From the French of ERNEST MENAULT.

This is a class of animals which, by their organization and intelligence, approach nearest to man. The mammalia have a bony skeleton, the center of which is the spine, to which the other organs are attached, and whence they all radiate. They possess, also, a brain, in which the hemispheres are well developed; a heart with two ventricles and two auricles; lungs for inhaling air to oxydize the blood and stimulate all the organs, the brain especially. The thoracic cavity contains the lungs and the heart, which are always separated from the abdominal cavity by a complete diaphragm.

In this class the organs of sense acquire great perfection, even in their accessory parts. For instance, the greater number of each species have distinct eyelids, an external ear, and other peculiarities which are not found amongst the oviparous animals. The mouth is furnished with fleshy lips (except the monotrematous animals[K]), and the body is habitually protected with a specially adapted covering.

All the mammalia have five senses, but in different degrees. Thus, one species, such as the chamois and wild goats, that live upon the mountains, have long sight, and can see better far away than near. On the contrary, the heavy races which inhabit the valleys, such as the hog and rhinoceros, can see objects best when near them. Those whose eyes are too sensitive to bear the bright light of day, only go out during the night, like bats, or even hide themselves under the earth, as the armadillo and hedgehog. Those creatures which are the weakest, being on that account the more timid, are gifted with a keen sense of hearing. This enables them to avoid danger. The hare, the rabbit, the jerboa, the mouse, and other rodentia, on hearing the slightest noise prepare for flight. The more powerful or courageous races, the lion, tiger, cat, and lynx, whose sight is keen, even at night, have short ears and weak hearing, the strength of one sense generally compensating for the weakness of others.

With the carnivora the sense of taste becomes an eager, sanguinary appetite, while the herbivorous animals require a delicacy of taste to enable them to distinguish the nourishing plant from that which would poison them. “Thus,” says Virey, “nature adapts the constitution of each individual to its destiny on earth.” In depriving the armadillo and pangolins of teeth, she covers them with a coat of mail or scales. In making the hedgehog and porcupine weak and defenseless, she enables them to raise at pleasure a forest of sharp quills, and these animals have only to roll themselves up and become a prickly ball, which is quite impregnable. In denying to the herbivorous animals strong teeth and hooked claws, nature has armed the head of the ruminants with formidable horns; finally, she gives to the timid animals, such as the rodentia, either the industry to hide themselves in the earth, like the marmot, the rabbit, and the rat; the agility to jump from tree to tree, like the squirrel; or great quickness in running, and power to take immense leaps in fleeing from danger, as the kangaroo, which bounds along like a grasshopper. The llama is quite defenceless, but, if attacked, it covers its enemies with a disgusting and bitter saliva. The pole-cats, and all of that species, when pursued, throw off such execrable odors that their most ferocious enemies are obliged to give up the pursuit.

Some animals frighten their persecutor by frightful cries, like the howling monkey; others mislead their foes by a number of tricks and careful precautions, and know where to obtain safe shelter and seek obscure retreats.

The smallest species, besides being more numerous and multiplying more abundantly, are also more lively in proportion to their size than the larger animals. Before an elephant or a whale could turn round, a dormouse or a mouse would have made a hundred movements, the smallness of the limbs giving more unity and more control over the body; the shorter muscles contract more easily, and each movement is more rapid than amongst larger creatures. The mammalia form the intermediate class by which the other animals approach to us, and by which the inferior species are grouped around man. In fact, the family of the apes seems to come very near to the human race. On the other hand, the bats, the flying squirrel of Siberia, and other like species, appear to link the birds to the mammalia; while the armadillo and the pangolin, quadrupeds covered either with a cuirass or with scales placed one over the other, seem related to the reptile, such as tortoises and lizards. The amphibious mammalia, such as the seal, sea-cow, and other cetacea, which apparently partake of the nature of fishes, are linked to the large and numerous classes of aquatic animals.

“Thus,” says Virey, “the mammalia form the nucleus round which are grouped the different superior classes of the animal kingdom as being the most perfect type of creation, and the first link in the chain of animated nature next to man.” Let us compare the various other classes with the mammalia. The bird, inhabitant of the air, has received a temperament warm and lively, delicate and sensitive; always gay, full of fire and inconstancy, like the variable region he traverses. The fishes again, the cold creatures of the waters, are more apathetic, and occupy themselves chiefly with material wants; their scaly covering seems to steel them against gentle impressions, and hinder them from feeling acutely, or bringing their intelligence to anything like perfection. The quadrupeds, on the contrary, existing in a medium state, equally below the airy heights, as above the deep abyss of the waters—sharing with man the possession and sovereignty of the earth—seem to hold the middle place between two extremes. They have neither the ardor nor petulance of the bird, the lower sensibility of the fish, nor the apathy of the reptile; but, living as they do on a dry and firm soil, their nature has received more consistency, and their frame more solidity. The locomotion of the quadruped has not the rapidity of flight, nor the nimbleness of swimming; but it has not the painful slowness of the tortoise and other reptiles.

All the series of these mammalia represent a long succession of inferior structures below that of man. The monkey, considered either with regard to his external form of internal organization, seems but a man degenerated. Skeleton, members, muscles, veins, nerves, brain, stomach, and principal viscera resemble ours almost entirely, not only in general structure, but in the ramifications of the lesser vessels. In comparison with us it appears an imperfectly formed being, although it is perfect as regards its own species.

The same scale of graduated inferiority is observed in descending from the monkey to the bat; from the latter to the sloth, to the carnivora, and through all the series.

The smaller the extent of the brain, especially the hemispheres, and the fewer the number of its circumvolutions, the more brutal or more animal do we find the creature. In fact, in the monkey itself, and the quadrupeds with long snouts, which bend toward the earth, everything tends to the growth of the appetites and the development of the senses. They think only of satisfying their physical wants. Of all animals the quadrupeds are the most capable of understanding us; not only on account of their organization, but also because they are the more susceptible of being domesticated. The bird has less relationship with us; for, whatever familiarity or intelligence may be attributed to the parrot or tame canary, the qualities of the dog, the beaver, and the elephant always surpass those of the most clever birds. The more closely a well-organized animal approaches to us, the more it can comprehend us, and we can more easily aid in developing its intelligence. This is especially the case with the mammalia.

Nevertheless, the influence of man upon the domestication of the animals is limited by their fitness for sociability. There is not a single domesticated species which does not, naturally, live in society. Of all the solitary species, there is not a single one which has become domesticated; and sociability does not in the least depend on their intelligence, for the sheep lives in companionship, while the lion, fox, and bear live solitarily. Neither does it depend on habit; for the long continuance of the young ones with their parents does not produce it. The bear cherishes its young ones with as much tenderness and for as long a time as the dog, and yet the bear is amongst the most solitary animals.

Frederic Cuvier has observed three distinct conditions amongst animals:—The solitary species, such as cats, martens, bears, and hyenas; those which live in families, such as wolves, roebucks, etc.; those which live in societies, such as beavers, elephants, monkeys, dogs, seals, etc.

Cuvier has devoted himself to the study of these societies. He follows the progress of the animal, which, born in the midst of the flock, is there developed, and which, at each epoch of its life, learns from all which surrounds it to place its new existence in harmony with that of the old ones. The feebleness of the young animals is the cause of their obedience to the old, which possess strength; and the habit of obeying once adopted by the young, is the reason why the power still remains with the most aged, although he has become in turn the most feeble. Whenever a society is under the direction of a chief, that chief is nearly always the most aged of the troop. Mons. Flourens thinks that this order may, perhaps, be disturbed by violent passions. If this be the case, the authority passes to another: and, having commenced anew by reason of strength, they preserve the same by habit. There are, therefore, amongst the mammalia, species which form real societies; and it is from these alone that man takes all domesticated animals. The horse becomes, by domestication, the companion of man; and of all animals of his species is the most naturally so.

The sheep, which we have reared, follows us, but he also follows the flock, in the midst of which he was born. According to Cuvier, he looks upon man as the leader of the flock. Man, says M. Flourens, is to the animals only a member of their society; all his art is reduced to making himself acceptable to them as an associate; for, let him once become their associate, he soon becomes their chief, being superior to them in intelligence. Man does not, therefore, change the natural state of these animals, as Buffon says; on the contrary, he profits by it. In other terms, having found the animals sociable, he renders them domesticated; and thus domestication is not a singular case, but a simple modification, a natural consequence, of animal sociability. Nearly all our domestic animals are naturally sociable. The ox, goat, pig, dog, rabbit, etc., live, by nature, in society; that is, in herds or flocks.

The cat is not really a domesticated animal—it is not subdued, only tamed; in the same way the bear, lion, and tiger even might be tamed, but not domesticated. Man’s influence will make a sociable animal domesticated, but a solitary animal he can only tame.