As a whole, the hand of the Chimpanzee is, in proportion to the size of the animal, larger than that of the Gorilla, but the thumb is shorter, and this makes it more Monkey-like than human; and the same may be said of the lower limbs, for the thigh-bone and those of the leg, although greatly resembling those of the Gorilla, have many peculiarities which make them resemble those of the less important Monkeys. Finally, with regard to the foot, that of the Chimpanzee is more Monkeyish than that of the Gorilla. The great Ape’s foot has many peculiarities which make it differ from that of man, and these are all magnified, as it were, in the Chimpanzee, whose foot, therefore, is all the more unlike ours. It is especially adapted for grasping and climbing, and less well suited for occasionally standing erect and walking. Its heel is short and slender, and the toe-thumb is smaller, and the whole foot is slenderer, than the Gorilla’s. Moreover, it is more turned in.
When young, there are no crests on the head, but with age a small one grows on each side in front, running from about the centre of each side of the brow ridge over the receding forehead, and joining together in the middle line, close to the top of the skull. This meets a larger and stronger one, which is a miniature of the head crest of the Gorilla, and which reaches from ear to ear. The use is probably for the attachment of the masticating muscles at the side, and for that of the muscles of the neck behind; but it is also a kind of ornament of the males.
Strong as this Ape is in its loins, from its extra ribs, the hip-bones seem narrow from side to side; and one of the causes of this is interesting, not only because it is also noticed in the other great Apes, but also because it is one of their marked distinctions from man.
The pieces of the back-bone (or vertebræ), as they pass between the hip-bones behind, unite them together, and degenerate until they form the curious little tail-end of the back-bone, which in us, and in the Apes, is curled slightly, with the concave part of the bend forward. The pieces unite strongly to each other above and below, and form really one bone, which is called the sacrum. Now, if these pieces were nearly or quite as stout and broad as those higher up, the hips would be wide apart; but if they become narrow, the hips will be all the closer together. In man, the pieces are broad, and the sacrum, as a whole, is so also, and the hips are widely separate; but the reverse is the case in the Apes.
BRAIN OF CHIMPANZEE.
This difference in the breadth of the bone and the width of the hip has evidently to do with the maintenance of the erect posture in man, and the inability to keep erect for long, and comfortably, by these great Apes. The larger the surface of the sacrum, the greater is the mass of muscle passing to the back and downwards; and this is small in comparison in the Chimpanzee.
Where the proper vertebræ of the sacrum end—that is to say, the pieces of the back-bone which are placed between the hip (ilium) bones—the tail begins. It is made up of three stunted bones, which are something like ill-made back-bone pieces (vertebræ); they are usually inseparably joined together to make a special bone, which is broad above, and tapering below. This bone, the rudiment of the tail, which, from some fancied resemblance to a Cuckoo’s back, has been called the cuckoo-bone (os coccygis), is covered by skin and embedded in muscles, which do not allow it to stick out visibly even as a stump; for its tip is curled inwards. This apology for the member which is so vastly important in many Monkeys is narrow in the man-like Apes, the black Chimpanzee included; but it is a little wider in man, although the general construction is the same. Could these bones—which, by their being united, form this rudiment of a tail—be disunited and increased in number, stuck out, and covered with skin and muscles, something like the very Monkey-like appendage would be formed. But noble tails are not the gifts of the higher Apes, as they are called, from their many points of resemblance in structure with man, and even in the smaller Monkeys they are extremely variable belongings, being given to one kind and not to another in a manner far beyond our philosophy.
The Chimpanzee has a long palate, like the other great Apes of the West African woods. Moreover, it has a uvula in the back of the throat, and the back of the tongue is marked with great papillæ, which take up the shape of a T. It does not do more than grunt “hem,” and bark after a fashion; and the use of some great air-pouches, which resemble those of the Gorilla, are therefore not very apparent. But the bony structures of the palate are interesting, for at the back of it they do not form a simple knob, as in the Gorilla, but resemble those of man, and there is a little prominence, with a festoon curve on each side.
It lives upon vegetable food, and its teeth are admirably suited for it; they are of the same number as those of the rest of the great man-shaped Apes, and do not differ very much from them. The front teeth are large, and project, and do not bite very up and down on the tips, so they wear behind quicker than in front, their general shape being rather peculiar and distinctive. Female Chimpanzees have smaller eye-teeth than the males, and all have them with a sharp edge behind, so that they can cut a pine-apple as well as pierce it. Behind them are the pre-and true molars, but the last tooth of the upper jaw looks small, for its hinder projections or cusps are small. In the lower jaw the last tooth has a fifth cusp, but it is smaller proportionately than in the lower Monkeys; and the first pre-molar has its front and outer angle stuck out very much after the fashion of the Baboons. Now these are little matters, which do not appear to have anything to do with causes and effects, the adaptation of means to ends, or which do not enable the creature to chew and crush its food a bit the less well, or better than others; they refer to some hidden mystery which unites apparently very different animals together in the scheme of creation. Thus the Chimpanzee has human-like, Gorilla-like, Baboon-like, and other Monkey-like peculiarities, so far as the teeth are concerned, and yet which do not interfere with the successful mastication of the food. We may make theories about them of supreme interest, which may explain why animals are alike and unlike, and how the structures of superior animals were foreshadowed in those of lower ones, and the structures of the latter in those of still simpler forms of life.