New Park State College of Agriculture At Gornell University Dthaca, N. Y. Library ornell University Libra ric 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/cu31924002836710 BY THE SAME AUTHOR Elementary Zoology Pp. xv + 492, 172 figs., 12mo, 1901, $1.35. First Lessons in Zoology Pp. x + 363, 257 figs., 12mo, 1903, $1.12. American Insects Pp. vii + 671, 812 figs., 11 colored plates, 8vo, 1905 (American Nature Series, Group I), $5.00. Students’ edition, $4.00. Darwinism To-Day Pp. xii ++ 403, 8vo, 1907, $2.00. Insect Stories Pp. vi + 298, illustrated, 12mo, 1908 (A meri- can Nature Series, Group V), $1.50. Henry Hott anp Company PuBLisHeRs New York (‘sesuey jo Apsioatun ‘ayokq “yy “I “Jord Aq payunow suawisads wor st “gq 4q ydeiZojoyq) “Buno< pur ‘oyeutoy ‘ayeur Surpnyout ‘(woszq woszg) uosiq 10 oyeYN uvIIIaUTY JO dnoiy THE ANIMALS AND MAN AN ELEMENTARY TEXTBOOK OF ZOOLOGY AND HUMAN PHYSIOLOGY BY VERNON LYMAN KELLOGG PROFESSOR IN STANFORD UNIVERSITY WA Ua ® Us rath) VEX o i asi Sr P =: ¥ a Wy NEW YORK HENRY HOLT AND COMPANY IQII ¥ Copyricut, 1911, BY HENRY HOLT AND COMPANY PREFATORY NOTE This book is a simple introduction to the study of the structure, physiology, behavior and classification of animals and to the study of the make-up and physiology of the human body. It makes use of some of what have been proved by experience to be the most useful parts—specially revised for this book—of the author’s “Elementary Zoology”’ and “First Lessons in Zoology,” to which have been added new chapters on human structure and physiology and on certain special relations between animals and man. The whole book has been written and arranged from the point of view of a biologist intent on making our knowledge of the make-up and life of the lower animals help in under- standing human structure and physiology and in contributing to human welfare. I believe that this point of view need not militate in the least against the disciplinary or informational value of a text-book of zoology. I believe, indeed, that it will enhance these values. Chapters XXI to XXVIII, on human structure and physiology, were written by Assistant Professor Isabel McCracken of this University, and to that extent Miss McCracken is joint author of the book. I wish to acknowledge my indebtedness to those numerous zoologists who have accorded me permission to use illustra- tions original with them. The sources of these repeated illustrations are indicated in the captions of the pictures. The drawings for the figures original with me have mostly been made by Miss Mary Wellman and Mr. Sekko Shimada to both of whom I am under obligation for their intelligent and skilful help. V. L. K. STANFORD UNIVERSITY, January, 1911. CONTENTS PART I THE PARTS OF ANIMALS AND HOW THEY ARE USED CHAPTER ia ITI. IV. V. VI. VII. VIII. TX. THE GRASSHOPPER AND THE SNAIL (External Structure) THE SUNFISH AND THE SPARROW (External Structure) THE GARDEN TOAD (BUFO LENTIGINOSUS) (External and Internal Structure) Tue CRAYFISH (CAMBARUS SP.) (External and Internal ; Structure) AMcBA, PARAMECIUM AND VoRTICELLA (Structure and Behavior) ANIMAL PHYSIOLOGY PART II THE LIFE-HISTORY OF ANIMALS MULTIPLICATION AND DEVELOPMENT MosQuiIToES AND CATERPILLARS Frocs AND BIRDS ‘ PART III PAGE 1 8 19 28 37 49 DIFFERENT KINDS OF ANIMALS, THEIR CLASSIFICATION, HABITS AND SPECIAL RELATION TO MAN THE CLASSIFICATION OF ANIMALS THE SIMPLEST, OR ONE-CELLED, ANIMALS (Pror0z0a) Human DISEASES CAUSED BY One- CELLED ANIMALS THE INVERTEBRATES LUSCS y FIGHTING INSECT Pests . THE INVERTEBRATES (continued): ARTHROPODS AND MOoL- 107 118 124 132 149 180 THE VERTEBRATES: FISHES, BATRACHIANS, AND REPTILES 191 THE VERTEBRATES (continued): BirpDs THE VERTEBRATES (continued): MAMMALS DoMESTICATED ANIMALS . Fossiz ANIMALS 214 237 258 275 x CONTENTS PART IV HUMAN STRUCTURE AND PHYSIOLOGY (Chapters XXI-XXVIII by Isabel McCracken) CHAPTER PAGE XXI. INTRODUCTION, AND THE CHEMISTRY OF PHYSIOLOGY 287 XXII. DIGESTION AND ABSORPTION . 303 XXIII. THE Biroop anp CIRCULATION 316 XXIV. THE SKELETON AND MUSCLES 329 XXV. RESPIRATION AND EXCRETION 343, XXVI. NERvous System 357 XXVII. THE SPECIAL SENSES. 368 XXVIII. Micro-oRGANISMS AND SANITATION 379 XXIX. ANCIENT AND MopERN Man 384 PART V ANIMALS IN RELATION TO EACH OTHER, TO PLANTS, AND TO THE OUTSIDE WORLD XXX. THE STRUGGLE To LIvE, ADAPTATION, DISTRIBUTION, ETc. 399 XXXI_. PARASITISM AND DEGENERATION. 411 XXXII. Mutvat Arp AND CoMMUNAL LIFE . 421 XXXIII. Tae Coors AND MARKINGS OF ANIMALS, AND THEIR UsEs 438 XXXIV. INSECTS AND FLOWERS , 450 APPENDICES 1. STUDENT AND CLASSROOM EQUIPMENT AND METHODS . 467 2. REARING ANIMALS AND MAKING COLLECTIONS 469 INDEX : A 483, THE ANIMALS AND MAN The Animals and Man PART I THE PARTS OF ANIMALS AND HOW THEY ARE USED CHAPTER I THE GRASSHOPPER AND THE SNAIL An animal’s body composed of parts.—The body of every animal, even the very simplest ones, is composed of a few or many parts, each part having some special use or thing to do. A dog has its body made up of head, trunk, legs, and tail—the head comprising skull with brain inside, jaws with teeth, tongue, eyes, ears, etc.; the trunk com- prising a host of internal parts, as the backbone, heart, lungs, stomach, intestines, etc., and the legs in turn composed of a series of bones to which are attached muscles, among which run nerves and blood-vessels, the whole being covered with a hairy skin. The study of the parts, external and internal, of an animal is called anatomy, and the study of the uses or functions of the parts is called physiology. In earlier. years anatomy and physiology were studied wholly separately, as they still sometimes are. But we know that the things animals do, and the ways in which they do them, depend upon the parts of the body and upon the special character of these parts. We know also that these parts are specially developed and fitted to do certain things or perform certain functions in special ways. That is, the I THE ANIMALS AND MAN structure of a part and its function or business are close- ly related. A grasshopper’s hind legs are specially long and strong so as to enable the grasshopper to hop; or we may put it differently and say that the grasshopper can hop because its hind legs are specially long and strong. In whichever way we look at this relation between the power of an animal to do something in Leecon 2 Special way and its posses- sts on wild oats, sion of parts specially fitted (Natural size; for doing this something, from life.) Whether it be hopping, or flying, or singing, or breathing under water, it must be kept always plainly in mind that such a close relation does exist. Therefore when we study the make-up of an animal, examining care- fully the various parts of the body, we should always remember that this partic- ular make-up or structure is closely con- nected with the things the animal can do, and the special manner in which it does them. The grasshopper.—Grasshoppers, better called locusts, of some kind can be readily found along roadsides or in fields (fig. 1). Collect several specimens, keeping some alive and dropping the others into the killing-bottle (see p. 472). Examine care- fully a dead specimen. Note that the body THE GRASSHOPPER AND THE SNAIL 3 is made up of rings or segments. In what part of the body are these rings plainest? The legs are attached to the middle part of the body called the-thorax, of which the front part (to which the fore legs are attached) is movable and is covered over by a sort of saddle-shaped hood, while the hinder part is solid and box-like. How many pairs of legs are there? Examine a single leg and make a drawing of it, showing of how many parts it is composed and how each part appears. Of what use are the claws and the little pads on the under surface of the foot? To what part of the body are the wings attached? Note how the narrow thicker fore wings cover and protect the plaited delicate hind wings when the wings are folded. When the locust flies for long dis- tances it rises high into the air, until it finds an air current; then it simply lets its large outspread hind wings act as flat sails to hold it up, thus allowing it to float for many miles. In this way the Rocky Mountain locusts sail or fly some- times a thousand miles; all the way from Wyoming to Kansas. Note the many veins in the wings. What are these for? Draw a front wing and a hind wing. On the head find two large compound eyes (see fig. 2), three very small simple eyes, a pair of many-jointed feelers or antenne, used both for féeling and probably also for smelling, and a set of mouth-parts. consisting of an: upper lip, a pair of hard, blackish-brown jaws or mandibles, a second pair of jaw-like parts called’ maxilla, each made up of several small pieces and a small palpus or feeler, and an under lip bearing two more small palpi. With the mandi- bles the locust bites off, and with the help of the other parts, chews bits of leaves, green stems, etc. The palpi are be- lieved to be organs for feeling and tasting the food. Draw the front of the head, naming the different parts. Note that almost the whole outer surface of the body is covered with a firm,:smooth coat, the chitinized cuiticle, that is, the horny outer layer of the skin. The skin of the’ - ' 4 THE ANIMALS AND MAN neck, however, and that at the bases of the legs and wings is soft. Why is this necessary? Note that the soft skin of the neck is well protected by the projecting saddle-shaped horny piece on the front thoracic body-ring. Another use of the firm cuticle, or exo-skeleton, as it is called, is to afford solid points of attachment for the many muscles of the body, the locust having no bones or any kind of internal skeleton. (In a few places there are processes or continua- antenne auditory organ i J ocellus ‘ head compound eye, i ee | -" pronotum { an ? thorax ON ‘abdomen’ ; Z spiracles tibia” 5 7" tarsal segments Fic. 2. Locust, with external parts named. tions of the exo-skeleton projecting internally and these are sometimes called the endo-skeleton.) That part of the body behind the thorax is called the abdomen. Examine the upper side of the first (nearest the thorax) body-ring of the abdomen, and find two small, nearly circular, thin places looking like little windows. These are the hearing organs, or tympana, of the locust. The sound-waves striking against these thin tightly stretched bits of the body wall, set them into vibration, and these vibrations stimulate a tiny vesicle and nerve-ganglion THE GRASSHOPPER AND THE SNAIL 5 on the inside from which a nerve leads to one of the internal nerve-centers. ‘This is a much simpler kind of ear than we possess, and the locust probably cannot hear nearly as well as we can. Note on each side of each abdominal body-ring (except the last) a tiny blackish spot. These are breathing pores or spiracles which open into a system of internal tubes that carry the air to all parts of the body. The locust does not take in air through nostrils on the head nor through the mouth, but by means of these many lateral openings in the body-wall. There is a spiracle near each tympanum, and one on each side of the thorax near the insertion of the mid- dle legs. At the very tip of the abdomen are several small projecting parts which differ in the male and female. The female has two pairs of strong, curved, pointed pieces called the ovipositor or egg-laying organ. When the locust is ready to lay its eggs, by means of this strong ovipositor it bores a hole in the ground into which the abdomen is pushed and the eggs laid at the bottom. The male locust has a swollen, rounded, abdominal tip, with a few short inconspicuous pieces on the upper surface. Examine now a live locust and see how it uses its legs in walking and hopping; how it moves its jaws sidewise, not up and down as with us; how its antenne keep “feeling” about in front of it when it is walking; how the abdomen keeps up a slight but distinct and regular expanding and contracting. This movement forces air in and out of the body through the spiracles; it is the breathing motion. Make a drawing from lateral view of the whole body of the locust, showing and naming all the parts studied. (A more detailed study of the external structure of the locust can easily be arranged for by reference to Comstock and Kellogg’s ‘‘Ele- ments of Insect Anatomy,” 5th ed.) The pond snail.—Pond snails may be found in almost any pond, and live specimens may be easily kept in the schoolroom. aquarium or simply in bowls or glass jars of 6 THE ANIMALS AND MAN water (fig. 3). They should be fed pieces of lettuce or cabbage leaves. Observe the habits of the snails; how they come to the surface to breathe; how they crawl about; how they eat by rasping off bits of the leaves with the rough, horny tongue; how they protrude from and withdraw into the shell; how the feelers move in and out. Examine a specimen with body extended from the shell, and note that it is not made up of segments or rings, as the locust, but is a soft, un- segmented mass with a firm, muscular, flat- tish disk on its lower side called the foot. How does the snail “walk” by means of this “foot” ? The body is covered by the man- tle, an edge of which may be seen just at the margin of the shell. The soft, flex- ible body and firmer muscular foot can both be withdrawn into the protecting shell. Fic.3. Pond snails ina battery jar aquarium. Find on the head (One-third natural size; from life.) a pair of extensible tentacles, the feelers, with the eyes (dark spots) at their bases. Most other snails and slugs have two pairs of tentacles or horns, the eyes being on the tip of the second pair. Find also the mouth, and examine with a lens the peculiar ribbon-like radula or tongue, which is covered with fine curved teeth. The radula is drawn back and forth across the food. and by it THE GRASSHOPPER AND THE SNAIL 7 small particles of the leaf are rasped off. Leaves which have been fed on will show the rasped or scraped places. Find also, usually just at the surface of the water, when the snail has come up to breathe, a small hole on the right side of the body; this is the breathing pore, and air entering here passes into a small sac-like space, a simple kind of lung. Examine a shell and note the following parts: the aperture at the large end, the apex or pointed end, the lip or outer edge of the aperture, the lines of growth parallel with the lip, the suture or spiral groove on the outside, the spire compris- ing all the whorls or turns, and the columella or inner axis of the spire. Do the whorls of all the shells turn the same way? What is the use of the shell? Make a drawing of the right-hand side of a snail and its shell representing the animal fully extended; name all the parts of the snail and shell. If pond snails cannot be found, garden snails or slugs may be studied. The slug is a snail-like animal without a shell. CHAPTER II THE SUNFISH AND THE SPARROW The two animals whose external structure we have studied are both backboneless or invertebrate animals. Most of the smaller animals are without internal bony skeletons and hence without backbones. This is true of the sponges and sea-anemones, the starfishes, the worms, the crayfishes, crabs and lobsters, the centipedes, and the spiders, as well as of the insects and the snails, slugs, and clams. Con- trasted with these backboneless animals are the backboned ones, or vertebrates, including the fishes, amphibians, rep- tiles, birds, and mammals or quadrupeds. We shall now examine the external structure of two backboned animals, a fish and a bird. The sunfish (fig. 4).—Some kind of sunfish can be found in the streams of any part of the United States, except in Washington and Oregon, and in the higher Rocky Moun- tains. Where sunfishes cannot be obtained, bass or perch or gold-fish may be used for study. Specimens should be taken alive if possible, and kept in a large jar or tub of fresh water. Examine a live sunfish. Note the deep, flattened trunk of the body, and the paddle-like tail. The head is closely fitted to the trunk without any neck. How are the scales arranged? Remove a scale and examine it under a hand lens. What sort of an edge has it? Examine the fin, called the dorsal fin, on the back. Note that its front part is com- posed of spines, and its posterior part of soft rays jointed and branched, both spines and rays being connected by and supporting a thin skin. At the end of the tail is the caudal 8 ‘y ‘OIg ‘ds syomodng ‘ysyuns y (azis [eanjeu jyey-3u0) 10 THE ANIMALS AND MAN fin; in front of the tail on the under surface is the anal fin, while still in front of this is the pair of ventral fins, and on the sides of the body back of the mouth are the pectoral fins. How is each of these fins composed? The ventral fins cor- respond to the hind legs of other backboned animals, while the pectoral fins correspond to the forelegs, wings, or arms. Watch the fish swim and determine the use of each kind of fin. Professor Needham gives the following directions for doing this: ‘To learn the use of the pectoral and ventral fins catch the fish with the hand, avoiding the sharp spines at the front of the pectoral and anterior dorsal fins; fold the pectoral fins backwards, flat against the sides of the hody; pass a rubber band back over the head and around these fins to keep them so. Keep the fish under water while at- tempting to depress the pectoral spines, for in air it will keep them rigidly erect. Pass another rubber band about the ventral fins. Then liberate the fish and watch it. What position does its body assume? Release the paired fins and fasten down the dorsal and anal fins with rubber bands. Liberate the fish again, and observe how it gets along with- out the use of these fins. What kind of a course does it take through the water?” Examine the eyes. Are there eyelids? In front of the eyes are two pairs of nostrils. Examine the inside of the mouth. Is there a tongue? Where are the teeth situated, and in what direction do they point? What advantage to the fish is it to have the teeth pointing as they do? Lift up the flap, called opercular flap, in front of one of the pectoral fins and bend it forward. Under it are four gill arches, each with a double fringe of gills. The cavities enclosed by the gills are called gill-pouches. Note the gill- rakers, short and blunt, on the first gill arch. Note also, on the under side of the flaps turned back, delicate red gill-like structures covered by a membrane. These are the false gills. The true gills are organs by means of which the fish THE SUNFISH AND THE SPARROW II breathes under water. Note the fish continually gulping water. This water with air dissolved in it passes through the mouth into the gill-pouches and out under the operculum. Thus the dissolved air in the water comes in contact with the gills, passes through the delicate gill membranes and into the blood, which runs in many fine capillaries through the gills, while at the same time the blood itself gives up carbon dioxide, which passes out through the gill membranes into the water. In this way the blood is purified. Make a drawing from lateral view of the sunfish, showing and naming the parts studied. Professor Needham gives the following directions for seeing the flow or circulation of the blood in the caudal fin of a fish: “Wrap the fish in a wet towel, leaving the caudal fin exposed, and place it on a low box beside the microscope, with-its caudal fin extending across the center of the micro- scope stage. Spread the fin out flat on a glass slip upon the stage, so as to bring a thin portion of it into the field, and examine it with low power. If the fish refuses to lie quietly, pour a little chloroform on the towel near its mouth. “Observe the conspicuous, dark, irregular pigment cells scattered throughout the epidermis of the fin. “The larger blood-vessels are of two kinds: (z) arteries, bringing blood out into the fin, and (2) veins, conveying the blood back to the body again. The smaller ones are the capillaries connecting the arteries with the veins, and dis- tributing the blood throughout the tissues of the fin. “Observe that the blood consists of a fluid plasma, in which float numerous corpuscles. Observe that the blood appears red in the arteries and veins, where the corpuscles are accumulated, but only slightly reddish or yellowish in the capillaries, where the corpuscles form but a thin layer. “Does the blood travel faster in the arteries and veins, or in the capillaries? 12 THE ANIMALS AND MAN “Place a bit of cover-glass over a very thin portion of the fin and study it with higher power. Find two kinds of corpuscles in the blood: (z) red corpuscles (red only when a number are seen together), very numerous, and carried along in the center of the larger currents closely packed together; and (2) white corpuscles, . . . not very numerous, and usually seen trailing along the edges of the blood currents, or escaping out into the tissues.” Sunfishes eat insects, shellfish, spawn of other fishes, but not other fishes themselves. The females lay their eggs in shallow saucer-like depres- sions on the stream bed, which are scooped out and cleared of pebbles by the males. After laying her eggs the female departs, leaving the nest to the exclusive care of the male. The males are very active and pugnacious, defending the nest with great bravery. This attention lasts, however, only until the eggs hatch, which happens in a week or more, depending on the temperature. The young fry are left to care for themselves. The English sparrow (fig: 5).—As the English sparrows, which have spread over the whole country, are almost universally held to be pests, the shooting of a few to serve as specimens for the study of the external parts of a bird may be looked on more leniently than the killing of other birds should be. The habits of the live birds may be studied as the pupils go and come from school or in the school yard. Examine a dead specimen. Note the division of the body into head, trunk, and appendages—namely, wings and legs. Note that the sparrow is covered with feathers, some long, some short, in some places thick and in others thin, but all fitting together to form a complete covering for the body. Only the bill and feet are exposed, and these are covered in one case (bill) with a horny sheath, and in the other (feet) with horny scales. The feathers THE SUNFISH AND THE SPARROW 13 Mh | Aw AY he a) Fic. 5. English sparrows; note the black cheeks and throat which dis- tinguish the males. (One-half natural size; from life.) 14 THE ANIMALS AND MAN and the horny covering of bill and feet are simply modified portions of the skin. Of what uses are the feathers to the bird? The feathers are of several kinds or types, each of which has a name. In the wings and tail are long, stiff feathers called quill feathers; those which overlie the whole body and bear the color pattern are called contour feathers; the small soft ones which cover the body more or less com- pletely (being, however, mostly hidden by the contour feathers) are called down feathers or plumules, while, finally, the scattered, slender, soft, or stiff hair-like ones, with thin bare stem and small terminal tuft of branches, are called thread feathers or filoplumes. Pull a quill feather from the wing and examine it in detail. Note the central stem or shaft, composed of two parts, a basal hollow trans- parent quill, which bears no web and by which the feath- er is inserted in the skin, and Fic. 6. Bit of bird’s feather, great- a longer terminal four-sided ly magnified; s, shaft; b, barb; part, the rachis, which bears bl, barbule; , hamule. on either side a web or vane. Examine the vane with a lens and see that it is composed of many narrow linear plates called barbs, and that each barb is fringed in turn with smaller branches called barbules. Finally, each barbule bears many fine barbicels or hamules, which can be seen with a micro- scope. The barbs comprising the vanes are interlocked with each other (fig. 6), thus forming a true web and giving the vanes, composed of small, weak parts, much strength and power of resistance. Rub the feathers from tip to base, THE SUNFISH AND THE SPARROW © 35 and, examining the vanes with the lens, find out what has happened; now rub from base to tip, and note, under a lens, the result. Examine a plucked-out contour feather. How does it differ from the quill feather? Can you understand its structure from your study of the quill feather? Note that the tip of the feather is colored and marked while the base is not especially patterned. Why is this? Examine a down feather. How does it differ in make-up from a quill feather ? From a contour feather? What is the special use of the down feathers? Finally, pluck out one of the hair-like thread feathers from the base of the bill and examine it with the lens to determine its structure. Make a careful drawing of each of the four kinds of feathers, naming all the parts. In classifying birds reference is made in the manuals of classification to differences in the shape and character of many parts of the body and to differences in the plumage of various body-regions. To understand these references it is necessary to become acquainted with the names applied to these various small parts and regions, and so in fig. 7 the names of them are given. Examine the bill or beak. It is composed of an upper and a lower mandible or jaw; the meeting line of the man- dibles is called the commissure, and the corner of the mouth is called the rictus; the bristles at the rictus are the rictal bristles; the median ridge of the upper mandible is the culmen, and the median keel of the lower mandible the gonys. Note just above the bill two openings. What are they? How are they connected with the mouth? Note the eyes, and at the inner angle of each the delicate nictitat- ing membrane, which can be drawn over the ball. Does the bird have external ears? The names of the regions of the head which are commonly referred to in describing its markings will be learned from fig. 7. THE ANIMALS AND MAN 16 aIqipuDut wamoT agpunu soda’ ee } Se pvayaloy / / uamnga’ (xn110H) Fic. 7. Outline of bird’s body, with names of external parts and regions. THE SUNFISH AND THE SPARROW 17 Examine a wing; determine by reference to fig. 7 what feathers compose the primaries, secondaries, tertiaries, greater, middle, and lesser coverts.. How many primaries are there? How many secondaries? At the bend of the wing and lying partly over the upper greater coverts is a tuft of short quills, the spurious quills; underneath the wing at its junction with the body are some long, narrow feathers, the axillars. Spread the wing out and note where the quill feathers are inserted. Note how perfectly the feathers fit together and overlap, both when the wing is outspread and when folded. The wing corresponds to our arm and hand, the primaries being inserted on the hand (in the bird there is only one large finger, two very small ones not showing except in the skeleton), the secondaries on the forearm and the tertiaries on the upper arm. With what part of the fish does the wing of the bird correspond? If a cleaned and mounted skeleton of a bird can be had for examination the bones of the wing should be studied and drawn. The names of the various regions of the trunk can be learned by reference to fig. 7. How many rectrices or tail feathers are there? What.is the use of the tail? Note the oil gland above the base of the tail. What is the use of the oil? How is it put on the feathers? Observe this in a chicken. — Examine a leg. It is composed of thigh, shank, and foot, the foot comprising the long slender tarsus and four toes with claws. What parts of the leg are feathered? Note the covering on the unfeathered parts. What are the toes well fitted for? There is much variety in the shape and character of birds’ legs, including differences in the length of the various parts, in the covering, in the number and position of the toes, and in the size of the claws. All these differences, as well as the many in the shape and character of the bill, are correlated with habits, especially the feeding 18 THE ANIMALS AND MAN habits of the birds, and offer a most interesting subject for study. + The English sparrow was first introduced into the United States in 1850, and since that time has rapidly populated most of the cities and towns of the country. On account of its extreme adaptability to surroundings, its omnivorous food-habits, and its fecundity, it survives where other birds would die out. It also crowds out and has caused the dis- appearance or death of other birds more attractive and more useful. The sparrow annually rears five or six broods of young, laying from six to ten eggs at each sitting. Unmo- lested a single pair would multiply to a most astonishing number. It has, however, many enemies, most common among them perhaps being the “small boy,” but birds and mammals play the chief part in the destruction. The smaller hawks prey upon it, and rats and mice destroy great numbers of its young and of its eggs whenever the nests can be reached. The sparrow is omnivorous, and when driven to it is a loathsome scavenger, though at other times its tastes are for dainty fruits. Its senses of perception are of the keenest; it can determine friend or foe at long range. The nesting habits are simple, the nests being roughly made of any sort of twigs and stems mixed with hair and feathers and placed in cornices or trees. A maple- tree in a small Missouri town contained at one time thirty- seven of these nests. CHAPTER III* THE GARDEN TOAD (Bufo lentiginosus) TECHNICAL Note.—Although this description is written for the toad it will fit for the dissection of the frog. It will be found, after casting aside a few ungrounded prejudices, that the toad is the better for class dissection. Toads are best collected about dusk, when they can be picked up in almost any garden in town or in the country. Dur- ing the spring many can be found in the ponds where they are breeding. To kill the toad place it in an air-tight vessel with a piece of cotton or cloth saturated in chloroform or ether. When the toad is dead, wash off the specimen and put in a dissecting-pan for study. Several speci- mens should be placed in a nitric acid solution for a day or so (for directions for preparing, see p. 25) to be used later for the study of the nervous system. Also several specimens should be injected for the better study of the circulatory system. With an injecting mass made as directed in Appendix I, introduce through a small canula info the ventricle of the heart. This will inject the arterial system, and with increased pressure the injecting mass may be forced through the valves of the heart, thus passing into the auricles and throughout the venous system. After injecting use the specimen fresh or after it has been preserved in 4% formalin. External structure.—Note that the body of the toad is divided into several principal regions or parts, correspond- ing to those of the human body. Indeed, all through the study of the toad’s anatomy a general correspondence of the body-parts and their arrangement with the parts of the human body and their arrangement will be manifest. The toad and ourselves belong to the same great animal branch. *If preferred, or the school is not equipped for dissections by pupils, the teacher may substitute demonstrations of already dissected specimens for the dissections by students called for by this and the following chapter. 19 20 THE ANIMALS AND MAN As you look at the toad note the similarity of the parts on one side to those of the other, as right leg correspond- ing to left leg, right eye to left eye, etc. This arrangement of the body in similar halves among animals is known as bilateral symmetry. As a rule animals which show bilateral symmetry move in a definite direction. The part that moves forward is the anterior end, while the opposite extremity is the posterior end. In most animals we note two other views or aspects; that which is called the “back” and with most animals is, under ordinary conditions, uppermost is called the dorsum or dorsal aspect, while that which lies below is the venter or ventral aspect. When referring to a view from one side we speak of it as a right or left lateral aspect. These terms hold good for most of the animals that we shall study. Note on the head of the toad the wide, transverse mouth. What other openings are on the head? Note the two large eyes, the organs of sight. Just back of each eye find an elliptical, smooth membrane. This is the tympanum of the outer ear, and through this membrane the vibrations produced by sound-waves are transferred to the inner ear, which receives sensations and transmits them to the brain. Open the mouth by drawing down the lower jaw. Note just within the angle of the lower jaw the tongue. How is it attached to the wall of the mouth? On the tongue are a great many fine papille in which is located the sense of taste. It has now been seen that most of the special senses of the toad have their seat in the head. Pass a straw or bris- tle into one of the nostrils. Where does it come out? These internal openings to the nose are the inner nares. Note in the roof of the mouth just posterior to each of the eyeballs an opening. These are the internal openings to the wide Eustachian tubes, which lead to the mouth from the chamber of the ear behind the tympanum. Note far back in the mouth an opening through which food passes. This is the wsophagus or gullet. Note just aa 3 190 unq00 t-te . . : “pee | jourwopqn Spa.9Ud yoowumojs Sia 2 2 4 ~~ uaands jonp aziq | 3 & « : apouuuae re) ; be sada SS & ~sappn}q 1y08 “Ripoq wf : Aas aoe a sg 110M JDULWOpgD waa po)tod ~ ele SNSOLLI}LD SNUOD hia fivuownd eee bun anbuoy ayy fo safosn we yinow~ ‘snsoursijuay ofng ‘peo} uapres oy} JO UOTessIC[ ajosnul sdantun ajosnwm sniuoj4ps, LOWLU SNULAIU2 SNIOIt, uolvwm snusaqur snjoos SS N < snubow sOOrED 5 "sy VlH ura 9 Vl 2LaJWISIUL A. THE GARDEN TOAD ai below this gullet an elevation in which is. a: perpendicular slit, the glottis. This is the upper end of the laryngotracheal chamber, and the flaps within on either side of the slit are ' the vocal cords. Note at the posterior end of the body in the median line an opening. This is the anal opening or anus. Note the general make-up of the toad. How do its arms compare with our own? How do its fore feet (hands) differ from its hind feet? Note that the body is covered by a tough envel- oping membrane, the skin. In the skin are many glands which by their excretion keep it soft and moist. Internal Structure.—Trcunica, Notre.—With a fine pair of scissors. make a longitudinal median cut through the skin of the venter from the anal opening to the angle of the lower jaw. Spread the cut edges apart and pin back in the dissecting-pan. Note the complex system of muscles which govern the movements of the tongue. Observe a number of pairs of muscles overlying the bones which support the arms. These are attached to the pectoral or shoulder-girdle. Note the large sheet of muscles covering the ventral aspect of the toad. These are the abdominal muscles, which consist of two sets, an outer and an inner layer. Note that posteriorly the abdominal muscles are attached to a bone. This is the pubic bone of the pelvic girdle which supports the hind legs. TrecunicAL NotE.—With the scissors cut through the muscles of the body-wall at the pubic bone and pass the points forward to the shoulder-girdle. Separate the bones of the shoulder-girdle and pin out the flaps of skin and muscle to right and left in the dissecting-pan (see fig. 8). Cover the dissection with clear water or weak alcohol. Note two large conspicuous soft brown lobes of tissue. These form the diver, an organ which produces a secretion that assists in the process of digestion. Note just anterior to the liver and extending between its two lobes a pear- shaped organ, the heart... The lower end: or apex. of the 22 THE ANIMALS AND MAN heart, ventricle, undergoes a contraction, forcing blood out into the blood-vessels. This is followed by a relaxation of the apex and a contraction of the basal portion, the auricle. The heart is surrounded by a delicate semi-transparent sac, the pericardium. The pericardium is filled with a watery fluid, body-lymph, which bathes the heart. Note between the lobes of the liver a small bladder-shaped transparent organ of a pinkish color. This is the gall-bladder, a reser- voir for the bile, the secretion from the liver. Separate the lobes of the liver and note, beneath, the long convoluted tube which fills most of the body-cavity. This is part of the alimentary canal. The most anterior portion of the canal, the gullet or esophagus, leads to a large U-shaped enlargement, the stomach. From the lower end of the stomach there extends a long, slender, very much convo- luted tube, the small intestine, which is followed by a much larger one, the large intestine. This large intestine after one or two turns passes directly back into the rectum, which opens at last to the exterior through the anus. Note just ventral to the rectum a large thin-walled membranous sac. This is the urinary bladder which acts as a reservoir for the secretion from the kidneys. Notice a many-branched yellow structure with a glistening appearance, the fat-body (corpus adiposum). Now push liver and intestine to one side and note the pinkish sac-like bodies (perhaps filled with air), the /ungs. The lungs are paired bodies which open into the laryngotracheal chamber. The toad takes air into its mouth through its nostrils, and then forces it, by a kind of swallowing action, through the laryngotracheal chamber into the lungs. Now lift the stomach and note in the loop between its lower end and the small intestine a thin transparent tissue. This is a part of the mesentery, which will be found to sus- pend the whole alimentary canal and its attached organs to the dorsal wall of the body. Note in the loop of the stomach THE GARDEN TOAD 23 in the mesentery an irregular pinkish glandular structure which leads by a small duct into the intestine. This gland is the pancreas, and the duct is the pancreatic duct.’ From it comes a secretion which aids in the digestion of food. Near the upper end of the pancreas note a round nodular structure, generally dark red. This is the spleen, a ductless gland, the use of which is not altogether known. Make a drawing which will show as many of the organs noted as possible. TECHNICAL NoTE.—Pass two pieces of thread under the rectum near the pubic bone. Tie these threads tightly a short distance apart and then cut the rectum in two between the threads. Now carefully lift up the alimentary canal with attached organs (liver, etc.), and cut it off near the region of the heart. How is the heart situated with regard to the lungs? The heart consists of a lower chamber with thick muscular walls, the tip, called the ventricle, and two upper thin-walled chambers, the right and left auricles. Can you make out - these three chambers? ‘The purified blood from the lungs flows into the left auricle, while the venous blood from all over the body laden with its carbon dioxid enters the right auricle. From these two chambers the blood enters the ventricle. Here the pure and impure blood are mixed. From the ventricle the blood enters a large muscular tube on the ventral side of the heart. This is the conus arteriosus, which gives off three branches on each side; the anterior ones, the carotid arteries, supply the head, the next ones, the systemic arteries, or aorte, carry blood to the rest of the body, while the posterior vessels, the pulmonary arteries, go directly to the lungs and there break up into fine vessels (capillaries) where the carbon dioxid is given off and oxygen is taken from the air. From the lungs the blood returns through the pulmonary vein to the left auricle. Meanwhile the blood which has passed through the systemic arteries and body capillaries is collected again into other vessels going back 24 THE ANIMALS AND MAN to the heart; these are the veims, which empty into a large thin-walled reservoir, the simus venosus, which in turn con- nects with the right auricle of the heart. Three large veins enter the sinus venosus, namely, two pre-caval veins at the anterior end, and a single post-caval vein at the posterior end. ‘Trace out the larger arteries and veins from the heart to their division into or origin from the smaller vessels. TecunicaL Note.—Carefully remove the heart together with the lungs. The lungs may be inflated by blowing into them through the laryngotracheal chamber with a quill and tying them tightly, after which they should be left for several days to dry. When perfectly dry, sections may be cut through them in various places with a sharp knife, and by this means a very good idea of the simple lung structure of the lower backboned animals can be obtained. With a sharp knife cut the heart open, beginning at the tip (ventricle) and cutting up through the conus arteriosus and the two auricles. Note the valves in the heart which separate the different compartments. Note on either side of the median line in the dorsal region a pair of reddish glandular bodies, the kidneys. Attached to the kidneys of the male are two white ovoid glandular masses. These are the reproductive organs. From each kidney trace a tube, ureter, posteriorly toward the region of the anus. The kidneys are the principal excretory organs of the body. The blood which flows through the delicate blood-vessels in the kidney gives up there much of its waste products. These pass out through small tubules of the kidneys into the ureters, which carry the wastes toward the anus. Along one side of each kidney may be seen a yellowish glistening mass, the adrenal body. In some of the specimens studied, the body cavity may be filled with thousands of little black spherical bodies. These are undeveloped eggs lying in the female reproductive or- gans situated on each side of the post caval vein. They are deposited by the mother toad in the water in long strings of transparent jelly, which are usually wound around sticks or plant-stems at the bottom of-the pond-near- the shore. THE GARDEN TOAD 25 From these eggs the young toads hatch as tadpoles and in their life-history pass through an interesting metamorphosis. (See Chapter IX.) TrEcHNIcAL Note.—The teacher should be provided with several well-cleaned skeletons of the toad in order that the bones may be care- fully studied. Boil in a soap solution a toad from which most of the muscles and skin have been removed (see Appendix I). Leave in this solution until the muscles are quite soft and then pick off all bits of mus- cles and tissue from the bones. If this is carefully done, the ligaments which bind the bones will be left intact and the skeleton will hold together. Note that the skeleton (fig. 9) consists of a head portion which is composed of many bones joined together to form a bony box, the skull; of a series of small segments, the vertebre, forming the vertebral column, which with the skull forms the axial skeleton; and of the appendicular skeleton, consisting of the bones of the fore and hind limbs. Note that the skull is composed of many bones joined together, some by sutures, while others are fused. The anterior limbs (arms) articulate with the pectoral or shoulder-girdle. ‘The arms will be seen to be made up of a number of bones placed end to end. Note that the uppermost, the humerus, is attached to the pectoral girdle, while at its lower end it articulates. with the vadio-ulna. At the lower end of the radio-ulna is a small series of carpal bones which afford attachments for the slender finger-bones, the ¢halanges or digital bones. The bones of the leg are articulated with a closely fused set of bones, the pelvic girdle. The leg-bones, proceeding from the pelvic girdle, are named femur, tibio- fibula, tarsal bones, and phalanges or digits. To what bones of the arm do these correspond? Determine the other prin- cipal bones of the skeleton by reference to figure 9. TecunicaL Notr.—In a specimen which has been macerated for some time in 20% nitric acid dissect out the nervous system. Place the specimen in a pan, ventral side uppermost, and pin out. Carefully _ pick away the vertebre andthe roof of the mouth-cavity, thereby exposing the central nervous system, which will appear light yellow. 26 THE ANIMALS AND MAN nasal ‘sy, palatine *s astragalus Fic. 9. Skeleton of the garden toad, THE GARDEN TOAD 27 Examine the brain. In front of the true brain are the olfactory lobes, the nervous centre for the sense of smell. The brain itself is composed of several parts. The anterior portion consists of two elongated parts, the cerebral hemis- pheres; just back of these are the optic lobes or midbrain, consisting of two short lobes, which are followed by the small cerebellum, which in turn is followed by a long part, the medulla oblongata, which runs imperceptibly into the long dorsal nerve, the spinal cord. Note the large optic nerves running out to each eye. How far backward does the spinal cord extend? Note the many pairs of nerves given off from the brain and spinal cord. These nerves branch and subdivide until they end in very fine fibres. Some end in the muscle-fibres, and through them the cen- tral nervous system innervates the muscles. These are motor endings. Still others pass to the surface and receive impressions from the outside. These last are sensory end- ings. Note that the spinal nerves arise from the spinal cord by two roots, an anterior or ventral, and a posterior or dorsal root. Trace the principal spinal nerves to’ the body-parts innervated by them. These nerves are numbered as first, second, etc., according to the number of the vertebrae (count- ing from the head backward) from behind which they arise. For a more detailed account of the anatomy of the toad (frog) the student may refer to pecker and Haswell’s Text- book of Zoology, Vol. II. CHAPTER IV THE CRAYFISH (Cambarus sp.) TECHNICAL NotEe.—The crayfish, or crawfish, is found in most of the fresh-water ponds and streams of the United States. (It is not found east of the Hoosatonic River, Mass. In this region the lobster may be used. On the Pacific coast the crayfishes belong to the genus Astacus.) Crayfishes may be taken by a net baited with dead fish, or they may be caught in a trap made from a box with ends which open in, and baited with dead fish or animal refuse of any sort. This box should be placed in a pond or stream frequented by crayfish. If possible the student should study the living animal and observe its habits. Crayfish which are to be kept alive should be placed in a moist chamber in a cool place. They will keep for a longer time in a moist chamber than in water. Some fresh specimens should be in- jected by the teacher for the study of the circulatory system. A watery solution of coloring matter or, better, of an injecting mass of gelatine (see Appendix I) is injected into the heart through the needle of a hypo- dermic syringe. For the purpese of injecting, a small bit of the shell may be removed from the cephalothorax above the heart. Specimens which are to be kept for some time should be placed in alcohol or 4% formalin. External structure (fig. 10).—Place a specimen in a pan for study. Note that the body, which of course differs much in shape from that of the toad, is also unlike that of the toad in being covered by a hard calcareous exo-skeleton, which acts as a covering for the soft parts and also as a place of attachment for the muscles, just as the internal skeleton does in the case of the toad. The body is composed of an anterior part, the cephalothorax, and a posterior part, the abdomen. The cephalothorax is covered above and on the sides by the carapace, which is divided into parts correspond- ing to the head and thorax of the toad by the transverse 23 THE CRAYFISH 29 antennule antenna Saas) chela walfeing legs - , ‘ / thorax, , genital aperture Fic. 10. Ventral aspect of crayfish, Cambarus sp. with the appendages of one side disarticulated. 30 THE ANIMALS AND MAN cervical suture. The abdomen is composed of segments. How many? The flattened terminal segment is called the telson. Is the cephalothorax composed of segments? Where is the mouth of the crayfish? Where is the anal opening? At the anterior end of the cephalothorax note a sharp projection, the rostrum. Where are the eyes? Remove one of them and examine its outer surface with a microscope. A bit of the outer wall should be torn off and mounted on a glass slide. Note that it is made up of a great many little facets placed side by side. Each of these facets is the exter- nal window of an eye element or ommatidium. An eye com- posed in this way is called a compound eye. In front of the eye note two pairs of slender many-segmented appendages. The shorter pair, the antennules, are two-branched. Remove one of them and note at its base a small slit along the upper surface. This slit opens into a small bag-like structure which contains fine sand-grains. The bag is protected by a series of fine bristles along the edge of the slit. This bag- like structure is believed to be an auditory organ. The longer pair of appendages are the antenne, and the sense of smell is believed to be located in the fine hair-like pro- jections upon the joints. Thus it is seen that the sense- organs of the crayfish, like those of the toad, are located on the head. Beneath the basal portion of each antenna there is a flat plate-like projection, at the base of which on the upper, edge will be noted a small opening, the exit of the kidney, or green gland. Make a drawing of the surface of part of an eye; also of an antennule; and of an antenna. TECHNICAL NoTE.—Stick one point of the scissors under the pos- terior end of the carapace on the right side, and cut forward, thus exposing a large cavity, the gill-chamber. Remove all of the mouth- parts, legs and abdominal appendages from the right side, being careful to leave the fringe-like parts, the gills, attached to their respective legs. Place all of the appendages in order on a piece of cardboard. THE CRAYFISH 3I Examine the abdominal appendages, called pleopods, or swimming feet. How many pairs are there? Each is com- posed of a basal part, the protopodite, and two terminal seg- ments, an inner one, the endopodite, and an outer, the exo- podite. In the males the first and second pleopods of the abdomen are larger and less flexible than the others. In the female the pleopods serve to carry the eggs and the first two pairs are very small or absent. Note the last set of abdomi- nal appendages. These are the uropods, which together with the telson form the tail. Make a drawing of the pleopods of one side. Examine the appendages of the cephalothorax. Like the appendages of the abdomen the typical composition of each includes a protopodite, an exopodite and an endopodite, but some of these appendages are much modified, and show a loss of one of these parts, or the addition of an extra part. The cephalothoracic appendages may be divided into three groups, an anterior group of three pairs of mouth-parts (belonging to the head) of which the first pair is the mandi- bles and the others are the maxille; a second group of three pairs of foot-jaws or maxillipeds, belonging to the thorax, and a third group of five pairs of walking-legs. The man- dibles, lying next to the mouth-opening, are hard and jaw- like and lack the exopodite; the first maxilla are small and also lack the exopodite; the second maxilla have a large paddle-like structure which extends back over the gills on each side within the space, the branchial chamber, above the gills. It is by means of this paddle-like structure (the scaphognathite) that currents of water are kept up through the gill-chambers. The maxillipeds increase in size from first to third pair. Each pair of walking-legs except the last bears gills. These gills are the organs by which the blood is purified. The blood of the crayfish flows into the large vessels on the outer sides of the gill and thence into the fine vessels in the little leaf-like lamella. At the same 32 THE ANIMALS AND MAN time the air which is mixed with the water bathing the gills passes freely through the thin membranous walls of these lamella and blood-vessels, and the blood gives off its car- bon dioxide to the water and takes up oxygen from the air in the water. Thus it will be seen that the office of the gill is like that of the lung in the toad, namely, to act as an organ for the elimination of carbon dioxide and the taking up of oxygen. Note the pincer-like appendages of the first pair of legs. These pincers are the chele, with which food is torn into bits and placed in the mouth. In the basal segment of each of the last pair of legs of the male note the genital pore. In the female the genital pores are in the basal segments of the next to last pair of legs. Is the crayfish bilaterally symmetrical ? Note the repetition of parts in the crayfish, that is, the recur- rence of similar parts in successive segments. This serial repetition of parts among animals is called metamerism. Internal Structure (fig. 11) —TrcunicaL Nore.—With a pair of scissors cut through the dorsal wall of the cephalothorax into the body-cavity. Cut the body-wall away from both sides and remove the middle portion. At the anterior end of the cephalothorax note the large membranous sac, the stomach. Attached to each end of this are sets of muscles which control its movements. To the right and left of the stomach notice attached to the shell large muscles which connect by stout ligaments at their lower ends with the mandibles. Note a yellow fringe-like structure, the digestive gland, which fills most of the region about the stomach. It connects by a pair of small tubes, the bile-ducts, with the alimentary canal. Within the posterior portion of the cephalothorax note a pentagonal sac, the heart, contained within a delicate membrane, the pericar- dium. Remove the pericardium and note a pair of dorsal openings into the heart, called ostia. (There are also two 33 THE CRAYFISH ‘ds snapquod aanjuadn 70} yuab harap JDULULOPgD 708.L0p wnepsnoiuad / suatafap soa ad: ¢ D ‘ysgke1o Jo uoljoes [euIpnySuco] uelpem jo weiseq ‘TT ‘ol supb.o hsoyopndoo fusaqan pousays Yinou .--- snBoydoss0 / DYSO : ’ yoouojs yJaa}-yoowojs / ix ; /p409y $2489} \ ‘ \ iY yoouoss n1ojfid » \ puv)6 wadub huaqan ovupoyzydo 34 THE ANIMALS AND MAN lateral pairs and a ventral pair of ostia.) Note passing anteriorly from the heart along the median line to the eyes a blood-vessel, the ophthalmic artery. Arising from the anterior portion of the heart are the antennary arteries, run- ning to the antenne. Yet another pair running anteriorly from the heart to the stomach and digestive glands are called the hepatic arteries. From the posterior end of the heart arises the dorsal abdominal artery, running back to the telson. Below this arises the sternal artery, which will be seen later. In the region below the heart are located the reproductive organs. They are whitish glandular masses from each of which runs a tube which opens at the base of the last pair of walking-legs in the male, and at the base of the third pair of walking-legs in the female. TEcHNICAL NotE.—Cut longitudinally through the dorsal wall of the abdomen on either side of the median line and remove the piece of shell. Note the powerful muscles within which flex and extend the abdomen. By a rapid contraction of these muscles the tail is brought beneath the body, propelling the animal strongly backwards. When the crayfish crawls it generally goes forward, but in swimming it reverses this direction. Make a drawing showing, in their natural position, the internal organs which have been studied. Examine the alimentary canal for its whole length. Note that the large bladder-shaped stomach is attached to the mouth-opening by a short tube. What part of the canal is this? From the posterior end of the stomach is a short thick-walled part, the small intestine, followed by a long straight tube, the Jarge intestine, which opens to the exterior through the anus. TecunicaL Note.—Remove the alimentary canal, detaching it from the anal end first, and working forward. THE CRAYFISH 35. Cut the stomach open. Note an interior portion, the cardiac chamber, and a smaller posterior portion, the pyloric chamber. Examine its inner surface. What do you find here? This structure is called the gastric mill. Food, which for the most part consists of any dead organic matter, is chewed by the “stomach-teeth” into fine bits, and is then passed into the pyloric chamber. It is here that the diges- tive glands empty their secretion into the food. ‘These glands have the same office as have the liver and pancreas combined in the toad, and so they are often called the hepato-pancreas. When the stomach has been removed there will be noted in the anterior portion of the body paired, flattened bodies, already mentioned, which connect with openings at the base of each of the antenne by means of wide thin-walled sacs, the ureters. These organs are the kidneys, or green glands. Their office is similar to that of the kidneys in the toad, namely, the elimination of waste from the body. TecHnicaAL Note.—Carefully remove all of the alimentary canal, digestive glands, and reproductive organs. This process will expose the floor of the cephalothorax. Now cut away from either side the horny floor or bridge at the bottom of the cephalothorax. If the specimen has not already been immersed, place it in clear water for further dissection. The foregoing dissection will expose the central nervous system. It extends as a series of paired ganglia connected by a double nerve-cord along the ventral median line from the cesophagus to the last segment of the abdomen. From what points do the lateral nerves arise? Anteriorly the double nerve-cord divides, the two parts passing upward on each side of the cesophagus, where they again meet to form the supra-esophageal ganglion or brain. Where do the nerves run which rise from the brain? What is the differ- ence between the position of the central nervous system in the crayfish and in the toad? 36 THE ANIMALS AND MAN Make a drawing of the nervous system. Just beneath the nerve-cord note a blood-vessel extending the length of the body. This is the sternal artery, which arises from the posterior end of the heart and passes ventrally at one side of the alimentary canal and between the nerve- cords. Here the sternal artery divides into an anterior and a posterior branch, from which lesser branches are given off to each one‘of the appendages. The various arteries running to all parts of the body finally pour out the blood into the body-cavity, where it flows freely in the spaces among the various tissues and organs. After the blood has bathed the body tissues it flows to the gills on either side passing up the outer side of the gill through delicate thin- walled vessels, where it is oxygenated as has already been described. From the gills the purified blood flows back on the inner side through a large chamber, sinus, into the peri- cardium, through the ostia of the heart, whence it is driven into the arteries once more. ‘This sort of a circulatory sys- tem in which the blood in places is not enclosed in a definite vessel is known as an open system. In the toad we find the blood in a closed system, i.e., arteries leading into capillaries which in turn lead into veins, in no case allowing the blood to pass freely through the spaces of the body. For a detailed account of the life and structure of the crayfish see Huxley’s ‘‘The Crayfish: an Introduction to the Study of Zoology.” CHAPTER V AMCG@BA, PARAMECIUM AND VORTICELLA Amoeba.—Trcunicat Nore.—Amebe are found in stagnant pools of water on the dead leaves, sticks and slime at the bottom. To obtain them, collect slime and water from various puddles in separate bottles and take them to the laboratory. Place a small drop of slime on a slide under a cover-glass. Examine under the low power first and note any small transparent or opalescent objects in the field. Examine these ob- jects with the higher power and note that some are mere granular jelly-like specks, which slowly (but constantly) change their form. These are Amebe. A teacher of zoology recommends the following’ method of. obtaining a large supply of Amebe: “For rearing Amabe place two or three inches of sand in a common tub, which is then filled with water and placed some feet from a north window; three or four opened mussels, with merest trace of the mud from the stream in which they are taken, are partially buried in the sand and a handful of Nziella and a couple of crayfish cut in two are added; as decomposition goes on a very gentle stream is allowed to flow into the tub, and after from two to four weeks abundant Amebe are to be found on the surface of the sand and in the scum on the sides of the tub; small Amebe appear at first, and later the large ones.” Having found an Ameba (fig. 12) note its irregular shape, and if it moves actively observe its method of moving. How is this accomplished? The viscous, jelly-like substance which composes the whole body of an Ameba is called protoplasm. ‘The little processes which stick out in various directions are the “false feet” (pseudopodia). Note that the outer portion, the ectosarc, of the protoplasmic body is clear, while the inner, the exdosarc, is more or less granular in structure. Has Ameba a definite body-wall? Do the pseudopodia protrude only from certain parts of the body? 37 38 : THE ANIMALS AND MAN Within the endosarc note a clear globular spot which con- tracts and expands, or pulsates, more or less regularly. This is the contractile vacuole. Note the small granules which move about within the endosarc. These are food-particles Fic. 12. An Ameceba, showing forms assumed by a single individual in four successiv: changes. (Greatly magnified; from life.) which have been taken in through the body-wall. Note how pseudopodia flow about food-particles in the water and how these are digested by the protoplasm. If an Am@eba comes into contact with a particle of sand, note how it at once retreats, Note within the endosarc an oval transparent body AMCEBA, PARAMECIUM AND VORTICELLA 39 which shows no pulsations. This is the nucleus, a very com- plex little structure of great importance in the make-up of Amoeba. Note that Ame@ba has no mouth or alimentary canal; no nostrils or lungs, no heart or blood-vessels, no muscles, no glands. It is an animal body not made up of numerous dis- tinct organs and diverse tissues. Its whole body is a minute speck of protoplasm, and forms a single animal cell. But it takes in food, it moves, it excretes waste matter from the body, is sensitive to the touch of surrounding objects, and, as we may be able to see, it can reproduce itself, ie., produce new Amebe. Ameba is one of the simplest living animals. It is only rarely that we can find an Ameba actually repro- ducing. The process, in its gross features, is very simple. First the Ameba draws in all of its pseudopodia and remains dormant for a time. Next, certain changes take place in the nucleus, which divides into equal portions, one part with- drawing to one end of the protoplasmic body, the other to the opposite end. Soon the body protoplasm itself begins to divide into two parts, each part collecting about its own half of the nucleus. Finally the two halves pull entirely away from each other and form two new Amebe, each like the original, but only half as large. This is the simplest kind of reproduction found among animals. Amebe continue to live and multiply as long as the con- ditions surrounding them are favorable. But when the pond dries up the Amebe in it would be exterminated were it not for a careful provision of nature. When the pond begins to dry up each Ameba contracts its pseudopodia and the pro- toplasm secretes a horny capsule about itself. It is now protected from dry weather and can be blown by the winds from place to place until the rains begin, when it expands, throws off the capsule and commences active life again in some new pond. fo 40 THE ANIMALS AND MAN The Slipper Animalcule (Paramecium sp.) TECHNICAL NOTE.— Paramecia can be secured in most pond-water where leaves or other vegetation are decaying. However, if specimens are not readily se- cured place some hay or finely cut dry clover in a glass dish, cover with water and leave in the sun for several days. In this mixture specimens will develop by thousands. Place a drop of water containing Paramecia on a slide with cover-glass over it. Using a low power, note the many small animals darting hither and thither in the field. Run a thin mixture of cherry gum in water under the cover-glass. In this mixture they can be kept more quiet and be better studied. How does Paramecium (fig. 13) differ from Ameba in form and movement? Has the body an anterior and a posterior end? The delicate, short, thread-like pro- cesses, on the surface of the body, which beat about very rapidly in the water are called cilia, and they are simply fine prolongations of the body protoplasm. What is their function? Note a fine cuticle cov- ering the body. Note also many minute oval sacs lying side by side in the ectosarc. These are called trichocysts and from each a fine thread can be thrust out. Note on one side, beginning at the anterior end, the buccal groove leading into the interior through the gullet. Observe also that by the action of the cilia in the buc- fic. 1%, Pasonemtian an cal groove food-particles are swept note the body-wall, cilia, into the gullet. Rejected or waste buccal groove, gullet, con- particles are ejected from the body tractile vacuoles and nu- occasi onally. Where? Note about clei, (Greatly magnified; ~~ : from life.) midway of the Parameciuman ovoid py. ee NS SSE apa SS AMCEBA, PARAMECIUM AND VORTICELLA 41 body with a smaller oval one attached to its side, the former being the macronucleus, the latter the micronucleus. Note that there are two contractile vacuoles in the Paramecium; also that the food-vacuoles have a definite course in their movement inside the endosarc. Make a drawing of a Paramecium. In comparing Paramecium with Ameba it is apparent that the body of the first is less simple than that of the second. The definite opening for the ingress of food, the two nuclei, the fixed cilia, and the definite cell-wall giving a fixed shape to the body, are all specializations which make Paramecium more complex than Ameba. But the whole body is still composed of a single cell, and there is, as in Ameba, no differentiation of the body-substance into different tis- sues, and no arrangement of body-parts as systems of organs. ; Paramecium may occasionally be found reproducing. This process takes. place very much as in Ameba. The animal remains dormant for a while, the micronucleus then divides, the macronucleus elongates and finally divides in two, the protoplasm of the body becomes constricted into two parts, each part massing itelf about the withdrawn halves of the macro- and micronuclei, and lastly the whole breaks into two smaller organisms which grow to be like the original. After multiplication or reproduction has gone on in this way for numerous generations (from one to two hundred), a fusion of two Paramecia seems necessary before further divisions take place. (This is probably true of Am- wba also.) This process of fusion, called conjugation, may be noted at some seasons. Two Paramecia unite with their buccal grooves together, part of the macronucleus and micronucleus of each passes over to the other, and the mixed elements fuse together to form a new macro- and micronucleus in each half. The conjugating Paramecia now separate, and each divides to form two new individuals. 42 THE ANIMALS AND MAN The Bell Animalcule (Vorticella sp.)—TxrcunicaL NotTE.— Specimens of Vorticella may usually be found in the same water with Ameba and Paramecium. The individuals live together in colonies, a single colony appearing to the naked eye as a tiny whitish mound-like Fic. 14. Vorticella sp.; one individual with stalk coiled and one with stalk extended; note the peristome, epis- tome, vestibule, nucle- us, contractile vesicle, food particles, ete. (Greatly magnified; from life.) tuft or spot on the surface of some leaf or stem or root in the water. Touch sucha spot with a needle, and if it is a Vorticellid colony it will contract instantly. Bring bits of leaves, stems, etc., bearing Vorticellid colonies into the lahoratory and keep in a small stagnant-water aquarium (a battery- jar of pond-water will do). Examine a colony of Vorticella in a watch-glass of water or in a drop of water on a glass slide under the microscope. Note the stemmed bell- shaped bodies which compose the colony. Each bell and stem to- gether form an individual Vorticella (fig. 14). - How are the members of the colony fastened together? Tap the slide and note the sudden con- traction of the animals; also the details of contraction in the case of an individual. Watch the colony expand; note the details of this move- ment in the case of an individual. Make drawings showing the col- ony expanded and contracted. With higher power examine a single individual. Note the thick- ened, bent-out, upper margin of the bell. This margin is called the peristome. With what is it fringed? The free end of the bell is near- ly filled by a central disk, the epis- AMCBA, PARAMECIUM AND VORTICELLA 43 tome, with arched upper surface and a circlet of cilia. Between the epistome and peristome is a groove, the mouth or vestibule, which leads into the body. Study the internal structure of the transparent, bell-shaped body. Note the differentiation of the protoplasm comprising the body into an inner transparent colorless endosarc containing various dark-colored granules, vacuoles, oil-drops, etc., and an outer uniformly granular ectosarc not containing vacuoles. Is the stalk formed of ectosarc or endosarc or of both? Note the curved nucleus lying in the endosarc. (This may be difficult to distinguish in some specimens.) Note the nu- numerous large circular granules, the food particles. Note the contractile vesicle, larger and clearer than the food vacuoles. Note the thin cuticle lining the whole body externally. A high magnification will show fine transverse ridges or rows of dots on the cuticle. Make a drawing showing the internal structure. Observe a living specimen carefully for some time to determine all of its movements. Note the contraction and extension of the stalk, the movements of the cilia of peri- stome and epistome, the flowing or streaming of the fluid endosarc (indicated by the movements of the food particles), the behavior of the contractile vesicle. Make notes and drawings explaining these motions. Specimens of Vorticella may perhaps be found dividing, or two bell-shaped bodies may be found on a single stem, one of the bodies being sometimes smaller than the other. These two bodies have been produced by the longitudinal division or fission of a single body. In this process a cleft first appears at the distal end of the bell-shaped body, and gradually deepens until the original body is divided quite in two. The stalk divides for a very short distance. One of the new bell-shaped bodies develops a circlet of cilia near the stalked end. After a while it breaks away and swims about by means of this basal circlet of cilia. Later it settles 44 THE ANIMALS AND MAN down, becomes attached by its basal end, loses its basal cilia and develops a stalk. : “Conjugation occurs sometimes, but it is unlike the con- jugation of Paramecium in two important points: Firstly, the conjugation is between two dissimilar forms; an ordi- nary large-stalked form, and a much smaller free-swimming form which has originated by repeated division of a large form. Secondly, the union of the two is a complete and permanent fusion, the smaller being absorbed into the larger. This permanent fusion of a small active cell with a relatively large fixed cell, followed by divis- ion of the fused mass, presents a striking analogy to the process of sexual reproduction occurring in higher animals.” The single-celled body.—The study of Ameba, Para- meecium and Vorticella has made us acquainted with a type of animal body very different from that of the toad or the cray- fish. These extraordinarily minute animals have a body so simple in its composition, compared with the toad’s, that if the toad’s body be taken for the type of the animal body, Ameba might readily be thought not to be an animal at all. The body of Ameba is not composed of organs, each with a particular function or work to perform. Whatever an Ameba does is done, we may say, with its whole body. But as we learn the things that this formless viscid speck of matter does, we see that it is truly an animal; that it really does those things which we have learned are the necessary life- processes of an animal. Ameba takes up and digests food composed of organic particles; it has the power of motion; it knows when its body comes in contact with some external object, that is, it can feel or has the power of sensation. Ameba takes in oxygen and gives out carbon dioxide, and it can produce new individuals like itself, that is, it has the power of reproduction. But for the performance of these various life-processes or functions it has no widely differing AMEBA, PARAMECIUM AND VORTICELLA 45 special parts or organs, no mouth or alimentary canal, no lungs or gills, no legs, no special reproductive organs. We have here to do with one of the “simplest animals.” With a minute, organless, soft speck of viscous matter called pro- toplasm for a body, the simplest structural condition to be found among living beings, Ameba nevertheless is capable of performing in the simplest way in which they may be performed, those processes which are essential to animal life. Paramecium has a body a little less simple than Ameba. The food-particles are taken into the body always at a cer- tain spot; this might be spoken of as a mouth. And the body has some special locomotory organs, if they may be so called, in the presence of the cilia. The body, too, has a definite shape or form. But, as in Ameba, there is no alimentary canal, nor nervous system, nor respiratory sys- tem, nor reproductive system. The whole body feels and breathes and takes part in reproduction. A long jump has been made from the toad and crayfish to Ameba and Paramecium; from the complex to the simplest animals. But, as will later be seen, the great difference between the bodies of these simplest animals and those of the highly complex ones is only a difference of degree; there are animals of all grades and stages of struc- tural.condition connecting the simplest with the most com- plex. When animals are studied systematically, as it is called, we begin with the simplest and proceed from them to the slightly complex, from these to the more complex, and finally to the most complex. There are hundreds of thou- sands of different kinds of animals, and they represent all the degrees of complexity which lie between the extremes we have so far studied. The cell.—The characteristic thing about the body of Ameba and Paramecium and the other ‘simplest animals” —for there are many members of the group of “simplest 46 THE ANIMALS AND MAN animals,” or Protozoa—is that it is composed, for the ani- mal’s whole lifetime, of a single cell. A cell is the structural unit of the animal body. The bodies of all other animals ex- cept the Protozoa, the simplest animals, are composed of many cells. These cells are of many kinds, but the simplest kind of animal cell is that shown by the body of an Ameba, a tiny speck of viscous, nearly colorless protoplasm without fixed form. The protoplasm composing the cell is differenti- ated to form two parts or regions of the cell, an inner denser part, called the nucleus, and an outer clearer part, called the cytoplasm. Sometimes, as in the Paramecium, the cell is en- closed by a cell-wall which may be simply a denser outer layer of the cytoplasm, or may be a thin membrane secreted by the protoplasm. Thus the cell is not what its name might lead us to expect, typically cellular in character; that is, it is not (or only rarely is) a tiny sac or box of symmetrical shape. While the cell is composed essentially of protoplasm, yet it may contain certain so-called cell-products, small quantities of various substances produced by the life-processes of the protoplasm. These cell-products are held in the proto- plasmic body-mass of the cell, and may consist of droplets of water or oil or resin, or tiny particles of starch or pigment, etc. The cell cannot be said to be composed of organs, be- cause the word organ, as it is commonly used in the study of an animal, is understood to mean a part of the animal body which is composed of many cells. But the single cell can be somewhat differentiated into parts or special regions, each part or special region being especially associated with some one of the life-processes. In Paramecium, for exam- ple, the food is always taken in through the so-called mouth- opening; the fine protoplasmic cilia enable the cell to swim freely in the water, the waste products of the body are always cast out through a certain part, and so on. But this is a very simple sort of differentiation, and the whole body is only one of those structural units, the cells, of which so AMGBA, PARAMECIUM AND VORTICELLA 47 many are included in the body of any one of the complex animals. Protoplasm.—The protoplasm, which is the essential liv- ing substance of the typical animal cell and hence of the whole animal body, is a substance of very complex chemical and physical make-up. The most important thing about the chemical constitution of protoplasm is that there are always present in it certain complex albuminous substances called proteids which are never found in inorganic bodies, although the elements that compose these substances as well as all the rest of the protoplasm are the familiar ones, car- bon, nitrogen, hydrogen, oxygen, sulphur, phosphorus, potassium, sodium, etc. The atoms in a single proteid molecule often number more than a thousand, and the mole- cules are very large. But chemists have yet to find out a great deal about these complex albuminous compounds. In addition to the proteids protoplasm usually contains certain native albumins and certain other characteristic compounds known as carbohydrates and fats (which differ essentially from the albuminous substances in lacking nitro- gen as a composing element). There are also various salts and gases and always water to be found in living substances. Water is absolutely necessary to the physical condition of half fluidity which gives to protoplasm its essential capacity for motion on itself. The commoner salts found in living substances are compounds of chlorine as well as the car- bonates, sulphates, and phosphates of the alkalies and al- kali earths, especially common salt (sodium chloride), potassium chloride, ammonium chloride, and the carbon- ates, sulphides, and sulphates of sodium, potassium, magne- sium, ammonium, and calcium. The gases found in living matter are oxygen and carbon dioxide. These, when not in chemical combination, are almost always dissolved in water, although rarely they may be in the form of gas bubbles. The physical constitution of protoplasm seems to be that 48 THE ANIMALS AND MAN of a viscous liquid containing many fine globules of a liquid of different density. It is a sort of liquid foam. Some naturalists however, believe the fine globules to be solid granules while still others believe that numerous fine threads of dense protoplasm lie coiled and tangled in the clearer viscous protoplasm. The difficulty in determining the physical structure is due to the limitations of the microscope. The ultimate structure of protoplasm is ultra-microscopic. What little is known of the chemistry and physics of proto- plasm certainly is far from explaining its wonderful properties. It should be held clearly in mind also that the full life capacity of protoplasm is realized only when it is in that differ- entiated and organized condition typical of the structural unit or cell. The essential thing about the cell is not that it has a definite shape or size or that it is truly cell- or sac- like, but that it is a tiny but definitely organized mass of protoplasm with various substances secreted by or held in it. The protoplasm itself is differentiated into at least two parts, an inner, denser, smaller part called the nucleus, and an outer surrounding, usually larger, portion called the cytoplasm. Such a differentiated or organized proto- plasmic unit can perform all of the essential functions of life and persist in this performance indefinitely unless de- stroyed by extrinsic causes. The cell itself may not have an indefinite existence as a unit, but it will be the progenitor of an indefinitely prolonged series of cells. A single part of this cell, that is, a bit of protoplasm either of the nucleus or the cytoplasm, or the whole of either can perform for a while most of the activities of life; but such a part always lacks the capacity for reproduction, that is, for persistence as living matter. CHAPTER VI ANIMAL PHYSIOLOGY Motions and locomotion.—Our attention is usually first attracted to an animal by the movements it makes. These are the plainest proof that it is alive. For the animal itself the ability to move is essential to existence. Most animals move in search of food, to escape from their enemies, to find and build their homes, to seek their mates, and care for their young. In the higher forms the organs of motion constitute the great bulk of the body. The shape and size of such an animal are determined largely by these organs. The heart and blood-vessels, the lungs and digestive sys- tem, are principally concerned with supplying the organs of PEFLRPP LF Fic. 15. Scorpion walking, showing the successive positions of body and legs. (After instantaneous photographs by Marey.) motion with materials necessary for their working, and by far the larger part of the work of the sense organs and ner- vous system is to put these organs into action, and to direct and control them. We can see therefore that they have much to do with both the structure and physiology of ani- mals. Indeed the most marked usual difference between animals and plants is the possession by the former of the organs of motion and their nerves. True, plants have the 49 50 THE ANIMALS AND MAN power of motion and are sensitive to light, heat, and other influences as are animals, but to a far less degree. Among the movements made by animals, the moving of the body from place to place, usually spoken of as locomo- tion, generally requires the greatest energy or power. The other motions are those of parts of the body, as the arms, legs, head, etc. There are three different ways in which locomotion takes place, namely, by swimming in water, crawling or walking or leaping on some solid object, as the ground or the trunk of a tree, and by flying in the air. In each of these three cases the body must first be supported, then either pushed or pulled along or perhaps both pushed and pulled. In swimming the body is supported by the water. In animals that swim it is either lighter than water, as in the duck, or just as heavy or only a little heavier, as in fishes, so that it is wholly or almost wholly held up by the water, and the full power of the leg, fin, or tail used in the motion can be devoted to pushing the animal along. Animals crawling on the bottom in water also have very little to do in holding up the body, the water supporting them. But those that move on land or fly with their bodies immersed in air alone have the body only very slightly supported by the air. These animals must therefore devote energy to supporting the body as well as to moving it along, and they have special means for this. As already said the body is moved by pushes or pulls. In by far the most cases motion results from pushes given by a part of the body against something outside. Now it is plain that air is a very poor thing to push against as com- pared with water or a solid. Naturally since water is a liquid it gives way readily to a push, but its heaviness offers much greater resistance to motion than does the air. The solid ground, of course, offers most of all. Currents in wa- ter and air are of peculiar help in this matter. Water cur- ANIMAL PHYSIOLOGY 51 rents may carry an animal for great distances without any work on its part; while air currents make it possible for birds to soar with little effort. Flight by the vibration of wings, as in birds and insects, requires the greatest expen- diture of energy, since the pushes against the thin air must be made quickly and with great force and be rapidly re- peated to be effective for support and locomotion. Man in making locomotive machines, railway engines, automobiles, steamships, etc., has met the same conditions as the animals; but the difficulties of aerial locomotion are so great that he has only now succeeded in making a beginning toward achieving a mechanism for it. The simplest and what may be called the most imperfect modes of locomotion are shown by the simplest animals. These modes we have already studied in Amceba, Para- meoecium, and Vorticella. The living elements in the body of the higher animals are the many individual cells, and they show many kinds of move- ment. But motion in the higher animals is produced chiefly by the contraction of muscles, each of which is hm made up of contractile fibres A which may be thought to be modifications of such a fibre as exists in the stalk of Vor- ticella. The muscles require firm v.n.c. points of attachment to pull Fic. 16. Diagram of cross-section against and the complex through the thorax of an insect movements of most animals to show the exo-skeleton and the s ie leg and wing muscles attaching require also tigid levers and to it; , heart; al. c, alimentary fyulcra. These firm solid canal; v. 2. c, ventral nerve cord; parts of an animal’s body w, wing; J, leg; “m, muscles. : (Much enlarged; after Graber.) COMpOse its skeleton, 52 THE ANIMALS AND MAN The skeleton of a backboneless or invertebrate animal differs from that of a backboned or vertebrate animal (as we have seen in comparing the frog and crayfish) not in the use made of it but in its arrangement and in the part of the body from which it is mainly developed. The skeleton of the invertebrate is developed from the skin, and forms a hard casing over the whole or part of the body (fig. 16). It is therefore called an exo-skeleton. In the vertebrates the skeleton is mainly developed from tissues within the body and is called in consequence the endo-skeleton. Even more than in the invertebrates it is a system (fig. 17) of levers, fulcra, and points of attachment for muscles to work with, and is as important a part of the Fic.17. Skeleton of arm organs of motion as is the muscular enere bari a ‘ muscle; to show how system itself. bones and muscle act To illustrate the use of the skeleton as levers. (After Jen- of a vertebrate we may examine the mine) bones of the hind legs of a cat (fig. 18). The upper bone, the femur, is attached by a joint to the large irregularly shaped bone called the ilium, which is firmly bound to the backbone. Below the femur are two bones, the largest, called tibia, being bound : by a joint to the Fic. 18. Skeleton of cat. (After Reighard and femur. Below the Jennings.) tibia is a group of bones, the tarsal bones, pretty firmly fastened together. The largest makes a joint with the tibia. Each of the four tarsal bones toward the toes makes a joint with a ANIMAL PHYSIOLOGY 53 slender bone in the body of the foot. These are the metatarsals. At the end of each metatarsal is a series of three bones which forms the skeleton of each toe. All of these bones together constitute a system of levers which the muscles of the leg can draw up in a some- what folded position, and then straighten out with quick- ness and force. Since during such movements the toes rest on the solid ground, the body is lifted and thrown for- ward. There are several strong muscles which make the pulls for these motions, but a single pair may be studied as an example of the method of attachment and action of all. Fig. 19 shows the large muscles of the fore leg of a cat. Each consists of a large central mass formed of the muscular or contractile substance proper bound up into a compact body by connective tis- sues, with strings or bands of connective tissue at the ends fastening the muscular mass to the bones. These fastenings are tendons. When the muscular substance contracts it of course pulls on the two ten- donous ends. If one end of a muscle in the hind leg is attached. to the hip- bone it cannot move, but the one fastened to the tibia moves this bone as a lever, Fic.19. Muscles on With its fulcrum at the end of the fe- side of fore leg of mur. The tibia is brought toward the cat. (After Reigh- femur, and we say that the limb is flexed. cae la Another muscle in contracting will act on the tibia as a lever also, but it brings the tibia back again into a straight line with the femur. This motion is called extension. For each part of the limb from hip to toe are groups of muscles which flex and extend that part, the bones being levers and fulcra and points of attachment. Most of these levers are of the kind called in mechanics 54 THE ANIMALS AND MAN levers of the third class. By them quickness of motion is magnified. Thus by noting first what motions an animal makes, ‘and then, by dissection, examining the muscles, the bones, and their points and means of attachment, we may come to understand clearly the uses of the muscles and skeleton in any animal. Necessity of oxygen and food.—In the organs of motion just studied, the muscles and bones are only the machinery for motion. They make use of energy but cannot them- selves provide it. Just as an engine and all the wheels and levers connected with it make use of heat, which is one of the forms of energy, to produce the needed motions, so the muscles and bones make use of some form of energy to produce the motions of the animal body. In the steam- engine the special form used is heat, generated by the burn- ing of coal, oil, or wood; by means of this heat, which expands the steam, i.e., the vapor of water, energy is applied to the piston in the form of a push. The motion of the piston is passed over to the wheels and levers of the shop, and by them are given all the different directions and veloci- ties required by the different machines of that particular shop. In the animal body the muscle is the engine, for in it the energy is generated. In a way we do not yet exactly under- stand this energy makes the muscular substance contract and give a pull on the tendon, with the same effect as the push of the steam on the piston, that is, to set the rest of the machinery, the bones, in motion. The bones apply the motion in the way required for the movement of the animal. A striking difference, however, between the animal body and a shop is this, that while in even a very large shop there may be but one engine generating energy to run all the different machines, in the body every muscle is a separate engine, and one bone may be connected with a number of them. Never- ANIMAL PHYSIOLOGY ~ 55 theless the essential facts are the same in both cases. The muscle-engine, like the steam-engine, produces a form of energy and applies it to machines so as to lift weights or to move things from place to place. But we learn in physics that we can get any form of energy only by changing some other form into the one desired. The forms of energy are heat, light, electricity, chemical energy, and tnat of a body in motion. Now the only way to get heat, for example, is by a change from one of the others. We can make a piece of iron hot by striking it with a hammer; here the energy of a moving body is converted into heat. Or the energy of the electric current may be converted into heat or motion. Man’s most common way of getting heat is to take coal, wood, or oil, and apply some heat to start with, when the oxygen of the air will unite with carbon and hydrogen, sub- stances in the coal, wood, or oil, to make two new substances, one of these being carbon dioxide, the other water. This is chemical action; it results in changing chemical energy into heat. In ordinary language this union of oxygen with car- bon or hydrogen is spoken of as “burning” or ‘‘combustion.” An animal cannot make the least motion without using a certain amount of energy. And it has been shown by investigation that the energy possessed by an animal is derived from the chemical energy resulting from the union of oxygen with the carbon, hydrogen, and nitrogen in other substances. ‘The muscles are the engines in which this energy is made use of for motion. This brings us now to see how essential it is that the animal should have in its body oxygen and substances for the oxygen to combine with. Respiration.—Respiration is the name commonly used in books for the process of obtaining oxygen. The pro- cess has, however, another object in addition to procuring oxygen. When oxygen combines with carbon a poisonous gas, carbon dioxide, is formed. If this remains in the muscle or other tissue cells it interferes with the activity 56 THE ANIMALS AND MAN of those cells. It is, therefore, just as necessary for the carbon dioxide to be removed from the body as for oxygen to be supplied to it. Carbon dioxide, like oxygen, is soluble in water. Blood, which is composed largely of water, can carry off carbon dioxide as well as bring oxygen. Also, since carbon dioxide is made by a combination with oxygen it arises just where it can be carried away by the very means that brings the necessary oxygen. Thus the respiratory, aided by the circulatory apparatus manages both the bringing of a supply of oxygen and the disposal of the carbon dioxide. The fundamental fact in the process of respiration is that gases whether free or dissolved in water will readily pass through a thin, moist membrane. Thus, if a closed sac made of thin membrane filled with water in which carbon dioxide is dissolved be immersed in water in which oxygen is dissolved, carbon dioxide will pass out of the sac and oxygen into it until there is the same amount of each outside and inside. If the water outside is constantly replaced all the carbon dioxide will be finally removed. If the oxygen inside the sac is constantly used up and the supply outside is always renewed, oxygen will be constantly going in and carbon dioxide going out. This is just what happens in the living animal. Animals get their oxygen from the air, of which it is a part. The air may be free or dissolved in water. Carbon dioxide is made in the cells of the body. Respiration takes place through the membranes covering all or part of the surface of the body. It requires the con- stant renewal of free air or water containing air on the out- side, and the constant passage of fresh blood on the inside surface of the membrane. This end is attained in a great variety of ways among animals. In the simplest forms, the Protozoa, where we have the most primitive means of motion, we find also the simplest means of respiration. The Amoeba, as we have seen, ANIMAL PHYSIOLOGY 57 simply relies on its whole external surface for breathing, the thin outside layer of the body acting as a membrane through which the oxygen passes in and the carbon dioxide out. During periods of activity the processes protruding from the body increase the amount of respiratory surface sufficiently to provide for the increased respiration demanded by the activity. In ciliated forms the cilia greatly increase the surface area and respiration is further assisted by the con- stant contact of the moving body with fresher water. Even in more complex animals, the common earthworm and the larvee of some insects, for example, the whole external skin is sometimes the only respiratory surface. However, such animals have only sluggish and weak motions. Much increase in size and activity make certain demands on the surface of the body which unfit it for respiraton. The hard covering of insects, crabs, and other animals necessary in connection with locomotion and for protection from inju- ries illustrates this. Again, while in a minute form like Ameeba, the slight increase of surface attained by its pro- truded processes answers the increased respiratory needs, the surface of a large animal would fall far short of doing so, because, according to a familiar law of physics, the mass or bulk of a body increases as the cube of the diameter while the surface increases only as the square. Therefore the larger animals must have special respiratory surfaces with special respiratory apparatus to move the air or water over these surfaces externally, and special circulatory apparatus to move the blood over them internally. Special respiratory surface is provided for in two ways. One is by the extension of a portion of the surface exter- ally; thus gills are formed. The other is by the extension of the surface within the body in the form of tubes, as the trachez in insects, or of sacs, as the lungs in the vertebrates. Water-breathers have gills and air-breathers have trachee or lungs. 58 THE ANIMALS AND MAN In the higher vertebrates the exterior skin surface is not at all adapted for respiration, which, together with the generally greater activity of these animals, necessitates a much greater development of the lungs. Thus instead of the two simple lung sacs of the frog the lizard has a com- piex double sac enlarged by tube-like extensions into the body-cavity. This arrangement gives a much increased respiratory surface. In birds and mammals the extent of surface is immensely increased. It is estimated that the inner surface of a man’s lungs amounts to a thousand square feet in area, or one hundred times the external sur- face of the body. The windpipe gives off one large branch to each lung; these branches divide again and again, the last divisions bearing on their ends very small sacs of thin membrane about which is clustered a net-work of capillary blood-vessels. Through the walls of these small sacs the oxygen and carbon dioxide pass. So far we have seen only how increase of surface is brought about. Accompany- ing this we find improved means for passing the air over the exterior and bringing the blood to the interior sur- face. A frog or salamander breathing quietly enlarges the mouth-cavity by lowering its eS floor, and the air comes in Fic. 20. Tracheal tube, lungs, heart through the nostrils; this air and diaphragm of a mouse. is then squeezed by the upward pressure of the floor of the mouth, the valves in the nostrils close, and it is thus pushed down into the lungs. The muscles in the walls of the body now contract and squeeze upon the air in the lungs, the nostril valves open, and the air is forced out. This method is gradually improved ANIMAL PHYSIOLOGY 59 upon in the vertebrates until in the mammals we find a bony basket of ribs and sternum, the thorax (fig. 20), containing the, lungs, with two sets of muscles between the ribs, which by their alternate contractions and expansions first elevate and extend the ribs, then lower and draw them in, thus enlarging and diminishing the thoracic cavity. We find further a muscular partition in the thorax, the diaphragm, separating it from the abdominal cavity. When the diaphragm, which is convex on the upper side, contracts, it lowers the floor of the thorax, thus enlarging the thoracic cavity; the muscles in the wails of the abdomen then contract and press upon the stomach, intestines, and liver, pushing up the floor of the thorax and so diminishing the thoracic cavity. Thus in two ways this is enlarged, and in two ways diminished. As it enlarges, the pressure of the outside air expands the elastic sacs of the lungs; as it diminishes, the air is pressed out again. Along with great increase of surface and great complexity of mechanism for moving the air go, as has been pointed out, a perfecting of the circulatory apparatus for bringing the blood to the respiratory surface, and a proportionate complexity of the nervous system for producing and regu- lating the necessary movements. It is to be kept in mind, however, that the respiratory apparatus only brings oxygen to the respiratory surface, and before the real respiration at the tissue-cell can take place the oxygen must be carried by the blood to the cell. This process we shall later discuss under the head of circulation. Now having seen how animals get the necessary oxygen we may next inquire how they obtain and make use of the equally necessary substances to be oxidized and to build the body out of, that is, their food. How. animals obtain and digest food.—Amceba eats without a mouth. It extends any part of its soft body over the little plant or animal it feeds upon. In many 60 THE ANIMALS AND MAN Protozoa, however, there is a definite mouth-place, as in Paramecium, where the food-particles are gathered to- gether in a little ball by the cilia, and then pushed through the body-wall. The body of the fresh-water hydra (see Chapter XIII), incloses a digestive cavity, the mouth being but an opening to this. In the higher animals we find mouths arranged for cutting, filing, sucking, crushing, gnawing, grinding, chiseling, piercing, sawing; in fact almost every device one could think of for working in wood, bone, shell, flesh, liquid, soft and hard material of many forms. To understand the process of digestion some knowledge of the nature of food substances is necessary. In con- sidering the production of energy and making of body material we saw that the same substances provided for both. In fact whatever the form of food, animal or plant, the elementary substances are the same, being conveniently classified into two great groups, organic and inorganic substances. Inorganic food substances are water and certain minerals of which common salt is one. Organic food substances are of three kinds or groups. The first group, called the proteids, of which the white of egg is an example, forms a large part of the tissues of animals; the second group is made up of the fats and oils; the third, known as the carbohydrates, consists of the starches and sugars. Digestion consists in changing all these substances into soluble form so that they can be absorbed into the body, circulate with the blood, if there be any, and then pass into the living cells for their use. This change is ac- complished by certain liquids called digestive fluids. The digestive apparatus varies like other parts of the animal organism, being very simple in some forms and very com- plex in others. In Amceba the food-particles are retained in spaces in the cell until they are digested. So in other ANIMAL PHYSIOLOGY 61 Protozoa. The simple digestive cavity of the hydra has been referred to. In the polyps and jelly-fishes (see Chap- ter XIII), this cavity is extended, the digestive surface being much increased by partitions, tubes, etc. Worms, crabs, and snails have a definite alimentary canal with certain parts set apart for special processes. In the vertebrates the digestive apparatus varies from a relatively simple straight tube to the very long and complex alimentary canal of the cow. ll this variety depends much on the nature of the food of the individual animal, and the processes necessary to turn it into body material. We have now to consider that process which has to do with carrying oxygen and food from the respiratory and digestive surfaces to all parts of the body. This process is the circulation, and the organs for performing it com- pose the circulatory system. How the blood circulates.—It has already been shown that increase of size and activity in animals necessitates blood and a means of circulating it through the body. The uses of the circulation are: to bring oxygen from the respi- ratory surface to every cell, to take carbon dioxide from every cell to the respiratory surface, to carry digested food substances from the absorbing surface of the alimentary canal to every cell, and, further, to remove from every cell the injurious and waste substances formed by its activity to where they may be either excreted from the body or dis- posed of in some other way. Circulation is accomplished by the moving of a liquid through a system of tubes and spaces channeling the whole body. In the very smallest and most sluggish of animals there is no circulatory system. In those which are of compara- tively large size and very active, and which therefore need a great amount of energy, much oxygen and food must be supplied. Also a large amount of waste substance is pro- duced which must be removed. In such animals the cir- 62 THE ANIMALS AND MAN culatory system is found to be highly developed and to work with great efficiency. In Amceba, because of its small size and the constant flowing of the body-substance, there is no circulatory system. In some Protozoa the contents of the body-cell seem to have a definite movement, but there are no such organs as heart and blood-vessels. In most animals we find blood and a system of tubes and spaces for it to circulate in. In some, as the insects (fig. 21), only part of the circulatory system consists of definite tubes; these open into loose ill-defined spaces in the body-cavity. In these spaces the blood moves gradually throughout the animal, but not so definitely and quickly as in others where the blood runs in definite vessels. In the earthworm there is no “heart” as in higher animals, but the blood- Fis. 21. Diagram of vessel along the dorsal line and some “#wlatory system of 5 : a young dragon-fly; of its branches around the sides have inthe middle is the muscular walls and “‘beat’” by a wave chambered dorsal of contraction running toward the Yess! with single ‘ artery; the arrows head. In insects the dorsal blood- indicate the direction vessel beats in the same way, but of _blood- currents. generally more vigorously. Inthe young (After Kolbe.) larva of a mosquito or nymph of a May-fly with transparent skin the beating can be easily seen under the microscope. In molluscs there is a well-developed heart; it can be well seen in the fresh-water mussel. The crustaceans also have a heart. This can be seen at work in a water-flea under the micro- scope, or can be readily demonstrated in a crab or crayfish killed with chloroform or ether. In vertebrates the blood circulates in a definite system of tubes through which it is pumped by a heart. The fishes ANIMAL PHYSIOLOGY 63 (fig. 22) have the heart consisting of two parts, with mus- cular walls, a single auricle and a single ventricle. The auricle receives the blood pouring from all the tissues of the body through the veins. It contracts and forces the blood into the ventricle. This then contracts and drives it into a short vessel called the ventral aorta, which gives of a branch artery for each gill-arch. The gill-arteries divide Fic. 22. Diagram of the circulatory system of a fish; v, ventricle; u, auricle. (After Parker and Haswell.) into capillaries in the gills, whence, after aeration, the blood is gathered by another artery and carried to the dor- sal aorta, from which branch arieries distribute it to the capillaries of the general body-tissues. From these it is gathered by the veins and carried back to the auricle to be- gin again. In the course of circulation the blood reaches every part of the body, picking up certain substances here, leaving others there, thus accomplishing the results already pointed out as the objects of the circulation. In the circulation of the higher vertebrates the most striking difference from that of the fish is in the structure of the heart, which adapts the circulation to lungs instead of gills, and in the more perfect control and regulation of the action of heart and blood-vessels by the nervous system. It may be asked how, since the blood remains in vessels during circulation, the tissue-célls refeive anything from it. The: blood. as such does. not reach. the tissue-cells. These 64 THE ANIMALS AND MAN are surrounded by a liquid, called lymph, which fills the spaces between them. The capillary blood-vessels run through this liquid and may not actually touch the cells themselves at all, or at only a few points. The walls - of the capillaries being very thin, however, the substances needed by the cells diffuse from the blood through the walls into the liquid and thence to the cells themselves. On the other hand, substances from the cells—carbon dioxide and other waste matters—diffuse into the liquid and from this to the blood through the capillary walls. In fact each tissue- cell feeds, like certain one-celled animals, by absorption from a liquid medium, but by means of the circulation this liquid has a prepared food constantly brought to it. We may ask how the blood carries the oxygen. In the vertebrates part of the blood consists of little bodies called the red corpuscles. The color of these is due to a chemical substance called hemoglobin. This has the capacity of ab- sorbing oxygen at the lungs and of giving it up to the tissues. How animals know things and control their motions.— Thus far we have considered the mechanisms animals have for motion and for obtaining oxygen and food. A more difficult but more interesting subject is how motions take place in the animal, how they are guided, how they are stopped; in short, how the whole conduct of the life of the animal is carried on. To understand better what these processes consist of, let us consider as an example the life of a common bird. We know that after hatching from the egg it takes food, learns the notes of the parent bird, learns to fly, learns to fight or to avoid enemies, all these including motions guided by sight, hearing, touch, and smell. On the approach of winter it migrates to the south; in spring it returns, chooses a mate, builds a nest, and rears young to which it teaches in turn the ways of bird life. While the full explanation df these processes is far from being reached, and while we cannot here discuss them at length, ANIMAL PHYSIOLOGY 65 yet we may at least examine some of the parts of the body specially concerned with these processes. In the higher animals they are determined and directed by means of the sense-organs and the nervous system. In vertebrates the special senses, as they are called, are those of sight, hearing, smell, taste, touch, cold, heat, and one called the muscular Sunfish. Toad. Snake. Sparrow. Mouse. Fic. 23. Diagram of brains of vertebrates; olf. l., olfactory lobes; cbr., cerebrum; md. b ..“midbrain (optic lobes); cbi., cerebellum; med. ob., medulla oblongata; sp. cd., spinal cord. sense. A part of the eye known as the retina is specially sensitive to light; in the internal ear there are certain cells which are affected by sound vibrations; in the nasal passages there is a region in which are cells sensitive to odors; in the skin of the tongue are cells that react to sweet, sour, and bitter liquids; in various parts of the skin are cells sensitive to pressure, heat, and cold. These different kinds of cells affected by different influences are called sense-cells. Now what the animal sees, hears, touches, etc., deter- mines its motions, and we find that the sense-cells are con- nected with the muscles by means of the nervous system. Through this connection light, heat, sound, etc., guide muscular action. The nervous system of a vertebrate (fig. 24), consists of a central portion, the brain (figs. 23, 25), and spinal cord, from 66 THE ANIMALS AND MAN which branches called nerves extend in pairs; the nerves then branch and branch again until their divisions reach every part of the body in the shape of very numerous white threads, tco small to be detected by the naked eye. These very small nerve-threads or fibers end at last in connection with cer- tain of the tissue-cells. All the sense-cells of the retina, Fic. 24. Central nervous system of a dog. | (After Ritzema-Bos.) ear, nose, tongue, and skin are connected with minute nerve-fibers as are also all the muscle-fibers. Now all the nerve-fibers from both sense-cells and muscle-cells run to the central portions of the nervous system, the brain and spinal cord, and are there in some way definitely connected with one another, thus making pathways over which every- thing that affects the eye, ear, and other sense-organs may affect the muscles. The nervous system of all vertebrates is on the same general plan, being, however, less complex in the lower forms. All animals with a definite nervous system have nerve-fibers connecting both sense-cells and muscle-cells with certain central parts. They differ, however, in the arrangement of these parts. And since they differ also in muscular arrangement, and in the kind and position of the sense-organs, the arrangement of the nerve-fibers connecting ANIMAL PHYSIOLOGY 67 muscles and sense-organs with these central parts differs accordingly. In the worms, crustacea, and insects, which have much the same body-plan, the central nervous system (fig. 26) con- sists of a chain of ganglia (small nerve-centers) along the ventral portion of the body, this chain being connected at the anterior end by a cord on each side of the gullet, with a large head ganglion which stands in the position of the vertebrate brain. In the starfishes and sea-urchins, the central nerv- ous system has the form of a ring with radiating branches, but with no head ganglia. In sea-anemones and jellyfishes it is somewhat sim- ilar, but is less distinctly set apart from: the other tissue-cells. In the one-celled animals we recognize Fic. 25. Brain of a cat, dor- no trace of a nervous system any sal surface; I, olfactory more than we do of a muscular fpheres, IL cerebellum; OT bony system. In Amoeba. the IV, medulla oblongata. whole cell is in a weak way sensi- (After Reighard and Jen- tive to light, heat, jars, odors, acids, mings.) alkalis, and the various other things that affect the sense-organs of higher animals. The cell as a whole conducts the effects of these to all its parts and the response of the animal is slow and indefinite. In recent years a great deal of careful observation and experimentation has been done on the behavior of the simplest animals. The conclusions of the naturalists who have done this work are not yet in sufficient harmony to make possible any satisfactory generalizations, but it seems certain that much of the behavior of the simpler animals is determined and controlled by agencies outside of the body. 68 THE ANIMALS AND MAN Fic. 26. Diagrams showing fundamental structure of types of several animal phyla: 1, sea-anemone; 2, starfish; 3, worm; 4, centiped; 5, clam; 6, honeybee; 7, salamander. In each figure the central nervous system is indicated by the black lines. (After Haeckel.) ANIMAL PHYSIOLOGY 69 Light, for example, has always a definite influence on certain simple animals compelling them to move in certain ways and to continue moving until they have arranged their bodies in a fixed position with regard to the direction of the light rays. Certain chemical substances, as well as gravita- tion, magnetism and other external agencies exert similarly definite influences. These externally controlled movements are called tropisms. Various other animal motions are of such a definite character, always recurring in exactly the same way under the same conditions of stimulation, that they are called reflexes; and these also go to show, as do the tropisms, that much of the behavior of the simpler animals, and even more or less of that of the higher animals, is beyond the control of the animal itself. As we proceed upward in the animal scale we find a gradual grouping into definite positions of a number of cells that are specially sensitive to the different influences acting on the organisms, and along with this definite groups of muscular cells and definite nerve pathways for impulses to pass from the sensitive to the motor cells, and more and more complex connections of groups with groups. In the highest organisms we have sense-organs which make us exactly acquainted with the outside world; we have brain, spinal cord, and nerves, which receive the impulses from these and turn them through the muscles into all the motions our bodies are capable of; besides we have all those wonder- ful processes included under the names instinct, memory, and reason. The special senses and their organs.—The organs of sight, the eyes, are the only organs of special sense generally conspicuous and unmistakably recognizable when present. In the vertebrates the eyes, ears, nose, and taste organs are always situated on the head, but in the invertebrates the sense-organs corresponding to these are often scattered over the body, and certain other organs are found which from 70 THE ANIMALS AND MAN their structure seem to be sense-organs although we are by no means sure what kind of sense they serve. In some of the lower animals, as the polyps, there are on the skin certain sense-cells, either isolated or in small groups that are not limited to a single special sense. They seem to be stimulated not alone by the touching of foreign substances, but also by warmth and light. These simple sense-cells from which the more complex or special ones may develop are called primitive or generalized sense- organs. The tactile sense or sense of touch is the simplest and most wide-spread of the special senses, with the simplest organs. The special organs are usually simple hairs or papilla connecting with a‘nerve. They may be distributed pretty evenly over most of the body or may be mainly con- centrated upon certain parts in crowded groups. Many of the lower animals have projecting parts, like the feeling tentacles of many marine invertebrates, or the antenne (feelers) of crabs and insects, which are the special seat of the tactile organs. Among the vertebrates the tactile organs are either like those of the invertebrates, or are little sac-like bodies of connective tissue in which the end of a nerve is curiously folded and convoluted. These little touch-corpuscles (fig. 27) lie in the cell layer of the skin, : covered over thinly by the cuticle. Some- aged foe oe times they are simply free, branched nerve- of man; x, nerve, endings in the skin. In either case they (Greatly magni- are especially abundant in those parts of a ane a the body which can be best used for feel- ing. In man the finger-tips are thus es- pecially supplied, in certain tailed monkeys the tip of the tail, and in hogs the end of the snout. The taste organs are much like the tactile organs except ANIMAL PHYSIOLOGY q1 that the special taste cell must be exposed or covered only by a thin osmotic membrane, so that small particles of the substance to be tasted can come into actual con- tact with it. The taste organs (fig. 28) of man and the other air-breathing animals are located in the mouth or on the mouth parts. It is also necessary that the food substance to be tasted be dissolved. This is accomplished by the fluids poured into the mouth from the salivary glands. With the lower Fic. 28. Papilla with taste buds (¢. b.) aquatic animals it is not sone Pa eked cai improbable that taste or- gans are situated on other parts of the body besides the mouth, and that taste or a sense akin to it is used not only to test food substances but also the chemical character of the fluid medium in which they live. Smelling and tasting are closely allied, the one testing substances dissolved, the other substances vaporized. The organs of the sense of smell are, like those of taste, simple nerve-endings in papillae or pits. By smell animals can discover food, avoid enemies, and find their mates. With the strictly aquatic animals the sense of smell is probably but little developed. There is little opportunity for a gas or vapor to reach them, and only as gas or vapor can a sub- stance be smelled. With these animals the sense of taste must take the place of the olfactory sense. But among the insects, mostly terrestrial animals, there is an extraordinary development of the sense of smell. Insects must depend on smell far more than on sight or hearing for the discovery of food, and for becoming aware of the presence of their enemies and the proximity of their mates and companions. The organs of smell of insects are situated principally on 72 THE ANIMALS AND MAN the antenne or feelers (fig. 29), a single pair of which is borne on the head of every insect. That many insects have an amazingly keen sense of smell has been shown by numerous experiments, and is constantly proved by well-known habits. Fic. 29. The antenna of a carrion beetle, with the terminal three seg- ments enlarged and flat- tened and bearing many “‘smelling-pits.” (Much enlarged; photo-micro- graph by Geo. O. Mitch- ell.) for perceiving or being stimu- lated by vibrations ranging from 16 to 40,000 a second—that is, Hearing is the perception of cer- tain vibrations of bodies. These vi- brations give rise to waves—sound- waves as they are called—which proceed from the vibrating body in all directions, and which, coming to an animal, stimulate the special au- ditory organs, which transmit this stimulation along the auditory nerve to the brain, or nerve ganglion, where it is translated as sound. These sound-waves come to animals usu- ally through the air, or, in the case of aquatic animals, through water, or through both air and water. The organs of hearing are of very com- plex structure in the case of man and the high- er verte- brates. Our ears (fig. 30), which are adapted Fic. 30. Diagram of the in- ternal part of the human ear; for hearing all those sounds pro- y, external opening; b, bones duced by vibrations of a rapidity of the ear; J, labyrinth; ¢, not less than 16 to a second nor greater than 40,000 to a second jy.) cochlea or ‘snail shell”; 7, auditory nerve. (After Head- ANIMAL PHYSIOLOGY 73 —are of such complexity of structure that many pages would be required for their description. But among the lower or less highly organized animals the ears, or audi- tory organs, are much simpler. In most animals the auditory organs show the common characteristic of being wholly composed of, or having, Fic. 31. The auditory organ of a locust (Welanoplus sp. ). The large clear part in the center of the figure is the thin tympanum, with the auditory vesicle (small, black, pear-shaped spot) and auditory ganglion (at left of vesicle and connected with it by a nerve) on its inner sur- face. A spiracle at the side of the tympanum allows air to pass into a chamber behind the tympanum so that the air pressure is the same on both outer and inner surfaces of the tympanum. (Greatly magni- fied; photo-micrograph by Geo. O. Mitchell.) as an essential part, a small sac filled with liquid in which one or more tiny spherical hard bodies called otoliths are held. This auditory sac is formed of, or lined internally by, auditory cells, specialized nerve-cells, which often bear 74 THE ANIMALS AND MAN delicate vibratile hairs. Auditory organs of this general character are known among the polyps, the worms, the crustaceans, and the molluscs. Recent studies seem to show that the otoliths have a special use as organs which help the animal to keep its equilibrium. In the common crayfish the “ears” are situated in the basal segment of the inner antenne or feelers. They consist each of a small sac filled with liquid, in which are suspended several grains of sand or other hard bodies. The inner surface of the sac is lined with fine auditory hairs. The sound-waves coming through the air or water outside strike against this sac, which lies in a hollow on the upper or outer side of the antenne. ‘The sound-waves are taken up by the contents of the sac and stimulate the fine hairs, which in turn give this stimulus to the nerves which run from them to the principal. auditory nerve and thus to the brain of the crayfish. Among the insects other kinds of auditory organs exist. The com- mon locust or grasshopper has on the upper surface of the first abdominal segment a pair of tympana or ear-drums (fig. 31), composed simply of the thinned, tightly-stretched chitinous cuticle of the body. On the inner surface of this ear-drum there are a tiny auditory sac, a fine nerve leading from it toa small auditory ganglion lying near the tympanum, and a large nerve leading from this ganglion to one of the larger ganglia situated on the floor of the thorax. In the crickets and katydids, insects related to the locusts, the auditory organs or ears are situated in the fore legs. Certain other insects, as the mosquitoes and other midges or gnats, undoubtedly hear by means of numerous delicate hairs borne on the antenne. The male mosquitoes have many hundreds of these long, fine antennal hairs, and on the sounding of a tuning-fork they have been observed to vibrate strongly. In the base of each antenna there is a most elaborate organ, composed of fine chitinous rods, and accompanying nerves and nerve-cells whose function it is to ANIMAL PHYSIOLOGY "5 take up and transmit through the auditory nerve to the brain the stimuli received from the external auditory hairs. Not all animals have eyes. The moles, which live under- ground, insects and other animals that live in caves, and the deep-sea fishes which live in waters so deep that the light of the sun never comes to them, have no eyes at all, or have eyes of so rudimentary a character that they can no longer be used for seeing. But all these animals have no eyes or only rudimentary ones because they live under conditions where eyes are useless. They have lost their eyes by degen- eration. There are, however, many animals that have no eyes, nor have they or their ancestors ever had eyes. These are the sim- plest, most lowly organized animals. Many, perhaps all eyeless animals, are, however, capable of distin- guishing light from darkness. They rye. 32. Simple eye of a are sensitive to light. An investiga- jellyfish. (Greatly magni- tor placed several individuals of °4 after Hertwig.) the common, tiny fresh-water polyp (Hydra) in a glass cylinder the walls of which were painted black. He left a small part of the cylinder unpainted, and in this part of the cylinder where the light pene- trated the Hydras all gathered. The eyeless maggots or larve of flies, when placed in the light will wriggle and squirm away into dark crevices. They are conscious of light when exposed to it, and endeavor to shun it. Most plants turn their leaves toward the light; the sunflower turns on its stem to face the sun. Light seems to stimulate organ- isms whether they have eyes or not, and the organisms either try to get into the light or to avoid it. But this is not seeing. The simplest eyes, if we may call them eyes, are not capable of forming an image or picture of external objects. They only make the animal better capable of distinguish- ing between light and darkness or shadow. Many lowly 96 THE ANIMALS AND MAN organized animals, as some polyps, and worms, have cer- tain cells of the skin specially provided with pigment. These cells grouped together form what is called a pig- ment-fleck, which can, because of the presence of the pig- ment, absorb more light than the skin-cells, and are more sensitive to the light. By such pigment-flecks, or eye- spots, the animals can detect, by their shadows, the passing near them of moving bodies, and thus be in some measure informed of the approach of enemies or of prey. Some of these eye-flecks are provided not simply with pigment but Fic. 33. Diagram of vertebrate ~~ E eye; ¢, choroid; 4, iris; J, lens; With a simple sort of lens that n, optic nerve; 7, retina; s, serves to concentrate rays of sclerotic. (From Kingsley.) light and make this simplest sort of eye even more sensitive to changes in the intensity of light (fig. 32). Most of the many-celled ani- mals possess eyes by means of which a picture of external ob- jects more or less nearly com- plete and perfect can be formed. There is great variety in the finer structure of these picture- forming eyes, but each consists essentially of an inner delicate A or sensitive nervous surface called Fic, 34. Part of cornea, show- the retina, which is stimulated by _ ing facets, of the compound light, and is connected with the ‘Y¢ 0! @ horse-fly. (Greatly . 3 magnified; photo-microgra- brain by a large optic nerve, and phy by Geo. O. Mitchell.) ANIMAL PHYSIOLOGY 77 of a transparent light-refracting lens lying outside of the retina and exposed to the light. These are the constant essential parts of an image-forming and image-perceiving eye. may make the whole eye an organ of ex- cessively complicated structure and of re- markably perfect seeing capacity. Our own eyes (fig. 33) are organs of extreme structural complexity and of high devel- opment, although some of the other ver- tebrates have undoubtedly a keener and more highly perfected sight. The crustaceans and insects have eyes of a peculiar character called com- pound eyes (figs. 34 and 35). In ad- dition most insects have smaller simple eyes. Each of the compound eyes is composed of many (from a few, as in certain ants, to as many as twenty- five thousand, as in certain beetles) eye elements, each eye element seeing largely independently of the others and seeing only a very small part of any ob- ject in front of the whole eye. All the small parts of the external object seen by the many distinct eye elements combine so as to form an image in mo- saic, that is, made up of separate small parts of the external object. If the head of a dragon-fly be examined it will be seen that two-thirds or more of the whole In most eyes there are other accessory parts which Fic.35. Section through a few facets and eye elements(ommatidia) of the compound eye of a moth; f, corneal facets; ¢. c, crystalline cones; ~, pigment; r, retinal parts; o. ., optic nerve. (Greatly magnified; after Ex- ner.) head is made up of the two large compound eyes, and with a lens it may be seen that the outer surface of each of these eyes is composed of many small spaces or facets, which are the out- er lenses of the many eye elements composing the whole eye. PART II THE LIFE-HISTORY OF ANIMALS CHAPTER VII MULTIPLICATION AND DEVELOPMENT Multiplication. We know that any living animal has parents; that is, has been produced by other animals which may still be living or be now dead or, as with Ameba, may have changed, by division, into new individuals. Individuals die, but before death, they produce other individuals like themselves. If they did not, their kind or species would die with them. This production of new animals constantly going on is called the reproduction or multiplication of animals. The process is well called multiplication, because each female animal normally produces more than one new individual. She may produce only one at a time, one a year, as many of the sea-birds do or as the elephant does, but she lives many years. Or she may produce hundreds, or thousands, or even millions of young in a very short time. A lobster lays 10,000 eggs at a time. Nearly nine millions of eggs have been taken from the body of a thirty-pound female codfish. As a matter of fact but very, very few of these eggs produce new animals which. reach maturity. From the 10,000 eggs produced by the lobster each year an average of but two new mature lobsters is produced. There is always a struggle for food and for place going on among animals, for many more are produced than there are food and room for, and so of all the new or young animals , 79 80 THE ANIMALS AND MAN which are born the great majority are killed before they reach maturity. In a later chapter more attention will be given to this great struggle for life. In the preceding paragraph it has been stated that “we know that any living animal has parents; that is, has been produced by other animals which may still be living or be now dead.” This is a statement, however, which has found complete acceptance only in modern times. It is a familiar fact that a new kitten comes into the world only through being born; that it is the offspring of parents of its kind. But we may not be personally familiar with the fact that a new starfish comes into the world only as the production of parent starfish, or that a new earthworm can be produced only by other earthworms. But naturalists have proved these statements. All life comes from life; all organisms are produced by other organisms. And new individuals are produced by other individuals of the same kind. That these statements are true all modern observations and investigations of the origin of new individuals prove. But in the days of the earlier naturalists the life of the microscopic organisms like Ameba and Paramecium, and even that of many of the larger but unfamiliar animals, was shrouded in mystery. And various and strange beliefs were held regarding the origin of new individuals. Spontaneous generation.—The ancients believed that many animals were spontaneously generated. The early naturalists thought that flies arose by spontaneous generation from the decaying matter of dead animals. Frogs and many insects were thought to be generated spontaneously from mud, and horse-hairs in water were thought to change into water-snakes. But such beliefs were easily shown to be based on error, and have been long discarded by zoologists. But the belief that the microscopic organisms, such as bacteria and infusoria, were spontaneously generated in stagnant water or decaying organic liquids was held by MULTIPLICATION AND DEVELOPMENT 81 & some naturalists until very recent times. And it was not so easy to disprove the assertions of such believers. If some water in which there are apparently no living organisms, however minute, be allowed to stand for a few days, it will come to swarm with microscopic plants and animals. Any organic liquid, as a broth or a vegetable infusion, exposed to the air for a short time becomes foul through the presence of innumerable microscopic organisms. But it has been certainly proved that these organisms are not spontaneously produced in the water or organic fluid. A few of them enter the water from the air, in which there are always greater or less numbers of spores of microscopic organisms. ‘These spores germinate quickly when they fall into water or some organic liquid, and the rapid succession of generations soon gives rise to the hosts of bacteria and one-celled animals which infest all standing water. If all the active organisms and inactive spores in a glass of water are killed by boiling the water, and this sterilized water be put into a sterilized glass, and this glass be so well closed that germs or spores cannot pass from the air without into the sterilized liquid, no living animals will ever appear in it. We know of no instance of the spontaneous generation of animals, and all the animals whose life-history we know are produced by other animals of the same kind. Simplest multiplication and development.—The sim- plest method of multiplication and the simplest kind of development shown among animals are exhibited by such simple animals as Ameba and Paramecium. This method we have already studied. The production of new in- dividuals is accomplished by a simple division or fission of the body (a single cell) into two practically equivalent parts. The only change necessary for the young or new Ameba to become like its parent, is that of simple growth to a size about twice its present size. The development here is reduced to a minimum. Just as the simplest animals per- 82 THE ANIMALS AND MAN form the other life-processes, such as taking and digesting food, breathing and feeling, in an extremely primitive simple way, so do they perform the necessary life-process of re- production or multiplication in the simplest way shown among animals. In the case of Paramecium the process of multiplication is slightly more complex than that of Ameba in the fact that sometimes before the simple fission of the body takes place the interesting phenomenon of conjugation occurs. If the two conjugating individuals differ at all—and they always do differ, because no two individual animals, al- though belonging to the same species, are exactly alike— the new individual, made up of parts of each of them, will differ slightly from both. Nature seems intent on making every new individual differ slightly from the individual which precedes it. And the method of multiplication which Nature has adopted to produce the result is the method which we have seen exhibited in its simplest form in the case of Paramecium—the method of having two individuals take part in the production of a new one. The development of the new Paramecia is a little more complex than that of Ameba. Not only must the new Paramecium grow to the size of the original one, but it must develop those slight, but apparent, modifications of the parts of its body which we can recognize in the full- grown, fully developed Paramecium individual. A new mouth-opening must develop on the new individual formed of the hinder half of the original Paramecium and new cilia must be developed. And the recent studies of a careful naturalist have shown that altogether the new Parameecia undergo considerable change during their growth to full size. Thus there is a slight advance in complexity of development, just as there is in complexity of structure in Paramecium as compared with Ameba. In the many-celled animals this complexity of development is carried to an extreme.. MULTIPLICATION AND DEVELOPMENT 83 Birth and hatching—When a young animal is born alive, it usually resembles in appearance and structure the parent, although of course it is much smaller, and requires always a certain time to complete its development and be- come mature. A young kangaroo or opossum is carried for some time after its birth in an external pouch on the mother’s body and is a very helpless animal. A young kitten is born with eyes not yet opened and must be fed by the mother for several weeks. On the other hand young Rocky Mountain sheep are able to run about swiftly within a few hours after birth. Most animals appear first as eggs laid by the mother. This is true of the birds, the reptiles, the fishes, the insects, and most of the hosts of invertebrate animals. This egg may be cared for by the parent as with the birds, or simply deposited in a safe place as with most insects, or perhaps dropped without care into the water as with most marine invertebrates. The young animal which issues from the egg may at the time of its hatching resemble the parent in appearance and structural character (although always much smaller) as with the birds, some of the insects, and many of the other animals. Or it may issue in a so- called larval condition, in which it resembles the parent but slightly or not at all, as is the case with the gill-bearing, legless, tailed tadpole of the frog or the crawling, wingless, wormlike caterpillar of the butterfly, or the maggot of the house-fly. Life-history—Any animal which hatches from an egg has undergone a longer or shorter period of development within the egg-shell before hatching. The development of an animal from first germ-cell to the time it leaves the egg, for example, the development of the embryo chick from the first cell to time of hatching, is called its embryonic development; and the development from then on, for ex- ample, that of the chick to adult hen or rooster, or that of 84 THE ANIMALS AND MAN tadpole to frog, is called the post-embryonic development. Beginning students of animals cannot study the embryonic development (embryology) of animals readily, but they can in many cases easily follow the course of the post-embryonic development, and this study will always be interesting and valuable. CHAPTER VIII MOSQUITOES AND CATERPILLARS In the following* studies of insect life-histories the growth and development of the insects from hatching to maturity can be readily observed in the schoolroom. The particular insects chosen are selected because they can be easily ob- tained and reared indoors, and because they present especially interesting changes in their development. But other insect life-histories may be observed, either completely or in part, if it is so desired. Various caterpillars and chrysalids can be kept alive and watched as they develop into moths or butterflies, and various grubs that live in the ground can be kept until they become beetles. Flesh-flies may be allowed to lay their eggs on decaying meat, and the hatching of the maggots, their change into brown seed-like pupx, and the final emergence from these of the blue and green flies all carefully noted. MOSQUITOES The eggs and hatching.—Mosquitoes’ eggs are usually laid in small blackish masses, which float on the surface of water. (In the case of some species the eggs are laid in groups of only a few, or even deposited singly.) These sooty egg-masses are composed of a single layer of slender elongate eggs standing on end and loosely fastened to- *Most of the work outlined in this chapter, as also that of the succeeding chapter, can be done only in the spring or summer, so that this part of the book although devoted to a subject which should logically be treated imme- diately after,—if indeed not before—the structure and general physiology, may be postponed until after the next part (classification) is studied. 85 86 THE ANIMALS AND MAN gether to form a narrow, irregular, little raft, slightly concave on the upper surface, and wholly unsinkable. They are to be found on small pools of standing water, or in water- ing-troughs or exposed barrels—wherever indeed there is quiet or stagnant water. These egg-masses should be brought into the schoolroom and kept in glass tumblers, with some of the water on which they are found floating (fig. 36). Examine an egg-mass with a hand lens to note the arrangement and appearance of the eggs. How many are there in the mass? The eggs should be kept under pretty constant observation for hatching is likely to take place soon after they are brought into the schoolroom. Ordinarily they hatch in from twelve to twenty-four hours after they are laid. They may, of course, hatch at night. But if the hatching occurs during the day it can be easily observed. From which end of the egg does the young mosquito emerge? It may not be easy to find the egg-masses on the pools; in that case the wrigglers or larvee (described in the next paragraph) should be sought for and brought into the schoolroom in tumblers or jars containing water taken from the pool in which they are found. The life-history can be studied from this point on. The tumblers must not be kept in places too cool or dark, or the young mosquitoes will develop abnormally slowly. The ‘“wrigglers” or larve.—The newly hatched mosquito bears no resemblance to the familiar winged fly which we call by that name. In this first stage of its life, or second stage, if we call the egg stage the first, it is familiarly known as a “wriggler,’ but is called larva by naturalists. The active young stage of any insect which differs markedly from the fully developed or mature one is called the larval Stage. The larve swim actively about. By what means do they swim? If they cease swimming do they sink deeper in the water or rise to the surface? Is the body of the larva denser MOSQUITOES AND CATERPILLARS 87 or less dense than the water? that is, is it heavier or lighter than water? Note that some of them hang quietly from the surface, and that each one comes occasionally to the surface and rests there for a while to breathe. Every ani- mal has to breathe; that is, to take up oxygen from the air and to give off. from its body carbon di- oxide (CO,). There is always some air mixed with or dis- solved in water, and most aquatic animals—fishes for example—have special structures called gills which enable them to take up this dissolved oxygen, and thus to breathe under wa- ter. But the gills of most mosquito larve are too un- developed, and therefore they have to come occasional- ly to the surface to breathe. Fic. 36. A mosquito, Culex sp.; showing eggs (on surface of the water), larvae (long and slender, in the water), pupa (large-headed at surface), and adult (in the air). (About three times natural size; from living specimens.) Examine with a hand lens one of the larve in a watch- glass of water. Distinguish the head end of the body; note the eyes (two small black spots), the feelers, or antenne, 88 THE ANIMALS AND MAN and a pair of tufts or brushes of hair on the head which vibrate rapidly and constantly. These brushes by their vibration create currents in the water setting toward the mouth, which lies between them, and thus bring food to it. This food consists of any tiny animalcules and microscopic bits of organic matter in the water. Are there any legs or wings? Examine the posterior end of the body and note its division into two parts—one the end of the hind body or abdomen, the other a breathing-tube projecting from the next to last body-ring. Make a drawing of the larva, showing and naming all these parts. Observe again the larve in the jar. When they hang from the surface note that only the tip of the breathing- tube reaches it. Note the vibration of the mouth-brushes. The larve feed busily for most of the time. If they sink in the water when they stop “wriggling,” i.c., swimming, how is it that they can rest quietly at the surface? For this reason: the tip of the stem-like breathing-tube pro- jects slightly above the surface when the wriggler comes up to breathe, so that the expanded edges of its mouth are caught by the tense surface film and the wriggler’s body being but slightly heavier than water, is thus supported or suspended by the film. It is easier to prove the existence of this film than to explain it. If you carefully lay a clean needle on the surface of the water it will not sink, although much denser, i.e., heavier than water, but will be supported by the surface film. If you fill a tumbler to its brim you can still add more water carefully and so heap it up above the level of the brim. This is because the surface film ex- tending over the water from edge to edge holds it in place. If you dip your finger in and then lift it up the water does not all run off, but a large drop will remain hanging to your finger. The tense surface film holds the little mass to- gether in the form of a drop. The mosquito larva takes advantage of the surface film and is able to keep itself at MOSQUITOES AND CATERPILLARS 89 the surface when breathing by hanging from it. Water- striders and the numerous little flies which run quickly and safely about on the surface of the water are supported by the film. Their feet make little dents or depressions on the water’s surface, but do not break through. It is probable that the movements of the feeding-brushes also help to keep the wriggler at the surface, as the wrigglers seem to be able to balance themselves, i. e., keep from sinking, in the water by these movements. Observing the larve or “‘wrigglers” from day to day it will be noted that they increase in size, that is, are growing. They breathe and feed and swim and grow. And some keenly observant pupil may see that they occasionally cast their skin, or moult. That the larve do moult one or more times is certain; how many times, however, has not yet been found out for many kinds. The pupz.—After several days—just how many each pupil should determine for himself—the long slender larve enter upon another stage in the mosquito’s life called the pupal stage, and the young mosquitoes are now called pupe. In this stage the head end is large and bulbous, the hind body is usually curled underneath the head, and the creature spends most of its time floating at the surface. It can swim, and does so when disturbed, by a peculiar straightening and folding of its body. When it stops swimming what happens to it? In what way must the pupa differ from the larva in its relation to the density of water? Examine with a hand lens one of the pupe in a watch- glass of water. Note the two tubes or horns which project upwards from the back or dorsal part of the bulbous head end of the body, and the pair of flaps at its posterior tip. What are the dorsal tubes for? With what do they cor- respond in the larvee? The mouthless pupa takes no food and usually floats quietly at the surface. Why then does it swim at all? What is the use of the flaps at the end of the go THE ANIMALS AND MAN body? Note the indications of legs and wings folded on the under side of the head end. Make a drawing showing and naming these parts. In two or three days the pupa suddenly changes into the full-fledged winged mosquito. That is, the cuticle or outer skin wall of the body splits along the middle line of the back, and the winged mosquito emerges through this open- ing. What part of the body appears first? What parts next? While the mosquito is emerging the pupal skin serves as a raft upon which the soft-bodied damp insect is partly supported until its wings and legs are unfolded and dried and hardened, and it is ready to fly away. Some- times the body rests simply on the surface of the water, being supported by the surface film. This transformation of pupa into fully developed mosquito can be readily ob- served, and each pupil should see. it. The winged or imago stage.—The mosquito is now full-grown and fully developed; and in this fully developed stage it is called an imago to distinguish it from larva and pupa. It is of course the same insect, a mosquito all the time, but we commonly apply that name only to the winged stage or imago. A few of the winged mosquitoes should be killed in a “‘killing-bottle”? (see Appendix I), and examined under a hand lens. Two kinds may be distinguished; one with many long hairs on their feelers or antenne, the other with fewer and much shorter hairs; the latter are females, the ones with bushy antenne males. These antennz are the mosquito’s organs of hearing. How many wings has the mosquito? How many pairs of legs? Can you find behind the wings a pair of delicate little knobbed processes projecting from the body? ‘These are called balancers and they aid the mosquito in directing its flight. Note the long, piercing and sucking beak (fig. 37) by means of which the mosquito gets its food, which is either the blood of animals or the sap of plants. The male mosquitoes MOSQUITOES AND CATERPILLARS Or never (or very rarely) suck blood. On each side of the beak, and arising at its base, is a pair of feelers or palpi, presumably organs for smelling and tasting, or which at least aid in determining the character of the food. These palpi are as long as the beak in the males, but less than half as long as in the females. What are the large black spots on the head? Make a drawing of a mosquito, showing and naming these parts. If some of the mosquitoes are kept alive in jars filled with water and covered with netting the females may per- haps lay eggs on the surface of the water. But it is not at all certain that they will; indeed, they seem to lay eggs Fic. 37. Beak of female mos- quito, dissected to show the only rarely when thus kept piercing needle-like parts and in confinement. If a slice of their sheath; max, p., the max- banana be put in the jar the illary palpi, or feelers of the mosquitoes may be seen to suck mouth, (oreatly maguiied:) the sap from it, and they may be kept alive for many days if given fresh banana every three or four days. If the egg- laying occurs, the life-history of our mosquitoes is com- pleted. A new cycle is about to begin. Distribution of mosquitoes.—Mosquitoes are distributed all over the world, being found in enormous numbers in arctic regions and on high moutain ranges as well as in the tropics, and in swamps and marshy valleys. About four hundred and fifty species, or different kinds, of mos- quitoes are known, nearly seventy of which are found in North America. Besides the irritation caused by their “bite,” i.e., piercing with the sucking beak, it has been 92 ; THE ANIMALS AND MAN proved that mosquitoes are the conveyers and distributors of the germs of malarial fever (see Chapter XII). Only certain kinds of mosquitoes, however, are malaria-carriers. These all belong to the genus Anopheles; they may be distinguished by the possession of spotted wings, as most of the innocuous kinds have the wings clear. There are a few innocuous or non-malarial kinds with spotted wings, how- ever, but no malaria-carrying kinds with wholly clear wings. The malaria-bearing kinds have the maxillary palpi long in both male and female, while in the other kinds the females have short palpi (fig. 37). Other kinds of mosquitoes are certainly the distributors of the germs of yellow fever, and the same kinds convey a terrible tropical disease called elephantiasis. The most effective remedy against mosquitoes is to pour a little kerosene on the surface of the pool in which the larve and pupe live. The kerosene will spread out and form a thin, oily film over the surface of the water, and no winged mosquito will be able to emerge alive through this film, contact with kerosene being fatal to almost all insects, and and especially so just after a moult. For full accounts of the life of mosquitoes see ‘‘Mosquitoes,’’ by Dr. L. O. Howard or “Mosquito Life” by Evelyn G. Mitchell. CATERPILLARS Caterpillars are the larva of moths and butterflies. While larva is the entomologist’s name for the young of any kind of insect that has a complete metamorphosis, most persons call the larve of different kinds of insects by different names, as grubs for the larve of beetles, maggots for those of many flies, wrigglers for those of mosquitoes, slugs for those of saw-flies and caterpillars for those of moths and butterflies. Most caterpillars are readily distinguishable by the five pairs of short, blunt, fleshy abdominal legs which they possess in addition to the three pairs of jointed thoracic legs. MOSQUITOES AND CATERPILLARS 93 The different kinds also are often easily recognizable by well-marked color patterns, or by coverings of colored hair or the presence of conspicuous tubercles and the like. They may be found from late spring to early fall usually busily feeding in their favorite plants. “The best hunting grounds are the sides of country roads, the edges of woods, Fic. 38. Larva of the achemon sphinx moth, Philampelus achemon. (Natural size; after Lugger.) half-cleared fields and gardens. Low fresh second growths of oak, poplar or elm will pay investigation. . . . A low growth of wild cherry is almost sure to yield a harvest.” Virginia creeper, sassafras, bayberry, hop-vines, appletrees, nettles, milkweeds and wild carrot are all favorite feeding grounds of butterfly caterpillars. The important thing to note at the time of collecting a live caterpillar, which you wish to rear indoors, is the kind of plant it is feeding on. For these are the best leaves to bring in to it. Indeed some kinds of caterpillars will 94 THE ANIMALS AND MAN eat the leaves of only certain few kinds of plants. Indoors the live caterpillars should be kept in clean cages (see Appendix II for directions for making cages) and given plenty of fresh food. They will then eat, grow, moult, pupate and finally turn into perfect moth or butterfly. The observations to be made on the caterpillars are of P ss, Fic. 39. Larva of the violet-tipped butterfly, Polygonia interrogationis, pupating. (Slightly enlarged; photograph from life by the author.) two general categories: (1) observations of structure; (2) observations of behavior. ‘To record the first make drawings; for the second make notes. Of structural characteristics note the segmental make-up of the body and number of the segments; number, position and character of the legs, the mouth-parts, eyes and antenne on head; presence and arrangement of hairs or tubercles, and position and number of spiracles (breathing pores). MOSQUITOES AND CATERPILLARS 95 All of these points may be shown in a single drawing. A colored drawing should be made showing the colors and color pattern. Among the characteristics of behavior to be noted are the manner of walking,- manner of eating, attitudes when disturbed or frightened, and the processes of moulting and pupating. If an inch worm (caterpillar of a Geometrid moth) can. be found, note its different methods of walking and the dif- ference in the number of legs. Is there a relation between the different number of legs and the different mode of walking? Some caterpillars go into the ground to pupate, some spin silken cocoons, some simply attach themselves freely exposed. The spinning of cocoons should be watched closely and described fully in the notes. A fully spun cocoon should be cut open several days after it is made, in order to see the chrysalid within. If some caterpillars have burrowed into the ground one or two should be dug up after several days in order to see what has happened. If the chrysalid has been made freely exposed note whether its colors and patterns are such as would tend to conceal it if it were hanging against bark or among leaves. Make a drawing of the chrysalid showing and naming all the parts that can be observed. Look for spiracles and for the wings, legs, mouth-parts and antenne of the future moth or butterfly. Make drawings and notes describing in detail the issuance of the moth or butterfly from the chrysalid case. Pay special attention to the unfolding and expanding of the wings. By what means does this expansion probably take place? Make drawings of the fully expanded moth or butterfly showing not only its general shape but all of its parts. Note all of the details in which it differs from the caterpillar. These include number, character and arrangement of the 96 THE ANIMALS AND MAN segments, number and character of the legs, presence of the wings, difference of the wings, difference in antenne, eyes and mouth-parts, clothing of scales over wings and body, color and color patterns, etc. Fic. 40. Pupa or chrysalid of the violet-tipped butterfly, Polygonia in- terrogationis. (Slightly enlarged; photograph from life by the author.) There is no limit to the possibilities of pleasure and in- terest in the field study and collecting of moths and butter- flies. The study should include observations on their flight, their resting attitudes, their feeding habits, their play with each other, and their mating and egg-laying. Directions for collecting and preserving these and other insects will be found in Appendix II. Butterflies can be named by referring to some such book as Com- stock’s “How to Know the Butterflies,” Holland’s “The Butterfly Book,”” or Scudder’s ‘Everyday Butterflies.” The more common and conspicuous moths can be named from Holland’s “‘ The Moth Book.” CHAPTER IX FROGS AND BIRDS While the life-history of most of the backboned animals shows no such startling transformations or metamorphoses as that of the insects we have studied, yet among toads, frogs, and salamanders, forming the class of backboned animals known as amphibians or batrachians, there is an interesting and well-marked metamorphosis. A newly hatched bird is much smaller and weaker than its parents, its feathers are different, and it usually has to be cared for and fed for some time, but it is unmistakably birdlike in appearance, and its development to adult form is gradual and without startling changes. The same is true of kittens and puppies, or young lions or camels, and true, also, for the most part, of fishes and of snakes and lizards. But the young toad or frog, which we call tadpole, looks, and truly is, much more like a fish than like its parent, and therefore in its growth and development it undergoes a marked trans- formation. The eggs and hatching.—In the spring, April and May, the frogs and toads begin their croaking and trilling, and then is the time to look in the ponds for the eggs. Indeed the ponds had better be watched as soon as the ice goes out. Hunt in the shallow water along the banks. Toads’ eggs lie in long strings of a gelatinous, jelly-like substance, usually wound about submerged sticks or the stems of water-plants, while those of the frog are found in small bunches or masses of the jelly. They are small, shining, black, and bead- like, and in the toad strings are arranged in single rows. 97 98 THE ANIMALS AND MAN If they have been recently laid, the enclosing jelly mass will be clean and clear, but it soon becomes partly covered with fine mud, when the eggs are not so easily seen. Bring some egg-masses to the schoolroom and keep them in water in a light warm place but not in the direct sunlight. Examine the eggs several times a day, as hatching occurs in two or three days after they are laid. The developing embryo can be clearly seen through the transparent jel- ly. Watch for their first move- ments and note their change in form. Finally they wriggle out from the jelly mass and swim freely in the water, or attach themselves, by means of a little V-shaped sucker on the head, to some solid object. They are not like adult frogs or toads at all, but are the famil- iar little fish-like tadpoles (fig. 42). The tadpoles.—To rear tadpoles successfully in the school- room requires some pains. First, a proper little artificial pond must be made. Professor Gage, of Cornell University, who has sucessfully reared many broods, gives the following directions for caring for them: “To feed the tadpoles it is necessary to imitate nature as closely as possible. To do this a visit to the pond where the eggs were found will give the clue. Many plants are present, and the bottom will be seen to slope gradually from the shore. The food of the tadpole is the minute plant-life on the stones, the surface of the mud, or on the lic. 41. Garden toad. FROGS AND BIRDS 99 outside of the larger plants. Make an artificial pond in a small milk-pan, or a large basin or earthenware dish. Put some of the mud and stones and small plants in the dish, arranging all to imitate the pond, that is, so it will be shallow on one side and deeper on the other. Take a small pail of clear water from the pond to the schoolhouse and pour it into the dish to complete the artificial pond. The next Fic. 42. Tadpoles. (Photograph from life by Cherry Kearton; per- mission of Cassell and Co.) morning when all the mud has settled and the water is clear, put thirty or forty of the little tadpoles which hatched from the egg string, into the artificial pond. Keep this in the light, but not very long at any one time in the sun. “One must not attempt to raise too many tadpoles in the artificial pond or there will not be enough food, and all will be half-starved. While there may be thousands of tadpoles in a natural pond, it will be readily seen that, compared with the amount of water present, there are really rather few. “Every week, or oftener, a little of the mud, and =e 100 THE ANIMALS AND MAN a small stone covered with the growth of microscopic plants, and some water should be taken from the pond to the arti- ficial pond. The water will supply the place of that which has evaporated, and the mud and stones will carry a new supply of feed.” The tadpoles will begin to change very soon. Make a drawing of one just hatched from the egg, examining it with a hand lens. Note the gills on the sides of the neck, the V-shaped sucker on the head, and the absence of legs and eyes. Watch sharply for the first changes. What are they? It takes a tadpole about two months from the time of hatching to complete its development and hop out of the water as a little toad or frog. In this process of develop- ment the following changes occur: eyes appear; the gills are lost; four legs develop; the tail is gradually lost, and lungs are formed inside the body. The development of the lungs cannot be actually seen, but its course is made apparent by the behavior of the tadpoles. While at first they remain under the water nearly all the time, breathing by means of their gills the air dissolved in the water, as they grow older they come more and more often to the surface and gulp down air through the mouth. Lungs are developing, and are being more and more used for breathing air from the limitless supply above. Observe carefully the process of the disappearance of the tail. Does it drop off suddenly? Is it lost before the legs develop? Which pair of legs appears first? The order of their appearance differs in the toad tadpoles and the frog tadpoles; if both kinds are being reared determine this by observation. Make a drawing of a tadpole just after its legs appear, and compare with the drawing of the newly hatched tadpole; make also a drawing of a little toad or frog when it first finishes the tailed tadpole stage and hops out of the water. FROGS AND BIRDS 101 While the development of the tadpoles is going on in the schoolroom observations on the growth and changes of those in the natural ponds outdoors should be made. Does development go on more rapidly indoors than out? Where do the little toads and frogs go after they leave the outdoor ponds? Toads and frogs.—Adult toads and frogs are carniv- orous, instead of feeding on tiny plants as in their tadpole stage. They snap up all kinds of insects, worms, and snails; when full grown they will eat younger frogs, cray- fish, small turtles, and fish, and may also occasionally capture small birds. A few grown-up toads and frogs should be kept in the school- room in a box with at least one glass-side and covered over with netting. Keep a dish of water in the box, and the bottom covered with clean moist sand. Feed the toads live insects, worms, and snails, or bits of raw meat. How does the toad catch its prey or seize the offered food? Both toads and frogs do much good by destroying many insects. One observer, quoted by Professor Gage, reports that a single toad disposed of twenty-four caterpillars in ten minutes, and that another ate thirty-five celery-worms within three hours. This observer estimates that a good- sized toad will destroy nearly ten thousand insects and worms’ in asingle summer. The garden can have no more desirable animal inhabitants than toads; not only should they not be killed but it would be worth while to introduce them into flower and vegetable gardens where they are not naturally present. For a good account of tadpole-rearing see ‘The Life of a Toad,” by Professor S. H. Gage. Fic. 43. Garden toad. 102 THE ANIMALS AND MAN BIRDS The animals whose life-history we have so far studied do not take care of their young, though making certain provision for them nevertheless. The female mosquito, although an aerial creature, is careful to lay her eggs on the surface of water so that the young will find themselves at the moment of hatching in their proper element; the female moth or butterfly, although she never eats leaves her- self, always lays her eggs on the plants or trees where the young, on hatching, can find at hand their proper leaf food. Such is the habit of ‘all moths and butterflies. Some of them indeed take no food in their adult stage; others do, but this is always liquid nectar from flowers, or other sweet juices, and water, and their mouth-parts are formed into a long flexible, coiling, sucking proboscis. They could not eat green leaves if they would; and yet each moth and butterfly mother seeks out, at egg-laying time, that par- ticular plant, unknown to her as food, the green leaves of which, the young caterpillars must live upon; truly a re- markable instinct! But beyond this care in laying their eggs in suitable places the butterflies and moths have nothing to do with their young. And so it is with most of the lower or simpler animals, and with many of the vertebrates (backboned animals), most of the fishes for instance, the amphibians, and the reptiles. These animals pay little or no attention to their young after birth; indeed many of the lower ones die before the young are hatched, and those that do not may have gone a long distance away before that time. But among the higher vertebrates, the birds and mammals, and among a few particularly interesting invertebrates, as the social insects and others, the parents give much care and pro- tection to their young, building homes for them, providing them with food, and teaching them to help themselves. Almost all animal homes are built primarily for the pro- FROGS AND BIRDS 103 tection and housing of the young, although the parents, may, and during the rearing of the young, naturally do, largely live in them themselves. As an example of an ani- mal home, we may observe the construction of a bird’s nest, together with the egg-laying and incubation and the care of the fledglings. A bird’s nest.—In spring (Gy W7 iy Z YU fH times, find close to the school- room a pair of birds that have begun a nest. By keeping sharp watch in trees and bushes they will surely be found, though most birds hide their nests as effectively as possible. Robins are especially good birds to watch, because they are not easily frightened from their work,- because they build a large nest, and be- cause they gather their nesting materials mostly in the near vicinity of the nest. Because the robin’s nest is in a tree, Fic. 44. Nest of humming-bird, it may not be so easy to watch made of sycamore down, as the nest of some bird that (One-half natural size.) builds in hedges or bushes. Find a robin or other bird carrying a straw in its bill and trace it “home.” In observing the nest-building, egg-laying, and incu- bation try to answer the following questions: Do both birds take active part in building, or but one, and if one, which one, the male or female, and what does the other do? What materials are used? Is the nest composed chiefly of one kind of material, or nearly equally of several? What “tools” of the bird are used in building? When does build- Me Me S i NWA Uh MEY Y Y and early summer, the nesting- aN UY y/, Wy \AN OG 104 THE ANIMALS AND MAN ing begin? How long does it last? How soon after finish- ing the nest are the eggs laid? Are all the eggs laid at one sitting? Do both birds take part in incubation, i. e., sitting, or but one, and if but one, is it the male or female? What does the other do? How long before the eggs hatch? Do they all hatch at the same time? After hatching the care of the fledglings should be well Fic. 45. Oriole’s nest with skeleton of bluejay suspended from it; the bluejay probably came to the nest to eat the eggs, became entangled in the strings composing the nest, and died by hanging. (Photo- graph by S. J. Hunter.) watched. Do both parents bring food? How many times is food brought in one hour, or if so much time can be given to continuous watching, in two or three? What is the food? Is the nest cleaned? If so, how often? When are the first flying lessons given? How long do the young birds con- tinue to come back to the nest at night after they first leave it? FROGS AND BIRDS 105 Other incidents in the course of nest-building, incubation, and care of the young birds will certainly be noted if sufficient observation to answer the above questions is given. Attacks by cats and bluejays (fig. 45), disputes between the parent birds, accidents from high winds or other causes are all likely to enter into the course of nesting. And the behavior of the parent birds under such more or less unnatural cir- cumstances will be interesting to observe and record. While some pupils are watching a robin’s nest others should observe the nesting of other kinds of birds—the blue- bird, wren,. groundbird, catbird—any familiar kind that can be found at work. See Chapters XVII-XXI in Baskett’s “The Story of the Birds,” and Chapter VI in Chapman’s “‘Bird-life.” PART II DIFFERENT KINDS OF ANIMALS, THEIR CLASSIFICATION, HABITS AND SPECIAL RELATION TO MAN CHAPTER X THE CLASSIFICATION OF ANIMALS Basis and significance of classification.—It is the com- mon knowledge of all of us that animals are classified: that is, that the different kinds are arranged in the mind of the zoologist and in the books of natural histroy, in various groups, and that these various groups are of different rank or degree of comprehensiveness. A group of high rank or great comprehensiveness includes groups of lower rank, and each of these includes groups of still lower rank, and so on, for several degrees. For example, we have already learned that the toad belongs to the great group of back- boned animals, the Vertebrates, as the group is called. So do the fishes and the birds, the reptiles and the mammals or quadrupeds. But each of these constitutes a lesser group, and each may in turn be subdivided into still lesser groups. In the early days of the study of animals and plants their classification or division into groups was based on the re- semblances and the differences which the early naturalists found among the organisms they knew. At first all of the classifying was done by paying attention to external re- 107 108 THE ANIMALS AND MAN semblances and differences, but later when naturalists began to dissect animals and to get acquainted with the structure of the whole body, the differences and likenesses of inner parts, such as the skeleton and the organs of circulation and respiration, were taken into account. At the present time and ever since the theory of descent began to be accepted by naturalists (and there is practically no one who does not now accept it), the classification of animals, while still largely based on resemblances and differences among them, tells more than the simple fact that animals of the same group resemble each other in certain structural characters. It means that the members of a group are related to each other by descent, that is, genealogically. They are all the descendants of a common ancestor; they are all sprung from acommon stock. And this added meaning of classifica- tion explains the older meaning; it explains why the animals are alike. ‘The members of a group resemble each other in structure because they are actually blood relations. But as their common ancestor lived ages ago, we can learn the history of this descent, and find out these blood-relationships among animals only by the study of forms existing now, or through the fragmentary remains of extinct animals pre- served in the rocks as fossils. As a matter of fact we usually learn of the existence of this actual blood-relationship, or the fact of common ancestry among animals, by studying their structure and finding out the resemblances and dif- ferences among them. If much alike we believe them closely related; if less alike we believe them less closely related, and so on. So after all, though the present-day classification means something more, means a great deal more, in fact, than the classification of the earlier naturalists it is still largely based on and determined by resemblances and differences just as was the old classification. Some- times the fossil remains of ancient animals tell us much about the ancestry and descent of existing forms. For THE CLASSIFICATION OF ANIMALS 109 example, the present-day one-toed horse has been clearly shown by series of fossils to be descended from a small five-toed horse-like animal which lived in the Tertiary age. Importance of development in determining classifica- tion.—A very important means of determining the relation- ships among animals is by studying their development. If two kinds of animals undergo very similar development, that is, if in their development and growth from egg-cell to adult they pass through similar stages, they are nearly related. And by the correspondence or lack of correspon- dence, by the similarity or dissimilarity. of the course of development of different animals much regarding their relationship to each other is revealed. Sometimes two kinds of animals which are really nearly related come to differ very much in appearance in their fully developed adult condition because of the widely different life-habits the two may have. But if they are nearly related their developmental stages will be closely similar until the animals are almost fully developed. For example, certain animals belonging to the group which includes the crabs, lobsters, and cray- fishes, have adopted a parasitic habit of life, and in their adult condition live attached to the bodies of certain kinds of true crabs. As these parasites have no need of moving about, being carried by their hosts, they have lost their legs by degeneration, and the body has come to be a mere sac-like pulsating mass, attached to the host by slender root-like processes, and not resembling at all the bodies of their relatives, the crabs and crayfishes. If we had to trust, in making out our classification, solely to structural re- remblances and differences, we should never classify the Sacculina (the parasite) in the group Crustacea, which is the group including the crabs and lobsters and crayfishes. But the young Sacculina is an active free-swimming creature resembling the young crabs and young shrimps. By a study of the development of Sacculina we find that it is more rr0 THE ANIMALS AND MAN closely related to the crabs and crayfishes and the other Crustaceans than to any other animals, although in adult condition it does not at all, at least in external appearance, resemble a crab or lobster. Scientific names.—To classify animals then, is to deter- mine their true relationships and to express these relation- ships by a scheme of groups. ‘To these groups proper names are given for convenience in referring to them. These proper names are all Latin or Greek, simply because these classic languages are taught in the schools and colleges of almost all the countries in the world, and are thus intelligible to naturalists of all nationalities. In the older days, indeed, all the scientific books, the descriptions and accounts of animals and plants, were written in Latin, and now most of the technical words used in naming the parts of animals and plants are Latin. So that Latin may be called the language of science. For most of the groups of animals we have English names as well as Greek or Latin ones and when talking with an English-speaking person we can use these names. But when scientific men write of animals they use the names which have been agreed on by naturalists of all nationalities and which are understood by all of these natural- ists. ‘These Latin and Greek names of animals laughed at by non-scientific persons as “jaw-breakers,” are really a great convenience, and save much circumlocution and misunderstanding. AN EXAMPLE OF CLASSIFICATION. TECHNICAL NotE.—There should be provided a small set of bird- skins which will serve just as well as freshly killed birds, and which may be used for successive classes, thus doing away with the neces- sity of shooting birds. The birds suggested for use are among the commonest and most easily recognizable and obtainable. They may be found in any locality at any time of the year. The skins can be made by some boy interested in birds and acquainted with making skins, or by the teacher, or can be purchased from a naturalists’ sup- ply store, or dealer in bird skins. The skins will cost about 25 cents THE CLASSIFICATION OF ANIMALS III each. This example or lesson in classification can be given just as well of course with other species of birds, or with a set of some other kinds of animals, if the teacher prefers. Insects.are especially avail- able, butterflies perhaps offering the most readily appreciated resem- blances and differences, Species.—Examine specimens of two male downy wood- peckers (the males have a scarlet band on the back of the head). (In the western States use Gardiner’s downy woodpecker.) Note that the two birds are of the same size, have the same colors and markings, and are in all respects alike. They are of the same kind; simply two individuals of the same kind of animal. There are hosts of other individuals of this kind of bird, all alike. This one kind of animal is called a species. The species is the smallest* group recognized among animals. No attempt is made to distinguish among the different individuals of one kind or species of animal as we do in our own case. Examine a specimen of the female downy woodpecker. It is like the male except that it does not have the scarlet neck-band. But despite this difference we know that it belongs to the same species as the male downy because they mate together and produce young woodpeckers, male and female, like themselves. There are thus two sorts of individuals, male and female, comprised in each species of animal. A species is a group of animals comprising simi- lar individuals which produce new individuals of the same kind usually after the mating together of individuals of two sexes which may differ somewhat in appearance and structure. Examine a male hairy woodpecker and a female; (in western States substitute a Harris’s hairy woodpecker). Note the similarity in markings and structure to the downy. Note the marked difference in size. Make notes of meas- *The lesser group called variety, or subspecies, we may leave out of consideration for the present. tSome species of animals are not represented by male individuals; and in some all the individuals are hermaphrodites. 112 THE ANIMALS AND MAN urements, colors and markings, and drawings of bill and feet, showing the resemblances and the differences between the downy woodpecker and the hairy woodpecker. These two kinds of woodpeckers are very much alike, but the hairy woodpeckers are always much larger (nearly a half) than the downy woodpeckers and the two kinds never mate together. The hairy woodpeckers constitute another species of bird. Genus.—Examine now a flicker (the yellow-shafted or golden-winged flicker in the East, the red-shafted flicker in the West). Compare it with the downy woodpecker and the hairy woodpecker. Make notes referring to the differ- -ences, also the resemblances. The flicker is very differently marked and colored and is also much larger than the downy woodpecker, but its bill and feet and general make-up are similar and it is obviously a ‘‘woodpecker.” It is, however, evidently another species of woodpecker, and a species which differs from either the downy or the hairy. wood- pecker much more than these two species differ from each other. There are two other species of flickers in North America which, although different from the yellow-shafted flicker, yet resemble it much more than they do the downy and hairy woodpeckers or any other woodpeckers. We can obviously make two groups of our woodpeckers so far studied, putting the downy and hairy woodpeckers (together with half a dozen other species very much like them) into one group and the three flickers together into another group. Each of these groups is called a genus, and genus is thus the name of the next group above the species. A genus usually includes several, or if there be such, many, similar species. Sometimes it includes but a single known species. That is, a species may not have any other species resembling it sufficiently to group with it, and so it constitutes a genus by itself. If later naturalists should find other species re- sembling it they would put these new species into the genus THE CLASSIFICATION OF ANIMALS 113 with the solitary species. Each genus of animals is given a Greek or Latin name, of a single word. Thus the genus including the hairy and downy woodpeckers is called Dryobates; and the genus including the flickers is called Colaptes. But it is necessary to distinguish the various species which compose the genus Colaptes, and so each species is given a name which is composed of two words, first the word which is the name of the genus to which it be- longs, and, second, a word which may be called the species word. The species word of the yellow-shafted flicker is auratus (the Latin word for golden), so that its scientific name is Colaptes auratus. The natural question, Why not have a single word for the name of each species? may be answered thus: There are already known more than 500,000 distinct species of living animals; it is certain that there are no less than several millions of species of living animals; new species are being found, described and named constantly; with all the possible ingenuity of the wordmakers it would be an extremely difficult task to find or to build up enough words to give each of these species a separate name. This is not attempted. The same species word is often used for several different species of animals, but never for more than one species belonging to a given genus. And the names of the genera are never duplicated. (There are, of course, much fewer genera than species, and the difficulty of finding words for them is not so serious.) Thus the genus word in the two-word name of a species indicates at once to just what particular genus in the whole animal kingdom the species belongs, while the second or species word distin- guishes it from the few or many other species which are included in the same genus. This manner of naming species of animals and plants (for plants are given their scientific names according to the same plan) was devised by the great Swedish naturalist Linnzus in the middle of the eighteenth century and has been in use ever since, 14 THE ANIMALS AND MAN Family—Examine a red-headed woodpecker (Mela- nerpes erythrocephalus) and a sapsucker (Sphyrapicus varius) and any other kinds of woodpeckers which can be got. Find out in what ways the hairy and downy wood- peckers (genus Dryobates), the flickers (genus Colaptes), and the other woodpeckers resemble each other. Examine especially the bill, feet, wings and tail. These birds differ in size, color and markings, but they are obviously all alike in certain important structural respects. We recognize them all as woodpeckers. We can group all the wood- peckers together, including several different genera, to form a group which is called a family. A family is a group of genera which have a considerable number of common struc- tural features. Each family is given a proper name consisting of a single word. The family of woodpeckers is named Picide. We have already learned that resemblances between animals indicate: (usually) relationship, and that classify- ing animals is simply expressing or indicating these relation- ships. When we group several species together to form a genus we indicate that these species are closely related. And similarly a family is a group of related genera. Order.—There are other groups* higher or more com- prehensive than families, but the principle on which they are constituted is exactly the same as that already explained. Thus a number of related families are grouped together to form an order. All the fowl-like birds, including the families of pheasants, turkeys, grouse and quail, all obviously re- lated, constitute the order of gallinaceous birds called Galline. The families of vultures, hawks and owls con- stitute the order of birds of prey, the Rapiores, and the fami- lies of the thrushes, wrens, warblers, sparrows, black-birds, *Each of these higher groups has a proper name composed of a single word. In the case of no group except the species is a name-word ever duplicated. Each genus, family, order, or higher group has a name-word peculiar to it, and belonging to it alone, THE CLASSIFICATION OF ANIMALS 115 and many others constitute the great order of perching birds (including all the singing birds) called the Passeres. Class and branch.—But it is evident that all of these orders, together with the other bird orders, ought to. be combined into a great group, which shall include all the birds, as distinguished from all other animals, as the fishes, insects, etc. Such a group of related orders is called a class. The class of birds is named Aves. There is a class of fishes, Pisces, and one of frogs and salamanders, Batrachia, one of snakes and lizards called Reptilia, and one of the quad- rupeds which give milk to their young called Mammalia. Each of these classes is composed of several orders, each of which includes several families and so on down. But these five classes of Pisces, Batrachia, Reptilia, Aves and Mammals agree in being composed of animals which have a backbone or a backbone-like structure, while there are many other animals which do not have a backbone, such as the insects, the starfishes, etc. Hence these five backboned classes may be brought together into a higher group called a branch or phylum. They compose the branch of backboned ani- mals, the branch Vertebrata (now usually looked on as a sub-branch of the great branch Chordata); all the animals like the star-fishes, sea-urchins and sea-lilies which have the parts of their bodies arranged in a radiate manner compose the branch Echinodermata; all the animals like the insects and spiders and centipedes and crabs and crayfishes, which have the body composed of a series of segments or rings and have legs or appendages each composed of a series of joints or segments, make up the branch Arthropoda. And so might be enumerated all the great branches or principal groups into which the animal kingdom ‘is divided. TABLE OF BRANCHES AND CLASSES OF ANIMALS As the animals referred to in this book are not taken up in a rigorous systematic or classificatory order, but are 116 THE ANIMALS AND MAN grouped together to some extent rather according to simi- larities of habit or habitat, the following table of classifica- tion* of animals to branches and classes is introduced to show the relationships of the various large groups. Class Class Class Class Class Class Class Class Class Class Class Class Class Class Class Class Class Class Class Class Class Class KINGDOM ANIMALIA. Brancu I. PROTOZO/A. I. Rhizdp’oda. Il. Mycétozo’a. Ill. Mastigéph’ora. IV. Spérozd’a. V. Infusé’ria. Brancu II. PORIF’ERA. I. Porijera. Brancu III. CCELEN’TERA’TA (sé-lén-te-ra-ta). I. Hydroz0'a. II. Scyphézda (si-f5-26’-a). III. Actinozd’a. IV. Cténdph’ora (tén-dph’-o-ra). BrancH IV. PLATYHELMIN’THES. I. Turbella’ria. II. Trémato’da. III. Césté’da. Branco V. NEMATHELMIN’THES. I. Némato'da. Il. Acanthocéph’ala. Ill. Chetdg’natha (ké-tdg’-na-tha) Branco VI. TROCHELMIN’THES. I. Rottf’era. II. Dinéphi'lea. III. Gastrét/richa. Brancu VII. MOLLUSCOI’DA. I. Pélyz6'a. II. Phérd'nida. TIl. Bréchidp’oda.. *The classification here used is that adopted by Parker and Haswell’s Text-book of Zoology (1897). fll: Class IL. Class II. Class III. Class IV. Class “‘Vz. Class VI. Class VII. Class A Class II. Class III. Class IV. Class I. Class IT. Class ‘III. Class IV. Class Vz Class I. Class II. Class III. Class IV. Sub-branch Sub-branch Sub-branch THE CLASSIFICATION OF ANIMALS BrancH VIII. ECHINODER’MATA. Asteroi' dea. Ophiuroi’ dea. Echinoi’ dea. Holothurot' dea. Crinoi' dea. Cystot’ dea. Blastot' dea. Branco IX. ANNULA’TA. Chetop' oda (ké-t6p’o-da). Géphyré'a (jéf-e-ré’-a). Archt-annél'ida. Hirudin’ea. Branco X. ARTHROP’ODA. Crusta’cea. Onychoph’ ora (n-y-kéf’-o-ra). Myridp’ oda. Inséc’ta. Aréch'nida. Brancu XI. MOLLUS’CA. Pélecyp’ oda. Amphineu’ra. Gastrip’oda. Céphalip'oda. Branco XII. CHORDA‘TA. I. Adélochor’da. Class Adélochor'da. II. Urochor’da. Class Urochor'da. III. Vertebra’ta. Division A. Acré’nia. Class Acra’nia Division B. Crania’ta. Class I. Cyclostém’ata. Class II. Pisces (pis-séz). Class III. Amphib’ia. Class IV. Reptil’ia Class V. A’ves. Class VI. Mémmal’ia, 117 CHAPTER XI THE SIMPLEST, OR ONE-CELLED, ANIMALS (PROTOZOA) Besides the Ameba, Paramecium and Vorticella (de- scribed in Chapter V) there are thousands of other kinds of Protozoa. Most of them live in water, but a few live in damp sand or moss, and some live inside the bodies of other animals as parasites. Of those which live in water some are marine, while others are found only in fresh-water streams and lakes. Form of body.—The Protozoa all agree in having the body composed for its whole lifetime of a single cell, * but they differ much in shape and appearance. Some of them are of the general shape and character of Ameba, sending out and retracting blunt, finger-like pseudopodia, the body- mass itself having no fixed form or outline but constantly changing. Others have the body of definite form, spherical, elliptical, or flattened, enclosed by a thin cuticle, and having a definite number of fine thread-like or hair-like protoplasmic prolongations called flagella or cilia. Many of the familiar Protozoa of the fresh-water ponds always have two whiplash- like flagella projecting from one end of the body. By means of the lashing of these flagella in the water the tiny creature swims about. Others have many hundreds of fine short cilia scattered, sometimes in regular rows, over the body- surface. The Protozoan swims by the vibration of these cilia in the water. There is no stagnant pool, no water standing exposed in *In some Protozoa a number of similar cells temporarily unite to form a colony, but each cell may still be regarded as an individual animal. 118 THE SIMPLEST, OR ONE-CELLED ANIMALS II9Q watering-trough or barrel which does not contain thousands of individuals of the one-celled animals. And in any such stagnant water there may always be found several or many different kinds or species. A drop of this water examined with the compound microscope will prove to be a tiny world Fic. 46. Sun animalcule, a fresh-water Protozoan with a siliceous skeleton and long thread-like protoplasmic prolongations. (From life.) (all an ocean) with most of its animals and plants one-celled in structure. A few many-celled animals will be found in it preying on the one-celled ones. There are sudden and violent deaths here, and births (by fission of the parent) and active locomotion and food-getting and growth and all of the businesses and functions of life which we are accustomed to see in the more familiar world of larger animals. 120 THE ANIMALS AND MAN Marine Protozoa.—One usually thinks of the ocean as the home of the whales and the seals and the sea-lions, and of the countless fishes, the cod, and the herring, and the mackerel. Those who have been on the seashore will recall the sea-urchins and starfishes and the sea-anemones which live in the tide-pools. On the beach there are the innumerable shells, too, each representing an animal which has lived in the ocean. But more abundant than all of these, and in one way more important than all, are the myriads of the marine Protozoa. Although the water at the surface of the ocean appears clear and on superficial examination seems to contain no animals, yet in certain parts of the ocean (especially in the southern seas) a microscopical examination of this water shows it to be swarming with Protozoa. And not only is the water just at the surface inhabited by one-celled animals, but they can be found in all the water from the surface to a great depth below it. In a pint of this ocean-water there may be millions of these minute animals. In the oceans of the world the number of them is inconceivable. And these myriads of Protozoa represent a great host of different species grouped in various families and orders. All of this wealth of animal life was unknown to the earlier naturalists, for but few of the Protozoa are visible without the aid of the microscope. Among all these ocean Protozoa none are more interesting than those belonging to the two orders Foraminifera (fig. 48) and Radiolaria. The many kinds belonging to these orders secrete a tiny shell (of lime in the Foraminifera, of silica in the Radiolaria) which encloses most of the one-celled body. These minute shells present a great variety of shape and pattern, many being of the most exquisite symmetry and beauty. The shells are perforated by many small holes through which project long, delicate, protoplasmic pseudopodia. These fine pseudopodia often interlace and fuse when they touch each other, thus forming a sort of THE SIMPLEST, OR ONE-CELLED ANIMALS protoplasmic network outside of the shell. I2r In some cases there is a complete layer of protoplasm—part of the body protoplasm of the Protozoan—surrounding the cell externally. When these tiny animals die their hard shells sink to the bottom of the ocean, and accumulate slowly, in incon- ceivable numbers, until they form a thick bed on the ocean floor. Large areas of the bottom of the Atlantic Ocean are covered with this slimy ooze, called Fora- minifera ooze or Radiolaria ooze, depending on the kinds of animals which have form- ed it. Nor is it only in present times that there has been a forming of such beds by the marine Pro- tozoa. All over the world there are thick rock strata composed almost exclusively of the fossil shells of these simplest animals. The chalk- beds and cliffs of England, and of France, Greece, Spain, and America, were made by Foraminifera. Where now is land were once oceans the bottoms of which have been gradually lifted above the water’s sur- face. Similarly the rock Fic. 47. Stentor sp.; a Protozoan which may be fixed, like Vorti- cella, or free-swimming, and which has the nucleus in the shape of a string or chain of bead-like bodies. The figure shows a single individual as it appeared when fixed, with elon- gate stalked body, and as it ap- peared when swimming about, with contracted body. (From life.) called Tripoli found in Sicily and the Barbadoes earth from the island of Barbadoes are composed of the shells of ancient Radiolaria. 122 THE ANIMALS AND MAN It is thus evident that the Protozoa are an ancient group of animals. As a matter of fact zoologists are certain that it is the most ancient of all animal groups. All of the animals of the ocean depend upon the marine Protozoa and the marine Protophyta, one-celled plants, for food. Either they feed on them directly, or prey on animals which in turn prey on these simplest organisms. A well- known zoologist has said: ‘“The food-sup- ply of marine ani- mals consists of a few species of micro- scopic organisms which are inexhausti- ble and the only Fic. 48. Rosalina varians,a marine Proto- source of food for all zoan (Foraminifera) with calcareous . : shell. (After Schultz.) the inhabitants of the ocean. The sup- ply is primeval as well as inexhaustible, and all the life of the ocean has gradually taken shape in direct dependence on it.” The marine Protozoa are the only animals which live independently; they alone can _ live or could have lived in earlier ages without depending on other animals. They must therefore be the oldest of marine animals. By oldest is meant that their kind appeared earliest in the history of the world, and as it is certain that ocean life is older than terrestrial life—that is, that the first animals lived in the ocean—it is obvious that the marine Protozoa are the most ancient of all animal groups. THE SIMPLEST, OR ONE-CELLED ANIMALS 123 As already learned in the examination of examples of one-celled animals, it is evident that life may be success- fully maintained without a complex body composed of many organs performing their functions in a specialized way. The marine Protozoa illustrate this fact admirably. Despite their lack of special organs and their primitive way of performing the life-processes, that they live success- fully is shown by their existence in such extraordinary numbers. They outnumber all other animals. The con- ditions of life in the surface-waters of the ocean are easy and constant, and a simple structure and simple method of performing the necessary life-processes are wholly ade- quate for successful life under these conditions. CHAPTER XII HUMAN DISEASES CAUSED BY ONE-CELLED ANIMALS Long ago when it was first discovered that various para- sitic worms lived in our bodies and were the causes of pain and injury and even certain diseases physicians rapidly came to believe that all our ills were in some way caused by such parasites, known or unknown. Later there came a reaction against this belief as the search for the supposed parasites causing various diseases was unsuccessful in re- vealing them; but again with the later discovery, by means of perfected microscopes and methods of investigation, of bacterial germs in the body tissues the parasite or germ theory of disease was rehabilitated, and this time to endure. These first known and first studied ‘‘germs’’ were all bacteria, which are extremely small, simple, one-celled plants. They are indeed probably the simplest of all living plants. But with the continued study of germs and con- tagious and infectious diseases it was found that certain of these diseases were produced not by bacteria or bacilli but by one-celled microscopic animals, organisms belonging to the branch Protozoa, or simplest animals. So today just as we recognize that typhoid, cholera and tuberculosis are diseases caused by the presence and growth in our body of bacteria, we recognize that malaria, sleeping sickness, re- lapsing fever and other related diseases are caused by the presence and growth of Protozoa. A marked difference between the bacteria-caused and the Protozoa-caused diseases is the manner of the development and of the inoculation of the disease germs. While bacteria 124 DISEASES CAUSED BY ONE-CELLED ANIMALS | 125 have a very simple sort of life-history, the disease-producing Protozoa have usually a very complicated life-history and one that requires two kinds of hosts for its completion. The bacteria or bacilli that cause typhoid fever for example, multiply in the body by simple division repeated indefi- nitely, forming generation after generation of bacilli all alike and of the same habits. The Protozoa that cause malaria multiply for a number of generations in the body, somewhat as the bacteria do, but then gradually cease multiplying and either die or lie more or less inert in the blood until they are sucked up with some of this blood into the stomach of a mosquito when they renew their active life and their process of multiplication but in a way very different from their former way. ‘The very shape and appearance of the germs become so changed that they could not be recognized as belonging to the same kind if the actual process of the changes had not been clearly observed. In the mosquito’s stomach some of the little round in- active bodies suddenly put forth five or six long slender lash-like processes that break off and go swimming about like little snakes. These find some of the inactive bodies which have become somewhat swollen and fuse with them and the new body formed by this fusion becomes active and moves toward the wall of the stomach and there burrows into this wall as far as its outer coating. Here the parasite comes to rest and begins to grow rapidly until it forms a little nodule on the outer surface of the stomach. Inside this nodule the body stuff of the parasite divides into many hundred minute spindle-shaped bodies. Finally the walls of the nodule, which now projects into the body-cavity of the mosquito, break and the hundreds of new activé germs escape into the blood of the insect which flows freely all through its body-cavity. From the blood they migrate forward into the neck and head and finally lodge in the salivary glands where they remain. 126 Transmitted to Human Blood when Mosquito THE ANIMALS AND MAN 2: s. . We), 3s. Q) > Some may be taken into the stomach \ 4 — of the Mosquito when Development of it bites 6 Parasite in ~ 0 8 49 Human Blood 7 5. 5G), S bites RO in the Mosquito @ iw fff tn Bod { fy i Cavity of Mosq, or" Jo yoeworg ur qWeudoys } "Ny a? g % f a Fic. 49. Diagram to illustrate the life-history of the malarial parasite. 1 is a red blood-corpuscle, 2 to 7 shows the development of the parasite in the corpuscle, a b ¢ d and a’ b’ c’ and e the development of the para- site in the stomach of the mosquito, f g h i the development in the capsule on the outer wall,of the stomach of the mosquito, & in the salivary gland. DISEASES CAUSED BY ONE-CELLED ANIMALS 127 When a mosquito “bites,” that is, pierces the skin with its needle-like mouth-parts, so as to suck blood, it always pours a little of the fluid from the salivary glands into the wound. The reason for this is not certainly known, but the fluid, perhaps, keeps the blood from coagulating and thus from refusing to flow. However, one of the results of this habit is to inoculate the bitten person with the germs of Fic. 50. Diagrammatic figure of stages in the development of the malaria- producing Haem ba (Plasmodium) in a red blood-corpuscle of the human body. malaria, for some of the many quiet little spindle-shaped germs flow into the blood with the salivary fluid. As soon as they enter the blood they become active and attach themselves to the red blood-corpuscles and burrow into them. As they work their way into the corpuscles they change their shape gradually, getting shorter and thicker, until by the time a germ is well lodged within a blood-corpuscle it is nearly spherical. 128 THE ANIMALS AND MAN The germ now feeds and.grows at the expense of the corpuscle. It may become nearly as large as the whole corpuscle. Then its body stuff divides into about six parts, the corpuscle breaks down, and the six new germs escape Fic. 51. Malarial mosquito, Anopheles maculipennis, on the wall. (Photo graph from life by R. W. Doane.) into the blood to find new blood-corpuscles to attack. This kind of simple multiplying goes on for a number of generations but ceases after a while, and the germs of the last generation lie inert in the blood until they can be taken into a mosquito’s body. Then a new life-cycle is started, according to the processes already described. This, in brief and most general terms, is the story of the relation of the minute Protozoan animals called Haematozoa, DISEASES CAUSED BY ONE-CELLED ANIMALS 129 or, popularly, malarial germs, with man and the mosquito. Not all kinds of mosquitoes—and over a hundred species of mosquitoes live in the United States—carry malaria germs. In only a few kinds, certain ones belonging to the spotted- winged genus Anopheles, can the malarial germs live and multiply. But it is difficult for the non-expert to tell one kind of mosquito from another and as the malaria-spreading kinds are scattered over the whole country, all mosquitoes should be avoided or fought. How mosquitoes live is told in Chapter VIII and how to fight them in Chapter XV. The way in which quinine cures malaria is by its power of killing the germs when they are in our blood. But we do not know that they are there until a great many have been produced by their rapid method of multiplication, and then it takes some time for the quinine to make headway against them. We should be saved much suffering by preventing their getting a lodgment into the body at all. As the germs are not created in the mosquito’s body but only get into it by the sucking up of blood by the insect from some person already suffering from the disease, another way of fighting malaria is to prevent mosquitoes from having access to malarial patients, in other words to isolate and quarantine from mosquitoes any person suffering from malaria. While malaria in America is not looked on as a fatal disease—although in fact about 10,000 persons die each year from its effects—elsewhere in the world, as in the. Mediterranean countries and especially in India, it is a very terrible disease indeed, carrying off hundreds of thousands, even millions of victims every year. In some of these countries, notably in Italy, mosquito fighting is done on a large scale under governmental control and expense. The malarial fevers are the principal diseases which in our own country are produced by one-celled animals living in our bodies, But elsewhere in the world other even more "130 THE ANIMALS AND MAN serious diseases are caused by Protozoan germs. The terrible sleeping sickness of Africa is one of these and, as with malaria, the germs are spread from man to man by a blood-sucking insect. This is not the mosquito but a larger heavier fly called the ¢se-tse, which is rather like a small horse-fly in general appearance. Yellow fever is also almost certainly caused by a Protozoan parasite, which is ie distributed exclu- sively by mosqui- toes. Several infec- tious diseases of domestic animals are caused by Pro- tozoa. The best known of these in this country is the Texas or splenic cattle fever, the germs of which pass part of their life in the bodies of ticks Fic. 52. Texas fever tick, Margaropus an- and are distributed ia lata adult not fully gorged. by them from ani- mal to animal. These germs, called Piroplasma, have the interesting power of entering the eggs in the body of the female tick so that when the young ticks hatch from these eggs, which are laid on the ground when the old ticks drop off from the cattle upon which they have been holding while sucking their blood, these young ticks are already inoculated with germs. When cattle are attacked by these young ticks they become inoculated with the fever by the escape of the germs from the bodies of the ticks into their blood. The characteristic common to all these Protozoa-caused DISEASES CAUSED BY ONE-CELLED ANIMALS 131 diseases that they are disseminated by insects in whose bodies the germs live for part of their life and undergo a special part of their multiplication is one that distinguishes them from the diseases caused by bacteria. However, several of the bacterial diseases are undoubtedly partly spread by insects, as cholera and typhoid fever by house- flies, plague by fleas, etc. But the germs do not have to live in the insects’ bodies in order to complete their life-history. However, the germs of some bacterial diseases can be, and are, taken into the stomachs of the insects and passed out of the body alive and virulent. The bacilli of both typhoid fever and cholera have been found in “flyspecks,” which are the excrement from the alimentary canal of the fly. CHAPTER XIII THE INVERTEBRATES The invertebrate or backboneless animals include all of the great branches, or phyla, into which the animal king- dom is divided, except one, the branch Chordata. Ac- cording to our table of animal classification (see pp. 116, 117) there are twelve of these invertebrate branches, one of which, the Protozoa, or one-celled animals, we have already briefly discussed. Included in the other eleven branches are all the sponges, sea-anemones, corals and jellyfishes, all the animals we commonly know as worms and a host of less familiar worm-like others, all the starfishes, sea-urchins and sea-cucumbers, the crabs, the centipedes, the insects and spiders and all the shell-fish and other creatures grouped together as molluscs. The backboneless animals out- number by far in species and in individuals the backboned animals. The insects alone, which compose but a single class, the Insecta, of the great branch Arthropoda, include a greater number of kinds than all the other animal classes and branches together. But just the same the interest of most of us is held more by the backboned animals, the fishes, batrachians, reptiles, birds and animals; those animals with which our own bodies may be most readily compared and among whom we find our most valuable and entertaining and friendly companions and aids in life. However, the five hundred thousand known species, more or less, of invertebrate animals now living include a host of kinds whose lives are of great interest and of great immediate importance to us. Some of them help build 132 THE INVERTEBRATES 133 islands on which men live; others live parasitically in our bodies to our great discomfort and danger; many are per- sistent enemies of our crops and domestic animals. Finally, all in their structure, their physiology, their development and growth, their extraordinary adaptations to the con- ditions of their life, their marvelous modes of distribution, their beauty of color and pattern, and symmetry of outline, appeal to that inborn love of knowledge in us, as subjects to study, admire and enjoy. Sponges.—A bath or slate sponge is simply the skeleton, or part of it, of a sponge animal. In life all of this skeleton is in- closed or covered by a soft, tough mass of sponge flesh. Sponges are fixed, ex- cept when very young, when they swim freely about. They are found at all depths and in all seas, grow- ing especially abun- dantly in the Atlan- Fic. 53. A simple sponge, Graniia sp.; tic Ocean and the at right a longitudinal section, showing Mediterranean. A the simple body-cavity. (One-half natu- very few kinds live in ral size; after Jordan and Kellogg.) fresh water, being found in lakes, rivers, and canals, in all parts of the world. The shape of the simplest sponges is that of a small vase, or nearly cylindrical cup, attached at its base, and having at the free end a large opening (fig. 53). But most sponges are very unsymmetrical and grow more like a low, compact, bushy plant than like the animals we are familiar with. The smallest sponges are only 1 mm, (1-25 in.) high, while the largest may be over 134 THE ANIMALS AND MAN a meter (39 in.) in height. In color they may be red, purple, orange, gray, and sometimes blue. Examine a bath sponge and note the holes in it. These Fic. 54. The skeleton of a glass sponge, composed of siliceous spicules; from Japan. (Natu- tal size.) are to let in and out the sea- water, in which float the minute bits of animal or plant sub- stance on which the sponge feeds. This water also brings oxygen for the breathing of the sponge, and carries away the carbon dioxide given off by it. But the sponge has no special organs, its soft flesh being able to digest food and take up oxygen without stom- ach or lungs. The living sponges are col- lected by divers, or are dragged up by men in boats with long- poled hooks or dredges. They are first killed by exposure to the air, and then thrown into tanks of water. Here the flesh decays away, leaving the tough, horny, or leathery skeleton, which, when cleaned, bleached, and _ trim- med, is ready for market. Some sponges have a lime and some a glass skeleton instead of a horny one, and the glass skeletons are often very beautiful (see fig. 54). All the sponges compose the animal branch called Porifera. Hydra.—One of the most interesting of the simple animals found in fresh-water ponds is Hydra (fig. 5s). Though THE INVERTEBRATES 135 very small compared with most animals we know, it is much larger than any of the Protozoa, being when expanded nearly one-fourth of an inch long. It is also not composed of a single cell but of hundreds of cells. It is one of the simplest of the many-cell- ed animals, i.e., Metazoa. a Hydra may be found at- : tached to bits of sticks, fe ge stones, and leaves in pools R : \ not too stagnant. There ye ee are two common kinds, hi “4 Sse one brown and one green. Specimens should be brought into the school- room alive, and kept in a dish of water in the light. To observe the habits of Hydra, examine a live specimen, attached to a bit of leaf or stick, in a watchglass, under the low power of a compound microscope, or with a good magnifier. Note the cylindrical body, attached at its base, Fic. 55. Hydra; note two tentacles catching an insect larva; note the and with a series of ten- budding young Hydra. (Natural tacles projecting from its size, one sixth of an inch high; from life.) free end. How many ten- tacles are there? They arise in a circle apout the mouth. Have some small water-fleas in the water and observe Hydra’s method of catching and eating food. Note that when it captures one of the water-fleas with its tentacles the flea soon ceases to struggle. It is paralyzed. On the tentacles are many extremely fine, little, stinging 136 THE ANIMALS AND MAN threads, which lie coiled up in small pockets until prey is captured, when they uncoil, shoot out, and sting. If Hydra catches an animal'too large to be crowded into its mouth it releases it. Note that Hydra can contract its tentacles and its whole body until it looks like a small egg with a rosette of short blunt fingers at one end. Sometimes Hydra may be seen with another much smaller one growing out from it (fig. 55). This is a new one, forming by the process of ‘‘budding.” It will grow and develop until about as large as the parent, when it will break off, and attaching itself elsewhere will begin an independent existence. Hydra has the interesting power of being able to regenerate itself if cut in two. In such a case each half will usually develop into a new com- plete Hydra. Sea-anemones, corals and jellyfishes.—The sea-anemones which are common in tide-pools, and the coral animals which live in tropic and sub-tropic oceans, have the same type of body as that shown by Hydra, but are much larger. When the tide is out, exposing the dripping seaweed-covered rocks, and the little basins are left filled with clear sea- water, the brown and green and purple “‘sea-flowers”’ may beseen fixed to the rocks by the base, with the mouth opening and circlet of slowly moving tentacles hungrily ready for food. Touch the fringe of tentacles with your finger-tip and feel how they cling to it. If it were a small animal, like a sea-snail, these deadly ten- tacles would hold it fast and slowly carry it into the mouth. Inside the body is a cylindrical hollow, which is really a primitive kind of stomach. But there is no heart nor brain nor lungs in this simple body. It is only a thick-walled sac, with the mouth surrounded by food- catching tentacles. The coral animals, or coral polyps, are simply a kind of sea-anemone which secretes in its otherwise soft body- THE INVERTEBRATES 137 wall a stony skeleton of carbonate of lime which persists after the polyp is dead. We know these animals chiefly by their skeletons, which we see in masses in collections, or made into ornaments. But in tropical oceans there are whole islands of coral, or long coral reefs fringing the shores of continents, formed by the skeletons of millions of polyps. For as they live closely massed together in great colonies their skeletons form solid stony banks. Coral islands have a great variety of form, but the elongated, circular, ring- shaped, and crescent forms predominate. In the Atlantic Ocean they are found along the coasts of Southern Florida, Brazil, and the West Indies; in the Pacific and Indian oceans there are great coral reefs on the coasts of Australia, Madagascar, and elsewhere; and certain large groups of inhabited islands, as the Fiji, Society, and Friendly Islands are almost exclusively of coral formation. There are over 2000 kinds of coral polyps known, and their skeletons vary much in appearance. Because of the suggestive appearance of some of these they have received common names, as the organ-pipe coral, brain coral, etc. The red coral of which jewelry is made grows chiefly in the Mediterranean Sea. It is gathered specially on the western coast of Italy, and on the coasts of Sicily and Sardinia. Most of this coral is sent to Naples, where it is cut into orna- ments. By walking along the sea-beach soon after a storm one may find many shapeless masses of a clear and jelly-like substance scattered here and there on the sand. These are the bodies or parts of bodies of jellyfishes which have been cast up by the waves. Exposed to the sun and wind they soon die or evaporate away to a small shrivelled mass. The flesh of a jellyfish contains hardly more than one per cent of solid matter, all the rest of it being water. Jellyfishes, although closely related to the fixed polyps, some indeed being the immediate offspring of them, have 138 THE ANIMALS AND MAN a body of quite different appearance. It corresponds in general to an umbrella or bell (fig. 56), around the edge of which are disposed numerous threads or tentacles (cor- responding to the tentacles of the polyp). The mouth- opening is at the end of a longer or shorter projection which hangs from the middle of the under side of the umbrella, Fic. 56. A jellyfish or medusa, Gonionema vertens, eating two small fishes. (Natural size.) like a short, thick handle. The body-cavity, or primitive stomach, extends out into the umbrella-shaped part of the body. By alternately clapping shut and opening the um- brella the jellyfish swims about. Jellyfishes occur in great numbers on the surface of the ocean, and are familiar to sailors under the name of “‘sea- blubs.”” Some live in the deeper waters; a few specimens THE INVERTEBRATES £30 have been dredged up from depths of a mile below the sur- face. They range in size from “umbrellas” or disks a few millimeters in diameter to disks of a diameter of two meters (24 yards). They are all carnivorous, preying on other small ocean animals, which they catch by means of their tentacles, provided with stinging-threads. The tentacles of some of the largest jellyfishes, “reach the astonishing length of 40 meters, or about 130 feet.’”’ Many of the jelly- fishes are beautifully colored, although all are nearly trans- parent. Almost all of them are phosphorescent, and when irritated some emit a very strong light. The so-called ‘‘colonial jellyfishes” are floating or swim- ming colonies of jellyfishes and polyps composed of many individuals closely joined. These individuals are all of one species, but are of different forms or kinds, each kind having a special function to perform in the life of the colony. For example, some individuals catch ali the food for the colony; some make the motions; some are especially sen- sitive to the presence of enemies or prey, and some produce all the young. These various individuals act like the separate organs of our own body. The beautiful Portu- guese ‘‘man-of-war” is one of these colonial jellyfishes. It appears as a delicate bladder-like float, brilliant blue or orange in color, usually about six inches long, and bearing on its upper surface, which projects above the water, a raised parti-colored crest, and on its under surface a tangle of various appendages, thread-like, with grape-like clusters of little bell- or pear-shaped bodies. Each of these parts is a specially modified individual, produced by budding from an original central polyp. The Portuguese man-of- war is very common in tropical oceans, and sometimes vast numbers swimming together make the surface look like a splendid flower-garden. The sea-anemones, corals, and jellyfishes compose the animal branch Celenterata. 140 THE ANIMALS AND MAN Starfishes and sea-urchins.—Among the most easily found and most readily recognized seashore invertebrates are the starfishes and sea-urchins, which belong to the animal branch called Echinodermata. Although these animals do not look at all alike, the starfishes having a body composed of Fic. 57. Starfishes of various kinds in a tide-pool on the Bay of Monterey, California; note two with five rays, three pentagonal, and two with many rays. (Photograph by the author, from living specimens in situ.) central disk and long rays or radiating arms, and the sea- urchins looking like spiny flattened balls, they are really closely related. In each the body, with its various organs, is built on a radiate plan of structure, the mouth being in the center of the under side and all the body parts radiating out from this center. THE INVERTEBRATES 141 If a starfish, either fresh or preserved in alcohol, can be had for examination, note that the body is covered by a a ~—» 2p » ™ = 32. 2-2 $.I-f 2-2 3-3 The mouth is bounded by fleshy lips. On the floor of the mouth is the tongue, which bears the taste-buds or papil- THE VERTEBRATES: MAMMALS 241 le, the organs of taste. The cesophagus is always a simple straight tube, but the stomach varies greatly, being usually simple, but sometimes, as in the ruminants and whales, divided into several distinct chambers. The intestine in vegetarian mammals is very long, being in a cow twenty times the length of the body. In the carnivores it is com- paratively short—in a tiger, for example, but two or three times the length of the body. The blood of mammals is warm, having a temperature of from 35° C. to 4o° C. (95° F. to 104° F.). It is red in color, owing to the reddish-yellow, circular, non-nucleated blood- corpuscles. ‘The circulation is double, the heart being com- posed of two distinct auricles and two distinct ventricles. Air is taken in through the nostrils or mouth and carried through the windpipe (trachea) and a pair of bronchi to the lungs, where it gives up its oxygen to the blood, from which it takes up carbon dioxide in turn. At the upper end of the trachea is the larynx or voice-box, consisting of several cartilages attaching by one end to the vocal cords and by the other to muscles. By the alteration of the relative position of these cartilages the cords can be tightened or relaxed, brought together or moved apart, as required to modulate the tone and volume of the voice. The kidneys of mammals are more compact and definite in form than those of other vertebrates. In all mammals except the Monotremes they discharge their product through the paired ureters into a bladder, whence the urine passes from the body by a single median urethra. Mammary glands, secreting the milk by which the young are nourished during the first period of their existence after birth, are present in both sexes in all mammals, though usually func- tional in the female only. The nervous system and the organs of special sense reach their highest development in the mammals. In them the brain is distinguished by its large size, and by the special 242 THE ANIMALS AND MAN preponderance of the forebrain or cerebral hemispheres over the mid- and hind-brain. Man’s brain is many times larger than that of all other known mammals of equal bulk of body, and nearly three times as large as that of the largest- brained ape. In man and the higher mammals the surface of the forebrain is thrown into many convolutions; among the lowest the surface is smooth. Of the organs of special sense, those of touch consist of free nerve-endings or minute tactile corpuscles in the skin. The tactile sense is especially acute in certain regions, as the lips and end of the snout in animals like hogs, the fingers in man, and the under surface of the tail in certain monkeys. All the other sense-organs are situated on the head. The organs of taste are certain so-called taste-buds located in the mucous membrane cov- ering certain papille on the surface of the tongue. The organ of smell, absent only in certain whales, consists of a ramification of the olfactory nerves over a moist mucous membrane in the nose. The ears of mammals are more highly developed than those of other vertebrates both in respect to the greater complexity of the inner part and the size of the outer part. A large outer ear for collecting the sound-waves is present in all but a few mammals. A tym- panic membrane separates it from the middle ear in which is a chain of three tiny bones leading from the tympanum to the inner ear, composed of the three semi-circular canals and the spiral cochlea. The eyes have the structure char- acteristic of the vertebrate eye, consisting of a movable eye- ball composed of parts through which the rays of light are admitted, regulated, and concentrated upon the sensitive expansion, retina, of the optic nerve lining the posterior part of the ball. The eye is protected by two movable lids. In almost all mammals below the Primates there is a third lid, the nictitating membrane. In some burrowing rodents and others the eye is quite vestigial and even con- cealed beneath the skin, THE VERTEBRATES: MAMMALS 243 Development and life-history.—All mammals except the Monotremes give birth to free young. The two genera of Monotremes produce their young from eggs hatched out- side the body; Tachyglossus lays one egg which it carries in an external pouch, while Ornithorhynchus deposits two eggs in its burrow. The embryo of other mammals develops in the lower portion of the egg-tube, to the walls of which it is intimately connected by a membrane called the placenta. (In the kangaroos and opossums, Marsupialia, there is no placenta.) Through this placenta blood-vessels extend from the body of the mother to the embryo, the young developing mammal thus deriving its nourishment directly from the parent. The duration of gestation (embryonic or prenatal develop- ment in the mother’s body) varies from three weeks with the mouse, eight weeks with the cat, nine months with the stag, to twenty months with the elephant. Like the birds, the young of some mammals, the carnivores for example, are helpless at birth, while those of others, as the hoofed mam- mals, are very soon able to run about. But all are nourished for a longer or shorter time by the milk secreted by the mammary gland of the mother. Habits, instinct, and reason.—Despite the wonderful ex- amples of instinct and intelligence shown by many insects and by the other vertebrates, especially the birds, it is among mammals that we find the highest development of these qualities and of reason. In the wary and patient hunting for prey by the carnivora, in the gregarious and altruistic habits of the herding hoofed mammals, in the highly devel- oped and affectionate care of the young shown by most mam- mals, and in the loyal friendship and self-sacrifice of dogs and horses in their relations to man, we see the culmination among animals of the development of the functions of the nervous system. In the characteristics of intelligence and reason man of course stands immensely superior to all other 244 THE ANIMALS AND MAN animals, but both intelligence and reason are too often shown ° by many of the other mammals not to make us aware that man’s mental powers differ only in degree, not in kind, from those of other animals. Pure instinct is hereditary, and purely instinctive actions are common to all the individuals of a species. Those actions which the individual could not learn by teaching, imitation, or experience are instinctive. ‘The accurate peck- ing at food by chicks just hatched from an incubator is purely instinctive. Purely instinctive also is the laying of eggs by a butterfly on a certain species of plant which may have to be sought for over wide acres, so that the caterpillars when hatched shall find themselves on their own special food- plant. Yet the butterfly never ate of this plant and will never see its young. Such elaborate instincts as these have been developed from the simplest manifestations of sensation and nervous function, just as the complex structures of the body have been developed from simple structures. The feeding and domestic habits and the whole general behavior of animals are extremely interesting subjects of observation and study. And such observation intelligently pursued will be of much value. The point to be kept ever in mind is that all animal habits are connected with certain conditions of life; that in every case there is an answer to the question “why.” This answer may not be found; in many cases it is extremely difficult to get at, but often it is simple and obvious and can be found by the veriest beginner. Classification.—The mammals of North America repre- sent eight orders. Three additional mammalian orders, namely, the Monotremata, including the extraordinary duck- bills (Ornithorhynchus) and a species of Tachyglossus in Australia and Tasmania; the Edentata, including the sloths, armadillos, and ant-eaters found in tropical regions; and the Sirenia, including the marine manatees and dugongs, are not represented (except by a single manatee) in North ‘ THE VERTEBRATES: MAMMALS 245 America. In the following paragraphs some of the more familiar mammals representing each of the eight orders represented in North America are referred to. The opossums (Marsupialia)—The opossum (Didelphys virginiana) is the only North American representative of the order Marsupialia, the other members of which are limited exclusively to Australia and certain neighboring islands. The kangaroos are the best known of the foreign marsupials. After birth the young are transferred to an external pouch, the marsupium, on the ventral surface of the mother, in which they are carried about and fed. The opossum lives in trees, is about the size of a common cat, and has a dirty-yellowish woolly fur. Its tail is long and scaly, like a rat’s. Its food consists chiefly of insects, although small reptiles, birds, and bird’s eggs are eaten. When ready to bear young the opossum makes a nest of dried grass in the hollow of a tree, and produces about thirteen very small (half an inch long) helpless creatures. These are then placed by the mother in her pouch. Here they remain until two months or more after birth. Probably all the North Ameri- can opossums found from New York to California and espe- cially common in the Southern States belong to a single species, but there is much variety among the individu- als. The rodents or gnawers (Glires).—The rabbits, porcu- pines, gophers, chipmunks, beavers, squirrels, and rats and mice compose the largest order among the mammals. They are called the rodents or gnawers (Glires) because of their well-known gnawing powers and proclivities. The special .arrangement and character of the teeth are characteristic of this order. There are no canines, a toothless space being left between the incisors and molars on each side. There are only two incisor teeth in each jaw (rarely four in the upper jaw), and these teeth grow continuously and are kept sharp and of uniform length by the, gnawing on hard substances 246 THE ANIMALS AND MAN and the constant rubbing on each other. The food of rodents is chiefly vegetable. Of the hares and rabbits the cottontail (Lepus nuttalli) and the common jack-rabbit (L. campestris) are the best known. ‘The cottontail is found all over the United States, but shows some variation in the different regions. There are several species of jack-rabbit, all limited to the plains and mountain regions west of the Mississippi River. The food of rabbits is strictly vegetable, consisting of succulent roots, branches, or leaves. Rabbits are very prolific and yearly rear from three to six broods of from three to six young each. There are two North American species of porcupines, an Eastern one, Erethizon dorsatus, and a Western one, E. epixanthus. ‘The quills in both these species are short, being only a few inches in length, and are barbed. In some foreign porcupines they are a foot long. They are loosely attached in the skin and may be readily pulled out, but they cannot be shot out by the porcupine, as is popularly told. The little guinea-pigs (Cavia), kept as pets, are South American animals related to the porcupines. The pocket gophers, of which there are several species mostly inhabiting the central plains, are rodents found only in North America. They all live underground, making extensive galleries and feeding chiefly on bulbous roots. The mice and rats constitute a large family of which the house-mice artd rats, the various field-mice, the wood-rat (Neotoma pennsylvanica) and the muskrat (Fiber zibethicus) are familiar representatives. "The common brown rat (Mus decumanus) was introduced into this country from Europe about 1775, and has now nearly wholly sup- - planted the black rat (M. rattus), also a European species, introduced about 1544. The beaver (Castor canadensis) is the largest rodent. It seems to be doomed to extermin- ation. through the relentless hunting of it for its fur. The woodchuck or ground-hog (Arctomys monax) is another THE VERTEBRATES: MAMMALS 247 familiar rodent larger than most members of the order. The chipmunks (fig. 128) and ground-squirrels are com- monly known rodents found all over the country. They are the terrestrial members of the squirrel family, the best known Fic. 128. Chipmunk. (Permission of Camera Craft.) arboreal members of which are the red squirrel (Sciurus hudsonicus), the fox-squirrel (S. ludovicianus), and the gray or black squirrel (S. carolinensis). The little flying squirrel (Sciuropterus volans) is abundant in the Eastern States. The shrews and moles (Insectivora).—The shrews 248 THE ANIMALS AND MAN and moles are all small carnivorous animals, which, be- cause of their size, confine their attacks chiefly to insects. The shrews are small and mouse-like; certain kinds of them lead a semi-aquatic life. There are nearly a score of species in North America. Of the moles, of which there Fic. 129. The hoary bat, Lasiurus cinereus. (Photograph from life, by J. O. Snyder.) are but few species, the common mole (Scalops aquaticus) is well known, while the star-nosed mole (Condylura cristata) is recognizable by the peculiar rosette of about twenty carti- laginous rays at the tip of its snout. Moles live underground and have the fore feet wide and shovel-like for digging. The European hedgehogs are members of this order. The bats (Chiroptera).—The bats (fig. 129), order Chi- THE VERTEBRATES: MAMMALS 249 roptera, differ from all other mammals in having the fore limbs modified for flight by the elongation of the forearms and especially of four of the fingers, all of which are con- nected by a thin leathery membrane which includes also the hind feet and usually the tail. Bats are chiefly noc- turnal, hanging head downward by their hind claws in caves, hollow trees, or dark rooms through the day. They feed chiefly on insects, although some foreign kinds live on fruits. There are a dozen or more species of bats in North America, the most abundant kinds in the Eastern States being the little brown bat (Myotis subulatus), about three inches long with small fox-like face, high slender ears, and a uniform dull olive-brown color; and the red bat (Lasiurus borealis), nearly four inches long, covered with long, silky, reddish-brown fur, mostly white at tips of the hairs. The dolphins, porpoises, and whales (Cete).—The dolphins, porpoises, and whales (Cete) compose an order of more or less fish-like aquatic mammals, among which are the largest of living animals. In all the posterior limbs are wanting, and the fore limbs are developed as broad flattened paddles without distinct fingers or nails. The tail ends in a broad horizontal fin or paddle. The Cete are all predaceous, fish, pelagic crustaceans, and especially squids and cuttlefishes forming their principal food. Most of the species are gregarious, the individuals swimming together in “schools.” The dolphins and porpoises com- pose a family (Delphinidz) including the smaller and many of the most active and voracious of the Cete. The whales compose two families, the sperm-whales (Physeteride) with numerous teeth (in the lower jaw only) and the whalebone whales (Balenide) without teeth, their place being taken in the upper jaw by an array of parallel plates with fringed edges known as “whalebone.” The great sperm-whales or cachalots (Physeter macrocephalus) found in southern 250 THE ANIMALS AND MAN oceans reach a length (males) of eighty feet, of which the head forms nearly one-third. Of the whalebone whales, the sulphur-bottom (Balenoptera sulfurea) of the Pacific Ocean, reaching a length of nearly one hundred feet, is the largest, and hence the largest of all living animals. The common large whale of the Eastern coast and North Atlantic is the right whale (Balena glacialis); a near relative is the great bowhead (B. mysticetus) of the Arctic seas, the most valuable of all whales to man. Whales are hunted for their whalebone and the oil yielded by their fat or blubber. The story of whale-fishing is an extremely interesting one, the great size and strength of the ‘“‘game’’ making the “‘fish- ing” a hazardous business. The hoofed mammals (Ungulata).—The order Ungu- lata includes some of the most familiar mammal forms. Most of the domestic animals, as the horse, cow, hog, sheep, and goat, belong to this order, as well as the familiar deer, antelope, and buffalo of our own land and the elephant, rhinoceros, hippopotamus, giraffe, camel, zebra, etc., familiar in zoological gardens and menageries. The order is a large one, its members being characterized by the presence of from one to four hooves, which are the enlarged and thickened claws of the toes. The Ungulates are all herbiv- orous, and have their molar teeth fitted for grinding, the canines being absent or small. The order is divided into the Perissodactyla or odd-toed forms, like the horse, zebra, tapir, and rhinocerus, and the Artiodactyla or even-toed -forms, like the oxen, sheep, deer, camels, pigs, and hippo- potami. The Artiodactyls comprise two groups, the Ru- minants and Non-ruminants. All of the native Ungulata of our Northern States belong to the Ruminants, so called because of their habit of chewing a cud. A ruminant first presses its food into a ball, swallows it into a particular one of the divisions of its four-chambered stomach, and later regurgitates it into the mouth, thoroughly masticates THE VERTEBRATES: MAMMALS 251 it, and swallows it again, but into another stomach-chamber. From this it passes through the other two into the intestine. The deer family (Cervide) comprises the familiar Vir- ginia or red deer (Odocoileus americanus) of the Eastern Fic. 130. Male elk, or wapiti, Cervus canadensis. (Photograph of a specimen mounted by L. L. Dyche.) ; and Central States and the white-tailed, black-tailed, and mule deers of the West, the great-antlered elk or wapiti (Cervus canadensis) (fig. 130), the great moose (Alce ameri- cana), largest of the deer family, and the American reindeer or caribou (Rangifer caribou). All species of the Cervide have solid horns, more or less branched, which are shed 252 ; THE ANIMALS AND MAN annually. Only the males (except with the reindeer) have horns. The antelope (Antilocapra americana) (fig. 131) common on the Western plains also sheds its horns, which, Fic. 131. Antelope, male, female, and young, Antilocapra americana. (Photograph of however, are not solid and do not break off at the base as in the deer, but are composed of an inner bony core and an outer horny sheath, the outer sheath only being shed. The family Bovide includes the once abundant buffalo or specimens mounted by L. L. Dyche.) THE VERTEBRATES: MAMMALS 253 bison (Bison bison) (frontispiece), the big-horn or Rocky Mountain sheep (Ovis canadensis) (fig. 128), and the strange pure-white Rocky Mountain goat (Oreamnos montanus). The buffalo was once abundant on the Western plains, Fic. 132. A buffalo, Bison bison, killed for its skin and tongue on the plains of Western Kansas, forty years ago. (Photograph by J. Lee Knight.) travelling in enormous herds. But so relentlessly has this fine animal been hunted for its skin and flesh that it is now practically exterminated (fig. 132). A small herd is still to be found in Yellowstone Park, and a few individuals live in parks and zoological gardens. In all of the Bovide the horns are simple, hollow, and permanent, each enclosing a bony core. 254 THE ANIMALS AND MAN The carnivorous mammals (Fere).—The order Fere includes all those mammals usually called the carnivora, such as the lions, tigers, cats, wolves, dogs, bears, panthers, foxes, weasels, seals, etc. All of them feed chiefly on animal substance and are predatory, pursuing and killing their prey. They are mostly fur-covered and many are hunted for their skin. They have never less than four toes, which are provided with strong claws that are frequently more or less retractile. The canine teeth are usually large, curved, and pointed. While most of the Fere live on land, some are strictly aquatic. The true seals, fur-seals, sea-lions, and walruses comprise the aquatic forms, all being inhabitants of the ocean. The true seals, of which the common harbor seal (Phoca vitulina) is our most familiar representative, have the limbs so thoroughly modified for swimming that they are useless on land. The fur-seals, sea-lions, and walruses use the hind legs to scramble about on the rocks or beaches of the shore. The fur-seals (fig. 133) live gregariously in great rookeries on the Pribilof or Fur Seal Islands, and the Commander Islands in Bering Sea. The bears are represented in North America by nine species, of which the best known are the wide-spread brown, or black bear (Ursus americanus) and the huge grizzly bear (U. horribilis). The great polar bear (Thal- arctos maritimus) lives in arctic regions. The otters, skunks, badgers, wolverines, sables, minks, and weasels compose the family Mustelide, which includes most of the valuable fur-bearing animals. Some of the mem- bers of this family lead a semi-aquatic or even strictly aquatic life and have webbed feet. The wolves, foxes, and dogs belong to the family Canidae. The coyote (Canis latrans), the gray wolf (C. nubilus), and the red fox (Vulpes pennsylvanicus) are the most familiar representatives of this family, in addition to the dog (C. familiaris), which is Fic. 133. The Lukanin rookery of fur seals, Callorhinus atascanus, on St. Paul Island, Pribilof group, Bering Sea. (Photograph from life, by the Fur Seal Commission.) 256 THE ANIMALS AND MAN closely allied to the wolf. ‘Most carnivorous of the carnivora, formed to devour, with every offensive weapon specialized to its utmost, the Felide, whether large or small, are, relatively to their size, the fiercest, strongest, and most terrible of beasts.”” The Felide or cat family includes the lions, tigers, hyenas, leopards, jaguars, panthers, wildcats, and lynxes. In this country the most formidable of the Felidz is the American panther or puma (felis concolor). It reaches a length from nose to root of tail of over four feet. Its tail is long. The wildcat (Lynx rufus) is much smaller and has a short tail. The man-like mammals (Primates).—The primates, the highest order of mammals, include the lemurs, monkeys, baboons, apes, and men. Man (Homo sapiens) is the only native representative of this order in our country. All the races and kinds of men known, although really *showing much variety in appearance and body structure, are com- monly included in one species. The chief structural characteristics which distinguish man from the other members of this order are the great development of his brain and the non-opposability of his great toe. Despite the similarity in general structure between him and the anthropoid apes of the Old World, in particular the chimpanzee and orang- outang, the disparity in size of brain is enormous. The lowest Primates are the lemurs, found in Madagas- car, in which island they include about one-half of all the mammalian species found there. The brain is much less developed in the lemurs than in any of the other mon- keys. The monkeys and apes may be divided into two groups, the lower, platyrrhine monkeys, found in the New World, and the higher, catarrhine forms, limited to the Old World. The platyrrhine monkeys have wide noses in which the nostrils are separated by a broad septum and with the openings directed laterally. These monkeys are mostly smaller and weaker than the Old World forms and THE VERTEBRATES: MAMMALS 257 are always long-tailed, the tail being frequently prehen- sile. They include the howling, squirrel, spider, and ca- puchin monkeys common in the forests of tropical South America. The catarrhine monkeys have the nose-septum narrow and the openings of the nostrils directed forwards, Fic. 134. “Bob,” a monkey of the genus Cercopithecus. (Photograph from life by D. S. Jordan.) and the tail is wanting in numerous members of the group. They include the baboons, gorillas, orang-outangs, and chimpanzees. These apes have a dentition approaching that of man, and in all ways are the animals which most nearly resemble man in physical character, CHAPTER XIX DOMESTICATED ANIMALS The animals that we call domestic while sometimes of kinds and appearance very different from any wild animals that we know are yet certainly all descended from kinds that are or were originally wild. There are wild pigs, wild goats, wild doves, wild ducks, wild silkworms! There are no wild dogs nor probably any longer any true wild horses but it is easy for us to see from what wild animals our tame dogs and horses have been derived. It is certain from the records of history, of ancient pic- tures and carvings and still more ancient bones and relics, that man has had domesticated animals for the last ten thousand years. How long before that he made a practise of taming and using and perhaps breeding his animal com- panions of pre-historic times we may never know. In the caves where are found the bones and rude implements of early man, that primitive man of the Glacial epoch, there are also found the bones of various animals, but these seem to be the remains of kinds that were either his victims or his con- querors in the raw struggle for existence of those ancient times. However, when the pre-historic Egyptians emerged from the Stone Age into the earliest light of history they appear with cattle, sheep, donkeys and dogs already fully domesticated. The domestication of animals is the result of several. different factors. First, there may be the simple capture and taming and using of individuals of a wild species. Then comes the rearing in captivity of young of this species, 258 DOMESTICATED ANIMALS 259 and the easier taming of these home-reared individuals be- cause of their earlier acquaintanceship with man. : But in this rearing in captivity a new element enters almost at once. That is the choosing or ‘selection of certain of these young to be allowed to grow up, and again the choos- ing among these when grown up of those to be the parents Fic. 135. Assyrian hunters with great dogs. From an Assyrian wall relief of 668 B.C., now in the British Museum. (After Keller.) of more young. This selection may be almost unconsciously done, or it may be made intentionally and carefully, so as to preserve the most desirable individuals and have them give birth to others like themselves. Then there comes the crossing of special individuals or the hybridizing with other races in the hope of adding or com- bining in the offspring the desirable qualities of both kinds of parents. It is this careful selecting and crossing that are yy fou, Fic. 136. Various races of pigeons, all probably descended from the European rock dove, Columba livia, shown in lower right hand corner. (After Haeckel.) 260 DOMESTICATED ANIMALS 261 usually meant when animal breeding is spoken of. And our modern hosts of kinds or races of domesticated animals, the scores of sorts of dogs and cats and cows and pigeons and ducks have all been produced by “breeding.” The acts of choosing and hybridizing and choosing again and rearing from these chosen offspring and again from each following generation until a form is arrived at very different in appearance or habit from the original ancestor are called also artificial selection. It was largely on a basis of his observations of the methods and results of artificial selection that Charles Darwin founded his great theory of natural selection, which, is, simply, that Nature uncon- sciously chooses or selects among animal and plant indi- viduals and kinds through the survival and producing of young by those types born with traits advantageous in the struggle for existence, this struggle being inevitable on account of the geometrical ration by which animals multiply. The art of the animal breeder has. reached in these later days, the days since Darwin particularly, a very high stage of development. It is becoming a science, because the breeders are studying the laws of variation and heredity and making their hybridizations on a basis of the scientific knowledge of these laws. There is in our country a large association of animal and plant breeders known as the American Breeders’ Associa- tion, the reports of whose meetings with the discussions and prefaced papers presented at them are books of true science. Such men as Luther Burbank have given the science of breeding a popular fame and familiarity that was not known a half century ago. | An important thing to note in connection with animal breeding and artificial selection is that the selecting and modifying is all made to change the animals along lines wholly determined by man; lines that make the animals more useful or pleasing or curious to us but not better fitted 262 THE ANIMALS AND MAN to survive in Nature. In fact most of these artificially in- duced changes tend to unfit the animal for success in life unaided by man; they are mostly degenerative changes. The loss of flight, the shortening of legs, the over-develop- ment of fat, the production of crests and plumes and ruffs, the loss of horns, the sluggishness and helplessness that characterize the domesticated animals of different kinds, are all characters and conditions of degeneration. Fic. 137. Thibet wolf, Canis niger, one of the wild ancestors of dogs. (After Sclater.) As an outcome of this modern great interest and activity in the methods and results of producing new races and types of domesticated animals, the history of the origin of many of the more wide-spread and useful of these animal races has been unraveled, and the following paragraphs give in briefest possible form some interesting facts about the origin of our more familiar animal companions. There seems to be no doubt that the dog is the oldest domesticated animal as he is also the closest and the most universal. From among the crudest of living human races to the most civilized and cultivated, the dog is everywhere al- ways man’s companion, serving him as faithful helper in DOMESTICATED ANIMALS 263 the chase, in caring for his flocks and home, and as com- panion of his table and fireside. The Bushmen of Australia, the Esquimaux of the Arctic, the Indians of the prairie and pampas, the cannibals of the scattered Pacific Islands as well as the Caucasians of the world’s great capitals have their dog companions. And as is inevitable under such many and different conditions and civilization stages of hu- man existence the kinds of dogs are many and very different. How many dog races and types there now are I do not know; hundreds, at least. There are many long books filled with the descriptions and illustrations of these manifold varieties, from the tiny, toy dogs of Paris, that a lady can carry in her muff, to the great Danes and St. Bernards that stand three feet high and weigh one hundred and fifty pounds. The origin of all these dog races is not to be found in any one wild species of doglike animal but in several. These wild ancestors of the dogs are certain wolves and jackals of various lands. Dogs are descended from at least seven such wild species, namely the jackal (Canis aureus) of west- ern Asia, the landga (Canis pallipes) of India, the jackal wolf (Canis anthus) of northeast Africa, the walgie (Canis simensis) of Ethiopia, the black Thibet wolf (Canis niger) of Thibet, and the coyote (Canis latrans) and dun-gray wolf (Canis occidentalis) of North America. , The house cats, on the contrary, as various and as widely distributed as they are, seem to be all descended from a single wild species. This is the dun wild cat (Felis mani- culata) of northeast Africa. All of the present races of house cats trace their lineage back to Egypt. That the Egyptians were much given to the possession and care of cats the numerous cat mummies of their graves show. Cats were a sacred animal for them under the special pro- tection of the Goddess Bast, a goddess introduced into Egypt by Semitic influence. The horses of modern times can be traced back to two 264 THE ANIMALS AND MAN wild ancestors, namely Equus przewalskii of northern Asia, from which all the Oriental, Mongolian, Arabian, North African and East European races have sprung; and Equus caballus fossilis, or the diluvial horse, of Europe, from which the German, Norman, English and West European horses generally have arisen. In America fossil horses have Fic. 138. Arion, a record-holding American trotting horse. (After Plumb.) been found back through a series of geologic ages as far as the beginning of the Tertiary age forming a connected series from the small Eohippus of the Lower Eocene period, about the size of a fox, and with four toes and splint of the first digit on the front feet and three toes and splint of the fifth di- git on each hind foot; through Protorohippus and Oro- hippus of the Middle Eocene, about 14 inches high, with four toes on front feet and three toes on hind feet, and no splints; through Mesohippus of the Oligocene, about the DOMESTICATED ANIMALS 265 size of a coyote, and with three toes on all its feet; through Protohippus and certain other kinds of the Middle Miocene, about as large as Shetland ponies and with three toes on all feet but with the side toes not touching the ground; to Equus, which first appeared in the Pleistocene with only one developed toe and splints of the 2d and 4th on each foot. tic. 139. Restoration of the tour-toed horse; based on a mounted skeleton, 16 inches high, in the American Museum of Natural History. (After a water-color by C. R. Knight.) The color of the prehistoric horse is not known but it was probably dun with more or less well-defined stripes like a zebra. The bones of human beings have been found associ- ated with those of prehistoric horses in South America and in Europe. Remains of horses are associated in Europe with human relics of the Bronze Age. Donkeys have been derived from two wild species, the Nubian Desert donkey, Equus teniopus, and the onager, Equus onager of eastern Asia. Tame donkeys are figured in the earliest of Egyptian and Assyrian drawings and carvings. 266 THE ANIMALS AND MAN The races of domesticated hogs are also descended from two wild races, the European wild boar, Sus scrofa, and another species, Sus vittatus, from eastern Asia. From this latter the swine of China and those of the Romans and indeed most of the European races have descended. The lake dwellers of Switzerland had domesticated hogs, and pig Fic. 140. Wild boar contrasted with the modern domestic pig. (After Romanes.) remains have been found with prehistoric relics in Denmark. China has had domesticated swine for thousands of years. The many races of cattle all trace back to two sources, the wild Banteng, Bos sondaicus, of Java and South Asia, from which are derived the zebus, the old Egyptian long- horns, and many of the races of Europe, such as the Span- ish, Albanian, Sardinian, Polish and brown Alpine cattle; and the primitive wild ox of Europe, Bos primigenius, from which have descended most of the English, North German, DOMESTICATED ANIMALS 267 and Holland races. This wild species persisted in Germany until the 12th century and in Poland up to the 18th century. A few persons in America have tried to create a hybrid race by crossing domestic cattle with the buffalo but probably no permanent result has been reached. It is a pity that our American bison could not have left us more of a heritage than a shameful memory. Fic. 141. The Banteng, Bos sondaicus, or wild ox of Java and South Asia. (After Keller.) The domesticated races of sheep seem to have had three original wild sources, the Ovis musimon of South Europe, the Ovis arkal of Western Asia and the Ovis tragelaphus of North Africa. Most of our present European and American races come from the second named of these wild kinds. The earliest certain remains of tame sheep appear in the Stone Age. In the Bronze Age sheep domestication was well developed. The oldest of Assyrian drawings picture domesticated sheep, among which the still persisting fat- tailed race appears. The Egyptians had domesticated sheep in pre-Pharaonian times. Our goats also are descended from three wild races, namely Capra aegagrus of Western Asia, Capra falconeri Fic. 142, Heads of various British breeds of domestic cattle, showing variations in shape of head and condition of horns: 1 Highland Scot; 2, Irish Kerry; 3, Aberdeen Angus; 4, Hereford; 5, is 6, sid horned Midland. (After Ror----* — - DOMESTICATED ANIMALS 269 and Capra jemlaica of the Himalayas. The earliest pre- historic indications of tame goats come from the times of the Lake-dwellers. In the Bronze Age they were common. Other mammals that are represented by domestic races are the camel, the elephant, the water buffalo, the rabbit, the ferret, the reindeer, the lama and alpaca, the guinea-pig, the mouse, the rat, etc. But excepting with the rabbit the Fic. 143. White Hall Sultan, a Shorthorn prize bull. (After Plumb.) domesticated forms of these animals are only wild species tamed and reared under man’s hand but not much modi- fied by breeding. There are several well-marked races of domesticated rabbits all of which probably trace their lineage back to a wild species native to Spain and South- ern France. Of birds there are domesticated races of doves, chickens, turkeys, ducks, geese, swans, pea-fowls, pheasants, canary birds, ostriches, cormorants and others. Of these the doves and chickens are represented by the most varieties. Brown, an English authority on domesticated birds, lists more than 270 THE ANIMALS AND MAN seventy races of chickens now living, thirteen races of ducks, ten of geese and eight of turkeys. Of pigeons there must be nearly as many domestic races as there are of chickens. And yet all of them, with all their extraordinary variety of crests, and ruffs, and tails and plumage pattern, and all their various’ special manners such as tumbling, dancing, Fic. 144. Typical American Merino ewe, a highly specialized Seed of sheep, with fine, close-set wool. (After Shaw.) . and the like, are descended from a single wild species, the common rock dove, Columba livia, of Europe, Asia and North Africa (fig. 136). The domestic races of chickens are by some naturalists also held to be descended from a single wild species, the jungle fowl, Gallus bankivus, which ranges from Hindukoosh to the Chinese island of Hainau and through most of the Indonesian islands. But other naturalists believe that one or two other wild species of fowl are concerned in the an- cestry of our barnyard hen. DOMESTICATED ANIMALS 271 The domestic ducks are derived from the wild duck Anas boschas, and have evidently originated from this ancestor. independently both in China and in Europe. * The domestic geese seem to have an older origin than the ducks; in fact geese are probably the oldest of domesticated birds. The ancestor of our races is the wild species Anas cinereus. ‘The Chinese races how- ever, are descended from Anas cygmoi- des, and the early Egyptians seem to have tamed and used the Nile goose, Chenalopex egy ptiaca. The domesticated peacocks are de- scended from the wild species of In- dia, Pavo cristatus. The turkeys trace their ancestry to the wild Meleagris gallopavo of North Fis. 145. The wild sheep of the Trans-Caspian steppes, Ovis arkal. (After Keller.) America. The swans are really only tamed wild kinds. Common spe- cies are the white swan of Europe, Cygnus olor, the black swan of New Holland, Cygnus atratus, and the black- necked swan of South America, Cygnus nigricollis. The pheasants also are so far practically only partially tamed wild species, whose eggs however, are usually hatched under turkeys. Most of the kinds kept are from the Orient. Canary birds are descended from the wild species, Frin- gilla canariensis of the Canary Islands. But there has been some crossing of them with other species of wild birds, 272 THE ANIMALS AND MAN especially certain sparrow and finch kinds. There are now numerous domesticated races which vary structurally in color-pattern a8 well as in voice. Many of the characters resemble the ruffs, crests, and other plumage eccentricities of pigeons. The principal place of canary bird breeding at present is in the Harz Mountains of Germany. Tamed cormorants are used by the Chinese and Japanese as fishing birds, somewhat as falcons were used in days of weer Fic. 146. Wild jungle fowls, Gallus bankiva, of India. ‘After Brown.) old as hunting birds. Indeed in these same days cormorants were used for sport. Charles I of England had a ‘‘master of the cormorants.” Nowadays, however, cormorant fishing is a practical means of gaining food. A ring is placed about the neck of each bird so as to prevent it from swallowing the fish it.catches. Several different species of cormorants are thus used. The ostrich is the most recent addition to the ranks of domesticated birds. The tamed species is derived directly from the widely distributed African ostrich, Struthio camelus. Besides mammals and birds two or three species of fish, such as the carp and goldfish, may be called domesticated. DOMESTICATED ANIMALS 273 This is certainly true of the goldfish which is a product of Chinese ani- mal breeding. Some most bizarre forms have been produced in the thousand or more years in which this fish has been a subject of selection and hybridization. There are also finally at least two species of insects that have a right to be called domesticated animals, namely, the honeybee and the mul- : berry silkworm. The Fic. 147. Silver-laced Wyandotte cockerel. a fH honeybee, Apis mel- Me lifica, has been long used by man to obtain honey from, but only in modern times has the species been the subject of true ‘“‘breed- ing.” However, already several distinct races have been produced. The bee is native to Europe and Asia, and “wild” honeybees in America are only com- munities established by wandering swarms ee oe from hives, or from Fic. 148. White-crested black Polisn cock.’ other “wild” communi- 274 THE ANIMALS AND MAN ties which have descended from such escaped swarms. The silkworm, Bombyx mori, has on the contrary been an artificially bred animal for five thousand years, and , scores of races, \ with differently RBs: ’ colored and shaped Fic. 149. Tiger-banded variety of the Bagdad COCOONS exist. The silkworm race. (Natural size.) actual wild species from which the domesticated races are descended is not known, but it is most likely some one of the several wild species of Northern India. The cocoons of certain of these wild Indian species are today still collected for the silk and sold under the commercial name of ‘“Tussoor” silk. The ancient breeding and care of silkworms was mostly done in China and Japan. Today it is carried on even more extensively in France and Italy. CHAPTER XX FOSSIL ANIMALS Not all the animal kinds that have lived on this earth still live on it. Indeed those that now exist, as many hun- dred thousands.or millions as they may be, are certainly only a small part of all that have existed. The earth has had a history of life as varied and nearly as old as the history of its own liquid and solid self. As soon as it had cooled and contracted from a great gaseous mass to a smaller com- pacter liquid and solid one it began to be a possible abode of life. And sometime after its temperature had got below the co- agulation or killing point for protoplasm—which is the basic substance of every living thing—life appeared. Whence it came or how it came to be produced are great questions that sclence has yet no answer for and may never have. The speculations about it are various: such as that living germs reached the earth from other planets in meteorites or as “cosmic dust,” or that it originated spontaneously under the peculiar chemical and physical conditions of the earth’s surface in those ancient dim days of the first hardening and. cooling. And there are even some biologists who think that such spontaneous generation of life from non-living sub- stances may be going on today. But no one of them has been able to prove this. ‘All life from previous life” is the dictum of most naturalists of today. And this poses the problem of the origin of the first life as one ae beyond present scientific knowledge. If, however science knows nothing about ihe « origin of life in the early days of the earth’s history it does know something 275 (‘A10ISIPT [BANJEN JO winasnyy UBIUeUTY 9y) UT Buyjured woay {Biequiasisyy) ‘wWsuy pue uioqgsQ Aq uoyeIOWsaY “prez sspunyy, 10 ‘snanvsojuoag “OST “O1A Z < = a Z < Z = Z <— fr B FOSSIL ANIMALS 277 about what kinds of living creatures, both plants and ani- mals lived in those and succeeding ages. It knows this by virtue of the preservation of parts of some of these animals and plants as fossils. Animal fossils are the actual remains of bones or shells or other (usually hard) parts of the body preserved intact in soil or rock; or else, and more commonly, are parts of ani- mals which have been turned into stone by slow replacement of these parts by rock particles; or else, finally, are parts of which stony casts have been made. Examples of these three kinds of fossil are (1) extinct insects preserved in amber, teeth of ancient sharks, tusks of mammoths, shells of various molluscs; (2) petrified bones, corals, crinoids shells, etc.; (3) casts of insect wings, etc. Huxley said that “fossils are only animals and plants which have been dead rather longer than those which died yester- day.” This “rather longer” may mean anywhere from a few thousand to several million years. Geologists estimate the age of the habitable earth—the time, that is, since life could have existed on the surface—as being from fifteen mil- lion to seventy million years. This enormous time is divided into certain periods of various lengths each period being characterized by a certain set of geologic, geographic and life conditions,.and these conditions determining in some measure the kinds of plants and animals living during the period. The geologic history of the earth, which is a very broken and partial one, is read by the geologists from the kind and succession of rocks and fossils which form the outer crust. Only in certain rocks, those that have been slowly deposited in water as small (usually soil) particles and have become compacted and hardened into layers or strata, one above the other, do fossils occur. Hence only water-inhabiting animal kinds, or those land kinds whose dead bodies might get into lakes or oceans, are represented by fossil remains. Also, sedimentary or stratified rocks ( B19quIe}S Jaye ‘A10}SIFT [BiIN}JeNY JO uNasnyY UBoTIEWTY 9Y} ul) ‘4ojadskp snanvsojt ‘imesojA], pesou-wey jo uoywayS “IST “OT : (‘Siequisig pue uojstA\ J0qze ‘sesuey jo AysioatuQ ay} Jo wmasnyy ay up) ‘zu40gGs0 280 THE ANIMALS AND MAN form only a part of the earth’s crust. Rocks that are cooled and solidified from a molten condition, such as volcanic and other igneous kinds, and even stratified rocks that have been highly heated, contain no fossils. Hence the record or history of the life of the long geologic ages before our present one is most incomplete. But it is one of extraor- dinary interest and value in any study of biology. Only a very few words can be said about the interesting kinds of earlier creatures, now extinct, that inhabited our earth in ancient times. In the very oldest fossil bearing rocks are found only remains of the simpler kinds of animals as the one-celled kinds, and the sponges, corals, jelly-fishes, etc. In the next oldest strata there are still only simple invertebrate animals but more kinds than in the older rocks. The first vertebrates appear next and these are all fishes. Amphibians are found only in more recent strata, reptiles in still more recent and mammals and birds in still younger strata. That is, it is plain from the record of the rocks that the animal types have appeared in succession beginning with the simpler kinds and advancing towards the most complex or higher types by regular stages. ‘This fact is one of the most important that has been learned about life, for it is very strong evidence for the belief of most naturalists that animal kinds are descended from each other, the complex or higher ones from simpler or lower ones. The table or diagram on the next page shows the order of the appearance of various kinds of animals in geologic time. One must not believe that with the advent of new types of animal life all of the old types became extinct. It is not at all true. Although hundreds of thousands of animal species have become extinct and are known to us only through their fossil remains, or are not known at all, some FOSSIL ANIMALS 281 Eras or Animals Especially Charac- Periods. Ages or Systems. teristic of the Era or Age. Quaternary or Pleis-| Man; mammals, mostly of spe- Cenozoic. | tocene (age of manand cies still living. Era of recent mammals)..| Mammals abundant; belonging Mammals. | Tertiary: Pliocene, to numerous extinct families Miocene, Eocene... and orders. Cretaceous .......-- Birdlike reptiles; flying reptiles; toothed birds; first snakes; bony fishes abound; sharks M F again numerous. hea ok Jurassic.......----.- First birds; giant reptiles; am- Reptiles monites; clams and_ snails . abundant. Trlassic: 2.2 dats se First mammals (a marsupial); sharks reduced to few forms; bony fishes appear. Earliest of true reptiles. Amphi- Carboniferous (age of bians; lung fishes; fringe fins; amphibians) ....-. first crayfishes; insects abun- dant; spiders; fresh-water mussels. First amphibians (froglike ani- Devonian (age of mals); sharks; ostracophores; Paleozoic. | fishes) ......-.---- first land shells (snails); mol- Era of luscs abundant; first crabs. Inverte- First truly terrestrial or air- brates. Silurian (age of in- breathing animals; first in- vertebrates) ....... sects; corals abundant; mailed fishes. First known fishes, ostracophores, Ordovician or Lower mailed and with cartilaginous Silurian .......... skeleton; brachiopods; trilo- bites, molluscs, etc. Cambrian ......... Invertebrates only. Archean. Algonidan. Tne Simple marine invertebrates. 282 THE ANIMALS AND MAN species of all the great groups from simplest to higher are living today. Most of these species are however modern in their origin. The original or first species in all the great Fic. 153. Skeleton of Hesperornis regalis, the Giant Toothed Bird of the Kansas Cretaceous. (In the American Museum of Natural History; after Sternberg.) groups are gone; and some whole families and orders of species are extinct. For example in the class of reptiles there existed in the Mesozoic era many enormous kinds FOSSIL ANIMALS 283 called Dinosaurs, Ichthyosaurs, Pterodactyls, etc., of which no living representatives are left. Some of these reptiles had. wings (Pterodactyls) and seem more like great birds than true reptiles. In the bird class, too, there were, in the same era, various enormous kinds now extinct, some of which had, teeth. An interesting example of the geologic succession of related animals and one often referred to in books about extinct animals, is that of the horse series. In lower Eocene rocks is found an animal called Eohippus, about the size of a fox, with four hoofed toes and the rudiment of a fifth on forefeet and three hoofed toes on hind feet. This is the first of a series of similar but always differing and ever- more horse-like forms that are found in the rock strata suc- cessively younger and higher, representing Miocene, Pliocene and Quaternary periods. The hoofed toes disappear one by one, the size of the whole animal is ever larger, and the teeth are more and more like horse’s teeth as we examine the successively younger (more recent) members of the series, until in the rocks of our present epoch we find the bones of an animal which is essentially identical with the horse as we know it today. Similar ancestral series have been discovered for the deer, for certain pond snails, for the ammonites, for many other kinds of animals, indeed. The first deer in the early Miocene had no antlers. In the middle Miocene are found small deer with small two-pronged antlers. In the upper Miocene and lower Pliocene there are larger deer with three-pronged, larger antlers. In the later Pliocene occur four and five-pronged antlers, while in the Pleistocene are remains of deer with branching antlers like those of the liv- ing species. The fossil fishes of the earlier geologic periods are all of the simpler, more primitive families of which none or but few representatives occur today. Of the 12,000 known (‘Ar0jsty [RANE NY JO uNasnyA, UROLIOUTY 343 UL Suyured worz {Biaquisig Jay) “jyswy pue wiogsg fq uonwioysoy ds sdojpsazia [ ‘anesoulq pe0}-e1yL, “PST “ld FOSSIL ANIMALS 285 living species of fishes 11,500 belong to the great group of Teleostomi or bony fishes, of which the first representatives are found only in Triassic strata. But fossil fishes are known from all the geologic periods from the Silurian on up. All the fishes of these earlier millions of years were of more primitive shark-like families. Many of these families are now wholly extinct and of the others only a few per- sisting species remain. Even those early families of the true bony fishes of the Triassic and Jurassic rocks are mostly now extinct. Most modern families date from Cretaceous times. The question may be asked: Are there any fossil men known? The answer is yes. But man is very young, geologically speaking. No indubitable human bones or relics have been found in rocks earlier than those of the present great epoch, the Quaternary. But this epoch is certainly already many thousand years old. Man existed in Glacial times. Remains of the mammoth, the cave-lion, cave-bear, and other extinct animals have been found in the same caves with human bones. So man has a certain geologic history; one at least of 20,000 years; probably much longer. PART IV HUMAN STRUCTURE AND PHYSIOLOGY (Chapters XXI to XXVIII, inclusive, by ISABEL McCRrACcKEN) CHAPTER XXI INTRODUCTION The study of physiology and its purpose.—We have found in our study of animals that they are made up of many parts or structures arranged in definite ways. To see many of the parts itewas necessary to dissect the animals that we have studied most carefully, as the frog and craw- fish. This study of the structure of animals is called the study of anatomy. We must know something of the anat- omy of the animal body to understand what it can do. We have learned that each part has its special function and that these various functions constitute the processes which, added together, ,are life itself. The study of the functions of the various structures of the body is called the study of physiology. Since the study of physiology is the study of the parts of the living body in action, the study of human physiology at first hand is very difficult. We can dissect the lower animals easily, and find out at first hand what their parts are and how they are put together, but elementary students cannot dissect the human body. They must depend upon 287 288 THE ANIMALS AND MAN the statements of physicians, surgeons, and trained physi- ologists for most of their knowledge of human anatomy and human physiology. The health of the human body depends upon the right performance of its proper function by each part of the body. The laws of health or of hygiene are merely those rules that have been proved by experience and experimentation to be best adapted for maintaining the body in its best work- ing condition. Our chief purpose in studying human physiology is there- fore to understand the working of the human body as a self-regulated, working machine, that we may know how to give it the protection and care necessary to preserve it as such. Structural units of the living body and division of labor.—In a lifeless mechanism like a watch, we find many individual parts, and these parts so nicely adjusted one to the other that they all work together successfully as a whole. So it is in the living mechanism. Our study of the amoeba (Chapter V) made us acquainted with a living, feeding and moving animal whose body is composed of a single cell. Our study of the structure of the toad (Chapter III) showed us that the life-functions are performed in this animal by certain large systems of organs; that these organs are made up of groups of tissues formed of masses of similar cells, each cell performing its own special kind of work. The cell is therefore the struc- tural and physiological unit of the body. Each cell does its share of the work of that tissue of which it is a part, and each tissue does its share of the work of the organ of which it is a part. In the same way each organ works in harmony with all the other parts in its system, and all the systems work together to maintain life. The living substance of the cell and metabolism.—In Chapter V it was explained that while the cells of the body may differ very much in appearance and function, they are HUMAN PHYSIOLOGY: INTRODUCTION 289 alike in being chiefly made up of the one substance proto- plasm. This is the living substance of the cell. The life and activity of the body depend upon the life and activities of the protoplasm of the many cells of the body that make up the various organs. A diseased condition of body means a diseased condition of the protoplasmic cells of the body. Metabolism.—In their functional activity, the cells of the body provide heat and do some kind of work. This work is done by reason of the energy generated by the cell. In providing energy the cell itself wears out or wastes away. It has, however, the power of self-renewal or self-repair. This double process of ‘‘waste and repair” is known as metabolism. The airy we breathe, the water we drink and the food we eat supply the cells of the body with the three essentials for their metabolism. Protoplasm is a very complex substance built of simpler substances. The foods we eat are first reduced to simple substances. Each protoplasmic cell acts as a little chemical laboratory in laying hold of these simple food substances, and recombining their elements into its own complex sub- stance. It then reverses the process and, with the aid of oxygen, breaks up this complex substance into simple sub- stances. These are then thrown out of the cell as waste products. The whole problem of the body, as a mechanism, is, there- fore, to obtain air, water, and food and to carry these to the cells; then to carry the waste away from the deep-seated cells, and eliminate it from the body. It is to this end that all the systems of the body work together. Systems of the human body and their functions.—In the human body, as in the higher animals already studied, there is a digestive system, consisting of the alimentary canal and all of its parts. This system supplies the body with 290 THE ANIMALS AND MAN food and prepares the food for the use of the tissues. A circulatory system, consisting of heart, blood-vessels, capil- laries, and lymphatics, transports the prepared food and oxygen to the cells of the body. The muscular and skeletal systems, consisting of the muscles and bones of the body and their attachments, enable the body to do all the things re- quiring motion. The respiratory system, consisting of the air passages of the nose, throat or pharynx, larynx, the bronchial tubes and minute air sacs forming the large respira- tory surface, is employed in supplying the blood with oxygen which is to be carried to the cells. An excretory system, con- sisting of the kidneys and their ducts, and certain glands in the skin known as sweat glands, take up the waste from the blood and remove it from the body. The nervous system, consisting of the brain, spinal column and innumerable nerves, puts all the parts of the body into communication so that they may work in harmony. The sense-organ sys- tem, intimately connected with the nervous system and functioning with it, comprises the organs for seeing, hearing, smelling, tasting, feeling, etc. They put the inside of the body into communication with the outside world. All of these systems work together to maintain life, that is, to maintain the metabolism of the cells. If any system fails to fulfill its function the whole body suffers and disease sets in. It is our business to provide the body with good food, fresh air, pure water and daily exercise so that each system may be kept in the best condition possible for its work. The chemistry of the body.—The chemist tells us that, in all the world, there are only about seventy simple or ele- mentary substances. All the gases, liquids and solids that we know of, are formed by uniting these simple elements in many ways. ‘Thus the simple element oxygen united with the simple element hydrogen forms the water we drink. A mixture of pure oxygen, nitrogen, hydrogen and a few other gases forms the air we breathe. HUMAN PHYSIOLOGY: INTRODUCTION 2g1 The cells of the body are made up of certain chemical substances, compounds of the simple elements, sulphur, phosphorus, carbon, oxygen, hydrogen and nitrogen and a few other substances (potassium, chlorine, calcium and magnesium). Comparatively few elements, therefore, are found in the animal tissues. These are, however, united in many ways to form many different compounds. Chemical compounds of the body.—The chemical compounds found in the body are proteids, carbo-hydrates, fats, acids, and salts. Proteids contain carbon, oxygen, hydrogen, and nitrogen. These are called the nitrogenous compounds. Carbo-hydrates contain carbon, hydrogen and oxygen, the former predominating. Fats contain also chiefly oxygen, carbon and hydrogen, the latter predominating. The carbo-hydrates and fats are known as non-nitrogenous substances. Since these are the chief substances that the body is built up of, they must also be the chief substances in the foods we eat. OBSERVATION OF A FEW SIMPLE CHEMICAL ELEMENTS Oxygen, the properties of.—The most necessary ele- ment in all the world is oxygen. Neither plant nor animal can live without it. Fire cannot burn without it. It forms about one-fifth of the atmosphere. It is a colorless, odor- less and tasteless gas. Most of the other simple elements will combine with it, especially at a high temperature. Oxidation and combustion.—Oxidation is the union of oxygen with any other substance. We say that a substance is oxidized if it has taken up oxygen. Thus carbon, when it takes up oxygen, is oxidized and becomes carbon-dioxide. When oxidation is rapid or accompanied by light or great 292 THE ANIMALS AND MAN heat it is called combustion. When a match is rubbed on a surface, the heat produced by friction causes the phos- phorus.and other substances at the match tip to take up oxygen rapidly, causing combustion. Phosphorus is thus “oxidized and the combustion that arises from its rapid oxidation sets the match on fire and consumes it. Rust is oxidized iron or iron-oxide. It is the nature of organic substances (compounds con- taining carbon) to unite easily with oxygen. That is, oxygen has a great affinity for these compounds. It combines easily with other elements. To obtain oxygen.—The simplest way to obtain pure oxygen is to heat some compound containing it. The heat breaks up the compound and sets its elements free. The oxygen thus escaping may be collected. EXPERIMENT 1.—Place some oxide of mercury in a test tube and heat it. It gradually disappears from view. The oxygen and the mercury of the compound have separated. The oxygen has become an invisible gas, the mercury has become vaporized. Drops of pure mercury will soon condense on the sides of the glass. If, while the experiment is in progress, a live coal on the end of a stick, be inserted into the mouth of the test tube the coal will glow with a greater brilliancy. This means that oxygen in its pure state unites more freely with the carbon of the wood and makes a more brilliant glow than did the oxygen of the air, mixed as it was with other gases. Potassium chlorate gives up oxygen rapidly when heat is applied to it, so rapidly indeed as to cause an explosion. If an equal quantity of black oxide of manganese be mixed with potassium chlorate, the oxygen is given off more slowly and without danger of explosion, and may then be collected in jars as follows: Arrange an apparatus as in fig. 155. First fill the jar with water and invert it over the pan of water. Partly fill the test tube with the mixture of potassium chlorate and black oxide of manganese (equal parts). Fit the test tube with a tightly fitting cork and a bent glass delivery rod. Before placing the delivery tube in the water move the alcohol flame along the test tube so as to drive out the air and warm the tube, that no moisture may form on the tube and break the glass. Then heat the mfxture gradually, beginning at the top and working HUMAN PHYSIOLOGY: INTRODUCTION 293 toward the bottom. After a few seconds gas will come off. The de- livery tube may then be placed under water beneath the opening of _, the jar, and soon the bubbles of oxygen coming off will displace the water in the jar. Caution.—After collecting a jar of oxygen (or several jars) lift the end of the delivery tube out of the water before removing the lamp, otherwise the water will rush back into the delivery tube and crack it. Insert the live coal of a splinter into the jar. It will burst into flame. Fic. 155. Apparatus for collecting oxygen. (After Jenkins and Kellogg.) Or heat the end of a piece of picture wire and insert the red-hot wire into the oxygen. It will burn with a bright flame, thus showing again that oxygen “‘supports combustion.” Other experiments with oxygen may be found in books on elementary chemistry. Properties of Carbon.—Carbon is the chief solid element in wood, muscle, fat, sugar, starch, etc., in fact in every substance that is or has been living. For this reason, sub- stances containing carbon are called organic substances. It is found in coal, showing that coal was once a living sub- stance. A special branch of chemistry, called ‘Organic Chemistry,” is devoted to the study of the carbon compounds. The black substance, or charcoal, left after the splinter was burned is almost pure carbon. It is without taste or odor. When carbon is cold it has little affinity for other elements. When it is heated, however, it takes up oxygen, or becomes oxidized, as we have seen in our oxygen experi- 294 THE ANIMALS AND MAN ment. The gas formed by oxidized carbon is carbon dioxide. It is colorless but may be readily detected on account of its power to turn lime water milky. Carbon dioxide is constantly formed in our bodies and given off in the breath. If we breathe through a straw or glass tube into a jar of lime water, the water in the jar will soon take on a milky appearance due to the union of the carbon and lime. In the formation of carbon dioxide, as in other oxidations (or formation of other oxides), heat is gen- erated. This principle is made use of in the cells of the body for the generation of heat and energy. Oxidation in the body.—The oxygen of the air is taken into the lungs and passed into the blood. The blood carries it to the cells. The carbon of the living cell derived from the food takes up oxygen, that is, becomes oxidized. Heat is produced, and the energy, by means of which the work of the body is done, is liberated. Phosphorus.—Phosphorus in its pure state is a yellowish waxy substance. With calcium and oxygen it forms a large part of our bones. The affinity of pure phosphorus for oxygen is so great that it must be kept under water or else combustion will take place. Sulphur.—Pure yellow sulphur is familiar to all of us. When sulphur is oxidized it gives off suffocating fumes. Muscle is largely a compound of sulphur and other elements. The disagreeable odor given off by decaying flesh is caused chiefly, by the sulphur fumes. In eating an egg with a silver spoon the sulphur of the egg forms with the silver a blackish compound. FOODS AND NUTRITION Food nutrients.—Those substances needed by the cells for their metabolism and their growth are called food nu- trients. The nutrient or food value of any substance there- HUMAN PHYSIOLOGY: INTRODUCTION 295 fore depends upon its composition or the amounts and kinds of nutrients present. It must contain one or more of the following substances, proteids, carbohydrates, fats, water and inorganic salts. The following table shows approximately the average com- position of some of those substances commonly used as food. Composition of Foods.* Carbohydrate (In 100 =| Water é Divestible Inorganic parts) |H,O sa Starch Cellulose Salts and Sugar Meat ...... 76.7 | 20.8 | 1.2 3 1.3 Eggs......- 973-7 | 12.6 |12.1 I.I Cheese ...-. 36-60 | 25-33 |7-30 3-7 3-4 Cow’s milk .| 87.5 3-4 | 3-2) 4-8 -7 Wheat flour.) 13.3 | 10.2 -9, 74.8 a6 Wheat. bread] 35.6 4.1 #2 55-5 “3 1.1 Rye flour...) 13.7 | 411-5 | 2.1 69-7 =3 1.4 Rye bread ..| 42.3 6.1 -4 49-2 1.6 1.5 Rice veai ees I3-I | -7-0 9 77.4 “5 1.0 Corn....... 13-1 9-9 | 4.6 68.4 -6 I.5 Macaroni. ..| 10.1 9-0 3 79-0 2.5 25 Peas, beans, lentils ....|12-15 | 23-26 |13-2] 49-54 £3 2-3 Potatoes .-.-| 75-5 2. 32 20.6 4-7 I Carrots..... 87.1 I. 2 9-3 7 -9 Cabbages --} 90. 2-3 “5 4-6 I.4 1.3 Mushrooms .|73-91 4-8 5 3-12 I-2 I.2 Fruity, avec: 84 5 10. I-5 i Butter....-- 15 83- 4- *Howell’s Physiology, p. 676 (with slight additions). Uses of nutrients (proteids, carbohydrates, fats, salts, and water).—The exact use of each kind of nutrient to the body is a subject upon which there has been much careful experimentation. Two things are positively known, and they have already been stated. First, the nutrients furnish the cells with materials for growth and metabolism, and 296 THE ANIMALS AND MAN second, their oxidation in the cells results in the production of energy, in the form of heat or motion; that is, they furnish the body with building material and fuel. The proteid compounds are best fitted for this purpose, though each food nutrient has its value. We may now consider each of the food nutrients sepa- rately, and the place ‘of each in our diet. Proteids or nitrogenous compounds (albumins, etc.).— While the exact composition of proteid is unknown the substances forming it are known to be carbon, oxygen, hydrogen, nitrogen, sulphur and other elements. Such foods as white of egg, lean meat, milk curd and the gluten of wheat, contain large amounts of proteid. The proteid food stuffs are the only food stuffs supplying nitrogen to the body. This nitrogen is being constantly eliminated from the cells and hence must be constantly restored #o the cells. Proteids have been called flesh-producers or tissue-formers because they possess all the elements for forming tissues and cells, as muscles, nerves, etc. Plants manufacture proteid from sugars and certain min- eral salts, the former supplying the carbon, hydrogen, and oxygen, the latter supplying nitrogen, sulphur, and other elements. Plants are therefore the original source of supply for proteid food. While carnivorous animals obtain their proteid by eating the flesh of other animals, these have obtained it from plants. Tests For Proteid. a. Xanthoproteic Test.—Boil the substance to be tested in strong nitric acid (80%); a lemon yellow appears. Wash in water and add enough ammonia to neutralize the acid. If the color changes to deep orange proteid is present. b. Millon’s Test.—Pour Millon’s reagent (solution of mercury in nitric acid) over the substance to be tested and bring slowly to a boiling point. If proteid is present the solution becomes rose red. Proteid burns with the odor of burning leather. Carbohydrates (starches, sugars, etc.).—Carbohydrates con- HUMAN PHYSIOLOGY: INTRODUCTION 297 tain carbon, oxygen and hydrogen. The green parts of plants are, with the aid of sunlight, the manufacturers of starch. The materials used are carbon dioxide (CO,) obtained from the air by the leaves, and water obtained by the roots. Thus vegetables and fruits supply the carbohydrate foods. Starch forms the chief carbohydrate food of the world. Carbohydrates unaided could not, however, form living cells because they lack the element nitrogen, therefore, they could not take the place of proteids. The carbohydrates, with the fats, have been called the heat and energy producers because their compounds, in becoming split up and oxidized, produce energy for the per- formance of the body movements, and heat to maintain the temperature of the body. The carbohydrates and fats have also been called “‘proteid sparers”’ because by keeping up the supply of heat and energy of the body they spare the proteids from that kind of work so that their main work may be that of tissue formation and growth. It would take relatively a very large amount of proteid to furnish sufficient heat and energy. Therefore, if we should furnish the body with enough proteid for this we should over-furnish it with tissue-building material. It is thus economy to furnish carbohydrate foods for heat and energy and proteid for tissue-building. Test For Starch.—Break up and crush the substance to be tested (a bit of potato or corn). Pour over it a few drops of iodine solution. If there is a large amount of starch present it will turn black, if but little starch is present it will turn blue. Test For Grape or Cane Sugar.—Heat the substance to be tested, slightly, in a test tube with a little water. Add to this twice its bulk of Fehling’s solution* (may be obtained at the drugstore). Heat *To prepare Fehling’s solution: Solution 1.—Add to 35 grains of copper sulphate (blue vitriol) 500 cubic centimeters of water and put aside until dissolved. _ Solution 2.—Add to 160 grains of caustic soda and 173 grains of Rochelle salts, 500 cubic centimeters of water. Mix equal parts of solutions 1 and 2, 298 THE ANIMALS AND MAN the mixture or allow it to remain over night ina warm room. If grape sugar is present in any quantity, the contents of the tube will turn first greenish, then yellow and finally brick red. Fats (butter, oils, oil of nuts, etc.).—Like carbohydrates, fats contain carbon, oxygen, and hydrogen ‘but in different proportions. They are insoluble in and lighter than water. They are easily oxidized as we know from the rapidity with which they burn. Like carbohydrates, they are heat and energy producers and proteid savers. Tests for Fats——Rub the substance to be tested upon a sheet of white paper, or heat it in an oven upon paper. If oil is present, it will show as a grease spot. Water.— Water undergoes no chemical change in the body. Its importance as a food is due to the fact that it forms a large percentage of the composition of the body, nearly 59% of the total weight. A large amount of water is thrown off daily as waste, through the skin and kidneys. This must be restored daily to keep the body well. Our food provides only about one-third of the water we need and we must drink three or four pints each day to supply the deficiency. - Water promotes digestion, by aiding in softening and dissolving the food and stimulating contractions of the muscle. A large amount of muscle and a much larger amount of blood is water. Inorganic salts (chlorides, sulphates, carbonates, etc.).— Inorganic salts are found in the cells and fluids of the body, and particularly in the bones, of which they form an im- portant part. They are non-oxidizable and hence have no importance as sources of energy. They are supposed to function in controlling the flow of water to and from the tissues. This is by virtue of the principle of osmotic pres- sure. These salts are supplied to the body largely through vegetable food. Diffusion and Osmosis.—When one liquid is poured into another the resulting solution will be a blend of the two HUMAN PHYSIOLOGY: INTRODUCTION 299 substances, if they are capable of mixing. That is, the molecules of one liquid become thoroughly intermingled with the molecules of the other, as when syrup is poured into water. This is diffusion. If two such liquids are separated by an animal membrane, the molecules of each will pass through the membranes so that in time the solutions on each side will be equally diffused. ‘This passage of the molecules of liquid through an animal membrane is known as osmosis.. The “attrac- tion” exerted mutually by the liquids is called osmotic pres- sure. Osmotic pressure varies with the density and tem- perature of the solutions. Osmosis and osmotic pressure are facts of great importance in animal physiology as we shall see when we study the nutrition of the cells. Procure from the butcher a small bladder; moisten it and fill it with sugar solution. Insert a tube into the opening and tie the neck of the bladder tightly around the tube. Immerse this in a dish of water and note the result. The energy with which the water enters the solution of greater density is due to osmotic pressure. Relative value of common foods.—-Our meals consist usually of a ‘‘mixed diet,” of fruit, nuts, cereal and eggs, or perhaps bread, meat, and vegetables. Experience has shown that a mixed diet is better suited to the appetite and to the needs of the body than a single food material. Eggs, milk and bread are nutritious because they contain almost no waste. Meat is valuable for its high percentage of proteid. Potatoes and other vegetables are valuable for their high percentage of carbohydrates. Some foods are valuable for their large percentage of water. Daily diet—Certain experiments have been made both in Europe and America to determine a “standard diet’”—the amount of food that should be consumed in order to preserve the health. This amount varies of course with the occupation,- the sex and the age of the individual and with the climate. 300 THE ANIMALS AND MAN Prof. Atwater of the U. S. Department of Agriculture gives the following table as approximating the average amounts of nutrients needed per day. Conditions Proteid Carbo- Fat *Calories Ibs. hydrate Ibs. Man with light muscular work......- -22 -88 .22 2980. Man with moderate work..........-. -28 2.99 .28 3570. Man with active muscular work...... 233 I-10 .33 4060. Principles involved in cooking food.—Cooking improves the taste of food, by bringing out its natural flavors. It renders food more wholesome by killing any noxious or poi- sonous organisms that may have collected on it in the mar- kets. It makes the food more digestible by softening the fibers, and in vegetables by bursting the cell walls so that the digestive juices can get at it. Economy in the purchase of foods.—The Department of Agriculture at Washington is giving much attention to this subject and bulletins of the results of investigations are published from time to time to furnish information about it. “The cheapest food is that which supplies the most nutrient for the least money. ‘The most economical food is that which is cheapest and at the same time best adapted to the wants of the eater.” If we adopt these as rules for the purchase of foods we must study tables of the relative values of foods and consult the markets for relative prices. Food accessories.—We commonly add certain things to our foods to make them more palatable, to make them taste better, such as pepper, mustard, vanilla, cinnamon, nutmeg, vinegar, pickles, lemon juice, etc. These are condiments, or flavors, and contain none or but little of the food nutrients. *A calory is the accepted unit for measuring heat. It is the amount of heat necessary to raise the temperature of one kilogram of water one degree. tFarmers’ Bulletin, 23, p. 20. HUMAN PHYSIOLOGY: INTRODUCTION 301 They are therefore known as food accessories. They are not absolutely necessary as part of the diet, but, used in limita- tion, they stimulate the appetite and favor the flow of diges- tive juices. They, therefore, have a place upon the table. If used in excess, however, they destroy the normal appetite for natural flavors and may over-stimulate the glands that furnish the digestive juices. Stimulants.—There are certain other substances that primarily excite or stimulate the activity of certain parts of the body, chiefly the nervous system, without providing material for growth or repair, for heat or energy. These are stimulants. They are chiefly tea, coffee, cocoa, chocolate and alcoholic liquors. While in small amounts these may be harmless, it is not easy to tell how small this amount should be, and it differs with different dispositions. Their chief injury to the body lies in the fact that, by stimulating the nervous system, they deprive the body of the sense of fatigue, or of the desire for sleep, and so also of the benefits derived from rest and sleep. Alcohol.—A true food is a substance which nourishes the body, acts as a tissue builder or as a heat and energy producer. It has been determined by experiment, that in very small amounts given at stated and widely separated periods, alcohol is oxidized in the body, and thus produces heat and energy as do the fat and carbohydrate foods. These are such doses as the physician sometimes gives when for some reason he must find an equivalent for fats and carbohydrates. In large amounts, alcohol has been found to act as a drug, causing much harm to the tissues, poisoning them and disarranging them seriously. Like other stimulants, and acting more quickly and in- juriously, it excites the nervous system in a peculiar manner. Unlike other poisons, its use establishes a craving or appetite for it which eventually weakens the will and is apt to lead to intoxication. 302 THE ANIMALS AND MAN In small amounts, then, alcohol may be considered as a kind of food but should be administered, like other medicines, under a physician’s order. In large amounts it is recognized as a poison and dangerous. The direct action of alcohol upon certain organs will be considered later. Narcotics.—Narcotics are substances which blunt the sensibilities and induce sleep. Tobacco, alcohol (in large quantities), opium, morphine and cocaine, are the most common. All narcotics are deadly poison when taken in large quantities. Some of them, like tobacco and alcohol may stimulate in small doses and narcotize in large doses. Tobacco, like alcohol, affects the nervous system. It leads to weakness of the heart and irregular pulse by inter- fering with nerve regulation. The poisonous ingredient of tobacco is nicotine. It is this that makes boys sick and sleepy when they first begin to use tobacco. The constant use of tobacco impairs the digestion through its action on the salivary secretions. It produces hoarseness and catarrh through irritation of the mucous lining of the mouth. CHAPTER XXII DIGESTION AND ABSORPTION Digestion.—We have learned that it is the function of food to nourish the cells of the body. The cells can, how- ever, absorb liquid food only, so the food requires further treatment than mere cooking to render it of use to the cells. It is the function of the alimentary canal and its assisting or digestive glands to dissolve thoroughly the food, to separate the nutritious from the non-nutritious, and to treat it with such reagents that it can be taken up by the cells. This is digestion. The alimentary canal—Digestion, as has been said, takes place in the alimentary canal. Our study of the ali- mentary canal of the frog, together with the use of the accom- panying diagram (fig. 156), will aid us in understanding this structure in the human body. It is a continuous tube from the mouth to the anus. Part of the tube is twisted and doubled back upon itself, as shown in the figure. Its entire length, were it stretched out, is about thirty feet. Its diameter varies at different points, being widest at the stomach. There are outgrowths at different points called glands that furnish the digestive juices for dissolving and preparing the food. These glands pour their secretions into the various parts of the alimentary canal where they become thoroughly mixed with the food. ‘The alimentary canal is lined with a soft mucous membrane like that within the mouth. Its secreting cells furnish mucous for keeping the inner surface moist. The mouth or buccal cavity.—If we close the lips and feel around with the tongue we find the mouth bounded on 303 304 THE ANIMALS AND MAN the front and sides by the /ips, the teeth, the gums and cheeks. The tongue (fig. 157) lies on the floor of the mouth. The Salivary __.) Glands Gullet MVver----~ Mh Hl) : Lh ; Cy Mi Mi Ry iP nal es © a A a pancress Ouedenum «* lerge dntestina ------) Vermiform Appendix =< [t Fic. 156. Diagram of the alimentary canal. (Modified from Landois.) hard palate and soft palate form the roof of the mouth. The pendant hanging from the soft palate is the wvula. During deglutition or swallowing the wvula closes the inner passage DIGESTION AND ABSORPTION 305 into the nasal cavity which lies above the palate (see fig. 157). The teeth and tongue act mechanically upon the food, masticating it or breaking it up. The teeth—The teeth are important structures since they initiate the work of digestion. Those that grow in during the first two years of life are called milk teeth. They have small- er roots than the per- manent teeth and ap- pear while the jaws are small. As the jaws enlarge (during the sixth and seventh years) the second set or perma- f igs \ nent teeth grow in and te f a7, | She gae one by one replace the ig pate. milk teeth. The perma- \ nent teeth need much < 2 Trachew care and attention as S they must last through- 8 out life. Fic. 157. Diagram of the buccal cavity Kinds of teeth Pua showing the manner of closing the ‘There are eight teeth in posterior nares during deglutition. the front of the mouth (After Landois & Stirling.) (four on each jaw) called incisors, to bite and cut the food. The sharp pointed teeth on either side of the incisors are the canines. On either side of the canines there are two large teeth with two-point- ed surfaces. These are the bicuspids or premolars. On either side of the premolars are three large molars. The premolars and molars are grinders. The third molars fre- quently do not appear until after the twentieth year, and are commonly called the wisdom teeth. Structure of the teeth (fig. 158).—The teeth, though as 306 THE ANIMALS AND MAN hard as bone, are not bone but a hardened epithelium tissue. The part above the gum is the crown and is but a part of the whole tooth. Under the gum are the neck and roots. The roots are inserted into sockets in the jaws. cisors and canines have but one root, the premolars have usually two roots and the mo- lars have from two to five. If a tooth is cut lengthwise as shown in the figure, there is exposed a central chamber, or pulp chamber filled with Y blood-vessels and nerves which have entered the cavity oi through the roots. The pulp chamber is surrounded by a layer of dentine (D), an ivory- like substance which makes up the bulk of the tooth. The dentine is protected on the crown by enamel (E), the hardest substance in the body, and on the roots by cement (C). The enamel protects the teeth from mechanical injury and from the effect of chemicals and bacteria. Care of the teeth.—As the teeth masticate or grind the food and prepare it for the Fic. 158. tooth in jaw. dentine; P. M., peridontal mem- brane; P. C., pulp cavity; C, cement; B, bone of lower jaw; V, vein; A, artery; N. nerve. (After Stirling.) The in- Vertical section of a E, enamel; D, action of the digestive juices, their condition has much to do with the health. Decay of teeth is caused by injury to the enamel. This is due mainly (1) to the action of bacteria or particles of food that lodge between the teeth; (2) to tartar, a deposit DIGESTION AND ABSORPTION 307 of lime salts that collects on the teeth especially near the gums. The teeth should be brushed with water after every meal to remove every particle of food from the mouth. Once or twice a week a good tooth powder like precipitate of chalk should be used. This is not hard enough to injure the enamel but removes the tarter. A dentist should examine the teeth about once a year. Salivary glands.—The salivary glands open into the mouth. There are three pairs. These are named from their location: parotid, lying in front of and below the ears; submaxillary, lying beneath the lower jaw, and sublingual, lying beneath the mucous membrane in the floor of the mouth. The position and openings of these glands are shown in fig. 156. Chemical action of saliva.—The salivary glands secrete a digestive juice called saliva. This is composed mainly of water and a certain enzyme called ptyalin. An enzyme is an organic substance which acts chemically upon another substance so as to change its nature without itself becoming changed. Ptyalin changes starch, an insoluble food, to sugar, a soluble food, that is, it digests starch. The chewing process in the mouth thoroughly mixes the saliva with the food so that the enzyme can reach the starch. This is the first act of digestion. The mechanical action of moistening the food and thus preparing it for swallowing is quite as important as its chemical action. Food thus moistened stimulates the sensation of taste. Experiment to Show Digestion of Starch.—Chew a piece of par- affin; this will start the flow of saliva in the mouth. Collect the saliva in a test tube. Test its chemical reaction with litmus paper. If it changes blue litmus to red it is alkaline. If it changes red litmus to blue it is acid. Add a little vinegar to the saliva and test again. Account for the different result. Partly fill a test tube with saliva, another with water, a third with saliva to which vinegar 308 THE ANIMALS AND MAN has been added. Test a bit of soda cracker for its starch reaction (see p. 297). Place the soda cracker (a little boiled starch will do as well) in each of the three test tubes and leave over night in a warm room. In the morning test the contents of each tube for starch and for sugar. In which has digestion taken place? Deglutition.—Deglutition is the act of swallowing. Fig. 157 shows how it is begun. The tongue is raised to the roof of the mouth, and the uvula automatically closes the nasal passage. The food is pushed into the pharynx by means of the muscles at the base of the tongue. The pharynx.—There are seven openings into the pharynx; one each to the mouth, the windpipe or larynx, and the oesophagus, a pair to the nasal passages, and a pair to the Eustachian tubes leading to the middle ear. The opening into the larynx (or sous) is closed by the epiglottis during deglutition. The pharyngeal cavity is lined with mucous membrane. The oesophagus.—The pharynx narrows intotheelongated oesophagus. ‘This is also lined with mucous membrane and has muscular walls which by peristaltic contraction pass the food into the stomach. FPeristaltic contraction is a contrac- tion that starts at one end of a series of muscles and moves along the muscles in a wave. It may be imitated by press- ing the fingers on a rubber tube and drawing them the length of the tube. The abdominal cavity.—This is the large cavity shown in fig. 159 separated from the thorax or chest by the muscular diaphragm (D). At the back are the spinal column and lower ribs. Its base is formed by the large pelvic bones (P). The sides and front are covered with muscles. The cavity is lined with peritoneum, a membrane which is deflected over the organs lying in this region, and which supports them. This membrane secretes a fluid (serous fluid) which keeps it moist. Form and structure of the stomach (figs. 156 and 159).— i DIGESTION AND ABSORPTION 309 The stomach is a pear-shaped organ lying just beneath the diaphragm. ‘The oesophagus opens into its larger or cardiac Fic. 159. Diagram of thorax and abdomen showing location of heart, viscera and lings. C, clavicle; D, diaphragm; 10, first dorsal vertebra; F, femur; H, humerus; Ht, heart; I, ilium; L, liver; L. L., large intestine; L. L., left lung; P. pelvis; R. L,, right lung; S. I, small intestine; S, scapula; | St., sternum. (After Deaver.) end which is at the left side. The walls are muscular, and distend as food enters. It is covered on the outside with 310 THE ANIMALS AND MAN the peritoneal membrane and lined by a mucous membrane. A submucous membrane lies between the muscular coats and the mucous coat or epithelium. The large blood vessels of the stomach lie in the peritoneum and send capil- laries into the submucous coat. The mucous coat is smooth when the walls of the stomach are distended, but wrinkled when the stomach is empty and its walls collapsed. The stomach narrows at its lower or pyloric end and opens into thesmall intestine (fig. 156). . Glands.—The mucous lining is covered with minute shallow pits, the openings of the gastric glands. The glands fur- nish certain enzymes, pepsin and rennin, all of which aid in digestion. The pyloric glands (fig. 160), which furnish pepsin only, lie in the pyloric end of the stomach. The fundus glands in the cardiac part of the stomach, are formed of sev- Fic. 160. Section of pyloric eral kinds of cells, and furnish glands from human stomach. S : : a, mouth of gland leading into pepsin, rennin and hydrochloric —’ jong wide duct (b), into acid. which open the terminal divi- The gastric juice containing sions; c, connective tissue of P ‘ mucosa. (After Piersoe.) these enzymes acts in an acid medium upon proteid food, while the ptyalin of the salivary juice acts in an alkaline medium and upon carbo- hydrates. The presence of food or food accessories in the stomach stimulates the flow of gastric juice. , Pepsin.—This enzyme changes proteid into a soluble form called peptone. It acts at a rather high temperature. Rennin.—This enzyme acts upon milk, causing it to coagu- late or separate into curds (the proteid part) and whey (mostly DIGESTION AND ABSORPTION 311 water). This separation prepares it for the action of pepsin. Hydrochloric acid.—This secretion establishes the acid medium necessary for the action of pepsin and may dissolve some of the mineral salts. The cardiac or fundic end of the stomach (fig. 156) acts as a reservoir for the food as it leaves the oesophagus. Here the food may remain for sometime while the starchy matter is further acted upon by the salivary juice. In the pre-pyloric and pyloric end digestion of proteid is begun by the gastric juice. This is the second stage in digestion. It results in a milky mass called chyme, which in part is ready for absorp- tion and in part needs further treatment. This passes in small amounts Fic. 161. Mucous membrane of the ~ : 3 small intestine of the dog. A, artery; into the small intestine. B, vein; C, capillaries; D, lacteals; The small intestine and E, glands of Lieberkithn; Ep., epi- the intestinal juices.—The thelial tissue. (After Cadiat.) s , 3 : intestine is a very long coiled tube held in place by a fold of the peritoneum called the mesentery. The mesentery is fastened at the back to the spinal column. The coats of the small intestine are similar to those of the stomach. The inner surface of the small intestine is covered with minute papille or projections called villi (fg. 161). These are filled with blood vessels and lymphatic vessels. Between the villi are numerous minute pores. These are openings of tiny glands that secrete intestinal juices. Other digestive secretions found in the small intestine are the bile and the pancreatic juice, 312 THE ANIMALS AND MAN The liver—This is the largest gland in the body. It lies (fig. 159 Li) beneath the diaphragm, its lobes partly over- lapping the stomach. Its cells, called hepatic cells, secrete bile. Its duct opens into the small intestine near the pyloric end. Unused bile is stored in a small sac or gall bladder con- nected by a duct with the bile duct near its distal end. The pancreas (fig. 156).—This gland lies along the curvature of the stomach. Its cells secrete pancreatic juice. Its duct joins the bile duct near its opening into the intestine, so that bile and pancreatic juice intermingle while entering the intestines. Digestion in the small intestine-—This is due to the combined action of the three digestive fluids mentioned, intestinal juice, pancreatic juice and bile. The intestinal juice furnishes an enzyme that acts upon starches and sugars and upon fats. The pancreatic juice furnishes three enzymes, trypsin, amylopsin, and steapsin. Trypsin, like ptyalin, acts in an alkaline medium. Like pepsin it acts upon proteid converting it into peptone. Amylopsin (diastase), like ptyalin, acts upon starch, con- verting it into sugar. Steapsin (lipase) acts upon fat. Fat is chemically composed of fatty acid and glycerine. This combination must be broken up before fat can be made di- gestible. When once broken up, the fatty acids unite with the alkali present and form a soap which is soluble. This process is saponification. Fat must also be broken up into tiny droplets. This is emulsification. These two processes are accomplished by intestinal juice and steapsin. Bile is alkaline and hence serves to neutralize the acid chyme and prepare it for the action of the intestinal and pancreatic juices. It also aids in emulsifying and saponi- fying fats. Digestion may be artificially demonstrated as follows. Procure from a druggist some dry pancreatic extract. Dissolve 15 grs. of this in 2 0z. of warm water. (1) Half fill a test tube with this artificial digest- DIGESTION AND ABSORPTION 313 ive juice and place in it a small amount of cooked starch. (2) In a second tube, place a small amount of white of egg or other proteid with the artificial digestive juice. (3) Ina third, place a few drops of olive oil and artificial digestive juice. Leave these preparations in a water bath or oven at 98° F. for 12 hours and note results. When the food is thoroughly dissolved it has reached the last stage of digestion. It is now ready for absorption. Absorption.—We have learned that the blood carries food to the deep seated cells of the body. The transfer of the digested food through the walls of the intestine to the blood is called absorption. The sole object of absorption is to get the digested food into the blood. This takes it through the walls of the villi. Fig. 161 represents a series of villi cut through to show the loose network of blood capillaries and lymphatic capillaries (lacteals) within each one. Lymphatic vessels are like blood vessels in some ways but they carry a milky fluid and not red blood. The mucous membrane of the intestine is bathed by the digested food. To reach the blood and lacteals, this digested food must pass through the mucous membrane of the villi and the thin walls of the capillaries and lacteals. This is accomplished by osmosis (see page 298). Only soluble substances can mix by osmosis, hence it is that starch, proteids and other foods must be dissolved or digested before they are ready for absorption. Where absorption takes place—A minute quantity of peptone (derived from proteids) may be absorbed in the stomach, and a small amount may pass into the large in- testine and become absorbed there, but most of it passes . through the walls of the villi of the small intestine into the blood. The sugar (derived from carbohydrates) is absorbed into the blood through the villi also. The fats (as emulsions or soaps) pass into the lacteals. 314 THE ANIMALS AND MAN Water and salts pass into the blood mainly in the small and large intestine. Alcohol is absorbed very quickly through the walls of the stomach. Its quick action upon the body is probably due to this fact. Action of the liver upon nutrients.—Absorbed food is carried immediately by a large blood vessel (the portal vein) to the liver. Here it undergoes further changes before it is distributed to the cells of the body. Here glycogen or liver starch is formed of any normal excess of sugar in the blood and held as a reserve supply. Here, also, any poisonous com- pounds, that may have been absorbed with the food and that might injure the tissues, are removed. The large intestine.—During its passage through the small intestine most of the digested food is absorbed, as we have learned. The undigested parts of the food, together with such poisons as have been collected by the liver, pass into the large intestine and out of the body through the rectum, by peristalsis. Constipation is the clogging of the rectum or large intestine. Constipation is dangerous because the poisons from the liver become reabsorbed. ‘This results in biliousness, headache and often very serious troubles. Hygiene of eating and digestion.—The body requires that some proteid, carbohydrate and fat and water shall be absorbed each day. The digestive system is regulated to care for a certain amount only. If too much is demanded of the alimentary canal, digestion is impaired and dyspepsia results. Digestion is a ‘“‘chain of results;” first the cooking, then the masticating, and finally solution in the digestive juices. All this takes care and time. A poorly cooked meal or a hurried meal means a partially digested meal. Lack of the right kind of food and of exercise engender con- stipation. Indigestion and constipation are the signs by which we know that something is going wrong and must be remedied. DIGESTION AND ABSORPTION 315 Effect of alcohol upon digestion.—While the use of alcohol may have a serious effect upon the activities of the body as a whole, through its influence on the nervous system, according to Chittenden and others it has little direct effect upon digestion. Their experiments have shown that it leaves the alimentary canal and enters the blood very soon after it reaches the stomach. In quantity it deprives the system of its normal healthy appetite. CHAPTER XXIII THE BLOOD AND CIRCULATION BLOOD We have seen that digestion prepares the food for the cells and that by means of absorption this food enters the blood. The blood is the common carrier between the ab- sorptive surface of the small intestine and all the tissues of the body. It circulates within a closed system of tubes or blood-vessels, and substances that pass into or out of the blood must pass through the walls of the blood-vessels. Composition of the blood.—If the finger is pricked with a clean needle and a drop of blood placed on a slide and looked at under the microscope, the blood will be seen as yellowish liquid, containing a great many tiny round disks and a few particles of irregular shape. The yellowish liquid is the plasma, the disks and other floating cells are corpuscles (red and white). Structure and function of the red corpuscles.—The red corpuscles are biconcave disks without nuclei and con- tain a red pigment, hemoglobin. It is the function of haemoglobin to carry oxygen to the tissues and carbon dioxide from the tissues. Structure and function of white blood corpuscles.— The white blood corpuscles are of many sizes and without definite form. They are colorless and nucleated. Many of them move about in the blood plasma like amcebe. Some of the white blood corpuscles (phagocytes) take up from the blood foreign organisms such as disease produc- 316 THE BLOOD AND CIRCULATION 317 ing bacteria. The formation of immunizing substances in the blood is attributed to leucocytes. Other corpuscles aid in the absorption of fats while others aid in forming a clot when a blood-vessel is wounded. Blood plasma.—-The plasma is the fluid part of the blood. It supports the red and white corpuscles. It is composed of much water, a substance called fibrin, certain salts, absorbed nutrients in the form of serum albumin, and certain wastes (urea and acids) from the tissue cells. Blood clotting.—Blood exposed to the air forms a clot by the mixture of some of the white blood corpuscles and fi- brin of the plasma. If a bowl of blood is stirred vigorously the fibrin may be separated from the serum and blood cor- puscles. Blood clot or coagulation protects against the loss of blood when a blood-vessel is wounded. The amount of blood in the body and its distri- bution.—A grown person is provided with about six quarts of blood which equals about one-thirteenth the weight of the body. This amount is constant under normal conditions, because the amount of food and oxygen given up to the tissues is balanced by the amount of waste received. The supply of blood to the heart and lungs, the liver and the skeletal muscles equals about seventy-five per centum of the whole amount in the body.- It is distributed to the tissues accord- ing to their needs. An active gland or an active muscle requires more than a resting gland or muscle. During di- gestion and absorption a large supply goes to the stomach. Effect of food, fresh air, exercise and rest upon the blood.—The healthy condition of the blood depends upon abundance of fresh air to supply it with oxygen; nutritious food and plenty of water to maintain the proper composition of the blood plasma and to supply iron for the red corpuscles; a sufficient amount of exercise so that all the arteries and capillaries may be thrown into activity; and sleep and rest that the demands of the tissues may not be too great a drain 318 THE ANIMALS AND MAN upon it. A short rest gives the blood time to carry away the wastes from the tissues. CIRCULATION In order that the blood may find its way from the absorp- tive cells of the intestine to every tissue of the body and from these to the lungs, it must circulate in a continuous flow. This it does by means of a closed system of vessels, the blood-vessels, and a pumping organ, the heart. The arteries carry blood away from the heart to the system and the lungs. The veins carry blood to the heart from the sys- tem and the lungs. Tiny anastomosing (many branched) vessels called capillaries connect the arteries and veins. Structure and position of the heart.—In fig. 159 the heart may be seen lying in its natural position, a little to the left of the thoracic cavity, just above the diaphragm and. be- tween the two lobes of the lungs. The apex points down- ward and to the left. The heart is enclosed within a sac called the pericar- dium. The walls of the heart are thick and muscular and are supplied with blood-vessels and nerves. Internal structure of the heart.—The heart is divided by a muscular partition into right and left halves, having no‘ intercommunication. Each half is separated into an upper and lower cavity, the auricle and ventricle. The right auricle opens into the right ventricle and the left aur- icle opens into the left ventricle. The blood flows from the auricles into the ventricles and out into the arteries. Fig. 162 shows the left side of the heart opened so that the inside may be seen. The opening between the left auricle and the left ventricle is guarded by a valve, the mitral valve, with two flaps (6,6). These flaps are fastened by strong cords to tiny muscular pillars on the walls of the ventriculus (5,5 ). The cords prevent the flaps from being forced backward into the auricle when the heart beats. THE BLOOD AND CIRCULATION 319 The opening between right auricle and right ventricle is guarded by the tricuspid valve. This is similar in structure to the mitral except that there are three flaps instead of two. The position of these valves in action is shown in figs. 163 and 164. Blood-vessels direct- ly connected with the heart.—The large veins open into the auricles. On the right side of the heart opening into the right auricle there are three veins, the superior Fic. 162. Left auricle and ventricle opened and a part of anterior and left wall removed. 1, two right pulmonary veins cut short; 1’,within cavity of left auricle; 2, wall between auricle and ven- tricle; 3, 3’, 3”, cut walls of ventricle; 4, portion of wall of ventricle with muscular pillar to which tendons of mitral valve are attached; 5, 5, muscular pillars on inner wall of left ventricle; 5’, within cavity of left ventricle; 6, 6’ mitral valve; 7, commencement of aorta (with semilunar valve below); 7’, aorta; 8, root of pulmonary artery and its semilunar valve; 8’, continuation of the pul- monary artery; 9, artery connecting pulmonary artery and aorta; 10, arteries arising from summit of aortic arch. (After Allen Thomson.) vena cava (descending from the parts of the body above the heart) the inferior vena cava (ascending from the parts 320 THE ANIMALS AND MAN of the body below the heart), and the coronary vein arising in the walls of the heart. On the left side of the heart opening into the left auricle there are four large veins, the pulmonary veins. Two of these arise in the left lung and two in the right lung. Two of these are shown at (1) in fig. 162. The large arteries arise in the ventricles. The aorta (7) arises in the left ventricle and carries the blood that is to be distributed to Fic. 163. Right cavities of the heart; auriculo-ventricular valves open, arterial valves closed. (After Dalton.) the tissues of the body. Its branches go to the tissues carrying blood laden with food and oxygen. The pulmonary artery (8) arises in the right ventricle and carries the blood that is to be distributed to the air chambers of the lungs. Its branches go to the walls of the lungs filled with blood laden with carbon dioxide which is there ex- changed for oxygen. The openings from the ventricles into the arteries are guarded by semilunar valves shown in fig. 162. Their position in action is shown in figs. 163 THE BLOOD AND CIRCULATION 321 and 164. Thus we see that the flow of blood from auricle to ventricle, and from ventricle to artery, can take place in one direction only. In case of diseased valves there may be a backward flow or regurgitation. How the heart works.—The auricles are constantly fill- ing with blood from the great veins. Both auricles contract at the same time, the auriculo-ventricular valves open and the blood is driven into the ventricles. The ventricles con- Fic. 164. Right cavities of the heart; auriculo-ventricular valves closed, arterial valves open. (After Dalton.) tract at once and send the blood out into the great arteries. The heart beat is the alternate contraction (systole): and relaxation or expansion (diastole) of the walls of the heart. In man this occurs about seventy-five times per minute under normal conditions. A child’s pulse is more rapid. Systemic circulation—-We have seen that the aorta carries food and oxygen to-the tissues. It passes anteriorly from the left ventricle, then arches and passes posteriorly 322 THE ANIMALS AND MAN and dorsally, forming thus the arch of the aorta (fig. 162,7’). The dorsal aorta passes downward through the diaphragm. near the spinal cord (fig. 167) to the lower part of the abdom- inal cavity. Here it divides into two great arteries, one to each of the lower limbs, the common iliac arteries. Branches of the aorta.—Two small arteries, the coronary arteries, leave the aorta near its point of origin. These sup- ply blood to the walls of the heart. From the arch of the aorta (fig. 162) three large arteries pass to the head, neck and shoulders. From the thoracic aorta, a number of small arteries pass to the muscles of the thorax, the pericardium and the oesophagus. Abdominal aorta and its branches.—A series of arteries arise from the aorta in the abdomen. 1. Two phrenic arteries passing to the muscles of the diaphragm. 2. Celiac axis—a short trunk that soon divides into three important branches supplying the stomach, liver, gall bladder, pancreas, and first part of the duodenum, and the spleen. 3. The superior mesenteric artery with its many branches supplying the small intestine (except the duodenum). 4. The renal arteries, passing to the kidneys. 5. The inferior mesenteric artery, supplying the large intestine and rectum. All of these arteries break up into capillaries in the tissues they supply. Thus the aorta, through its branches, supplies blood to every part of the body. The capillaries—At the extremities of the arteries the blood-vessels branch into finer and finer branches until they end in vessels of minute size. These are the capillaries. They penetrate the tissues of the glands, muscles, skin, brain, etc. Capillaries with the blood corpuscles trickling through them may be seen in a frog’s foot under the microscope. The tissue cells are surrounded by a watery fluid THE BLOOD AND CIRCULATION 323 called lymph. The capillaries are also bathed by lymph. Composition and uses of lymph.—Lymph is composed partly of water and partly of food material derived from the capillaries through their walls. Lymph gives up food and water to the tissue cells and receives from them, through their walls, certain. waste ‘products. Oxygen also passes from the capillaries through the lymph to the cells, and carbon dioxide passes from the cells through the lymph to the blood. We see, therefore, that the important changes in the blood take place in the capillaries and that the lymph sur- rounding the cells functions as a medium of interchange between the blood and the cells. This interchange is ac- complished by the process of osmosis (see p. 298). The veins.—As the arteries break up into capillaries, so ‘the capillaries unite, after leaving the tissues, to form veins. The blood that flows to the tissues through the arteries is laden with food and oxygen. We have seen that much of this is exchanged in the capillaries for carbon dioxide and waste products. Hence it is that the blood in the veins is | laden with these substances and needs to be purified before it again becomes fit for use by the tissue cells. The blood is partly purified in the kidney, partly in the liver, and partly in the lungs. The blood from the intestines, stomach, spleen and pancreas, passes by way of the portal vein to the liver. In the intestines it has gathered the di- gested food, as already described on page 313. The portal vein breaks up into capillaries in the liver and some of the particularly deleterious waste products and poisonous sub- stances that may have passed into the blood with the digested food, are here removed. From the liver the hepatic vein car- ries the blood into the vena cava ascending and thus back to the right auricle of the heart. Veins from other parts of the body, as the arms, legs, and muscles, return the blood from the capillaries of these parts, directly to the vena cava de- scending and so to the right auricle (fig. 165). 324 THE ANIMALS AND MAN This completes the systemic circulation. Pulmonary circulation.—We have learned that the sys- temic arteries carry blood away from the left ventricle, and that the veins return it to the right auricle. In this circula- tion the blood gathers food by absorption from the intestines, gives up food and oxygen to all the tissues and gets rid of certain waste products in the kidneys and liver, but it must also get rid of the large amount of carbon dioxide collected from the tissue cells. It does this through the pulmonary circulation. The blood received into the right auricle from the system (through the vena cavas) is forced into the right ventricle through the tricuspid valve. It is then pumped out into the pulmonary artery which carries it to the lungs, as already stated. The pulmonary arteries break up into capillaries in the tissues of the air sacs of the lungs (fig. 176). Carbon dioxide in the blood is here exchanged for oxygen. The blood thus purified is collected by four large pulmonary veins (fig. 175, 13, I4, 15, 16) and sent back to the left auricle of the heart. Figure 165 shows the course of this blood-flow as just described. We see, therefore, that all the blood leaves the heart by way of arteries and returns to the heart by way of capillaries and veins. We see that it all passes through one set of cap- illaries and that the blood from some of the organs (stomach, intestines, spleen and pancreas) passes through a second set of capillaries in the liver before returning to the heart. How is the circulation of blood maintained ?—The circulation of blood is effected as follows: The muscular ventricles pump the blood into the arteries. The valves be- tween the ventricles and arteries prevent the reflux of blood. The fine capillaries, because of their immense number and small size, exert a certain resistance so that all the blood thus pumped out of the heart can not at once pass through them. The walls of the arteries are elastic and hence expand to ac- THE BLOOD AND CIRCULATION 325 commodate whatever blood fails to pass through the capillaries during the heart beat. The elasticity of the walls of the arteries exerts sufficient con- stant pressure to force the blood through the capillaries between heart beats. In this way the amount of blood passing through the capillaries between heart beats equals the whole amount that leaves, the ven- tricle at each succeeding beat, and a constant flow is kept up. The blood rushes very rap- idly through the arteries, slowly but steadily through the capil- laries, and moderately slowly through the veins. During diastole the chambers of the heart enlarge and fill up with blood from the veins. During systole this blood is forced into the arteries. The pulse.—During systole, a wave of muscular contraction begins in the auricles and erids in the ventricles. This sudden and forcible contraction of the heart causes a wave of contrac- tion to run throughout the whole length of the arterial Fic. 165. Diagram of circulation. 1, heart; 2, lungs; 3, head and upper extremities; 4, spleen; 5, intestine; 6, kidney; 7, lower extremities; 8, liver. (After Dalton.) 326 THE ANIMALS AND MAN system. This is the pulse wave. It may be detected by the tip of the finger where the artery lies near the surface, as in the wrist, and the rate of the heart beat counted. This we call “feeling the pulse.” It is used by physicians to deter- mine the condition of the heart; for conditions affecting the heart will change the rate of the pulse beat. Sounds of the heart.—The heart in action makes two sounds, one—a long sound (lub), caused by contraction, and another—a short sound (dub), caused by the closing of the valves. These strokes are repeated about seventy- two times a minute, day and night. Nervous control of the circulatory apparatus.—When an organ is at work it needs a greater supply of blood than when at rest. After a meal the stomach and intestines need a large amount of blood. During exercise, the muscles need a large supply. The caliber of the arteries of any organ is increased or decreased according to the needs of the organ. During activity of the organ, the caliber of its arteries is increased, and hence the organ receives an increased supply of blood. During rest, the caliber of the arteries is reduced and hence part of the blood supply is shut off. This increase and decrease of the caliber of the blood- vessels is effected by the nervous system. There are aug- menting (hastening) and inhibiting (checking) nerve fibers, passing from central nervous ganglia to each blood-vessel. Effects of exercise upon circulation.—During muscular activity, or exercise, the muscles need a large supply of blood. The arteries of the muscles dilate and the heart increases the rapidity of its beat. This results in a rapid supply of blood to the lungs, a quick exchange of carbon dioxide and oxygen, and a large supply of oxygen to the muscle. In the muscle rapid metabolism is in progress which, if not overdone, invigorates the whole system. The heart may be weakened by over exercise or by vigorous exercise at THE BLOOD AND CIRCULATION 327 long intervals only. The heart must be trained by well regulated exercise to respond to all demands upon it. Regulation of heart action.—If a heart is cut off from the living body it goes right on beating for a while. This shows that cardiac or heart muscle differs from any other, since it does not require an impulse from the central ner- vous system to keep up its movements. Inhibitory and acceleration fibers.—The heart is, however, supplied with two kinds of nerve fibers which regulate the force and rate of the heart beat. ‘The acceleration fibers stimulate the heart to beat stronger and faster. The inhibi- tory fibers slow the beat and lessen its strength. The nerve centers where these fibers originate are believed to be stimulated by the products of muscular activity resulting from metabolism. Thus the activity of one organ regulates the activity of another and the work of one is adjusted to the demands of the other. Treatment of cuts and bruises.—In cases of injury where the skin is broken, special precaution must be taken in dressing the wound to prevent bacteria or other microbes from infecting the wound and thus gaining entrance into the circulation. Lockjaw and blood poisoning are diseases that result from such infection. The first thing to do, therefore, is to wash the wound and the skin about the wound with a clean cloth or bit of absorbent cotton and soap, and apply a disinfectant such as weak corrosive subli- mate (1 part to 100 parts water) or peroxide of hydrogen. If a large artery is cut, the high pressure in the arteries will cause the blood to flow out in spurts. In this case, the artery must be bandaged between the wound and the heart. To do this press the artery firmly with the finger until the blood ceases to flow. Then have someone tie a knot in a handkerchief or bandage and twist this loosely about the limb with the knot applied over the artery. Place a stick under the bandage, and twist it until the constriction 328 THE ANIMALS AND MAN is sufficient to check the flow of blood. If a vein is cut the blood will simply ooze out and may of itself form a clot that will stop the wound; if not, the blood flow may be stopped by applying a bandage over the wound, first disin- fecting it and drawing the edges of the wound together. In the case of a bruise, the skin is not broken, but the tissue or blood-vessels beneath the skin are crushed. This may cause a swelling and a dark appearance by the collection of blood and lymph at the spot. Gentle rubbing or a hot or ice-water application will ease the pain and keep down the swelling. Effects of alcohol on circulation.—The use of alcohol may seriously affect the distribution of blood in the body. By weakening the inhibitory impulses, the blood-vessels of the skin become permanently dilated or enlarged so that a large amount of blood is found in the skin. This disarranges the normal adjustment of blood in the tissues. Such a disarrangement is more serious in cold than warm weather because it results in much loss of heat to the body. CHAPTER XXIV THE SKELETON AND MUSCLES Two very important tissues of the body are the bones and muscles. The skeleton (fig. 166A).—The bones, of which there are some two hundred or more in the body, are arranged and joined in such a way. as to form the skeleton. The skeleton fulfills three purposes: (1). It is made use of by the muscles to enable the body parts and the whole body to move about and handle things. (2). It forms a framework to protect the delicate organs of other systems. (3). It gives form and rigidity to the body. In man, as in other vertebrate animals, the axial skeleton is formed of the bones of the skull, vertebral column or ‘backbone, ribs, and sternum. The -bones of the skull protect the brain. The vertebral column encloses the long dorsal nerve cord. The long, flat, curved ribs, articulating at the back with the vertebral column and in front with the sternum, protect the heart and lungs in the thoracic cavity (fig. 159). The large hip bones (pelvic bones, figs. 166,S and 159, P) form a sort of basket for the support of the organs of the abdominal cavity. The bones of the legs and arms form the appendicular skeleton. The leg bones articulate with or join the pelvic bones, pelvic girdle, and the arm bones articulate with the shoulder bones, or pectoral girdle. A comparison of the skele- ton of the toad (fig. 9) with that of man (fig. 166 A) shows that while the different bones vary in relative size and shape, the same regions are laid down in each. 329 Fic. 166 B. Side view of spinal column. C-1 to 7, cervical ver- tebre; D-1 to 12, dor- sal vertebre; L-1 to 5, lumbar vertebra; S. 1. sacrum; Co. 1-4 coccyx. (After Mar- tin.) Fic. 166 A, Bony and cartilaginous skeleton. a, left parietal bone of cran- jum; b, frontal bone; ¢, cervical vertebrae; d, sternum; e, lumbar verte- bre; f, ulna; g, radius; #, carpals; /, meta-carpals; k, phalanges; J, tibia; m, fibula; », tarsal bones; 0, metatarsals; ~, phalanges; g, pa- tella (knee-pan); 7, femur; s, pelvis; ¢, humerus; u, clavicle. (After Martin.) THE SKELETON AND MUSCLES 331 The vertebral column (fig. 166).—The long backbone in man is composed of separate ringlike pieces, called verte- bre, placed one above the other. Each has several lateral pro- jections for the attachment of muscles and for interlocking adjacent vertebre. The vertebre are ' held together by strong ligaments, passing from one ver- tebra to another. The first seven vertebre _ are called cervical or neck vertebra. The | next twelve are the _ dorsal vertebre. To _ each one of these is | attached a pair of ribs, as shown in fig. 167. The last five are the lumbar ver- tebre. The single. large bone below the lumbar vertebre is the sacrum and the | fe, Pets ot Fic. 167. Lower half of thorax with dorsal and lumbar vertebre. A, sixth dorsal vertebre; Ao, aorta; D, (lower) dia- phragm; D, (upper) aorta passing through diaphragm; I, intercostal muscles; O, oesophagus; IV, opening in diaphragm for vena cava ascending; T T, tendons of right and left crura attaching diaphragm curved tip at the end is the coccyx. ‘The to 3rd, and 4th lumbar vertebre. (After sacrum is really com- Allen Thomson.) posed of five vertebre fused together, and the coccyx of four bones fused into one. Each of the twenty-six vertebre differs a little in shape from its neighbor, but all are nicely adjusted to one another. Between the vertebre are pads of elastic cartilage. These act as cushions and prevent jarring of the vertebral column. The ribs.—The ribs, articulating with the twelve dorsal vertebree, are held in place by sheaths of connecting muscles 332 THE ANIMALS AND MAN (fig. 167). Each of the first seven ribs is attached to the sternum or breast bone by a rod of cartilage. The carti- laginous ends of the next three join with the cartilage of the seventh, while the remaining two are the so-called floating , ribs, joined only to the vertebral column (figs. 166 A, and 159). The skull (fig. 168).—The skull is formed by the union Fic. 168. A side view of the skull. F, frontal bone; P, parietal; S, sphenoid; T, temporal; N, nasal; M, malar; S M., superior maxilla; IM., inferior maxilla; O, occipital. (After Martin.) of the cranial and facial bones. They are so fitted to one another that they completely enclose the brain. Some are perforated to admit the passage of nerves and blood-vessels. The sphenoids and ethnoid bones form the floor of the cra- nium. The occipital bone (O) lies at the back of the skull. The temporal bones (T) form the sides. Within the tem- poral bones are embedded the channels of the inner ear. THE SKELETON AND MUSCLES 333 The parietals (P) lie above the temporals and meet on the top of the head. The /fronial bone (F) covers the front part of the brain and forms part ofthe bony socket that protects the eye. The facial bones are those forming the jaws, the sides of the nose and the roof of the mouth. Support of the skull.—The first spinal vertebra, the aélas, supports the skull. This bone articulates movably with the second vertebra called the axis, and permits of much move- ment, as nodding, turning the head, etc. Pelvic and pectoral girdles.—The large pelvic bone (fig. 166 A-s) forms the pelvic girdle and contains the socket of the hip-joint (fig. 171), by means of which the legs are ar- ticulated with the axial skeleton. The collar bones (clavicles) (fig. 159 C) and shoulder blades (scapulas) (fig. 159 S) form the pectoral girdle. The collar bones, one on either side, may be felt just beneath the neck. ‘They articulate with the sternum in front and at their outer extremities with the upper bone of the arm. The two large shoulder blades at the back, the scapulas, are held in place merely by muscles attached to the ribs. At their outer ends they also articulate with the humerus. The pec- toral girdle articulates with the axial skeleton through the clavicles only. This adjustment permits a wide range of motion to the arms. Structure of a long bone.—A bone in a prepared skeleton, or one picked up in the field after it has been exposed to the weather for a long time, shows only the mineral matter of which it is composed. It has lost all of its organic or living material. A fresh bone, procured from the butcher, shows the features indicated in fig. 169. At each end is an enlargement or head, with certain protuberances for the attachment of muscles. The ends are capped with dense white elastic tissue or cartilage (fig. 170d). These are the surfaces that articulate with other bones. The central shaft (fig. 169, X-z) is covered with a sheath of connective tissue, 334 THE ANIMALS AND MAN the periosteum, which is bone- forming material. Surfaces for articulation with other bones are smooth and covered with cartilage (Cpl,Tr and Cp). A bone, sawed through the middle, as shown in fig. 170, exposes a dense layer of hard bone (b) enclosing, at the ends, a spongy mass of bone tissue (c), the spaces of which are filled with red marrow. Here red blood corpuscles are formed. The shaft encloses a space filled with yellow marrow (a). This is rich in fat and gelatin. This struc- ture secures the maximum of strength for a given amount of bone material. In the ribs, or other flat bones, the entire outer wall is dense and hard, while the entire central part is made up of a spongy mass of bone filled with red marrow. Chemical composition of bone.—Bone is formed from materials taken into the body with the food, chiefly lime, salts (mineral matter) and Fic. 169. Right humerus seen from in front. Cp, rounded surface of upper extremity; Tr, Cpl, round- ed surfaces of lower extremity. Tmj, Tm, El, Em, prominences for attachment of muscles; Aa (x--z) central shaft. (After Martin.) THE SKELETON AND MUSCLES organic compounds. Place a small bone in dilute hydrochloric acid and leave it for several days. The acid will dissolve out the mineral matter, leaving the soft parts, the cartilage at the ends, the periosteum and the organic matter of the bone tissue. The bone so decalcified does not lose its shape but can be twisted and bent without breaking. Burn a bone in the fire. The organic matter disap- pears leaving the mineral matter only, which is now white and brittle. The animal matter, therefore, gives the bone flexibility, while the mineral matter gives it stiffness. Bone is nourished by blood that passes in blood-vessels through the periosteum into a series of microscopic canals that perforate the bone tissue. Joints.—Movements between the limbs are accomplished by joints or articulations. There are four classes of joints, the bail and socket, like that of the femur or leg with the hip bone; the hinge joint, as at the elbow or ankle; the gliding joint, as the wrist and knee joints; and the pivot joint as exhibited by the articulation of axis and atlas in the neck. Figure 171 shows a perfect example of a ball and socket joint, the hip joint. On the left, .the femur is shown held in place by bands of strong ligaments (H L) attaching it to the pelvic bone, and so arranged as to give perfect freedom of movement. On Fic. 170. Humerus, bisected —_ length- wise. @, marrow- cavity; 0b, hard bone; c, spongy bone; d, articular cartilage. (After Martin.) the right, these bands have been cut away to show the 336 THE ANIMALS AND MAN rounded head of the femur (F) fitting exactly into the socket and attached to its base by the capsular lig- aments. The surface of the ball and of the socket are each covered with a smooth elastic cartilage to prevent friction. Cover- ing: the inside of the ligaments there is a thin membrane, the synovial membrane, which secretes a thick viscid fluid Fic. 171. Articulation of pelvis and hip-joint seen from before. (The anterior half of the capsular ligament of the left hip-joint has been removed and the femur rotated outwards.) F,femur; H L, capsular ligament of hip-joint; S, sacrum; L, vertebral ligament inserted on sacrum; L I, ligaments inserted on vertebrae. (After Allen Thomson.) called synovial fluid. This acts as a lubricating fluid for joints. In a hinge joint, as at the elbow, the bones are so connected as to admit of motion in only two directions, like a door upon hinges. Dislocation, fractures and sprains.—A dislocation occurs when the bones of a joint are forced out of place. The bones must be replaced at once by a physician. In the meantime the pain may be relieved by hot or ice cold applications. THE SKELETON AND MUSCLES 337 Fractures.—A fracture is a break in a bone, and usually injures the periosteum and other tissues connected with the bone. In an accident of this kind the physician brings the two ends of the bones together and binds them between splints until new bone is formed and the fracture healed. Sprains.—The tearing, or pulling out of place, of a liga- ment and muscles in the region of a joint results in a sprain. The physician must bandage a sprain tightly and the patient must rest the injured parts for many weeks. Relief from pain before the physician comes is afforded by hot applica- tions and by arnica or other liniment. Comparison and composition of skeleton of child and adult.—In very early life many of the bones are formed of cartilage. Later the real bone tissue is formed that sup- plants the cartilage except in the region of the joints. In youth, when bone tissue is first formed it is comparatively soft and flexible, the living or organic part far exceeding the mineral matter. It is for this reason that bones are less easily broken and more quickly repaired in youth than in age. It is for this reason also that young people must exercise much care in standing, walking and sitting correct- ly, for in youth the skeleton is sometimes permanently de- formed by incorrect usage. THE MUSCLES Arrangement and structure.—The muscles in the human body, as in all animals, are the active organs of motion and locomotion. Each muscle constitutes a separate organ, composed of a mass of fibers collected in bundles and im- bedded in connective tissue. The biceps muscle is a mass of muscle fibers on the front part of the upper arm. When the arm is hanging by the side at rest the muscle feels soft. It is then relaxed and at its greatest length. When the arm is bent at the elbow, the muscle is harder, shorter and bulges 338 THE ANIMALS AND MAN slightly. It is now contracted. Fig. 173 shows this muscle in both relaxed and contracted position. A muscle like the = — Fic. 172. Superficial muscles of trunk, shoulder and back viewed from behind. A, external occipital protuberance; 1-1, trapezius muscles; 1’ oval tendon between right and left trapezius; 1” insertion of trapezius; B, summit of shoulder (acronium); 2-2’, lateral muscle and insertion; 3, sterno-mastoid; 4, deltoid; 5, infraspinatus; 6, teres minor; 7, teres major; 8, rhomboideus major; 9, part of external oblique muscle of abdomen. (After Allen Thomson.) biceps is attached to two bones by strong white elastic cords or tendons. One of the attachments serves as a fixed point THE SKELETON AND MUSCLES 339 or point of origin of the muscle; the other as the point of insertion. As the muscle shortens, the bone upon which the muscle is inserted moves. In the biceps, the shoulder blade is the point of origin, the radius of the forearm, the point of insertion. Fig. 174 shows other muscles of the forearm, inserted by tendons. In some parts of the body, as in the back, the muscles lie in sheets, one upon the other, and are attached at different places on the bones so as to render many movements possible (fig. 172). Certain sets of muscles are used for holding the body erect; others are used in moving the whole body, as in walking, running or leaping; others for moving parts of the body as the arms, the jaws, the eyelids, eyes, etc. These muscles are entirely enclosed in a sheath of connec- tive tissue called Fic. 173. Biceps muscle and bones of arm, ‘ y 7 illustrating flexion of elbow joint when ais ane Mk muscle contracts. (After Martin.) ecomes ex at the ends as tendons. From the inner side of this sheath partitions pass inward, separating the groups of reddish muscle fibers into larger and smaller bundles, and binding all together into a distinct muscle. These partitions, or septa, also afford support to the numerous blood-vessels and nerves with which each muscle is supplied. Muscles of this type have been called voluntary muscles because they are for the most part under the control of the will. Such muscles are also called striated muscles from their cross-striated ap- pearance shown under the microscope, “ 340 THE ANIMALS AND MAN There are certain other muscles that form expanded membranes for enclosing cavities. | Fic. 174. Deep view of muscles and ten- dons of right shoulder. A, brachialis anticus; B, tendon of insertion of bi- ceps (biceps removed); C,coracoid pro- cess of scapula; Cl, clavicle; H, humerus; Sc, scapula with attached subscapularis muscle. T-T, triceps. (After Allen Thomson.) These have no definite point of insertion. Such a sheet of muscle by its contractions and relaxa- tions exerts a pressure that affects the move- ments of the contents of the cavity. Examples of this we have already found in the case of the muscles of the heart and arteries. Such also are the muscles of the oesophagus, stomach and intestines. Muscles of this type have been called involuntary muscles be- cause they are regula- ted by the nervous sys- tem without any control of the will. Under the microscope these mus- cles present no appear- ance of striations and so have been called non-stri- ated muscles. Blood and nerve sup- ply.—Since every muscle of the body must be well supplied with nutriment and oxygen for its meta- bolism and for the work it performs, all muscles of the body are richly supplied with blood capillaries. These pene- trate the connective tissues that separate the muscle fibers. THE SKELETON AND MUSCLES 341 To each muscle also a nerve passes, distributing its nerve fibers through the connective tissues to the muscle cells. Without its nerve-supply, any muscle would be useless, for the nerve centers must initiate and control every motion. Hygiene of muscles; necessity for exercise.—Muscular activity is absolutely essential to healthy living, and should therefore be as much a daily habit as eating or sleeping. Take a vigorous walk for a mile or two and note the result. The day may be cold, but the body is soon aglow with warmth, the heart beats more vigorously, the breathing is deep and invigorating. What is taking place in the body? The muscles are undergoing chemical change. Carbon dioxide and other wastes are being thrown into the blood, and large quantities of heat are being liberated so that the temperature of the body rises considerably. This calls for a rapid supply of blood to the muscle cells, that there may be a sufficient supply of food and oxygen. The heart responds by a quickened beat, driving the blood to the needy tissues. The heat regulating apparatus is brought into play. ‘The small arteries of the skin dilate, and perspiration, laden with water and waste, is secreted by the glands of the skin. The blood-vessels of the internal organs constrict, reducing the blood flow to these organs. The respiratory movements become deeper and more frequent, and, probably most beneficial of all, the lymph circulation in the tissues is improved. The lymph having no propelling organ like the blood, is dependent upon the bodily movements, par- ticularly the muscular movements, for its flow. Muscular activity not only aids in the proper circulation of food and oxygen, but in keeping the muscles at a proper tension. An unused muscle becomes soft and flabby, and tires easily when demands are made upon it. Those forms of exercise are most valuable that call into play the greatest number of muscles. Walking is perhaps the best exercise because it exercises most of the body muscles and the 342 THE ANIMALS AND MAN muscles of the lungs and heart, and so “tones” up the whole system. Exercise, to be of most value, should be regular. It should not be taken immediately after a meal, because then blood would be withdrawn from the digestive system at a time when it is particularly needed there. Fatigue and rest.—A feeling of weariness or muscular fatigue follows prolonged exercise at irregular intervals, or exercise of muscles occasionally used. If the heart has not been trained by constant exercise to keep up a vigorous movement of the blood, or if the heart is overworked, the waste matter (carbon dioxide and urea) produced by muscular activity accumulates in the tissues and the feeling of fatigue follows. Thus the waste products, as such, fulfill an im- portant function as indicators that rest is needed. A rest of a few minutes, even, gives the blood time to carry off the waste; and the feeling of fatigue ceases. CHAPTER XXV RESPIRATION AND EXCRETION RESPIRATION Cell breathing.—Cell breathing, the exchange of carbon dioxide for oxygen, or the process of oxidizing the living cell, is the essential act of respiration. The ameeba takes its oxygen from the water which sur- rounds it, and discharges its carbon dioxide into the water. Cells of the body take their oxygen from and discharge car- bon dioxide into the lymph which surrounds them. From the lymph carbon dioxide passes into the blood. The blood carries it to the lungs. The respiratory or breathing appa- ratus is a mechanism for supplying the blood with its needed oxygen and for removing from the blood its load of carbon dioxide. The apparatus may be considered to consist of the lungs and the air passages leading into them. Position and structure of the lungs.—The lungs (figs. 175 and 159 R. L., L. L.) fill the greater part of the thoracic cavity. This cavity is lined by the pleural membrane which folds neatly back over all the organs in the cavity. The lungs are therefore suspended within this sac of pleural membrane. The portion of the membrane covering the lungs is separated from the portion lining the thoracic cavity by a liquid which reduces friction between the two walls. The lungs are shaped to fit around the heart which also lies in this cavity. The thoracic cavity is completely divided into two parts by a partition of connective tissue, within which lie the trachea, the oesophagus and large blood-vessels. One lung lies on 343 344 THE ANIMALS AND MAN either side of the partition. The trachea (fig. 175, 3) divides within the membranes into two branches or bronchi (fig. 175, 4) which pass through the membrane into the lungs. The bronchi divide, in the lungs, into smaller and smaller Fic. 175. Bronchi and lungs, posterior view, showing position of heart. 1, 1, summit of lungs; 2, 2, base of lungs; 3, trachea; 4, right bronchus; 5, branch to upper lobe of lung; 6, branch to lower lobe; 7, left bronchus; 8, branch to upper lobe; 9, branch to lower lobe; 10, left branch of pulmonary artery; 11, right branch; 12, left auricle of heart; 13, left superior pulmonary vein; 14, left inferior pulmonary vein, 15, right superior pulmonary vein; 16, right inferior pulmonary vein; 17, inferior vena cava; 18, left auricle of heart; 19, right ventricle. (After Sappey.) branches, each culminating in a minute vessel or bronchiole (fig. 176) which ends in a small air sac or alveolus. The lungs are in reality masses of these tiny air sacs surrounded by connective tissue. It is through the thin walls of the RESPIRATION AND EXCRETION 345 alveoli that the interchange of carbon dioxide and oxygen, which results in freshening the blood, is made. Air, during respiration, enters through the nostrils into the pharynx (figs. 156, 157). From the pharynx it passes through the glottis into the larynx and trachea. The larynx is the voice-box. The glottis is the opening of the voice-box, closed at times by a flap called the epiglottis. The respiratory and the digestive paths cross in the pharynx. During respira- tion, the epiglottis is open giving free passage for air into the trachea. During feeding it closes over the glottis (fg. 157) so as to admit the passage of food = into the oesophagus only. 2 The heart lies in such a &¢* position (fig. 175) as to be able to send the blood through the pulmonary ar- =§42 teries directly into the lung /y. tissues. The connective OS Fr, 176. A bronchiole. B, entrance; sue lying between the alveoli 4 p, alveolar passage: A c, air cells; I, contains a mass of pulmo- infundibulum, or pouch into which nary capillaries, and each ‘e air cells open. one of the infinite number of red blood corpuscles is exposed separately to the air in the air cells. By this means the hemoglobin of the blood corpuscles is kept saturated with oxygen. The mechanics of breathing movements.—Breathing consists of inspiration, or taking the air through the air passages into the air sacs of the lungs, and expiration, or forcing air from the air sacs of the lungs out through the air passages and nostrils. 346 THE ANIMALS AND MAN To accomplish an inspiration, the thoracic or pleural cavity must be enlarged. The pleural cavity is completely en- closed, being bounded on the front by the sternum, on the sides by the ribs with their intercostal muscles, and on the back by the backbone. The diaphragm forms the floor of the cavity. This is a dome-shaped sheet of muscle (figs. 159, D and 167, D) convex upward. In ordinary breathing, the muscles between the ribs, called intercostal muscles (fig. 167, I), the muscles between the backbone and ribs, called elevators of the ribs, and the muscles of the diaphragm are all brought into play. Contraction of these muscles elevates the ribs and lowers the diaphragm, thus enlarging the cavity. The air rushes in through the air passages and enters the lungs, expanding the elastic lung tissue until it fills the enlarged thoracic cavity. Immediately following inspiration the diaphragm assumes its normal position, the intercostal and elevator muscles relax, and thus the size of the pleural cavity is reduced. The pressure of the walls of the thorax upon the lungs forces the air out and expiration takes place. The walls of the thorax move rhythmically normally sixteen or eighteen times a minute. This rate is increased during exercise. Composition of inspired and expired air.—The es- sential components of air, from a physiological standpoint, are oxygen, nitrogen and carbon dioxide. There are a few other elements, but they have not been shown to have any physiological significance. There are also accidental con- stituents of the air varying with the locality. The following table, given by Howell, represents the composition of ordinary inspired and expired air. Carbon / Nitrogen Oxygen dioxide Water ANS PIPE ded. 5 sense Gakice eee Gus 79 20.96 0.04 SR PITed seit, y Mince 2 a H yim | HAN Fic. 243. Setting-board with but- terflies properly “spread”. (After Comstock.) part powdered alum, cotton, and metric-system measure. Before skinning, the bird should be measured. With a metric-system measure carefully take the alar extent, i. e., 478 THE ANIMALS AND MAN spread from tip to tip of outstretched wings; length of wing, i. e., length of wrist-joint to tip; length of bill in straight line from base (on dorsal aspect) to tip; length of tarsus, and length of middle toe and claw. To skin the bird, cut from anus to point of breast-bone through the skin only. Work skin away on each side to legs; push each leg up, cut off at knee-joint, skin down to next joint, remove all flesh from bone, and pull leg back into place; loosen skin at base of tail, cut through vertebral column at last joint, being careful not to cut through bases of tail- feathers; work skin forward, turning it inside out, loosening it carefully all around, without stretching, to wings; cut off wings at el- bow-joint, skin SSS down to next joint —{—=— and remove flesh ———} from wing-bones; push skin forward eee — i to base of skull, IG. . Setting-board in cross-section to show z @ construction. (After Comstock.) and if skull is not too large (it is in ducks, woodpeckers, and some other birds), on over it to ears and eyes; be very careful in loosening the membrane of ears and in cutting nictitating membrane of eyes; do not cut into eyeball; remove eyeballs without breaking; cut off base of skull, and scoop out brain; remove flesh from skull, and ‘‘poison” the skin by dusting it thoroughly with the powdered arsenic and alum mixture. Turn skin right side out, and clean off fresh blood-stains by soaking them up with corn-meal; wash off dried blood with water, and dry with corn-meal. Corn-meal may be used during skinning to soak up blood and grease. There remains to stuff the skin. Fill orbits of eyes with cotton (this can be advantageously done before skin is re- versed); thrust into neck a moderately compact, elastic, smooth roll of cotton about thickness of the natural neck; REARING AND COLLECTING ANIMALS 479 make a loose oval ball of size and general shape of bird’s body and put into body-cavity with anterior end under the posterior end of neck-roll; pull two edges of abdominal incision to- gether over the cotton, fasten, if necessary, with a single stitch of thread, smooth feathers, fold wings in natural position, wrap skin, not tightly, in thin sheet of cotton (op- portunity for delicate handling here) and put away in a drawer or box to dry. Before putting away tie label to leg, giving date and locality of capture, sex and measurements of bird, and name of collector. Before bird is put into permanent collection it should be labelled with its common and scientific name. The mounting of birds in lifelike shape and attitude is hard to do successfully; and a collection of mounted birds demands much more room and more expensive cabinets than one of skins. For instructions for the mounting of birds see Davie’s “Methods in the Art of Taxidermy,” pp. 39-57; or Horna- day’s ‘“Taxidermy and Zoological Collecting.” For a more detailed account of making bird-skins, see also these books, or Ridgway’s “Directions for Collecting Birds.” In collecting birds’ nests cut off the branch or branches on which the nest is placed a few inches above and below the nest, leaving it in its natural position. Ground-nests should have the section of the sod on which they are placed taken up and preserved with them. If the inner lining of the nest consists of feathers or fur put in a ‘“‘moth-ball” (naphthaline). To preserve birds’ eggs they should be emptied through a single small hole on one side by blowing. Prick a hole with a needle and enlarge with an egg-drill (obtain of dealers in naturalists’ supplies, see p. 464). Blow with a simple bent blowpipe with point smaller than the hole. After removing contents clean by blowing in a little water, and blowing it out again. After cleaning, place the egg, hole downward, on a layer of corn-meal to dry. Label each egg by writing on it near the hole a number. Use a soft pencil for writing. This number should refer to a record (book) under similar number, or to an “egg-blank,” 480 THE ANIMALS AND MAN containing the following data: name of bird, number of eggs in set, date and locality, name of collector, and any special information about the eggs or nest which the collector may think advisable. The eggs may be kept in drawers or boxes lined with cotton, and divided into little compart- ments. For detailed directions for collecting and preserving birds’ eggs and nests, see Bendire’s ‘Directions for Collecting, Preparing, and Preserving Birds’ Eggs and Nests,” or Davie’s “Methods in the Art of Taxidermy,” pp. 74-78. *Mammals.—Any mammal intended for a scientific speci- men should be measured in the flesh, before skinning, and as soon after death as practicable, when the muscles are still flexible. (This is particularly true of larger species, such as foxes, wildcats, etc.) The measurements are taken in millimetres, a rule or steel tape being used. (1) Total length: stretch the animal on its back along the rule or tape and measure from the tip of the nose (head extended as far as possible) to the tip of the fleshy part of tail (not to end of hairs). (2) Tail: bend tail at right angles from body back- ward and place end of ruler in the angle, holding the tail taut against the ruler. Measure only to tip of flesh (make this measurement with a pair of dividers). (3) Hind foot: place sole of foot flat on ruler and measure from heel to tip of longest toe-nail (in certain small mammals it is necessary to use dividers for accuracy). The measurements should be entered on the label, along with such necessary data as sex, locality, date, and collector’s name. Skin a mammal as soon after death as possible. Lay mammal on back and with scissors or scalpel open the skin along belly from about midway between fore and hind legs to vent, taking care not to cut muscles of abdomen. Skin down on either side of the body by working the skin from flesh with fingers till hind legs appear. Use corn- meal to stanch blood or moisture. With left hand grasp *The following directions for making skins of mammals were written for this book by Professor W. K. Fisher of Stanford University, an experi- enced collector. \ REARING AND COLLECTING ANIMALS 481 a leg and work the knee from without into the opening just made; cut the bone at the knee, skin leg to heel and clean meat off the bone (leaving it attached of course to foot). In animals larger than squirrels skin down to tips of toes. Do the same with other leg. Skin around base of tail till the skin is free all around so that a grip can be secured on body; then with thumb and forefinger hold the skin tight at base of tail and slowly pull out the tail. In small mammals this can be done readily, but in foxes it is often necessary to split the skin up along the under side and dissect it off the tail-bones. After the tail is free skin down the body, using the fingers (except in large mammals) till the fore legs are reached; treat the fore legs in the same manner as hind legs, thrusting elbow out of the skin much as a person would do in taking off a coat; cut bone at elbow; clean fore-arm bone. Skin over neck to base of ears. With scalpel cut through ears close to skull. With scalpel dissect off skin over the head (taking care not to injure eyelids) down to tip of nose, severing its cartilage and hence freeing skin from body. Sew mouth by passing needle through under lip and then across through two sides of the upper lip; draw taut and tie thread. Poison skin thoroughly. Turn skin right side out. Next sever the skull carefully from body, just where the last neck-vertebra joins the back of the skull. It is necessary to keep the skull, because characters of bone and teeth are much used in classification. Remove superfluous meat from the skull and take out brain with a little spoon made of a piece of wire with loop at end. Tag the skull with a number corresponding to that on skin, and hang up to dry. A finished specimen skull is made by boiling it a short time and picking the meat off with forceps, further cleaning it with an old tooth-brush, when it is placed in the sun to bleach. Care must be taken always not to injure bones or dislodge teeth. Mammals are stuffed with cotton or tow; the latter is used in species from a gray squirrel up. Large mammals stuffed with cotton do not dry readily, and often spoil. Being much thicker-skinned than birds, mammals require 482 THE ANIMALS AND MAN more care in drying and ordinarily require a much longer period. Soft hay may be substituted for tow; never use feathers or hair. Roll a longish wad of cotton about the size of body and insert with forceps, taking care to form the head nearly as in life. Split the back end of the cotton and stuff each hind leg with the two branches thus formed. Roll a piece of cotton around end of forceps and stuff fore legs. Place a stout straight piece of wire in the tail, wrapping it slightly to give the tail the plump appearance of life. (If the cotton cannot be reeled on to the wire evenly, leave it off entirely.) Make the wire long enough to extend half way up belly. Sew up slit in belly. Lay mammal on belly and pin out on a board by legs, with the fore legs close beside head, and hind legs parallel behind, soles downward. Be sure the label is tied securely on right hind leg. For directions for preparing and mounting skeletons of birds, mammals, and other vertebrates, see the books of Davie and Hornaday already referred to. Fishes, batrachians, reptiles, and other animals.—The most convenient and usual way of preserving the other vertebrates (not birds or mammals) is to put the whole body into 85 per cent alcohol or 4 per cent formalin. Batra- chians should be kept in alcohol not exceeding 60 per cent strength. Several incisions should always be made in the body, at least one of which should penetrate the abdominal cavity. Anatomical preparations are similarly preserved. By keeping the specimens in glass jars they may be examined without removal. Fishes should not be kept in formalin more than a few months, as they absorb water, swell, and grow fragile. Of the invertebrates all, except the insects, are preserved in alcohol or formalin. The shells of molluscs can be pre- served dry, of course, in drawers or boxes divided into small compartments. END INDEX References to illustrations are indicated by an asterisk (*). A Abdomen and viscera in human body, *309 Absorption in human body, 313; object, 313; where it takes place, 313; of sugar, 313; of fats, 313; of water, 314; of salts, 314; of alcohol, 314 Aenigmatis blattoides, *424 Agalendiz, 168 Age, old stone, 390; paleolithic, 390; newer stone, 391; neolithic, 391; metal, 391 Ages, geologic table of, 281 Air, composition of inspired and expired, 346; quantity breathed, 347; tidal, 347; residual, 347 Akka pygmy, *397 Alcohol, absorption by human body, 313; effect upon digestion, 315; effect on circulation, 328; effect on nervous system, 366 Alimentary canal of human body, structure, 303; function, 303; diagram, *304 Alligators, 212 Alveolus, 344 Ameeba, structure and_ behavior, 38; changing shape, *39 Amylopsin, 312 Anatomy, definition, 1 Anopheles maculipennis, mosquito, *128 malarial Anosia plexippus, *447 Antelocapra americana, *252 Antelope, *252 Antenna of carrion beetle, bearing smelling pits, *72 Ants, fly guest of, *424; social para- sites of, 425 Aorta in human body, 320, 321; branches, 322 Apes, 256 Apis mellifica, queen, drone and worker, *433 Aquaria, how to prepare, 469 Aquarium, battery jar, *472 Arachnida, 149, 162 Arachnoid membrane, body, 358 Argiope, 169 Aristolochia clematitis, *458 Arm of man, diagram to show how the bones and muscles act, *53 Arrow head of ancient man, *386 Artery in human body, aorta, 320; pulmonary, 320; phrenic, 322; coeliac axis, 322; superior mes- enteric, 322; renal, 320, 322; infer- ior mesenteric, 322; coronary, 322 Arthropoda, 149 Artiodactyla, 250 Ascidian, *193 Asclepias flowers, honeybee at, *456 Association centers in human brain, ¥*363 in human 483 484 Asterias, starfish, dissection, *141 Astigmatism, 375 Atlas, in human body, 333 Attide, *168 Auditory sensations of man, 376 Auk, razor-billed, *223 Auricle of human heart, 318 Axis, in human body, 333 Axis cylinder, 363 Axon, 363 B Bacilli, 379 Back swimmer, *159; 160 Bacteria, 379; beneficial, 380; harm- ful, 380; causing decay of teeth, 306 Bagworm, *404 Balanus, *152 Banteng, *267 Barnacles, *152; California, *172 Barriers, in animal distribution, 407 Basilarchia archip pus, showing mim- icry, *448 Bat, hoary, #248 Batrachians, 200; how to preserve, 482 Bear, 254 Beaver, 246 Bees, carpenter, nest of, *428; soli- tary, 427; social, 428; nests of mining, *429 Beetle, Australian lady bird, *181; carrion, antenna, *72; guest of termite, *424; whirligig, 159; water scavenger, 159; predaceous diving, *159 Bile, in small intestine, 311, 312; reaction of, 312 Birds, body form and structure, 214; development and life history, 218; classification and _ identification, INDEX 220; migration, 221; breeding and nesting, 223; external parts named, *16; life history, 102; nests, 103; nest building, 103; rearing of young, 103; giant toothed, fossil skeleton,. *282; how to collect, skin and _ stuff, 477, domesticated kinds, 269; structure and habits, 227; food habits, economics and protection, 233, Birth, 83 Bison bison, *253 Bladder, urinary, 350 Blood in human body, function, 316; composition of, 316; corpuscles, 316; plasma, 316, 317; structure, 316; clotting, 316; amount, 317; distribution, 317; effect of food, fresh air and rest on, 317; changes in capillaries, 323; purification, 323; vessels, 318; vessels con- nected with heart, 319; circula- tion in live fish, 11 Boar, wild, *266 Bombus, *430 Bone in human body, structure, 333; chemical composition, 334; nour- ishment, 335; frontal, 333; collar, 333; sphenoid, 332; ethnoid, 332; occipital, 332; temporal, 332; parietal, 332 Books, references, 466 Bos sondaicus, *267 Bovide, 253 Brachynotus nudus, crab, *152 Breathing, of man, mechanics, 345; hygiene, 347; effects of exercise on, 347 Brain of cat, *67; structure of hu- man, 358; internal structure of human, 361; ventral view of hu- INDEX man, *359; of vertebrates, *66 Branch, defined, 115 Branches, of animals, list, 116 Bronchi, in human body, 344 Bronchiole, in human body, dia- gram, *344; 345 Brontosaurus, *276 Buffalo, *253 Bull, shorthorn, prize, *269 Bumble bees, social life, 428; nest, *430 Burns, treatment, 356 Butterfly, owl, *438; dead leaf, *445; scales of, *439; part of wing showing scales, #440; *441; diagram showing scales of wing, *442; larve of Monarch, *446; Monarch, *447; Viceroy showing mimicry, *448; Parnassius, *407; violet-tipped, larve, *94; pupa, *96; swallow tail, *163; how to spread wings, *477; *478 C Cage for breeding insects, *470; *471 Calf, taste papilla, *71 Caligo, *438 Callorhinus atascanus, *255 Callorhinus ursinus, killed by para- sites, *419 -Calory, 300 Canary birds, domesticated races, 271 Cancer productus, *152 Canide, 254 Canis niger, *262 Capillaries, in human body, 322, 324 Carbo-hydrates, composition, 291, 296; as food nutrient, 295; as proteid sparer, 297 Carbon, as a cell element, 291; in 485 proteid, 291, 296; in carbo-hy- drate, 291; in fat, 291; in Prop- erties, 293 Carbon dioxide, 291; Gass 294; exchange in lungs of man, 324 Cartilage, 331 Cat, domesticated races, 263; skele- ton, *52; muscles of fore leg, *53; brain, *67 Caterpillars, structure and habits of, 92 Catfish, 195 Cattle, domesticated races, 266; heads of British breeds, *268; Cell, characterized, 46; function, 289; chemical composition of, 291; breathing, 343; chemistry, 291; as a unit of life, 288; living substance of, 288 Centipede, *156; skein, *155; *156 Centrurus, *164 Cephalopoda, 171 Cercopithecus, *257 Cerebellum, of man, 359 Cerebro-spinal fluid, of man, 358 Cerebrum, of man, 358 Cervide, 251 Cervus canadensis, *251 Cete, 249 Charcoal, 293 Chemistry of the cell, 291 Chickens, domesticated races, 269 Chipmunk, *247 : Chiroptera, 248 Circulation, in human body, 318; systemic, 319; pulmonary, 324; how maintained, 324; effect of alcohol on, 328; effects of exercise on, 326; diagram, *325 Circulatory system, of man, 290; of young dragon fly, *62; of fish, *63 486 Clams, 171 Class, defined, 114 Classes of animals, list, 116 Classification, 192; of animals, 107; example, 110; table, 116 Clavicle, in human body, 333 Cleanliness, importance, 356 Coagulation, 317 Cocci, 379 Coccyx, in human body, 331 Cock, Polish, *273 Cockerel, silver-laced wyandotte, *273 Coelenterata, 139 Colaptes auratus, *231 Collections, high school, 473; how to make, 469, 473 Colors of animals, 438; uses of, 442; how produced, 441; warning, 446 Columba livia, domesticated varie- ties, *260 Combustion, 291 Commensalism, 421 Communal life, 426 Condiments, 300 Constipation, 314 Copper head, 211 Corals, 136 Corisa, *161 Cormorants, domesticated, 272 Corpus callosum, 359 Coyote, 254 Crab, 151, *152; hermit, with polyp on shell, #423 Crayfish, 149; anatomy, 28; ven- tral aspect and appendages, *29; internal structure, *33 Crocodiles, 212 Cross-pollination, 452; by insects, 452 Crustacea, 149 Cuticle, of human body, 352 INDEX Cuttlefish, 178 Cyclas, 171 D Damp-bug, *154 Decapoda, 178 Deer, 251; extinct, 283 Deglutition, 308 Dendrites, 363 Dentine, 306 Dermacentor americanus, *166 Dermis, of human body, 352 Development of animals, 81 Devil fish, 179 Diaphragm, in human body, 309, 346 Diastase, 312 Diastole, 325 Dictynide, 168 Didelphys virginiana, 245 Diemyctylus torosus, 203 Diet, standard, 299 Diffusion, 298 Digestive system, of man, 289 Digestion, in human body, defined, 303; first step in, 307; of starch, 307; in stomach, 311; in small intestine, 312; experiment in arti- ficial, 312; effect of alcohol on, 315 Dinosaur, extinct three-toed, *284 Diphtheria, 380 Disease, human, caused by one- celled animals, 124 Disinfection, 381 Dislocation, 336 Distribution of animals, 406, 409 Dog, 254; ancient Assyrian, *259; domesticated races, 263, 271; ner- vous system, *67 Dolichorhynchus osborni, fossii ske]- eton, *279 INDEX Dolphins, 249 Domestication of animals, 258 Donkeys, 265 Doves, domesticated races. 269 Dragon fly, circulatory system, *62 Drawings, student, 462 Dura mater, 358 Dyticus, larva, *160 E Ear, function and organs, 72; of man, external part, *72; struc- ture, 376; *375; care of, 377; of locust, *73 Earthworm, dissection, *144 Echinodermata, 140 Eft, western brown, *203 Elk, #251 Empidonax fulvifrons pygmeus, ¥*225 Emulsification, 312 Enzyme, defined, 307; in gastric juice, of man, 310; im intestinal fluid, 312 Epeiride, 168 Epialtus productus, *152 Epidermis, of human body, 352 Epiglottis, of human body, 308, 345 Eumecus skelionianus, *206 Eustachian tube, in man, 376 Excretion, in man, 350 Excretory system, of human body, 290 Exercise, effect upon heart, 326 Expiration, 346 Eyes, of man, structure, 370; func- tions, 370; formation of image in, 373; accommodation, 373; hygiene, 374; section, *372; of moth, part of section showing ele- ments, *77; of jelly fish, *75; of vertebrate, *76; of horse fly, *76, 487 compound, 77; of various ani- mals, 75 F Family, defined, 114 Fatigue, 342 Fats, composition, 291, 298; as food nutrient, 295; characteristics, 298; tests for, 298 Febling’s solution, 297 Felide, 256 Fere, 254 Fertilization of plants, 451 Fever, Texas cattle, caused by pro- tozoan parasite, 130; yellow, caused by protozoan parasite, 130 Fibrin, 317 Fish, 194; as food, 199; hatcheries, 199; circulatory system of, *63; domesticated races, 272; how to preserve, 482 Flounder, *197 Flowers and insects, 450 Fly, guest of ant, *424 Fly catcher, buff breasted, *225 Food, how animals obtain and digest, 59; necessity to animals, 54; spe- cial means of getting, 401 Food nutrients, 294; oxidation, 294,, function, 295; accessories, 300; Foods, chief substances in, 291; composition, 296; relative value, 289; principles involved in cook- ing, 299; economy in purchase, 300 Fossils, how formed, 277; animals, 275 Fowl, wild jungle, #272 Foxes, 254 Fracture, 337 Frog, 201; eggs and hatching of, 97; life history, 97; tree, *202 488 G Gall bladder, in human body, 312 Galley-worm, *155, 156 Gallus bankiva, *272 Gastric fluid, of human body, 310 Gastropoda, 171 Gavial, 213 Geese, domesticated races, 271 Gila monster, *207 Glands, 310; gastric, 310; pyloric, 310; fundus, 310; sweat, 354; lachrymal, 371; section of py- loric, *310; sebaceous, 354 Glires, 245 Glomerulus, in human body, 351 Glottis, in human body, 308 Glycerine, 312 Goats, domesticated races, Rocky Mountain, 253 Goniomena vertens, *138 Gophers, 246 Grantia, a simple sponge, *133 Grape sugar, test for, 297 Grapla, part of wing showing scales, *441 Guinea pigs, 246 Gulls, #233 267; H YZemamobe, malarial, *126; *127; Hemoglobin, 316; function, 316 Hair, 354 Hairworm, 146 Harporhynchus redivivus, *232 Hatching, 83 Hearing, 368 Heart, of man, structure and posi- tion of, 318; internal structure of, 318; valves of, 318; action of, 321; beat of, 321; sounds of, 326; effect of exercise on, 326; dia- gram showing valves, *319; +320; opened, *321 INDEX Heat, generation in body, 294 Heloderma horridum, *207 Hesperorinus regalis, fossil skeleton, #282 Hippocampus kelloggi, *198 Hog, domesticated races, 266 Homo, primigenius, 390, 394; sa- piens, 390, 394 Honeybee, queen, drone, worker, *434° brood cells, *435; life, 429; observation hive, *431; gathering pollen and nectar, *432; building comb, *433; at Asclepias flowers, *456 Horse, domesticated races, 264; American trotting, *264; four- toed, *265; extinct, fossil, 283 Horsefly, eye, cornea, *76 Hottentot Venus, head, *395 House-flies, fighting, 187; foot, *188 Humerus, *334; section of, *335 Humming bird, nest, *103; ruby throat, nest and eggs, *221 Hydra, structure and habits, 134; *135 Hydrochloric acid, in human body, 310; action of, 310 Hydrogen, as a cell element, 291; in proteid, 291, 296; in carbo- hydrate, 291; in fat, 291 Hygiene, laws, 288; of eating and digestion, 314; of muscles, 341; of the nervous system, 365; of the eyes, 374; public, 382 Hygrotrechus, *158 Hyla arenicolor, *202 Hypermetropia, 375 I lcerya purchasi, *181 Immunity, 381 Indians, picture writing of, *385 INDEX Insecta, 149 Insects, 157; and flowers, 450; fighting, 180; guests of ants, 424; domesticated kinds, 273; cross- section of thorax to show muscles and exo-skeleton, *51; cross-pol- linating flowers, 452; remedies for injurious, 183; how to kill and preserve, 474; how to pin up, *476; parasitic, *414; killing bottle, *474 Insecticides, 184 Insectivora, 247 Inspiration, 346 Intestine, in human body, structure of small, 311; coats of small, 311; villi of small, 311; glands of small, 311; digestion in small, 311; mu- ous membrane of small, *311; large, 314 Invertebrates, 132 Iron oxide, 292 Isopod, *154 J Jelly fish, 136, 138; eye, *75 Joints, defined, 335; ball and socket, 335; hinge, 335; gliding, 335; pivot, 335 Jordan, D. C., on effect of alcohol, 366 Julus, *155; 156 K Kallima, *445 Kidneys, in human body, structure and function, 350; section, *351 Koch, Robert, 380 L Laboratory, material for use in, 463 Lacteals, in human body, 313 489 Lark, horned, *234 Larynx, of man, 308, 345 Lasiurus cinereus, *248 Le&ch, 145 Lemurs, 256 Leucocytes, in human body, 317 Life history, defined, 83; of mos- quito, 85 Ligaments, in human body, capsu- lar, 336 Lipase, 312 Liver, of man, position, 312; secre- tion, 312; action, 314 Lizard, *206; thunder, extinct, *276 Lobster, 151 Locust, ear, *73; external parts named, *4; on wild oats, *2 Louse, biting bird, *418 Lumbricus, earthworm dissection, *144 Lungs and bronchi, of man, *344 Lungs, position and structure, in man, 344 ; Lycena, part of wing showing scales, *440 Lycoside, 167, *168 Lymph, in human body, 323; com- position and uses, 323 Lymphatics, in human body, 313 M Malaria, 380; caused by protozoa, 125; mosquito which spreads, *128; parasite, life history, *126; *127 Mammals, 237; body form and structure, 239; development and life history, 243; instinct and reason, 243; classification, 244; carnivorous, 254; how to skin, 480; man-like, 256; various do- mesticated, 269 490 Mammoth, drawing by ancient man, 4387 Man, jawbones of ancient and mod- erm, 256; *393; internal part of ear, *72; tactile corpuscle of the skin, *70; parasites of, 418, an- cient and modern, 384; age of, on earth, 384; ancient life, 386; Neanderthal, remains, *390; Spy, remains, %*392; races, 393; Ethiopic race, 394, 398; Mon- golic race, 394, 396; Caucasic, 394, 396; American, 394, 396; ancient, arrow head of, *386; drawing of, by himself, *389; bones, 389; works, 392 Mantis, preying, *403 Margaropus annulaius, Texas fever tick, *130 Marrow, 334 Marsupialia, 245 Martisia xylophaga, *175 Material for laboratory, how to ob- tain, 465 May fly, 161; young, *162 Medulla oblongata, of man, 360 Medusa, *138 Melanoplus sp., ear, *73 Meleagrina margaritifera, 174 -Merula migratoria propinqua, *229 Mesentery, in human body, position, 311 Metabolism, definition, 289; essentials for, 289 Mice, 246 Microorganisms, 379 Millipede, *155 Millon’s test, 296 Mimicry, 448 Mites, 164; cheese, *165 Moles, 248 Mollusca, 169 three INDEX Mollusk, burrowing, *174, *175 Monkeys, 256; *257 Mosquitoes, fighting, 189; eggs, larvee and pupe, *189; eggs and hatching, 85; larvae, 86; all life stages, *87; life history, 85; pupa 89; external structure, 90; distri- bution, 91; sucking beak of fe- male, *91; malarial, *128 Moth, gypsy, 182; eye, part of sec- tion showing elements, *77; Ache- mon sphinx, *93; codlin, spray- ing against, *184; Sphinx, para- sitized larva, *416; Sphinx, suck- ing proboscis, *402; mimicking wasps, *448 Motions of animals, kinds and how performed, 50 Mouth, 303 Mouth cavity, of man, diagram, *305 Multiplication of animals, 79 Muscle, in human body, arrange- ment and structure, 337; biceps, 337; ¥*338; contraction, 337; re- laxation, 337; voluntary, 339; striated, 339; nonstriated, 340; involuntary, 340; blood supply, 340; nerve supply, 340; hygiene, 341; of trunk, shoulder and back, *338; of shoulder, #340 Muscular system, 290 Mussels, California, *172 Mustelide, 254 Mya arenaria, 172 Myopia, 375 Myriapoda, 149, 155 N Nails, 353 Narcotics, 302 Nautilus, pearly, 179 Necessity of food and fresh air, 366 INDEX Negrito-Papuan, head, *396 Nest of humming bird, *103; of oriole, *104 Nerves of dog, *66; in human body, cranial, 360; optic, 359; com- misural, 364; efferent, 364; motor, 364; sensory, 364; fifth cranial, branches, *360 Nerve fibers, classification, strain, 365 Nervous system, 65; types, *68; in human body, 290; hygiene, 365; effect of alcohol on, 366; central organs, *358 Neurone, structure, 363 Nicotine, 302 Nirmus prestans, *418 Nitrogen, in proteid, 296; elimina- tion from cells, 295 Note books, student, 462 Novius cardinalis, *181 Nudibranch, 177 Oo 364; Octopoda, 179 Octopus, 179 Oesophagus, of man, 308; peristal- tic contraction, 308 Olfactory lobes, in man, 359 Ommatostrephes californica, *178 Onychophora, 149 Opossums, 245 Oriole, nest, *104 Osmosis, 298; experiment showing, 299; in small intestine, 313; in capillaries, 323 Osmotic pressure, 299 Ostrea virginiana, *173 Ostriches, #228; *230; domesticat- ed, 272 Otocoris alpestris, *234 Ovis arkal, *271 Agi Owl, barn, #224 Oxidation, definition, 291; in the body, 294 Oxygen, as a cell element, 291; in proteid, 291, 296; in carbohy- drate, 291; in fat, 291; proper- ties, 291; affinity, 292; method of obtaining pure, 292; apparatus for collecting, *293; necessity to animals, 55 Oyster, #173; pearl, 174; crabs, 153 P Pagurus samuelis, *152 Palate, of man, 304; soft, 304 Pancreas, of man, 312; secretion of, 312 Panther, 256 Papilo rutulus, *163 Paramcecium, structure and be- havior, 41; *40 Parasite, malarial, life history, *126; *127; of Sphinx moth larva, *416; degeneration, 411; internal, 413; of man, 418 Parnassius smintheus, +407 Pasteur, Louis, 380 Peacocks, domesticated races, 271 Pectoral girdle, of man, 329, 333 Pelecypoda, 171 Pelvic girdle, of man, 329, 333 Pelvis, of man, *336 Pepsin, 310; action of, 310, 312 Peptone, 312 Pericardium, in human body, 318 Perimysium, 339 Periosteum, 334 Peripatus eiseni, *149 Perissodactyla, 250 Peritoneal membrane, body, 310 Peritoneum, in human body, 308 in human 492 Perspiration, 354 Pests, fighting insect, 180 Phagocytes, 316 Pharynx, of man, 308 Philampelus achemon, *93 Phoebe, black, nest and eggs, *219 Pholas, *174 Phosphorus, as a cell element, 291; properties, 294 Physiology, definition, 1; animal, 49; human, defined, 287; pur- pose of study, 288 Pia mater, 358 Picture writing, Indian, *385 Pigeons, races of, *260; 270 Pill-bug, 154 Pinnotheres, 153 Pithecanthropus ¥391 Pituophis bellona, *208 Plants, as proteid manufacturers, 296; as source of proteids, 296; as starch manufacturers, 297 Plants, fertilization of, 451 Plasmodium, malarial, *126; *127 Plectrophenax nivalis, *234 Plesiosaur, fossil skeleton, ‘*279 Pollicipes polynemus, *152 Pollination of flowers, *450 Polygonia interrogationis, larve, *94; pupa, *96 Pons varolii, in man, 360 Porcupines, 246 Porpoise, 249 Primates, 256 Protection, special means, 403 Proteids, composition, 291-297; as nitrogenous compounds, 291; as food nutrient, 295; as flesh-pro- ducers, 296; as tissue-formers, 295; tests for, 296 Protoplasm, described, 48 erectus, remains, INDEX Protozoa, 118; form of body, 118; marine, 120; causing human dis- ease, 124 Pseudopleuronectes americanus, *197 Ptyalin, 307 Pulse, 325; 326 Puma, 256 Pupation of caterpillars, 95 Pigmy, *397 Piroplasma, germ of Texas cattle fever, 130 Q Quarantine, 381 Quohog, 171 R Rabbits, 246 Rats, 246 Reflex action, 364; inhibition, 364; simple arc, diagram, *362 Reindeer, drawing by ancient man, #388 Remedies for injurious insects, 183 Rennin, 310; action of, 310 : Reptiles, 203; how to preserve, 482 Resemtblances, protective, 442; spe- cial protective, 444 Respiration, character and organs, 56; essential act of, 343; effect of exercise on, 347; effects of tight clothing on, 348; artificial, 348 Respiratory organs of mouse, *58; system, 290 Rest, 342 Retina, 372; formation of image on, diagram, *372 Robin, western, *229 Rodents, 245 Rosalina varians, *122 Roundworm, 146 Ruminants, 250 INDEX Ss Sacculina, *412 Sacrum, 331 Salamander, western brown, *203; tiger, *204 Saliva, action of, 307 Salivary glands, of man, 307 Salmo irideus, *196 Salmon, 196, 199 Salts, inorganic, function, 298 Sanitation, 382 Sayornis nigricans, nest and eggs, *219 Scale, cottony cushion, *181; San Jose, *185; *186 Scapula, of man, 333 Schoolroom, equipment, 461 Scientific names, 110 Scolopendra, *156 Scorpion, *164; successive positions of body and legs in walking, *49 Scutigera forceps, *155; 156 Sea-anemone, 136 Sea-horses, 197; *198 Seals, 254; fur, *255; killed by parasites, *419 Sea-squirt, *193 Sea-urchin, 140 Selection by nature, 401 Sense, organs, special, classification, 368, 290 Senses, special, and their organs, 69 Sepia, 178 Sheep, domesticated races, 267; American merino, *270; Rocky Mountain, 253; wild *271 Shells, sea, 177 Ship-worm, 175 Shoulder blades, in human body, 333 Shrews, 247 Sight, of man, 368, 370, 374; func- tion and organs of, 75 Silkworm, domesticated, 274 Skeletal system, in man, 290 Skeleton, of man, *330; functions, 329; axial, 329; appendicular, 329; comparison in adult and child, 337 Skin as an excretory organ, 350; functions, 352; structure, 352; as a heat regulator, 355; section, #353; touch papilla, *369 Skink, blue-tailed, *206 Skull, *332; structure, 332; support, 333 Sleeping sickness, caused by proto- zoan parasite, 130 Slug, California giant yellow, *176 Smell, organs and function, 71; of man, 370 Smelling pits of antenna of carrion beetle, #72 Snails, 176; pond, external struc- ture, 5; in aquarium, *6 Snakes, 208; gopher, *208; garter, *209; king, *210; rattle, 211; rattle, rattles, *211; rattle, poison fangs, *212; rattle, remedies, 212 Snake, glass, 207 Snowflake, *234 Social life, 426 Sparrow, English, external struc- ture, 12; *13; habits, 18; feath- ers, types, 14; parts, *14, wes- tern chipping, *220 Species, defined, 112 Spider, 165; eyes and mandibles, *166; spinnerets, *167; hunting, 167; trap door, *167; jumping, *168; running, *168; web-weav- ing, 168; crab, 167, *168 Spinal column, *330; cord, struc- ture, 362 Spinnerets of spider, 167 494 Spirilla, 379 Spizella socialis arizona, *220 Sponges, 133; example of, *133; skeleton, *134 Spontaneous generation, 80 Sprain, 337 - Spraying, apple trees, *184; mix- tures for, 184 Spreading of animals, 408 Squid, 179; giant, *178 Squirrels, 247 Starch, manufactures, 297; test for, 297 Starfish, 140, *140; dissection, *141 Steapsin, 312 Stentor, *121 Sterilization, 381 Sternum, in human body, 332 Stimulants, 301 Stomach, in man, form and struc- ture, 308; asa food reservoir, 311; digestion in, 311 Struggle to live, 399, 400 Suffocation, 348 Sulphur, as a cell element, 291; properties, 292; in proteid, 296 Sun animalcule, *119 Sunfish, 194; external structure, 8; Eupomotis sp., *9; habits, 12 Swan, domesticated races, 269 Synovial membrane, in human body, 336; fluid, 336 Systems of the human body, 289; functions of, 290 Systole, 325 T Tactile corpuscle of the skin of man, *70 Tadpoles, structure and habits, 98; *99 Tapeworm, *147; *415 INDEX Taste, function and organs, 70; in man, 368; papilla of calf, *71 Teeth, 305; structure, 305; kinds, 305; care, 306 Temperature, regulation in body, 355. Tendon, 339 Teredo, 175 Termites, insect guests of, beetle guest of, *424 Termitogaster texana, *424 Testudo, *205 Texas cattle fever, caused by proto- zoan parasite, 130; tick, *130 424; Thalessa, *417 Thamnophis parietalis, *209 Theobaldia incidens, eggs, and pupe, *189 Theridide, 168 Thomiside, 167, *168 Thorax, and viscera, in human body, *309; showing skeleton and dia- phragm, *330 Thrasher, sickle-billed, *232 Thrush, russet-backed, *217 Ticks, 164; dog, *166; wood, *166; Texas fever, *130 Toad, 201; horned, 207; anatomy, 19; dissection, *22; eggs and hatching, 97; life history, 97; in garden, *98; *101 Tongue, 303; showing taste papilla, *370 Tools of ancient man, *394 Tooth, vertical section, *306 Torpedo, electric, 198 Tortoise, Galapagos, land, 205 Touch, sense, 70; in man, 368; skin papilla, *369 Trachea, 343 Trachina spiralis, 147; *414 Tremex, ¥417 larve, INDEX 495 Trochilus colubris, nest and eggs, *221 Trout, rainbow, *196 Triceratops, extinct, *284 Trypsin, 312 Tuberculosis, 380 Turdus ustulatus, *217 Turkeys, domesticated races, 271 Turtles, 205 Tylosaurus dyspelor, fossil skeleton, *278 Typhoid fever, 380 Tyroglyphus siro, *165 U Ungulata, 250 Urea, 317 Ureter, 350 Uvula, 304 Vv Valves of heart, of man, mitral, 318; tri-cuspid, 319 Veins, in human body, pulmonary, 320; portal, 314; vena cava as- cending, 323; vena cava descend- ing, 323; renal, 350; coronary, 320 Veliger, 171 Ventilation, 349 Ventricle, of heart of man, 318, 319 Venus mercenaria, 171 Vermes, 143 Vertebre, of human body, 331; cer- vical, 331; lumbar, 331; sacrum, 331; coccyx, 331 Vertebral column, 331 Vertebrate, diagram of eye, *76 Vertebrates, structure, 191 Villi, of small intestine, 311 Vinegar-eel, 146 Viscera of abdomen and thorax, of man, *309 Vorticella, structure and behavior, 43; *42 Ww Wapiti, *251 Wasps, mimicked by moths, *448 Water, as food nutrient, 295, 298; boatman, *161, bugs, 160; moc- casin, 212; strider, *158; tiger, *160 Whales, 249 Wildcat, 256 Wolf, Thibet, *262 Wolves, 254 Wood-lice, 154 Worms, 143 Y Yellow fever, caused by protozoan parasite, 130 Yellow-hammer, *231