The ridges and crests on the top and back of the Gorilla’s skull are larger than those of any of the great flesh-eating animals of the cat tribe, and it has therefore been thought that they were a proof of the occasional bad habits of the great Ape, and of his indulging now and then in negro flesh. Large as are the crests in the old males, they are barely present in the females and young, and they must be regarded partly as of use to the larger animals, and partly as ornamental; for in animal nature, as a rule, the gentlemen are more beautiful than the ladies, the idea of beauty being, of course, very much a matter of taste. They are evidently protections against falls, and they also give origin to muscles. The back crest, when looked at from behind, is almost fan-shaped, the bone being broad, and the great muscles of the neck and back are attached to it. They pull the head backwards, and the single, long crest on the top gives origin to the muscles, which pass downwards on the temples to the lower jaw. Indeed, the energy of the muscles of the side of the head is principally devoted to the lower jaw, to its crushing, crunching, and masticating offices, for the food, although often soft enough, is occasionally inside the sugar-cane, and several harder woods. The powerful upper jaw is, of course, attached to an equally strong lower one, which forms the front and lower part of the face. The upper jaw reaches out far in front of the eyes and nostrils, and is straight rather than bulged, and appears narrow, from side to side, in comparison with the great, wide cheek-bones, but it looks formidable with four strong front teeth, projecting only slightly, and a large, long, eye tooth on each side, sticking out rather far below the others.
On looking at the under surface of the roof of the mouth and palate, the cause of the length of the front of the face is seen. Instead of the back teeth forming an open curve around the roof of the mouth, as in men, they are placed in a long, and almost parallel straight row. Five great teeth on each side thus form with the bone, into which their fangs are planted, a long side to the face. In front of these is the large eye, or dog tooth (canine tooth), mentioned above.
The palate and roof of the mouth are long and comparatively narrow, and hence no Gorilla could speak distinctly, or use his tongue glibly enough to talk as a child. Howling and a kind of bark may, on the contrary, be done to perfection.
But although of no use as regards speech, the long roof of the mouth, with its wide ranges of teeth, is of great importance to a vegetable-eating creature, which does not want the sugary juices of its food to run out of the corners of its mouth, and which spends the greater part of its time in filling its capacious stomach.[4] The lower jaw fits the upper one, and when its teeth clench with those above, the cavity of the mouth is nearly shut, and it is quite closed by the lips and cheeks outside.
As might be expected from the great muscles which unite the lower jaw to the skull, it is large and strong, but it has no projecting chin, and this slopes in a retiring manner. The side of the jaw which supports the teeth is, as in man, curved upwards behind at what is called the angle. The jaw is very movable, and can act sideways in munching, or up and down, as in biting; and having these powers—thanks to the action of different sets of muscles—it has teeth fashioned to bite, and to crunch, and to chew. They greatly resemble those of the upper jaw, on which they work, and a superficial view of them all leads to the opinion that they greatly resemble those of man; there are, however, many differences. As in the upper jaw, the front and eye teeth are nearly straight in front, the last-mentioned projecting outwards, and the front teeth biting inside the upper ones; and the back teeth are in straight rows also.
The following story is told by Du Chaillu to illustrate the cause of the wearing of the front teeth of the Gorillas. He had gone into the interior, and was suffering from hunger, so went out into the forest for game. Not finding any, he was about to retrace his steps, when he heard the unmistakable roar of a Gorilla. He writes, “I plunged forward into the thick of the forest, breaking, as I went along, small boughs to enable me to find my way back, and tearing my clothes in the thorny underwood. The roar became nearer, and seemed to shake the ground under me. I heard the rustling of the branches, and fancied there must be more than one. The excitement of the moment was great, and was increased by the prospect of obtaining food for all our party. Suddenly the roaring ceased. I stopped, thinking that it was a male, which was preparing to advance on me. But I listened in vain—the beast had fled. When I reached the spot I saw nothing but broken branches of trees. I measured some of them with my thumb, and found boughs of five inches’ diameter broken in two by the powerful grip of this monster of the forest. Although disappointed in my chase, I was glad to find a corroboration of the explanation I had given of the wearing down of the animal’s front teeth, for some of the branches plainly bore the toothmarks.”
UPPER JAW. PALATE. UNDER JAW.
THE TEETH OF THE GORILLA.
As the teeth of the Gorilla are admirably adapted for their duties of masticating and biting vegetable food, sometimes soft and sometimes hard, and as they resemble in number and general arrangement those of man, it is necessary to notice them briefly. They are of three kinds, the front ones, which bite when the jaw is moved up and down, the large eye teeth (or dog teeth), which pierce, and the back teeth, which crush and grind. The first-mentioned are called incisor teeth or cutters, and there are four in the upper and four in the lower jaw, as in man; the inner two in each jaw being larger than the outer two. They project slightly, and those of the upper jaw cut on the lower ones, and are, when the jaws are clenched, in front or “over-hung.” In shape they are adapted for biting a piece out of anything, and they have one fang each, which fits into a socket in the jaw. In the upper jaw there is a space between the incisor teeth and the great eye or dog teeth. This is one of the matters which distinguish the jaw of the Gorilla from that of man, whose teeth are continued in a row without any spaces where the gum is visible between them. The cause of the space is that the lower eye tooth is so large and long that when the mouth is closed it fits in there. This space is called a “diastema,” and, as it is a term which will often be mentioned, it is necessary to notice that it is taken from the Greek word διάστημα, “an interval.” In the lower jaw the incisor teeth are succeeded by the eye teeth without any diastema. The eye or dog teeth are usually called canines, from Canis, a dog, they being very distinct in that animal. They are four in number, two being in each jaw, one on each side, and those of the upper jaw are long and pointed, being rounded, moreover, outside, and marked by grooves inside. The lower canines are nearly as large as the upper ones, and, as already noticed, fit in the diastema in front of those of the upper jaw.