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 
to make sure that they were free from tuberculosis, and then placed 
in four separate disinfected pens. Each hog was fed 1 ounce of 
butter daily in addition to its other feed ; the butter was of the kind 
used for the guinea-pig-inoculation tests; the feeding was continued 
thirty days. This butter consisted of several different lots, the 
youngest of which was 90 days or 3 months old when it was fed to 
the hogs. The amount of butter received daily by each hog was less 
than the average person of the same weight eats, and the total amount 
received by each hog was less than 2 pounds. 
Several months after the feeding of butter w T as discontinued the 
hogs were killed and examined post mortem, and three of the four 
were found to have contracted tuberculosis. 
More direct evidence to prove that tuberculosis is contracted from 
infected food, and more direct evidence to prove that tubercle bacilli 
remain alive and virulent a quarter of a year in ordinary butter, 
would be difficult to obtain. 
In oleomargarine tubercle bacilli may also remain alive long periods 
of time, probably as long as in butter, which it closely resembles in 
general character. In cheese the germs are especially dangerous when 
they occur in fresh products, like cottage cheese, but that even those 
cheeses which require some time to ripen are not wholly safe is shown 
by the fact that Prof. F. C. Harrison proved that tubercle bacilli 
may remain alive in Cheddar cheese, a standard American variety, 
one hundred and four days. 0 
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 17 per cent of the cows tested with tuberculin 
reacted, and in the State of Yew York the figure among those tested 
is about 30 per cent. It does not absolutely follow from this that the 
cattle of Yew York State are more commonly tuberculous than those 
° United States Bureau of Animal Industry, Annual Report, 1902, p. 228. 
