INFECTIOUS DISEASES OF CATTLE. 441 



Again, how are we to explain the human cultures of medium viru- 

 lence ? Are they human bacilli which, for some unknown reason, are 

 increijsing 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 tliis 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 aceept the conclusion which follows fi'om 

 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 bo\'ine origin; but these 4 cases 

 were all found among the 16 cases of tuberculosis in children which 

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

 cases tested of tuberculosis in children would by Koch's method be 

 classified as of bovine origin. 



In the Bureau of Animal Industry two distinct lines of experiments 

 have been carried on, in order that one might serve as a check against 

 the other. There has been, however, no discrepancy in the results. 

 De Schweinitz, in the Biochemic Division. Bureau of Animal Indus- 

 try, isolated 9 cultures from human tuberculosis. Two of these 

 were derived from human sputum, 3 from cases of generalized tuber- 

 culosis in adults, and 4 from cases of generalized tuberculosis in chil- 

 dren. By comparing these cultures with a newly isolated virulent 

 culture of bovine tuberculosis, there were found among them 2 cul- 

 tures from children which were identical in their cultural and mor- 

 phological characters with the bovine bacillus. These cultures also 



