DEVELOPMENT OF NERVE ELEMENTS. 173 



number of cell elements must be determined even before 

 birth, at a time when in other respects the individuals 

 are most similar. The provisional picture, therefore, to 

 be formed of the brains belonging to those races least 

 capable mentally is that of one in which the number of 

 cell elements is approximately similar to that in the 

 most capable races ; but many of these elements being 

 but partially developed, the organisation of the brain is 

 less perfect, though the size is not thereby greatly 

 reduced. 



4. What significance is to be attacJied to t/ie difference 

 in brain-weight existing between men and women ? 

 Keith I has shown that among monkeys the males 

 have the heavier brains. The fact that among mam- 

 mals generally the males are the larger and heavier, 

 renders it probable that this relation of the brain- 

 weight will be commonly found in this class. Whatever 

 inference is drawn, therefore, from this relation will have 

 an application far beyond the limits of the human species. 

 The encephalon in the two sexes has a nearly similar 

 specific gravity, and the development of its subdivisions 

 is in almost the same proportion. In every case, how- 

 ever, where average weights have been compared, the 

 male encephalon has been found to be heavier than that 

 of the female. At birth the encephalic weight is nearly 

 the same for the two sexes, and the greater part of the 

 differences found between them at maturity is developed 

 during the first seven years of life. In macrocephalic, 

 large, medium, small, and microcephalic brains the 

 weight relation between the sexes is similar, though 

 both the absolute and relative differences increase with 

 increasing weight, just as in the body-growth of the two 

 sexes. Yet the microcephalic brains are most instruc- 

 tive in this connection. A minimal amount of com- 

 1 Keith, Jonrn. of Anat. and Physio I .^ vol. xxix., 1895. 



