CHAP. XXI.] OF THE HUMAN BRAIN. 899 



The latter is a point of considerable importance, and 

 not always sufficiently borne in mind by those who have 

 dwelt upon the large size of the Occipital Lobes in 

 many of the Quadrumana. If these parts seem to be 

 relatively smaller in Man, it must not be forgotten that in 

 Monkeys and in Apes their surfaces are smooth and com- 

 paratively unconvoluted, whilst in Man, in proportion to 

 their size, the area of superficial grey matter on the Occipital 

 Lobes becomes en- 

 ormously increased 

 by reason of the 

 number and depth 

 of their surface-fold- 

 ings. 



Thus we find in 

 the Brain of Man 

 not so much new 

 parts or regions, as 

 an enormous deve- 

 lopment of pre- 

 existing parts and 

 regions. Again, the 

 degree of such in- 

 creased development FIG. 146. Section through the left Occipital Lobe 



TO IVIT nr\ rvmnTia ^ a Human Brain ; showing the number and depth 

 J.o U V 1\J llltujilo - ., 



of its surface-foldings. 



every where the same. 



These are both of them facts of great significance from a 

 psychological point of view and especially from the 

 point of view of that Psychology which has its roots 

 in the general Philosophy of Evolution. 



One of the most notable peculiarities of the Human 

 Cerebrum is that, in various ways, its two Hemispheres are 

 not quite symmetrically developed. 



