276 TUBERCULOSIS 



cannot say. It is thus possible that the cases of human tuber- 

 culosis 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 re- 

 actions 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. 79, C), and, 

 moreover, takes place at a higher temperature, 43*5 C., than is the case 

 with mammalian 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 (Strauss, 

 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 inoculation of mammals as ordinary 

 tubercle bacilli have. 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 tuber- 

 culosis (Nocard).] 



There is, therefore, abundant evidence that the bacilli derived 



