VARIETIES OE TUBERCULOSIS 281 



always of the bovine type ; in fact this seems to be the prevalent 

 organism in animal tuberculosis (vide infra). I» 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. Pulmonary phthisis is 

 almost invariably caused by bacilli of the human type ; a few 

 cases have been recorded in which the bovine type has been 

 present, but these constitute less than 1 per cent, of the cases 

 investigated. 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 ; and more recent 

 observations have shown that glandular tuberculosis in children 

 under ten years of age is produced by bovine bacilli in more 

 than 70 per cent, of the cases. 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 byl<V. H. Park, the bovine bacillus was present in more 

 than 2~) per cent., the percentage being higher in the earlier 

 than in the later years of childhood ; and Eraser has found that 

 of seventy cases of tuberculosis of bones and joints in children 

 in Edinburgh, this was the type present in more than half. 

 This proportion is higher than that found by Eastwood and 

 F. Griffith and by A. Stanley Griffith, in a large number of cases 

 chiefly in England, namely, a little over 25 per cent. Fraser also 

 found 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. 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 Eoyal 



