death of the animal. Such parasites are injurious and may cause disease,
but it is only in rare cases that they cause death.

"_Pig typhoid_" is sometimes spoken of as a highly infectious disease
involving the intestines. A disease of hogs that may be termed typhus-fever
sometimes affects a large number of the hogs in the herd. This disease
occurs among hogs kept in small yards and houses that are crowded,
unsanitary and in continuous use, or when the hogs drink from wallows,
ponds and creeks.

The term swine-plague should not be used in speaking of outbreaks of
hog-cholera, as it is now considered a form of hog-cholera involving
especially the lungs.

[Illustration: FIG. 81.--Kidneys from hog that died of acute hog-cholera.]

[Illustration: FIG. 82.--Lungs from hog that died of acute hog-cholera.]

LESIONS.--In _acute hog-cholera_ the inflammation is hemorrhagic in
character. Small, red spots and blotches occur in different organs and
tissues. In the _chronic form_ of the disease ulceration of the intestinal
and gastric mucous membrane, inflammation of the lungs and pleura and
sloughing of the skin are common lesions.

_The skin_ over the under side of the neck, body and inside of the thighs
may appear red or purplish-red in color. The different groups of _lymphatic
glands_ are enlarged and softened. They may vary in color from a
grayish-red to a deep red, depending on the degree of engorgement with
blood. The pleura and pericardium may show small red spots and blotches.
The _kidneys_ are usually lighter colored than normal, and marked with red