IMMUNITY IN TUBERCULOSIS 233 



the diseased body of an alien species — man, for example — tends to dis- 

 credit the experimental transmutations referred to. 



Bovine tubercle bacilli are characterized, as ascertained by Smith, 

 by a greater degree of pathogenic power for mammals in general than 

 human bacilli, with which fact is correlated certain peculiarities of 

 cultural and physiological properties serving further to separate the 

 bovine from the human bacilli. The bacilli of mammalian origin are, 

 perhaps, closely related and less removed from each other by the sum 

 of their properties than they are from the avian bacillus. With the 

 few exceptions mentioned all forms of mammalian tuberculosis are 

 caused by either the human or the bovine bacillus. 



In view of the general fact that the bovine bacilli show a greater 

 degree of pathogenic action for the lower mammals than the human 

 bacilli, it was natural to assume that bovine bacilli would be powerfully 

 pathogenic for man also. To test this probability directly by experi- 

 ment is, of course, not permissible. But the belief that tuberculosis 

 in cattle is a menace to man is expressed in the many regulations by 

 which it is aimed to control and prevent the use as food of products 

 derived from tuberculous animals. It was not until Koch's address 

 was delivered in 1901 that any serious doubt existed in the minds of 

 sanitarians and pathologists that tuberculous cattle offered a source of 

 danger to man. The specific knowledge which has accumulated since 

 that date has served to establish the transmissibility in some degree 

 of bovine tuberculosis to the human subject. The inherent difficulty 

 and tediousness of the investigation of the specific types of tubercle 

 bacilli existing in human cases of tuberculosis necessarily limit the total 

 number of instances in which it has been established, beyond perad- 

 venture, that the bovine type of bacillus does occur in tuberculous 

 processes in man. In this country the responsibility of refuting the 

 too general statement of Koch has fallen chiefly upon Bavenel and 

 Theobald Smith, whose admirable studies in this direction are of a 

 convincing nature. 



If we pause for a moment to consider upon what data Koch based 

 his statement of the independence and non-communicability of tuber- 

 culosis in cattle and man, we shall appreciate that, in so far as he dealt 

 with established fact and not hypothesis, he had long been anticipated. 

 That cattle are highly resistant to infection with tuberculous material 

 and tubercle cultures obtained from human subjects can be concluded 

 from the early experiments of Baumgarten, Sidney Martin, Frothing- 

 ham and Dinwiddie. The most conclusive evidence upon this subject 

 is contained in Theobald Smith's paper of 1898. in which he sum- 

 marizes his experiments by stating that " putting all the facts obtained 

 by experiments on cattle together, it would seem as though the sputum 

 bacillus can not gain lodgment in cattle through the ordinary channels." 



