=The Stomach.=—The sight and smell of food, its presence in the mouth, and the performance of mastication, which induces a secretion of saliva, gives rise at the same time to a flow of gastric juice. It is psychic stimulation and the act of eating which cause gastric juice to ooze from the gland-tubes of the stomach at the commencement of digestion, not the stimulation of nerve-endings by food which has passed down the œsophagus. As a consequence of gunshot wounds, or as the result of operations performed for the purpose of relieving patients whose œsophagus has become blocked, numerous cases have been recorded in which a fistulous opening into the stomach has made it possible to study the interior of this organ. Such cases present an opportunity of watching the digestion of various foods introduced through the opening, and of collecting gastric juice for purposes of analysis. A similar condition has been established in animals by operative means. The œsophagus having been cut, and the cut end sutured to the margins of an aperture in the skin, food taken by the mouth escaped by this opening instead of passing into the stomach. A similar opening was made into the stomach for the insertion of food, and for the purpose of studying the effects of reflex stimulation of the gastric glands. As soon as food was introduced into the mouth, gastric juice began to flow. The advantage of this experimental method lies in the fact that the juice secreted was a pure juice—not mixed with food, as in all the earlier experiments in which, the stomach being opened without diversion of the œsophagus, the presence of food within it was the stimulus which led to secretion. No juice flowed in the absence of stimulation; nor was the secretion normal in composition when provoked by a mechanical stimulus, such as the tickling of the gastric mucous membrane by a feather.