96 
Transactions of the 
[Monthly Microscopical 
Journal, Feb. 1, 1869. 
one, thougli on the whole the best results have been obtained with 
Canada balsam. But as regards the solvents, it is much more 
important which one we select, as some of the solutions will keep 
well and even bear slight exposure to the air without undergoing 
change, whilst others will not. Although they have yielded fairly 
good results therefore, so far as the preservation of the tissues was 
concerned, I have now dismissed from use the solutions of the 
above-named resins in tetrachloride of carbon, ether, and chloroform, 
because all these solutions are more or less liable to become cloudy 
and granular in the stock bottles (owing to a molecular precipitation 
of the resin) after they have been kept for a certain time. Benzole 
and benzine are, however, much more stable products, and seem to 
undergo no change from moderate exposure to air or light — they 
simply evaporate — and accordingly I have found that solutions of 
gum-dammara or of Canada balsam in these keep clear and good 
for any length of time. Seeing also that the anatomical details 
of tissues are preserved at least as well in these as in the other 
solutions named, I now employ them only. I have not found 
any appreciable difference of result with benzole and benzine 
respectively; but as the former is a definite chemical product, 
and the latter a variable commercial article, I should recom- 
mend the employment of pure benzole. It will be seen, there- 
fore, that the solution to which on the whole I give the 
preference is one of Canada halsam in henzole, which should be 
prepared as follows : — Some Canada balsam must be carefully 
heated in a shallow pot for a certain time, so as to drive off as 
much as possible of the turpentine which it may contain, then it 
should be poured into a small bottle and sufficient benzole added 
for the solution of the balsam;* after all the balsam has been 
dissolved, the solution should be filtered through very thin filtering 
paper into a stoppered bottle, and so kept in store — what is re- 
quired for immediate use being poured into one of Highley's drop- 
bottles. 
Preparations may then be mounted in this solution in either 
of two ways : — 
1st Method. The section cut from a hardened organ is allowed 
to remain in a watch-glass with some spirits of wine for two or 
three minutes, then a drop of carbolic acidf having been placed upon 
the glass slip on which the specimen is to be mounted, the section 
is taken from the watch-glass on the tip of a small scalpel, its depen- 
dent edge brought into contact for a moment with a piece of clean 
* This should be done gradually so as to get nearly a saturated solution of 
balsam in benzole. If shaken a little from time to time, the solution will be com- 
plete in from thirty minutes to half-an-hour. 
t When procured from the chemist this is in the form of acicular crystals ; but 
the addition of a very few drops of water is sutficient to permanently liquefy three 
or four ounces of the acid. 
