Some species attach themselves to the intestinal wall, suck the blood of
the host and cause anaemia and debility. Colic resulting from _circulatory
disturbances_ is not common. The female of a certain species of
_strongulus_ deposits eggs in the mucous membrane. On hatching, the larvae
may enter a blood capillary, drift along in the blood stream and finally
come to rest in a large blood-vessel that supplies a certain portion of the
intestines with blood. Here the parasite develops. The wall of the vessel
becomes irritated and inflamed, pieces of fibrin flake off and drift along
the blood stream until finally a vessel too small for the floating particle
to pass through is reached and the vessel becomes plugged. The loop of
intestine supplied by it receives no blood. A temporary paralysis of the
loop occurs, which persists until a second vessel is able to take over the
function of the one that is plugged. This form of colic is most common in
old horses (Fig. 16).

Such complications of acute indigestion as _twisting, infolding_ and
_displacement of the intestine_ may occur. It is not uncommon for a
stallion to suffer from strangulated hernia, due to a rather large internal
inguinal ring and a loop of the intestine passing through it and into the
inguinal canal or scrotum. Such displacements are usually accompanied by
severe colicky pains.

_The symptoms_ vary in the different cases. In the mild form, the colicky
pains are not prominent, but in the acute form, the animal is restless,
getting up and down in the stall and rolling over. These movements are
especially marked when the abdominal pain is severe.

_In the spasmodic form_ the attack comes on suddenly, the colicky pains are
severe, and the peristaltic movement of the intestine is marked and
accompanied by loud intestinal sounds. In most cases of indigestion