BOVINE AND HUMAN TUBERCLE BACILLI 235 



The human bacillus, as a rule, grows someAvhat more easily and 

 abundantly from the first, and will grow well on glycerine-agar in 

 sub-cultures made directly from the original growth on blood- 

 serum. All attempts to obtain a like result with the bovine 

 organisms have failed. In artificial culture the human bacillus 

 rapidly loses virulence. The bovine bacillus grows as a film on 

 blood-serum, whereas the human bacillus produces warty growths. 



The morphological distinctions tend to disappear also in the 

 tissues of susceptible animals. We may inoculate a typical bovine 

 culture, and in a short time obtain from the various organs long 

 and much beaded bacilli simulating the human variety (Hueppe). 



The most striking dissimilarity is, however, seen in the action 

 of the bacilli from the two sources on animals. By whatever 

 method of inoculation, the bovine bacillus, as a rule, possesses a 

 much greater pathogenic power than the human bacillus for all 

 animals on which it has been tried (Villemin), the only exceptions 

 being possibly those animals, like guinea-pigs, which are so 

 extremely susceptible to both types that it is difficult to draw any 

 distinction between them. 



Polymorphism. — Another matter which claims consideration in 

 connection with the biology of the tubercle bacillus is its own poly- 

 morphism. As this feature does not directly affect the relation of 

 the bacillus to milk, it will be unnecessary to do more than refer to 

 it in passing. A number of workers since 1882 have described aber- 

 rant forms, threads, filaments, branched forms, clubs, dumb-bell 

 shaped forms, diplococcal forms, etc. (Babes, Nocard, Metchnikoff, 

 Fischel, Bruns, Coppen -Jones, Friedrich, Schultze, Schweinitz, 

 Dorset, Moeller, Lubarsch, etc.). Recently it has been suggested 

 that these various forms may be different stages in a single life- 

 history, and that upon morphological grounds the tubercle bacillus 

 may be classified among the group of higher fungi like the actino- 

 myces. This latter parasite is able, like the tubercle parasite, to set 

 up specific inflammatory new growths of a granulomatous type. 



Pseudo-tuberculosis. — Another characteristic which makes 

 our knowledge of the biology of tubercle complex is that apper- 

 taining to what is generally called pseudo-tuberculosis. In 1899 

 the Pathological Society of London urged that this term should 

 be discarded, and it is admittedly an unsatisfactory term, especially 

 when applied to various pathological conditions bearing only a 

 semblance to the tuberculous process. On the other hand, it is 

 a term of convenience, if not suitability, to describe that group of 

 bacilli not identical with tubercle bacillus and not acid-fast, and 



