Orang-Outang (pithecus, Geoffr., or simia, Linn, and Illig.), the common name of the large tailless anthropoid apes of S. E. Asia and the islands of Borneo and Sumatra. Some details have been given regarding the orange under Ape and Chimpanzee. The orang most commonly seen in menageries is the P. saty-rus (Geoffr.), of which the adult has been described as the P. Wurmbii, the pongo of authors and the mias of the natives of Borneo. The pongo or adult orang is more powerful and less anthropoid than the chimpanzee (troglodytes niger, Geoffr.); it represents in Asia the gorilla of Africa, and varies in height from 5 to 7 ft. The forehead is contracted, sloping directly backward, with no projecting superciliary ridges; the occiput is flattened, the canines large, jaws powerful, zygomatic arches strong and expanded, and cranial ridges largely developed; the crown is less flat than in the chimpanzee; the brain cavity of the adult is very little larger than at the period of the first permanent molars, the greater size of the cranium depending on a thickening of the walls and the development of the temporal ridges; the latter commence at the external angular process of the frontal bone, and pass upward, inward, and backward to meet at the junction of the sagittal and coronal sutures, the two including a smooth triangular portion of the frontal; the interparietal crest is about half an inch high, as in the large carnivora, dividing at the vertex, and passing behind the lambdoidal suture to the mastoid ridge, and a rough prominence continues from the point of divarication half way down the occiput.
As compared with the chimpanzee, it comes nearer man in the small portion of the wing of the sphenoid which reaches the parietal, separating the frontal from the temporal, though this character does not hold good in all races of men nor always in the orang; the occipital foramen is further hack, and its condyles are nearer together in front, with double anterior condyloid foramina; from the greater development of the canines, the incisive foramina are further hack; the intermaxillary sutures are not obliterated until the permanent teeth are almost fully developed; the single nasal bone is flat, with no projection beyond the nasal processes of the upper jaw; the inter-orbital space is relatively narrower; the upper jaw has three infra-orbital foramina instead of one, and is larger; the incisors project more obliquely forward; there is a greater height and breadth of the rami of the lower jaw, and greater depth of symphysis. The teeth are in number the same as in man, the chimpanzee, and gorilla, the incisors and canines especially being relatively larger.
The spinous processes of the cervical vertebra are simple and very long, for the muscular attachments rendered necessary by the backward position of the occipital foramen, the great development and weight of the face, and the general anterior inclination of the vertebra) themselves; the spinal column has one general curve behind from the atlas to the beginning of the sacrum, where there is a slight curve in the opposite direction; the dorsals are 12 as in man, the chimpanzee having 13; the lumbar are four, with shorter spines; the sacrum consists of five bones, and is longer, narrower, and straighter than in the chimpanzee; the coccygeal bones arc three, anchylosed together, but not to the sacrum. Continuing the comparison with the chimpanzee, the ilia are more expanded and flatter, and the ischia are less extended outward, making the lower part of the pelvis narrower; the superior pelvic opening is nearly a perfect oval; the chest is ample, as large as a man's, the transverse greater than the anteroposterior diameter; the ribs are narrower and less flattened; the sternum short and wide, composed, below the first bone, of a double series of seven or eight small bones, always distinguishable in the young animal, but not in the chimpanzee; the clavicles very little curved; the scapulae broad and short.
The principal difference is in the relative length of the upper and lower limbs; the arms reach to the heel; in the forearm there is greater space between the bones, owing to the outward curve of the radius; the bones of the hand are elongated, those of the thumb slender and short, not reaching to the end of the metacarpal of the forefinger; proximal phalanges curved for easier prehension and climbing, and the last row not expanded for a wide sensitive bulb of a linger. The femur has no ligamentum teres, giving greater mobility and less solidity to the motions of the hip joint, useful in climbing, but rendering the gait on the ground awkward and shuffling; the bones of the leg are short, with greater space between them, owing to the inward curve of the tibia; the foot is turned more inward, and the os calcis does not project so far back; the phalanges much elongated, the hind thumb not reaching to the condyle of the next metatarsal; it resembles a hand more than a foot. The sutures are obliterated in the adults.
The large canines of these anthropoid apes bear no relation to their food, being used principally as weapons of defence against the larger carnivora, which their great strength enables them to cope with; the smaller the species and the more easily concealed, the less developed are the canines. The capacity of the adult male orang skull is 26 cubic inches, of the female 24, considerably less than in the gorilla, and about the same as in the chimpanzee; in the young, up to the age of about five years, the facial angle is 60°; the extremities preserve the proportions of a six-months human foetus, while in the chimpanzee they are those of a yearling infant. The numerous resemblances to the human structure which have served as arguments for progressive animal development have always been taken from immature specimens of these anthropoid apes, in which the facial angle, teeth, and shape and relative size of cranium assume human proportions, which are lost as the animal advances in age; the docility and gentleness of the young give place to obstinacy and ferocity in the old, as the cerebral development becomes relatively less. - The Bornean pongo has long loose hair of a deep fuscous color, approaching in some parts to black, the adult male having large dermal fatty protuberances over the cheek bones, not found in the Sumatran species; the younger specimens, both in Borneo and Sumatra, are more ruddy brown.
In the immature specimens, which are the best known, the head is pear-shaped, expanding from the chin upward; the eyes close together; the external ears small; the nose confluent with the face, with nostrils but slightly elevated; mouth projecting, with large gape and very narrow lips; the abdomen protuberant; the hair on the forearm reversed. They are fond of low marshy regions, well wooded, their whole organization being fitted for progression on trees; they seldom move far on the ground, and then on all-fours or by swinging the body awkwardly forward between the arms supported by the bent knuckles; they build a kind of nest in trees, where they spend the night, leaving it late in the morning when the sun has dispersed the dew and thoroughly warmed the air; they do not live in society, except when a pair have a family in charge; the food consists of fruits, nuts, tender plants, leaves, and shoots, and is entirely vegetable in a state of nature; the natives say they always attack and are attacked by the crocodilo (C. biporcatus). In captivity the disposition is mild and affectionate, and the deportment grave and often melancholy; the intelligence and powers of imitation are considerable, and they get to be fond of the varied food of man, and especially his drinks, as ardent spirits and coffee.
The Sumatran orang has been described as a distinct species, as P. Abelii or bicolor (Geoffr.); it is of large size and of a reddish brown color. A smaller and more anthropoid species in Borneo has been named P. morio by Owen; it is about 4 ft. high, and 6½ ft. between the ends of the outstretched arms; the ridges of the skull are rudimentary, passing from the external angle of the frontal bone, slightly converging but not meeting, and behind the coronal suture soon subsiding to the level of the skull; the canines are smaller, and are related to differences in the cranium; it may be, according to Owen, a now permanent, though dwarfed, variety of P. satyrus.
Orang-outang (Pithecus satyrus).