No. 1.] HARDENING REAGENTS. 149 
lost most in weight are not those which have lost the greatest 
percentage of solids, so that the final weight of the alcohol 
specimens is the resultant of both shrinkage and extraction of 
solids, and it is not clear how these processes are related to 
each other. 
Effects of Bichromate of Potash.—¥rom all the foregoing 
observations we may conclude : — that the sheep’s brain, under 
the influence of solutions of bichromate of potash, increases in 
weight and volume ; that by far the greatest change is during 
the first 24 hours; that after the first two weeks the increase 
is slight and comparatively insignificant ; that after the maxi- 
mum weight is attained there may occur a slight decrease. 
The gain in weight is made greater by freshness, absence of 
pressure, and low percentage of salts in the solution, it is made 
less by a temperature of 38° C. The increase in weight is due 
to the taking up of the solution by the specimen. 
The fluid within the specimen at first contains a smaller 
percentage of the salt than is present in the surrounding 
fluid. 
The percentage of solids may be increased above the normal, 
by prolonged hardening in a solution of 2% or more of bichro- 
mate of potash. A temperature of 38° C. increases the per- 
centage of solids still further. 
Liffects of Alcohol.—The general action of alcohol is to 
decrease the weight and volume of the sheep’s brain. The 
rate at which this takes place is similar to that for the increase 
in bichromate of potash. 
The higher the percentage of alcohol, the more rapid and 
greater is the loss in weight. The loss in weight is due to the 
decrease in the volume of the specimen by shrinkage, extraction 
of solids and replacement of water by the alcohol of a less 
specific gravity. In the case of 50% and 60% alcohol, the final 
decrease in weight is slight, and is preceded by an increase. 
Strong alcohol decreases the percentage of solids. — So long 
as the exact time of death is not controlled, we shall be unable 
to determine how far the changes in weight in a given speci- 
men are due to changes dependent on post mortem alterations, 
and how far they represent ante-mortem conditions. 
