356 BA CTERIOLOG Y. 



be mistaken for it on morphological grounds also. 

 Furthermore, while not all the members of this group 

 are capable of causing disease, some of them are patho- 

 genic for the same animals that are susceptible to true 

 tubercular infection ; and these may produce in those 

 animals lesions which are distinguishable from genuine 

 tubercles only by their finer histological structure. A 

 few words concerning some of these varieties, with a 

 brief summary of their more important peculiarities, 

 may not be out of place. 



BACTERIUM LEPR^E. Between 1879 and 1881 there 

 was described by Hansen and by Neisser an organism, 

 a bacillus, that was constantly to be found in the nodules, 

 characteristic of leprosy. For this organism the name ba- 

 cillus leprse was suggested. Though very like bacterium 

 tuberculosis in both morphology and staining properties, 

 it is, however, a little shorter, thicker, and much less 

 homogeneously stained. Its presence in the tissues and 

 secretions is demonstrated by the same method as that 

 employed for detecting bacillus tuberculosis. In sec- 

 tions of leprous nodules, stained by the ordinary Koch- 

 Ehrlich process, the bacilli, crowded together in the 

 large so-called " lepra cells," are always to be seen in 

 great abundance. It is unlikely that bacillus Iepra3 has 

 ever been cultivated artificially, and the disease has cer- 

 tainly never been reproduced in animals by inoculation 

 with bits of the diseased tissue, so that nothing can be 

 said of the life-history of this organism. 



BACTERIUM SMEGMATIS. In 1885 Alvarez and 

 Tavel discovered in the fatty secretions about the gen- 

 italia an organism that suggested the bacterium of 

 tuberculosis. Their observation has been abundantly 

 confirmed by others, and the organism to which they 

 directed attention is now regarded as pretty commonly 



