BACILLUS OF TUBERCULOSIS. 801 
mon and infectious among fowls. The bacilli them- 
selves grow more readily on artificial culture media 
and produce a more even and moist growth. The 
bacilli are more apt to show branching forms than the 
human. In rabbits they produce very similar lesions. 
They are probably from the same stock as the mamma- 
lian varieties; but it is not believed that they are any, 
and certainly not any great, factor in the production of 
human tuberculosis. 
Diagnosis. One of the most important results of the 
discovery of the tubercle bacillus relates to the practical 
diagnosis of tuberculosis. The staining peculiarities 
of this bacillus render it possible by the bacteriological 
examination of microscopical preparations to make an 
almost absolutely positive diagnosis in the majority of 
cases. A still more certain test in doubtful cases is 
the subcutaneous or intraperitoneal injection of guinea- 
pigs, which permits of the determination of the presence 
of numbers of bacilli so small as to escape detection by 
microscopical examination. . For the animal test, how- 
ever, time is required—at least three weeks, and, when 
the result is negative, several months—before any posi- 
tive conclusion can be reached, for when only a few ba- 
cilli are present tuberculosis develops slowly in animals. 
LABORATORY TECHNIQUE IN THE EXAMINATION 
FOR TUBERCLE BACILLI AND OTHER ASSO- 
CIATED BACTERIA. 
I. Microscopical Examination of Sputum for the Presence 
of Tubercle Bacilli. 
1. Collection of Material. The sputum should be col- 
lected in a clean bottle (two-ounce) with a wide mouth 
and a water-tight stopper, and the bottle labelled with 
