NATURE OF THE INTESTINAL MOVEMENTS. 329 



nearly always travel from above downwards. After paralysis of 

 the local nervous mechanism (Auerbach's plexus) by nicotin or cocain, 

 the waves are still present in undiminished force, but now travel 

 indifferently in either direction. They therefore originate in the muscle 

 fibres, and probably are transmitted from one muscle cell to the next, 

 i.e. the contractions are myogenic and myodromic. 



The post-mortem " vermicular " contraction described by Engelmann 

 in the rabbit is probably merely an exaggerated wave of the type 

 just described, since it may be excited by local stimulation, and 

 travels equally well in either direction at a rate of 3 to 4 cms. per 

 second. 



Mall, however, would place this form of contraction in a class by itself, and 

 distinguishes, therefore, three types of contraction, namely, pendular or 

 rhythmic, vermicular, and peristaltic. 



2. True physiological peristalsis is a slow process. According to 

 Cash, 1 it takes in the cat about an hour and a half to travel from one 

 end of the intestine to the other. On observing the intestines in an 

 animal, after division of the splanchnic nerves, such waves of constric- 

 tion may be seen passing slowly down the gut, or, if absent, may be 

 excited by mechanical stimulation. They may be studied by introducing 

 a bolus of wax, or cotton-wool and vaseline, into the intestine at some 

 point. Almost immediately it will be noticed that the segment of 

 intestine just above the bolus enters into a strong tonic contraction. 

 At the same time the intestine for a considerable length below the 

 bolus is inhibited and relaxed, as may be shown by recording the con- 

 tractions of either muscular coat by means of the enterograph. In con- 

 sequence of this contraction above and relaxation below, the bolus moves 

 onwards down the intestine, followed up and driven by the advancing 

 ring of constriction. If the intestine be less irritable, the introduction 

 of the bolus may cause merely an augmentation of the rhythmic con- 

 tractions of the segment above, and the inhibition below may be only 

 slightly marked. In this case the movement of the bolus still occurs, 

 but is incomparably slower than under the conditions just described. 

 It may be quickened if we increase the stimulus due to the presence of 

 the bolus by pinching the gut at this point, each pinch being followed 

 by a temporary inhibition of the gut below, and a corresponding accelera- 

 tion of the movement of the bolus. The progression of the bolus down 

 the intestine depends, therefore, on two events, which are excited by the 

 mere presence of the bolus, namely, augmentation of contraction above, 

 and inhibition of contraction below, the bolus. This double effect is 

 the characteristic response of the intestine to local stimulation. If we 

 record the contractions at any point of the gut, it will be found that a 

 pinch applied from 1 inch to 12 inches above the recorded spot gives an 

 instant inhibition of the rhythmic contractions ; whereas a pinch applied 

 from \ inch to 3 inches below produces, after a varying latent period, an 

 augmentation of the contractions. 



It is evident that the true peristaltic contraction is a co-ordinated 

 reflex, carried out by the local nervous centres in the wall of the gut. 

 By means of the injection of nicotin or the local application of cocain, 

 we can paralyse the nerve centres, leaving the muscle fibres intact. We 

 then find that, although the rhythmic contractions are even better 

 1 Proc. Roy. Soc. London, vols. xl. and xli. 



