64 BOVINE TUBERCULOSIS AND OTHER CATTLE DISEASES. 



tubercle bacilli in the two branches of the disease was not 

 questioned. Then Theobald Smith pointed out certain differ- 

 ences in morphology, cultural characteristics and virulence 

 regarded as characteristic of the organism in man and bovines 

 (47, 48). That these differences are usually observed, is a 

 fact that has received very wide confirmation. 



I'iews of Koch. In 1901 (13) and 1902 (14), Koch very 

 carefully reviewed the grounds for the belief that bovine tuber- 

 culosis is transmitted to man, and reached the conclusion that 

 it is not worth while to combat bovine tuberculosis in the 

 interest of the public health. Koch's paper raised an extraor- 

 dinary storm of protest, and likewise stimulated the study of 

 the problem along lines suggested by his arguments. He 

 pointed out very clearly and conclusively the essential weak- 

 ness of the evidence frequently accepted as proof of the trans- 

 mission of tuberculosis to man. The very wide prevalence of 

 human tuberculosis makes it very difficult to establish the 

 absence of human infection in cases where cattle are suspected 

 as the source. He laid down certain conditions that mu,st be 

 satisfied before transmission would be admitted as proven, and 

 these dicta are so stringent that it would be very difficult to 

 find any case conforming to them. 



It has been observed by Koch that milk-borne tuberculosis 

 does not correspond to the other milk-borne diseases in the 

 matter of the sudden explosive occurrence of cases among 

 those consuming the milk. The known peculiarities of tuber- 

 culosis, such as its deliberate onset, and especially the concep- 

 tion of latency of infection introduced by von Behring (52), 

 rather impair the value of the point as an argument against 

 the transmission of tuberculosis by milk. 



Bovine tubercle bacilli in man. Koch pointed out that the 

 recognition of bovine and human types of tubercle bacilli gave 

 a sound basis for determining the source of the disease in 

 human cases. It is along this line that the most conclusive 

 evidence of the transmission of the disease has been obtained. 

 The literature shows between forty and fifty cases in which 

 bovine tubercle bacilli have been isolated from infants and 

 children. This was conceded in 1907 by Theobald Smith (49), 



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