1885.] Microscopy. 629 
will not crumble during the removal to the prepared slide, but 
also in the fact that sections successfully transferred to the slide 
are liable to have portions of the yolk granules loosened an 
ign over other portions of the sections during the removal of 
paraffine. While by the ordinary methods of mounting 
(Geisbrecht, Schallibaum) those elements of the section which lie 
on its under side, and therefore come in immediate contact with 
the fixative, are ‘safely held in place, it may happen that man 
from the upper surface are loosened and washed away, because the 
fixative does not penetrate the whole thickness of the section. 
This obstacle may be entirely avoided by the proper use of col- 
We are indebted to Mason,! so far as I am aware, for the first 
suggestion of the use of collodion in this connection. But the 
method employed by Mason has serious objections. A drop of 
collodion on the surface of a paraffine-imbedded preparation soft- 
ens the object to such an extent that cutting is a very slow pro- 
cess, and thin sections are not easily attainable. The thickness of 
the collodion film, moreover, interferes more or less with accurate 
study of the mounted object, even if the sections are inverted 
when applied to the slide. The gradual drying of the surface of 
the film also causes the section to roll into a hollow cylinder with 
its collodion surface innermost, so that the inversion of the sec-. 
tion becomes difficult if not altogether impossible. The consist- 
ency of the collodion to be used is stated by Mason, but this is of 
little value since even a short exposure to the atmosphere often 
repeated will quickly change the condition of the collodion in the 
bottle. 
- All these impediments—but for which the method, I believe, 
would have come into more general use—may be largely if not 
aeaea obviated by using a very small amount of a rather thin 
collod 
The Eaterted which serves me is: the collodion must dry almost 
instantly (within two or three seconds after being applied) without 
leaving a trace of glossiness on the surface of the paraffine? 
In this collodion process T use at present the following method: 
The object imbedded in paraffine in the ordinary way is 
placed in a receiver of a Thoma’s microtome and the 
cut away to within 1™™ to 2™™ of the object on four sides, 
1N. N. Mason, Use of rege ay in Cutting thin Sections of Soft Tissues, AMER. 
Nart., Vol. xrv, p. 825, Nov., 1880. 
2 Judging from the effects, I am inclined to think that by this method the collodion 
pene! eparation certain depth, fixing the parts in their natural relations 
isat paneda a feia 1At (am mph > bcp k re made sufficient- 
ly thin (e. g. 5) there is no curling, whereas with muc uch thicker sections, the super- 
cial portion of which alone contains in that case the collodion, there is often a ten- 
dency to roll. This I have poupat to the slight shrinkage in the upper or collo- 
dion-impregnated portion of the section. 
VOL, XIX.—NO, VI. 41 
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