5(10 



THE SENSORIAL FUNCTIONS. 



cavity for the reception and defence of this most 

 important organ. It is chiefly from the expan- 

 sion of the hemispheres, and the developement 

 of its convolutions, that the human brain derives 

 this great augmentation of size.* 



* This will be apparent from the vertical section of the human 

 brain, Fig. 461 ; where, as before, s is the spinal marrow ; m, 

 the medulla oblongata; c, the cerebellum, with the arbor vitm ; 

 T, the optic tubercles, or corpora quadrigemina, dwindled to a 

 very small size, compared with their bulk in fishes ; p, the 

 pineal gland, supposed by Des Cartes to be the seat of the soul ; 

 V, one of the lateral ventricles; q, the corpus callosum ; and 

 ir, H, H, the hemispheres. 



Several expedients have been proposed for estimating the 

 relative size of the brain in different tribes of animals, with a 

 view of deducing conclusions as to the constancy of the relation 

 which is presumed to exist between its greater magnitude and 

 the possession of higher intellectual faculties. The most cele- 

 brated is that devised by Camper, and which he termed the 

 facial angle, composed of two lines, one drawn in the direction 



