Mammals

“ Mammals.—Any mammal intended for a scientific specimen 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.) ”

“ In such experiments mammals are the animals chiefly used, because in most respects they most nearly resemble man, himself a mammal. Practically all the domestic mammals have been used, horses, cattle, sheep, goats, swine, dogs, cats, rabbits, guinea-pigs, and rats and mice; monkeys are also used. And all have made wonderful contributions to medicine or surgery or both. ”

“ Perhaps no order of mammals presents us with so extraordinary a series of gradations as this*—leading us insensibly from the crown and summit of the animal creation down to creatures, from which there is but a step, as it seems, to the lowest, smallest, and least intelligent of the placental Mammalia. ”

“ The groups have, therefore, been subdivided into five classes, which we will study in succession, only naming each now: viz. mammals, birds, reptiles, fish, and batrachians. Do not alarm yourself at this last name: it is a Greek word, meaning simply frogs.
The mammals are our immediate neighbors. Mammalia are the animals which produce milk. They bring forth their young alive, and give suck to them as soon as they are born. ”

“ Mammals.—Rodents, and all other animals which suckle their young, are included by naturalists in the class Mammalia. These animals agree further in breathing air, in having warm blood, and in being more or less completely covered with hair.
Vertebrates.—Mammals, birds, reptiles, amphibians, and fishes are grouped together to form the sub-kingdom Vertebrata. ”

“ It will be seen that evolution not only introduces a lucid order and arrangement into our thousands of species of living and fossil mammals, but throws an admirable light on the higher animal world of our time. The various orders into which the zoologist puts our mammals are seen to be the branches of a living tree, approaching more and more closely to each other in early Tertiary times, in spite of the imperfectness of the geological record. ”

“ The mammals constitute the highest group of animals, including man, the monkeys and apes, the quadrupeds, the bird-like bats and fish-like seals and whales; in all about 2500 species. They are found everywhere except on a few small South Sea islands. Only a few species, however, have a world-wide distribution. The name Mammalia is derived from the mammary or milk glands with which the females are provided and by the secretion of which the young of this class, born free in all but a few of the lowest forms, are nourished for some time after birth. ”

“ There are only a few points in the classification of organisms upon which naturalists have always agreed. One of these few undisputed points is the privileged position of the class of Mammals at the head of the animal kingdom. ”

“ Moreover, the brain, the olfactory organ, the heart, the lungs, the internal and external sexual organs, the kidneys, and other parts of the body present special peculiarities, both in general and detailed structure, in the mammals; all these, taken collectively, point unequivocally to an early derivation of the mammals from the older groups of the reptiles and amphibia, which must have taken place, at the latest, in the Triassic period—at least twelve million years ago! In all these important characteristics man is a true mammal. ”

“ Next above the Bird family comes the highest form of all—the Mammals. But before we begin our consideration of these high forms, let us take a hasty glance at the "connecting-links" between the Birds and the Mammals. The lowest forms of the Mammals resemble Birds in many ways. ”

“ A glimpse of what mammals are capable of, were it necessary, may be obtained by watching those that are playful, such as lambs and kids, foals and calves, young foxes and others. For these young creatures let themselves go irresponsibly, they are still unstereotyped, they test what they and their fellows can do. ”

“ But to avoid any such criticism, let us take the mammalian subdivision only. The earliest known remains of mammals are those of small marsupials, which are the lowest of the mammalian type; while, conversely, the highest of the mammalian type—Man—is the most recent. ”

“ CLASS I. Mammals.—Warm-blooded animals which have fur or hair, bring forth their young alive, and nurse them. House People are Mammals.
CLASS II. Birds.—Warm-blooded animals which have feathers and lay eggs.
CLASS III. Reptiles.—Cold-blooded animals which have scaly skins, like lizards, snakes, and turtles.
CLASS IV. Batrachians.—Cold-blooded animals which have naked skins, like frogs, toads, and newts.
All the foregoing classes, except a few of the Batrachians, breathe air in lungs, and almost all, except snakes, have legs; none now living can fly, except bats and birds ”

“ Mammals' heads are ' carved out of peat,' and it does not matter out of what substance a mammal is modelled, provided the form is reproduced exactly as it would be were the animal alive, and that it is possible to drive pins in it without bursting or breaking the artificially prepared body, in order to press the skin into the hollows between the muscles. ”

“ The differences between the Mammals and the reptiles and birds are so important and characteristic that we can assume with complete confidence this division of the vertebrate stem at the commencement of the development of the Amniotes. ”

“ The vast assemblage of placental mammals, which range over all the continents, are divided into numerous orders, most of which appear to be natural groups of truly related forms, while some are but doubtfully so and others again are clearly unnatural and arbitrary. ”

“ Birds having long-pointed wings, without scales on metatarsus. Examples: swift, humming bird, and goatsucker.
Mammals.—Dogs and cats, sheep and pigs, horses and cows, all of our domestic animals (and man himself) have characters of structure which cause them to be classed as mammals. They, like some other vertebrates, have lungs and warm blood. They also have a hairy covering and bear young developed to a form similar to their own, [28] and nurse them with milk secreted by glands known as the mammary glands ”

“ To discuss in any intelligible manner the history of mammals, it will be necessary to go much farther than the above table in the subdivision of that part of geological time in which mammalian evolution ran its course. As mammals represent the highest stage of development yet attained in the animal world, it is only the latter part of the earth’s history which is concerned with them ”

“ Mammals [3] are divisible into one great group, which comprises the immense majority of kinds termed, from their mode of reproduction, placental Mammals, and into another very much smaller group comprising the pouched-beasts or marsupials (which are the kangaroos, bandicoots, phalangers, &c., of Australia) , and the true opossums of America, called implacental Mammals. ”

“ The conviction that a large number of animals—at least the higher mammals—are not less endowed than man with a thinking soul and consciousness prevails in modern zoology, exact physiology, and the monistic psychology. The immense progress we have made in the various branches of biology has contributed to bring about a recognition of this important truth. We confine ourselves for the present to the higher vertebrates, and especially the mammals. ”

“ In the great majority of mammals the body [2] is clothed with hair; a character found in no other animals. In a few mammals the skin is naked, and in still fewer there is a partial covering of scales. The list of characters common to all mammals, which distinguish them from other animals, might be indefinitely extended, for it includes all the organs and tissues of the body, the skeletal, muscular, digestive, nervous, circulatory, and reproductive systems, but the two or three more obvious or significant features above selected will suffice for the purposes of definition. ”

“ 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 developed and affectionate care of the young shown by most mammals, 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. ”

“ Finding among mammals some that, in search of prey or shelter, have taken to the water in various degrees, we shall cease to be perplexed on discovering the mammalian structure hidden under a fish-like form, as it is in the Cetacea. ”

“ In attempting to frame a definition of the term Mammal, it is impossible to avoid technicalities altogether, for it is the complete unity of plan and structure which justifies the inclusion of all the many forms that differ so widely in habits and appearance. Mammals are air-breathing vertebrates, which are warm-blooded and have a 4-chambered heart ”

“ Mammals furnish a crowning instance of a trend of evolution which expresses itself at many levels--the tendency to bring forth the young at a well-advanced stage and to an increase of parental care associated with a decrease in the number of offspring. ”

“ In the forests and following the grass over the Eocene plains there appeared for the first time a variety and abundance of mammals. Before we proceed to any description of these mammals, it may be well to note in general terms what a mammal is. ”

“ Among the mammals thus far obtained are specimens of twenty species that represent significant extensions of known range, are of especial taxonomic or zoogeographic interest, or that complement published information, and it is these records that are reported herein. ”

“ The next highest form among the mammals are known as the placentals, or those which bring forth mature young. In this class are found the ant-eaters, sloth, manatee, the whale and porpoise, the horse, cow, sheep, and other hoofed animals; the elephant, seal, the dog, wolf, lion, tiger, and all flesh eating animals; the hares, rats, mice, and ail other gnawing animals; the bats, moles, and other insect-feeders; then come the great family of apes, from the small monkeys up to the orang-outang, chimpanzee, and other forms nearly approaching man. ”

“ And if we look back at the peculiarities which distinguish placental from implacental mammals, the mammalia generally from birds, and birds from reptiles, we shall see that in every case exactly similar apparent disadvantages have been mainly instrumental in producing the higher faculties of each successive vertebrate development. ”

“ THE Carnivorous animals form the largest and most powerful family of Mammals that live on the land; and in this family are also included many water Mammals. Although this extensive family contains animals that are very different in size and form, yet they are all alike in their flesh-eating habits, in possessing strong sharp claws, and three kinds of teeth, the incisors, molars and canines; the latter being sharp and powerful fangs used for seizing and holding their struggling prey. ”

“ As some of these forms advance, we begin to descry in them the features, remote and shadowy at first, of the horse, the deer, the elephant, the whale, the tiger, and our other familiar mammals. In some instances we can trace the evolution with a wonderful fullness, considering the remoteness of the period and the conditions of preservation. Then, one by one, the abortive, the inelastic, the ill-fitted types are destroyed by changing conditions or powerful carnivores, and the field is left to the mammals which filled it when man in turn began his destructive career. ”

“ The differences which separate the mammals, birds, reptiles, and fishes from each other, though vast, yet seem of the same nature as those which distinguish a mouse from an elephant or a swallow from a goose. ”

“ The most valuable results which may be gained from a study of these fossil mammals are the answers which they afford to the great questions of relationship, classification and genetic descent, and the light which they throw upon the [49] processes of evolution and the course of geographical arrangement. The bones and teeth afford admirable means of tracing the gradual steps of modification by which the modern mammals have arisen from very different ancestors and of following their wanderings from region to region and continent to continent. ”

“ Different mammals have been specialized in structure for amazingly varied modes of life, on land, under the ground, in trees, in the air, or in rivers or the sea. Of the terrestrial animals some have been modified for fleetness, like the horse and the antelope; others for strength, like the elephant; others again, like the lion and the tiger, to prey upon their weaker relatives. ”

“ All the mammals, from the lowest monotremes and marsupials to the ape and man, have a large number of striking characteristics in common, and these distinguish them from all other vertebrates: the hair and glands of the skin, the feeding of the young with the mother's milk, the peculiar formation of the lower jaw and the ear-bones connected therewith, and other features in the structure of the skull ”

“ The classification of the mammals approaches more nearly the ultimate truth than does that of any other group of organisms, because we know more about the extinct forms than we do of any other class, and also because we know more about the living forms than we do about any other living animals. ”

“ Mammals differ from fishes and batrachians and agree with reptiles and birds in never having external gills; they differ from reptiles and agree with birds in being warm-blooded and in having a heart with two distinct ventricles and a complete double circulation; finally, they differ from both reptiles and birds in having the skin more or less clothed with hair, the lungs freely suspended in a thoracic cavity separated from the abdominal by a muscular partition, the diaphragm, and in the possession by the females of mammary glands. ”