366 'Journal of Cojnparative Neurology and Psychology. 



TABLE 9 — Continued. 



As the calculated, values of the weight of the brain vary in the 

 same sense as the body weights, it appears that from birth to 

 maturity the curves for the brain weight in the two sexes are 

 related to each other as are the body weights, and thus the brain 

 weights in the females between the ages of 14 and 52 days are heav- 

 ier than those in the males. This relation should be confirmed 

 by direct observation before any value is attached to it. On the 

 other hand, after the period of most rapid growth the brain weight 

 of the male is always the heavier, because at like ages the male 

 body weight exceeds that of the female. This portion of the 

 curves is therefore like that in man, and for the same reason. 



As previously pointed out, we consider the period of the rela- 

 tively rapid growth in the brain to cease when it reaches the point 

 where the further increase in weight is approximately in propor- 

 tion to the 7th root of the body weight. This occurs at about 70 

 days in the males, and 73 days in the females. 



In order to compare the amount of increase in the weight of the 

 brain between birth and maturity in man with that in the albino 

 rat, it is necessary to bring the data on man into the same form 

 as that for the rat. Taking as a basis the data compiled by Vier- 



