No. 1.] HARDENING REAGENTS. 165 
this is probably the main reason for the smaller increase in 
bichromate of potash and the smaller decrease in alcohol. 
In closing this paper it need only be pointed out, that in 
the further handling of hardened tissues many reagents are 
employed which produce changes in the weight and volume ; 
and that before we can begin a number of investigations 
depending on the size and form of the elements, these changes 
must either be brought under control or eliminated. 
Literature. — Here and there in the older literature are 
many isolated observations on the disturbances caused in 
animal tissues by the action of reagents on them. In 1891 
we gave an account of the changes produced in some of the 
cranial nerves by the process of hardening and mounting (4), 
and while this present paper was preparing for the press, Mr. 
P. A. Fish has published his valuable observations on brain 
preservation (6). 
In addition we may call attention to the observations of 
Brunetti (2), Hofmeister (3), Sehrwald (1), Van Gieson (5), 
and Kaiserling and Germer (7). The above observations are 
directly in line with those by the authors last mentioned, 
although the technique and material employed in this investiga- 
tion is quite different from that used by them. 
UNIVERSITY OF CHICAGO, 
November 14, 1893. 
