Il8 THE GROWTH OF THE BRAIN. 



In the preceding paragraphs it has been the value of 

 the relative figures within a single series of observations 

 that has been under discussion, but when from the 

 cranial capacity the attempt is made to deduce the size 

 of an individual brain, the usual difficulties appear. 

 The authors are fairly well agreed that the relations of 

 the brain to the cranial cavity vary with age, sex, and 

 cause of death. The brain appears more nearly to fill 

 the cranial cavity in the young than in the adult ; in old 

 age there is an increasing diminution in both weight 

 and volume. In females it more nearly fills the cranial 

 cavity than in the males, and direct observation shows 

 that its volume may be less than that of the cranial 

 cavity by from 7 to 33 per cent, of the latter. Manou- 

 vrier found that sex being neglected, the brains which 

 he x examined were about 16 per cent, less in volume 

 than the cranial cavity ; but the observations were made 

 on dried skulls, and these compared with fresh brains, 

 no correction having been made for the shrinkage of the 

 skulls. This shrinkage, due to drying, would appear 

 from certain figures published by Bischoff to reduce the 

 cranial capacity from I to 2 per cent. Despite these 

 data, when the cranial capacity of a single skull is alone 

 given, it is possible only with much uncertainty to 

 deduce the size of the particular brain which filled it. 

 On the capacity of the skull according to age, a few 

 observations have been recorded by Broca. At any 

 given time it must always have a capacity somewhat 

 greater than the volume of the brain, but whether the 

 relations of growth are such that an enlargement of the 

 skull is, followed by the enlargement of the brain, or 

 whether they grow simultaneously, has yet to be 

 determined. 



1 Manouvrier, Sitr F interpretation de la quantity dans 

 phale, &c., Paris, 1885. 



