CHAP. XXL] OY THE HUMAN BRAIN. 407 



might be met with between individuals of either race." 

 The relative number in the several parts was, however, 

 found to be different in some of the smaller lobes, and many 

 of the laminaB were also smaller and thinner. The slight 

 deficiency in weight of the Bushwoman's Cerebellum, 

 " depends essentially," according to Marshall, " not on the 

 absence of any parts or laminae, but on the narrowness of 

 these latter ; for they are obviously much finer than in 

 the European brain." On the whole, he considers that 

 " the Cerebellum in the Bush woman is very well developed, 

 and that, as an organ, it is far more completely evolved 

 than the Cerebrum." 



Significance of the High Convolutional Development 

 of the Human Cerebral Hemispheres. 



After the preceding description of the external configu- 

 ration of the Human Brain, and now that the differences 

 existing between it and that of the higher Apes have been 

 detailed, such questions as these may naturally present 

 themselves to the minds of many readers : What is the 

 precise significance of this more complex convolutional 

 development of the Human Cerebrum ? and what signi- 

 ficance is to be attached to the want of symmetrical 

 development in the corresponding Convolutions of its two 

 Hemispheres ? 



It has been previously pointed out that there are three 

 principal types of convolutional arrangement (1) that 

 of the Herbivora, (2) that met with among Carnivora and 

 Cetacea, and (3) that of Quadrumana and Man. We 

 have seen also that within each of these great groups, 

 the development of the Convolutions peculiar to particular 

 species has hitherto seemed to be dependent in the main 



