Mammalia

“ At present man exercises so enormous an effect, both directly and indirectly, that the future history of the Mammalia is probably foreshadowed by the instances of the White Rhinoceros and the Quagga. On the other hand, the economic usefulness of the Mammalia is greater than that of any other animals ”

“ 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. ”

“ 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. ”

“ 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. ”

“ 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. ”

“ They have all the peculiar attributes of the "Mammalia," such as suckling their young, being born alive, having four extremities, warm blood, respiration by lungs, and a heart with two auricles and two ventricles.
A general description of the anatomy and some of the functions of Man will be given hereafter, and will apply equally to all the Mammalia; always bearing in mind that the difference in structure of every animal, although making it inferior to Man, does not do away with any of the essential qualities, which constitute it one of the members of the highest group ”

“ 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." ”

“ 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. ”

“ 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. ”

“ The animals that we considered in the last chapter, though showing certain unmistakable likenesses to the mammals, are nevertheless unquestionably not mammals but reptiles. In the Triassic strata, however, we first meet with the remains of undoubted mammals. The Mammalia first appeared upon the earth in a tentative and hesitating way: they had not cast off many of the characters of their supposed reptilian forefathers; they shrank from observation and destruction by their small size, and apparently, so far at any rate as their teeth afford a clue, by an omnivorous diet. ”

“ Advance of the mammalia during the tertiary. During the several millions of years comprised in Tertiary time the mammals evolved from the lowly, simple types which tenanted the earth at the beginning of the period, into the many kinds of highly specialized mammals of the Pleistocene and the present, each with the various structures of the body adapted to its own peculiar mode of life. The swift feet of the horse, the horns of cattle and the antlers of the deer, the lion’s claws and teeth, the long incisors of the beaver, the proboscis of the elephant, were all developed in Tertiary times. ”

“ The visitor has now reached the Southern Extremity of the Eastern Zoological Gallery, and brought his first visit to a conclusion. He may well pause, however, before dismissing from his mind the objects which have engaged his attention.
First, then, he examined the varieties of MAMMALIA. The mammalia, of which man himself is the highest type, are the leading class of the great order of vertebrate, or back-boned animals, and fishes are the lowest, the intermediate classes being birds and reptiles. ”

“ This Order comprises Man, Monkeys, and Lemurs, aud therefore includes the most highly organized Mammalia. At the same time the Lemurs and some of the Monkeys are of comparatively low grade, and much inferior, at all events in development of brain, to Mammalia belonging to other orders. ”

“ The mammalia, for example, were long thought to have first appeared in Tertiary times, where they are represented in some of the earlier deposits by all the great divisions of the class fully developed—carnivora, rodents, insectivora, marsupials, and even the perissodactyle and artiodactyle divisions of the ungulata—as clearly defined as at the present day. ”

“ As, however, Professor Kingsley justly says that "no single bone occupies a more important position in the discussion of the origin of the Mammalia than does the quadrate," and with equal justice adds that "upon the answer given as to its fate in this group depends, in large measure, the broader problem of the phylogeny of the Mammalia," it becomes, or indeed has long been, a matter which cannot be ignored in any work dealing with the mammals. ”

“ There is no longer a doubt but that the first birds were simply modified reptiles. The first bird had a long jointed tail, and a bill well supplied with formidable teeth.18 It was during this period that the first representative of the class Mammalia, to which man belongs, appears.19 It is in the rocks of this era that we meet with remains of marsupials, the order to which opossums belong. This is the lowest of the Mammalian class. To the class Mammalia belong the most highly organized animals. They have been the ruling animals since the close of Mesozoic time. ”

“ The mammals differ from the reptiles and birds in many important characters, as in the manner in which the skull and backbone are joined together (two condyles instead of one) , in the simple structure of the lower jaw, it being composed of only one piece on each side in the Mammalia, whereas in the reptiles and birds it is made up of several. The skin of the mammals is covered more or less with hairs, never with feathers, as in birds. They bring their young into the world living, and nourish them for a longer or shorter time with milk. ”

“ The classes of the vertebrata, according to both the authors above quoted, are: 1. Mammalia. 2. Aves. 3. Reptilia. 4. Amphibia. 5. Pisces, in which order they will be taken here.
The sub-classes and orders of mammalia are as follows:
MAMMALIA.
The above series of orders is arranged according to Professor Flower's Osteology of Mammalia, and they will follow in this succession throughout my work. ”

“ 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. ”

“ With respect to existing Mammalia, most naturalists of the present day seem to be unanimous as to the convenience at least of founding a generic or subgeneric distinction on well-marked modifications in the form and structure of the teeth, although they may correspond in number and kind, in proof of which it needs only to peruse the pages of a Systema Mammalium which relate to the distribution of the Rodent Order. ”

“ If we suppose the mammalia to be more sensitive than are the inferior classes of the vertebrata, to every fluctuation in the surrounding conditions, whether of the animate or inanimate world, it would follow that they would oftener be called upon to adapt themselves, by variation, to new conditions, or if unable to do so, to give place to other types. ”

“ We may therefore say that neither form nor complication of structure distinguishes classes, but simply the mode of execution of a plan. In Vertebrates, for instance, how do we distinguish the class of Mammalia from the other classes of the type? By the peculiar development of the brain, by their breathing through lungs, by their double circulation, by their bringing forth living young and nursing them with milk. In this class the beasts of prey form a distinct order, superior to the Whales or the herbivorous animals, on account of the higher complication of their structure ”

“ And amongst the Mammalia, beginning with small Rodents, which quickly reach maturity, produce large litters, and several litters in the year; advancing step by step to the higher mammals, some of which are long in attaining the reproductive age, others of which produce but one litter in a year, others but one young one at a time, others who unite these peculiarities; and ending with the elephant and man, the least prolific of all, we find that throughout this class, as throughout the rest, ability to multiply decreases as ability to maintain individual life increases. ”

“ Lines of Migration of the Mammalia.—The whole series of phenomena presented by the distribution of the Mammalia, looked at broadly, are in harmony with the view that the great continents and oceans of our own epoch have been in existence, with comparatively small changes, during all Tertiary times. ”

“ The structural differences will not bear any such interpretation, and have not the same value as those distinguishing the orders of mammalia; as, for instance, between carnivora and bats, or the cloven-footed animals and the rodents, or rodents and edentates. ”

“ The birth-place and migrations of some mammalian families and genera.—We have now to consider a few of those cases in which the evidence already at our command, is sufficiently definite and complete, to enable us to pronounce with some confidence as to the last movements of several important groups of mammalia. ”

“ 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. ”

“ Teeth and toes are the basis for subdividing the class mammalia into orders. Although the breathing, the circulation, and the internal organs and processes are similar in all mammals, the external organs vary greatly because of the varying environments of different species. The internal structure enables us to place animals together which are essentially alike; e.g. the whale and man are both mammals, since they resemble in breathing, circulation, and multiplication of young. The external organs guide us in separating the class into orders. ”

“ Mammalia, fishes, and reptiles, as well as mollusca, present similar phenomena; and the more the habits of animals are investigated, the more numerous are found to be the cases in which their colours tend to conceal them, either from their enemies or from the creatures they prey upon. ”

“ The number of mammals which devour insects seem sometimes overlooked, and this fact can be easily realized by looking through the pages of any good treatise on the Mammalia, and tabulating the nature of the food used by the different animals. ”

“ The growth of animal life is equally instructive. First invertebrate life, then the lowest forms of vertebrate life. The fishes are followed by amphibians—then reptiles, then birds. The first mammal to appear was the lowest organized of all—the marsupials. And we have seen the sudden increase of mammalian life in Tertiary times. We notice, in all the divisions of life, a beginning, a culmination, and a decline. ”

“ But the organisation, quite special, of the first of the Mammalia will certainly be a matter of astonishment to the reader, and must satisfy him that Nature proceeded in the creation of animals by successive steps, by transitions which, in an almost imperceptible manner, connect the beings of one age with others more complicated in their organisation. The first Mammals which appeared upon the earth, for example, did not enjoy all the organic attributes belonging to the more recent creations of the class. ”

“ The fact that all the Mammalia are provided with glands which in the female supply milk for the nutrition of their young, that they have a hairy coat, that they have a highly developed brain more fully adapted for learning by experience than is the case in other vertebrates, that they have limbs capable of a much more varied and active range of skilled movements, and a host of identical transformations of viscera, muscles, nerves, and vessels prove the common ancestry of mammals from some very primitive cynodont reptile. ”