Pavlow showed that the chewing and swallowing of food which the dogs relished resulted, after a delay of about five minutes, in a flow of natural gastric juice from the side pouch of the stomach—a flow which persisted as long as the dog chewed and swallowed the food and continued for some time after eating ceased. Evidently the presence of food in the stomach is not a prime condition for gastric secretions, and, since the flow occurred only when the dogs had an appetite and the material presented to them was agreeable, the conclusion was justified that this was a true psychic secretion.” In several cases necessary operations on human beings have permitted of observations similar to these experiments on dogs. Thus, Richet, who had opportunity to observe such a case, “reported that whenever the girl chewed or tasted a highly sapid substance, such as sugar or lemon juice, while the stomach was empty, there flowed from the fistula a considerable quantity of gastric juice.” Another observer, Hornborg, “found that when the little boy whom he studied chewed agreeable food a more or less active secretion of gastric juice invariably started, whereas the chewing of an indifferent substance, as gutta-percha, was followed by no secretion.” Carlson has reported numerous similar observations on an adult. In the case of this man the sight, smell, or thought of food, even when he was hungry, was inadequate to cause the gastric juice to flow. Moreover, “the mere act of chewing indifferent substances, and the stimulation of the nerve endings in the mouth by substances other than those related to food,” caused no secretion. But a few minutes after the taste organs were stimulated by edible substances it was seen that not only did the flow of gastric juice begin, but the “hunger contractions” of the stomach were inhibited. Further, the secretion of gastric juice in this patient was clearly seen to vary with the palatability of the food. The chewing of bread and butter yielded a smaller flow than did the mastication of meat, and the flow was always greatest during the chewing of desserts, or on occasions when the food was said to be “unusually fine.” Oranges, of which the patient was especially fond, produced a greater flow than did pies, puddings, and other fruits. Carlson, in reporting these observations, says: “There is no question but that the mastication of a palatable dessert at the end of a meal serves to augment and prolong the appetite secretion of the gastric juice.”