Page:Encyclopædia Britannica, Ninth Edition, v. 2.djvu/171

Rh SKELETON.] APE 157 body which is the main support in the sitting posture. These naked spaces increase in size as we descend through the series of Cynopithedna;, and are subject to a tumefaction (sometimes excessive and extending to parts adjacent) at the season of sexual excitement. Such naked spaces are never found in any of the Celidce. No ape has so exclu sive and preponderating a development of hair on the head and face as exists in most men. As to the head, long hair is found thereon in Hapale cedipus and in some of the Semnopitheci, whilst certain of the Macaci (as, e.g., the Chinese bonnet monkey, M. sinicus) have the hair of the head long, and radiating in all directions from a central point on the sinciput. A beard is developed in the male orang, and Cercopithecu-s Diana has long hair on the cheeks and chin. The wanderoo (Macacus silenus) has the face encircled by a kind of mane of very long hairs, and many of the marmosets have a long tuft of hairs on each side of the head. The American apes exhibit some extremes respecting hair development. Thus in some of the howlers (as in some of the Colobi of the Old World) the hair of the flanks is greatly elongated. Some also have an elongated beard, but the latter structure attains its maximum of development in the couxio (Pitheda satanas). Some of Pithedince have the hair of the whole body and tail very long, others have the head of the female furnished with elongated hair, while another species (Brachyurus calvus) has the head bald. Long hair may be developed from the shoulders, as in Cynocephahts hamadryas and Hapale humeralifer; or may form a tuft at the end of the tail, as in Macacus silenus, Cynoceplialus hamadryas, and Cynocephalus gelada. The direction of the hair may sometimes vary in nearly allied forms. Thus the hairs on the arm and forearm respectively may be so directed that the apices converge towards the elbow. Such is the case in most of the lati- sternal apes, yet in Hylobates agilis all the hair of both these limb segments is directed towards the wrist. The hair presents generally no remarkable character as to its structure. It may, however, assume a very silky nature, as in Hapale rosalia, or assume the character of wool, as in Eriodes, and as in that remarkable form recently discovered by Father David, Macacus thibetanus. The last named species inhabits the snowy ranges of the Thibet mountains, and is provided for this habitat by a modifica tion in its hairy clothing similar to that which suited the extinct mammoth for the severity of its Siberian home. This fact as to M. thibetanus has an interesting bearing on fossil forms, which we shall have to consider later. Great brilliance of colour is sometimes found in the naked parts of the body, particularly in the Simiadce, and especially in the regions of the face and sexual organs. In some of Cercojntheci and Cynocephali, rose colour, turquoise blue, green, golden yellow, and vermilion appear, in vari ous combinations, in one or other or both of these regions, and become especially brilliant at the epochs of sexual excitement. THE SKELETON. The skeleton of apes generally, if we except the tail, consists of but few more bones than that of man. The proportions of its parts, except as regards the relative length of the limb bones, are also much as in man; nor are their shapes, except those of the jaws and haunch bones, greatly different. The same general resemblance may be predicated of their minute structure, though the osseous tissue is generally rather dense, and the medullary cavity in the long bones small The Axial Skeleton. The Skull. The axial skeleton consists of the skull and the verte bral column, and the general shape of its more anterior portion, tho skull, has already been indicated when speak ing of the head as part of the external form. It is scarcely ever so evenly balanced on the occipital condyles as in man. The artificial division of the skull into a cranial and a facial portion may be here conveniently adopted from human anatomy. The proportion of the latter portion to the former varies greatly from age and sex, owing mainly to the differences produced through the development of large and powerful canine teeth in the adult males of most species. This proportion also varies in an irregular manner as we descend (through the series of apes) from those which are most like man. Thus the facial part is already very large in the orang and chimpanzee, much more so than in Semnopitliecus, where most of the ape cranial characters are moderately developed, or even than in many Cercopitlied; but it attains its maximum of rela tive size in the Cynocephali, above all in C. porcarius. In the Cebidce the facial part is relatively smaller than in the Simiada?, with the exception of Mycetes, while in Chryso- thrix the facial portion of the skull is relatively smaller than even in man himself. The relation of the face to the cranium (or brain case) is best shown by the cranio- facial angle, which is estimated by means of two lines, one drawn parallel to the base of the skull (from the front margin of the occipital foramen to the anterior end of the Fio. 14. Side view and base of the skull of tlie Douc (Semnopithecut nemctwi). From De Blainville. cerebral surface of the presphenoid), the other drawn from the front end of that base to the middle of the lower margin of the upper jaw. No ape, especially no ape of the Old World, presents so elevated and rounded a contour in the frontal region as does man. It is in American forms, especially in the genus Pitheda, that we find the greatest resemblance to man in this respect ; but the skull is lofty in the orang. The convexity of the occiput is well marked in Simia, Troglodytes niger, and Hylobates, while in the inferior Simiada? it is flat. Its maximum of production, however, is met with in the genus Chry$o1hrix.