TRANSMISSION OF TUBERCULOSIS THROUGH MEAT AND MILK. 717 
man tubercle bacilli which have been made by Smith and Din- 
widdie they have compared the bacilli of human sputum with 
the bacilli of bovine tissues. 
I believe that we cannot make a fair comparison between 
tubercle bacilli from the human and the bovine source unless 
all the conditions on both sides are as nearly similar as possible. 
We cannot make a fair comparison between tubercle bacilli 
derived from human sputum and those derived from bovine 
tissues. Smith has found by comparative study of the bacilli 
from these two sources in cultures that those from human spu¬ 
tum are more saprophytic in growth than those from bovine 
tissues. It may be that the more saprophytic the bacillus is 
the less virulent it is, and that this will account for the fact that 
the bacillus from human sputum shows itself to be less virulent 
than that from bovine tissues. It appears that in order to carry 
on absolutely fair comparative researches it would be necessary 
to watch the cases on both sides for a considerable time to make 
out whether they are acute or chronic and then take the germs 
from tissues in the same part of the body of each, and from 
tissues which have undergone similar degeneration on account 
of the disease. Reliable work can be done only with cultures and 
not with tissues. The reasons for this are easily apparent. Un¬ 
til this is done it seems to me that but little can be done on this 
part of the subject which will warrant us in drawing conclusions. 
If experiments be made in the manner suggested it may be that 
the difference in virulence between human and bovine bacilli 
would not appear, and that they may be found to be of equal or 
nearly equal virulence. 
Inasmuch as Koch’s address before the British Congress on 
Tuberculosis 81 on July 23, 1901, has received so much attention 
and has been the occasion for so many unwarranted dicta, 
especially upon the part of those who oppose the doctrine of 
transmission of tuberculosis from animal to man, it is incumbent 
upon me to give it special notice here. First, I would notice a 
certain statement of his which has been the subject of most 
misinterpretation. Koch has made within the last two years 
