284 BACTERIOLOGY. 



According to Baumgarten, the lepra bacillus is stained 

 by an exposure of six to seven minutes to a cold, satu- 

 rated watery solution of fuchsin, and retains the stain 

 when subsequently treated with acid alcohol (nitric acid, 

 1 part; alcohol, 10 parts). By similar treatment for 

 the same length of time the bacillus tuberculosis does 

 not ordinarily become stained. 



These points, particularly what has been said with 

 reference to the smegma bacillus and the bacillus of 

 syphilis, are of much practical importance and should 

 always be borne in mind in connection with microscopic 

 examination of materials to which these organisms are 

 liable to gain access. It is hardly necessary to say that in 

 the examination of sputum and pathological fluids from 

 other parts of the body, the tubercle bacillus is, of the four 

 organisms, always the one most commonly encountered. 



TUBERCULIN. The filtered products of growth from 

 old fluid cultures of the tubercle bacillus represent what 

 is known as tuberculin a group of proteid substances 

 possessing most interesting properties. When injected 

 subcutaneously into healthy subjects, tuberculin has no 

 effect, but when introduced into the body of the tuber- 

 culous person or animal, a prouounced systemic reaction 

 results, consisting of sudden but temporary elevation of 

 temperature, with, at the same time, the occurrence of 

 marked hyperaBmia round about the tuberculous focus, a 

 change histologically analogous to that seen in the 

 primary stages of acute inflammation. This zone of 

 hypersemia, with the coincident exudation and infiltra- 

 tion of cellular elements, probably aids in the isolation 

 or casting off of the tuberculous nodule, the inflamma- 

 tory zone forming, so to speak, a line of demarcation 

 between the diseased and healthy tissue. 



