IO6 THE GROWTH OF THE BRAIN. 



the same weight of the brain persisting up to the onset 

 of old age (about fifty years), when there appears a loss 

 in weight, which becomes rapidly more evident, so that 

 the smaller brain-weight of the aged must represent a 

 percentage of loss in some instances quite large. For 

 comparison it would be of interest to know how the 

 cranial capacity of the extremely aged compared with 

 that of those in the prime of life, and also whether there 

 was possibly any correlation between longevity and the 

 initial weight of the brain, for it is conceivable that a 

 heavy brain, though developed late in life, may in itself 

 be unfavourable to length of years. From the curves it 

 is clear that the brain-weight for the females runs almost 

 from the start below that for the males, that the 

 difference increases during the period of most active 

 growth, and at the end of that time reaches nearly its 

 maximum. This difference is maintained throughout 

 life. 



Concerning the weight of the encephalon in males 

 and females at birth, a word more may be added. 

 Most of the older observers found at this period the 

 greater weight in the males. These figures of Vierordt 

 show a slight excess in favour of the females, and this 

 same occurs in other recent series. Of course the con- 

 dition of greatest importance in determining the weight 

 of the brain at birth is the size of the child, which can 

 vary, as we know, within wide limits. To the larger 

 and heavier children belong, on the average, the heavier 

 brains, and it will not be possible to clarify our ideas 

 concerning the weight of the brain at birth and the 

 influence of sex upon this weight until it is possible to 

 compare more accurately male and female children, and 

 to be sure that still-born children have not been in- 

 cluded in the record. The matter is more complicated, 

 and consequently more interesting, than at first sight 



