. The United States Bureau of Entomology has shown that fly
maggots travel downward through a manure pile as it comes time for the
maggot to enter the ground and pupate, and an excellent maggot trap,
consisting of an exposed manure platform raised on posts which are set
in a concrete basin extending under the platform and filled with three
or four inches of water, has been devised. As maggots work down they
come to the platform and escape through the spaces between the boards,
left open for the purpose, to the water in the concrete basin, where
they are drowned. In this way the exposed manure pile serves to attract
flies with a deceptive proffer of a breeding place.

Apparently it is the young forms of these stomach worms which develop at
times on the skin, causing a cutaneous habronemiasis known as summer
sores. This is discussed under diseases of the skin.

STRONGYLES (_Strongylus_ spp. and _Cylicostomum_ spp.).--These worms
(Pl. V, figs. 2 and 3) live in the large intestines of the horse as
adult worms and are often present in enormous numbers. Many of them are
very small, and the largest are less than two inches long. The adult
worms do considerable damage, but the immature or larval worms do even
more.

The larva of _Strongylus vulgaris_ enters the blood vessels of the
intestinal wall and finally attaches in the great mesenteric artery,
where it causes aneurisms; here it transforms to an adult without sexual
organs, which passes to the walls of the cecum and encysts, giving rise
to small cysts or abscesses; these cysts finally discharge to the
interior of the cecum, setting the worms, now mature, at liberty in the
lumen of the intestines.

The larvae of _Strongylus equinus_ are found principally in the liver,
lungs, and pancreas.

The larvae of _Strongylus edentatus_ may be met with almost anywhere,
especially under the serous membranes, the pleura and peritoneum.

The embryos and larvae of species of _Cylicostomum_ are found in the
mucosa of the large intestine.

Aneurisms impede the circulation of the blood, and may give rise to
intermittent lameness. The aneurism may rupture, since it constitutes a
weak place in the wall of the blood vessel, and the horse die of the
resulting hemorrhage. Particles of blood clots in the aneurisms may
break off and plug a blood vessel at the point where they lodge, thereby
causing the death of the part from which the blood is shut off and
occasioning a type of colic which