THE COMBATING OF TUBERCULOSIS. 465 



body in the same way and thus originate other forms of tuberculosis. 

 This, however, is a considerably rarer case. The sputum of consump- 

 tive people, then, is to be regarded as the main source of the infection 

 of tuberculosis. On this point, I suppose, all are agreed. The question 

 now arises whether there are not other sources, too, copious enough to 

 demand consideration in the combating of tuberculosis. 



Great importance used to be attached to the hereditary transmission 

 of tuberculosis. Now, however, it has been demonstrated by thorough 

 investigation that, though hereditary tuberculosis is not absolutely non- 

 existent, it is nevertheless extremely rare, and we are at liberty in con- 

 sidering our practical measures to leave this form of origination entirely 

 out of account. But another possibility of tuberculous infection exists, 

 as is generally assumed, in the transmission of the germs of the disease 

 from tuberculous animals to man. This manner of infection is gener- 

 ally regarded nowadays as proved and as so frequent that it is even 

 looked upon by not a few as the most important, and the most rigorous 

 measures are demanded against it. In this Congress also the discussion 

 of the danger with which the tuberculosis of animals threatens man 

 will play an important part. Now, as my investigations have led me 

 to form an opinion deviating from that which is generally accepted, I 

 beg your permission, in consideration of the great importance of this 

 question, to discuss it a little more thorouglily. 



Genuine tuberculosis has hitherto been observed in almost all 

 domestic animals, and most frequently in poultry and cattle. The 

 tuberculosis of poultry, however, difEers so much from human tuber- 

 culosis that M^e may leave it out of account as a possible source of in- 

 fection for man. So, strictly speaking, the only kind of tuberculosis 

 remaining to be considered is the tuberculosis of cattle which, if really 

 transferable to man, would indeed have frequent opportunities of 

 infecting human beings through the drinking of the milk and the eat- 

 ing of the flesh of diseased animals. Even in my first circumstantial 

 publication on the etiology of tuberculosis I expressed myself regard- 

 ing the identity of human tuberculosis and bovine tuberculosis with 

 reserve. Proved facts which would have enabled me sharply to distin- 

 guish these two forms of the disease were not then at my disposal, but 

 sure proofs of their absolute identity were equally undiscoverable, and 

 I therefore had to leave this question undecided. In order to decide it 

 I have repeatedly resumed the investigations relating to it, but so long 

 as I experimented on small animals, such as rabbits and guinea pigs, 

 I failed to arrive at any satisfactory result, though indications which 

 rendered the difference of the two forms of tuberculosis probable were 

 not wanting. Not till the complaisance of the Ministry of Agricul- 

 ture enabled me to experiment on cattle, the only animals really suitable 

 for these investigations, did I arrive at absolutelv conclusive results. 



