slaughter all diseased and exposed animals, bury the carcasses in
quicklime, disinfect the premises (Figs. 107, 108 and 109) and enforce a
district, county and State quarantine, until after the infection has died
out. This statement may not hold true of methods of control in countries
where foot-and-mouth disease is widely distributed.

TETANUS. LOCKJAW.--This is an acute infectious disease that is
characterized by spasmodic contractions of voluntary muscles. The specific
germ remains at the point of infection, and produces toxins that cause
tetanic contractions of the muscles. It commonly affects horses, mules,
cattle, sheep and swine. The disease is most common in warm, temperate
climates.

[Illustration: FIG. 108.--Disinfecting boots and coats before leaving a
farm where cattle have been inspected for foot-and-mouth disease.
(Photographed by S. J. Craig, County Agricultural Agent, Crown Point,
Indiana.)]

[Illustration: FIG. 109.--Cleaning up and disinfecting premises where an
outbreak of foot-and-mouth disease has occurred.]

The _specific cause_ is a pin-shaped germ, the _Bacillus tetani_ (Fig.
110), that is present in the soil, especially those that are rich and well
manured. The germ enters the body by way of a wound, especially punctured
wounds. Infection may take place through some wound in the mucous membrane
lining the mouth, or other parts of the digestive tract. Infection may
follow a surgical operation, such as castration. In any case, the germ
requires an absence of air (oxygen) for its development.

_The period of incubation_ varies from one to two weeks, the length of time