1885.] Microscopy. 829 
Transfer to a thin solution of celloidin, and allow it to remain 
for from one to three days, according to the size of the object. 
Imbed in a thicker solution of celloidin. This is best done as 
follows: A cylindrical cork of convenient 
diameter is selected; a strip of glazed paper 
wrapped round it tightly and fastened with a 
couple of pins as indicated in the figure. In 
the box thus formed the object is placed and 
the celloidin poured carefully over it. If neces- | 
sary the object can be secured in any position 
by pins. Bubbles will rise from the cork and 
interfere with the imbedding ; two precautions 
will essentially diminish this danger: 1. Pour 
in so much celloidin that it covers the object 
half an inch deep, giving an opportunity for 
the bubbles to rise above the tissue; 2. Before 
imbedding cover the end of the cork with a 
thin layer of celloidin, which is allowed to dry 
on completely. After the object is covered the 
cork is mounted on a lead sinker (see figure), 
and allowed to stand until a film has formed 
on the upper surface. It is then immersed in f 
alcohol of 82-85 per cent (stronger alcohol (HAIT 
attacks the celloidin) for one to three days, 1 | 
have found it best to allow plenty of time for Qj) 
the hardening after imbedding. 
The sections have to be cut under alcohol; we use Jung’s 
microtome with his largest knife, placed so as to cut with as much 
of the blade as possible; if the edge i is good, then the longer the 
draw the thinner the sections which can be made. While cutting 
the knife blade should have as much alcohol upon it as possible ; 
to secure this we use the dripping apparatus described below. 
The sections should be removed from the knife with a fine brush, 
to avoid all risk to the edge. For celloidin imbedding are 
needed : 
1. Mixture of ether and alcohol, equal parts. 
2. A thin solution of celloidin in (1). This should be syrupy 
mo still flow easily. 
3. A thick solution of celloidin in (1) of about the consistency 
of thick molasses. 
The usual mistake is to have the solution too thick. Quanti- 
tative directions cannot be given because the celloidin varies in 
weight according as it is more or less dried. 
` Celloidin is a purified gun cotton, manufactured by E. Scher- 
ring in Berlin, Germany. It may be obtained in Boston of the 
Prang Educational Co., and of the Educational Supply Co., in 
ounce boxes, at $1.25. It is a most valuable and important addition 
to the resources of the histologist, as it enables him to make thin 
