234 PHYSIOLOGY CHAP. 



On opening the abdomen of a recently killed animal, so as to 

 expose the intestines, they are seen to be the seat of writhing 

 or vermicular movements. At first these are hardly perceptible, 

 and are confined to the upper part of the small intestine, but they 

 soon become more ample and extend over its entire length to the 

 last section of the ileurn, with decreasing vigour. They consist of 

 contractile waves propagated peristaltically, and preceded by waves 

 of dilatation ; the coils of intestine are displaced and move forward, 

 some being pushed down, while others come to the surface, sliding 

 one over the other. The irregularity and simultaneous appearance 

 of these vermicular movements in different parts of the intestine 

 confuse the observer, so that it is impossible to grasp the rhythm, 

 or the ascending or descending direction of the motion. After 

 reaching their maximum intensity, the waves gradually diminish, 

 and die out. But after the spontaneous movements have ceased, 

 it is possible to start them again by various stimuli. Haller 

 excited intestinal movements in a dog an hour after death, Colin 

 in the horse after about 50 minutes. 



The movements observed in animals with an open abdomen, 

 such as Haller described, are, however, quite unlike the true 

 physiological phenomenon, i.e. the movements normally serving in 

 the intestine to propel and churn up the chyme, and to facilitate 

 intestinal absorption. They result from the abnormal conditions 

 of the intestine exposed to the air after the death of the animal, 

 when it becomes hyperaemic, cooled, and dried up. 



If immediately after opening the animal's abdomen it is filled 

 with physiological saline, warmed to body-temperature : or better, 

 if the abdomen of a living rabbit be opened after fixing it in a 

 holder, and plunging the whole into a bath of the same saline 

 at 38 C., as first attempted by Sanders-Ezn and von Braam- 

 Houckgeest (1872), the duodenum and the jejunum alone exhibit 

 very slight movements, which can be separated into two groups, 

 according to whether or no they assist the progress of the 

 intestinal contents towards the large bowel : the former, known as 

 peristaltic movements, originate in a ring of constriction which 

 travels like a wave from one part of the intestine to the other ; 

 the latter, known as pendulum movements, exhibit a rhythmic 

 to-and-fro motion of the single coils, which alternately contract and 

 expand so that the contents are shifted about and thoroughly 

 mixed. 



According to van Braam-Houckgeest, the longitudinal fibres 

 play an active part, even in the weakest peristaltic contractions, 

 for the advancing ring of constriction is immediately preceded by 

 a shortening and widening of the intestine which promotes the 

 advance of its* contents towards the ileum. The length of the 

 annular wave of peristalsis varies greatly. If it traverses a short 

 distance, it is weak, and is frequently renewed. With stronger 



