BACILLUS OF TUBERCULOSIS. 301 



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 



