Boldyreff has reported that the contractions of the empty stomach in the dog cease during the periods of "spontaneous" secretion of gastric juice. We know that tasting or chewing palatable foods leads to reflex or "psychic" secretion of gastric juice in mammals (including man). May not the inhibition described above be an indirect one, due to the secretion of gastric juice, rather than a reflex inhibition of more direct character ? This question has been investigated and settled. A rapid secretion of gastric juice is associated with cessation, partial or complete, of the stomach contractions in Mr. V. We shall show later that this is due, not to the processes of secretion, as such, but to acid stimulation of nerve-endings in the mucosa. When the chewing or tasting of palatable foods leads to copious secretion of gastric juice, this gastric juice is one factor in the accompanying inhibition of the stomach movements.
We know, from Pavlov's work on dogs, that the latent period of the "psychic" secretion is about 5 minutes. The latent period of the "psychic" secretion in man is shorter (2 to 3 minutes). The inhibition of the stomach tonus and movements follows within a few seconds after placing the food in the mouth. Hence it is not an acid inhibition from the stomach. The same thing can be shown when the tasting or chewing of the food produces only a scanty secretion of gastric juice. The inhibition appears in the normal way, and the concentrations reappear on removing the food from the mouth despite the slow secretion of gastric juice.
It seems that a certain quantity of gastric juice must accumulate in the stomach or the free hydrochloric acid in the stomach must reach a certain concentration before the acid inhibition takes place. Thus, if the period of chewing or tasting the palatable food is short (4 to 6 minutes), the stomach contractions may reappear at the end of the stimulation in the mouth, and shortly afterward again be inhibited by the acid gastric juice. This inhibition continues during the phase of rapid "psychic" secretion. When the psychic secretion is more copious, the reflex inhibition from the mouth merges into the acid inhibition from the stomach.