148 Instinct and Intelligence 



in man is covered by the posterior part of the 

 third frontal convolution, was, in the case of this 

 idiot, exposed. It is unnecessary for us to enter 

 into a further anatomical description of this 

 brain, which has been elsewhere fully described. 

 But we may observe, that the form and size of 

 this idiot's brain differs less from that of the 

 brain of an anthropoid ape, than it does from 

 the cerebrum of a normal adult European. We 

 may go beyond this, and state that the brain of 

 this individual was more nearly allied struc- 

 turally to that of an adult male chimpanzee than 

 to that of an average human cerebrum. 1 



Our object in drawing attention to the form 

 and dimensions of the skull and so of the brain 

 of anthropoid apes, as compared with that of 

 our human progenitors and existing races of 

 men, is in order to show that, with about the 

 same weight of body their intellectual capacities 

 have advanced in proportion to the increase in 

 the size of their cerebral hemispheres; for it is 

 owing to the growth of this part of their brain 

 that its bulk has advanced from that of a chim- 

 panzee of 600 to 1,500 c.c. This increase of 



1 Human Speech, by N. C. Macnamara, pp. 226-7. 



