31 



The general appearance and proportion of tlie Chimpanzee, Mr. 

 Owen remarks, are unquestionably the most anthropoid that the 

 Quadrumanous order presents; but many marked and essential 

 differences are observable upon a close comparison. The skull of 

 the adult is of a narrow elongated ovate figure, slightly contracting 

 towards the anterior part, which is, as it were, truncated, from the 

 depth and direction of the symphysis of the lower jaw. Compared 

 with the rest of the body it is of small size, owing to the arrested 

 development of the cerebral portion, which, as in other Quadrumana, 

 is altogether posterior, the face sloping forwards in the adult ani- 

 mal, at an open angle, as in the Baboons. Its exterior surface is 

 devoid of the intermuscular frontal and sagittal crests which give 

 so strong a carnivorous character to the skull of the Orang. The 

 extent of the origin of the temporal muscles is, however, readily 

 traceable by a slightly elevated ridge of bone : it differs considerably 

 in the adult and in the foetal skulls, but exactly accords with the in- 

 crease in the power of mastication required for the due action of the 

 large permanent teeth. It is possible that the slight development of 

 the intermuscular crest may be a sexual character ; for in an adult 

 female cranium of the Orang, the crest was scarcely more prominent 

 than in the Chimpanzee : in the latter, however, its development is 

 less to be expected, in consequence of the smaller comparative size 

 of the canine teeth. The muscular impressions on the occipital re- 

 gion are also less strongly marked than in the Orang, in which the 

 occipital foramen is nearer the posterior plane and its position is 

 more oblique. There is a greater proportion of brain behind the 

 meatus auditorius externus in the Chimpanzee than in the Orang, and 

 this disproportion is much greater in the adult than in the young. 

 Considerable changes also take place in the relations of the meatus 

 auditorius with the glenoid cavity for the articulation of the lower 

 jaw, in consequence of the increased development of the maxillary 

 apparatus, while the cranium remains nearly stationary; and a pro- 

 cess, of which the rudiment is perceptible in the young animal, co- 

 extending in downward growth with the changed position of the 

 articulation, becomes interposed between the condyle and the meatus, 

 and affords a support against backward dislocation. In the cranium 

 of the negro, a similar process may be traced in a rudimental con- 

 dition, anterior to thejissura Glasei'i, as in the young Chimpanzee, 



The zygoma is proportionally weaker than in the Orang. But 

 the most remarkable characteristic of the skull of the Chimpanzee, 

 both in the young and adult states, is the large projecting supra- 

 orbital ridges, which being continued into each other across the 

 glabella, form a sort of barrier between the head and face. The 

 cranial sutures, which are obliterated in the adult Orang, syndac- 

 tylous Ape, and more or less in the Baboons, are for the most part 

 persistent in the Chimpanzee, as in the human subject. Enough of 

 the squamous suture remains to show that the anterior angle of the 

 temporal bone joins the frontal, and separates the parietal and sphe- 

 noid bones, as in the young. The condyloid processes are propor- 

 tionately smaller than in the human subject, and their articular sur- 



