=Causation.= Hæmorrhagic enteritis is rarely seen except during the hottest days of summer, and in young animals which have previously shown nothing abnormal. The high temperature seems to favour its appearance, but is always supplemented by another cause, viz., the ingestion of irritant food, particularly of weeds and toxic plants or herbage of bad quality; amongst such may be mentioned dog’s mercury, and plants of the order Papaveraceæ, Euphorbiaceæ, etc. Otherwise the often rapid manner in which the disease develops indicates toxic enteritis. In other cases, more benign in appearance, but quite as grave in reality, blood is passed continually, and the disease assumes a chronic form. It is then of parasitic origin, and is due to intestinal psorospermosis. =Symptoms.= The primary symptoms are similar to those of acute enteritis, and consist of fever, dryness of the muzzle and of the mouth, colic and constipation. This is soon followed by loose motions containing blood or blood clots, according as the hæmorrhage occurs at a greater or less distance from the rectum. The fæces are then ejected violently to a considerable distance, on account of the exaggerated intestinal peristalsis. The disease may produce death in twenty-four hours, though usually the end is deferred for several days, or, in cases due to sporozoa, for a considerably longer time. In these cases there is some chance of recovery, provided that treatment be prompt. =The diagnosis= is very easy. =The prognosis= is in all cases grave. =The lesions= are ill-recognised. The animals die rapidly, and if not immediately examined show no characteristic lesions. The changes to be looked for consist in intense congestion or ulceration of the intestine, or even in ulceration of arterioles and of arteries of considerable size. In parasitic enteritis one finds localised inflammation and, in the epithelial interstices, sporozoa, which cause the rupture of blood-vessels. =Treatment.= It is necessary to act energetically from the outset, and to arrest hæmorrhage by acting on the intestine, on the vascular system, and on the skin. Mustard plasters or other external stimulant applications are therefore indicated. Internally, small doses of astringents like tannin, preparations of opium, 25 per cent. solution of sulphuric acid in alcohol, etc., are given to produce constriction of the vessels, though they seldom arrest the discharge of blood for long. In most cases it is necessary to have recourse to subcutaneous injections of ergotine, in doses of 5 to 10 grains in young animals, and 15 to 45 grains in adults. The dose may be given in two parts to prevent an unduly severe action. The smooth fibres of the small vessels are thus directly excited, and hæmorrhage ceases in consequence of clotting in the contracted vessels.