549 
^ criticism to the effect that the inoculation of guinea pigs was not a 
: sufficient test to show that such bacilli are dangerous when they are 
; ingested, the following experiment was made: 
! Four hogs, weighing 125 pounds each, were tested with tuberculin 
I to make sure that they were free from tuberculosis, and then placed 
\ in four separate disinfected pens. Each hog was fed 1 ounce of 
i butter daily in addition to its other feed ; the butter was of the kind 
i used for the guinea-pig-inoculation tests; the feeding was continued 
j; thirty days. This butter consisted of several different lots, the 
I youngest of which was 90 days or 3 months old when it was fed to 
j the hogs. The amount of butter received daily by each hog was less 
i| than the average person of the same weight eats, and tlie total amount 
received by each hog was less than 2 pounds. 
I Several months after the feeding of butter was discontinued the 
!' hogs were killed and examined post mortem, and three of the four 
J were found to have contracted tuberculosis. 
I More direct evidence to prove that tuberculosis is contracted from 
I infected food, and more direct evidence to prove that tubercle bacilli 
I remain alive and virulent a quarter of a year in ordinary butter, 
I would be difficult to obtain. 
i In oleomargarine tubercle bacilli may also remain alive long periods 
j of time, probably as long as in butter, which it closely resembles in 
: general character. In cheese the germs are especially dangerous when 
I they occur in fresh products, like cottage cheese, but that even those 
I' cheeses which require some time to ripen are not wholly safe is shown 
i by the fact that Prof. F. C. Harrison proved that tubercle bacilli 
I may remain alive in Cheddar cheese, a standard American variety, 
I one hundred and four days.® 
We may conclude, as far as it is possible to test the vitality and 
virulence of tubercle bacilli from different sources and in different 
environments, that those from cattle are, as a rule, the most virulent, 
and that it seems to be clear that dairy products generally, and butter 
especially, supply an ideal medium for the preservation of both the 
life and virulence of tubercle bacilli. 
THE PROPORTION OF TUBERCULOUS COWS AMONG THOSE IN USE 
FOR DAIRY PURPOSES. 
General statistics from which we can determine the percentage of 
dairy cows affected with tuberculosis are not obtainable. In the Dis- 
trict of Columbia about IT per cent of the cows tested with tuberculin 
reacted, and in the State of Xew York the figure among those tested 
is about 30 per cent. It does not absolutely follow from this that the 
cattle of New York State are more commonly tuberculous than those 
“ United States Bureau of Animal Industry, Annual Report, 1902, p. 228. 
