on this
point are conflicting and further information is much desired. Some have
asserted so long as the udder itself shows no lesions that no tubercle
bacilli would be present,[86] but the findings of a considerable number
of investigators[87] indicate that even when the udder is apparently not
diseased the milk may contain the specific organism as revealed by
inoculation experiments upon animals. In some cases, however, it has
been demonstrated by post-mortem examination that discoverable udder
lesions existed that were not recognizable before autopsy was made. In
the experimental evidence collected, a varying percentage of reacting
animals were found that gave positive results; and this number was
generally sufficient to indicate that the danger of using milk from
reacting animals was considerable, even though apparently no disease
could be found in the udder.

The infectiousness of milk can also be proven by the frequent
contraction of the disease in other animals, such as calves and pigs
which may be fed on the skim milk. The very rapid increase of the
disease among the swine of Germany and Denmark,[88] and the frequently
reported cases of intestinal infection of young stock also attest the
presence of the organism in milk.

The tubercle bacillus is so markedly parasitic in its habits, that,
under ordinary conditions, it is incapable of growing at normal air
temperatures. There is, therefore, no danger of the germ developing in
milk after it is drawn from the animal, unless the same is kept at
practically blood heat.

Even though the milk of some reacting animals may not contain the
dangerous organism at the time of making the test, it is quite
impossible to foretell how long it will remain free. As the disease
becomes more generalized, or if tuberculous lesions should develop in
the udder, the milk may pass from a healthy to an infectious state.

This fact makes it advisable to exclude from milk supplies intended for
human use, all milk of animals that respond to the tuberculin test; or
at least to treat it in a manner so as to render it safe. Whether it is
necessary to do this or not if the milk is made into butter or cheese is
a somewhat different question. Exclusion or treatment is rendered more
imperative in milk supplies, because the danger is greater with children
with whom milk is often a prominent constituent of their diet, and also
for the reason that the child is more susceptible to intestinal
infec