rows of bristles which aid in locomotion. The bristles project backward when the worm is moving forward, and so keep the animal from slipping backward when it lengthens itself. The bristles also serve to hold the’animal in its burrow. Earthworms are of considerable value in the soil. They burrow through the earth by swallowing the dirt which is mixed with vege- table matter; both are then acted upon by digestive juices in the alimentary canal. The refuse of the food, which is not available for use in the body, is ejected from the posterior end of the intestine. The little piles of dirt that are sometimes so common on a, lawn are the “ castings ” of earthworms. It has been found that soil worked over by these animals is in better condition for the growth of plants. Then, too, the deeper soil that has not been used by plants is brought to the surface and mingled with the dirt recently used. Darwin 4 estimated that in England earthworms annually bring to the top of the ground eighteen tons of soil per acre. 135. Suggestions for the study of the earthworm. — Laboratory study. This study should be made upon living worms. The pupil should first note and describe the general shape and segmentation of the animal, the differences between the anterior and posterior ends, the dorsal and ventral surfaces, and the characteristic appear- ance of the girdle. An earthworm should be placed on a moist surface such as soil or wet paper, and the locomotion of the animal observed and described. A large specimen should be pulled, an- terior end first, between the fingers, and the action of the bristles noted and their situation and appearance studied with the help of a magnifier. Touch the earthworm on various parts of the body, and determine, if possible, which portions are the most sensitive. Look on the dorsal and ventral surfaces for blood vessels, and watch the pulsations of the blood in these vessels; describe the location of these blood vessels and state the direction in which blood flows in each of them. , 1Darwin’s ‘‘ Vegetable Mold and Earthworms.” ADDITIONAL ANIMAL STUDIES 181 136. Relatives of the earthworm. — Two forms of animals that formerly were classed with the earthworm under the head of ‘‘ worms” are the tapeworm (Fig. 129) and trichina. The tape worm is some- times present in beef and trichina (Fig. 130) in pork. . Meats, there- fore, should be well cooked to kill all such parasites. The trichina, if it gets into the. human system, causes great suffering. When a tapeworm becomes attached to the human intestine by the suckers and hooks on its anterior end, it is diffi- cult to dislodge. D. Mollusca 137. Fresh water mussel. — The fresh water mussels are mollusks that are sometimes called clams. They are often quite abundant on the bottom of creeks, rivers, ponds, or lakes. Usually they are partly covered with sand or mud, sometimes even more than is shown in Figure 131. It will be seen at once that the B, tapeworm, about 15 feet long, omitted portions being indicated acry gained Fic. ea ae ey (Shipley and two parts called valves ; hence these animals, as well as salt water niussels, clams, and oysters are called bivalves (Latin bis = two + valve). The two valves are held together along one margin by a tough material that serves as a hinge. On each valve near the hinge, a promi- nence, known as the beak or uwmbo, may be readily seen. Around 182 ANIMAL BIOLOGY the umbo, in ever widening concentric rings, are the lines of growth of the animal, which indicate younger stages in its development. Let us now pu!l up a mussel and lay it on a sandy bottom. Ina few moments the shell will open somewhat and from one end will project a pinkish body, which may finally extend some distance. This organ is the foot. If mo ) Ma we watch long enough, we Ba) yes a mma 7 pM ) may see the mussel use the ony MMB EG ah mn PD ar? tm foot to push itself over the “2 surface of the sand or it yas Sein may burrow into the sand, nnn ae ut niin and fin: ally come to occupy Fig. 130.— Trichina in Muscle. (Leuckart.) a position like that in which we found it. Now if one is patient, and the animal feels at home, it will be pos- sible to see the method of eating and breathing. At the end oppo- site the foot there may slightly project from the shell a fringed and somewhat tubular-shaped structure. Let us place a little finely powdered carmine in the water above the opening. As the carmine slowly sinks and comes opposite the tube, the particles will suddenly be drawn into the tube. This shows that water is being sucked into the tube, and it brings with it oxygen and any food that may be near, such as mi- . eroscopic plants and animals. To learn any more about the feeding and breathing of the mussel it will be neces- sary to open the shell. Let us take an- other mollusk and pry open the valves. We shall soon find that this is not easy todo. The reason will be evident after studying Figure 132. The valves are held together by strong muscles. So we pry the valves open a little with a heavy knife and then slip another sharp knife in close to the valve, where we meet an obstruction toward one end. When we have cut this, the valve opens at that N) Ny DD Ri; ny DE foot Fic. 131.— Mussel bur- rowing in sand. ADDITIONAL ANIMAL STUDIES 183 end. After cutting the muscle at the other end, we can readily separate the valves. All over the surface of the animal, except where the two muscles were attached to the shell, is a thin cover- ing called the mantle. By raising the body of the mussel from the valve it will be evident that there is a similar structure on the other side. Now, if we fold back the mantle, it will be possible to follow the course of the food and water. The first thing that strikes our at- muscles that hold 1 the valves to- / gether + muscles that . hold thevalves \ together Z incurrent f siphon _— lines of growth foot Fic. 132. — Fresh water mussel with foot extended. tention is the contracted foot, and above this is a soft mass called the abdomen. In the abdomen are found the digestive organs. On each side of the abdomen are two broad, thin flaps, the gills, by which the animal breathes. Between the foot and the end that was bur- ied in the sand are found, on either side of the body, two small flaps or palps, and between them lies the mouth opening. To this mouth the food that has been swept into the tube is brought by the wav- ing of thousands of cilia that are found on the surface cells of the gills and palps. Let us now return to the study of the mussel partly covered by the sand. The hinge is on the dorsal region of the body, the free edges of the valves on the ventral, while the mouth and foot are at 184 ANIMAL BIOLOGY the anterior end. Hence, the animal in its natural position “stands on its head,” or at least where its head ought to be. From the pos- terior end projects the tubular structure to which reference has been made. Let us again drop some powdered carmine closer to the animal, and watch the particles when they reach a point just above the tube where we saw the particles enter. We shall now see the carmine carried away from the animal instead of into it. A closer examina- tion reveals the fact that the tubular structure has’a second opening above the first. Both of these tubes are called siphons, the lower being the incurrent siphon, and the upper the excurrent siphon. The stream of water forced out of the excurrent siphon carries with it the carbon dioxid and other wastes of the body. 138. Suggestions for study of the mussel. — It is desirable to have students see the mussel in its natural home. They should tell where they found the animals and the positions in which they were seen. It would then be well for the pupil to study in the laboratory the shell, making out the points of structure described above. A drawing of a side view of the mussel should be made and labeled as follows: valve, umbo, hinge, lines of growth, anterior region, posterior region, dorsal edge, ventral edge. It is also desirable that a drawing of the animal in the sand or mud be made and the incurrent and excurrent siphon openings be labeled. The pupil might well follow the account as given above, verifying the statements and experiments, and making drawings of the mussel with the shell open and all the animal lying in one valve. Label: mantle, muscles that close shell, incurrent siphon, excurrent siphon. Also a drawing should be made of the mussel with the mantle re- moved. Label: foot, abdomen, palps, mouth, gills. Write an account of how the mussel moves or burrows, how it feeds and breathes. 139. Relatives of the mussel.— Some of the relatives of the mussel are the clams, oysters, salt water mussels, snails (Fig. 133), and slugs. While the fresh water mussels are not much used for ADDITIONAL ANIMAL STUDIES 185 food, they are important economically on account of the pearly matter that is found on the inside of their shells. This-is used in making buttons and other articles. In fact, there is a considerable industry in this line along the Missis- sippi River. Oysters are im- portant as an arti- cle of food. The oyster fishermen re- ceive annually from twenty to thirty mil- lions of dollars from these mollusks collected from the oyster beds along the Atlantic Coast. A certain kind of mollusk, known as the pearl oyster, secretes within its shell the pearls of commerce. These are formed of a material similar to that found on the inner layers of the fresh water mussel. Fig. 133.— The snail. E. Reptiles 140. The turtle. — The body of a turtle may be divided into four regions; namely, head, neck, trunk, and tail. The larger part of a turtle, the trunk, is covered by a shell, and to this shell the bony skeleton is firmly united. The two pairs of legs, however, are freely movable, but can be drawn within the shell for protection. The toes of the feet are armed with sharp, curved nails, and the legs are covered with scales. The legs are used for walking and also for swimming. In some turtles the legs become broad and flat and are of but little use except for swimming. The head, neck, and tail can also be drawn into the shell. Scales cover the neck and part of the head. The jaws of the turtle, often called the beak, possess no teeth. The eyes, protected by the eye- lids, the nostrils, and the ear openings, are readily seen. Turtles reproduce by means of eggs, which are comparatively large. Turtle eggs are often used for food. These animals breathe throughout their entire life by means of lungs. 186 ANIMAL BIOLOGY 141. Suggestions for the study of the turtle. — Turtles are easily kept at home or in the laboratory. The pupil should verify the “Se Se Fic. 134.— Lizard of the Southwest (commonly known as the “horned toad”’). statements given above concerning the turtle, and should then write an account of his observations in his notebook; or a well-labeled drawing will cover most of the ground. The pupil should also ob- serve and describe in his notebook the methods by which the turtle Fic. 135.— The rattlesnake. feeds, crawls, swims, and protects its head, legs, and tail. 142. Relatives of the turtle. — Animals related to the turtle are the lizards (Fig. 134), alligators and crocodiles, and snakes (Fig. 135), all of these animals being known as reptiles. None of the reptiles, other than the turtles, possess a shell, but all are covered with scales, and have toes armed with claws, except ADDITIONAL ANIMAL STUDIES 187 the snakes which have no appendages. Unlike the turtles the jaws of all other reptiles contain sharp teeth, used in holding their prey, and in the rattlesnake and copperhead some of these teeth are provided with poison glands. None of the other reptiles in the northern part of the United States are in any way dangerous to man. Indeed, many snakes destroy large numbers of rats and mice, while lizards catch large numbers of insects. The hide of the alligator is of considerable value for leather. All reptiles breathe throughout their life by lungs, and most of them reproduce by eggs, which are hatched by the warmth of the sun. F. Mammals 143. Characteristics of mammals. — In this class of vertebrates are included domesticated animals such as the cow, sheep, horse, camel, dog, and cat. Let us consider the structure of some of these Fie. 136. — The sperm whale. animals to see why they should be grouped together. We are familiar enough with the animals named above to know that they all have a head, neck, trunk, and tail and that these regions are covered with hair. A few mammals, e.g. the baboons, have no tail, and a few are nearly destitute of hair, like the whales (Fig. 136) ; but all of them nourish their young on milk produced in certain organs known as mammary glands; hence these animals are called mammals. The organs of the head, namely the ears, eyes with eyelids, and the nostrils, are prominent in all common mammals, but vary in size and shape. The jaws have teeth set in sockets, but the number and kinds of teeth vary greatly. Rats, rabbits, and squirrels, for 188 ANIMAL BIOLOGY example, have sharp cutting teeth (incisors) and grinding teeth (molars). Others, e.g. dogs, cats, lions, and tigers, have sharp pointed incisors and molars and in addition long canine teeth for tearing their food. In horses, cows, and other herbivorous animals the grinding teeth are especially developed, while canine teeth are either wanting or are relatively small. All these animals have four legs, but the relative size of the front and hind legs may differ greatly. In a kangaroo, for instance, the a //); DAS UNT/... Splint se Fic. 137. — Skeleton of the horse. hind legs are very large, while the front pair are so small as to be practically useless. Then, too, the nails on the toes vary con- siderably. The fingers and toes of man are protected on a surface by nails. A horse has only one toe on each foot, and the nail for that toe is developed into a hoof. Cows and sheep have two toes on each foot similarly protected. On this account these mammals and others like them are called the hoofed mammals. ADDITIONAL ANIMAL STUDIES 189 An examination of the skeleton of a horse (Fig. 137) or of most mammals, shows that the skeleton consists of bones similar to those of man. Thus, for instance, there is the spinal column made up of a series of more or less similar bones, with a skull that may vary a great deal in shape from that of man, but still may consist of similar bones. The shoulder bones and hip bones can be readily distin- guished. The bones of the legs are for the most part much alike, but in the foot there is frequently a wide variation, as in the case of © the one-toed foot of the horse, the two-toed foot of a cow, the three toes of the tapir, the four of a hippopotamus, and the five of the dog or of man. 144. Suggestions for the study of a mammal.— Follow the gen- eral account given above and describe the corresponding structures of a horse, dog, cat, or other mammal. Thus, for instance, name the regions present, and describe the character of the covering of each region. Then describe the situation and parts of the eyes, the situation, size, and shape of the external ears, the location of the nostrils, and soon to the end of the study. Lastly, describe the methods of locomotion of the animal, and its food and feeding habits. 145. Economic importance of mammals.— The mammals in- clude many of our most useful animals as well as those that are very dangerous. Our common beasts of burden, horses and mules in this country, the llama of South America, the elephant and camel of Asia and Africa, are all mammals. This group of animals also fur- nishes us with an immense amount of material valuable for food or clothing (e.g. the cow, deer, sheep, pig, seal). The group of car- nivorous mammals contains one of man’s most devoted friends and protectors, the dog. To the same order as the dog, however, belong the wolves, lions, tigers, hyenas, and wild cats; all these have canine teeth which they use with deadly effect in tearing their prey. The gnawing mammals (e.g. rats and mice) besides being a nuisance, do a great deal of damage. The rat also scatters diseases like cholera and bubonic plague. Some rodents, the beaver, for example, 190 ANIMAL BIOLOGY are valuable on account of their fur. The rapacity of man, however, has nearly exterminated these very interesting animals. G. Classification of Animals 146. Vertebrates and invertebrates. — All animals may be divided into two great groups, known respectively as vertebrates and inverte- brates. To the first group belong the animals that have a “ back- bone ” or spinal column composed of a series of bones known as vertebre. To this group belong fishes, frogs, turtles, birds, rabbits, and human beings, for all of them have a spinal column made up of vertebre. Insects, earthworms, and oysters, on the other hand, have no backbone; hence, they are called invertebrates (i.e. ani- mals without vertebre). 147. Summary of the classification of the invertebrates. — While the vertebrates, on account of their size, are more familiar to most people, in reality there are a great many more kinds of inverte- brates than vertebrates. For example, over 300,000 different species of insects have been described, more than all other species of animals put together. The invertebrates are divided by zodlo- gists into ten or more branches or subkingdoms, some of the most common of which are named in the table on pages 192 and 193. 148. Summary of the classification of the vertebrates. — The vertebrate branch of the animal kingdom is divided into five distinct classes. The striking characteristics of each of these classes will be seen by studying the table on page 194. 149. Reproduction among the vertebrates.— Among the ani- mals belonging to the two lowest vertebrate groups, namely, the fish and amphibia, the female forms eggs within the body and deposits them in the water. Before these eggs can develop, however, they must be fertilized by sperm-cells produced by the male, and this is likewise true of all the higher animals and plants. The fertilized eggs develop into embryos by the process of cell division, and enough food is stored in the egg to supply the young animal until it can secure its own food. Much the same is true also in the case of rep- ADDITIONAL ANIMAL STUDIES 191 tiles, except that the eggs are usually laid in the sand and left to develop by the warmth of the sun. There are, however, certain exceptions to the general statements made above. Some of the sharks, for example, and certain of the snakes, instead of depositing eggs that develop into embryos in the water or on land, retain the eggs, and the young are born in a form much like that of the adult. Very few of the animals belonging to the classes that we have been discussing (namely, the fishes, amphibia, and reptiles) ever take any care of their young. The great majority of birds, however, not only build nests in which to lay their eggs, but they also brood over their eggs until they are hatched, and then the parents feed the young until they are ready to fly. A few of the lowest mammals, like most of the vertebrates named above, lay eggs. By all the common mammals, however, the eggs are not laid, but as was the case with certain sharks and snakes, the eggs develop into a form resembling the parent, before being born. All mammals at birth, unlike birds, are unable to eat the food that is used by their parents. Hence, a form of food that is easily digest- ible must be furnished. This is secreted by certain cells of the adults in the form of milk. The masses of cells that secrete milk are known as mammary glands, and because of the presence of these glands in all animals of this the highest group of vertebrates, this class is known as the mammals. ANIMAL BIOLOGY 192 Apoq pedeys “Tq 94} Sur ~joe1yu0D pus susiepue sq = |yynour 04 pooy WOT}OULOD0T UO | BULIQ «YOY 5 Aired YsyATae | spjeo surdurys J9}eM aures OY pus esuys =| yim potrd Aq peyyeq =| auo AqIABO (qo81} 0AT]S9 einyeut ur |-dns sepoeqyuey | Jolajur pue | sanseSip pue soysyAyer | -tp AdoTjor) poxy ore syeiod | jo suvout Ag | ole}xa JoOsTPEDQ | AytAva Apog s[eio_n | 248194 U9[MO suey 89]SBM -sfs snoalou aAouwoad Jo ‘A1078~N9 ST]99 943 | PUB s][e0 oYy =| -aTO ‘aAT}SOSIP If@ 0} pooy T[@ 0} uwedAxo qnoyyiM = ynq pexg ore = Bulg Joyem Jo | Sutq 1078AA Jo ‘por[a0-AUeUL. saduods ‘wi0f | syuadimo vipa =| syuadmmo wifto §=| — Apoq ey} esuods (SuLresq einyeur ey} Uy | jo suveut Ag} jo suvou Ag | JoAO [[B sodog | y}8q UOUTOD | -910d) BIajLIOg wise[d -0}01d ay} ][® s[TeuIUe jo jUsUTAAOUL spodop poT[20-o]8urs sy} Aq JO | -nesd 10 wy =| Joo Joooevjns | oy} [7B sepnyo eqeoury (speurue ello josuvour Ag | jo suvew Ag | sayno YySnomyy, | -ur dnoss sm, wumnpeureieg | IY) voz0j01g NOILOWODO'T SNIGEaA YT DNIBLVaU Gg SOILLSIUALOVUVAY) HONVUg HO GOBLET dO dOHLAIL 40 GOHLET IV4UENaY EIGN 40 GWVN 193 ADDITIONAL ANIMAL STUDIES ° ysy Aero UIS}OTOUIUILMS pue uouwlop 4 -q@ Jo suvowl Ag “e90BiSn1o UL §109SUI syed =| ‘s]]Is / syoosulr sosepuodde siapidg ul SsUuIM pue ygnou poyurof | ur saqny sre pezutol ‘Apoq Ba0B4snID |(190] poyutofl) sso] JosuvourAg | jo suvour Ag|jo suvam Ag | poy,uesmsog syoesu] epodoiyy1y « JOOF ,, IepNo s[reus ul -snur josuvaur | onsu0ysuidse1 fq wonouos |Aq ‘yynow -O] uo ALred o4uL pooj s[teus pue suey | Sutiq 4%q4 ULYS {STOUT Teys £q Treug 93848 4[Npe UT SUIv[D UT BITIO | “4Jos Io ‘STIs pereaoo Ale we) (perpoq poxy o1v S19}sAQ | Jo suvour Ag | jo suvaur Ag | -nsn ‘Xpoq 4jJo9 IaqysAQ | -3JOS) vosnq[OyT sopstiq Aq pepre ‘syueur -3o9S 9} SUL sesepued -joe1jU00 pus -de poejutol SuIyesuola | puo ON ‘SSULI UT £q womow IOLIE}Ue Ye urs = |pesueiae Apog (ssuLt -090] UO Arreo =| YJNOW Suryons qystour ‘4J0s pe yesuojea jo opeur SUIIOMYJIGAY | Jo suvou Ag] jo suvaut Ag|oy} jo syieg WIOMYe” | Apoq)eprpuny 194 ANIMAL BIOLOGY ; WaRrM OR Gi: | asics (OMEEM) "Core. Aare yes On Fishes |Codfish | Scaly | Cold | Fins Gills skin | blooded : Am- Frogs |Naked}| Cold |Two pairs ap-|Gills in tad- phibia skin | blooded} pend. Toes| pole, lungs in without claws| adult Reptiles} Turtles | Scaly | Cold | Two pairs ap-j/Lungs through- Lizards | skin | blooded| pend. Toes| out life with claws Birds |Robins |} Skin | Warm | Anterior ap- | Lungs Sparrows] with | blooded} pend. wings; feathers poster. ap- pend. with claws Mam- | Cows Skin | Warm | Paired append.} Lungs mals | Man with | blooded} with nails hair 1 Cold-blooded animals are those animals in which the tempera- ture of the blood changes with the temperature of their surround- ings. Warm-blooded animals, on the other hand, maintain under normal conditions an almost constant temperature. The tempera- ture of the human body, for example, is 98.6° F., which is usually higher than the temperature of the earth, air, and water; con- sequently when we touch a fish or frog, the animal feels cold. LOUIS PASTEUR CHEMIST AND BIOLOGIST ‘‘He saved more lives than Napoleon took in all his wars.” See pages 168-170. HUMAN BIOLOGY CHAPTER I THE GENERAL STRUCTURE OF THE HUMAN BODY 1. Regions of the body.—In man and in most other mammals one can distinguish at least three regions; namely, the head, neck, and trunk. To the trunk are attached two pairs of appendages; namely, two arms and two legs, or, as they are more often called in the descriptions of the lower animals, the four legs. If the front wall of the trunk (com- posed largely of skin and muscle) were removed, it would be found that this region of the human body is divided into an upper story or chest cavity (Fig. 1), and a lower story or abdominal cavity. These two cavities are separated from each other by a flexible partition called the diaphragm, which is composed largely of muscle more or less in the form of adome. The chest and abdominal cavities, separated by a diaphragm, are characteristic of all mammals. 2. Organs of the body.!— When we study the body more closely, especially its interior, we find, in various regions, parts that carry on special kinds of work (Fig. 2). Within the chest cavity is the heart, which forces blood through the 1 Hach of the structures named in this paragraph should be demon- strated on_a manikin or a chart before the textbook lesson is as- signed. While studying the lesson, the pupil should find in Fig. 2 each of the organs named. B 1 2 HUMAN BIOLOGY body. Here, also, are the lungs, which take in oxygen and give it to the blood, and which remove carbon dioxid, water, and other waste matters from the blood. Below the dia- phragm are the stomach and the intestines, the liver and the spinal column ‘composed of vertebra and cartilage) spinal cord (composed of nerve cells and nerve fibers) --chest cavity ~ -diaphragm Fic. 1.— Longitudinal section of trunk (sidé view). pancreas, all of which help to change our food into liquid form ready to be used by the body. All these and other parts of the body are called organs. An organ is a part of a living body that has’ some special work to do; this special work ts called its function. Our hands, for example, are organs THE GENERAL STRUCTURE OF THE HUMAN BODY 3 because with them we do some special work like writing, sewing, or playing the piano. 3. Tissues of the body. —- When we squeeze the arm or the hand, we feel the hard bones within that form the skele- = heart right lung ~ left lung — diaphragm liver = =stomach (opened) — large intestine ~ small intestine (opened) large intestine — opened Fig. 2.— Organs of chest and abdomen (front view). ton. We can raise from the bones the softer fleshy material, which is composed of muscle covered by skin. By clenching the fingers tightly we can see and feel on the inner side of the wrist the tough cords or tendons of connective tissue that 4 HUMAN BIOLOGY attach thé muscles to the bones. If we run a clean needle point into the finger, blood flows; in this way we discover another of the materials found in our hand; namely, blood. This experiment also demonstrates that the human body has some structures by the help of which sensations of touch or pain are perceived. All the parts of the hand we have been enumerating are known as tissues. For the present a tissue may be defined as one of the building materials of which an organ ts composed. In the hand we have found evidence of the presence of bone tissue, muscle tissue, connective tissue, blood tissue, and nerve tissue. Other kinds of tissue will be discussed in the pages that follow. In order to go farther in our study of structure we need the aid of the compound microscope. With this instrument we discover that the tissues are by no means the simplest part of an animal. 4. Cells lining the mouth. — Laboratory study. Materials: Cells from the human body may be readily prepared by gently scraping with the finger nail the mucous membrane lining the mouth and then rubbing the material thus obtained on a clean glass slide, adding a drop of water and a cover glass. The cells may be stained with iodine in order to show the nucleus more sharply. If time allows, prepared sections of the brain, intestines, skin, and other organs of the body may well be shown. Examine with the low power of the compound microscope the cells prepared as described above. 1. Describe the form and color of each cell before it is stained with iodine. 2. In the cells stained with iodine notice a body, usually near the center, that is more deeply stained than the rest of the cell. This is the cell nucleus, and the rest of the cell is known as the cell body. The nucleus may be seen in the unstained cells as a denser portion. THE GENERAL STRUCTURE OF THE HUMAN BODY 5 a. Name, now, two parts of a cell from the membrane lining the mouth. b. State the form and position of the cell nucleus. 3. Make a drawing of two of the cells described above (each cell to be represented about an inch in diameter). Label cell body and cell nucleus. 4. (Optional.) Demonstrate by the use of prepared slides, pic- tures, or charts that the brain, the intestine, and other organs of the body are composed of cells (Fig. 3). 5. Cells and protoplasm. — Under the microscope cells at first appear to be only plane surfaces surrounded by lines (Fig.3). In reality, however, each cell has not only length and breadth, but also thickness. Cells in animals and human beings differ from those in plants in never hav- ing cell walls of cel- lulose, and often cell walls are entirely wanting. If pres- liver cells * cells from the mouth nerve cells from the cells windpipe wee mus le cells Fic. 8. ———— from tissues of body. ent, the cell wall is so transparent that it is possible to look through it and see the cell body and nucleus within. The discovery of these minute bodies of which organs are composed was not made until about the middle of the last century (1848). With the rather imperfect microscopes then in use the two discoverers, Schleiden and Schwann, could see the walls only, and they did not know, as we now 1 Because of the importance of emphasizing cellular structure, the substance of §§ 42 and 43, ‘‘ Plant Biology,”’ are here inserted. 1 6 HUMAN BIOLOGY know, that the most important part of the cell is not the lifeless wall of cellulose, but the living substance which is found inside the cell wall, making up a large part of the cell body and cell nucleus. To this substance is given the name protoplasm. We know now that the living substance or pro- toplasm is the essential part, while the wall may be missing, so that in such a case there is no resemblance to a cell or box. Biologists now understand a ceil to be a bit of proto- plasm (cell body) containing a nucleus (which is a denser por- tion of the protoplasm). Protoplasm, when examined with the highest powers of the microscope, appears as a colorless, semifluid substance, in which are often seen solid particles or granules, which are probably little masses of food. The nucleus, as already stated, is commonly found near the center of the cell, and is composed of protoplasm denser than the protoplasm of the rest of the body of the cell. The appearance and composition of the protoplasm surrounding the nucleus, that is, the cell body, may be well represented by raw white of egg; but in making this comparison one should bear in mind that the white of an egg is not living substance. 6. Assimilation, growth, and cell division. — Within the pro- toplasm are foods in solution (such as sugar protein, and mineral matters). These are used by cells in their growth and repair, and in the various kinds of work that they carry on. In the human body, as in plants, the food materials are gradually changed by protoplasm into living substance like itself. To this process is given the name assimilation (Latin, ad =. to + similis = like). Asa result of the process of assimilation the amount of protoplasm of course increases and the cell grows. Were this process to continue indefi- nitely, cells would come to be large in size. This, however, THE GENERAL STRUCTURE OF THE HUMAN BODY T does not occur; for when a cell reaches its normal size, the nucleus divides (Fig. 4), and the halves separate from each other to form two nuclei. The cell body now divides into two parts, and cell walls are formed between the two cells. Thus are produced two cells, each having its own nucleus, and these in turn assimilate and divide. In this way the number of cells increases with the growth of the body. 7. Cells ofthe lz ect acadbed blood. —If we 4, cell before divi- B, cell with divided C, single cell divided : sion. nucleus. into two cells. were to examine with the com- Fic. 4.— Cell division. pound micro- scope a drop of fresh blood,! we should find that it is not the simple red liquid it seems to be; it consists of solid particles, called blood corpuscles, floating in a watery liquid known as blood plasma. These corpuscles are single cells. Two kinds can be distinguished, which from their color are known as red corpuscles and white corpuscles (Fig. 5). There are three hundred to seven hundred times as many red corpuscles as white. We shall first consider the white corpuscles. Each consists of a minute bit of protoplasm in which is imbedded a nucleus. These cells of the blood 1 The blood may be easily obtained by tying.a cord tightly about the finger and then pricking it with a needle cleaned by an antiseptic like peroxid of hydrogen or by heating it in a flame. A drop of blood is squeezed out upon a glass slide and covered with a thin cover glass. 8 HUMAN BIOLOGY have a characteristic method of locomotion, in the process of which they change their shape; they can creep along in a direction opposite to that of the blood current, and they red corpuscles surface view white corpuscles nucleus not seen ted corpuscles edge view , | white corpuscles ” ¢ nucleus at centre of each Fic. 5.— Cells of human blood. have even been seen forcing their way through the walls of small blood vessels by pushing out slender processes called false feet. They then wander about in the tissues of the body, and, as we shall soon see, do us great service. The white corpuscles closely re- 10,000,000 red semble in structure and functions a kind corpuscles could : 3 ihe ee of single-celled animal called the Amceba in this square (A. B.,! Fig. 126). The red corpuscles have no power of in- dependent motion. They are circular Fic. 6.—Number of disks, concave on both surfaces. Some a sas aaa in 2 idea of the minute size of these cells may be gained from the fact that ten millions of them would just about cover a space one inch square. There is no nucleus in the red corpuscles; they are, however, formed from cells having a nucleus. 1A. B. = ‘‘ Animal Biology.” THE GENERAL STRUCTURE OF THE HUMAN BODY 9 8. Cells in other tissues. — It has been demonstrated that nerve tissue, muscle tissue, and other building materials of the body are all composed of cells (Fig. 3). A tissue may now be defined as a building material of the body, composed of cells of the same kind. CHAPTER II MICROORGANISMS AND THEIR RELATION TO HUMAN WELFARE I. Structure AND FuNcTIONS OF BACTERIA 9. Bacteria:! their microscopical appearance and size. — In the preceding chapter we considered to some extent the organs, tissues, and cells of the human body. However, before we discuss further the structure and functions of these various parts of our bodies, we shall study in some detail certain microscopic plants which have a most intimate relation to human welfare. Chief among these are the tiny organisms known as bacteria. Every one is familiar with the fact that if a bouquet of flowers is left for some time in a vase of water, the stems decay and disagreeable odors are given off. This is a com- mon example of the action of bacteria, for all decay is due to the work of these organisms. When we come to examine the flower stems or the putrid water, we find a slimy scum. If we put a drop of this scum on a slide, cover with a cover glass, and examine with the highest powers of the microscope, we usually see many different forms of living things. Some of them appear relatively large, and these, as we have already seen (A. B., Chapter VI), are single-celled animals. A closer examination will disclose countless numbers of very minute, 1The substance of this section, and several of those that follow, appear in Part I, ‘‘Plant Biology.’”’ Many teachers, however, find it impracticable to discuss bacteria until the work in human biol- ogy is taken up ; hence the repetition of this material in this volume. 10 MICROORGANISMS AND HUMAN’ WELFARE 11 colorless organisms; these are the bacteria. A careful study of many kinds of bacteria shows that they have several char- acteristic shapes (see Fig. 7), by means of which they may be roughly classified. Some are rod-shaped (like a firecracker), some are spheri- cal, or egg-shaped, and still others are a spiral-shaped. | A ane Each bacterium is peataecnemerernneeeR F Ble a tiny bit of trans- ; Zee RE. q lucent protoplasm, BEB oS 3 inclosed in a cell Se %2000 20 wall of cellulose. Sse Sa bORREE eS) ee Thus far no nu- ae cleus has been dis- ( ) covered in any ; kind of bacteria. W ff WY \ yy Because of their P cellulose walls, and because of spiral bacteria (spirilla) their likeness to certain low .forms f ly of green plants, bi- l i A ologists now regard 1 > these organisms bacteria _bacteria with reproducing spores as plants rather than animals. ' Some kinds of bacteria have one or more long, hairlike projections from the ends, called cil’i-a, which give the germs still further resemblance to firecrackers. These cilia lash about rapidly, and thus drive the cell through the water. The spiral bacteria roll over and over, and advance in a spiral path like a corkscrew. Fig. 7.— Various forms of bacteria. 12 HUMAN BIOLOGY It is very difficult to get any clear notion of the extreme minuteness of bacteria. It means little to say that, the rod-shaped forms are spp of an inch in length. The im- agination may be somewhat assisted if we remember that fifteen hundred of them arranged in a procession end to end would scarcely equal the diameter of a pin head. 10. Microscopic study of bacteria. —— Laboratory demon- stration. : Place on a glass slide a drop of the scum found on the surface of a hay infusion, and cover with a cover glass. Examine with the highest powers of the compound microscope. 1. Describe the source of the material you are examining. 2. What is the apparent color of the tiny bodies (bacteria) that you see? 3. Which of the different forms of bacteria shown in Fig. 7 do you find? Draw enlarged figures of each of the shapes that you find. - 4. Do any of the bacteria seem to be in motion? If so, describe the motion. 11. Reproduction of bacteria.— When conditions are favorable, the production of new cells goes on with marvelous rapidity. The process is something as follows: the tiny cells take in through the cell wall some of the food materials that are about them, change this food into protoplasm, and thus increase somewhat in size. The limit is soon reached, however, and the bacterium begins to divide crosswise into halves. The mother cell thus forms two daughter cells by making a cross partition (cell wall of cellulose) between the two parts (Fig. 7). If the daughter cells cling together, a chain or a mass is formed. Oftentimes they separate entirely from each other. In either case the whole mass of bacteria is called a colony. It usually takes about an hour for the division to take MICROORGANISMS AND HUMAN WELFARE 18 place. Suppose, then, we start at ten o’clock some morning with a single healthy bacterium. If conditions are favorable, there would be two cells at eleven o’clock, and by twelve o’clock each of these two daughter cells would form two granddaughter cells; the colony would then number four individuals. Should this process continue for twenty- four hours or until ten o’clock on the day after the single bacterium began its race, the colony would number 16,777,- 216 bacteria. ‘It has been calculated by an eminent biologist,”’ says Dr. Prudden,} “ that if the proper conditions could be maintained, a rodlike bacterium, which would measure about a thousandth of an inch in length, multiply- ing in this way, would in less than five days make a mass which would completely fill as much space as is occupied by all the oceans on the earth’s surface, supposing them to have an average depth of one mile.” 12. Spore formation in bacteria. — Such startling possi- bilities as those suggested in the preceding section fortunately can never become realities, for favorable conditions soon cease to exist and the cells either die or cease to multiply. Sometimes, when food or moisture begins to fail, the pro- toplasm within each cell rolls itself into a ball and covers itself with a much thickened wall. This protects it until it again meets with conditions favorable for growth. The process we have been describing is known as spore formation ; the tiny protoplasmic sphere is called a spore, and its dense covering a spore wall (Fig. 7). In this condition bacteria may be blown hither and yon as a part of the dust. They may be heated even above the temperature of boiling water without being killed. When at length they settle down on the Story of the Bacteria,’ by Dr. T. Mitchell Prudden. G. P. Putnam’s Sons, New York. BS ae 14 HUMAN BIOLOGY a moist surface that will supply them with food, the spores burst their thick envelope, assume once more their rod- shaped or spiral form, and go on feeding, assimilating, and reproducing their kind. II. OccuRRENCE OF BACTERIA 13. Are bacteria present in the air. — Laboratory demonstration. Materials: The best method of cultivating bacteria is by the use of a nutrient agar mixture in Petri dishes, which is prepared as follows : — To prepare 1000 cc. (about a quart) of agar mixture, weigh out 10 grams of salt, 10 grams of peptone, 10 grams Liebig’s beef ex- tract, and 10 grams of agar. Measure into an agate stewpan 1000 cc. of water, and stir in the salt, peptone, beef extract, and agar (the latter having been cut into small pieces). Heat the mixture in a double boiler until the agar is wholly melted. Slowly stir in just enough baking soda to cause red litmus paper to turn blue; i.e. the mixture should be slightly alkaline. When the pieces of solid agar have all disappeared, the hot liquid should be filtered into flasks of 250 ce. capacity through several rather thick layers of absorbent cotton placed in a funnel. This filtration might well be done by placing the flasks in a steam sterilizer. If the filtrate is not clear, the liquid should be poured through the same layers of cotton till it does become clear. Care should be taken to keep the agar mixture hot during the filtering process, otherwise the agar will not pass through the cotton. When the flasks are nearly full, plug the mouth of each with a large wad of cotton batting, put them into a steam sterilizer, and heat them at least thirty minutes on each of three successive days to make sure that all germs and their spores are killed. The flasks of agar may then be kept as a stock mixture until needed. Carefully clean and dry enough Petri dishes to supply, if pos- sible, seventeen or more dishes for experiments with each division MICROORGANISMS AND HUMAN WELFARE 15 of students. Put the ‘closed dishes in an oven and heat to a high temperature (150° C.) for an hour to kill any germs or spores that may be on the dishes. Allow the oven to cool before opening the door; otherwise the dishes are likely to crack. To fill the Petri dishes, melt the agar mixture in a steam sterilizer, then arrange the sterilized Petri dishes along the edge of a horizontal surface. Carefully remove the cotton plug from the flask, lift one edge of the cover of one of the Petri dishes, pour enough of the hot agar mixture into the lower part of the dish to make a layer about an eighth of an inch deep, and quickly replace the cover on the dish. Quickly pour into each of the dishes in turn. After the agar has hardened, the dishes are ready for the experiments. Any agar mixture left in the flasks should be sterilized for thirty minutes on each of three successive days in order to make sure that it will keep for subsequent use. Treat several of the Petri dishes of agar as follows: Label the first dish No. 1 and keep it closed throughout the experi- ments. Place a second Petri dish on the desk of a pupil, remove the cover and thus for ten minutes expose the surface of the agar to the air of a classroom or laboratory; label it dish No. 2. In a similar manner expose the surface of dish No. 3 for ten minutes to the air near the floor of a corri- dor through which classes are passing. Put all three dishes aside for a few days in a dark place where the temperature is 80° to 90° (e.g. in a furnace room), and then examine each dish. 1. State the difference in the treatment of dishes No. 1, No. 2, and No. 3. In what respects have all three been treated alike? 2. The spots on the surface of the agar are colonies of bacteria, each one of which has developed from a single bacterium (see Fig. 11). Which of the three dishes has the largest number of bacteria colonies? 3. Suggest a reason for the difference in the number of bacteria colonies in the three dishes. 4. What do you infer, therefore, as to the presence of bacteria in the air? 16 HUMAN BIOLOGY 5. (Optional.) Make careful drawings at intervals of several days to show the difference in the number of colonies in the dishes, and the change in the size and appearance of the colonies. 14. Are bacteria present in water, milk, and other foods? — Laboratory demonstration. Allow the water to run from the faucet for several minutes, and then spread a drop on the surface of dish No.4. Spread a drop of milk on the surface of the agar in dish No. 5. On the agar surface of dish No. 6 put a bit of raw meat, a bit of apple peel, and bits of other kinds of food. Put the dishes in a warm, dark place as directed above, and examine at the end of several days. 1. State the difference in the treatment of dishes No. 4, No. 5, and No. 6. 2. In which of the three dishes do you find bacteria colonies? Describe the colonies in each dish as to position, number, and color. 3. What do you infer as to the presence of bacteria in water, milk, and other foods that you have tested? 15. Are bacteria present on various parts of the human body ? — Laboratory demonstration. Touch the surface of the agar in dish No. 7 with the finger tips; lay a hair on another part of the surface, and touch a third part with a toothpick that has been used to scrape the teeth. Put the dish in a warm, dark place as above, and examine at the end of several days. Describe fully this experiment, stating your observations and conclusions. 16. Distribution of bacteria.— From our study of the culture dishes we have learned that bacteria are very com- mon organisms. In fact, they are doubtless the most abundant of all living things; for they are found not only in air, water, and milk; not only in countless numbers wherever dead plant or animal material is allowed to accu- mulate; but also, unfortunately, in living tissues. MICROORGANISMS AND HUMAN WELFARE 17 17. To determine conditions favorable and unfavorable for the growth of bacteria. — Laboratory demonstration. A. The effect of different degrees of temperature. — Expose for ten minutes three Petri dishes of nutrient agar to the air in a room or corridor when classes are moving about. Cover the dishes and label them No. 8, No. 9, and No. 10, respectively. Put dish No. 8 in a temperature of 80° to 100° F., and dish No. 9 in the refrigerator, or in some other equally cold place. Dish No. 10 should be put in a steam sterilizer and heated for thirty minutes on each of three successive days; it should then be kept in a warm, dark place. 1. Describe the difference in the treatment of dishes 8, 9, and 10. 2. At the end of a week examine each of the three dishes. What difference do you find in the relative number of colonies in them? 3. What do you conclude, therefore, as to the influence of each of these three different degrees of tempera- ture on the growth of bacteria? B. Pasteurization of milk.— (Optional.) If possible secure a Pas- teurizer! (Fig. 8). Carefully clean with soap and hot water, inside and out, four of the glass bottles, fill each . with milk that is fresh, and fasten on the stoppers. 1 Home Pasteurizers,— System Nathan Straus, —each supplied with bottles and stoppers, may be bought at the Nathan Straus Pasteurized Milk Laboratory, 348 East 32d St., New York City, or , at any of the Laboratory depots situated throughout the city. The manufacturer’s price for the entire outfit is $1.50. The authors are indebted to the Nathan Straus Laboratories for the cut of the Pas- teurizer, and for the directions quoted above. The circular also contains the following statements. ‘‘The advantage of Pasteuriza- tion over other systems, such as sterilization or boiling, consists in the lower degree of heat applied, which is sufficient to kill all noxious germs, while the nourishing quality and good taste of the milk are _retained. . .. Before use, warm the milk —in the bottles — to blood heat. Never pour it into another vessel. The milk must not be used for children later than twenty-four hours after Pasteuriza- tion. Never use remnants.” c 18 HUMAN BICLOGY Keep one bottle at the temperature of the laboratory, labeling it bottle No. 1, and put another, bottle No. 2, in the refrigerator. Pasteurize the other two bottles in accordance with the following directions : — “Set the bottles into the tray. . . . The pot is then placed on a wooden surface (table or floor) and filled to the three supports (in the pot) with boiling water. Place the tray <= INSIDE SECTION SHOWING BRACKET FOR TRAY ‘ wie PASTEURIZe, ; 5: *Ystem NathanSt™ Tig. 8.— Straus Pasteurizor. with the filled bottles into the pot, so that the bottom of the tray rests on the three supports, and put cover on quickly. After the bottles have been warmed up by the steam for five minutes, remove the cover quickly, turn the tray so that it drops into the water. The cover is to be put on again immediately. This manipulation is - to be made very quickly, so that as little steam as pos- sible can escape. Thus it remains for twenty-five MICROORGANISMS AND HUMAN WELFARE 19 minutes. Now take the tray out of the water, cool the bottles with cold water and ice as quickly as possible, and keep them at this low temperature till used.” Place one bottle of Pasteurized milk (No. 3) beside the bottle in the room temperature, and the other (No. 4) in the refrigerator beside bottle No. 2. 1. At the end of three days shake the two bottles kept at the room temperature and open them. Smell or taste of the milk in each. State your observations and gon- clusions. 2. Ina similar manner, test the two bottles that have been kept on ice for a week. State your observations and conclusions. 3. Why are milk, meat, and other foods of the kind put into the refrigerator, especially in summer time? Does this kill the bacteria? How do you know? 4. Why are meats cooked, milk Pasteurized, and fruits boiled before they can be kept for any length of time? C. The effect of lack of moisture. —Expose for ten minutes OG. EP Oey, 9 Rott two Petri dishes of nutrient agar in a dusty room or corridor (asin A above). Place the two dishes (No. 11 and No. 12 side by side in a warm room (over 90°). Cover dish No. 11 and leave dish No. 12 un- covered. Describe the similarity and the difference in the treatment of dishes 11 and 12. How is the agar mixture affected by removing the cover? In which dish do colonies of bacteria develop? What do you conclude, therefore, as to the necessity of moisture for the growth of bacteria? Why is hay dried before it is put into the barn? Name some foods used by man that are kept for a long time after being dried. As a conclusion from these experiments (in A, B and C) state what conditions you have found favorable for the growth of bacteria. 20 HUMAN BIOLOGY 7. State also what conditions you have found that hin- der the growth of bacteria. D. The effect of antiseptics.— Prepare a pure culture of bacteria in dish No. 13 in the following manner. Heat a dissecting needle on a piece of platinum wire in a hot flame to kill all the germs upon it. When it cools, touch a colony of bacteria in a Petri dish with the needle-point or wire; carefully raise the cover of dish No. 13 and make several scratches in the agar (the date of the experiment or the num- ber of the room may be scratched in this way). In a similar way prepare dish No. 14 and then pour over the surface some peroxid of hydrogen or othér antiseptic solution. When the dishes have been treated as described above, put them in a warm, dark place for several days? 1. Describe the preparation of dishes 13 and 14. 2. In which of the two dishes do you find no colonies of bacteria at the end of several days? 3. Peroxid of hydrogen is employed in treating wounds. How do you know that bacteria are killed by this treatment? III. Bacreria AS THE FRIENDS oF Man 18. Relation of bacteria to soil fertility. — Having dis- cussed somewhat the structure and functions of bacteria, we are now to consider the great importance of these mi- croscopic organisms to human welfare. In the first place, were it not for their never ending activity, all life upon the earth would soon cease to exist. Let us see why this is so. When animals or plants die, their bodies fall upon the ground, and had not these lifeless masses been taken care of, the whole surface of the earth would long since have been covered with a vast number of unburied organisms. All this dead material, however, as we have seen, is food for the countless MICROORGANISMS AND HUMAN WELFARE 21 bacteria; they cause it to decay, and thus decompose it into simpler chemical compounds that soak into the earth and may then be used in the nutrition of the higher oie And since plants are constantly taking from the soil the food materials that they need, this soil would tend to be- come less and less fertile were it not for the work of the bacteria that cause ‘decomposition. This is the reason why rotting manure adds to the fer- tility of soil. Again, it has been proved that certain kinds of bacteria directly in- crease the amount of nitrogen com- pounds that are so essential for plant growth. It has long been known that corn and other crops will grow better in soil that has just borne a crop of peas, beans, clover, or other members of the pea family. Within recent years an explanation of this fact has been found. When the roots of these pod bearing plants are examined, small swellings are seen (Fig. 9). These contain multitudes of bacteria that are able to take the free nitrogen from the air, where it exists in such abundance, and store it away in the Fic. 9.— Roots of horse bean, with tubercles. form of nitrates, which are very important mineral matter's needed by all crops. Since these bacteria can be put into soils that do not have them, it may be possible in the near future to restore much of the fertility that has been lost (Fig. 10). 22, HUMAN BIOLOGY 19. Relation of bacteria to the flavors of food. — Again, many of the flavors of food are due to the action of bacteria. The flesh of animals, for instance, that have just been killed, is often tough and tasteless. If allowed to stand, however, these meats become tender and acquire their distinctive fla- vors by the decomposing action of bacteria. A similar action takes place when butter or cheese ripens, and the dairy in- dustry has been perfected to such a degree that bacteria of certain kinds have been : ® proved to give rise to defi- y DN » f nite flavors, and these \ oa a Sf bacteria may be produced in pure cultures for the ( dairymen. ‘em & v4" 20. Bacteria in the in- f dustries. — Without the W® 5 \ 9 help of bacteria the prep- aN 2X aration of linen, jute, > © es ™® and hemp would be im- possible. All these valu- able products. are plant fibers which are connected with woody materials so closely that they cannot be separated without first subjecting the stems of flax, hemp, and jute to a process of decay in large tanks of water. Moisture and warmth induce the rapid growth of germs, and the resulting decay loosens the tough fibers so that they may be separated from the useless parts of the plant. The change of alcohol into vinegar is also caused by bacteria. Formerly in the preparation of indigo other forms of bacteria were all- important, but at the present time indigo is largely made artificially. Fig. 10.— Bacteria from root tubercles. MICROORGANISMS AND HUMAN WELFARE 23 IV. Bacteria AS THE Fors or Man 21. Injurious effects of bacteria. — Most of.the common bacteria are either harmless or distinctly beneficial to man- kind (18-20). The experiments we tried with milk (17, B), however, show that this kind of food soon sours unless it is kept in a very cold place. Every housekeeper knows also that meat and many other kinds of food quickly spoil if they are not cooked or otherwise preserved. In a following section we shall consider some of the methods that are used to prevent this decaying action of bacteria. Unfortunately, too, there are certain germs! that find favorable conditions for growth in living animal tissue, and by their growth cause certain diseases, some of which are tuberculosis, diphtheria, and typhoid fever. In later sections we shall learn that these disease-producing bacteria are all too common in dust, water, and foods; but we shall likewise see that scientists are fast learning effective methods of preventing the ravages of these disease-producing bacteria, which are called by Dr. Prudden ‘‘ Man’s Invisible Foes.” ? 22. Methods of food preservation. — We saw in (17, A and C) that bacteria thrive whenever they can get plenty of food and moisture, and. whenever the temperature is favor- able for their growth. We also learned that, whenever any one of these necessary conditions is wanting, bacteria cease to carry on their functions. If, then, we wish to 1 Disease-producing bacteria are commonly spoken of as germs or microbes. 2In general it is unwise and unnecessary that boys and girls should be taught much regarding the symptoms and effects of dis- ease; but since so much may be done to prevent these diseases that we have mentioned and others that afflict mankind, it is essential that the young should learn something of the deadly work of some of the germs which are all too common. 24 HUMAN BIOLOGY keep food from spoiling, we need only to bring about con- ditions that are unfavorable for the growth of microor- ganisms. For instance, everybody knows that meat, milk, and eggs must be put on ice in summer if they are to be kept for any length of time. Indeed, many food materials of this sort will remain in a more or less fresh condition for months or even years if they are in cold storage. It has been proved, how- ever, that food products kept in cold storage for a long time are often unsafe for human consumption. On the other hand, we demonstrated (17, A) that a high degree of heat will kill bacteria, and so meats'that have been cooked and milk thdt has been Pasteurized or scalded will keep longer than they do when left uncooked. If meats, vegetables, or fruits are heated to the boiling point in cans and sealed up at once, they may be permanently prevented from spoiling. Ham and herring are often smoked to preserve them, while pork and codfish are soaked in a strong solution of salt (brine) to keep them from the decaying action of bacteria. Another method of preserving food is by depriving it of water. Dried beef, apples, hay, and seeds will keep indefi- nitely if no moisture is allowed to get to them. Previous to the passage of the Pure Food Law by Congress in 1906, many unscrupulous dealers were accustomed to use borax, formaldehyde,! and other chemicals to prevent their food supplies from spoiling. Fortunately for the health of the consumer, this method of food preservation has been largely stopped. by the enforcement of the law to whish we have just referred. 1 Method of determining whether or not formalin has been added to milk. Into each of two test tubes or flasks put an equal quantity of fresh milk. To one of the glasses add a drop or two of formaldehyde solution. Then to each add a volume of hydrochloric acid equal to MICROORGANISMS AND HUMAN WELFARE 25 23. To determine the best method of cleaning a room.— (Optional Demonstration.) Select three rooms with rugs or carpets as nearly as possible of the same size and amount of dirt. Open Petri dish No. 15 and expose its surface for five minutes at the level of the table while one of the three rooms is being swept with a broom.. Ina similar man- ner expose the surface of dish No. 16 for five minutes to the air in a room that is being cleaned with a carpet sweeper, and dish No. 17 in the third room for five minutes while it is being cleaned with a vacuum cleaner. Close each of the dishes, label, and put in a warm place (90° to 100° F.) for several days. 1. Describe the preparation of dishes 15, 16, and 17. 2. What difference do you find in the relative number of bacteria colonies in the three dishes? 3. What do you conclude, therefore, as to the most effective method of removing dust and germs from a room? 24. Proper methods of sweeping and dusting. — From our experiments (13, 23) we have learned that large num- bers of bacteria are present in the air of rooms where dust is raised by the movement of people or by sweeping. Since each colony started from a single bacterium, it is easy to show the relative number of germs present.in the air under varying conditions (Fig. 11). The number of bacteria that may be found in a church, schoolroom, theater, or living room has been proved by a that of the milk and a drop of ferric chloride (made by dissolving a spoonful of ferric chloride in a quart of water). Put both dishes of milk into a dish of boiling water and stir or shake frequently for five minutes. 1. Describe the preparation of the experiment. 2. At the end of five minutes state the color produced in the milk in each of the two test tubes. 3. How, then, can you determine whether or not formalin has been added to milk? 26 HUMAN BIOLOGY long series of experiments to be enormous, for with the or- dinary methods of “cleaning” these rooms, very few of the germs are removed. When a room is swept, most of the light dust particles are raised from the floor and mingled with the air. After a short time the room is “ dusted,” often with a feather duster. The bacteria which may have settled are whisked off again into the air. Experiments have shown, too, that the number of germs in a room is not materially diminished by ventilating currents, unless there is a strong draught. Most of this germ dust can, however, be removed from our homes if they are cleaned in a proper manner. In aroom that has not been used for three or four hours practically all of the bacteria and fine dust particles have settled out of the air upon the horizontal surfaces. For dusting, a cloth should always be used. ‘‘ Dustless dusters ’’ may be bought or prepared by soaking a piece of cheesecloth or flannel in a mixture of wax and turpentine, or by slightly sprinkling cheesecloth with water. By the use of these cloths most of the particles of dirt may be taken up and then removed from the cloths by washing. If carpets, rugs, and draperies are then cleaned with a vacuum cleaner, practically no dust is raised (Fig. 11); hence, further dusting is unnecessary. Careful investigation has demonstrated that the use of a vacuum cleaner on surfaces that may be washed or wiped with a cloth is too expensive a method of cleaning, and that it is not nearly as effective. It is much more hygienic to have floors covered with rugs, for if a vacuum cleaner is not available, the dusty rugs and draperies may be removed from the room and cleaned in the open air. In general, a carpet sweeper is to be preferred to a broom as a means of cleaning carpets, since, as Fig. 11 shows, fewer germs are stirred up when the former is used. Cysleg [eoso[90Z *X ‘N ‘a1oqueg "yY “IW Aq peydeisojyoyg) “3z ‘duo 0300}00} vog 9=‘duIddaMS 10}Je ‘MOI IOMOT : SUIdeVMS BIOJOq SBTUO[OD BIIE}OVq MOYS SoYysIp jo MoI IaddQ —'[T ‘Ol 27 *queulliedxe “‘quourtiedxa “‘queuliedxa “quoulliedxe wo00I1q woo1q pue qadeoms Jaues[o Aig ‘d qoded yam °0 yedieg -g wuMnoeA ‘F & = & <) cS) S < : cs) Q > x RQ a Ny a qq oS RS oS ° && 28 HUMAN BIOLOGY If brooms are used, small pieces of crumpled newspapers or tea leaves should be moistened and scattered on the floor before the sweeping is done. In cleaning public buildings, the floors should first be sprinkled with moist sawdust and then the coarser dirt collected by brushing with hair brooms. The floors should then be washed each day if possible.2 Dirty streets, too, are a constant source of dust infection. Most of the irrita- tion and possible diseases from this source would be avoided, ' Figure 11 shows, so far as bacteria are concerned, the compara- tive results obtained by four methods of sweeping. Four rugs of the same size and approximately the same amount of use were selected, and placed at night in four different rooms. Early the next morning a Petri dish was uncovered in each room, and thus the nutrient agar of each dish was exposed to the air of the room for five minutes ; after which the dishes were covered. A second set of four dishes was then opened in turn for five min- utes while the four rugs were being cleaned as follows. Rug D was swept with a dry broom; rug C was covered with pieces of wet newspaper and then swept with a broom; rug B was cleaned with a carpet sweeper ; and rug A was cleaned with a vacuum cleaner. All of the eight dishes were then closed and kept in a warm room for five days and at the end of that time were photographed. (See Fig. 11.) The number of bacteria colonies in each dish were counted, and the results are expressed in the following table : No. C No. C No. Times Cotonres ec aaleaee pol Gamerna WEN ta BY Dish D 4 1190 297+ Dish C 6 436 72+ DishB .... 7 135 19+ DishA .... 25 118 4+ Hence over four times as many bacteria were stirred up by a car- - pet sweeper as by a vacuum cleaner, eighteen times as many when the sweeping was done with a broom and wet paper, and over seventy times as many when a dry broom was used. 2 We are indebted to Mr. John H. Federer, Superintendent of the New York Public Library building, for valuable information con- tained in the preceding paragraphs. MICROORGANISMS AND HUMAN WELFARE 29 however, if the citizens insisted that the streets be kept watered, especially when they are swept. Street sweeping and the removal of garbage should be done as far as possible at night. 25. Treatment of cuts. —A vast amount of discomfort. and possible danger from bacterial infection in the body would be avoided if people but used proper care in the treat- ment of wounds. We have seen that white corpuscles resemble amcoebe in their structure and activities (7). Let us now study their functions in the human body. When one gets a sliver of wood in one’s finger and leaves it there for a time, the finger becomes more or less swollen and sore, Hs and white * matter” or pus £9529) usually forms in the region of the wound. These effects are principally due fo the activity *75 2" core devouring a bas- of bacteria, which were car- errr Ras corpuscle destroyed by bac- ried into the wound on the piece of wood. Finding in the tissues all the favorable conditions for growth, these minute organisms multiply rapidly and produce poisons called toxins, that cause the inflammation. As soon however, as these inflammatory processes begin, large numbers of white corpuscles are hurried to the spot and proceed to attack the invading bacteria. If the number of germs.is relatively small, and if the corpuscles are in a healthy condition, these cells of the blood seize upon and devour the bacteria (Fig. 12) in the same way that an amoeba takes in its food. Under these conditions ‘little if any a Fig. 12.— White corpuscles. 30 HUMAN BIOLOGY pus is formed. But if the bacteria get the upper hand in the struggle, many of the corpuscles are killed, and it is the dead white cor- puscles that form the pus. In case of a cut the wound should be cleansed as quickly as pos- sible with peroxid of hydrogen or some other germ- destroying solu- tion, and should then be covered with absorbent cotton soaked in the peroxid solution and bandaged, to prevent the en- trance of other germs. If this is not done, bacteria are Fic. 13.— Dr. Robert Koch, German bacteriologist. || : Born 1843. Died 1910. likely to settle in (From International Encyclopedia. Courtesy of Dodd, the wound, and Mee e009? healing may be delayed or even more serious results may follow. With proper treatment a wound should show no signs of inflam- mation, or formation of pus, and should heal rapidly. 26. The cause of tuberculosis. —It is said that one seventh of all the deaths in the world are due to the disease MICROORGANISMS AND HUMAN WELFARE 81 tuberculosis, which is more commonly known as consump- tion. In New York City alone the Board of Health reports 300 to 400 new cases every week. Yet if the general public only knew the manner in which this disease is transmitted and would make use of this knowledge, the dreadful sacrifice of life and health due to this ‘‘ great white plague ”’ could be almost wholly prevented. It was conclusively proved in 1882 by Dr. Koch, a noted German scientist (Fig. 13) that tuberculosis is always caused by extremely small, rod-shaped bacteria, bacillus tuberculosis (Fig. 14). He found countless numbers of these living germs in the sputum coughed up by consumptive patients ; he cultivated these germs in test tubes and when he injected the bacteria into the bodies of guinea pigs or rabbits, the animals be- came ill with tuberculosis. By many experiments of this sort, biologists have learned important facts in regard to the cause, preven- tion, and cure of disease. Fic. 14. — Tuberculosis bacteria in human We are absolutely sure sputum. (Courtesy of Dr. Thomas 8. then, that before any one 9 ©@™neton.) can become a consumptive, he must take into his body the living bacteria of consumption, and the most common avenue of infection is through the nose and air passages. Consump- tives who are ignorant of the danger they are causing, fre- quently expectorate on the floors of rooms or of public con- veyances, and when this sputum becomes dried, the germs are likely to be blown about in the air, and to be inhaled by 382 HUMAN BIOLOGY other people. When the bacteria get; into the lungs of a per- son who happens to be a little ‘run down,” as we say, straightway the bacteria begin to multiply, feeding meanwhile on the lung tissues; for this reason the disease is called con- sumption, and if it is not arrested, the lungs may be almost destroyed, and death, of course, results. During the progress of the disease, little masses or tubercles of lung tissue (whence the name tuberculosis) are thrown off by the patient in coughing, and these, as we have already stated, are swarm- ing with living bacteria. 27. The prevention of tuberculosis. —It is of the ut- most importance, therefore, that these living germs ‘be kept out of the bodies of people who come in contact with con- sumptives. Responsibility in this matter rests very largely upon the patients themselves, and if they exercise the neces- sary care, they need not become a menace to healthy people in the home or in the community. It is of course essential that every effort be made to stop altogether the dirty and dan- gerous habit of spitting. Many people have the disease long before they are aware of it, and a general public sentiment should be developed that will actively assist boards of health in enforcing their rules against the ‘ spitting nuisance.” Every consumptive should provide himself with paper cups or cloths that may be burned, together with their contents. Tuberculous patients should exercise care not to cough or sneeze without covering the mouth or nose with a hand- kerchief, for it has been proved that living germs are widely distributed by carelessness in this regard. Separate knives, forks, spoons, and drinking vessels, which ought to be cleaned in boiling water, should be set apart for consumptives. Kiss- ing the lips of consumptives should never be permitted. 28. The cure of tuberculosis.— In former years the decision by doctors that a patient had tuberculosis was be- MICROORGANISMS AND HUMAN WELFARE 33 ‘lieved to be a sentence to a lingering death; it was believed also that the disease was hereditary. Happily modern medicine has dispelled both these beliefs. A child may inherit weak lungs or a frail body; but it will never be a A. Tent open. B. Tent closed. Fig. 15.— Window tent. (Courtesy of Dr. Thomas 8. Carrington.) consumptive unless the bacteria that cause this disease are in some way planted in his tissues. Consumption, too, is a curable disease, unless it is neglected until it has reached an advanced stage. The prime requisites in the treatment of the disease are a plentiful supply of fresh air, plenty of easily D 84 HUMAN BIOLOGY digested and nutritious food, like eggs and milk, sleep and freedom from hard muscular work and from worry. ‘These conditions may be obtained even in crowded cities, for. by the use of tents on the roof, or of window tents (Fig. 15) a suffi- cient amount of air may be secured, and almost marvelous cures are found to result.! 29. The cause and treatment of pneumonia. — Another disease that affects the lungs is pneumonia. It is more prevalent in the spring and autumn of the year, and is commonly a disease of adults. The cause of pneumonia is a spherical form of bacteria, which get into the lung tissue and grow there when the individual is physically weak or mentally depressed. Formerly, in treating the disease, patients were kept in closed rooms, carefully shielded from all draughts of air. It has been found, however, as is the case with tuberculosis, that fresh outdoor air is one of the best means of treating the patient. To combat both tuber- culosis and pneumonia, our bodies and minds should be kept in such a healthy and vigorous condition that invading dis- ease germs will always meet with a hostile reception whenever they attempt to prey upon our organs and tissues. 30. Cause of diphtheria. — Another disease that formerly claimed many victims among young children is diphtheria. The germs of this disease are rod-shaped ‘organisms some- what larger than those that cause tuberculosis. When these bacteria find lodgment and grow in the throat, they produce a membrane and form poisonous substances known as toxins, which are absorbed and carried by the blood to other parts of the body, often causing paralysis and other injurious effects. 1 The authors are much indebted to Dr. Thomas Spees Carrington for suggestions relating to tuberculosis. For additional suggestions see Dr. Carrington’s ‘“‘ Fresh Air and How to Use It’ ($1), National Association for the Study and Prevention of Tuberculosis, 105 E. 22d St., New York City. MICROORGANISMS AND HUMAN WELFARE 35 31. Treatment of diphtheria. — But these germs do not have things all their own way. The cells of the body seem to know when an army of this enemy has entered their terri- tory, and they at once set to work to produce substances that will neutralize or overcome the toxins formed by the diphtheria bacteria; these substances are known as anti- toxins. When the disease is at its height, there is a fierce battle between the invading microbes with their toxins and the cells of the body fighting for their lives by means of their antitoxins. If the bacteria are victorious, death ensues. In the year 1892 a most important discovery was made by a German bacteriologist named Von Behring. He found that it is not necessary for the human body to manufacture _all the antitoxin it needs for its struggle with the diphtheria poisons, but that this substance may be taken from the blood of other animals that have produced it. For this purpose, healthy horses are now secured by city boards of health, and a small dose of diphtheria toxin is injected into their bodies; the next day a larger dose may be given with little or no ill effects; until, at the end of several months of this treatment, the animals can stand a quantity of the poison that would have proved fatal if given at an earlier time. For during all these days the horse has been having a very mild form of diphtheria, and the cells of his body have been producing and giving into the blood an amount of antitoxin much more than is needed to neutralize the diphtheria poisons the ani- mal has received. Some of the blood is then carefully re- moved and allowed to clot. The liquid serum that oozes out of the clot contains the antitoxin, which is carefully prepared for injection into the body of human beings when ‘diphtheria attacks them. And so our good friend the horse, without any permanent ill-effects to himself, has decreased the death rate formerly caused by diphtheria by 75 to 80 per cent. 36 HUMAN BIOLOGY 32. Prevention of diphtheria. — We have learned some- thing of the means by which we can combat this disease when once it has begun its attack. Antitoxin may also be administered to any members of the family who have been exposed to diphtheria, and it then becomes a means of pre- venting the disease. But it is much more important, as is the case with tuberculosis, to prevent all danger from attacks by this disease than it is to know how to cure it. Here again we find strong arguments for the enforce- ae ment of the rules against spitting, for liv- ing bacteria are often found in the throats of sufferers from what are thought to be : ordinary sore throats. For this reason, Fis: OT too, children should be especially careful ; to avoid putting into their mouths pencils, coins, candies, or other objects that have been used by other pupils, for diphtheria germs have been frequently transmitted in this manner. 33. Cause of typhoid fever. — Typhoid fever is a disease caused by the growth in the tissues of the intestines of rod- shaped bacteria. The typhoid bacteria have several hair- like projections something like long cilia (known as flagella), which vibrate rapidly and so enable the germs to move about (Fig. 16). These bacteria are practically always taken into the body through the mouth and thence into the intestines. “ Food and drink are usually the vehicles which serve for the entrance of the bacillus, water and milk being probably the most frequent sources of infection. The latter is es- pecially dangerous from the fact that the typhoid bacillus not only lives but multiplies in it. Water and milk, however, are only dangerous when they actually contain the typhoid bacilli which have entered into them from the excretions of MICROORGANISMS AND HUMAN WELFARE 387 typhoid patients or those who have become typhoid car- riers.”! It has been proved over and over again that the common house fly is frequently the means by which typhoid fever is transmitted (A. B., 43), since these insects often alight on the excretions of typhoid patients, and then carry the germs on their hairy feet (A. B., Fig. 40), and so infect the foods on which they alight. 34. Prevention of typhoid fever. —It is evident, then, that if the excretions from the intestines and kidneys of typhoid patients were thoroughly disinfected by carbolic acid or other germicides, the spread of typhoid fever would be very largely prevented. It must be borne in mind, however, that the bacteria of this disease continue to live in great numbers and to multiply in the intestines of some people who have had typhoid fever years after recovery from the disease, and these people are the so-called “ typhoid carriers.”’ ? One of the most difficult problems that formerly confronted armies was that of preventing typhoid infection. In the Mexican War and in the Civil War the armies on both sides paid frightful toll to this dread disease, and even in the Cuban War, five thousand men in the United States Army died of typhoid fever or other fly-borne dis- eases, while only three hundred were killed by Spanish bullets. Sanitary camps, however, have greatly improved the situation, and in recent years an anti-typhoid vaccine, somewhat like that used in the prevention of smallpox, is injected as a means of prevention, and the results of the use of this vaccine have been most favorable. The improvement in army health is strikingly shown by comparing figures for two army divisions of about the same size, one at Jack- sonville, Florida, during the Spanish-American War in 1898, the 1 Quoted from article on typhoid fever, in New International En- eyclopedia, copyrighted 1903 by Dodd, Mead, and Co. 2 See footnote, p. 39. 388 HUMAN BIOLOGY other at San Antonio, Texas, during the 1911 maneuvers on the Mexican border. JACKSONVILLE | SAN ANTONIO 1898 1911 Number of soldiers. . . ; 10,759 12,801 Number cases typhoid (Gertain and probable) . . . . : 2,693 1 Number of deaths from typhoid fever 248 0 Number of deaths from all diseases. 281 11 v 35. Water supplies. —In country districts each house usually has its own well, and so the family becomes account- able for its own water supply. In this case great care should be taken to place the well in such a position that none of the drainage from the house or barn can soak through the soil into the well-water. Those who live in large towns and cities almost always obtain their water supply from a common source. This sometimes becomes contaminated by typhoid and other germs, and a disease epidemic then follows. Hence, if there is any doubt as to the purity of a water supply, boards of health should notify the house- holders, and the water, when used for drinking purposes, should then be boiled and kept in bottles on ice until used. 36. Milk supplies. — Many families in rural communities keep their own cows, and so they can be sure of clean milk if they only take the necessary trouble. Cows, like human beings, need plenty of light, air, wholesome food, and clean surroundings. If any of these are wanting, the animals are likely to become diseased, and the milk is then affected. Great care should be taken also at milking time to see that MICROORGANISMS AND HUMAN WELFARE 39 the surface of the body of the cow, especially about the flanks and udder, are brushed and wiped with a moist cloth, and that the hands and clothing of those who milk are kept clean; otherwise enormous numbers of microbes will fall into the milk. No one who has any infectious disease should be allowed to have anything to do with the care of cows or of milk until he has completely recovered. Over and over again epidemics of diphtheria, scarlet fever, typhoid,’ and tuberculosis in infants have been traced along the routes of careless milkmen. Those who live in cities, however, are wholly dependent for milk upon sources they know nothing about. The milk that is consumed in New York City, for instance, comes from over 40,000 dairies scattered through six different states. It is, of course, impossible to make any proper inspection in such a wide field. The New York Board of Health is doing all it can in this respect, and so far as possible it prevents dirty and dangerous milk from coming to the city. The only path of safety, however, lies in the careful Pasteuriza- tion of milk and cream that are used for drinking purposes, especially by young children. In communities where Pas- teurization has been tried at all generally, there has been a surprising decrease in the percentage of sickness and death from intestinal diseases, especially in the summer time and among young children. The instruction given by boards of health to mothers and to older children as to the care of the young during the hot months has also helped to save the lives of a large number of infants. 1A sudden increase in the number of cases of typhoid fever in New York City in 1909 was found to be entirely due to milk fur- nished by a dairyman in a town in New York State. He had re- covered from typhoid fever in 1864, but still carried infection in his body and passed an enormous number of the germs of the dis- ease.: 40 HUMAN BIOLOGY 87. Smallpox and vaccination.— Smallpox was once so common that scarcely one person in a hundred escaped it. It was intro- duced into America by the Spaniards, it destroyed 3,500,000 people in Mexico, and spread with frightful rapidity throughout the New World, until in 1733 it nearly de- populated Green- land. Mankind is indebted to Dr. Edward Jenner (Fig. 17), an Eng- lish physician, who in 1796 proved that vaccination is a sure method of preventing the dis- ease. In vaccina- tion our bodies re- ceive germs that originally came from smallpox, but which have been so modified that they cause a mild form of disease very different from Fig. 17.—Dr. Edward Jenner, English physician. smallpox itself. Born 1749. Died 1823. The cells produce (From International Enclyclopedia. Courtesy of Dodd, some form of anti- Mead & Co.). toxin which is ef- fective protection when we are exposed to the disease. This kind of protection does not last indefinitely, however, and every person should make sure that successful vaccination is performed at least once in ten years, and oftener than that if cases of smallpox develop in the community in which he is living. If a person has been act- ually exposed to the disease, he should be vaccinated immediately. MICROORGANISMS AND HUMAN WELFARE 41 Since the introduction of compulsory vaccination, smallpox is be- coming very rare. - 38. Hydrophobia and the Pasteur treatment. — Hydrophobia, or rabies, is a disease due to the bite of a mad dog, cat, or wolf. Until the latter part of the nineteenth century the only known method of treating this disease was that of burning out or cauterizing the wounds with hot irons or nitric acid. After a long series of investi- gations, however, Louis Pasteur (Frontispiece), a French scientist, made known to the world the so-called Pasteur treatment (1885). Pasteur found that the disease was located in the spinal cord, and that, if pieces of the spinal cord of a rabbit which had died of hy- drophobia are allowed to dry in the air, the germs gradually lost their virulence. He therefore began the treatment of patients who had been bitten by mad dogs by first injecting beneath the skin an emulsion made from the spinal cords which had been dried for four- teen days. Each day for twenty-one days an injection was made from a cord that had been dried for a shorter time. Since hydro- phobia. usually does not develop in human beings for two weeks to four months after the bite of a mad dog, the cells of the body by this Pasteur treatment gradually acquire the power to resist the hydrophobia toxins, and so the disease is prevented, if the wound is cauterized at once and treatment begun immediately. The cau- terization is of value even after a delay of twenty-four hours.! 39. The cause and prevention of other diseases. — The germs that cause scarlet fever, yellow fever, measles, whoop- ing cough, and infantile paralysis have not as yet been dis- covered. Since, however, they are all infectious diseases like tuberculosis and diphtheria, they must be due to some form of microbe. Those in yellow fever, measles, and infantile paralysis are so small that they pass through stone filters. 1 The authors are much indebted to Dr. W. H. Park, Director of the Laboratory of the Board of Health of New York City, for his suggestive criticism of the sections relating to disease-producing bac- teria. 42 HUMAN BIOLOGY These cells are therefore too small to be seen by the most powerful microscopes. The life history and method of transmission of the micro- scopic animal that causes malaria has already been dis- cussed in connection with the study of the Anopheles mosquito (A. B., 40). Likewise, it has been demonstrated beyond a cavil that infectionfrom a yellow-fever patient can only be brought about through the agency of the Stegomyia mosquito. Hence, to eradicate these diseases entirely, we need only to exterminate all Anopheles and Stegomyia mos- quitoes. Sleeping sickness is a dread disease of the tropics which is due to a kind of Protozoan something like a paramecium. iS saline “6 ASS z qs 40. Safeguards of the body against disease. — In the first place, the tough outer skin, as long as it is unbroken, forms a most effective ee se een er omer barrier to the entrance of bacteria, secretion except at the mouth and nose Fic. iri os cells from openings. Each of the nostrils is ee guarded by hairs that collect a large number of dirt particles. On the.mucous membrane lining the nose and throat still other bacteria are caught, and the cells which line the windpipe are furnished with cilia, which lash upward (Fig. 18) and tend to expel the germs that may have gone past the outer lines of defense that we have named. If the bacteria enter the stomach and intestines-in a living condition, many of them are digested with the food. And even though the invading microbes finally reach the interior of the cells of our lungs, or muscles, or brain, we can still rely upon the antitoxins which the cells of a healthy human F MICROORGANISMS AND HUMAN WELFARE 43 body are ever ready to produce. In the case of many of the contagious diseases, like scarlet fever or smallpox, these antitoxins remain for a considerable time in the blood to make us immune against a second attack. The white cor- puscles, too, are a sort of cavalry, troop, ready to pounce upon the bacteria and either devour them or carry them off from the body (Fig. 12, A). An optimistic view of life and free- dom from worry are undoubtedly very important factors in keeping the body in a state of vigorous health. 41. Topics for biology composition.!— Optional Library Work. Consult the local health authorities, Allen’s ‘Civics and Health,” Bulletins of U. 8. Department of Agriculture, New Inter- national or other Encyclopedia, and other sources, and prepare in your notebook a composition on one or more of the following topics: — 1. The Work of the Board of Health. 2. The Work of the Tenement House Commission. 3. How a City May Be Kept Clean. 4. A Visit to a Model Dairy. 5. City Milk Inspection. 6. A Hygienic House. 7. Helpful Bacteria. 8. City Playgrounds and Parks: Their Use and Abuse. 9. How the Study of Bacteria Can Help Us in Our Homes. 10. Sleeping in the Open Air. 11. A Visit to Ellis Island: How the Commission Cares for Immigrants. 12. The Responsibility of the Individual for Fable Health. 13. An Ideal School Infirmary. 14. The Work of the Consumers’ League. 15. Methods of Sewage Disposal. 16. The City Water Supply. 1The authors are indebted to Miss Edith Read of the Morris High School for the following list of composition topics. CHAPTER III FOODS AND THEIR USES I. Foop SuBSTANCES FOUND IN THE Human Bopy 42. Composition of the body. — Many careful analyses have been made of the composition of the human body, and these analyses have shown that our bodies are made of the same kinds of materials as those found in plants; namely, proteins, fats, carbohydrates, mineral matters, and water. 43. Proteins. — The most important substances in the living body are the proteins. As we have already learned,} proteins are essential constituents of the protoplasm of every plant cell, and this is likewise true of the cells in animal and human bodies. 44. Fats and carbohydrates. — The amount of fat in the body varies greatly in different individuals, but it is always present in some quantity. Muscle, however lean, contains particles of fat; fat constitutes a small percentage of the blood ; it fills the spaces in the interior of bones; and it is often deposited in considerable quantity in the deeper layers of the skin. In the blood and in other animal tissues we find some of the carbohydrate called grape sugar. Another car- bohydrate known as animal starch, or glycogen, is found in the liver and in the muscles. 45. Mineral matters. — Mineral matters are found in the greatest quantities in the bones and the teeth. When 143, ‘‘ Plant Biology.” 44 FOODS AND THEIR USES 45 we burn bones, about one third of the weight disappears, the remaining two thirds being bone ash, which is the mineral matter. Every part of the body, however, contains some mineral ingredients; for when muscle, liver, brain, or blood is burned, there remain some traces of ash in each case. 46. Water. — The great importance of water in the com- position of the human body is evident from the fact that this compound forms about 62 per cent of the weight of an adult. Hence, if all the water were removed from the body of a man -weighing one hundred and fifty pounds, the solids that re- mained would weigh less than sixty pounds. The different organs vary greatly in their percentages of water; bones contain about 22 per cent, muscles have 75 per cent, and the kidneys 82 per cent. II. Tue Necessity ror Foops 47. Necessity of foods for growth. — During the earlier years of life, as we all know, the human body rapidly increases in weight. A child at birth usually weighs seven to eight pounds, whereas the weight of a fully grown man is often one hundred and fifty pounds or more. Hence during a lifetime there is often a twentyfold increase in weight. To provide for this increase or growth a large amount of new material must of course be taken in by the human being, and this material is supplied by the food. 48. Necessity of foods for repair and for the production of energy. — On the other hand, it is not difficult to prove that throughout life the body tends constantly to decrease in weight. For instance, if one were weighed on accurate scales immediately after eating and then again after several hours had elapsed and before food or drink had been taken, a decrease in weight would be noted.. Still more striking is 46 HUMAN BIOLOGY the loss of weight due to abstaining from food because of illness or other reasons. It has been found too that when one is engaged in very active exercise, such as playing tennis or football, the loss of weight is greater than when one remains quiet. How, then, can we account for the loss of weight in all the cases that we have been enumerating? We all know that during violent activity considerable quantities of perspiration are given off from the skin, and this has been proved to be true at all other times, though to a less extent. It has also been demon- strated that many waste materials are given off from the lungs, the organs of digestion, and the kidneys. We have now accounted for the constant loss of weight in our bodies, but we have still to ask ourselves how these waste substances are produced in the body. The two commonest wastes of the body are carbon dioxid and water. These are produced by the oxidation of the carbon (P. B., 80) and the hydrogen in the foods. This has also been proved to be true in animals and in the human body. 49. Definition of a food.— The three most important uses of foods have been suggested in the preceding sections. Hence we may say that a food is any substance that yields material for the repair or growth of the body, or that supplies the fuel used by the body for producing heat, or power to do work. It should be understood, however, that no substance should be regarded as a food if it injures the body while supplying materials for growth, repair, or the production of energy. III. Tue Composition or Foops 50. Todetermine the food substances present in milk. — Laboratory demonstration. 1. Shake a bottle containing milk and cream and pour a FOODS AND THEIR USES 47 small amount into a test tube; add a little strong nitric acid, and boil. a. Describe what was done. : b. What change in the color of the milk do you observe? c. What food substance do you therefore conclude to be present in milk? 2. Place a drop of the “‘ mixed milk,’ used in 1 above, on paper, and allow the paper to dry over a warm radiator. Hold the paper to the light. What kind of food substance is present in considerable quantity in the milk? How do you know? 3. Add a few drops of iodine to some milk. What is the result, and what is your conclusion? 4. Test another sample of milk with Fehling’s solution. State the result and your conclusion from the ex- periment. The sugar found in milk is known as milk sugar, and when it is heated with Fehling’s solution, it is changed to grape sugar. 5. Heat a half spoonful of milk, and hold over it a clean, dry tumbler. What nutrient does this experiment prove to be present? Why? 6. (Optional.) Evaporate to dryness the spoonful of milk, and then burn the solid residue over a very hot flame. Does all the solid disappear, or is something left on the spoon? What is your conclusion as to the presence or absence of mineral matter in milk ? I . As a conclusion from all your experiments, state what food substances or nutrients! are present in milk, and what food substances are absent. 51. The composition of other foods. — Our study of milk has shown us that this food is composed of the same 1 In our study of plant biology we called the compounds named in this paragraph food substances rather than nutrients, for botanists regard the simpler compounds (carbon dioxid, water, and mineral matters) that plants obtain from the water and air as the nutrients of the plants. By some writers water is not regarded as a nutrient ; since, however, it is an essential constituent of protoplasm, it may well be named among the nutrients. 48 HUMAN BIOLOGY EGG WHITE AND YOLK BEEF STEAK T7HOLE MILK Fic. 19.— Composition of common animal foods. (Drawn from Charts of U.S. Dept. of Agriculture by Mabelle Baker.) ‘ FOODS AND THEIR USES 49 STRING BEAN .GREEN. PARSNIP = ug 9 Ash:0.6- = Carbohydrates: 7.4 im WHITE BREAD ters 35.3 (fill meni rbo- {rates DO+ Ash: 0.3" Carbohydrates: 14.2 — POTATO Carbohydrates: 18.4 Water: 76.3 . 20.— Composition of common vegetable foods. (Drawn from Charts of U.S. Dept. of Agriculture by Mabelle Baker.) EB 50 HUMAN BIOLOGY kind of food substances that we found in plants; and this is what we might expect, since the cow is wholly’dependent upon grass and other vegetable foods. Indeed, when we analyze any other animal foods that we eat, we find that all consist of one or more of the food substances which closely re- semble those that we have been studying in plant biology. In Figures 19 and 20 are represented not only the various nu- trients found in some of our most common fcods, but also their relative proportions in percentages. 52. Composition of various foods. — (Home study.) 1. Name the foods represented in Figures 19 and 20 that are derived from animals; name those obtained from plants. Which of the two classes of foods, named in 1 above, has on the average the larger percentage of protein? In which of these two classes do you find the larger amount of fats? Which class has the larger percentage of carbohydrates? What, then, are the principal differences in the composi- tion of animal and vegetable foods? Name the various food substances found in one animal food and in one vegetable food, giving in each case the percentage of each nutrient. Oo: Siar. coe IV. Usrs or tHE Foop SuBSTANCES 53. Uses of the food substances to plants and animals. — In our study of green plants we learned that these living organisms can manufacture the food substances they need from the simple compounds (water, carbon dioxid, and mineral matters) found in earth, air, and water, and that these food substances are used for the making of protoplasm and the liberation of energy. Animals and human beings, on the other hand, since they cannot make their foods, are FOODS AND THEIR USES 51 either directly or indirectly dependent on plants for their food supply. They use these food materials, however, for the same purposes as do plants. The use of the individual food substances will now be considered. 54. Uses of proteins. — Protein is an essential constit- uent of plant protoplasm (P. B., 48). This class of nutrients is also essential for the growth and repair of the living sub- stance in muscle, nerve, and all other tissues of the human body. Proteins may also be oxidized in the body and give heat and muscular. energy. 55. Uses of fats and carbohydrates. — The chief fuel in- gredients of food, however, are the fats and carbohydrates. Most of the fat in our foods is probably oxidized soon after it reaches the cells to furnish heat and power, and this class of nutrients possesses two and a half times the fuel value of any other kind of food substance. This is the reason why the inhabitants of arctic countries eat such large quantities of fatty foods. The starches and sugars of bread, potato, fruits, and milk are also used as fuel. The fat which we stated (44) is stored in various parts of the body, is derived partly from the carbohydrates and partly from the fats in our food, and this acts as areserve fuel. That portion of the fat which is stored in the deeper layers of the skin helps to keep our bodies warm by preventing the escape of heat. 56. Comparison of uses of the nutrients. — It is evident that the three nutrients thus far studied may be used to supply the body with energy. If our diet is deficient in any one of the three, the others supply the need, and are burned instead. For growth and repair, however, proteins are absolutely essential; neither carbohydrates nor fat can be transformed 52 HUMAN BIOLOGY into this essential ingredient of protoplasm. Hence, an animal soon dies if it is not supplied with proteins. If a machine is to do a large amount of work, it must be large enough and strong enough, and must have plenty of fuel. This is true of the body machine. A man who does hard work, and a good deal of it; needs plenty of proteins in his food to build up his tissues and keep them in repair, and plenty of fats and carbohydrates for fuel. 57. Uses of mineral matters and water.— The mineral matters like phosphate and carbonate of calcium and magne- sium are necessary for making bones and teeth, and for the making of protoplasm (P. B., 43). Salt is used in large quantities by all civilized nations; it makes food more palatable and it is important in the making of digestive fluids. Water is an essential constituent of protoplasm, and hence the body needs it constantly. Water also aids in dissolving foods. A considerable amount is supplied by the water contained in some of our solid foods, and we get the rest from the water and other beverages that we drink. V. Cooxine or Foops 58. Importance of proper cooking. — Some of our foods, like milk, nuts, and fruits, are eaten without being cooked. The great majority, however, before they are taken into our bodies are changed considerably. It is important for us to learn the essential prin- ciples of good cooking, since food, as often prepared, loses much of its flavor, becomes more or less indigestible, and is deprived of a considerable percentage of its nutrition. 59. Reasons for cooking animal foods. —In civilized com- munities meats and other animal foods are usually cooked by broil- ing, roasting, boiling, or frying. The reasons for cooking the flesh FOODS AND THEIR USES 53 of animals are these: (1) proper cooking loosens and softens the fibers, thus preparing the meat for mastication and for the action of the digestive juices; (2) the heat kills the harmful bacteria and other parasites (e.g. tapeworms) that are sometimes found in foods of animal origin; (8) cooking makes the meat more attractive in appearance and often improves its flavor; and (4) cooked meat is more completely digested. It is probably true, however, that raw or partly cooked meats are more ¢asily digested. 60. Frying. —If meats are fried, the skillet should be very hot, so that the surface of the meat may be coagulated at once, thus preventing the escape of nutrients and the entrance of fats. Frying usually involves the use of additional fats, and since frying tends to make foods indigestible, this is doubtless the poorest method of cooking meat. 61. Soups. —If we wish to obtain nutritious soups, the meat should be cut into rather small pieces and first put into cold water to which a little salt has been added. A small proportion of the proteins, and large amounts of so-called ‘‘extractives,” or flavoring matters, are drawn out by the water and salt, and since the meat is in small pieces, a considerable proportion of the mineral matter is thus dissolved. When we warm the mixture, we cause the fats to melt, and when it is boiled, much of the tough connective tissue is made more or less soluble by being turned into gelatin. The soups thus obtained are made more palatable by the addition of condi- ments. The meat which is left after the soup has been prepared is more or less tasteless. Only small percentages, however, of the nutrients have been withdrawn; hence the soup meat should not be thrown away, but should be used as described in 71. 62. Stewing. — It is unfortunate that stews are not more highly regarded in American families, for by this method of preparing animal foods all the nutritive ingredients are utilized. Tomakeagood stew the meat should be cut into rather small pieces and placed in cold water. Some of the flavoring matters and soluble proteins 54 HUMAN BIOLOGY pass out into the broth, making it rich and nutritious. When the stew is allowed to simmer for several hours on the back of the stove, the meat itself becomes tender and readily digestible. The addi- tion of vegetables makes it a most nourishing and palatable dish. 63. Boiling meats. — When the meat itself is to be eaten, and the broth is not to be used, the whole piece should be plunged intc boiling water for a few moments. In this way the protein on the surface is quickly coagulated, and the crust thus formed prevents the loss of the meat juices. The temperature of the water should then be reduced somewhat below the boiling point by pushing the kettle toward the back of the stove, and the meat should then cook slowly until it is done. A piece of meat, when cooked in this way, is tender and juicy throughout. If, however, the water is kept at the boiling point (212° F.), the meat may be easily torn apart, but the fibers are found to be hard and stringy. 64. Roasting and broiling. — The best method of cooking the flesh of animals, if the broth is not desired, is by roasting or by broil- ing, since smaller percentages of the nutrients are lost than is the case in boiling. The outer layer of protein must, however, be coagu- lated at once, and for this purpose a very hot fire is needed. When the piece to be roasted is small, the high temperature should be maintained until the meat is cooked. A large roast,'on the other hand, after the outer covering has been coagulated, requires a slower fire and a longer time; meat is not a good conductor of heat, and a hot oven would scorch the outside before the central mass could become thoroughly cooked. A better crust is formed on the outer surface of the roast if the meat juices in the pan (mostly fat) are frequently poured over the surface of the roast. This is called “basting.” : 65. Reasons for cooking vegetables. — The starches, which are present in large quantity in foods of vegetable origin, are usually inclosed in cells, the walls of which are formed of indigestible cellu- lose. Hence, before starch can be digested, it must be freed from this cellulose envelope. This is largely accomplished by cooking, FOODS AND THEIR USES 55 which causes the starch grains to swell. The cell walls are broken open in this way, and when the grains burst, a larger surface is ex- posed to the action of the digestive juices (Figure 21). This is strikingly shown in popping corn. The crust of bread is more easily digested than the softer parts, and toasting bread increases its di- gestibility, because this browned starch (sometimes called soluble starch) requires less change before it can be used by the body. 66. Boiling vegetables. — Experiments have shown that a good deal of nutriment is lost by boiling vegetables in water. Much of Fic. 21.— A, cells of raw potato with starch grains inclosed in the cellulose walls. B, cells of a potato well steamed and mashed; starch grains have been burst by the heat. this waste may be avoided, however, if one heeds the following directions: (1) vegetables should be cooked as far as possible in their peels, for these outside coverings keep the sugar, proteins, and min- eral matters from being drawn out by the water; (2) if the vege- tables must be peeled and cut up, the pieces should be relatively large, as a smaller surface is thus exposed to the water; (3) the amount of water should be as small as possible, and the vegetables should be cooked rapidly, in order to give less time for the solvent action to take place. 67. Bread making. — When bread is made, water (or milk), butter, salt, sugar, and yeast are added to flour. After the mixture has been stirred together, a sticky mass of dough is formed, which, in 56 HUMAN BIOLOGY a warm place, begins to rise. This is due to the fact that the yeast cells change the sugar into alcohol and carbon dioxid. Bubbles of gas are thus imprisoned in the sticky dough. While expanding and seeking to escape, the gas makes the solid mass porous. After the bread has risen sufficiently, it is kneaded in order to break up the large bubbles and in order to distribute the gas throughout the dough. When the bread is baked, the alcohol and carbon dioxid pass off into the air, leaving the bread light and digestible. VI. Foop Economy 68. Importance of food economy. —It is said that in a large proportion of American families more than half the total income is spent for food, and that the remainder of the income must serve for rent, fuel, clothing, doctor’s bills, and other expenses. Hence, any saving that can be made in the annual food bill of a family should result in a surplus which may well serve as a nucleus of a saving’s bank account, or may be used in improving the home surroundings or in se- curing wider means of education and enjoyment. The average American, however, is far from economical in the matter of foods. In the first place there is often extravagance in the purchase of food, and in the second place foods are fre- quently wasted in the home. 69. Comparative cost of foods.— (Home study.) The chart shown in Figure 22 exhibits (1) the cost price of each of the foods represented, (2) the weight. of the food that may be purchased for 25 cents, and (8) the weight of the solid food substances (except mineral matters) that may be purchased in each food for 25 cents. Note at the top of the chart the short vertical lines that indicate 1 pound, 2 pounds, .etc., of solid nutrients; hence, if 25 cents is spent for wheat flour, about 7 of a pound of protein can be secured, } of a pound . . of fat, and about 63 pounds of carbohydrates. FOODS AND THEIR USES 57 PROTEIN FATS CARBOHYDRATES THE HEAVY BLACK LINES IN THE CHART BE~ I WH’, LOW INDICATE THE RELATIVE FUEL VALUE WU IN ONE POUND OF EACH OF THE NUTRIENTS : s\bee ws = ra WEIGHTS OF NUTRIENTS AND FUEL VALUE SR \= ot Bo - zo IN 25 CENTS’ WORTH. a 2 cn lcts| vss. 1B. § LBs. BLFS BEEF, SIRLOIN 25.0} BEEF,ROUND 15.0) BEEF,NECK 6.0 MUTTON, LEG 22.0) HAM,SMOKED 16.0) SALT PORK, VERY FAT 12.0 8 CODFISH, FRESH 8.0 °° 3 CODFISH, SALT 7.0 24 z MACKEREL,SALT 12.0 < OYSTERS, 35 CTS. QUART /48.0) EGGS, 26 CENTS DOZEN 14.7] STANDARD FOR DAILY DIET FOR MAN AT MODERATE WORK AMERICAN MILK,7 CENTS QUART 8.6 CHEESE,WHOLE MILK 15.0] CHEESE,SKIM MILK 8.0 BUTTER 90.0) ( SUGAR 6.0 VL SM)14Qqoun—mzjqqjoz?z WHEAT FLOUR 8.0] 8. MMM WA 8 WHEAT CREAD 7.0) 8.57 w WK UL K CORN MEAL 2.6 MT i 5 BEANS 5.0] 5.00 POTATOES 1.2] 20.00 Fig. 22.— Economy in-the purchase of foods. Prices in this chart were those in the year 1900. Compare with Drices to-day. (U. 8. Department of Agriculture.) a 58 10. HUMAN BIOLOGY ' Name the foods represented in Figure 22 that are derived from animals; name those obtained from plants. On the average, can larger amounts of the animal or of the vegetable foods represented on the chart be pur- chased for 25 cents? Bearing in mind the relative work and expense in pro- ducing animal and vegetable foods suggest some explanations for the answer you have given to ques- tion 2. Which one of the foods on the chart would you buy if you wished to get the largest amount of solid nutri- tion for 25 cents; that is, which food is the most economical ? From which kind of food would you get the smallest amount of solid nutrients? Name other foods on the chart which are more expensive per pound than the one that you have just named. Which of the three kinds of beef named on the chart would be the most economical for soup or stew? Name three classes of food substances needed in the diet of the average American engaged in moderate work (see last line on the chart), and estimate the weight of each that is needed during a day. Which food on the chart comes the nearest to supplying in the right proportions all the nutrients named in 7? In the food you have named which kind of food sub- stance is not present in sufficient proportion? Why is it better to eat a variety of foods rather than any one kind? Suggest a reason why meat and potato should be eaten together; bread and butter. 70. Economy in the purchase of foods. — The animal foods, we have just learned, are considerably more expensive than the staple foods of vegetable origin. Hence, in an economical household the proteins needed by the body should be largely obtained from vegetable foods like bread, corn meal, and beans. If this plan were followed, a con- FOODS AND THEIR USES 59 siderable saving in the year’s expenses might be effected. Figure 22 shows the weights of different food materials that may be purchased for 25 cents. On comparing the two meats at the top of the chart, one can see that a greater fraction of a pound of solid nutriment may be obtained by spending 25 cents for round steak than could be secured by the purchase of sirloin. Yet the latter is bought even in very poor families. From oysters one gets less of the solid nutrients than fromi any other food represented on the chart; therefore, if one’s income is small, this kind of food should be regarded as a luxury, seldom purchased except in case of sickness. 71. Economy in the use of foods. —In discussing the cooking of foods, we suggested some of the ways by which the loss of nutritive ingredients may be prevented. We waste foods, however, in other ways; for instance, we often throw away bones and gristle, regardless of the fact that they con- tain a considerable percentage of protein, gelatin, and fat from which one might make a nutritious soup. It has been found that large proportions of the food materials still remain in a piece of meat after it has been used for soup, even though it is more or less tasteless. This meat should not be thrown away, however, but should be chopped up and combined with vegetables and condiments to make a hash. The garbage pails of most kitchens receive far too large a per- centage of the food that is bought for the household, and many a dollar could be saved for other purposes if more care were exercised to prevent this waste. The food problem, then, for the healthy human being is this — how to obtain the largest amount of good, nutritious food for the least money. To this problem an intelligent house- keeper, if she can be led to see the importance of the subject, 60 HUMAN BIOLOGY will devote considerable thought. This problem cannot be solved, as we have seen, by consulting market prices only, for often the highest-priced foods contain small per- centages of the nutrients. Neither can we be sure of a good supply of foods by following our tastes. To many people cakes and sweetmeats are more appetizing than sandwiches and cereals. Yet it is the latter that usually supply the available proteins, at a lower cost. The composition of various foods can be found only by chemical analysis, and their nutritive value can be deter- mined only by experiment. Fortunately these analyses and experiments are being carried on by the United States government. The results are published in the Bulletins! of the Department of Agriculture, Washington, D.C., many of which will be sent free to any address. VII. Dairy Diet 72. Amount of each nutrient required.— Many in- vestigations have been carried on, in this country and in Europe, to determine the amount of each kind of nutrient needed per day for the work of the body. The conclusions that were drawn from this study are represented on the last, line of Fig. 22. According to these conclusions the average American, when doing moderate work, requires about one fourth of a pound of proteins to provide for the growth and repair of the body, and a quarter of a pound of fat and a pound of carbohydrates to furnish the needed energy.2 This 1The most suggestive of these publications are ‘‘ Foods, and the Principles of Nutrition,’ ‘‘ Meats: Composition and Cook- ng “Milk as a Food”? ; “Fish as a Food’’; ‘‘Sugar as a ‘00: 2 Recently, however, at the Scientific School of Yale University, some very careful experiments have been performed by Professor Chittenden which seem to prove that this quarter of a pound of pro- FOODS AND THEIR USES 61 is about the amount eaten by a man of average appetite. In order to secure a heathful diet, the general principles stated in the following paragraphs should be borne in mind, by an adult or by a growing boy or girl. 73. Necessity for a mixed diet.— A sufficient variety of foods should be eaten at each meal to obtain all the nutrients needed. In 69 we learned that in none of the foods on the chart are the nutrients in the right proportions. Cow’s milk comes the nearest to being a perfect food, but its percentage of carbohydrates is too small. If we were to feed on meat alone, we should get too large an amount of proteins; while most of the vegetable foods are lacking in fats. Hence, a well-balanced diet should consist of a mixture of many kinds of foods. Such a diet will supply not only the proteins, fats, and carbohydrates, but also the mineral matters so necessary in the development of the bones and teeth, and in the making of living substance. In fact, some foods, such as spinach, are valuable chiefly on account of the mineral matters which they contain. If the appetite is normal, one is fairly sure to secure the nutrients in ap- proximately the right proportions.! tein for each day is considerably more than the body really needs. Dr. Chittenden experimented on five of the Yale University pro- fessors, on thirteen soldiers of the United States army, and on five of the best athletes at Yale; he found that all agreed that they could do better physical and mental work, and do it without any loss of weight, when they had become accustomed to taking less than half their ordinary amount of proteins. In several instances rheuma- tism, biliousness, and other derangements of the body were cured by this restricted diet. ‘‘There is no question, in view of our results,’’’ says Professor Chittenden, ‘“‘that people ordinarily consume much more protein food than there is any real physiological necessity for, and it is more than probable that this excess of food is in the long run detrimental to health, weakening rather than strengthening the body, and defeating the very objects aimed at.” 1 It,is desirable that pupils prepare a list of the kinds of foods and beverages, stating quantity of each, that formed their diet on the 62 HUMAN BIOLOGY 74. Avoidance of indigestible foods. — Frequently in- dividuals find that they cannot eat certain kinds of foods, e.g. cheese, honey, cucumbers, without discomfort. Hence, in selecting their diet these foods should not, of course, be eaten. Foods that are hard to digest, such as fried foods, heavy bread, or pastry, should be avoided, especially by growing girls and boys. 75. Sugars as a part of the diet. — Carbohydrates, we have found, are essential constituents of our foods. If, however, sugars are eaten between meals, too much of this kind of food substance is likely to be consumed, the appetite for other foods is lessened, and digestive disturbances are: likely to follow. Consequently the pastry and confectionery that are eaten should form a part of dessert. 76. Review of Foods Nereis Noes a Nee Protein Coagulates | Necessary for | Meat, eggs, (albumin, when the manu- milk, cheese nitrogenous| heated. facture of (among ani- food). Turned to protoplasm. | mal foods), yellow When oxidized} and beans, color by releases peas, oat- nitric energy. meal (among acid. vegetable foods). three meals of some stated day. These menus should then be read and discussed by teacher and pupils, and such suggestions for im- provement should be made as may seem necessary. FOODS AND THEIR USES 63 NAME OF TEST FOR UsEs oF Foops ContaINnING NUTRIENT NUTRIENT NutTRIENT NUTRIENT i Starch. Turned to a} Changed to | Vegetable blue color sugar, source] foods by iodine of energy, (especially solution. and may be! cereals). transformed ‘ into body fat. Sugar. Fehling’s Source of Vegetable solution is | energy. foods turned Transformed (especially orange or into body fruits) ; milk red when fat. sugar is boiled with found in grape milk. sugar. Fats (or Make trans- | Source of Animal foods oils). lucent energy. (especially spots on Transformed butter, pork, paper. into body cheese), Dissolved fat. vegetable by ether or foods, as benzine. nuts, cocoa, chocolate. Mineral Left as ash | Help to form | Common salt ; matters. after food bone, teeth, | mineral is burned. and other matters in tissues. most vege- Aid in table and digestion. animal foods. CHAPTER IV STIMULANTS AND NARCOTICS I. DEFINITIONS 77. Stimulants. — In the preceding chapter we discussed food substances, and these, we learned, yield material for the repair or growth of the body, or supply the fuel necessary for producing energy in the body. But in addition to the various nutrients that may be used for one or all of these purposes, we often take with our food certain substances that are not useful to any considerable extent in any of these ways. As examples of such substances, we may mention spices. Such substances add an agreeable flavor to our foods, and se stimulate our appetites ; hence, they are known as stimulants. A stimulant is any agent that temporarily quickens some process in the body. The most common stimu- lants are tea, coffee, and alcohol. 78. Narcotics.— Another class of substances that we sometimes use has an effect directly opposite to that of stimulants. Ether, morphine, and chloroform, for example, do not quicken any process in the body as do stimulants, but, on the contrary, lessen the degree of activity. Any compound that acts in this way is called a narcotic. A narcotic is any substance that directly induces sleep, blunts the senses, and in sufficient amounts produces complete in- sensibility. 64 STIMULANTS AND NARCOTICS 65 II. BEVERAGES 79. General effect of tea and coffee on the body. — The effect of tea and coffee on the body is due to the presence of essentially the same stimulant in both (caffein), which acts largely on the nervous system. In both tea and coffee, as they are usually prepared, is another substance known as tannin. This chemical, when obtained from the bark of certain trees, is used in tanning or hardening leather. When tannin is taken into the stomach, it is found to injure the mucous membrane and to retard digestion. 80. The preparation of tea and coffee. — To prepare tea properly, boiling water should be poured upon tea leaves, and the infusion allowed to stand only a few minutes before pouring. Tea should never be put on the stove to boil, for two reasons: in the first place, by this treatment the delicate taste and odor of the beverage are lost; and in the - second place, if the tea infusion is boiled, a considerable quantity of the tannin is dissolved by the water. Obviously the tea grounds should not be used a second time. Most that has been said in regard to tea applies equally well to coffee, except that in the preparation of coffee the in- fusion should be put on the stove and allowed to come to a boil ; it should then be poured out, and should not stand on the coffee grounds; otherwise the tannin will be extracted. Coffee is best prepared by the use of a percolator, since in this utensil the water is continuously forced over the ground coffee. 81. The use and abuse of tea and coffee. — ‘‘ When properly made, tea in moderation is a wholesome, agreeable, and refreshing stimulant beverage, particularly grateful in conditions of mental or physical weariness. Used in F 66 HUMAN BIOLOGY excess, it exerts a harmful influence upon the nervous sys- tem, and in a too strong form injures the digestive organs.” The foregoing remarks, quoted from Harrington’s ‘ Practi- cal Hygiene,” apply to adults rather than to growing chil- dren and youths; for in early life stimulants of every kind should be avoided as much as possible, as they tend to interfere with the healthful development of the body. We should remember that tea and coffee are not foods, and so cannot be of use in repair or growth of tissue, both of which functions are of prime importance during the first twenty years of life. The habitual use of these beverages, especially at breakfast, is also likely to decrease the desire for the food that is needed. 82. Chocolate, cocoa, and soda water. — While it is true that cocoa and chocolate both contain a considerable amount of nutriment when eaten in solid form, when prepared as a beverage, the small amount so used makes its food value relatively unimportant unless milk is used. Chocolate and cocoa contain a certain amount of a stimulant similar to that found in tea and coffee. Since the sirups and ice cream used in the preparation of soda water contain a considerable amount of sugar, these drinks should not be taken habit- ually between meals, because they tend to impair digestion and to lessen the appetite at meal time (75). 83. Alcoholic beverages. — ‘‘In the case of an alcoholic beverage we have to deal with something which, like tea and coffee and cocoa and ‘temperance drinks’ is used as a beverage, and to that extent must be classed in the same group. Alcoholic drinks are, however, taken as stimulants, and so resemble tea and coffee and cocoa; but they differ from all these in their action upon the body. Moreover, their abuse gives rise not only to degraded moral and social STIMULANTS AND NARCOTICS 67 conditions, but is also attended with bad hygienic effects. Every one should be informed of their nature and of the dangers attending their use.’”” — Houeu and Srpewick, “‘ The Human Mechanism.” 84, Alcohol as a possible food. — Like the carbohydrates and fat, alcohol is composed of carbon, hydrogen, and oxygen. Since it contains no nitrogen, it has no value in the processes of growth and repair; in other words, it can- not be made into protoplasm. It cannot, therefore, like meat, milk, and eggs answer as a complete food. Alcohol we know may be burned in lamps for the produc- tion of heat, and in engines for the generation of power. Professor Atwater has shown that alcohol also, if used in sufficiently small amounts, may produce within the human body a certain amount of heat and muscular power. Indeed, in some cases of extreme weakness, especially in diseases, alcohol is regarded by some eminent physicians as necessary for saving life, though even for this purpose it is now being used to a less extent in medical practice. 85. Alcohol as a stimulant and a narcotic. — On account of the amount imbibed, however, alcohol, as ordinarily used in beverages, is practically always either a stimulant or a narcotic. In later sections we shall discuss the effects of alcohol on various organs of the body. One fact should, how- ever, be continually emphasized; namely, that even if it should be taken for granted that alcohol, when used by adults in moderation, may generate a certain amount of energy, still this 1s an exceedingly dangerous compound to introduce in any form into the diet of a boy or girl. In the first place, it interferes with the healthy growth of protoplasm; and in the second place, the use of liquors in moderation by a great many people, both young and old, is absolutely im- 68 HUMAN BIOLOGY possible. Men never become drunkards, paupers, and crim- inals by taking the nutrients, starch, sugar, fat, or protein, nor does the taste for any one kind of food become uncontrol- lable, as is so often the case with alcohol. ‘ Till he has tried it, no one can be sure whether he can control his appetite or not. When he has ascertained the fact, it is often too late. The child should be taught to avoid alcohol because it is dangerous to him. The only certain safety for the young lies in total abstinence.” 86. Effects of small and large quantities of alcohol. — The effects of alcohol on the body depend very largely upon the quantity taken; if the amount is small, alcohol may possibly be regarded as a source of energy, and hence in a limited sense, as a food; in larger amounts it increases tem- porarily the activity of the organs of the body, and so it seems to become a stimulant; if still larger quantities are taken, the narcotic effects of alcohol are shown in complete insensibility ; and finally, a sufficient amount may be con- sumed to poison the organs and cause death. No one who begins the use of alcohol expects to take such an amount that it will act as a poison, or even like a narcotic. There is, however, a constant danger that he will do so. 87. Professor Hodge’s experiments with dogs. — During the years 1895 to 1900, Professor Hodge of Clark Univer- sity, Worcester, Mass., carried on some very instructive experiments upon dogs. He secured four spaniel puppies (Fig. 23), all of which were born on Washington’s Birthday, 1895; the two males were brothers, and the females sisters. Professor Hodge carefully watched the four for nearly two months before beginning his experiments, in order to pick out the two most vigorous animals; these he named “ Tipsy ” and “ Bum,” and then put in with their chief meal each day STIMULANTS AND NARCOTICS 69 a moderate amount of alcohol; it was not enough, however, to cause any evidence of intoxication. The other two spaniels, ‘“‘ Nig” and “ Topsy,’ received no alcohol. 88. Effect of a moderate amount of alcohol on activity. — For over five years these dogs were studied, and important a Bum Tipsy Nig Topsy Fig. 23.— The appearance of the four spaniels six months after the experi- ments were begun. (‘‘ Physiological Aspects of the Liquor Problem,” by permission of Dr. Hodge and of Houghton, Mifflin & Co.) facts were learned as to the general effect of alcohol on physiological processes. Early in his observations it became evident to Professor Hodge that the dogs that were receiving the alcohol were far less playful than were those that had no alcohol in their food. To measure the comparative activity of the different animals, he attached to the collar of each dog a Waterbury watch adjusted in such a way that it would tick 70 HUMAN BIOLOGY 2 once each time the animal moved, and so at the close of each day he could determine and set down the record made by each dog. He found that for a period of two months and more “ Bum ” was only 71 per cent as active as “ Nig,’’ while “Tipsy” was only 57 per cent as active as “Topsy” ; in other words, the two alcoholic dogs lost 25 per cent to 50 per cent of their activity. 89. Effect of a moderate amount of alcohol on skill and endurance. — A second series of experiments was made to determine the comparative endurance of the four dogs and their ability to accomplish things. The animals were all taught to retrieve a rubber ball when it was thrown the length of the gymnasium floor, a distance of 100 feet. At each trial the ball was thrown 100 times, and a record was kept of all the dogs that started for the ball and of the one that succeeded in bringing it back. When he had averaged a long series of experiments, Dr. Hodge found that “‘ Bum ” and “ Tipsy ”’ secured the ball only about half as often as did “Nig” and “Topsy ”; the two alcoholic dogs also gave evidence of much greater fatigue during the trials. 90. Effect of a moderate amount of alcohol in producing nervousness. — “ A very striking result of the entire re- search,” says Dr. Hodge, ‘‘ and one entirely unexpected on account of the small doses of alcohol given, has been the ex- treme timidity of the alcoholic dogs. ... While able to hold their own with the other dogs in the kennel, the least thing out of the ordinary caused practically all the alcoholic dogs to exhibit fear, while the others evinced only curiosity or interest. Whistles and bells, in the distance, never ceased to throw them into a panic in which they howled and yelped, while the normal dogs simply barked. This holds true of all the dogs that had alcohol in any amount.” STIMULANTS AND NARCOTICS 71 91. Effect of a moderate amount of alcohol on the off- spring. — Another most striking result of the use of alcohol was shown in its effects on the young of “‘ Bum ” and “ Tipsy.” Of the twenty-three puppies descended from these alcoholic animals, only 17 per cent lived to be normal dogs; the rest were either deformed or unable to nourish themselves, and all died soon after birth. On the other hand, of the forty-five young of “ Nig” and “ Topsy,” over 90 per cent were healthy puppies. Hence, the puppies of the dogs that took alcohol even in moderation were over five tumes as likely to die young as were the puppies born of abstaining parents. 92. Effect of a moderate amount of alcohol on resistance to disease. — In the spring of 1897, in the course of these experiments, a great many dogs throughout the city of Worcester were afflicted with distemper, and dogs sick with the disease were not uncommon on the streets. At that time, Dr. Hodge had, in all, five dogs that were taking alcohol and four that were not. It was found that there was a marked difference in the effect of the disease on the two classes of animals. All the alcoholic dogs, with the exception of the one that had taken the smallest amount, had the distemper with great severity ; all the normal dogs had it in the mildest possible form. 93. Summary of Professor Hodge’s conclusions. — Hence, we may conclude from these experiments that alcohol, when given to dogs, even in moderation, (1) decreases their natural activity, (2) lessens their power of endurance and their ability to accomplish things, (3) decreases their power of resistance to disease, and (4) increases the percentage of deformity and of death among their offspring. These con- clusions have a most important bearing on the general sub- ject that we are considering, for observations show that sim- 72 HUMAN BIOLOGY ilar effects follow even the moderate use of liquor by human beings, as the following paragraphs will show. 94. Effect of the moderate use of alcohol on mental activity. — ‘‘ Few causes are more effective in leading to the abuse of alcohol than the idea that when one finds difficulty in doing a thing it may be accomplished more easily by hav- ing recourse to beer, or wine, or whisky for their ‘ stimulating’ -effect. In general, so far is this from being the truth that the person seeking such aid is really using a hypnotic and a depressant. Obviously he would be acting more wisely to adopt other methods of accomplishing his end. Nor is this conclusion merely theoretical. Brain workers who wish to “keep a clear head ” almost universally avoid alcoholic drinks, at least until work is over. And even among those who do drink it is customary to avoid drinking until the day’s work is done.” ! 95. Effect of a moderate use of alcohol on muscular ac- tivity. — That the general effect of alcoholic drinks on muscu- lar activity is a depressant rather than a stimulant was shown by experiments on English soldiers during forced marches in Africa. ‘‘ It was found that when a ration of rum was served out, the soldier at first marched more briskly, but after about three miles had been traversed the effect of it seemed to be worn off, and then he lagged more than before. If a second ration were given, its effect was less marked, and wore off sooner than that of the first. A ration of beef tea, however, seemed to have as great a stimulating effect as one of rum, and not to be followed by any secondary depres- sion.” — T. LaupER-BRUNTON. 96. Effect of a moderate use of alcohol on manual dexter- ity. — A German scientist determined the effect of alcohol 1 Hough and Sedgwick, ‘The Human Mechanism.” STIMULANTS AND NARCOTICS 73 on four typesetters in the following way. ‘‘ Four days were used for the tests, the first and third of which were ‘normal’ days; the second and fourth were ‘ alcohol days.’ On the alcohol days each man received about seven ounces of a Greek wine... aquarter of an hour before the trials took place.’ On the “ alcohol days ”’ it was found that the amount of type set was on the average 15 per cent less than that set on the ‘‘ normal days.” 97. Moderate use of alcohol in relation to disease. — “A much larger number of the victims of alcoholic intemper- ance die of some infectious disease than of the special alco- holic infections. Attention has been repeatedly called in this article to the lowering of the resistance of alcoholic patients to many infectious diseases. . . . This lowered re- sistance is manifested both by increased liability to contract the disease and by the greater severity of the disease.’”’ —_ Dr. Wetcu, in “‘ Physiological Aspects of the Liquor Problem.” Physicians also recognize that those who use alcohol are more susceptible to pneumonia, cholera, and other diseases, and that the percentage of recovery of such patients is lower than is that of total abstainers. 98. Total abstinence and life insurance.’ — “It is now becoming generally recognized that the alcohol habit is one of the main factors in determining length of life. No life office will knowingly accept the proposal of any one known as ahard drinker. Evidence of a very striking kind is rapidly accumulating, which shows that even the moderate use of alcohol is prejudicial to health and longevity. In England about a dozen life offices recognize this fact in one of two 1These quotations were furnished the authors by the Equitable Life Assurance Society of the United States. 74 HUMAN BIOLOGY ways: (1) by giving a reduction of premium to abstainers, or (2) by awarding them a larger share in the profits. “ Ten years ago the American Temperance Life Insurance Association was formed in this city (N.Y.), and accepts nothing but total abstinence risks. It has had pronounced success, and has paid something like $200,000 in death claims. President Frank Delano states that the results of their business show that the ratio of their death rate to that of general risks is about 26 per cent in favor of the total abstainer.”’ — Wiuu1am E. JoHNsoN. 99. Business arguments for total abstinence. — The value of total abstinence as a business: asset is clearly shown by the following rules of railroads: Rule 17, New York Central & Hudson River R.R.: “ The use of intoxicating drink on the road or about the premises of the corpora- tion is strictly forbidden. No one will be employed, or continued in employment, who is known to be in the habit of drinking intoxicating liquor.” Rule H, New York, New Haven & Hartford R.R.: ‘ The use of intoxicants by employees while on duty is prohibited. Their habitual use, or the frequenting of places where they are sold, is sufficient cause for dismissal.” General Order No. 12, Delaware, Lackawanna & Western R.R.: ‘The use of intoxicants while on or off duty, or the visiting of saloons or places where liquor is sold, in- capacitates men for railroad service, and is absolutely pro- hibited. Any violation of this rule by employees in engine, train, yard, or station service will be sufficient cause for dis- missal.”’ 100. The cost of intemperance. — The following figures, compiled by the League for Social Service of New York City from the United States Census, present some very striking STIMULANTS AND NARCOTICS 75 facts as to the cost to our country of the abuse of alcohol. During the year 1880 (and the same figures would doubtless hold true for any other year), it was found that three fourths of all the pauperism, one fourth of all the insanity, and three fourths of all the crime in the United States were directly caused by intoxicating drinks. Hence if the use of intoxi- cating liquor could be abolished, the heavy expense of main- taining the police force, the criminal courts, insane asylums, and charity organizations, would be very greatly reduced. 101. Concluding remarks on the use of alcoholic bev- erages. — “‘In the foregoing pages we have stated the sali- ent facts concerning the physiological action of alcohol and alcoholic drinks. It only remains to point out for, the student the obvious conclusions to be drawn from them and from the long and on the whole very sad experience of the race with alcoholic drinks. The first is that, except in sick- ness and under the advice of a physician, alcoholic drinks are wholly unnecessary, and much more likely to prove harmful than beneficial. The last is that their frequent, and especially their constant, use is attended with the gravest danger to the user, no matter how strong or self-controlled he may be. The only absolutely safe attitude toward alcoholic drinks is that of total abstinence from their use as bever- ages.” — Houau and Srepewick, “ The Human Mechanism.” III. Toxpacco 102. Effect of tobacco on growth.—JIn discussing the effects of tobacco, it is important, as was the case with tea and coffee, to distinguish between the results of its use by the young and by adults. Just because his father seems to be using tobacco without harm is no reason why a boy can safely smoke. We have already called attention to the complex 76 HUMAN BIOLOGY composition of protoplasm. During the whole period in which the body is attaining its growth this living substance is affected far more appreciably and seriously by the use of stimulants and narcotics than is the case later in life. Tobacco is a narcotic in its effects; that is, it tends to decrease activity and likewise growth. That such is its effect during early life has been abundantly proved in many ways. But perhaps the most conclusive facts are those presented by actual measurements made in college gymnasiums. Dr. Hitchcock, of Amherst College, who has made careful measurements of college students for a good many years, finds that those who do not smoke increase in height during their college course 37 per cent more than those who do smoke, and in chest girth this difference is 42 per cent, or nearly one half as much again. Dr. Seaver of the Yale Gymnasium finds, also, that in height and lung capacity smokers are considerably inferior to those who do not use tobacco. 103. Effect of tobacco on mental development. — Dr. George L. Meylan, Director of the gymnasium of Columbia University, made a careful comparison during two years of the relative physical measurements, rate of growth, and scholarship of 115 college men who smoked and 108 men in the same class who were non-smokers.! He found (1) that the smokers were on the average eight months older, which means that they had entered college this much later; and (2) that “the scholarship standing of smokers was distinctly lower than that of the non-smokers,” showing “that the use of tobacco by college students is closely asso- ciated with idleness, lack of ambition, lack of application, and low scholarship.” 1 Popular Science Monthly, August, 1910. STIMULANTS AND NARCOTICS TT “Whatever difference of opinion there may be regarding the effect of tobacco on adults—-and much difference of opinion exists — there is almost complete agreement among those best qualified to know that the use of tobacco is in a high degree harmful to children and youths. Physicians, teachers, and others who have much to do with boys very generally remark that those who begin to smoke at an early age very seldom amount to much.” ' Dr. Andrew D. White, for twenty years President of Cornell University, out of his wide experience in education, sums up the matter as follows: “I never knew a student to smoke cigarettes who did not disappoint expectations, or to use a vernacular expression, ‘ kinder peter out.’ I con- sider a student in college who smokes as actually handicap- ping himself for his whole future career. I am not fanatical in regard to smoking. It seems to me possible that men who have attained their growth and are in full health and strength may not be injured by moderate smoking at times. I will confess to you that at one period of my life I was a smoker myself, though in a very moderate degree. And should you feel a strong desire to smoke, thinking it may rest you and change happily at times the current of your thought, I may perhaps commend to you my own example; for I began my smoking at the age of forty-five and ended it ten years ‘ago at the age of seventy.” 104. Tobacco and athletics. — One of the rules rigidly enforced in athletic contests is that all candidates must abstain from the use of tobacco while in training. The reason for this insistence is the fact that tobacco seriously interferes with the action of the lungs and heart; therefore, those who smoke are found to be easily “‘ winded” in the games. - 78 HUMAN BIOLOGY An investigation! has been recently carried on among the football squads of fourteen of the American colleges and uni- versities to determine the relative success of the smokers and non-smokers who tried for positions on the varsity teams. ‘Six institutions furnished data relating to the ‘ try outs.’ A total of 210 men contested for positions on the first teams ; of this number 93 were smokers, and 117 were non-smokers. Of those who were successful, 31 (i.e. 33 %) were smokers, and 77 (i.e. 65%) were non-smokers. It will be observed that only half as many smokers were successful as non-smokers. . . .” Hence, the ambitious boy, who has any regard for develop- ing a vigorous body fitted for athletic success, for training - a mind capable of clear thinking, and for preparing himself for a successful life work, will resist all temptations to smoke, at least until he has attained his full growth. IV. Druces AnD Patent MEDICINES 105. Headache powders.— Drugs are chemical sub- stances used in the preparation of medicines. They should never be taken except under the direction of a competent physician. Headache medicines usually contain some chemi- cal (e.g. acetanilid) which reduces the heart action and so relieves the pain by diminishing the blood pressure without removing the cause of the pain; for the real cause may be disordered digestion or eye strain. Cases of permanent injury and even of death have resulted from taking these headache compounds (Fig. 24). 106. Soothing sirups and cough medicines. —In most soothing sirups and cough medicines are found substances derived from opium, which is a powerful narcotic. Hence, 1“Smoking and Football Men.” — Popular Science Monthly, October, 1912. STIMULANTS AND NARCOTICS 79 children who are given soothing sirups often become stupefied. If these compounds are given frequently, they injure the child permanently, and in larger doses have caused death. If cough sirups and like compounds are taken often, an opium BEWARE OF ACETANILID A large proportion of the most common head- ache medicines sold at drug stores depend for their effectiveness on the heart-depressing ac- tion of acetanilid. In some cases three or more grains of this drug are present in each dose. The Pure Food and Drug Law requires all makers of patent medicines to indicate clearly on the labels of such preparations the presence of acetanilid and other dangerous compounds.. Hence one has but to read the labels and avoid these nostrums in order to protect himself. Take no headache remedy without consulting a doctor, unless you are sure it contains no acetanilid. Make the druggist tell you. He is responsible. A suit for damages has recently been won against a New York drug store for illness consequent upon the sale of a “ guaranteed harmless” headache tablet containing three grains of acetanilid. Fic. 24. — Acetanilid and other drugs in patent medicines. habit may be developed, which is even more difficult to over- come than is the alcohol habit. 107. Patent medicines as “bracers.” — Figure 25 repre- sents the percentage of alcohol contained in three ‘patent medicines” as given by the Massachusetts State Board of HUMAN BIOLOGY 80 ‘sionbr] UI pues SeuUTOIpeUT yUsIed UT youOOTY Jo eBvjUs0IEg — “CZ “OT STIMULANTS AND NARCOTICS 81 Health in published document No. 34, as compared with the percentages of alcohol found in whisky, champagne, claret, and beer. The stomach bitters (Fig. 25), for example, con- tained over eight times as much alcohol as that found in beer. Hence, the average drug store where these patent medicines are freely sold must share with the liquor saloon the heavy responsibility for the prevalence of the drink habit. 108. Pure food and drug law. — One of the most impor- tant laws passed by the 59th Congress of the United States was that which compels every manufacturer of foods or medicines to state on the label the composition of each. Analyses of foods and drugs have proved that hitherto many of them were largely adulterated by cheap and often injurious compounds, put in to increase the manufacturers’ profits. Then, too, as already stated, many patent medicines contain high percentages of alcohol and other dangerous drugs. Under the new law the purchaser, if he takes the trouble to read the printed label, should be able to determine exactly what he is paying for and putting into his body. 109. Optional home work. — Examine the labels on any patent medicine bottles or boxes you can find. Make a list of such com- pounds as contain alcohol, opium, morphine, chloral, acetanilid, or phenacetin, and state after each compound the percentage of each of the drugs named. CHAPTER V DIGESTION AND ABSORPTION OF THE NUTRIENTS I. GENERAL SURVEY OF THE DIGESTIVE SYSTEM 110. Necessity of digestion.— In Chapter III we dis- cussed the composition, uses, and the preparation of foods. We learned in our study of plant biology (P. B., Ch. IV) that certain of the food substances will readily pass through the walls of plant cells, while others will not. Hence, the latter, to become available for use in other cells, must be changed to soluble form, and this change we called digestion. We shall now discuss similar changes that take place in foods within our bodies; for before the different food sub- stances can reach the cells of the brain, the muscles, or the bones where they are needed, they must be changed from a solid or semifluid condition into liquids that can pass through the walls of the cells that lie between the interior of the food canal and the blood. These necessary changes are accomplished within our bodies in the alimentary canal, a complicated tube nearly thirty feet in length. 111. Parts of the alimentary canal.— The alimentary canal (Fig. 26), as in the other vertebrates studied, begins with the mouth opening ; it enlarges to form the mouth cavity, and this in turn communicates behind with a somewhat smaller throat cavity. Below the throat is the gullet, which conducts the food into an enlarged pouch, the stomach. Most of the lower half of the trunk is filled with the much coiled 82 DIGESTION AND ABSORPTION OF NUTRIENTS 83 ~ intestines which begin at the stomach and open to the out- side of the body at the lower part of the trunk. J passage from nose to throat cavity of mouth throat cavity opening of windpipe pylorus transverse colon (cut) pancreatic duct liver— common orifice of bile, and pancreatic ducts beginning of small intestine appendix Fic. 26.— Parts of the alimentary canal. (The liver has been tilted upward to show the gall bladder on its lower surface; a piece of the large intes- tine has been removed to show the pancreas behind it.) Compare this figure with Fig. 2 which shows all the organs in position. 112. Digestive glands. — Several organs that are neces- sary in the process of digestion, as already discussed in the 84 HUMAN BIOLOGY fish and frog, lie outside the alimentary canal itself, but are connected with it. These are the digestive glands. They produce digestive ferments (P. B., 53), which after being dissolved in water are carried into the food canal through small pipes or ducts. Thus the salivary glands pour their secretions into the mouth cavity, and the liver and pancreas, situated near the stomach, empty their juices into the in- testine (Fig. 26). Il. THe Movurs Cavity Anp Its FUNCTIONS 113. Study of the mouth cavity.— (Home work.) Take a position with your back toward a window or some bright light, and study your mouth cavity by means of a hand mirror. ‘A. Walls of the mouth cavity.— The walls that are rigid are composed largely of bone; those that are yielding are largely made of muscle. 1. Press your forefinger against the roof, the side walls, and the floor of the mouth cavity beneath the tongue Which walls are composed of bone? which of muscle? 2. What is the color of the inner walls of the mouth cavity? This color is due to the blood vessels that lie close to the surface. 3. Rub your finger over the mucous membrane which covers these walls. The substance on your finger is largely mucus. Describe the mucus and tell where it is found. B. Tongue. 1. To what part of the mouth cavity is the tongue attached? 2. Chew a piece of apple or other solid food; note and describe the action of the tongue during the process of chewing food. 3. Swallow some solid food, and describe the action of the tongue in the process of swallowing. DIGESTION AND ABSORPTION OF NUTRIENTS 85 114. Structure and functions of the tongue. — The tongue is an elongated mass of muscle tissue (Fig. 27). The muscle fibers run through it in three directions, and by their separate or combined action the free end of this organ may be moved about at will. When one ex- amines the mucous membrane on the upper surface of the tongue, it is possible to see elevations of different sizes, called papille. Nerve fi- bers carry messages from these papille to the brain, and thus we become conscious of sen- sations of taste. Among the carniv- ora or flesh-eating animals the papillee on the tongue are Fie. 27.— Mouth cavity. especially rigid. This enables the dog, cat, lion, or tiger to scrape the meat from the bones and to extract the marrow after the bones are broken open. ‘ 115. Study of the teeth. — (Home work.) | 1. Bite off a piece of apple or bread. a. Describe the motion of the jaws in biting off a piece of food. b. In what part of each jaw are found the teeth that are used in biting food? c. Describe the shape and cutting surface of these teeth. 86 HUMAN BIOLOGY 2. Chew or grind a piece of apple or bread. a. Describe the motion of the jaws in grinding food. b. In what part of each jaw are found the teeth that are used in grinding or chewing food (Fig. 28)? c. Describe the shape and grinding surface of these teeth. 3. There are two kinds of cutting or biting teeth (Fig. 28), the incisors (Latin, in- cisum, from incidere = to cut into), and the canines (Latin, canis =dog, so- called because they often resemble the pointed teeth of a dog). incisors al cael ' -canine , , Fie. 28.— Teeth in upper jaw. There are also two kinds of grinding teeth, the bicuspids (Latin, 6¢ = two + cuspis = point), and the molars (Latin, molaris = a millstone). a. (Optional.) Human teeth may be obtained from a dentist. They should be cleaned by boiling them in strong caustic soda solution, then in water. should examine and draw one of each of the kinds of teeth named above. b. Determine by the use of a mirror the number of teeth of each kind that you have and record the numbers in a table in your notebook as follows :— If possible, each student Ricet Har oF Upper Jaw Lert Har or Uprer Jaw Ricur Har or Lower Jaw Lert Har or Lower Jaw Incisors. Canines Bicuspids . Molars . DIGESTION AND ABSORPTION OF NUTRIENTS 87 4, Examine carefully each of the teeth in your mouth and indicate in a table like the following the number of cavities (unfilled) and the number of fillings that you find. Ricut Haur or| Lerr Harr or | Riest Harr or| Lerr Hatr or Uprer Jaw Upper Jaw | Lower Jaw Lower JAw Cavity | Filling | Cavity | Filling | Cavity | Filling | Cavity | Filling Incisors . Canines . Bicuspids Molars 116. Arrangement of the teeth.— Within the mouth cavity the solid food is cut into small pieces, mixed with the juices of the mouth, and then ground into a pulpy mass. A large part of this work is done by the teeth, which are arranged in two semicircular arches (Fig. 29). In a normal set of teeth each tooth in the lower jaw works against a corresponding tooth in Fic. 29.—Arrangement of the . ue teeth. the upper jaw, and this is very necessary in order to chew the food properly and to keep teeth and gums in a healthy condition. If, however, the teeth do not develop as described above, a competent dentist should be employed to correct the irregularities. 117. Milk teeth. — During early childhood there appears a first set. of milk teeth, which later are gradually loosened and dis- 88 placed by the growth of the permanent set. HUMAN BIOLOGY There are but twenty teeth in the milk set and their arrangement is as follows : — Ricut Haur or| Lerr Havr or |Ricat Har or| Lerr Harr or Upper Jaw Uprer JAw Lower Jaw Lower Jaw Incisors 2 : 2 2 2 Canines 1 1 1 1 Molars 2 2 2 2 Bicuspids are, therefore, wanting, and the milk molars occupy the position in each half jaw that later is filled by the two bicuspids crown neck root Fic. 30.— Longitudinal section of a canine tooth. cement of the permanent set. The teeth appear gradually, the lower inci- sors usually being the first to push , through the gums at about the sixth month. The third permanent mo- lars of each half jaw often appear as late as the twentieth year; they are called the wisdom teeth. 118. Structure of teeth.— The exposed. portion of a tooth is called the crown (Fig. 30). It is covered with a layer of enamel, which is the hardest tissue in the body. The root of the tooth is imbedded in a socket in the bone of the jaw. It has no enamel, but, instead, its outer layer is a modified bone tissue called ce- ment. The incisors and canines usually have but a single root, the bicuspids may have two, and the molars are often held in the jawbone by three, four, or five roots. In the region be- DIGESTION AND ABSORPTION OF NUTRIENTS 89 tween the crown and the root is the neck of the tooth, which is surrounded by the gums. The internal structure of the tooth is well shown in a verti- cal section (Fig. 30). The covering of enamel is thickest over the top of the crown; it becomes thinner down the exposed sides, and disappears in the neck region. The largest part of the tooth is composed of bony dentine. In the central part is the pulp cavity. This region is well supplied with nerves and blood vessels, which enter through a small open- ing at the end of each root. The blood furnishes the teeth with new building material. 119. Care of the teeth.— Too much stress cannot be laid on the importance of caring for the teeth, since decay- ing teeth are frequently painful, are always unsightly, are usually the cause of an ill-smelling breath, and often lead to indigestion. Immediately after eating, one should remove any bits of food from between the teeth by using a wooden toothpick, dental floss, or thread. Pins, knife-blades, or other metallic implements should never be used for this purpose. The teeth should then be brushed thoroughly on all sides, and warm water and a little castile soap or reliable tooth powder should be used. The sides of the teeth should be brushed from the gums toward the crown in order to avoid pushing the gums away from the neck of the tooth. Since the enamel that covers the crown of the tooth is composed entirely of mineral matter, it cannot, of course, decay. If, however, food is allowed to decompose on or between the teeth, the acids formed by the action of the bacteria gradually dissolve the enamel until a cavity is formed. When the dentine is reached, the bacteria directly cause this part of the tooth to decay, since it contains living matter. 90 HUMAN BIOLOGY The teeth ought never to be used to crack nuts or to bite hard substances, for while the enamel is a very hard sub- stance, it is also brittle and may be cracked or broken off by such treatment. If once lost, it will not grow again. It is evident, therefore, that it is very essential to protect this outer layer, both from the action of acids, and from mechanical injuries. Some people seem to think that the loss of natural teeth is not a very serious matter, and that false teeth are just as effective as those teeth provided by nature. Experi- ments have shown, however, that the power to crush food with false teeth is only about one fifth that of the power exerted by a normal set of teeth. Hence, loss of teeth is very likely to result in imperfect mastication of food, with consequent ill-health resulting from indigestion. If, however, one has been unfortunate enough to have lost one or more teeth, the gaps should be promptly filled by bridge work. The teeth should be examined by a dentist at least twice a year so that any cavities found may be promptly filled. In short, everything possible should be done to secure and preserve a beautiful and effective set of teeth. 120. Importance of the digestion of starch.—In 47 of “Plant Biology’ we proved that starch can not pass through the walls of cells, and we likewise showed in 49 how this food substance is made ready by the process of digestion to pass through membranes. Many of the foods we eat contain large percentages of starch. We are now to show experimentally how starch is digested in the human body. 121. Does saliva digest starch ?— Laboratory demonstra- tion. Prepare some starch paste by boiling in a test tube of water an amount of arrowroot starch (or corn starch, if DIGESTION AND ABSORPTION OF NUTRIENTS 91 the atrowroot cannot be obtained) equal to half the size of a pea. 1. Pour a small amount of the starch paste into a test tube, add some Fehling’s solution, and boil. Is grape sugar present? How do you know? 2. Put some saliva into a clean test tube. Test it with Fehling’s solution as you did the starch. Does this saliva contain grape sugar? How do you know? 3. In another clean test tube pour some saliva into some of the starch paste, shake the mixture, and warm it gently for a few moments to the same temperature as that of the mouth. Now test with Fehling’s solution, as in 1 above. a. State what was done, the result, and the conclusion. b. What, therefore, is the effect of saliva on boiled starch? c. Name several foods already studied that could be partially digested by saliva. 4, (Optional home work.) Take some popped corn or shredded wheat into the mouth and chew it thoroughly. Can you detect any sweet taste at first? Can you after chewing for a time? What does this experiment teach you as to one advantage of thoroughly chewing the food ? 122. Position and action of the salivary glands. — In addition to the mucus given out by the mucous membrane (113) the mouth receives another secretion called saliva. At the sight or smell of tempting food ‘‘the mouth waters.” Saliva is secreted by the salivary glands. Two of these glands (the parotids, from Greek, meaning “beside the ear”) are located near the back of the lower jawbone just beneath and in front of the ear. Any one who has had the mumps can readily locate these organs, for mumps is a disease in which these glands swell. From the parotid gland of each side a duct conveys saliva along through the walls of the cheek. This duct opens at the top of a small elevation, which may be felt with the tip of one’s tongue opposite the upper second molar teeth. Two other pairs of glands (the submavzillary, Latin, sub = be- neath + maxilla = jawbone, and the sublingual, Latin, sub = 92 HUMAN BIOLOGY beneath + lingua = tongue) lie in the muscular floor of the mouth cavity, and the ducts from these glands open in the floor of the mouth under the tongue. 123. Uses of saliva.— (1) The saliva aids the mucus in keeping the mouth moist, and thus we are enabled to talk easily. (2) It moistens the food for swallowing. The importance of this function is appreciated when one tries to hurry in swallowing the crumbs of dry cracker. (3) Saliva helps to dissolve sugar and salt,! thus enabling us to taste them. If the tongue is wiped dry and a piece of sugar is placed upon it, we have no sensation of taste until the sugar has been partially dissolved by the mixture of saliva and mucus that is poured upon it. (4) Besides the three mechanical functions of saliva that we have just enu- merated, this secretion digests cooked starch, as we have already shown. This digestive action is due to a ferment known as ptyalin (pronounced ty’alin) which acts in the same manner as the diastase found in plants. III. Tae Turoat Caviry AND GULLET AND THEIR FUNCTIONS 124. Structure of the throat and gullet. — The cavity of the throat is behind the mouth. If one holds a mirror in front of the mouth opening and presses down upon the tongue with a spoon, one sees hanging down a small, fingerlike extension of the soft palate, called the wwla. When food is swallowed, this little tongue of the soft palate is shoved backward into a horizontal position, where it helps to separate the throat cavity from the nose cavity. The lower part of the throat narrows into the gullet. This tube traverses the length of the chest cavity, and as it nears the stomach, it passes through the diaphragm. Like all other parts of the ali- mentary canal it is lined with mucous membrane, which furnishes a 1See 130, A, 1. DIGESTION AND ABSORPTION OF NUTRIENTS 93 soft, moist surface for the passage of food. Outside the mucous membrane are rings of circular muscle running around the gullet. 125. Functions of the throat and gullet. — The food is quickly forced out of the throat cavity into the gullet, and is pushed slowly down the gullet by the successive contractions of the rings of muscle just described. After being swallowed from the throat, the food does not drop into the stomach, for the walls of the gullet are pressed together by surrounding organs, except when this tube is opened by the passing food. In fact, after practice, one can swallow when standing on one’s head, and most quadrupeds (horse, dog, cow), when feeding, hold the head below the level of the stomach. IV. THE SToMAcH AND ITs FUNCTIONS 126. Position, size, shape.— The stomach is a curved muscular pouch, which lies about midway between the upper and lower ends of the trunk, with its larger end lying toward ‘the left side of the body, where it communicates with the gullet (Fig. 26). When moderately filled, this organ holds 34 to 4 quarts. The small intestine is con- tinuous with the right end of the stomach, mpeping the communication between the two (known as the pylorus, from Greek, meaning gate- keeper) being controlled by a ring of - muscle. 127. The lining of the stomach and the gastric glands.—If one examines with a lens the mucous lining of the stomach, a countless number of small openings are 4,, 31 Three seen which look like pin pricks. These gastric glands. are the pores through which a digestive fluid known as gastric juice is discharged from the gastric glands (Fig. 31). This digestive fluid is composed of water 94 HUMAN BIOLOGY (over 99 per cent), free hydrochloric acid and a digestive fer- ment called pepsin. 128. Muscles of the stomach. — The chief function of the human stomach is to secrete the gastric juice and to mix this juice thoroughly with the food. The muscular walls are well adapted for this purpose. When the food reaches the stomach, the gastric juice oozes out upon it, and the mixture is pushed back and forth and up and down by the successive action of the different layers of muscles. The return of the food to the mouth cavity is prevented by the contraction of the circular muscles at the lower end of the gullet, except in the case of nausea, when they relax and allow the stomach to rid itself of its contents. The circular muscle at the pyloric end of the stomach (Fig. 26) relaxes from time to time, and the partially digested food is pushed on into the intestine. Fortunately for the well-being of the body, all these pro- cesses are entirely automatic; that is, they are carried on without our conscious direction. The muscles of the ali- mentary canal for this reason are called involuntary (Latin, in = without + voluntas = will). 129. Digestion in the stomach. — The gastric juice has practically no effect on the nutrients starch and fat. The saliva, however, that is mixed with the food and swallowed with it continues to act upon the starch for a time, particu- larly in the upper part of the stomach. Sugars and soluble salts (that is, salts that dissolve in water), if not dissolved in the mouth, are readily liquefied by the water of the gastric juice. Certain mineral food substances, however, like phos- phate of lime found in milk, are not soluble in water, and these insoluble salts reach the stomach unchanged. The following experiment illustrates the way in which mineral matters are made liquid by the hydrochloric acid in the gastric juice. DIGESTION AND ABSORPTION OF NUTRIENTS 95 130. Digestion of mineral matters.— (Optional.) Laboratory demonstration. Note to Teacher: Part A should be demonstrated in connection with the study of saliva; Part B, in connection with gastric diges- tion. Materials: Table salt, phosphate of lime, diluted hydrochloric acid (one part acid to six parts water). A. Soluble mineral matters. 1. Put some table salt into a test tube, add water, and shake well. Does the salt dissolve? How do you know? 2. Saliva is largely (over 99 per cent) composed of water. How, then, are soluble mineral matters made liquid in the mouth? B. Insoluble mineral matters. 1. Put some insoluble mineral matter like phosphate of lime (which is one of the constituents of milk) into a test tube, add water, and shake well, then allow the tube to stand for a time before answering the following questions. a. Does phosphate of lime dissolve in water? How do you know? Why is phosphate of lime called an insoluble mineral matter? b. Shake the mixture again and add some diluted hydro- chloric acid. What change do you observe? 2. Hydrochloric acid is one of the ingredients of gastric juice. How, then, are insoluble mineral matters like phos- phate of lime digested in the stomach? 131. Digestion of proteins. — One of the most important actions which takes place in the stomach is the digestion of proteins. This class of nutrients is not readily soluble in water and so cannot pass through the walls of cells (P. B., 52). Hence, before proteins can be made available for use in the body they must be changed to a soluble form known as 96 HUMAN BIOLOGY peptone (P. B., 58). This chemical change is brought about in our bodies to some extent by the gastric juice. 182. Digestion of proteins. — Optional laboratory demonstra- tion. Materials: Boiled egg, powdered: pepsin (which should be ob- tained fresh or kept in a tightly stoppered bottle), hydrochloric acid, water; test tubes. Each of the following experiments should be kept throughout the whole time as nearly as possible at the temperature of the body (98.6° F.). A. To prove that protein requires digestion after it is swallowed. 1. Shave off with a knife and cut into the finest pieces possible a part of the white of a boiled egg (or better, grate the egg). The solid constituents of egg are largely pro- tein. Put into a test tube a small amount (about twice the size of a pea) of this minced egg, add water, and shake. Label the test tube No. 1, and allow the mix- ture to stand for a day or two as nearly as possible at a temperature of 98.6° F. (which is the normal tem- perature of the interior of our bodies). a. Has all the egg been made liquid or digested by the water? How do you know? b. Pour off some of the clear liquid into a test tube, and add nitric acid and boil. Has any of the protein been digested? How do you know? 2. Into another test tube put the same amount of minced egg, add a spoonful or more of saliva. Label it test tube No. 2. Shake and allow it to stand for a day or two beside test tube No. 1. a. Is protein digested by saliva? How do you know? b. What do you therefore conclude in regard to the possibility of protein-digestion by the saliva? B. To prove that gastric juice digests protein. 1. Into a third test tube put a small amount of the minced egg. Half fill the tube with water, add powdered pepsin to DIGESTION AND ABSORPTION OF NUTRIENTS 97 the amount equal to about the size of a pea, and also add five to ten drops of diluted hydrochloric acid. (Water, pepsin, and hydrochloric acid are the three principal ingredients of gastric juice.) Label the test ‘tube No. 3, shake the mixture, and put it in a warm place beside test tubes 1 and 2. (Since it is difficult to get the exact proportion of the three ingredients of gastric juice, it is well to prepare several tubes as de- scribed above, labelling each test tube No. 3.) At the end of a few hours or a day examine the test tubes con- taining the minced egg and the artificial gastric juice, comparing them with test tubes 1 and 2. Has the egg been digested? How do you know? V. Tue SmMauu INTESTINE AND ITs FUNCTIONS 133. Position, form, and size. — The small intestine is a much-coiled tube, filling the larger portion of the abdominal cavity (Fig. 2). It is usually twenty feet or more in length, and therefore constitutes nearly four fifths of the whole length of the alimentary canal. Beginning at the stomach, it decreases somewhat, in size until it opens into the large intestine. 134. Peritoneum. — The whole abdominal cavity is lined with thin, smooth membrane called the peritoneum. Sheets of peritoneum likewise inclose the various organs found in the abdominal cavity, and help to connect these organs to the walls of the abdomen. Peritonitis is an inflammation of any portion of this membrane. 135. Digestion in the small intestines. — In the intestines important digestive processes are carried on (1) by the juices secreted in the glands found in the inner wall of the intestine (intestinal glands), (2) by the pancreatic juice secreted by the pancreas, and (3) by the bile secreted by the liver. All these juices, when mixed with the food in the intestine, H 98 HUMAN BIOLOGY bring about the digestion of fats and complete the digestion of starch and proteins. The pancreas (Fig. 26) lies just below the stomach and extends from the region of the pylorus toward the left side of the body. Within the gland is secreted the pancreatic juice, which is poured out through a duct upon the food just after it enters the small intestine. Pancreatic juice digests three of the nutrients; namely, starch, pro- teins, and fats. Like saliva, pancreatic juice changes starch into sugar, and like gastric juice, it converts proteins into peptones. The heat of the body melts much of the fat before it reaches the in- testine, but this liquid cannot be absorbed until it has been still further acted upon chemically by the pancreatic juice and bile. VI. THe Larce INTESTINE AND ITS FUNCTIONS 136. Position, form, and size. — The large intestine is the last portion of the alimentary canal. It is a tube five or six feet long, with a gradually decreasing diameter. Beginning in the lower right- hand region of the abdominal cavity as a sac-like pouch (Fig. 26), the large intestine passes upward on the right side of the body cavity to thé lower surface of the stomach; it then crosses the abdominal cavity ; a third portion continues downward on the left side. The large intestine then takes an S-shaped course and passes to the ex- terior of the body by a short, straight tube. 137. Vermiform appendix. — On the right side of the body, and connected with the beginning of the large intestine, is a small, tubular sac about the size of a lead pencil, and usually about four inches long (Fig. 26). From its more or less twisted shape it has received the name vermiform appendix (Latin, vermiform = worm-shaped). Appendicitis is a diseased condition arising from inflammation in the tissues of the appendix. VII. ABSORPTION FROM THE ALIMENTARY CANAL 138. Necessity for the absorption of food. — We have now learned something of the processes of digestion. We DIGESTION AND ABSORPTION OF NUTRIENTS 99 | have seen that the foods we eat are ground up in the mouth cavity by the teeth and thus made ready for the action of the various digestive juices. We have also demonstrated that sugars and soluble salts are dissolved in the mouth; that insoluble mineral matters are made soluble in the stomach ; that starch is changed to sugar by the saliva and pancreatic juice; that proteins are converted into peptones by the pancreatic and gastric juices; and that fats are digested in the intestines by the combined action of bile and pancreatic juice. Were the food to remain within the alimentary canal, however, even though it had been thoroughly digested, it would still be, in a certain sense, outside the body, since this canal is a continuous tube opening to the exterior at either end. In order to furnish material for building and repairing the various tissues, the liquid nutrients must be distributed to the tissues wherever needed. This is accom- plished through the agency of the blood system. We have now to consider the process of absorption, which includes the final steps whereby foods become a part of blood. By absorp- tion is meant the passage of the digested food through the lining of the alimentary canal, and through the thin walls of the count- less blood vessels that lie close at hand. 139. Absorption in the mouth, throat, gullet, and stomach. — While the mouth, throat, and gullet all have a moist lining, gener- ously supplied with thin-walled blood vessels, relatively little ab- sorption takes place in these regions; first, because only a small amount of the food has been digested, and secondly, because the food does not remain long enough in these organs for absorption to take place. The food usually remains in the stomach for several hours, and one would naturally expect that a good deal of absorption would take place during this time. But we must remember that the con- traction of the stomach muscles keeps the food in constant motion. 100 HUMAN BIOLOGY This movement, while favorable to digestion, diminishes absorp- tion, because the liquefied food does not remain long enough in one place to be absorbed by the blood. 140. Absorption in the small intestine. — We, therefore, find that most of our food passes through the pylorus before it is absorbed. In the structure of the small intestine, how- ever, we seem to find every possible provision for gathering up the nutrients. In the first place, the lining of this tube at intervals is elevated to form ridges that run two thirds ‘of the way around the interior wall, and some of them project about a third of an inch into the cavity of the intestines (Fig. 2). Like little dams, they delay the onward flow of the food, and they also increase considerably the large surface for absorption. The absorbing surface is multiplied still further by the villi. If one were to examine with a hand lens the mucous lining of the small intestine, one would see that the ridges and the depressions are covered with tiny, hairlike pro- cesses that give a velvety appearance to the surface. Each of these minute elevations is called a villus (Latin, villus =a tuft of hair). The villi are ex- ceedingly numerous in the small intes- tine of man, the total number being estimated at four millions. The ab- sorbent action of the villi may be com- pared with the absorption that takes place through the walls of the root hairs of plants. In structure, however, a villus is much more complicated than is a root hair. Each villus (Fig. 32) when highly magnified, is found to contain a network of minute blood vessels, and since they are covered only by a thin layer of cells on the outside of the Fig. 32. — Two villi, highly magnified. ‘DIGESTION AND ABSORPTION OF NUTRIENTS 101 villus, the liquefied food is readily absorbed by the blood current. Within the villi, too, are other thin-walled tubes, called lacteals, which are of great importance in the absorption of fats. As the souplike mass of food is pushed slowly along through the small intestine, it becomes less and less in bulk, and more and more solid, owing to the fact that the dissolved salts, sugars, peptones, and fats are largely taken up by the blood vessels and lacteals within the villi. 141. Absorption in the large intestine. — The amount of absorp- tion in the large intestine is considerably less, of course, for both villi and ridges are wanting. Yet even here considerable absorp- tion takes place. When the mass reaches the lower end of the in- testine, it consists of little but the indigestible cellulose of vegetable foods, some undigested connective tissue, waste substances from the bile, the solids in the mucous secretion, and some raw starch and undigested fats if large quantities of these nutrients have been eaten. This refuse of the food is thrown off from the body. VIII. Tue Liver anp 1Ts FUNCTIONS 142. Position, form, size. — The human liver (Fig. 26) is the larg- est gland of the body, weighing three to four pounds. It lies toward the right side of the body, just beneath the diaphragm, and par- tially covers the pyloric end of the stomach. It consists of several lobes, and on its under surface there is a small, greenish brown sac called the gall bladder. The deep red color of the liver is partly due to the fact that one fourth of all the blood of the body is found within its tissues. 143. Functions of the liver. — The liver performs three important functions. In the first place, it secretes a golden brown liquid called the bile, which is eitlier poured at once through the bile duct into the small intestine or is stored in the gall bladder until needed. If the bile duct becomes stopped up, the bile is absorbed into the blood and gives to the tissues the yellow tint that is characteristic 102 HUMAN BIOLOGY of jaundice. The liver, in the second place, serves as a great store- house for the carbohydrates when the blood does not need them for immediate use. When, on the other hand, there is a lack of carbo- hydrates in the blood, some of the supply in the liver is taken up again by the blood. Finally, the liver helps to destroy some of the worn out cells of the blood (the red corpuscles), and the waste materials thus formed are passed off into the intestine as a part of the bile. IX. Hyeiene or DicEestion 144. Hygienic habits of eating. — One should form the habit of eating slowly and of thoroughly masticating each mouthful of food. For by this process the food is thoroughly broken up, and thus is prepared for rapid digestion not only in the stomach but in the intestines as well. The process of chewing likewise stimulates the flow of saliva. Saliva not only helps digest food in the mouth, but this juice also, when swallowed with the food, continues for a time the di- gestion of starch in the stomach and likewise stimulates to greater activity the glands in the walls of the stomach. At least a half hour should be devoted to the eating of dinner and twenty minutes to breakfast, lunch, or supper. The proper digestion of food depends in no small degree upon one’s mental state; worry and disagreeable topics should, therefore, be forgotten as far as possible while one is eating, and the mealtime should be made a season of enjoyment. Regular hours of eating are of great importance, for nothing more commonly deranges the digestive system than the con- tinual nibbling of food or sweetmeats between meals. One should refrain from vigorous exercise or mental exertion for some time after eating; the reason for this will be clear after a study of the blood system. 145. Prevention of disease. — To insure a state of health the useless residue of the food should be expelled from the DIGESTION AND ABSORPTION OF NUTRIENTS 103 large intestine regularly each day. If this is not done, serious disturbances of the health are sure to follow. By constipation is meant the abnormal retention of waste matter in the intestine. ‘‘ The causes of constipation are imperfect digestion (due to deficient secretion in the alimentary canal, inaction of the liver, or insufficient contraction of the muscu- lar fibers of the intestines), insufficient exercise, the use of alcohol or drugs, or improper food.” 4 Constipation may usually be counteracted by liberal drink- ing of water, especially a half hour before breakfast, and by eating food with laxative effect,—for example, ripe fruits (especially figs), green vegetables (especially salads with oil), and breads made of the coarser graham and rye flours. Dyspepsia, also, is far too common, and is one of the most discouraging diseases to treat, because it shows itself in so many different ways. It is far easier to prevent than to cure, for it is usually caused by rapid or irregular eating, by taking indigestible foods, by lack of proper exercise, or by worry ; and for all of these conditions the individual is, in the main, responsible. The regulation of diet in time of sickness is a most impor- tant aid to recovery. In certain diseases it is necessary that some kinds of food should be forbidden. Whenever the func- tions of the body are not carried on with their accustomed vigor, the physician prescribes foods that are easily digested —for example, milk, raw oysters, toasted bread, and soft- boiled eggs. 146. The use of water as a drink. — ‘“ Many people, and especially many women, drink too little water. Water is constantly being lost through the lungs, skin, or kidneys, and this loss is only partially made good by the oxidation of the 1From New International Encyclopedia. 104 HUMAN BIOLOGY hydrogen of the proteins and fats. No rules as to the amount can be given, since it varies so much with temperature and the amount of muscular activity ; but the habit of drinking no water between meals and but little at the table, in spite of popular opinion on the subject, is to be deprecated. . . . “Undue emphasis has been laid upon the danger of drink- ing water with meals. The reasons given — that such water unduly dilutes the gastric juice or takes the place of a normal secretion of saliva — are questionable. As a matter of fact, the water thus taken is soon discharged into the intestine and absorbed. It is true, however, that the use of too much fluid with the meals is apt to lead to insufficient mastication because it makes it easier to swallow the food; and from this point of view caution is advisable. It is probably also true that much drinking with meals tends to overeating, by facilitating rapid eating.””— HoucH and SEpGwIck’s “Human Mechanism.” 147. Effects of alcoholic drinks on the organs of diges- tion. — Alcohol, unlike most of the substances taken into the alimentary canal, requires no digestion. It can, there- fore, be absorbed very rapidly by the blood, and hence alcohol is possibly sometimes of great value when administered by physicians, in cases when ordinary food cannot.be digested. In health, however; alcoholic drinks must be regarded as an expensive and extremely dangerous source of energy. According to the best authorities, small quantities of alcohol (when sufficiently diluted) seem for an adult to stimulate an increased flow of saliva and gastric juice, but even this is doubtful. The time required for the digestion of food, when alcohol is present in these small quantities, does not seem to be increased. Entirely different effects follow, however, when strong distilled liquors are taken, DIGESTION AND ABSORPTION OF NUTRIENTS 105 and alcohol in any large quantity often produces serious‘ disturbances of the organs of digestion. This is especially true when liquors are taken without food; that is, between meals. The constant danger that the moderate use of beer and the light wines will lead to an uncontrollable thirst for alcohol cannot be emphasized too strongly. All authorities agree, too, that the growing youth should let alcohol entirely alone. 148. Review of Digestion ReGion oF ALIMEN- Kinp or SECRETION . TARY CANAL PRESENT Processes CARRIED ON Mouth cavity. | Saliva and Mastication of food. mucus Starch changed to sugar. Sugar and salt dissolved. Tasting of food sub- stances. Small amount of absorp- tion of water, salt, sugar. Throat cavity. | Mucus. Passage of food and air: Gullet. Mucus. Passage of food to the stomach. 106 HUMAN BIOLOGY ReEGion oF ALIMEN- TARY CANAL Kinp oF SecrETION PRESENT PrRocEssES CARRIED ON Stomach. Gastric juice, consisting of water, pep- sin, and hy- drochloric acid, and mucus. Churning of food by the muscles. Digestion of starch (by saliva, for short time). Proteins changed to pep- tones. Insoluble salts changed to soluble. Small amount of absorp- tion of water, salts, sugars, peptones. Small intes- tine. Pancreatic juice, bile, intestinal juices and mucus. Fats changed to a liquid form ready for absorp- tion. Starch changed to sugar. Proteins changed to peptones. Large amount of ab- sorption of fats by lacteals of villi. Large amount of ab- sorption of water, salt, sugar, peptones, by blood vessels of villi. Large intes- tine. Mucus, and in- testinal juices Small amount of ab- sorption of nutrients. Removal of refuse of food from the body. CHAPTER VI CIRCULATION OF THE NUTRIENTS I. ComposITION OF THE BLOOD 149. Food and blood.— Thus far in our laboratory studies we have tested various foods, and have found that they all consist of one or more of the nutrients; namely, proteins, fats, carbohydrates (i.e. starch and sugar), fats, mineral matters, and water. We have discussed the way in which each of these nutrients is digested, and thus made ready for absorption into the blood — for until the nutrients actually become a part of blood, they cannot be of use to the body. In 7 we described the red and white corpuscles of the blood! (Fig. 5) and there stated that the liquid part of blood is known as blood plasma. 150. Composition of blood plasma. — Blood plasma con- tains a large amount of water in which are dissolved the various nutrients obtained by absorption from the alimentary canal. The presence of each of these nutrients has been demonstrated by applying the various food tests given in 23-28, “Plant Biology.” Following is the percentage of each nutrient found in the human body :— Water. . . . . . ww ee) 907 per cent Proteins . . . . . . . 8* per cent Fats, grape sugar, mineral esther . . . . 27 per cent 1For a laboratory study of blood, see ed s ‘‘ Laboratory Exercises,”’ pp. 50-53. 107 ‘108 HUMAN BIOLOGY 151. Hygiene of the plasma. — All the nutrition of the tissues is derived from the blood, and all the nutrients of the blood come from the foods we eat. If these foods are in- sufficient or of an improper kind, the blood will, of course, be deprived of necessary ingredients, and the cells must inevitably suffer in consequence. Hunger and thirst are the sensations that tell us that the blood is in need of new material. That this is true is demonstrated by the fact that these sensations disappear when water and liquid food, in- stead of being swallowed, are injected directly through the skin into the blood vessels. 152. Blood clotting. — When blood escapes from the body, it is a liquid of a bright red color. It soon changes to a dark maroon, however, and later this thickens to the consistency of jelly. This dark red mass is called a blood clot, and the process is known as clotting or coagulation. Coagulation is of great practical importance, since it provides a natural means of closing injured blood vessels, and of preventing loss of blood. II. CrrcuLation AND ITS ORGANS 153. Necessity for the circulation. — From our study thus far, we have found that our bodies are composed of complex chemical compounds that are constantly being consumed in the development of heat and other forms of energy. It is evident, then,.that every organ of the body, and indeed every living cell, must be supplied with new material to make good these losses and to provide for growth. The source of all this material is the food we eat. In the last chapter we considered some of the processes by which foods are converted into liquid form and made ready for use in the cells. We found that after being liquefied these CIRCULATION OF THE NUTRIENTS 109 nutrients are absorbed by the blood vessels in the walls of the alimentary canal. Since, however, many tissues of the body are at a considerable distance from the organs of di- gestion, it is evident that some means must be provided for supplying each cell with the nutrients it needs. This is effected by the circulation of the blood. By the term cir- culation of the blood 1s meant the ceaseless movement of the blood through a system of tubes called blood vessels. 154. Organs of circulation. — As is also true in the fish and other vertebrates, the force that drives the blood around through the body is largely furnished by the contraction of the muscular walls of the heart. Any blood vessel that carries blood away from the heart is called an artery. The veins are the blood vessels that bring the blood back to the heart. Connecting the arteries and the veins in every part of the body are countless microscopic blood vessels called capillaries (Latin, capillus = hair, so called from their mi- nute size). We shall now consider in more detail the struc- ture and action of each of these circulatory organs. III. Tue Heart 155. Position, size, shape.— The heart (Fig. 2) is a conical or pear-shaped organ about the sizeof the fist. It lies behind the breastbone near the middle of the chest cavity, with its pointed end or apex extending toward the left side between the fifth and sixth ribs. Since the beat of the heart is felt most plainly near the apex, it is commonly but wrongly believed that the heart lies on the left side of the body. Let one imagine the front wall of the chest ‘From Greek, aer = air + terein = to hold — a name which was given by the early anatomists to these tubes, because they were found empty after death, and were therefore supposed to carry air. 110 HUMAN BIOLOGY cavity to be removed; one would then see the soft, pink lungs on either side, nearly filling the chest cavity, and between them the heart ! (Fig. 2). 156. Chambers of the heart. — We have seen (A. B., 99) that a fish’s heart has two chambers, an auricle to receive the blood from all parts of the body, and a muscular ventricle to force the blood into the arteries which carry it to the organs of respiration (gills) and thence by another system of arteries to all parts of the fish’s body. In the human circulatory system, the blood, after returning to the heart from the organs of the body, is likewise forced through an auricle, a ventricle, and arteries, and so reaches the breathing organs (lungs). Unlike the circulation in the fish, however, the blood does not pass from the breathing organs to the other parts of the body directly, but returns by veins to the heart, and so an- other auricle and ventricle are provided on the left side of the heart. These receive the blood from the organs of respiration, and force it to all parts of the body. Thus we see that we have two hearts, the chambers of which are completely separated by a muscular partition; the right heart receiving the blood from all over the body and pump- . ing it to the lungs; the left heart receiving the blood from the lungs and pumping it over all the body. A comparison of these four chambers shows important differences. In the first place, the auricles have relatively thin walls as compared with the ventricles, and the reason for this is evident when we see that their function is simply to receive the blood from the veins and to push it downward into the ventricles. When one compares the walls of the 1 The heart is not only surrounded by the skeleton and muscles of the chest wall, but it is also inclosed in a tough bag of connective tissue called the pericardium (Greek, peri = around + cardia = heart). CIRCULATION OF THE NUTRIENTS 111 left ventricle with those of the right, one is struck with the great thickness of the former. The left ventricle does much more work than the right; it forces blood to the top of the head, to the tips of the fingers and toes, and to every other organ of the body. The right ventricle, on the other hand, pumps blood only to the lungs (Fig. 33). ONARY ARTERY PULMONARY). if ILUNAR (ALVES SEMILUNAR A= right heart. B = left heart, Fig. 33.— Cavities of heart. 157. Action of the heart. — The blood flows into the right and left auricles and thence into the corresponding ventricles. When the ventricles are nearly full of blood, the two auricles contract and force downward enough blood to fill the two ventricles completely. These muscular chambers then con- tract and force the blood out into the arteries that lead to the lungs, or to other parts of the body. When the con- traction of the ventricles takes place, it is evident that blood would be driven back into the auricles were there not some means of preventing this back flow. Hence, between each 112 HUMAN BIOLOGY auricle and ventricle tough flaps of membrane are provided which close the opening while the ventricles are contracting. Connected with each of these flaps are tough cords of tissue that are attached to the muscular walls of the ventricle. These cords prevent the valves from being forced up into the ef A = positions of valves before B= position of valves at the the contraction of the ven- beginning of the contrac- tricle. tion of the ventricle. Fic. 34.— Diagrams to show the action of the valves of the heart. auricle (Fig. 34). When the ventricles cease to contract, the blood entering the auricles presses these valves downward and so enters the ventricles. IV. THe Bioop VESSELS 158. Position of arteries and the pulse.— We have de- fined an artery as a blood vessel carrying blood from the heart. Every time the ventricles contract, the arteries leading from them are expanded, and this is true of every artery in the body. Most arteries lie beneath thick layers of muscle or bone, which protect them from possible injury.; but in certain regions of the body they lie close to the sur- face. If one places the fingers on the ‘wrist two inches or _tmore below the ball of the thumb, it is possible to feel a CIRCULATION OF THE NUTRIENTS 113 distinct throbbing, called the pulse. This is due to the enlargement of the artery at each heart beat followed by subsequent contraction. When an artery is cut, therefore, the blood is forced out in spurts at each contraction of the ventricle. 159. Structure of arteries. — If a piece of the aorta of any animal is examined, it will be found that the blood vessel retains its tubular form, and this is due to the presence cellsof lining /2 ZY, membrane //: | membrane muscle muscle ~"" 7 nee and elastic and elastic tissue tissue A = artery. B=vein. Fie. 35. —Cross section of blood vessels. of thick layers of muscular and elastic tissue (Fig. 35). It is the elastic tissue that allows the arteries to expand when more blood is forced into them by the contraction of the ventricles. After each pulse these elastic walls squeeze the blood forward into the capillaries; arteries, therefore, are specially adapted to keep the capillaries full of blood. The muscular tissue in the walls of the arteries aids in regulating the size of the arteries, and so determines the rel- ative amount of blood supplied to any given organ. For example, when the face is flushed, the muscles in the arteries have relaxed; pallor, on the other hand, is due to the con- traction of the muscular walls. I 114 HUMAN BIOLOGY 160. Astudy of the pulse. — Laboratory and home study. A. To take the pulse. (Laboratory study.) 1. Place the fingers on the wrist as directed in 158, and count the pulse while sitting quietly for a minute, being careful not to miss any of the beats. Repeat the count several times, until the numbers approximately agree. Describe what you have done, and record your pulse rate in your note- book. 2. (Optional.) Ina table like the following record the number of pupils with a pulse rate (while sitting still) correspond- ing to the headings of the various columns named below 40-49 | 50-59 | 60-69 | 70-79 | 80-89 | 90-99 | 100+ B. To determine the effect on the pulse rate of different posi- tions of the body. (Home work). 1. Lie a few moments on a couch and completely relax the muscles. Count and record your pulse, re- peating the count till the number during a minute is reasonably constant. (It is better, if possible, to have some one else do the counting.) 2. In a similar way, make a record of your pulse while sitting. 3. Determine, likewise, the pulse rate when you are standing. 4. Take some vigorous exercise for a few moments (eg. running upstairs or riding a bicycle)... Now de- termine your pulse rate. 5. What do you conclude, therefore, as to the effect on the heart beat of vigorous muscular activity? In what ways may the rate of the heart beat be de- creased ? 161. Valves at the mouth of arteries. — The arteries are always full of blood, and when the ventricles contract, these 1 In case the pupil has any heart difficulty, a milder form of exer- cise, such as walking rapidly or swinging the arms, should be taken. CIRCULATION OF THE NUTRIENTS 115 blood vessels have.to be stretched in order to accommodate the additional blood that is forced into them. Hence, when the ventricles begin to relax, the blood tends to rush back into these chambers from the arteries. To prevent this, valves are placed at the opening of each of the two arteries that lead from the right and left hearts (Fig. 33). Each valve is shaped like a watch pocket. The three open outward from the heart, but as soon as the ventricles begin to relax, the blood fills up the pockets, and the three valves, by meeting in the middle of each artery, keep the blood from returning to the ventricles (Fig. 33, A). 162. Position of the capillaries. — As we trace the arteries farther and farther from the heart, we see that they divide and subdivide until very small branches are formed. That these fine branches are still arteries is proved by the fact that elastic and muscular tissues are present in their walls. Finally, however, these tiny blood vessels become continuous with still smaller tubes, the capillaries. So numerous are the capillaries that one cannot push the point of a needle for any considerable distance into any organ of the body without piercing a number of them. These smallest of blood vessels communicate freely with one another and form a complicated network of tubes that bring blood close to all cells of the body. 163. Importance of the capillaries.—-If the blood were kept constantly within a system of tubes like the arteries, it would be entirely unable to help in the nutrition of the body because osmosis would be impossible. Each cell of the body must take from the blood the nutrients it needs for its special work; likewise it must give off to the blood the wastes it has formed by oxidation. It is through the thin-walled capillaries that all these exchanges of materials 116 occur. portion of the blood system. HUMAN BIOLOGY Hence, the capillaries form the most important 164. Structure of the capillaries. — In structure the capil- laries are extremely simple (Fig. 36). nucleus : of cell A=Surface view. B=Longitudinal section. Fic. 36.—Structure of capillaries. At the points in the blood system where arteries end and capillaries begin, muscular and elastic tissues are wanting. The walls of the capillaries are formed of a single layer of very thin- walled cells. We have in this arrangement the best possible conditions for the process of osmosis. Only the thin membrane of the capillary wall separates the blood from the surrounding tissues, and an exchange of materials between the two is readily carried on. 165. Position of the veins. —~ On the back of the hand one sees through the skin a branch- ing system of bluish blood ves- sels. These are veins. Unlike the arteries, veins have no pulse. Many veins, like those in the hand, lie near the sur- face, while most of the arteries, as we have stated above, are buried deeply among the other tissues. | | A B Cc Fie. 37.— Structure of a vein. A=vein laid open to show shape of valves; B =section of vein showing valve open; C'=section of vein showing valve closing. 166. Structure of veins. — When the veins are emptied of blood, they immediately collapse. This is due to the fact CIRCULATION OF THE NUTRIENTS 117 that their walls have far less muscular and elastic tissue than have the walls of arteries. Veins, however, are provided with valves shaped much like the valves at the mouth of the large arteries leading from the heart. The blood can flow toward the heart, but as soon as it begins to pass in the opposite direction, these valves are immediately filled and thus the passage is obstructed (Fig. 37). V. CIRCULATION OF THE BLooD 167. Course of the blood through the body. — Having completed our survey of the structure and action of the heart and the blood vessels, we are ready to study the blood system as a whole and to learn how the blood goes to, through, and from, the organs of the body. Let us now follow the course of the blood from the time it leaves the left ventricle until it again returns to this chamber of the heart. When the left ventricle contracts, the blood is forced out into the largest artery of the body, which is known as the aorta. This blood vessel forms an arch (Fig. 38) from the upper portion of which branches extend to the head and the arms. The aorta then continues downward through the chest and abdominal cavities, supplying on its way the various organs in these regions. It then divides into two arteries that continue down the legs. Each of these larger arteries that we have men- tioned divides again and again, until finally the blood is forced through a network of very fine capillaries in the various organs to which the arteries extend. From these capillaries blood passes into tiny veins which carry all the blood into two large veins, one from the upper part of the body, the other from the lower part of the body ; and these two veins finally empty into the right auricle of the heart. Thence the blood passes into the right ventricle. 118 HUMAN BIOLOGY _ bens frombhead ; we Biteries lohead Ath Of | aorta ‘ Superior vena Cara ™. ee Leln from arm Aightauritle_ > ze Fleht venti le... Artery toarm ee ro @-.-... | }---7horacic aorta iia aeatey --- Stomach Litertor vena cava-tfit [X. Ke ®&e PN MI -- branch of, = re. fo i | fANCSEES, AN INVEr veins rrom.----- y ; WES “--Soleen = pli Dees ste ---Winar arter, bla Biines \ : y pair: ~~ Branches of aorta Branches, of" ‘Goh : aorta to legs HF Fie. 38.— Diagram of the circulation to and from the various organs of the. body except the lungs. ; CIRCULATION OF THE NUTRIENTS 119 The right ventricle by its contraction drives the blood through an artery to each of the lungs, until it finally reaches the countless capillaries in the interior of these organs. Veins now receive this blood and convey it to the left auricle, whence it-again enters the left ventricle. About one half minute is required to complete the circulation. , 168. Changes in the composition of the blood. — The composition of the blood is continually changing in its pas- sage through the various tissues of the body. We may, perhaps, make clearer these various changes by expressing them in tabular form as follows : — =r Bioop Loses Buioop Gains In muscles, nerves, | Materials needed | Wastes formed by and other for growth, re- | oxidation (carbon tissues. pair, and produc- | dixoid, water, tion of energy. and other wastes). In lining of mouth, | Materials needed | Digested nutrients. stomach, for the manufac- intestines. ture of digestive juices and for growth and re- pair. In lungs. Carbon dioxid and | Oxygen. water. In kidneys and | Water and other | Carbon dioxid. skin. wastes. VI. HyGiENe oF THE CIRCULATION 169. Effect of exercise on the heart. — The pulse rate is slowest when we are asleep. As the activities of the day begin, the heart beat is quickened, and after violent exercise 120 HUMAN BIOLOGY this organ may beat as often as twice a second. Exercise, when properly regulated, is undoubtedly beneficial to every organ of the body, for the heart should be kept in such a vigorous condition that it is ready to meet not only the ordi- nary requirements of everyday life, but even the strain that may come in such emergencies as necessary escape from danger or recovery from disease. It is easily possible, however, to overstrain the heart. muscle by exacting from this organ too violent or too pro- longed activity (e.g. in sprinting or in long distance runs and bicycle rides). These often result in permanent thickening of the walls of the valves of the heart. Before a youth takes part in athletic contests, he should consult a competent physician as to the wisdom of his taking violent exercise. 170. Effect of exercise on the blood vessels. — When one is using the muscles actively, greater oxidation of the tissues goes on, and a larger amount of blood is needed to supply the oxygen and to remove the added wastes formed by this increased oxidation. The muscular walls of the arteries relax in the organs that are specially active, thus supplying these organs with more blood. It is manifestly impossible to have an increased supply of blood in the organs of digestion, in the muscles, and in the brain all at the same time. This is the reason why it is unhygienic for an adult to exercise violently or to carry on any considerable degree of mental activity immediately after a hearty meal. Per- sistence in violating this rule usually results in attacks of indigestion. 171. Stopping of blood flow in wounds. — One can tell when an artery has been cut by the fact that blood comes out in spurts. Since the blood is on its way from the heart, the flow can be stopped or lessened in this kind of accident “ \ CIRCULATION OF THE NUTRIENTS 121 by applying pressure on the side of the wound nearest the heart. Thus if the finger is cut deeply and the blood jets forth, a strong cord or a handkerchief should be tied loosely about the wrist, a wad of paper, or a pebble being placed directly beneath the knot and over the artery. A pencil or piece of wood should then be run through the loop, and the knot should be twisted until the blood flow is stopped by the pres- sure. When blood flows evenly from a wound, it is an in- dication that a vein has been cut, and the pressure should be applied in a similar way on the side away from the heart. If unable to decide whether an artery or a vein has been cut, put the bandage directly over the cut.” Bleeding from the nose may usually be stopped by holding the head erect, and by applying cold water to the bridge of the nose or to the back of the neck. 1Every pupil should practice the method of applying a bandage in accordance with the directions given in this section. 2 For further treatment of cuts and bruises see 25. CHAPTER VII RESPIRATION AND THE PRODUCTION OF ENERGY IN MAN I. NecrEssiTy FOR RESPIRATION 172. To prove that oxidation takes place in the human body.! — Laboratory study. A. Development of heat in the human body. Secure two chemical thermometers that approximately agree at the room temperature. Support one of the ther- mometers so that it hangs free in the air; clasp the bulb of the other thermometer in the palm of the hand for several minutes. 1. Describe the experiment as it was performed. 2. Note and record the temperature as indicated on each of the thermometers. 3. What evidence have you that heat is produced in the human body? B. Production of carbon dioxid in the human body. Blow the breath through a tube into a bottle or test tube of lime water. 1. Describe what was done. 2. What proof have you that carbon dioxid is given off from the body? 3. What element found in foods and protoplasm must be oxidized in order to produce carbon dioxid? 1 The student should review P. B., 75 (to prove that heat energy is developed in growing seedlings) and P. B., 81 (to prove that car- bon dioxid is formed during the growth of seedlings). 122 RESPIRATION AND ENERGY IN MAN 123 4. State now two evidences that oxidation is carried on in the human body. 5. What element must always be present in order that oxidation may be carried on? 173. Examples of energy in the human body. — While studying plants, we enumerated various ways in which these living organisms exhibit the energy which is developed within them (P. B., 74), and we have likewise called attention to evidences of energy in animals. In human beings the forms of energy are much more varied and strik- ing. For example, the movements of each of the five hun- dred separate muscles found in the body are all due to the muscular energy developed in their protoplasm; the control of all these muscles is due to energy liberated in the nervous system (nervous energy); all the glands that produce the varied ferments owe their ability to do their work to the release of chemical energy; and when we come to deal with the highest functions, namely, feeling, thinking, and willing, it seems probable that all of them are made possible by the setting free of some form of energy. In connection with the development of all these forms of energy, heat energy, as we proved in 172, is liberated. 174, Transformations of energy. — While considering the functions of green plants we found that the energy of the sun is utilized and stored in the manufacture of food materials, and thus is made available for the use of the plant. Con- sequently, when we take into our bodies and digest the various nutrients produced by green plants, these food substances become available as our sources of energy. But to release this stored-up energy, whether in muscle, gland, or nerve cells, oxygen is always essential. Hence, a constant supply of oxygen for the body is necessary. When this oxygen 124 HUMAN BIOLOGY combines, in the process of oxidation, with the carbon, hydrogen, and other elements in the foods or protoplasm, waste matters (carbon dioxid, water, etc.) are produced, and for the healthy working of the body, these wastes must be eliminated. We are now to see how the body is adapted to secure an adequate supply of oxygen and to rid itself of harmful waste matters. 175. Respiration in plants, animals, and man. —It should be clear from our study thus far that all living things require oxygen, and that this oxygen brings about in plants, animals, and man a process resembling oxidation, at least in the re- leasing of heat and of other forms of energy, and in the pro- duction of carbon dioxid and other waste matters. These various processes doubtless take place in each living cell. Hence, every cell must be supplied with oxygen and must necessarily form carbon dioxid. The process by which plants or animals take in oxygen and get rid of carbon dioxid is known as breathing. And when we include also the oxidation that takes place within the cells and the elimination of the wastes from the cells, this whole series of processes is known as respiration. Breathing involves two distinct processes; first, that of taking into the lungs new supplies of fresh air, and secondly, that of removing from the lungs the impure air that has been used. To the first process is given the name inspiration (Latin, in = into + spirare = to breathe) ; the second is called expiration (Latin, er = out + spirare = to breathe). II. ADAPTATIONS FOR SECURING OXYGEN AND FOR ExcrETING CarRBON D1oxIp 176. Course taken by the air.— In ordinary breathing, air enters the body through the two nostrils (the left one is RESPIRATION AND ENERGY IN MAN 125 shown in Fig. 39), and then through the two nasal passages it enters the throat cavity. In the lower region of the throat is the slit-like glottis opening, through which the air enters the larynx or voice box. The latter, commonly known as “‘Adam’s apple,” projects some- what on the front of the neck. Below the larynx is the contin- uation of the windpipe, which, just above the level of the heart, divides into two main branches (Fig. 40), one of which supplies [/% air to the right lung, the other to the left lung. Within the lungs these tubes branch off into a vast number of very small pipes, called bronchial tubes. The finest divisions of these tubes open into extremely thin-walled air sacs (Fig. 41). 177. The nose cavity. — The openings into the nasal passages are guarded by a mass of pro- jecting hairs, by means of which a considerable amount of dust is kept from entering the lungs. The nose itself is lined by mu- cous membrane which covers the whole interior of the nasal Fie. 39.— Longitudinal section of head and neck showing food and air passages. a = vertebral column. b = gullet. c¢ = windpipe. d= larynx. ‘e = epiglottis. f=uvula. g = opening of left Eustachian tube. h = opening to tear duct. k = tongue. l= hard palate. chambers. Its mucous secretion collects most of the dirt and germs that have passed the hairs in the nostrils. 126 HUMAN BIOLOGY 178. The throat and larynx. — Except when something is being swallowed, the glottis is always open, thus allowing a free passage for the air from the throat, through the larynx, into the wind- pipe. When food is swallowed, it is of course important that the windpipe be closed, and this is accom- plished by a little trap- door called the epiglottis (Fig. 39). If one puts the finger on the larynx region and then swal- . lows, one can feel this organ rising to meet the epiglottis. Within the voice box are two thin membranes that may be stretched with more or less tension and set in vibration by the in- spired or expired air. These vocal cords help to produce the various tones of the voice. Fig. 40.— Windpipe and lungs. 179. Lining of the air passages. —- The mucous lining of the nasal cavities and of the windpipe and its branches is especially interesting. The cells that cover these Fic.41.—Two air sacs passageways are covered by minute hair- With their branches. like projections called cilia, much like those on the outside of a paramecium (A. B., 120), which wave upward toward RESPIRATION AND ENERGY IN MAN 127 the throat with a quick movement, and then more slowly recover their former position (Fig. 18). In this way any dust particles that have passed the barrier of hairs at the nostril openings and the mucus secreted by the membrane are moved steadily upward until they reach a point where they can be coughed out into the mouth cavity. 180. The lungs.1— When the finest branches of the bronchial tubes are traced, we find that each one ends in a branching air sac with extremely thin walls of elastic tissue (Fig. 41). When air comes into these sacs, they are expanded; but as expiration begins, their elastic walls help to force back through the branches of the windpipe the air that has been taken into the lungs. F 181. Blood supply to the lungs. — The artery supplying the lungs, as we learned (167), arises from the right ventricle and soon divides into two branches, one for the right and one for the left lung. Within the lung tissue each artery divides into small branches that follow the course of the bronchial tubes to the air sacs. Here the arteries com- municate with a maze of capillaries that run just beneath the thin lining of the air sacs. It is here that the exchange of material takes place between the blood and the inhaled air, for the two are separated only by the extremely thin 1QOne can get a good idea of the structure of the human air passages and lungs by securing from the butcher the chest organs of a sheep or calf. These consist of the larynx, windpipe, and its branches, and the two lungs, between which lies the heart.