EASY LESSONS IN ANIMAL BIOLOGY.
CHAPTER III.
SUB-KINGDOM IX.—VERTEBRATA.
Though reptiles are generally regarded with aversion, there is much of interest in their natural history, and even they may serve some useful purpose. There are four genera, and about fifteen hundred species. The respiratory organs are the same in all, and are such as belong to air-breathing animals. With few exceptions they are carnivorous; generally sluggish in their habits, and their sensations dull. Nearly all the winter they are in a state of lethargy.
FLYING TOAD.
Amphibia.—There are several species of cold blooded amphibious vertebrates which are properly neither fishes nor reptiles, but, having some things in common with both, should be mentioned here. Their respiration is most peculiar, as they have only gills when young, and, when adult, lungs. In their immature state they are fish-like, but develop no fins; and their limbs, when they at length have them, show the same articulations as those of higher animals. These amphibia, in the progress of their development undergo a series of remarkable metamorphoses. They begin life as water-breathing larvæ. In some of the lower orders the gills remain through life; others, when mature, have lungs only. Aquatic Newts, two-legged Mud-Eels, Toads, and Salamanders, are their representatives. The Batrachia[1] include the frog, a well known, tailless amphibian. Its metamorphose is peculiar. The ova are deposited in a jelly-like mass at the bottom of the water, and, if the temperature is suitable, develop rapidly. In a few days very interesting microscopic observations are possible. The embryo presents four distinct appearances before leaving the egg, and five more before assuming its complete organization. For a time it seems a soft-skinned, scaleless fish, breathing only as fishes do, and having a long, flexible tail, used as an oar. Then it develops the palmated hind legs, as assistants in its locomotion, the caudal process diminishes, the forelegs protrude, true lungs are developed, the wriggling tadpole is a frog; abjures kinship with its still aquatic relatives, hops to the land, and enters on pursuits befitting its new mode of life. The common frog is well known, and we present one of a different family. It is distinguished by having the ends of its toes dilated into discs, or suckers, by which it sticks to the smooth bark, and is capable of its arboreal life. It is often called the “flying frog” and the “tree frog.” The webbed feet are large, and when spread out serve to bear up the body, as would paper kites of the same size. But the animal does not fly. It is active, and leaps from branch to branch expertly, and, when it wants to descend, by spreading those fan-like feet, it comes down with less violence. Tree toads are noisy little creatures, and seem to be ventriloquists, as their voices do not indicate their true position. This deception, and their color, make their capture more difficult.
CLASS II.—REPTILIA.
Order I.—Ophidia,[2] or serpents, are oviparous, air-breathing vertebrates, having round, tapering bodies. They crawl or glide on their ventral surface. The serpent’s body is very flexible. Its numerous vertebræ, concave in front, and hemispherically convex behind, are so jointed as to allow a free horizontal motion. Its progress is usually by lateral undulations, made practicable by the great number of the vertebræ, attached flexible ribs, and muscles along the sides, specially arranged for prompt action on the spinal column. The bones of the head are loosely jointed, and movable, making the mouth very dilatable. The sharp teeth are hooked backward, so that whatever is seized is likely to go down the capacious throat. The entire skeleton and skin are so elastic that objects much larger than the serpent, in its normal condition, can be swallowed whole. Though without limbs, they perform with dexterity a great variety of movements; creep, climb, swim, raise the body almost erect, and spring from the ground. There are two classes, the poisonous and the harmless. Of the former the Cobra, Copperhead, Viper, and Rattlesnake are representatives. They have extensile fangs, and, along the side of the upper jaw, a large gland, which secrets a poisonous liquid that is injected through the hollow or grooved fangs into the wounds they inflict. Harmless snakes have much the same structure, but nothing of this special arrangement.
Order II.—Lacertilia[3] or lizards, are snakes with short legs, and usually much quicker in their movements than most other reptiles. Most species are harmless, though a few are said to be venomous, and, because of them, all are dreaded. They differ much in appearance, some being really beautiful, and others about as hideous as reptiles can be. There are an immense number and variety of lizards, having some distinctive characteristics. Several extinct species, as the Iguanadon,[4] Megalosaurus,[5] Plesiosaurus,[6] and Ichthyosaurus,[7] are known only by their gigantic fossils, casts of which may be seen in many of our college museums.
Order III.—Chelonia.[8] This name is derived from the Greek word for tortoise. The class includes all the varieties of tortoises or turtles. Tortoise means crooked, or twisted, and refers to the awkward manner in which the limbs are twisted about when in motion. There are two skeletons, the one external, including the viscera and the whole muscular system, which is internally attached to it. The upper plate of this covering, called the carapace, is more or less convex, and made up of strong elastic plates. The lower, or plastron, is flat and smooth, being apparently an extension of the sternum or breast bone. These plates are joined together at their lateral edges, leaving anterior and posterior openings through which the head and limbs are extended. When at rest, these are usually under the covering. The head and neck are covered with a rough, corrugated skin, and the horny upper jaw terminates in a strong, hooked beak. They are usually distinguished as marine, fresh water, and land turtles. The former are good swimmers, but their movements on land are slow and awkward, and if turned on their backs they are quite helpless. Some marine turtles are very large, being from four to six feet in diameter, and weighing from 600 to 2,000 pounds. Usually they weigh much less. All are oviparous, the female producing about one hundred and fifty hard-shelled eggs at a time. For this purpose she cautiously comes ashore, and, dextrously using her hind flippers, excavates a hole in the sand, from a foot to eighteen inches in depth, lays her eggs, and, having carefully covered, leaves them to be hatched by the heat of the sun. The green, edible turtle is very valuable, and furnishes much wholesome and delicious food. The “hawks-bill” is seldom used for food, but supplies the greater part of the well known “tortoise shell” of commerce. There are many other species, both marine and fresh-water, whose flesh or shells are of considerable value. Soft Tortoises, Snappers, Mud-Turtles, and Terrapins, all have some peculiar characteristic.
Order IV.—Loricata.[9] This corselet or armor-covered family includes Crocodiles and their allied species. Their upper parts are covered with a corselet of bony plates set in the tough, leathery skin. The jaws are long, and have many strong, conical teeth, fixed in sockets. The lower jaw extends back of the cranium, and the upper is hinged and movable. Crocodiles belong in tropical climates, are sluggish animals, and live a long time if not destroyed by violence. Their legs are short but powerful, and when on land they manage to wriggle, or drag, their immense bodies along with considerable speed. They are found in India, and in all the large rivers of Africa. The Gavial of the Ganges, the Crocodile, and the Mississippi Alligator are closely related, though there are some structural differences. Of whatever variety, whether of the Old World or of the New, they are more numerous than desirable, not being noted for either their beauty or usefulness.
Class III.—Aves.[10] Birds furnish a delightful study, and their leading characteristics are easily stated. Widely as they differ, they all have a common type of structure, and are essentially alike in those particulars that distinguish them from other orders in the animal kingdom. They are all warm blooded, feathered, biped vertebrates, mostly with wings fitted for flight, and with either webbed feet for swimming, or claws for seizing, scratching, and perching.
ANATOMY OF A HEN.
Ex.—A, cranium; B, cervical vertebræ; G, furcula, or merry thought; J, sternum, or breast bone; H, cloaca, surrounded by the pelvic bones; E, caudal vertebræ, terminating in plowshare bone; D, lumbar vertebræ, or rump; C, F, dorsal vertebræ, to which the ribs are attached.
There are several points of interest in the anatomy of a bird that may be used to bring out general characteristics: (1) The long neck, with vertebræ so adjusted as to allow great freedom of movement, makes the head a convenient prehensile organ. (2) The skeleton is remarkably light. It has fewer bones than other vertebrates; the thin skull bones, the dorsal vertebræ, and bones of the feet being anchylosed.[11] They are also harder, of lighter material, and filled with air, thus having the greatest possible strength with the least weight. (3) To make respiration sufficient during rapid flight, an abundant supply of air not only inflates the lungs as in other animals, but fills little membranous sacs, or cells, distributed through the body, and extends even into the wing feathers. (4) The digestive apparatus differs materially from that of either fishes, reptiles, or mammals. The æsophagus[12] before reaching the sternum is dilated into a large sack, or crop, and serves as a first stomach, in which the food is softened, and prepared for other digestive organs. Below this is another slight enlargement, the walls of which are thicker, and secrete gastric juice. Still further down, the canal is enlarged into a third stomach, the muscular gizzard, in which the process is completed. (5) There are no teeth set in the bone sockets, as their weight would be inconvenient, but the mandibles are sheathed in a horny case, which has sharp edges, and terminates in the beak, or bill.
NESTS OF BIRDS.
Both genera and species are very numerous, but any two birds that can be selected differ less in their anatomy than some reptiles of the same order differ. The leading orders only of this class have been selected. Raptores[13] (robbers). This is a mild term when used to indicate the ferocity of most birds of prey which not only plunder but destroy. They are almost constantly committing murderous assaults on their weaker neighbors. This is their nature, and accords with their physical structure. The strong hooked bill, powerful legs, feet armed with sharp claws to seize and hold their victims, while the murderous beak is tearing off bits of flesh, are some of their chief characteristics. These murderers have representatives in nearly all countries, but as civilization advances they become less numerous.
They are usually divided into three great families: Falcons, Vultures, and Owls. The first includes all kinds of Hawks and Eagles. True falcons reveal a predatory character, not only by their general structure as described, but have a special arrangement for keeping their formidable weapons in order. The continual sharpness of their claws is necessary, and to maintain it they must be kept from coming in contact with hard substances. To make this practicable, though they are not retractile, like a cat’s claws, there not being sufficient integuments to cover them, the bird has power to elevate their points when stepping or perching on anything likely to dull them. Being very powerful and rapid flyers, falcons were in former times tamed, and trained for catching other birds and small game. Falconry, in the middle ages, was one of the principal diversions of kings and noblemen, lords and ladies, and in later times the same sport was practiced in England under the name of “hawking.” The training of the birds was a profession, and there were teachers who became proficient in it. The Eagle, king of birds, belongs to this class; he is, perhaps, inferior in activity and enterprise, but is more powerful, and his supremacy is undisputed. The Bald Eagle adorns our American flag, and is a fit emblem of national sovereignty, though there was, it is confessed, some ground for Franklin’s protest, “The bird has a bad moral character, and does not get his living honestly.” The Gypætos, or Vulture Eagle, is the largest bird of Europe, and often a terror to the peasants near the Pyrenees and Swiss Alps. Its great strength, bold, predatory habits, and impetuosity in pouncing on animals exceeding itself in size, make it more formidable than most eagles are.
THE FLAMINGO.
Vultures are cowardly, disgusting creatures, and feed mostly on putrid flesh, yet they are useful scavengers in hot climates, devouring much animal matter that would otherwise cause pestilence and death.
Owls are nocturnal birds of prey, and though seldom abroad except in the darkness, or twilight, being often captured and confined, they are pretty well known.
Insessores[14] (perching birds). This term is adopted as vaguely descriptive of many species, of which no particular mention can be made. They include our common singing birds and skillful nest builders. Some of these build low, among the grass, others on branches of trees. Some are solitary, and during the nesting season isolate themselves. Others, as the “sociable weavers,” unite in building them cities, in which each pair claims a private residence.
Cursores[15] (runners). Birds of this class run rather than fly, have no keel on the breast bone, no well developed wings, and their feathers are loosely put together, without the connecting barbs that strengthen the wing feathers of others. But they have strong legs, and feet with nails rather than claws. The Ostrich is most distinguished for its size, strength, speed, and peculiar feathers. The Emeu and Apteryx belong to the same class, the latter being tailless.
Grallatores[16] (waders). These aquatic birds are distinguished by their very long, bare legs, also necks and bills of like proportions. Herons, Storks, and Flamingoes are representatives.
The latter is a peculiar bird, common in some portions of America, Southern Europe, Asia, and Africa. When walking erect it is about five feet high, the body of a light color, and the wings red. When a number go in single file, as such birds do, they appear like a company of British soldiers in uniform. As their legs are quite too long for convenience when incubating, they construct, of grass, rushes, and mud, a little cone of sufficient height, make their nest on the top, and sit astride, the long legs hanging down the sides. This also protects the eggs and young from moisture in wet weather.
THE ALBATROSS.
Natatores[17] (swimmers). Aquatic birds being keel breasted, with short legs, webbed feet, and thin, light, warm covering, delight in swimming. Some of these have also good flying qualities, as Wild Geese, Swans, Sea-Gulls, and Petrels, which spend much time in skimming over the water, either on or above the surface.
This family includes the wandering Albatross, which is among the largest of the sea birds, having from ten to fifteen feet expanse of the wings, and weighing from twenty to thirty pounds; yet it sustains itself in the air for many hours together without any apparent difficulty. It is often met far out at sea, and sailors have many superstitions respecting it. Like all petrels and sea-gulls, the albatross makes its nest on crags and cliffs along the coast, choosing places that seem inaccessible. To gather the eggs of seafowls, which are esteemed a delicacy, and to capture the birds themselves for the feathers, is one of the most perilous employments. The adventurous fowlers are swung over precipices from five hundred to a thousand feet above the sea, sustained simply by a rope, that, by breaking, or slipping from the hands that hold it, must hurl them to certain destruction.
Class IV.—Mammalia (milk givers). Though there are some very low species in this order, it reaches upward and includes the highest forms of animal organization, all of what ever degree, that have the mammary glands, and secrete milk for the nourishment of their young. There are more than two thousand species of these in North America alone. They have several distinguishing characteristics. The heart is four chambered, having two auricles and two ventricles. They are warm blooded, the blood having two kinds of corpuscles, the red predominating, and being globular. The impure blood from the body pours into the right auricle, passes to the right ventricle, and thence to the lungs. In the lungs, which are spongy and full of air cells, it is supplied with oxygen from the air freely circulating through them. Being thus changed to purer arterial blood, it passes back through the left auricle to the left ventricle, and, by a muscular action, is forced through the great aorta and its innumerable branches to every part of the body. Mammals always breathe by lungs enclosed in a membranous sack called the pleura. They are viviparous, or produce their young alive, though some when in a very immature, helpless state. They are for convenience subdivided:
Order I. Monotremata.[18] These animals, the lowest of mammals, have long, flattened beaks, webbed feet, and other bird-like characteristics. But they are of little importance, few in number, and not widely distributed, being confined mostly to Australia and Tasmania.
Belonging to this class is the Water-Mole, with a broad, duck-like, horny bill. It lives on worms and vegetables, and burrows in the banks of streams, having the opening to its quarters under the surface of the water.
Order II. Marsupial, or pouched animals. The young are brought forth in a very premature state, but are immediately placed in a marsupium or pouch under the abdomen, where, attached to the little teats, they receive their nourishment. They are thus protected and carried by the mother as long as such care is necessary. The opossum, the only native marsupial of the United States, is about twenty inches long, exclusive of the peculiar rat-like, prehensile tail, by which the animal often suspends itself from the branches of trees. When in danger, it feigns death as a way of escape—and can survive injuries that would be fatal to most animals. They were once very numerous in this country, and though destructive to fruit and poultry, are of some value. Their flesh is used by some, and the skins are in demand, the hair or coarse fur being wrought into felt.
Order III. Edentata[19] (toothless). Animals without incisors, and having separate clawed toes, are included under this order. The chief representatives are the Armadillos, Sloths and Ant-eaters.
Armadillos[20] are remarkable animals, with a covering of horny plates, not unlike a tortoise shell, but arranged in sections in a way that allows more freedom of motion. Some of the extinct species were of gigantic proportions. A fossil armadillo found near the La Plate was as large as a full grown rhinoceros.
The Sloths are natives of South America. They are covered with long, coarse, gray-and-black hair, resembling the moss of the trees in which they live, for these animals are arboreal, while the other members of the order burrow.
Ant-eaters, of which there are several varieties, are covered with spines like the hedge-hog. Even the long, rough tongue and palate are provided with the sharp little spines with which they spear and hold their prey. Their claws also are fitted for digging into the ant hills, where the food is obtained. They are very inferior mammals, but have their place, and are useful in destroying noxious insects.
The giant ant-eater of South America is much the largest of the genus, and an animal of considerable strength. From its long, bill-like snout it thrusts out its longer tongue, and the frantic ants, disturbed in their quarters, on rushing out stick to it, and are rapidly swept into the mouth. When sleeping, it is coiled up under its immense bushy tail and looks more like a little heap of dried grass than an animal.
THE ANT-EATER.
Order IV.—Sirenia[21] (sea cows), include the Manatee, found between the Amazon and Southern Florida, and the Dugong, of India. They are amphibious milk givers. In appearance and structure they are very unlike most mammals. Their forelimbs resemble fins, having fingers or toes. The hind legs are wanting, and the tail like that of a fish, but they suckle their young, sometimes supporting them for the purpose with their flippers.
Order V.—Cetacea[22] (Whales). They are much the largest of mammals. They live entirely in the sea, and have in general a fish-like appearance. Their forelimbs are huge paddles, the others being only rudimentary. But they produce their young well developed, and nourish them with an abundance of rich, creamy milk. The amount of blood in a large whale must be immense, the great artery being a foot in diameter, every pulsation of the heart forces many gallons along the channels prepared for it. A single whale, captured in 1884 by the crew of a New London vessel, produced whalebone and oil worth $15,720, beside other products of considerable value.
Order VI.—Insectivora (insect eating). An order of small animals, having well developed teeth, the molars remarkable for their sharp cusps; and five-toed feet furnished with claws. The Mole, Hedge-hog and Shrew are examples.
VARIETIES OF BATS.
Order VII.—Cheiroptera[23] (wing handed). Bats are not generally favorites, and are by many regarded with aversion. Their strange and rather uncomely forms are seen on wing only in the dim twilight, as they spend the day mostly in deserted buildings and gloomy caverns. In eastern countries, where such receptacles of the dead are common, bats are often found in sepulchers or catacombs, and are regarded as fit dwellers with desolation and death. There are many species, with enough variety in their appearance; and the study of their natural history softens prejudice and reveals much of interest in their structure and habits.
Order VIII.—Rodentia[24] (gnawing animals). Animals of this order have two large, chisel-like incisors in each jaw, and, separated from them by a wide space, are the molar teeth. The incisors never cease growing from the roots, but are constantly worn away by nibbling. The lower jaw moves backward and forward. This order includes more than half of the known mammals, and its representatives range from the equator to the poles. Hares, Mice, Rats, Squirrels, and Beavers are among those best known.
Order IX.—Ungulata[25] (hoofed animals). An order of mammals most valuable to man. They are grouped in two divisions, according to the number of toes. The uneven-toed ungulates include the Elephant, Rhinoceros and Horse. The elephant is marked by the prolongation of the nose and upper lip into a trunk or proboscis, which is said to contain over 40,000 muscles. It has no canine teeth, and incisors only in the lower jaw. Elephants are found in Asia and Africa. There are two extinct species, the mastodon and mammoth. The rhinoceros is a native of Africa and India. It is an immense animal, covered by a hairless skin, which lies in folds on the body. The nose bears one or two horns, which grow sometimes three feet in length. The horse includes animals having one toe upon each foot, upon which they walk. The family includes the Ass, Zebra and Quagga.
The even-toed ungulates include all the Ruminates, or cud chewing animals, with the Swine and Hippopotamus. The ruminants are remarkable for their peculiar method of digesting their food. They possess a very peculiar stomach, of four compartments. The food, mixed with saliva, is swallowed and passes into a paunch where it is mingled with water, and then forced into what is called the honey-comb stomach, a sack in which the food is formed into cuds, and by a muscular arrangement is forced back into the mouth to be masticated a second time before passing directly into the third stomach or manyplies, where it is strained, and then driven into the true stomach to be acted upon by the gastric juice and assimilated.
The deer is a fine representative of the ruminant, with solid branching horns. Like all ruminants it has two toes. There is a large class of cud-chewers having hollow horns, which usually are not shed, as are the solid horns. The Buffalo, Ox, Sheep, Goat and Antelope belong to this division.
OX SKELETON.
10, horns; 8, spine; A, cervical, B B, dorsal, C, lumbar, D, sacral, and E E caudal vertebræ; F F, ribs; G, sternum and cartilages; R, ossa innominata; H, scapula; I, humerus; K, radius; L, ulna; N, metacarpal; S, femur; T, patella; U, tibia; V, hock; X, metatarsal; Y, small metatarsal; P, sesamoids; Y, bones of tarsus, nine in number. Figures near Z: 1, infero maxilla; 2, supero maxilla; 3, premaxilla; 4, nasal; 5, lachrymal; 6, frontal. Figures near letter M, bones of the carpus or knee, 1, trapezium; 2, cuniform; 3, lunar; 4, scaphoid; 5, unciform; 6, magnum. Figures near the letter Q, mark the three phalanges, or small bones of the foot.
The Giraffe, an inhabitant of Central Africa, and remarkable for its long neck, is another ruminant. The camel also belongs here. The true camel has two fatty humps upon its back; another species, called the dromedary, has but a single hump. The camel has a peculiar modification of one compartment of the ruminant stomach. The paunch is divided into cells which hold supplies of water.
Order X.—Carnivora (flesh-eaters). The distinguishing characteristics of this order are sharp canine teeth, and one molar on each side in the upper and lower jaw, longer and sharper than the rest; and feet which are provided with toes, generally supplied with claws. According to the modifications of the feet they are divided into Pinnigrades, Plantigrades and Digitigrades. The first have short, webbed feet which they use as paddles for swimming, and are represented by Seals and Walruses. These are amphibious mammals of a high order. They spend much of their time in the water, and both the form and covering of their bodies are adapted to their aquatic mode of life. They swim and dive with the greatest facility. The soft woolly down, close to the skin, is covered with a coat of long, smooth, shining hairs which lie close to the body, offering no resistance to their passage through the water. Their skins and oil are of considerable mercantile importance. The Plantigrades include those animals which in walking place the sole of the foot flat upon the ground. Such are Bears and Raccoons. The Digitigrades are those which walk on the toes, as Weasels, Foxes, Dogs, Cats, Lions and Tigers.
Order XI.—Primates are at the head of the animal kingdom. The distinguishing characteristics of this class are the more erect carriage of the body, a hand better adapted for use, its fingers being furnished with nails, and a thigh free from the body. The order includes the Lemurs, Monkeys, Apes and Man. The lowest division of the primates, the lemurs, are small animals whose bodies are covered with hair. They have a fox-like face, a pointed nose, large ears, and a long tail, and they walk on all fours. The monkeys have long prehensile tails, and though their hands can be used for grasping, the thumbs are not opposable. A distinguishing mark is the number of teeth; they have thirty-six instead of thirty-two, as the apes and man. Among the monkeys are the Baboon, the Howling Monkeys, the Mandril, and the Sleepers of Africa and Asia.
The apes are more erect than the monkeys, have no tail, and have longer arms. The division includes the Orang-Outang of Borneo and Sumatra, the Chimpanzee, of Africa, and the Gorilla of Africa and Asia.
Man commands the highest physical development among the primates. In him the partially erect position of the monkey and ape becomes complete. His limbs are more nearly equal in length and more perfectly developed than those of other primates, the skull is larger, the forehead more rounded, and the brain nearly twice the size of that of the gorilla, the dentition is more perfect, the teeth being regular and rarely protruding. The great distinction between man and the lower primates is that of mind. He alone, of all animals, possesses the power of articulate speech, of forming abstract ideas, and of reasoning.
End of Required Reading for the Year 1884-85.