98 
Transactions of the 
[Monthly Microscopical 
Journal, Feb. 1, 1869. 
glass applied. After a time the varnisli hardens in the same 
way that the solution of balsam does. But the great objection to 
this most facile method is, that in the course of a few weeks untinted 
specimens, [mounted in this manner, become so very transparent 
that more than half their details are obliterated. If specimens be 
very deeply tinted, however, this method answers fairly well. I 
have found that specimens of liver mounted in this way are pre- 
served almost better than any other organ, though it does not 
answer at all well for sections of tubercle, since it renders the 
fibrous element here, as elsewhere, too uniformly transparent. 
This method might, however, prove very useful, occasionally, for the 
mounting of thick opaque sections, which require a good deal of 
clearing up, and also to some persons, perhaps, engaged in other 
kinds of investigation, who might be glad of a balsamic medium of 
this kind, possessing even greater powers of rendering objects 
transparent than Canada balsam itself. 
The methods hitherto mentioned are what I advise principally 
for the preservation of specimens which have been previously tinted 
and are principally applicable also for sections of organs. But 
many specimens, whether sections or mere fragmentary portions of 
tissue, we may not desire to tint, and these are, I think, best pre- 
served in a mixture of glycerine and carbolic acid, in the proportion 
of fifteen of the former to one of the latter. In the paper before 
alluded to, I recommended a mixture of these two ingredients with 
the view of correcting the tendency that glycerine alone has to 
render specimens too transparent or too granular after a time. But 
I now use much less of the carbolic acid than I then recommended, 
so that now also it is not so necessary that the specimens should be 
immersed in spirits of wine first ; they may be taken at once from 
water, and transferred to the glycerine and carbolic acid in which 
they are to be mounted, provided only that the excess of water be 
first removed by bringing a portion of the specimen for a moment 
in contact with blotting-paper. The natural appearance of thin 
sections is beautifully preserved in this way, only the sections must 
be thin, since preparations so mounted are not nearly so transparent 
as when in glycerine alone. 
Another method, which I have oftentimes adopted with great 
success, for the preservation of very delicate tissues, without the 
least loss of detail, is one for a knowledge of which I am indebted to 
Mr. Lockhart Clarke, at whose instigation I first tried it. This con- 
sists in mounting the specimen in a very weak aqueous solution of 
bichromate of potash — about one of the bichromate to 1000 parts 
of water. In using an aqueous medium, such as this, however, we 
are placed, as it were, at the mercy of the cement we employ. If 
this be not good, we may at the time when we most regret it, find 
a valuable specimen ruined, owing to some crack or imperfection in 
