VARIETIES OF TUBERCULOSIS 287 



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 ; in fact this seems to be the prevalent 

 organism in animal tuberculosis (vide infra). 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 that the bovine type was present in 50 per cent, of cases 

 of primary abdominal tuberculosis in children that is, in cases 

 where apparently infection had taken place by alimentation. 

 This proportion is, however, somewhat higher than what has 

 been obtained in other countries. In cases of lupus nearly half 

 of the bacilli obtained were of the bovine type, and it is an inter- 

 esting fact that almost all the viruses, both of the human and 

 bovine types, were markedly attenuated in their virulence for 

 animals. In over two hundred cases of tuberculosis in children, 

 given by W. H. Park, the bovine bacillus was present in more 

 than 25 per cent., the percentage being higher in the earlier 

 than in the later years of childhood ; and Fraser has recently 

 found that of seventy cases of tuberculosis of bones and joints 

 in children this was the type present in more than half. The 

 latter observer has also obtained the interesting result, that the 

 proportion of cases in which the bovine type is present is much 

 higher when there is no evidence of infection from other 

 members of the family, than when there is the possibility of such 

 infection. It is also to be noted that almost all the tubercular 

 lesions from which the bovine type has been obtained have 

 been in children, the presence of the bovine type of bacillus in 

 adult tubercular lesions, phthisical sputum, etc., being of very 

 rare occurrence. It is therefore justifiable to conclude that tuber- 

 culosis 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 occasionally met 

 with, though some of these on analysis have been found to be 

 really due to a mixture of the two types. According to some 

 observers, it is 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, but the more recent results, including those of the 

 Royal Commission, are that this modification does not take 



