250 TUBERCULOSIS 



corresponding modifications in the tissues of the human subject 

 what period of time is necessary for such a change we cannot 

 say. It is thus possible that the cases from which the bovine 

 type has been obtained do not represent the full number where 

 infection from the ox has occurred. It is quite likely that 

 although the bovine bacilli are more virulent to the lower 

 animals than the human bacilli are, this does not also hold in the 

 case of the human subject. In fact the comparative chronicity 

 of the primary abdominal lesions in children in the first instance 

 would point rather to a low order of virulence towards the 

 human subject. We may also add that there are cases, notably 

 those of Ravenel, in which accidental inoculation of the human 

 subject with bovine tubercle has resulted in the production of 

 tuberculosis. 



2. Avian Tuberculosis. In the tubercular lesions in birds there 

 are found bacilli which correspond in their staining reactions 

 and in their morphological characters with those in mammals, 

 but differences are observed in cultures, and also on experimental 

 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 International 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. The following 

 points of difference may be noted : 



On glycerin agar and on serum, the growth of ..tubercle bacilli from 

 birds is more luxuriant, has a moister appearance (Fig. 84, 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 ap- 

 parently been the sputum of phthisical patients. Again, tubercle 

 bacilli cultivated from birds have not the same effect on inoculation 

 of mammals as ordinary tubercle bacilli have. When guinea-pigs are 

 inoculated subcutaneously they usually resist infection, though occa- 

 sionally 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).] 



