CHANGES IN HUMAN CEREBELLUM WITH AGE 15 



stem. This gives, with but little error, the weight of the cere- 

 bellum alone. From this value I calculated the percentage 

 which the cerebellum is of the encephalon. There remains, how- 

 ever, the question as to the effect of fixation and preservation in 

 formahn on the relative weight of the parts of the brain. Ac- 

 cording to Donaldson ('94), bichromate changes sUghtly the rela- 

 tive weights of the parts of the encephalon, so it seems probable 

 that formalin may have a similar effect. I attempted to estimate 

 this effect in two ways. Fu'st, I weighed again ten of the brains 

 used by Mall and compared the changes in relative weight of 

 the parts. Five showed increases in relative weight of the cere- 

 bellum and stem amounting on an average to 0.2 per cent, that is 

 an increase from 11 per cent to 11.2 per cent, and five showed de- 

 creases in relative weight which averaged 0.4 per cent. The 

 maximum change in any case was a loss of 0.5 per cent. Second, 

 I plotted the percentage weights of the cerebellum on the per 

 cent losses in absolute weight of the encephalon to see whether 

 the group would give any consistent curve showing either loss or 

 gain in percentage weight of the cerebellum with loss in weight 

 of the encephalon. 



I did this both for the negro brains and for the white ones in- 

 cluded in Mali's study. The values for the white males gave a 

 uniformly rising curve indicating a gain in percentage weight of 

 the cerebellum with loss in weight of the encephalon; the values 

 for the negro males did not give a very good curve, but indicated 

 the same tendency as that for the white males; the values for 

 negro females were distributed in such a manner that it was im- 

 possible to draw a conclusion. 



The changes in the weight of the encephalon during fixation and 

 preservation depend, as Pfister has pointed out ('03), on its condi- 

 tion at the time of fixation, and as the condition of different brains 

 varies widely according to the nature and course of the disease 

 causing death, it is to be expected that a series of brains from a 

 general hospital will show the greatest possible variations in the 

 effects of the fixing fluid. This will apply not only to the encep- 

 halon as a whole, but also to the relations of its parts, though per- 

 haps to a less extent. It is consequently wise to use considerable 

 caution in interpreting results based on such material. 



THE JOURNAL OF COMPARATIVE NEUROLOGY, VOL. 32, NO. 1 



