92 DISEASES OF THE HOESE. 



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 con- 

 crete basin, wdiere they are drowned. In this way the exposed 

 manure pile serves to attract flies with a deceptive proffer of a breed- 

 ing 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. 



Strong YLEs {Strongylus spp. and CyllcostoTnuin spp.). — These 

 worms (PI. Y, 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 lib- 

 erty in the lumen of the intestines. 



The larvae of Strongylus equinus are found principally in the liver, 

 lungs, and pancreas. 



The larvse of Strongylus edentatus may be met with almost any- 

 where, especially under the serous membranes, the pleura and peri- 

 toneum. 



The embryos and larvae of species of CyVicostomiun 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 con- 

 stitutes 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 often termi- 

 nates fatally. The larvae of Cylicostomum form cysts in the walls 

 of the large intestine, and when these open they give rise to small 

 sores ; when they are numerous they cause a thickening and harden- 

 ing which impair the proper functioning of the intestine. Abscesses 

 sometimes perforate, causing death. The adult worm attacks the 

 intestinal wall, causing bleeding which results in anemia. The 



