Behind the canine teeth are, on each side in both jaws, five crushing teeth, that is to say, ten in each jaw, and twenty in all. In the upper jaw there is a continuous row of teeth from the canines in front to the last of the crushers, which occupy the position of the upper wisdom teeth of man, but in the lower jaw there is not this serried row of teeth, for, between the crushing ones and the canine, there is another space or diastema into which the upper canine tooth fits when the mouth is closed.
SKELETON OF THE GORILLA.
All these hind teeth are made to endure constant grinding, one over the other, in masticating, besides frequent shocks—as when nuts are cracked—and to last for years. Covered with a beautiful enamel, which gives them strength and smoothness, they are safely fixed by fangs in sockets in the bone, in such a manner that the nerves and blood-vessels supplying them do not suffer from pressure. They are not quite flat at the top, for then they could not grind, and they are not acutely sharp-pointed, for then the points would prevent the side-to-side movement of the jaw, and would be broken off; but they have rounded projections, or cusps, on them, separated by grooves, so that those of the teeth of one jaw can fit into those of the other. All these teeth are not quite alike, and they are divisible into two kinds, the three hinder ones being the molar teeth, from Mola, a mill-stone, and the two in front of them being called false molars or pre-molars (front molars). Every one who has had a back tooth (a molar) taken out, will remember its three fangs, and in a Gorilla there would be the same terrible wrench in extracting a molar for the same reasons as with us. But, fortunately for it, tooth decay is unknown, and the molars, with their three fangs, last as long as life. The pre-molars have two fangs only in man, but it appears that sometimes there are three to those teeth in the upper jaw of the Gorilla, and two only in the lower. They are smaller than the true molars or three back teeth, and in front of them; and that nearest the canine tooth is often tall, and almost like a four-sided pyramid in shape. The size of the crushing or molar teeth is very distinctive of the Gorilla when it is compared with the other great man-like Apes, for the upper ones are equal in size, and in the lower jaw the hindmost tooth is larger than the others. Moreover, these lower teeth have five cusps or projections. There is a ridge extending obliquely across the crowns of the lower molars from an inner to an outer cusp; and the cross-like grooves of the upper surface of the corresponding teeth in man are not seen. The manner in which the teeth of the Gorilla differ from those of other Apes will be mentioned in the several descriptions. Milk teeth, or those of the first set, are found in baby and young Gorillas, and when they fall out the permanent set come out of the jaw and replace them, adding also to their numbers. The long canine teeth are characteristic of the old males, and those of the females and young are much smaller. The thirty-two teeth of the Gorilla, eminently adapted for a mixed vegetable diet, are therefore arranged as follows:—Upper jaw—four incisors, two canines, four pre-molars, and six true molars, and there is the same number in the lower jaw.
It is a very remarkable fact, and one which will be of some interest in comparing one of the other great Apes with the Gorilla, that the skull of the young Gorilla (of both sexes) and that of the full-grown female differs materially from that of the male in the absence of the prominent ridges of the top and back of the head. This gives a roundness to their skulls which would at first sight lead to the belief that they could not belong to the same species.
Living upon such nice things as sugar-canes and pine-apples, the Gorilla has a long and well-formed tongue to taste them with,[5] and a good nose to enjoy their scent and fragrance. The nostrils are open, and look downwards, being separated by a moderately wide piece of flesh covering, gristle, or cartilage, and they are protected above by very dense bones, which form the slight ridges called the nasal bones. Up the nose a passage leads to the air spaces in the bone of the front of the head, and they and some curiously curled bones not very far from the nostrils are covered with a delicate membrane well supplied with the nerves in which the function of smell exists.
Both the natives and Du Chaillu allude to the roaring and yelling of the old male Gorillas, and it will be noticed further on that the young ones can make noise enough. Dr. Savage was told that when the male is first seen he gives a terrific yell that resounds far and near through the forest, something like Kh—ah! Kh—ah, prolonged and shrill, and others have compared the noise to distant thunder. They have an organ of voice on the top of the windpipe, made on the plan of that of man, but deficient in many respects, and especially in those fine adaptations of structure which produce the human voice. But there is a very remarkable arrangement in their larynx, as it is called, which, although it has nothing to do with the formation of sound, may possibly make it more resonant and growling, and this is one of the things which separate the great Ape from man in matters of mere construction.
THROAT OF GORILLA.