We have been unable to obtain any definite evidence of inhibition of the stomach movements by the movements of mastication when the mouth is empty. But chewing what may be called indifferent substances, such as paraffin, gum, or straw, produces distinct inhibition. Most of the experiments were made by chewing paraffin. Most people can chew paraffin without any sensation of a disagreeable or unpleasant tone, or of a pleasant tone, either, for that matter. Mr. V. said he "did not care for the paraffin," naturally. But he has no dislike for it. The chewing of indifferent substances produces, on the whole, less inhibition than do gustatory stimuli. The stomach "escapes" from the inhibition in a few minutes, even though the chewing is continued with uniform vigor. The chewing usually fails to produce any effects in the tetanus' stage of the stomach activity.
Inasmuch as the masticatory movements do not cause inhibition if the mouth is empty, we may conclude that inhibition produced by chewing indifferent substances is initiated by mechanical stimulation of afferent nerve-endings in the mouth.