STOMACH WORMS OF THE HORSE (_Habronema_ spp.).--These worms (Pl. V, fig. 4) occur in nodules in the mucous lining of the horse's stomach and are credited with doing more or less damage. Their presence is not likely to be diagnosed in the present state of our knowledge, but in case their presence is determined or suspected in connection with the summer sores noted later, tartar emetic is recommended. At least one of these worms has an intermediate stage in the ordinary housefly, the fly becoming infested while it is a larva developing in horse manure. Obviously, therefore, any measures looking toward the eradication of the fly or the proper disposal of manure will aid in the control and eradication of this worm. 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.