266 BACTERIOLOGY. 



if it is the smegma bacillus this will rob it of its 

 color. 



3. If it is still not decolorized it is either the lepra 

 or tubercle bacillus. 



The differential diagnosis between the last two 

 organisms is less satisfactory ; they both take on the 

 same stains and both retain them or give them up under 

 treatment with the same decolorizers. The results of 

 investigations, however, indicate differences in the rate 

 of staining and decolorization, and it is accepted by 

 many of those who have compared the two organisms 

 that the lepra bacillus takes up staining very much 

 more readily than does the tubercle bacillus, often 

 staining perfectly by an exposure of only a few minutes 

 to cold watery solutions of the dyes, but when once 

 stained it retains its color much more tenaciously when 

 acted upon by decolorizing agents than does the latter 

 organism. 



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 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 sputa and pathological fluids from 

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



