Causes: peptic digestion, paresis, caustics, irritants, acids, alkalies, salts, mechanical irritants, hot food, parasites, thrombosis, embolism, specific disease poisons, aneurism, tumors, infective growths, nervous disorder, debility, toxins of diphtheria, staphylococcus, etc. Symptoms: slight colics, tympany, emaciation, vomiting blood, tender epigastrium, dark or bloody stools, irregular bowels; in carnivora abdominal decubitus, arched back, bloody, mucous, acid vomit, colics after meals. Lesions: in horse erosions, ulcers, parasites, neoplasms, discolorations, extravasations; in cattle and dogs on folds, nature of ulcer. Treatment: restricted, digestible diet, lavage, anodynes, bismuth, antacids, antiseptics, salol, naphthol, chloral, pure water. _Causes._ Gastric ulcers may arise from quite a variety of causes which determine necrotic conditions of the mucosa and the gradual invasion of the resulting lesion by destructive microbes. One of the simplest factors is the peptic juice, the stomach, being struck with paresis (in inflammation, fever, nervous disorder), while containing a quantity of its secretion, undergoes an autodigestion which affects particularly the lowest (pyloric) portion, toward which the liquid gravitates, and the free edges of the folds which are the most exposed to its action. The swallowing of irritant and caustic agents (the mineral acids or alkalies, mercuric chloride, tartar emetic, antimony chloride, Paris green, arsenious acid, etc.) by corroding or causing destructive inflammation of the exposed mucous membrane may similarly operate. This is especially the case with monogastric animals, (horse, pig, dog, cat), as in the ruminants such agents tend to be diluted in the first three stomachs and rendered more harmless. Mechanical irritants may cause the lesion and infection atrium in any of the domestic animals, pins, needles, nails, pieces of wire and other sharp pointed bodies being swallowed by horse and ox, and small stones, pieces of bone, and all sorts of irritant objects picked up by the puppy or rabid dog. Cooked food swallowed hurriedly at too high a temperature is especially liable to start necrotic changes in the single stomach of horse, pig or dog, the ruminant being in a measure protected by the food passing first into the rumen. The wounds caused by gastric parasites may become the starting points of molecular degeneration and ulceration. In the horse the spiroptera megastoma, s. microstoma, and the larvæ of the various œstri; in cattle and sheep the strongylus contortus, s. convulutus, s. filicollis and s. vicarius; in swine the spiroptera strongylina, Simondsia paradoxa, and gnathostoma hispida; in dogs spiroptera sanguinolenta, and in cats the ollulanus tricuspis act in this way. Gastric catarrh debilitates the affected mucosa and lays it open to necrotic microbian infection especially in the pyloric sac and on the summit of the folds.