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becomes emaciated, is easily exhausted and the coat becomes rough. The
worms wander about in the gut and their bites cause small wounds in the wall
through which harmful bacteria may gain entrance. The migrating larvae also
cause injuries of various types to the organs and tissues through which they
pass. Whether or not these parasites produce toxic secretions is not de-
finitely known, but they must be harmful when they die and disintegrate in
the bowel.
The larvae of the single-toothed strongyle—S. vulgaris—are particularly
injurious and may be responsible for numerous cases of colic due to the aneu-
rysms they produce. This is borne out by the reduction in the number of
cases of colic following on measures to prevent infestation with this parasite.
The larvae settle in certain arteries, specially the anterior mesenteric artery
supplying blood to the large intestine, with the result that the wall of the
artery, where the worms accumulate, becomes thickened and stretches con-
siderably to form an aneurysm. It is a spindle-shaped, cylindrical, or
globular dilatation of a blood-vessel which often contains a very heavy deposit
of fibrin. It may attain the size of a child's head. This condition seriously
interferes with the circulation of blood resulting in a diminished blood supply
to the large intestine and thus leading on to colic, twist or intussusception.
Occasionally a piece of the fibrin deposit in the aneurysm may break loose
and plug the terminal portion of an artery with the result that the circulation
of a part of the intestine is cut off, producing local anaemia and reduced
peristalsis with the consequences mentioned above. In extreme cases such
conditions prove fatal. Opinions, however, differ with regard to the role
played by the aneurysm and its associated thrombus in the production of
colic. Some believe that the local anaemia and reduced peristalsis are caused
by the embolism of an artery supplying a portion of the intestine; while
others maintain that the inflammatory processes produced by the larvae
in the wall of the anterior mesenteric artery affects the nerves of the coeliac
and anterior mesenteric plexuses and the affected nerve supply of the in-
testine creates favourable conditions for the occurrence of impaction, volvulus
and intussusception. Thus aneurysm acts only indirectly in the production
of colic. In any case it would appear that most cases of colic in horses are
due to the presence of larvae in the blood vessels supplying the gut. Colie
may also result from intestinal catarrh interfering with the normal function
of the intestine with the result that food is not properly digested and fer-
mentation takes place.
When horses suffering from strongylidosis are treated for worms the
above symptoms disappear, they put on weight and regain their working capa-
city. Diagnosis is made by finding the eggs in the faeces. Before administering
any treatment the animal should be starved for 36 hours in order to
reduce the contents of the large intestine. There are three drugs which are
effective against strongyles of horses : oil of chenopodium, carbon-tetra¬
chloride and normal butylidene chloride. Oil of chenopodium is given in a
dose of 4 to 5 fluid drm. (10 to 20 c.c.) to an animal weighing 1,000-lbs.,
and is immediately followed or preceded by one quart of raw linseed oil or