144 DONALDSON. [Vou. IX. 
discussing the reactions of the human brain, too much weight 
should not be laid on the differences just noted. 
Though solutions of bichromate of potash are most frequently 
used in hardening the brain, yet alcohol also plays an important 
role, either alone or in connection with the bichromate of potash 
solution. Moreover a study of the action of alcohol may help 
us to understand the manner in which the change in weight 
occurs and the conditions influencing it. 
It will be best, therefore, to take up at this point the action 
of ethyl alcohol on the encephalon of a sheep. As before we 
take a typical specimen. 
TABLE 16. 
Hemiencephalon of a sheep in 500 c.c. of 95% Ethyl Alcohol. 
Time 1n Days. PERCENTAGE Loss. 
1.2 19.1 
GD 24.3 (c) 
3.8 31.8 
5:9 32:9 
6.9 33-9 
Se) 33:5 
62.0 34.2 
105.0 34.4 
198.0 36.2 
550.0 36.5 
636.0 36.3 
The great rapidity with which weight is at first lost, and 
the long period through which a slow loss continues, are 
both features of interest. The total loss in weight in this 
percentage of alcohol is almost equal to the total gain in the 
2% % solution of bichromate of potash. 
The whole method of preparation and weighing, as described 
for the specimens in the bichromate, was followed in the case 
of the observations with alcohol. Thus far we have used ethyl 
alcohol only. The percentage of the alcohol was always deter- 
mined by the Tralles scale. 
Percentage of Alcohol. —Under the action of alcohol the 
decrease in weight is less when the alcohols of the lower 
percentages are used. This is shown in the following 
table: — 
