VARIETIES OF TUBERCULOSIS 249 



Young, general tuberculosis has been produced by tubercle 

 bacilli from the human subject, but these results are exceptional). 

 Corresponding differences come out in the case of the rabbit ; in 

 fact, intravenous injection of suitable quantities in this animal is 

 the readiest method of distinguishing the two types an acute 

 tuberculosis resulting with the bovine, but not with the human 

 type. In guinea-pigs and monkeys a generalised tuberculosis may 

 result from subcutaneous injection of bacilli of the human type, 

 but in this case also the difference in favour of the greater viru- 

 lence of the bovine type is made out. With regard to the dis- 

 tribution of the two types of organisms, it may be stated that so 

 far as we know the bacillus obtained from bovine tuberculosis is 

 always of the bovine type, and the same may be said to be true 

 of tuberculosis in pigs ; in fact this seems to be the prevalent 

 organism in animal tuberculosis. In human tuberculosis the 

 bacilli in a large majority of the cases are of the human type ; 

 but on the other hand, in a certain proportion bacilli of the 

 bovine type are present, the bacilli when cultivated being 

 indistinguishable by any means at our disposal from those 

 obtained from bovine tuberculosis. The Royal Commission 

 found the bovine type in 14 out of 60 cases of human 

 tuberculosis a somewhat higher proportion than has been 

 obtained by most other investigators and in all of these, 

 with one exception, the bacilli were obtained either from caseous 

 cervical glands, or from the lesions of primary abdominal tubercu- 

 losis, that is from cases where there was evidence of infection by 

 alimentation. It is also to be noted that almost all the tuber- 

 cular lesions from which the bovine type has been obtained have 

 been in children. The general result accordingly is that bovine 

 tubercle bacilli are present in a certain proportion of cases of tuber- 

 culosis in young subjects, and that these are especially cases where 

 infection by the alimentary canal has occurred. It must thus 

 be held as established that tuberculosis is transmissible from 

 the ox to man, and that the milk of tubercular cows is a common 

 vehicle of transmission. 



Although most of the bacilli which have been cultivated 

 correspond to one of the two types, as above described, it is 

 also to be noted that intermediate varieties are met with. It 

 has also been found that the type characters of the bacillus are 

 not constant. Various observers have found it possible to 

 modify bacilli of the human type by passing them through the 

 bodies of certain animals, e.g. guinea-pigs, sheep, and goats, so 

 that they acquire the characters of bovine bacilli. In view 

 of these facts it is probable that bovine bacilli will undergo 



