300 TUBERCULOSIS 
man from eating tuberculous flesh is therefore slight. Further, 
flesh is commonly cooked before it is eaten. Thorough cooking 
will destroy the bacteria, but even the moderate cooking which 
meat commonly receives is sufficient to destroy the bacteria upon 
its surface, although the heat does not extend to the interior. 
Inasmuch as flesh is rarely the seat of the tubercular infection, and 
accidental contamination with the butcher’s knife will be on its 
surface, cooking will almost always render it harmless, unless the 
infection is deep-seated. For these reasons the flesh of animals 
slightly infected with this disease need not be condemned as food. 
It is universally admitted that the actual danger from this source is 
very small and perhaps does not exist at all. 
Milk.—The problem of the use of milk from tuberculous 
animals is a more difficult one to settle. The milk of tuberculous 
cattle does not always contain the bacilli and it is an unsettled 
question whether it will ever contain them unless the disease be 
located in the udder. At all events, cows having tuberculous 
udders (somewhere about 1 per cent.) will produce milk infected 
with tuberculosis bacilli. That these bacilli are active and 
vigorous is proved by thousands of experiments which have shown 
that such milk is capable of producing tuberculosis in guinea- 
pigs. It is true that the bacilli do not multiply in milk, but milk 
from one cow can, by being mixed with other milk, infect a large 
amount. It is possible that such milk may be a danger to the 
public health. It has been abundantly shown that market milk 
frequently contains tubercle bacilli in sufficient quantity to 
produce an infection in guinea-pigs, and the same is true of market 
butter. All of these facts certainly indicate a possible danger to 
the public from this source. 
In regard to the extent of this danger there has been a wide 
difference of opinion. It has certainly been magnified by some. 
The danger is, beyond question, frequently overdrawn. It is 
sometimes doubted that mankind can ever acquire tuberculosis 
from this source. Experiment has shown that large numbers of 
the bacilli must be swallowed at once to produce infection even in 
