THE CELLOIDIN METHOD 
125 
The principal features of the method are as follows: Material is 
dehydrated in absolute alcohol; treated with ether-alcohol; infil¬ 
trated with celloidin; imbedded in celloidin; hardened in chloro¬ 
form or alcohol; after which it is cut, stained, and mounted. 
Eycleshymer, who brought the celloidin method to a high degree 
of efficiency, published in 1892 a short account, which may be sum¬ 
marized as follows: Put the celloidin tablet, or fragments, into a 
wide-mouthed bottle, and pour on enough ether-alcohol (equal parts 
ether and absolute alcohol) to cover the celloidin. Occasionally 
shake and add a little more ether-alcohol until the celloidin is all 
dissolved. The process may require several days. The solution 
should have the consistency of a very thick oil. Label this solu¬ 
tion Number 4. Solution Number 3 is made by mixing 2 parts of 
solution Number 4 with 1 part of ether-alcohol. Solution Number 2 
is made by mixing 2 parts of Number 3 with 1 part of ether-alcohol. 
Solution Number 1 consists of equal parts of ether and absolute 
alcohol. 
After dehydrating, the material is placed successively in solutions 
1, 2, 3, and 4. For an object 2 mm. square, 24 hours in each solu¬ 
tion is sufficient; for the brain of a cat, a week is not too long. 
A paper tray may be used for imbedding. Pour the object, with 
the thick solution, into the tray and harden in chloroform for 24 hours; 
then cut away the paper and place the block in 70 per cent alcohol 
for a few hours. The material may be left indefinitely in a mixture 
of equal parts of 95 per cent alcohol and glycerin. 
Before cutting, the object is mounted upon a block of wood. A 
block, suited to the microtome clamp, is dipped in ether-alcohol, 
which removes the air and insures a firmer mounting. Dip the end 
of the block of wood in solution Number 3, and the piece of celloidin 
containing the object in solution Number 1. Press the two firmly 
together, and place in chloroform until the joint becomes hardened. 
Set the blade of the microtome knife as obliquely as possible. 
Both the object and the knife should be kept flooded with 70 per cent 
alcohol, and the sections, as they are cut, should be transferred to 
70 per cent alcohol. 
Stain in Delafield’s haematoxylin for 5 to 30 minutes. Wash in 
water for about 5 minutes, and then decolorize in acid alcohol (2 to 5 
drops of hydrochloric acid to 100 c.c. of 70 per cent alcohol) until 
the stain is extracted from the celloidin, or at least until the celloidin 
