52 
Journal of the 
the slide carefully with a clean rag moistened with spirits of wine, 
and finished on the turn-table by sealing the cover with a ring of 
Brunswick black, or other varnish. 
Another aid to the thorough displacement of the acid is to use 
the balsam in as thick and pasty a condition as possible. At the 
same time this is not essential to success, as thin balsam works 
very well. Benzine* should be used in preference to turpentine 
to liquefy balsam that has become too stiff. Newly-purchased 
balsam is often very thin. In this case it is advisable to bake it 
in a cool oven for some days until it is hard enough to resist 
slight pressure, and then add about one-fourth part of benzine, 
placing the bottle in a hot-water bath, which will ensure perfect 
mixture. Balsam thus prepared will harden quickly, which it 
does not do if liquefied by turpentine. Turpentine may therefore 
be excluded from the microscopist’s laboratory. 
When mounting it is well to be provided with several pieces of 
blotting paper, about an inch square. These should be used, as 
above described, to aid the substitution of one liquid for another, 
particularly when displacing watery carbolic acid by pure acid. 
Vegetable tissues, such as plant leaves, sections of wood, &c., 
after washing in water may be drained and transferred at once to 
the slide, covered by thin glass, flooded in carbolic acid, and then 
boiled over the spirit-lamp, adding fresh acid from time to time 
until the object is perfectly clear. Air bubbles may thus be 
boiled out, and the object decolorised and rendered beautifully 
clear by the process. When cool, add fresh acid and follow with 
balsam, as above. 
Insects whole, or their organs, and animal tissues generally 
may be treated in the same way, which seems to suit such 
organisms better than the old method. The action of the acid 
under heat is rapid,t and can easily be stopped when required by 
simply blowing upon the cover. 
In preparing sertularians and polyzoa , where the empty cells 
retain air so pertinaciously, this annoyance may be overcome by 
* Some prefer chloroform, which will liquefy the balsam without heat, but 
we think the benzine much superior in subsequent operations. 
f As some objects are injured by heat, these may be cleared by soaking in 
cold carbolic acid for a few days or until cleared sufficiently. 
