CHAP. IV] THE GENERAL ANATOMY OF GORILLA 191 



marked in the Lemurs. But so far as is known, Man possesses no 

 marked superiority over the Gorilla in this respect, and it is prob- 

 able that though the sense of hearing may be more acute in the 

 . ape, this does not greatly affect the comparison of the sense organs 

 considered as a whole. 



(c) Failure to provide an explanation by reference either to 

 (a) general or (b) special sensibility, leads to an investigation of 

 the motor mechanisms and more especially of the motor area of 

 the neo-pallium. And herein relevant evidence is encountered. 

 For the motor area of the neo-pallium exhibits a progressive 

 increase in extent, culminating in the human cerebrum. It is to 

 be noted, moreover, that this increased area marks an increase in 

 the variety and range of movements, rather than an accession of 

 strength. And the inferiority of even so highly developed an ape 

 as the Gorilla in respect of skilled movements, such as those of the 

 hands, confirms this assumption. Even more significant is the 

 human superiority in the skilled movements of the lips, tongue, 

 pharynx and laryngeal structures subservient to articulate lan- 

 guage. 



(d) The mysterious " association areas " of the neo-pallium 

 remain for examination. These areas (neither purely motor nor 

 sensory though in close touch with undoubted motor and sensory 

 areas) have been identified in all the Primates described in the fore- 

 going pages. In extent, they manifest a progressive development. 

 In the brain of the Gorilla this has reached the latest stage so 

 far known as antecedent to that found in Man. As a factor in 

 determining the superior size of the human brain, the increase 

 in the association areas is predominant over all others. The 

 increase in extent affects not only the areas themselves, but 

 certain outlying regions adjacent to them and to the areas of 

 general and special sensibility. 



A comparison of the brains of the Gorilla and Man may be 

 drawn from the inspection of Figs. 125 and 126, in which the more 

 important areas are indicated. In concluding this brief sketch of 

 cerebral anatomy, two remarks may be added. Thus the figures 

 just mentioned indicate a most suggestive relation between cer- 

 tain of the neo-pallial sulci and the margins or limits of some 



