BACTERIUM TUBERCULOSIS 79 
EXERCISE XXVIII 
BACTERIUM TUBERCULOSIS 
118. The tubercle bacterium does not grow readily on the 
ordinary media. For its cultivation blood serum, egg medium, 
glycerin agar, or bouillon containing from 5 to 7% glycerin is 
ordinarily used. Formerly it was with much difficulty that it 
was made to grow from lesions of tuberculous animals; but 
when a culture was once started it could, on the media men- 
tioned above and sometimes on agar, be cultivated in sub- 
cultures with comparative ease. More recently Dr. Theobald 
Smith has described a method which renders its cultivation 
from tuberculous lesions much easier (for details, see Part II, 
Diagnosis of Tuberculosis). It grows very slowly, and it is neces- 
sary that the temperature should be kept, without variation, at 
about 37°C. The avian variety grows much more readily on 
glycerin agar, egg medium, serum, and in glycerin bouillon. 
On account of these difficulties it is not practicable, in a general 
course, to cultivate this organism, but cultures on solid and 
liquid media will be furnished by the instructor for examination. 
It is important, however, to be able to recognize this organism 
_ in tissues and sputum, and consequently the following additional 
exercise in staining and studying it is given. 
119. Work for this exercise. Examine and carefully describe * 
the appearance of the cultures of the tubercle bacterium | 
(human or -bovine variety) on glycerin agar and in glycerin 
bouillon furnished. : 
VY Make 2 cover-glass preparations from the cultures furnished 
for that purpose and stain them with carbol fuchsin (§ 96). 
Make 4 cover-glass preparations from tuberculous sputum zich 
and stain for tubercle bacteria. It is often desirable to counter- 
stain the specimens from sputa. Stain two of them by Gabbett’s 
method and two with carbol fuchsin, and decolorize without 
