146 DONALDSON. [Vou. IX. 
of this series of observations it was planned to make through- 
out a series of determinations of the volume parallel to those 
for weight. For this purpose a special apparatus was devised 
and found to work with accuracy. As we do not propose to 
go into the detail of this subject, the apparatus need not be 
described at this time. 
The outcome of the observations was that the curve for 
volume ran parallel, or nearly so, with that for weight. 
In this connection but one detailed observation was made 
and this with the purpose of determining whether in specimens 
hardened in alcohol, changes of temperature between 10° C. 
and 30° C. continued for an hour, caused variations in the 
volume. No change in volume was found, whereas specimens 
hardened in bichromate of potash, at the normal temperature 
or below, and then placed at 37° C., for some days undergo a 
decided decrease in volume, accompanying the decrease in 
weight. 
Period of Maximum.—Just here something may be said 
concerning the attainment of the maximum increase or de- 
crease in weight. 
The terminal weight after long hardening by no means 
always represents the maximum departure from the normal. 
It appears that within the limits of our observations the higher 
temperature favors the early attainment of a maximum. That 
in those specimens that attain the maximum at an early date 
the return toward the normal is most marked. When we come 
to study the human brain we shall find that renewal of the 
solution of the bichromate of potash is often followed by a 
decided decrease in the weight and volume of the specimen. 
The materials on which the change in weight depends, are 
therefore capable of variations in reaction even after long 
immersion in the hardening fluid. 
Extraction of Solids by Alcohol. —¥rom this digression we 
return to the consideration of the action of alcohol on the 
solids of the specimen. We take the normal percentage of 
solids in the fresh encephalon to be 20.5%. We find that the 
alcohol employed for hardening contained 0.004 grms. of solids 
in each 100 c.c. of fluid. For our purposes this is insignificant. 
