610 - JAMES W. BARRETT. 
particularly indicated in hot weather, and when the mass of 
celloidin is very large. 
When the mass becomes tolerably firm it should be trans- 
ferred to a mixture of equal parts of commercial alcohol and 
water, in which the consolidation soon becomes complete. 
The time the mass must be left under the bell jar depends 
much on the temperature of the room, and varies from one to 
six days. 
The eye is now infiltrated with and firmly embedded in cel- 
loidin, and sections of it may be prepared. 
It is almost impossible to cut sections from the block of cel- 
loidin in this condition on account of its size, so the whole 
mass should be cut into slices about a quarter of an inch 
thick, and one of these pieces should be fixed in the micro- 
tome. If the division into slices be made before embedding 
the lens will be displaced. 
When the eyes are exceedingly large, and embedding is 
consequently difficult, I usually re-embed one of these slices, 
and so obtain a requisite degree of hardness. 
Sections may be cut in three ways: 
a. By the freezing microtome. 
b. By any “slide microtome,” such as Jung’s. 
c. By a microtome so arranged that the section may be 
cut under spirit. 
(a) The mass should be placed in water for from six to 
twenty-four hours, until the greater part of the spirit has 
been removed. It should then be dipped in gum for a 
moment, and may be frozen, the gum serving to attach it 
to the plate of the microtome. 
Sections may next be cut and should he floated off the knife 
into warm water. Ifall the spirit has been removed from the 
mass, the celloidin, when frozen, often becomes intensely hard 
and difficult to cut. This difficulty may readily be obviated 
by warming the knife in warm water before cutting the 
sections. 
(6 or c) The mass should be securely fixed to a cork-covered 
plate. This is always difficult to do unless there is one flat 
