20 
PHARMACEUTICAL BOTANY 
signed for a cord or strap when it is desired to run the instrument 
by a motor. 
THE TECHNIQUE OF MAKING A TEMPORARY MOUNT 
1. Place a drop or two of water (or reagent) in the center of a clean 
glass slide. _ 
2. With the aid of a forceps take the section or very small quantity 
of the material to be examined and spread it on the drop of water. 
3. Place a clean cover-glass over the material. In placing the 
cover-glass do not drop it flat upon the drop of water, but place one 
side of it down first and allow it to squeeze the water along under it. 
4. Keep the top of the cover-glass dry. 
When filamentous algae or molds are to be examined, the material 
tends to cling together and must be carefully separated, in the drop 
of water, with dissection needles before the cover glass is placed over 
the material. In case a coarse ground drug is to be mounted the 
coarser particles should be first crushed in the water on the slide 
and subsequently teased apart with dissection needles. 
Care should’ always be taken to see that the water or mounting 
medium used is not contaminated with foreign substances. This 
can best be practiced by examining the mounting medium under the 
microscope before the material to be examined is placed in it. 
THE TECHNIQUE OF MAKING PERMANENT MOUNTS 
1. The Mounting Medium .—When a microscopic object is to be 
preserved permanently it must be kept from decaying and the fluid 
in which it is placed must be kept from evaporating. These condi¬ 
tions can be met by adding an antiseptic (2 per cent, acetic acid, or 
formaldehyde) to the water used in rfiounting and carefully sealing 
the cover glass with asphaltum or zinc white. As a rule, a better 
way is to use a mounting medium that will not evaporate, e.g ., 
glycerine, glycerin gelatin or Canada balsam. These fluids have 
a high refractive index and so render the objects penetrated by them 
more transparent. This quality is generally an advantage, but for 
objects already almost transparent it is quite the reverse. Glycerine 
has the disadvantage of always remaining soft, so that the mount 
may at any time be spoiled by careless handling. Glycerin-gelatin 
