Hunger-Reducing Effects of Food by Stomach Fistula versus Food by Mouth Measured by a Consummatory Response
In a study, M. Kohn compared the immediate effect on hunger drive in albino rats of 14 cc. enriched milk injected directly into the stomach, 14 cc. enriched milk taken normally by mouth, and a control injection of 14 cc. of isotonic saline. For his measure of hunger, Kohn used the rate of performing a response reinforced periodically with food. The measure of hunger was the amount of milk drunk during a 10-min. test period from a glass tube, inside diameter 4mm. but slightly constricted at the end by fire-polishing, which was inserted into each animal’s living cage. The experiment, using a consummatory response to measure hunger, yielded exactly the same pattern of results as did Kohn’s experiment, which used an instrumental response to measure hunger. In both cases an injection of milk directly into the stomach produced a prompt reduction in response, and milk taken normally by mouth produced an even greater reduction.