No. f.] HARDENING REAGENTS. 145 
TABLE 17. 
Change of weight after 70 days. 
ALCOHOL. PERCENTAGE DECREASE, 
95% 34:2 
i: 33-4 
93% 32.0 
“ 33-2 
80% 20.3 
x 21.6 
70% 13.8 
s 14.8 
60% 9.8 
“cc 9.5 
50% 0.04 
: 0.05 
It is interesting to note, that in the case of the 50% alcohol 
the loss in weight recorded, is preceded by an increase in 
weight, z. ¢., a period during which the specimen is swollen. 
This increase lasts only a day or two and then gives place toa 
decrease. 
The cause of the decrease in weight is due to a decrease in 
the volume of the specimen accompanied by an extraction of 
the solids. For example, after 245 days, in 95.5% alcohol, 
specimen C., for which the figures are given in Table 16, had 
an absolute weight of 33.3 grms. and a volume of 37.8 c.c.; 
at this time it showed a loss of some 32% in weight. The 
volume of the specimens in alcohol is greater than the weight, 
while for the specimen in bichromate of potash, as for the 
fresh brain, the volume is less than the weight. To this 
condition, of course, the low specific gravity of the alcohol 
contributes. Considered as a sponge, the specimen holds 
absolutely less fluid in the alcohol, than when in its normal 
condition. The contained fluid is lighter, and further the 
alcohol according to its strength has extracted a larger or 
smaller proportion of solids. 
Volume.— Before discussing the extraction of solids by 
alcohol, we may briefly state some observations made on the 
volume of the brain in various stages of hardening, as we have 
already had occasion to allude to the matter. At the beginning 
