168 



THE GENERAL ANATOMY OF GORILLA 



[sect, a 



Gorilla is contrasted with the Chimpanzee. The details are reserved 

 as more appropriate to the subject of the next chapter. Here we 



Fig. 109. Cranium of adult female Chimpanzee. (Mus. Anat. Cant.) 

 One-third of natural size. 



may repeat that the outstanding effects are (a) extension of 



surface, so as to provide for an increased 



mass of muscle : this extension is effected 



largely by the outgrowth of osseous ridges 



(Fig. 110); (b) excavations of the osseous 



tissue, to reduce the otherwise inevitable 



increase in weight: these are brought about 



by the activity of cells in the mucous 



lining of the nose. Reference must be 



made also to the phenomena presented by 



the brain. For this study it is necessary 



to compare the appearances revealed by 



the skulls in section. This subject also is pjg. no. skull of an 



reserved for Chapter v. It will suffice to adult male Gorilla with an 



r . . unusually high sagittal ridge 



state here that nothing is more impressive or crest. (From a specimen 



,i r* - n j.1 i-i. n i. c in the Museum at Le Havre, 



in the Gorilla than the small amount of Normandv ) 



brain-growth after infancy, and this point 



will be discussed further in the place indicated (Fig. 158). 



A systematic description of a skull of the Gorilla in the adolescent stage 

 will now be given, and for this purpose the following divisions are convenient. 



A. The true cranial part, consisting of the bones (developed mostly in 

 membrane) which protect the cerebral hemispheres. 



