ELEMENTARY BACTERIOLOGY LABORATORY EXERCISES 15 
EXERCISE 22 
CAPSULE STAIN 
Make stained preparations of the cultures furnished. 
Procedure 
(1) Fix the slide. 
(2) Cover the film with glacial acetic acid for a few seconds. 
(3) Shake off the excess of the glacial acetic acid. 
(4) Add portions of the aniline-water gentian violet until all the acid is 
washed out. 
(5) Wash in a 2% solution of sodium chloride and mount in the same so 
lution. Do not let water come in contact with the film at any time. 
When this method of staining is successful, the bodies of the bacteria show 
a deep violet color and the capsules a lighter, pinkish purple color. 
Formulae 
; Aniline Water 
Aniline 1 part 
Distilled water. 9 parts 
Aniline-W ater Gentian Violet 
Aniline water 9 parts 
Gentian violet, saturated alcoholic solution 1 part 
EXERCISE 23 
CAPSULE STAIN: INDIA INK METHOD 
Another method for determining the presence of capsules on bacteria may 
be used. 
Procedure 
(1) Place a drop of India ink upon a microscopic slide. 
(2) Puta small amount of the culture to be examined into the drop of ink 
and spread it into a thin film. 
(3) Fix the slide. 
(4) Stain the preparation in the customary way by using the simple carbol- 
fuchsin or the Gram stain. 
(5) Observe and draw. 
When bacteria are stained by this method the bodies of the organisms are the 
color of the stain used and the capsules are unstained in a dark background. 
