244 TUBER C UL OSIS. 



differences are observed in cultures, and also on experi- 

 mental inoculation. These differences were first described 

 by Maffucci and by Rivolta, but special attention was 

 drawn to the subject by a paper read by Koch at the Inter- 

 national Medical Congress in 1890. Koch stated that he 

 had failed to change the one variety of tubercle bacillus 

 into the other, though he did not conclude therefrom that 

 they were quite distinct species. 



On glycerine agar and on serum, the growth of tubercle 

 bacilli from birds is more luxuriant, has a moister appear- 

 ance (Fig. 64, C), and, moreover, takes place at a higher 

 temperature, 43.5 C, than is the case with ordinary 

 tubercle bacilli. Experimental inoculation brings out even 

 more distinct differences. Tubercle bacilli derived from 

 the human subject, for example, when injected into birds, 

 usually fail to produce tuberculosis, whilst those of avian 

 origin very readily do so. Birds are also very susceptible 

 to the disease when fed with portions of the organs of 

 birds containing tubercle bacilli, but they can consume 

 enormous quantities of phthisical sputum without becoming 

 tubercular (Straus, Wurtz, Nocard). No doubt, on the 

 other hand, there are cases on record in which the source 

 of infection of a poultry -yard has apparently been the 

 sputum of phthisical patients. Again, tubercle bacilli 

 cultivated from birds have not the same effect on inocula- 

 tion of mammals, as ordinary tubercle bacilli. When 

 guinea-pigs are inoculated subcutaneously they usually 

 resist infection, though occasionally a fatal result follows. 

 In the latter case, usually no tubercles visible to the naked 

 eye are found, but numerous bacilli may be present in 

 internal organs, especially in the spleen, which is much 

 swollen. Further, intravenous injection even of large 

 quantities of avian tubercle bacilli, in the case of dogs, 

 leads to no effect, whereas ordinary tubercle bacilli produce 

 acute tuberculosis. [The rabbit, on the other hand, is 

 comparatively susceptible to avian tuberculosis (Nocard).] 



There is, therefore, abundant evidence that the bacilli 

 derived from the two classes of animals show important 



