278 TUBERCULOSIS. 
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 (some- 
where about i per cent.) will produce milk infected with tubercu- 
losis 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 
susceptible animals. The number of bacilli which a person will 
swallow with a drink of milk will commonly be rather small, and 
the human individual has a considerable power of resistance 
against the disease. It is a further fact that, although bovine 
tuberculosis has been increasing, human tuberculosis has been con- 
stantly declining in recent years, and the decline has been equally 
