Fig. 274.—Gorilla. Gorilla gorilla, ♀. × ⅛.
If it were not for the fewness of the Anthropoid Apes, and their nearness to Man, it is doubtful whether the Gorilla would be ranked as a distinct genus,[[421]] for in internal structure it is very near the Chimpanzee. The microscopic character of the investigations into the anatomy of Man have somewhat dimmed the proper sense of perspective, and have tended to throw into greater prominence than seems necessary the divergences of structure seen in the Gorilla. Dr. Keith[[422]] has recently summed up and commented upon these divergences, and the following account of this Anthropoid is mainly deduced from his memoir.
The cranial capacity of the Gorilla is greater than that of the Chimpanzee. It is not possible, however, to decide from this point of view whether a given skull is that of one or of the other of these Apes. Some Chimpanzees are higher in capacity
than some Gorillas. But the average is undoubtedly as stated. It is to be noted that there is a correspondence between cranial capacity and size of palate, the correspondence being converse, i.e. the greater the brain the smaller the palate. This applies to Man as compared with his Ape-like relatives, but does not apply so accurately to the Gorilla, which has a more extensive palate than the Chimpanzee; its "brute development" is much greater than that of the Chimpanzee. Not only is the palate larger, but the molar teeth, slightly different in form, are also larger and stronger. This is so plainly marked that "one may say almost with certainty, that any upper molar tooth over 12 mm. in length is that of a Gorilla, and under 12 mm. is that of a Chimpanzee." In the skeleton generally it may be said that the crests for muscular attachments upon the bones are greater in the Gorilla. The nasal bones are more like those of lower Apes in their length, and they have a sharp ridge more marked than in the Chimpanzee, which, however, disappears in aged animals. It is a curious fact that Gorillas often have a "cleft palate," owing to the failure of the palatal part of the palatine bones to meet completely. The general conformation of the skull is less brachycephalic in the Gorilla.
The limbs show a number of small differences, which are associated with a more completely arboreal life in the Chimpanzee as compared with the Gorilla. The latter is approaching the human way of life. In spite, however, of these differences, no hard and fast lines of divergence can be laid down between the two African Anthropoids, for it appears from the many memoirs that have been written upon both that "there is scarcely a feature in any muscle or bone found in one animal which is not also found in the other." The heel of the Gorilla has already been referred to. This is, of course, associated with a plantigrade and therefore non-arboreal mode of progression. Certain of the muscles of the calf of the leg attached to the heel show a more human arrangement in the Gorilla than in the Chimpanzee. It is interesting to find that the muscles of the little toe are diminishing in the Gorilla as in Man. This is most clearly due to terrestrial progression and we may apply the same explanation to Man and ignore tight boots! The arm of the Gorilla is less adapted to arboreal progression. Its proportions differ from those of the arm of the Chimpanzee in that the fore-arm is shorter. In
both animals the thumb is not of much use, and this digit is more retrograde in the Gorilla, not only in proportionate length but in its muscular supply. The hip girdle tells the same tale. It is broader in the Gorilla, and the glutaei muscles are more prominent, all these features being connected with the more erect gait.
The brain of both animals have been studied, but not in the case of the Gorilla from a sufficiently large number of examples to make any generalisations of great value. On the whole, the Gorilla has the larger brain, but this must be discounted by the fact that it also has the larger body. It is a remarkable fact that the Gorilla's liver is much more like that of lower Apes than the liver of other Anthropoids. It has, as has the Chimpanzee, laryngeal sacs. The general conclusion concerning the relative position of the two African Anthropoids seems to be that the Gorilla is the more primitive; and as thus it must approach more nearly to the original parent than does the Chimpanzee, it may be said that it also comes rather nearer to Man, since the Chimpanzee has travelled away from the common stock on another line. The detailed likenesses to Man, however, are not to be unduly dwelt upon; for they mainly come from a tendency to assume the plantigrade mode of progression.
In mental characteristics there is the widest difference between the two Apes that we are considering. The Chimpanzee is lively, and—at least when young—teachable and tameable. The Gorilla, on the other hand, is gloomy and ferocious, and quite untameable. When angry the Gorilla beats its breast, a statement that was originally made, we believe, by M. du Chaillu, but which has been disputed, though it appears to be perfectly true. A young Gorilla, exhibited some time since in the Gardens of the Zoological Society, could be observed to do so. The cry of the Chimpanzee is different from the "howl" of the Gorilla. An immense amount has been written upon the ways of this animal in its own home, including much that is legendary. The Gorilla has been said to lurk in the depths of the forest, and to stretch down a prehensile foot to grasp and strangle an unfortunate black man passing below. It is said, too, to vanquish the Elephant by hitting it hard upon the trunk with a stout stick, and to crumple up the barrel of a rifle with its powerful teeth.
Apart from the doubtful "Pongo" and "Engeco" of Andrew Battel, our first intelligence concerning the Gorilla is due to Dr. Savage, after whom, indeed, the late Sir Richard Owen called the animal Troglodytes savagei, a name which has to be abandoned in favour of an earlier name.