Mammal

“ As a name for the class Linnæus adopted the term Mammalia, which he formed from the Latin mamma (i.e. teat) to designate those animals which suckle their young; hence the abbreviated form Mammal, which has been naturalized as an English word. “Beast,” as employed in the Bible, and “Quadruped” are not quite the same as mammal, for they do not include the marine forms, such as whales, dolphins, seals, walruses, or the flying bats, and they are habitually used in contradistinction to Man, though Man and all the forms mentioned are unquestionably mammals. ”

“ At a later period the mammal, with its special characteristics, develops out of the amphibian, and we can clearly see, in the successive stages of its later development, a series of steps of progressive transformation which evidently correspond with the differences of different mammalian orders and families. ”

“ 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. ”

“ 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 ”

“ 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. ”

“ 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. ”

“ It is possible to be quite sure that some facts carefully observed about mammals in a biological laboratory apply to similar structures in man, also a mammal. Because of this relationship, the data from medicine and surgery are priceless. ”

“ And as to what they are, fish, mammal, or reptile, or a compound of either two or all three of these, why doubt any possibility when we know that on land are similarly complicated organisms which so lately have perplexed our most able physiologists? ”

“ Now if, as still happens every year, there be discovered in any part of the earth a new species of mammal, a new species of marsupial, or a new species of deer, or a new species of ape, every zoologist knows with certainty at once, without having examined its inner structure, that this species must possess a quadruple heart, a brain and spinal marrow, like all other mammals. ”

“ Similarly the young mammal is developed within the body of the maternal organism to a point where it is able to perform the primitive functions of life. For weeks, months or even years, according to the class of the animal, it must be supported and protected by its parents. ”

“ The essential agreement in the whole bodily form and inner structure is still visible in the embryo of man and the other mammals at the late stage of development at which the mammal-body can be recognised as such. ”

“ The bony structure of man classes him as a vertebrate; the mode of suckling his young classes him as a mammal; his blood, his muscles, and his nerves, the structure of his heart with its veins and arteries, his lungs and his whole respiratory and circulatory systems, all closely correspond to those of other mammals, and are often almost identical with them. ”

“ 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. ”

“ Is the human species a unique kind of vertebrate, or does it find a place in one of these classes? The occurrence of hair, of a four-chambered heart which propels warm blood, of mammary glands, and of other systematic characters marks this species as a kind of mammal and not as a vertebrate in a section by itself. ”

“ The young of the mammal is fed by the mother through all the embryological stages, this being most fully performed in the highest mammals, so that their young commence an independent life at a stage to reach which the young of lower animals consume a considerable portion of their vital energy. ”

“ The embryonic development of man and the other mammals demonstrates their remote relationship and their gradual evolution. The dog, the sheep, the ox, the horse, the ape and man and every other mammal begins life as a single cell. ”

“ We cannot, however, in this book pretend to go into general matters of this kind, which would take us too far from the subject at hand; but anyone who would pursue this further can consult Professor Huxley’s ‘Elementary Physiology,’ or any other elementary text-book upon physiology. When a mammal—a human being, for example—breathes certain muscles are called into play. ”

“ GENERAL CLASSIFICATION OF THE ANIMAL KINGDOM
VERTEBRATA.
CLASS MAMMALIA.
The mammalia include not only man, the head of creation, but, generally, those animals which have the most numerous and perfect faculties, the most delicate perceptions, the most varied powers, and the highest degrees of intelligence. All the species have a double heart; red, warm blood; and a nervous system more fully developed than that of any other animals. This class is divided into nine orders, under each of which we shall notice some of the more remarkable species. ”

“ This is particularly true of the birds and mammals. We find them spreading so early in the Tertiary that we must put back the beginning of the expansion to the Cretaceous. As yet, however, the only mammal remains we find are such jaws and teeth of primitive mammals as we have already described. ”

“ 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 ”

“ One of those lowly gelatinous forms, so transparent and colourless as to be with difficulty distinguished from the water it floats in, is not more like its medium in chemical, mechanical, optical, thermal, and other properties, than it is in the passivity with which it submits to all the influences and actions brought to bear upon it; while the mammal does not more widely differ from inanimate things in these properties, than it does in the activity with which it meets surrounding changes by compensating changes in itself. ”

“ 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. ”

“ 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. ”

“ There is, of course, the essential resemblance that is shown between all animals that have definite organs which are set apart for respiration: the feathery gills of the marine worms, the closely set branchiæ of the fish, the lungs of the bird and of the mammal, are all constructed upon one plan, so far as essentials are concerned. ”

“ 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 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. ”

“ 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 ”

“ Thus, then, we see that in the mammalia, instead of man standing alone, sharply contrasted to the rest of the class, he merely occupies one extremity of a series toward the other end of which stand our much-talked-of friends the lamb and the foal, while the carnivorous animals and the apes occupy intermediate positions. ”

“ 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 ”

“ In reality, notwithstanding the prodigious speculations of learned anatomists, no truly good arrangement of the Mammalia has yet been arrived at; the deficiency arising from the fact that, as yet, no true zoologist has had the opportunity of a sufficiently extended observation of the natural habits of animals. ”

“ 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. ”

“ If we follow more in detail the appearance of the single organisms, some remarkable modifications show themselves in the course of their appearance and growth. We have heretofore mentioned the possibility of the appearance of the mammalia before the bird. ”

“ 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. ”

“ From these pregnant facts of comparative anatomy and ontogeny it follows absolutely that the whole of the Mammals belong to a single natural stem, which branched off at an early date from the reptile-root. It follows further with the same absolute certainty that the human race is also a branch of this stem. Man shares all the characteristics I have described with all the Mammals, and differs in them from all other animals. ”

“ 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. ”

“ We have now arrived at the highest rank in the scale of animal life—the four-footed, hair-clad, milk-nursed denizens of our woods and fields—the subclass Mammalia, mammals.
These are the "animals" of popular speech, but accuracy requires a more distinctive expression, for every living thing not a plant is an "animal." ”

“ If the hypothesis of evolution is true, what ought to happen when we investigate the history of this animal? We know that the mammalian type, as a whole, that mammalian animals are characterized by the possession of a perfectly distinct radius and ulna-two separate and distinct movable bones, We know, further, that mammals in general possess five toes, often unequal, but still as completely developed as the five digits of my hand. ”

“ 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. ”

“ We can follow the evolution of our mammals of this branch most easily by studying the modification of the feet and limbs. In a running attitude—the experiment may be tried—the weight of the body is shifted from the flat sole of the foot, and thrown upon the toes, especially the central toes. This indicates the line of development of the Ungulates (hoofed animals) in the struggle of the Tertiary Era. ”