TAXONOMY 
181 
and are called “Gram negative;” others retain the color and are 
called “Gram positive.” Examples of the latter are B. diphtheriae, 
Bacillus anthracis, and Bacillus tetani. 
Stains. — One of the most useful bacteriologic stains is Ziehl's 
Carbol Fuchsin, prepared as follows: 
Fuchsin (basic), i. 
Absolute Alcohol, i. 
Carbolic Acid (5 per cent, aqueous solution), 100. 
The fuchsin should be dissolved first in the alcohol and then the 
two fluids mixed. 
Ehrlich’s Anilin Water Gentian Violet. — Anilin Oil Water, 75 
parts. 
Sat. Sol. Gentian Violet in Alcohol, 25 parts. 
Anilin oil water is made by adding 2 mils anilin to 98 mils distilled 
water; shake violently. Filter through filter paper several times. 
Loffler’s Methylene-blue. — 
Sat. sol. Methylene-blue in Alcohol 30 mils 
Sol. KOH in distilled water (1:10,000) 100 mils 
Mix the solutions. 
Stain for “Acid Proof” Bacteria Including B. Tuberculosis. — 
1. Flood the cover glass with Ziehl’s carbol fuchsin and boil over 
the flame for thirty seconds. 
2. Wash and decolorize with a 2 per cent, solution of HC1 in 
80 to 95 per cent, alcohol until the thinner portions of the film 
show no red color. 
3. Wash in water. 
4. Counter stain for contrast with Lofiler’s Methylene-blue. 
5. Wash and examine. 
Van Ermengem’s Flagella Stain. — 1. Mordant: 
Osmic acid (2 per cent, aqueous solution) 50 
Tannin (10 to 25 per cent, in water) 100 
Four drops of glacial acetic acid may be added to this. 
2. Silver Bath: 
Dissolve 0.25 to 0.5 per cent, nitrate of silver in distilled water in a 
clean bottle. 
