The chemical makeup of gastric juice was presented, and the physiological response for each one noted. The secretion of gastric juice due to the thought of food, the presence of food in the mouth, and the presence of food in the stomach was presented. The digestion of protein in the stomach was presented using the treatment done on the trapper St. Martin in the 1700's. The overproduction of gastric juice, specifically the hydrochloric acid, was shown to attribute to the formation of gastric ulcers, especially in hyperactive, type A personalities.