Although it has long been known that the sight of food under certain conditions would call forth a secretion of gastric juice in a hungry dog (Bidder and Smith, 1852), and common observation has told us that emotion strongly affects the gastrointestinal functions, increasing or diminishing the secretions of saliva and gastric juice, and even producing dyspeptic disturbances and diarrhœa, it has remained for Pawlow and his co-workers to demonstrate the important part which the “appetite,” as a psychical state, plays in the process of digestion. In hungry dogs a large quantity of gastric juice, rich in ferment, is poured out when food is swallowed, and even at the sight of food, and it was proved that this outpouring was due to psychical influences. Simply teasing and tempting the animal with food cause secretions, and food associations in the environment may have the same effect. “If the dog has not eaten for a long time every movement, the going out of the room, the appearance of the attendant who ordinarily feeds the animal—in a word, every triviality—may give rise to excitation of the gastric glands.” (Pawlow, p. 73.) This first secreted juice is called “appetite juice,” and is an important factor in the complicated process of digestion. “The appetite is the first and mightiest exciter of the secretory nerves of the stomach.” (Pawlow, p. 75.) Pawlow’s results have been confirmed in man by Hornborg, Umber, Bickel, and Cade and Latarjet. The mere chewing of appetizing food, for instance, is followed by a copious discharge of gastric juice, while chewing of rubber and distasteful substances has a negative result. Depressing emotions inhibit the secretion of juice (Bickel). More than this, Cannon,[204] in his very remarkable experiments on the movements of the stomach and intestines, found that in animals (cat, rabbit, dog, etc.), gastric peristalsis is stopped whenever the animal manifests signs of rage, distress, or even anxiety. “Any signs of emotional disturbance, even the restlessness and continual mewing which may be taken to indicate uneasiness and discomfort, were accompanied in the cat by total cessation of the segmentation movements of the small intestines, and of antiperistalsis in the proximal colon.” Bickel and Sasaki have confirmed in dogs these emotional effects obtained by Pawlow and Cannon. The effect of the emotions on the digestive processes is so important from the standpoint of clinical medicine that I quote the following summary of published observations from Cannon: "Hornborg found that when the boy whom he studied chewed agreeable food a more or less active secretion of the gastric juice was started, whereas the chewing of indifferent material was without influence.