86 THE GROWTH OF THE BRAIN. 



tities of fluid. When the brain is weighed with the 

 ventricles unopened the fluid there present is included, 

 and contributes to the final figure. In the examination 

 of healthy brains the development of all these non- 

 nervous factors, the fluids, membranes, and vessels, is 

 either assumed as proportional in the several brains 

 compared, or more rarely some effort is made to exclude 

 them from the result by treating them separately. The 

 dura weighed 40 and 42 grammes in the two cases, a 

 woman and a man, in which E. Bischoff tested it. 1 

 Giacomini 2 found under ordinary circumstances that 

 the weight of the pia and residual fluid was from 5 to 

 5 '5 per cent, of the total weight of the hemispheres, 

 these in turn being but 87*2 per cent, of the entire 

 encephalon. If the vessels were congested the propor- 

 tion might rise to 6'5 per cent. The most complete 

 observations on the absolute weight of the pial mem- 

 branes is furnished by Broca. 3 He found that the pia 

 was heavier in the male than in the female, and that its 

 weight increased with age. When the subjects obtained 

 from a hospital for the insane, like the Bicetre, were 

 compared in this respect with those from the general 

 hospitals, the pia was found to be heavier in the case 

 of the insane. His table for the males is as follows : 



TABLE 9. SHOWING THE WEIGHT OF THE PIA MALES. 

 (Broca.} 



20-30 years 45 grammes. 



31-40 ... ... 50 



60- 60 



The variations ranged between 38 and 130 grammes, 



1 Bischoff, Zcitschr.f. rationclle Med., 1863. 



- Giacomini, Guidaallo studio dell' circonvoluzioni cerebrali delV 

 uomo, Torino, 1884. 



3 Broca, quoted by Topinard, Elements d? Anthropologie gene- 

 rale, 1885. 



