exclusively for higher purposes in man alone. It is also to be remarked, that in bats the faculty of flying is conferred upon them at a great sacrifice. It flies, in fact, at the expense of the powers of running, walking, and handling objects, in all which it is deficient. This is because raising a body and carrying it through the air requires so much more power than to carry it upon the surface of the earth that it is only by a concentration of its whole muscular force that it has been accomplished.

This might have afforded a lesson to those among our own species who have sometimes sought to invent wings by which to move through the air. These they have attached to the upper extremities. It is obvious that, as Nature has only been able to make one of the Mammalia fly by devoting nearly its whole muscular power to the object, if man is ever to accomplish this purpose it must be by an imitation of Nature in this particular. It is probable that the muscular power of man is as great in proportion to his weight as that of the bat. Could an apparatus, therefore, be contrived by which the whole muscular power of the body and limbs was brought to bear upon wings properly constructed, it is not impossible that the flight of bats might be imperfectly imitated.

There are other animals among the Mammalia that exhibit a similar structure in a less marked degree, as the flying lemur, flying squirrel of our own country, and the flying opossum of Australia, but these may be passed over, and we come to those in which the construction deviates from that of man in an opposite direction, being intended to enable them to live and move in and upon the water. They are of two kinds, the amphibious, as the seal, the morse, the dugong, capable of moving both on land and water; and the cetaceous, as the whale, dolphin, and porpoise in the water alone. The amphibia retain the four limbs, the bones of which are constructed like those of quadrupeds, but they are short and enveloped by flesh and skin, whilst a membrane or web connects the fingers gether to adapt them for

to

Fig. 14.

Seal.

swimming. The cetaceous animals are still farther removed from man in structure, the pelvis and hind limbs being want

Cetaceous animals are sometimes popularly confounded with true fishes. They differ, however, in essential particulars. They are warm-blooded; they are viviparous and suckle their young; they breathe air; their organs of circulation, respiration, and digestion, are like those of the other Mammalia. They are to be regarded as inhabitants of the surface of the water, rather than, like fishes, as inhabitants of its depths.

Fig. 16.

Camelopard.

Beside these general modifications of structure which characterize certain large divisions of this class, there are others more limited in their extent, but equally illustrative of the relation of structure to purpose, and of the struc ture of different parts to each other.

There is a striking disproportion between the anterior and posterior extremities of many animals, as compared with the average standard of the class. In the camelopard, or giraffe, the head is elevated to a height of eighteen feet, by

the length of the neck, the shoulders, and the fore legs, the hind parts being only about half as high. It is thus the most lofty of quadrupeds, and is adapted to feed, as it does almost exclusively, upon the tender leaves of trees. In other animals we find a similar disproportion in the hinder parts of the body, which qualifies them for different motions and a different mode of life, -as in the jerboa and the kangaroo. In these the hind limbs are many times longer and stronger than the fore limbs, enabling them to advance by enormous leaps, whilst they can scarcely walk or run at all.

In the lion and other animals of similar habits, the neck is short and strong, with great strength in the shoulders and fore legs. These correspond to their powerful head and jaws, and qualify them for seizing and bearing away their prey. Were the neck like that of the horse, it would be impossible to furnish it with muscles strong enough to lift their large head and the prey which they have seized, at the end of so long a lever, without in

creasing the size to absolute monstrosity. But in the horse the head is small and light; his food requires no power to raise it, but being intended for rapid motion, and having therefore long legs, he needs a long neck to reach the herbage on which he feeds. He is not intended to use his head or mouth for the purpose of defence, but trusts for safety to a rapid flight, and repels his enemies with his heels. Compare him in these particulars with the bull, whose instruments for defence are planted on his head. His neck must necessarily be shorter and stronger. But as his food is also herbage, the fore legs are short, or he could not reach the earth. These variations all follow from the design of crea

tion and the necessary harmony of structure. In the one case, we have an animal, fleet, with long legs, a long neck, and small head, who flies from his enemies, and, when approached, defends himself with his heels. In the other, we have another with a large head, a thick, short, sturdy neck and chest, short legs, not so well fitted for rapid motion, but well adapted for powerful resistance or attack with his head and horns.

In this way we may trace the connection of each peculiarity of formation with some use for which the parts are designed. With legs of a moderate length, the neck of the camel is long, for he is to seek his food on the ground; but it is slender because his head is small, the nature of his food not requiring a large one. With a head equally small, the neck of the giraffe is long, and raised upon shoulders of great height, because he is to seek his food above. The elephant has a very thick, short neck, on account of the immense weight of his head. His head is large because he must have great strength of bone to give support to his heavy tusks; his tusks are necessary as means of defence, and to aid him in procuring his food, which consists frequently of the branches of young trees. But with his large head, his short neck, and his long tusks, he cannot reach the ground; he could neither eat nor drink, he would starve in the midst of plenty but for his long trunk, which conveys water, and the food his tusks have gathered, into his mouth. Such a contrivance was absolutely demanded by the rest of his structure, and a similar necessity implies a similar provision in the mastodon, the great extinct animal of America.

Such are a few examples of the adaptation of structure to purpose, and the harmony which exists among the different parts of the same animal. Still there are a vast many peculiarities of which we cannot perceive the object; nor can we understand the design of differences among those species whose food, habits, and mode of life are apparently alike. Yet we may reasonably conclude that such differences are not without a purpose, because wherever we get at all the facts of the case we perceive such a purpose. Nor is it any objection to this view, that animals so often depart from the mode of life and the kind of food which is natural to them. There is in all a certain power of accommodation to external circumstances without permanent injury. It is no proof that the dog is not a carnivorous animal, that it can be brought to thrive on a vegetable diet; no proof that horns are useless to the ox, because there is a variety without them, any more than that our hands are useless, because some men can effect the same purposes with the mouth or the feet. In those laws of structure which relate to the essential functions of animal life, respiration, circulation, &c., such variations do not exist; in secondary provisions a great latitude and power of accommodation are observed. These secondary provisions are made, not for purposes absolutely essential, but for the comfort, convenience, or even the luxury of animal existence. To argue in any case that a provision is without an object, because it sometimes fails of that object, or because the same is sometimes accomplished without it, is a mode of reasoning forbidden by the whole analogy of Nature.

The division of the Mammalia into orders is founded upon considerations of this nature. The structure of an animal being found to correspond to its character, mode of life, and kind of food, those which have a similar structure will of course resemble each other to a certain extent in other particulars. From the formation of the extremities of an animal, particularly the anterior, we can judge of the degree of address of which he is capable, and of the kind of motions he is able to perform; and from the structure of his teeth, what is the nature of his food. Thus, the fore feet of animals may be either enveloped in hoofs, ike those of the horse and the ox; armed with claws, like those