THE HAND AND THE FOOT (p. 2l).--_Man Compared with the_ _Ape_.-- The peculiar prehensible power possessed by the hand of man is chiefly dependent upon the size and power of the thumb, which is more developed in him than it is in the highest apes. The thumb of the human hand can be brought into exact opposition to the extremities of all the fingers, whether singly or in combination; while in those quadrumana which most nearly approach man, the thumb is so short, and the fingers so much elongated, that their tips can scarcely be brought into opposition; and the thumb and the fingers are so weak that they can never be opposed to each other with any degree of force. Hence, though well suited to cling round bodies of a certain size, such as the small branches of trees, the anterior extremities of the quadrumana can neither seize very minute objects with such precision nor support large ones with such firmness as are essential to the dexterous performance of a variety of operations for which the hand of man is admirably adapted. The human foot is, in proportion to the size of the whole body, larger, broader, and stronger than that of any other mammal, save the kangaroo. The surface of the astragalus (ankle bone) which articulates with the tibia, looks almost vertically upward, and hardly at all inward, when the sole is flat upon the ground; and the lateral facets are more nearly at right angles to this surface than in any ape. The plane of the foot is directed at right angles to that of the leg; and its sole is concave, so that the weight of the body falls on the summit of an arch, of which the os calcis (heel bone) and the metatarsal bones form the two points of support. This arched form of the foot, and the contact of the whole plantar surface with the ground, are particularly noticeable in man, most of the apes having the os calcis small, straight, and more or less raised from the ground, while they touch, when standing erect, with the outer side only of the foot. The function of the _hallux_, or great toe, moreover, is strikingly contrasted in man and the ape; for, while in the latter it is nearly as opposable as the thumb, and can be used to almost the same extent as an instrument of prehension, it chiefly serves in the former to extend the basis of support, and to advance the body in progression.--DR. W. B. CARPENTER. FIG. 70. [Illustration: _The Leg in standing._]