36 STORRS AGRICULTURAL EXPERIMENT STATION. - 
bacilli, even in small numbers, such inoculation is sure to be 
followed by the disease. This method, of course, is slow. It 
requires several weeks to obtain results, and it is therefore of 
no use as a practical method of testing milk. It is, 
however, a method capable of giving valuable scientific 
results as to the general infectiousness of milk. It is such ex-~ 
periments with guinea pigs which have led to the conclusion 
that milk from only such cows as are suffering from udder 
tuberculosis is dangerous. Similar experiments have been 
made to test the infectiousness of mixed market milk of cities, 
with the result of showing that market milk is frequently, 
though by no means universally, infected with the tubercu- 
losis germs. 
Such experiments with guinea pigs are, however, open to 
very serious criticism, and various considerations lead us to 
doubt as to their value in indicating a danger to man in con- 
suming such milk. In the first place, it is very certain that 
the guinea pig is far more sensitive to tuberculosis than man. 
Indeed, the guinea pig appears to be more sensitive than any 
other animal yet discovered, and the fact that a guinea pig 
would succumb to tuberculosis if inoculated with milk, while © 
it indicates that tuberculosis bacilli are in the milk, does not 
at all indicate that such milk would be dangerous to man. 
Secondly, most of these experiments upon guinea pigs have 
been performed by inoculating the milk or butter into the ab- 
domen of the animal, and this is very properly pointed out as 
a very different thing from using the milk as food. The fact. 
that sensitive guinea pigs will frequently succumb to tuber- 
culosis if milk or butter is inoculated into their abdomen, while 
it does indicate that tubercle bacilli are frequently present in 
these dairy products, is far from indicating that such dairy 
products are likely to be of any danger to mankind when used 
as food. Some of the experiments with animals, indeed, have 
_ been performed by using the milk or butter as food, and these, 
of course, are more in accordance with the conditions in man- 
kind. Under these circumstances a considerably smaller pro- 
portion of the animals suffer from the disease, a fact which in- 
dicates, of course, that there is less danger when the tubercu- 
lous milk is used as food than when inoculated into the ab- 
domen. | 
A third series of facts has been recently discovered, which 
throws even greater doubt upon the whole series of experi- 
ments. It has been found that there is present in the milk a 
