The peristaltic movements consist of more or less strong contractions of the circular coat of the intestine, varying from a slight ring-like contraction which passes rapidly down the gut to a violent constriction of the intestine which obliterates the lumen of the gut and passes very slowly from above downward. The slight contractions may travel, according to Bayliss and Starling, as rapidly as 2-5 cm. per second, while the more violent ones move not more than ¹⁄₁₀ cm. per second. According to Nothnagel, Mall, and others, the formation of these peristaltic waves is always due to a local stimulus, usually the presence of a bolus of food. The intestine contracts immediately above the point of stimulation and the mass of food is forced downward. The wave of contraction follows close behind the bolus, while for some distance above this point similar waves run downward until they reach the mass of food. The gut is usually relaxed below the bolus, and the general statement has been made that a stimulation at any point causes a contraction above that point and an inhibition below it. It is generally thought that Auerbach’s plexus is concerned in the propagation of the peristaltic wave since the peristalsis takes place also when the intestine is separated from the central nervous system, and does not occur when nicotine or cocaine is given to paralyze the intrinsic nerves of the intestine. In addition to the pendulum and the peristaltic movements, there is a third quite distinct motion to be observed in the intestine. The normal peristaltic movements are very slow, while this third type, called by Nothnagel “Rollbewegung,” consists of a rapid contraction which may pass from one end of the intestine to the other in 1 to 2 minutes. The function of this movement is thought to be the rapid elimination of irritating substances from the intestine. It occurs irregularly and is more common in slight pathological conditions of the gut.