424 DISEASES OF CATTLE. -'-' " J ' " r 



and some of the human cultures did produce this form of the disease 

 in such animals. Moreover, while some of the human cultures caused 

 no disease at all, others led to the development of minute foci in the 

 prescapular glands, and still others to somewhat more marked disease 

 of these glands. There were, consequently, four degrees of virulence 

 noted in these 39 cultures of bacilli from human sources and three 

 degrees of virulence in the 7 cultures from animal sources. 



Now, if we accept the views of Koch as to the specific difference 

 between human and bovine tubercle bacilli, and that the human bacilli 

 produce only localized lesions in cattle, while bovine bacilli produce 

 generalized lesions in these animals, must we not conclude that the 

 one nonvirulent bovine culture was in reality of human origin, and 

 that the animal from which it was obtained had been infected from 

 man? This is a logical deduction, but reverses the dictum laid down 

 at London that human tuberculosis is not transmissible to cattle. 

 Again, how are we to explain the human cultures of medium virulence? 

 Are they human bacilli which, for some unknown reason, are increas- 

 ing in virulence and approaching the activity of the bovine bacillus? 

 Or are they really bovine bacilli which have multiplied in the human 

 body until their virulence has become attenuated? In whatever 

 manner these questions are decided it would seem that the findings of 

 the German commission, instead of supporting Koch's views that we 

 can decide with certainty by the inoculation of cattle as to the source 

 of any given bacillus, really show that this method of diagnosis is 

 extremely uncertain in the present condition of our knowledge. 



It is definitely admitted that 4 of the human cultures caused gen- 

 eralized tuberculosis in cattle; but Kossel suggests that it might be 

 possible that the bacilli in cases of human tuberculosis under certain 

 circumstances could likewise attain a very high pathogenic activity 

 for cattle without being for that reason bovine bacilli. Undoubtedly 

 the German commission is confronting the two horns of a dilemma, 

 either one of which is fatal to the views of Koch as stated with such 

 positiveness at London. If we accept this suggestion thrown out by 

 Kossel, we must conclude that Koch was wrong in his claim that 

 human tuberculosis can not be transmitted to cattle, and thus with 

 one blow we destroy the entire experimental support which he had for 

 his argument before the British Congress on Tuberculosis. And if, 

 on the other hand, we accept the conclusion which follows from the 

 principle laid down by Koch for the discrimination between human 

 and bovine bacilli, and which appears to be favored by Kossel, we 

 must admit that bovine tuberculosis is an extremely important factor 

 in the etiology of human tuberculosis. Of the 39 cases of human 

 tuberculosis tested, 4, or over 10 per cent, were virulent for cattle 

 and would be classified as of bovine origin; but these 4 cases were all 

 found among the 16 cases of tuberculosis in children which the com- 

 mission investigated; hence it is plain that 25 per cent of the cases 



