This article is only available in the PDF format. Download the PDF to view the article, as well as its associated figures and tables. The administration of cinchophen is an effective method for the production of chronic peptic ulcer in dogs. The ulcer thus produced is similar in most respects to the lesion seen in human beings. The ulcer begins as a diffuse gastritis with destruction of the mucosal cells and the formation of multiple erosions throughout the gastric mucosa. These erosions become acute ulcers, which tend to heal. The majority do heal, but one persists as a chronic ulcer, and the gastritis subsides. This chronic lesion is usually situated from 2 to 3 cm. from the pyloric ring on the lesser curvature or on the posterior wall of the stomach. Occasionally, two or more gastric ulcers are present, and there may be an associated duodenal ulcer in a small percentage of the animals. The ulcer readily heals when the administration of cinchophen is stopped. Many controversial articles have been written on gastric secretion.