354 BACTERIOLOGY. 



they are, except experimentally, concerned in disease- 

 production or that they are of importance to either 

 human or animal pathology.^ 



In the microscopic examination, particularly of urine, 

 of secretions from about the anus, rectum, and genitalia, 

 and of butter, it is manifestly of importance to bear in 

 mind the existence of this confusing group, for it is in 

 such secretions and substances that they are most often 

 encountered. The smegma bacillus and the butter 

 bacillus are especially liable to lead one into error of 

 diagnosis. This is less apt to be the case with the com- 

 paratively rare lepra bacillus and the questionable 

 syphilis bacillus. 



Differential Diagnosis. — According to Hueppe, 

 the differential diagnosis between b. tuberculosis, b. syph- 

 ilidis, b. smegmatis, and b. leprse, depends upon the fol- 

 lowing reactions : when stained by the carbol-fuchsin 

 method commonly employed in staining the tubercle 

 bacillus the syphilis bacillus becomes almost instantly 

 decolorized by treatment with mineral acids, particularly 

 sulphuric acid, whereas the smegma bacillus resists such 

 treatment for a much longer time, and the lepra and 

 tubercle bacillus for a still longer time. On the other 

 hand, if decolorization is practised with alcohol, instead 

 of acids, the smegma bacillus is the first to lose its color. 

 The bacillus tuberculosis and the bacillus of leprosy are 

 conspicuously retentive of their color even after treat- 

 ment with both acids and alcohol. To differentiate, 

 then, between the four organisms he recommends the 

 following order of procedure, based on the above reac- 

 tions : 



'For the literature on "acid-proof" bacilli, see Cowie, Journal of 

 Experimental Medicine, 1900, vol. v. p. 205. 



