148 DONALDSON. [Von. IX. 
regards the amount of restraint exerted on them by the sup- 
porting tissues, or that they differed as regards the propor- 
tion of substances particularly responsible by their swelling 
for the increase in weight, or in both these ways. In case 
it were the former, since the supporting structures are at 
the same time inelastic and shrinkable by alcohol, it might be 
assumed that the specimens which increase least in weight, 
under the action of the 2% solution of bichromate of potash, 
would be those which would decrease most under the action 
of strong alcohol, for the supporting tissues would resist the 
swelling by the bichromate and effect the contraction under 
alcohol. The experiment was made, six encephala being taken. 
The six right halves were put into 2400 c.c. of 2% bichromate 
of potash solution, the six left halves were put into 2400 c.c. of 
94.5% alcohol. At the end of 65 days those in bichromate of 
potash had gained, and those in alcohol had lost as follows :— 
TABLE 19. 
PERCENTAGE GAIN IN PERCENTAGE Loss IN 
PERCENTAGE OF SOLIDS 
SERIAL Bi. Pot. 2 PER CENT. ALCOHOL 94.5 PER CENT. 
FounpD IN 
NuMBER. 
CorRESPONDING HALVES. ALCOHOL SPECIMENS. 
ars 35.8 30-2 13.6 
2 2° 34-4 29.6 13.9 
Sh 4285) 33-5 29.5 13.4 
4 4 2.8 29.9 11-2 
5 x 32-7 28.8 12.9 
6 6 32-4 27.7 14.9 
It is evident from this table that while the correspondence 
is not complete in detail, yet there is a correspondence of 
such a nature that those specimens which increase most in 
bichromate of potash also decrease most in alcohol. 
This suggests that there is a simple explanation for the 
variations exhibited by the reactions of different specimens, 
but it also indicates that the hypothesis that the difference is 
due to the reaction of the supporting tissues alone, does not 
account for the facts. The explanation is by no means evident, 
since in the case of the alcohol specimens, those which have 
