Ture MIcRoscoPE. v i 
diffusely will it stain and the longer it takes for the completion 
of the process, as the higher grades of alcohol have less solvent 
powers than the lower. 
Cochineal.—This is the dried body a an insect, a bark 
louse (coccus cacti} which is very abundant in Central America. 
Only the female is of value, and to facilitate the extraction of 
the coloring matters, the amount used should be finely pulver- 
ized. 
MAYER’S COCHINEAL TINCTURE. 
a mee iv te oe See ae 8 to 10 grms. 
Alcohol, 50, 60 or 70 per cent.-----.----------- 100 ee. 
The cochineal in fine power is allowed to soak in the alcohol. 
for a week and the mixture then filtered, or the tincture may be 
made after the usual manner of percolation employed by phar- 
macists. The resulting solution is a clear deep red fluid which 
however, needs occasional filtering. It can be used whenevera 
simple alcoholic dye is required and with careful management 
produces very beautiful effects. To have the best success 
it is necessary to observe the following precautions: Before us- 
ing, the object should be placed for a short time in alcohol of 
the same percentage as that which was employed in making 
the solution, otherwise from the variety of substances in the 
dye and their different solubilities, there will be a precipitate. 
If the fluid is found too strong it may at any time be diluted 
with the same alcohol. After the staining, which requires from 
a few minutes for sections to a day or two for large objects, the 
surplus dye must be removed by immersion in alcohol of equiv- 
alent strength, until the specimen no longer yields any color. 
Over staining is removed by acid alcohol, (1-10 per cent. hydro- 
chloric or nitric acid, or one per cent. acetic or formic acid, and 
alcohol 70 per cent.) after which the specimen is again placed 
in pure alcohol. 
ALUM COCHINEAL. 
eM ing Sms wp ang os ease 1 to2 grms. 
ed arin mire gee eee | Gee, 
SOL OF WRLC?) Wj. ———— = — aoe pee 100 ce. 
The cochineal and alum are dissolved together in the me- 
dium selected, which is then evaporated down to 60 or 70 ce., 
and filtered. This solution stains the cell contents and wall 
and the inter-cellular substance as well as the nucleus. 
