t, and close confinement
in ill ventilated stables facilitate the spread of the disease, and
sooner or later, other animals acquire the trouble. This may all
occur while all animals appear in a healthy condition.

The symptoms of the disease in the earlier stages are quite
indefinite. As the disease progresses, the nutritive functions
appear to be disturbed, and sooner or later, the body weight begins
to decline, and finally marked emaciation ensues. Accompanying this
condition, especially when the disease is in the lungs, is a cough,
which is generally aggravated with active exercise. While the
run-down condition permits frequently of the detection of the
disease in the advanced stages, it is wholly impossible with any
accuracy to diagnose the trouble in the incipient stages. It is at
this stage that the tuberculin test comes to the aid of the
stockman.

_Tuberculin test._ This test is made by the injecting beneath the
skin of the animal a small quantity (about 2 c. c.) of tuberculin,
and noting the temperature of the animal, before and after the
injection. Tuberculin, a product of the growth of the tubercle
bacillus, when injected into the body causes a marked rise in
temperature, in the case of an animal affected with the disease, and
no such elevation in the case of a healthy animal. The process of
preparing tuberculin makes it absolutely free from danger, so far as
liability of producing the disease, or in any way injuring the
animal, is concerned. Fig. 19 shows the temperature range of both
reacting and non-reacting animals. While the test is not
absolutely infallible, it is so far superior to any and all other
methods of diagnosis that it should take precedence over them.

=Miscellaneous diseases.= There are a number of diseases that affect
both human beings and cattle, the causal organisms of which may be
transmitted through the milk. Foot and mouth disease is one wide
spread in European countries but which has not yet gained a
permanent foothold in this country. The ingestion of the milk, which
always contains the causal organism, produces the disease in both
humans and cattle. In the human the disease is very similar to that
in cattle; it may end in death. Vesicles are produced in the mouth,
on the lips, nose and fingers. The causal organism, which has not
yet been demonstrated, may occur in butter or cheese. It is easily
destroyed by pasteurizing the milk.

[Illustration: Fig. 19.--Temperature Curves.