PREPARATION OF EYE FOR HISTOLOGICAL EXAMINATION. 611 
surface to the celloidin. The most rapid method of fixing 
is to moisten the cork and the flat surface of celloidin with 
ether, and to firmly press the moistened surfaces against one 
another for five to ten minutes; the ether has then evaporated, 
and the celloidin firmly adheres to the cork. 
Another method is to smear some thick solution of celloidin 
over both surfaces, to press them together for fifteen to thirty 
minutes, and then to place them in alcohol for twenty-four hours. 
There are also other methods of securing the mass, with 
gelatine or with paraffin, but the two methods described are 
rather more simple. As regards the relative values of the 
three methods of section-cutting I think that for the prepara- 
tion of sections of small pieces of the eye the freezing 
method answers well, and has the merit of being very con- 
venient, but for the preparation of sections of pieces of any 
size the method of cutting under spirit is most suitable. 
When the sections have been prepared they may be stained 
or simply mounted ; they should always be manipulated between 
two pieces of tissue paper, since any rough usage causes dis- 
placements. They must be thoroughly dehydrated by long 
immersion in alcohol, and may be then cleared in one of three 
media: 
a. Oil of bergamot. 
b. Oil of cedar. 
c. Turpentine. 
Of these oil of bergamot acts the most rapidly and efficiently ; 
at times, however, samples of oil of bergamot are met with 
which will dissolve celloidin. 
Oil of cedar is very slow in its action; and turpentine often 
causes a disagreeable shrinkage. 
The sections should be mounted in balsam. 
I have obtained sections by the freezing method, which are 
fairly good histological specimens, and which will bear exami- 
nation with a high power; but by the other method I have 
rarely obtained sections which serve to illustrate more than 
the topographical anatomy of the eye—sections which may 
be examined with a half-inch objective—although, if the 
