No. £.] HARDENING REAGENTS. 161 
The comparison of the figures, Table 40, with those for the 
sheep, is to be made with due allowance for the fact that an 
average human encephalon contains from g00 to 1000 c.c. of 
fluid, and that when it is placed in 4000 c.c. of an 8% solution 
of bichromate of potash, the ultimate effect is to reduce the 
percentage of this solution 14%. This we know is a signifi- 
cant reduction, and greater than took place in the case of the 
sheep’s brain, since there the reduction in a solution ten times 
the weight of the specimen, is only about 0.6%. 
As matter of fact, the jars generally available in our labora- 
tories do not admit of adding more than five or six litres of 
fluid to an entire brain, and even less than this amount 
is ordinarily used; so that in the case of the human brain 
especially, the amount of fluid employed is of much signifi- 
cance, in determining the change in the weight of the specimen. 
This fact may account for the advice repeatedly given in the 
books to frequently change fluids, since this, for one thing, 
at least, keeps up the percentage of salts, 
TABLE 41.— Brain XVII. 
Female. Age, 40 years. Death from pneumonia. In hardening fluid 21 hours 
after death. 23% bichromate of potash plus one-sixth its volume of 95% 
alcohol. 
PERCENTAGE INCREASE. 
TimE — Days. ENCEPHALON. 
I 6.6 (c.) 
60 12.5 
73 (c.) 
309 12.6 
