INCREASE OF THE BRAIN IN WEIGHT. 109 



The fact that in Boyd's Table (20) the stem includes 

 more than the pons and bulb, prevents a direct com- 

 parison of the entries for the weight at birth with those 

 in Table 19. But both tables emphasise the great 

 development of the hemispheres at this time. 



Boyd's table further brings out the interesting fact 

 that there is comparatively small change in the per- 

 centage relationships after the period of rapid growth is 

 completed that is, after the twentieth year. The 

 failure of these proportional figures after the twentieth 

 year to exactly agree with those already given in 

 Table 14, is probably due to the fact that the time 

 intervals have been differently chosen. Indeed, a com- 

 parison of the two tables may serve to show, by reason 

 of the small amount of differences, how little influence 

 upon the proportional development is exerted by those 

 conditions which have so much effect on absolute 

 weight. It is further to be noted that in these latter 

 tables the proportional weight of the hemispheres is as 

 often superior in the female as it is inferior, hence we 

 must be very cautious about inferring the influence of 

 sex in this relation. 



Without giving special figures, Mies states that the 

 spinal cord in man increases in weight rapidly during 

 the first years of childhood, and more slowly later. He 

 further adds that it still continues to increase after the 

 brain has ceased to grow, and that its senile atrophy 

 begins at a later age than in the case of the brain. His 

 published observations show that in the new-born child 

 the weight oi the cord ranged from 2 to 6 grammes, 

 with a mean weight of 3-42 grammes. Table 19 shows 

 that Danielbekof found the weight of the spinal cord in 

 male children averaging in age one month 3*9 grammes, 

 and in the female 3*8 grammes. Comparing these with 

 Mies' figures for the weight in the adult (26 grammes) 



