in the central portion.]

_There are two methods of applying_ the tuberculin test. The subcutaneous
test consists in injecting a certain quantity of tuberculin beneath the
skin, and keeping a record of the body temperature of the animal between
the eighth and eighteenth hours following the injection. Tubercular animals
show an elevation in temperature that comes on about the eighth or twelfth
hour of the test. In the _intradermal test_, a small quantity of a special
tuberculin is injected into the deeper layer of the skin. The seat of the
injection in cattle is a fold of the skin on the under side of the base of
the tail. In tubercular animals the injection is followed by a
characteristic local swelling.

[Illustration: FIG. 94.--A tubercular gland that is split open.]

[Illustration: FIG. 95.--Caul showing tuberculosis.]

[Illustration: FIG. 96.--Foot of hog showing tuberculosis of joint.]

The control of tuberculosis is largely in the hands of the breeder and
dairyman. This is a disease that requires the cooperation of stockmen and
sanitary officers in the application of control measures. If there are
several open cases of tuberculosis in a herd of cattle, the application of
the tuberculin test, removal of the reacting animals and disinfection of
the premises are not sufficient to eradicate the disease. It is necessary
to repeat the tuberculin test within six months, and later at twelve-months
intervals, until none of the animals that remain in the herd react.

The most practical method of disposing of dairy cows that react to the
tuberculin test is to slaughter them. Unless a large percentage of the herd