An improved method for studying the peristaltic reflex in the isolated colon.

1. A method is described for studying the peristaltic reflex in the guinea-pig or cat isolated colon, using a graded localized intraluminal stimulus consisting of a solid bolus.2. The method gives an easy evaluation of propulsive activity and makes it possible to record simultaneously the segmental activity of the circular muscle in relation to the site of stimulation and the contractions and relaxations of the longitudinal muscle coat.3. The velocity of propulsion, which is a reliable measure of propulsive activity, is dependent on the degree of distension and is easily affected by physical agents and nervous stimulation. A solid bolus is propelled only when there is simultaneous ascending contraction and descending inhibition of the circular musculature.4. Since the peristaltic reflex could not be elicited from areas from which the mucosal and submucosal layers had been removed, these layers are essential for the triggering of the peristaltic reflex and for the propulsion of solid contents in the colon.