General bacteriology 
85 
solution, is spread thinly on a glass slide or a cover-slip, 
is allowed to dry in the air, is then rapidly passed several 
times through the flame of a Bunsen burner (this process 
fixes the preparation), and is now ready for staining. 
(Fig. 15.) 
Ordinary Stains (Gruebler’s or Merck’s) 
The stains used for bacteriologic purposes are anilin 
dyes, which are used as saturated solutions, either alco¬ 
holic or aqueous (in water). 
The most commonly used stains are: 
Methylene blue: aqueous saturated solution is 6.7 per cent. 
Methylene blue: alcoholic saturated solution is 7 per cent. 
Gentian violet: aqueous saturated solution is 1.5 per cent. 
Gentian violet: alcoholic saturated solution is 4.8 per cent. 
Fuchsin: aqueous saturated solution is 1.5 per cent. 
Fuchsin: alcoholic saturated solution is 3 per cent. 
The alcohol used here is understood to be 95 or 96 per 
cent alcohol. 
After the bacterial preparation has been fixed, any of 
the above-mentioned stains is poured on the slide, and 
is allowed to remain there for two to five minutes; most 
frequently methylene blue is used for routine examina¬ 
tions. The stain is then poured off the slide, the prepara¬ 
tion is washed in water, dried on filter paper, a small 
drop of cedar oil is placed on the cover-glass or slide, or, 
if the preparation is to be preserved, a drop of Canada 
balsam is to be put between the glass slide and the cover- 
glass, and a drop of cedar oil is then placed on the cover- 
glass; the preparation is then ready for microscopic ex¬ 
amination. ■ (Fig. 16.) 
No directions for the use of the microscope are given, 
