“A very curious Ape, the Siamang, was rather abundant, but it is much less bold than the common Monkeys, keeping to the virgin forest, and avoiding villages. This species is allied to the little long-armed Apes of the genus Hylobates, but is considerably larger, and differs from them by having the two first fingers of the feet united together, nearly to the end; whence its name. It moves much more slowly than the Hylobates, keeping lower down in the trees, and not indulging in such tremendous leaps; but still it is very active, and by means of its immense long arms—five feet six inches across in an adult about three feet high—can swing itself along among the trees at a great rate. I purchased a small one, which had been caught by the natives, and tied up so tightly as to hurt it. It was rather savage at first, and tried to bite, but when we had released it, and given it two poles under the verandah to hang upon, securing it by a short cord running along the pole with a ring, so that it could move easily, it became more contented, and would swing itself about with greater rapidity. It ate almost any kind of fruit and rice, and I was in hopes to have brought it to England, but it died just before I started. It took a dislike to me at first, which I tried to get over by feeding it constantly myself. One day, however, it bit me so sharply while giving it food that I lost patience, and gave it rather a severe beating which I regretted afterwards, as from that time it disliked me more than ever. It would allow my Malay boys to play with it, and for hours together would swing by its arms from pole to pole, and on to the rafters of the verandah, with so much ease and rapidity, that it was a constant source of amusement to us. When I returned to Singapore it attracted great attention, as no one had seen a Siamang before, although it is not uncommon in some parts of the Malay peninsula.”

There are some interesting points about the relation of the construction of this animal and its method of moving. Thus, in grasping a bough with the arm at full length above the head, so as to leave it with a swing in order to grasp another rapidly and for a correspondingly short period of time, the fingers require to be kept together as much as is possible, and to remain more or less bent on the palm. The long thumb may or may not be used, but in order to move efficiently it must be free, and also strong. Now in the Siamang these necessary peculiarities are present, and the common use of the finger and thumb in taking hold of things in the ordinary manner is sacrificed to them, and there is little or no delicacy of fingering or of prehension. Moreover, the fingers and thumbs are extremely thin and delicate, and in order to render the first finger less movable, it is, to a certain extent, deficient in its muscles of extension; and the common bending or flexor muscle of the fingers is very independent of that of the thumb. In compensation there is a special muscle found in this genus alone, which pulls the top of the second finger towards the thumb.[20] The skeleton of the hand shows that the fingers are slightly curved. There is no doubt that the hand of the Siamang, although it has these peculiar muscles, the curve of the bones, and also the extra bone noticed in the Orangs, is, as far as its skeleton is concerned, much more human than that of the other Apes. The extensor muscles of the fingers resemble those of the Orangs. The hand is larger than the foot in these animals, and the forearm is much longer than the upper arm.

A French naturalist states that the animal can leap, or, rather, swing—for it is done with the fore limbs—with graceful agility at least eighty feet, and the muscles of the arm, which are connected with the chest, aid in this. The pull is from the stationary arm to the chest of the movable body by muscular contraction; and the greater the muscular connection between the arm and chest, the greater will be the movement. In order to provide for this, the great muscle of the front of the upper arm, the biceps (see [page 26]), is not only attached, as in the other Apes and in man, to the blade-bone just above the arm-joint, but also to the chest in front, for it is united there with the great muscle which springs from the ribs and breast-bone, and is attached high up to the arm (pectoralis major). In some of the other Apes this second part of the biceps is attached to a bent projection (coracoid) of the blade-bone, so that it has no direct attachment with the chest itself.

The Siamang can walk fairly in the erect posture by balancing with the arms, or by placing them over the head, and it has a great power of grasp with its toe-thumb. The shape of the foot resembles that of man more than that of the Troglodytes and Orangs, and the heel-bone is strong, and projects but slightly, and the toe-thumb is stout and long. The muscles of the foot are, as it were, more separate than in man, especially the flexors: and there is an extra muscle, an abductor of the third joint of the second toe.

The ability to walk well was proved when a tame Siamang used to walk along a cabin table at sea, without disturbing the crockery; and curiously enough this was better done than were some of the ordinary movements of the hand, for drinking out of the palm was a most ineffective and clumsy effort.

The bones of the foot resemble those of man more than do those of the Apes already noticed; but the first and second fingers are united by a fold of skin.

SKELETON OF THE SIAMANG.
(From the “Cyclopædia of Anatomy
and Physiology.”)

Under the jaw and along the throat of a tame Siamang, a large swelling, not very well covered with hair, was visible enough. This was a vast air or laryngeal pouch, and pressure emptied it into the throat. Hence the creature in this point resembles the Oranges and the Troglodytes, but the use of the sac could not be satisfactorily decided. The sac opens into the windpipe by two apertures, which are in a membrane that unites the base of the tongue and the organ of voice together. It has an uvula.