At the back of our tongues, and also of those of the Gorilla, is a little flap, rather hard and gristly in us, and only membranous and soft in the Ape, which covers over the top of the air-passage into the windpipe when any food is swallowed. The food or drink would otherwise get into the air-passage, and would be constantly going “the wrong way.” Immediately under this flap, or, as it is called, the epiglottis, is a space limited in front by the hard substance we call in our throat the “Adam’s apple,” and at the bottom of it are the movable structures by whose action voice is produced. Now, in the this space is not shut in front as it is in us, but there are two openings in it, one on either side, which lead to a complicated sac or pouch. This pouch is made of thin membrane, and covers, when blown out like a bag—for the air coming out of the windpipe can be forced in—the front of the windpipe, and projects sideways under the muscles of the throat, and even amidst those of the armpits. The Gorilla can thus blow his neck out, as it were, and when he is yelling, the air in the bag or pouch must resound. Possibly this great bag of air may have something to do with making the body lighter when the animal is climbing and using all the force it can with its arms. These so-called “laryngeal” pouches are found in many Apes and Monkeys, but their double opening into the space below the little flap is peculiar to the great Apes, which are sufficiently man-like as to be called by the term Anthropoid—the Gorillas, their allies the Chimpanzees, the Orangs, and the Siamangs.[6] All the other Monkeys of the Old World with sacs have but one opening into a space, or, as it is termed, the ventricle of the organ of voice, or larynx. The Monkeys of the New World have a different arrangement of air pouches, which will be noticed in the proper place.
The Gorilla has one little peculiarity which distinguishes it from all other Apes and Monkeys, and which causes it to be more like man, and insignificant as it may seem, it is of some interest. In man there is a decided projection of bone behind, or rather below the ear, and this is called the teat-shaped process of the ear-bone (Mastoid process), and is of importance to the organ of hearing and also to the muscles which steady and keep the head erect, and allow of its being moved in particular directions. This process exists to a certain extent in the Gorilla but not in the Chimpanzee, Orang-Utan, or in any other of the Quadrumana. It is smaller in the Gorilla than in man, but it is made up, as in us, of a number of spaces enclosed by bones which have to do with the organ of hearing in some way or other, and which are lined with membrane. On the outside a muscle is attached, which passes downwards and inwards to the top of the breast-bone, covering the great blood-vessels and nerves of the neck.
In examining this process of bone, attention is of course drawn to the ear itself, and there is no doubt of the remarkable resemblance of those of man and of the Gorilla. The great Ape has evidently a very quick sense of hearing, for it gets out of the way of men as quickly as is possible, when it can only hear them in the forest and jungle, but that it should have the outside ear fashioned nearly after the resemblance of that beautiful structure in man is very remarkable. The ear of the Gorilla is smaller in proportion to the size of the head than those of other Apes, and is about the same length, but broader than that of man; the lobe, which is perforated by us for earrings, is perhaps less perfect in the Gorilla, but all the curves and folds, which are so complicated yet so graceful in the human ear exist in it, modified more or less, and not so harmonious in their general symmetry, as in man.
With all its great strength, the head of the great Ape cannot move as readily on the neck as that of weaker man, for the skull is not placed on the neck end of the back-bone quite in the same manner, and its position is not that which is admirably (as in us) adapted for carrying the head erect. One of the greatest marvels in the structure of man is the manner in which the tender mass of nerves called the spinal cord or marrow passes out of the hard skull into a bony canal down the spine, and yet does not suffer injury as head and back move and roll about.
The spinal cord or marrow passes out of the skull through a special opening, on the outside of which is a joint on either side. These joints fit on to corresponding ones on a ring-shaped bone (atlas bone), and this bone rests on one equally hollow, and which has an upward projection which enters the ring (axis bone), and is clasped to it by a strong ligament. It is this projection which prevents the spinal marrow from being injured by the head moving too freely, and yet life hangs almost on a thread, for were this strong ligament to break the soft nerve would be pressed in by the bony projection, and death would ensue. All the motions of the head are connected with these bones and their joints, and the way in which it is carried is in relation with the position of the opening in the skull for the spinal marrow. If the head is to be carried erect, as in man and in many birds, the opening is far from the back part of the head. If the face is to look upwards, as it does in a pig or dog, the opening is very far backwards. In the Gorilla it is not quite at the back, but further in that direction than in man, and hence the face of this Ape is more liable to be looking upwards than forwards. This is really the case, for the natural position of the animal is not erect, but on all-fours, and then it wants to look, not on the ground, but upwards and forwards, by tilting the head. Many of the great muscles of the back crest have to do with this. It is noticed also that the joint which permits the head to move on the ring-shaped bone (the atlas bone) is not so long or curved as in man, and therefore the movements of the Gorilla’s head are restricted.
All accounts of the life of a Gorilla tell of its moving rapidly amongst trees, climbing readily and noiselessly, and gathering its food constantly. It is therefore necessary to examine into the manner in which this is done, and how it relates to the shape and anatomy of the creature.
In climbing trees, the Gorilla, like a man under the same circumstances, lifts up the arms over the head, and clasps or holds on with one hand, but the position of the hand is not the same. Apes seize instinctively with the knuckles towards them, and not with the ends of the fingers and palm as man: and this makes a great difference, for the muscles of the back are therefore more important to the Ape than those of the chest in climbing. Then with some muscular effort the body is lifted or rather drawn up, so that the unemployed hand can reach and clasp higher than the other; and having thus two hands holding on to a bough or a tree, the muscles of both arms are used to draw up the ponderous trunk, head, and limbs until the face comes more or less on a level with the wrists. When this is accomplished, one of the arms is suddenly forced upwards to enable the huge grasp of the fingers to tighten upon a higher fixed point, and the “hand-over-hand” process is continued as long as is necessary. Doubtless the clasping feet assist in this movement, which is only rarely performed by man, but which is one of the commonest with the great Ape. A sailor or an acrobat may often use the muscles which are required to perform this feat of carrying upwards the body with the aid of the arms, but ordinary people rarely employ their energies in this manner; the Gorilla, on the contrary, must climb often and for some distance every day of its life, both for food, amusement, and for shelter. It becomes, therefore, an interesting question whether the Gorilla has any special muscles or bones which enable it to climb easily and rapidly, and for a considerable time, or whether there are the same kinds of bones and muscles in its hands, arms, and shoulders, which are to be found in man modified more or less. The results of careful inspection have proved that, although there are no peculiar structures given to the great Ape wherewith it may climb, still the bones of the arms and shoulders, and the muscles which are attached to them, greatly as they resemble those of man, are larger and stronger. Bone for bone, and almost muscle for muscle, the climbing limbs of the man and the Gorilla may be compared with extraordinary exactness; the structures of the last-mentioned being, as it were, simple exaggerations of the former, and the increased size bearing a distinct relation to the agility and energy displayed. It must be remembered, however, that whilst in man the muscles of the chest assist principally in climbing, in the Ape those of the back and shoulders are the most important.
FOREST IN THE GABOON COUNTRY—THE LAND OF THE GORILLA.