484 IOWA DEPARTMENT OF AGRICULTURE 
bacilli which for some unknown reason, are increasing in virulence and ap- 
proaching 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 finding of the German commission, instead of sup- 
porting Koch's views that we can decide with certainty by the inocula- 
tion 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 four of the human cultures caused gener- 
alized tuberculosis in cattle; but Kossel suggests that it might be possible 
that the bacilli in cases of human tuberculosis under certain circum- 
stances could likewise attain a very high pathogenic activitity for cattle 
without being for that reason bovine bacilli. Undoubtedly the German 
commission is confronting the two horns of the dilemma, either one of 
v/hich is fatal to the views of Koch as stated with sucn positiveness at 
London. If v»'e 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 en- 
tire experimeptal 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 89 cases of human tuberculosis tested, four, or over 10 per cent, were 
virulent for cattle and would be classified as of bovine origin; but these 
four cases were all found among sixteen 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 experiment* 
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 Biochmic Division, Bureau of Animal Industry, has 
isolated nine cultures from human tuberculosis. Two of these were de- 
rived from human sputum, three from cases of generalized tuberculosis 
in adults, and four from cases of generalized tuberculosis in children. 
By comparing these cultures with a newly isolated virulent culture of 
bovine tuberculosis, there were found among them two cultures from 
children which were identical in their cultural and morphological char- 
acters with the bovine bacillus. These cultures also killed rabbits and 
guinea pigs in as short a time as did the bovine bacillus. Hogs which 
were inoculated subcutaneously with these two cultures from children 
died of generalized tuberculosis. Two calves weighing over 300 pounds 
each v.ere inoculated subcutaneously with these virulent human cultures, 
and as a result developed generalized tuberculosis. A yearling heifer 
inoculated with one of the cultures showed generalized tuberculosis when 
killed three months after inoculation. Both the cattle and the hogs had 
