104 STUDIES IN CLINICAL PHYSIOLOGY 



tightly contracted for as long as twenty-four hours — 

 a highly significant observation, as we shall see. 

 Whenever food is taken into the stomach, the ileo- 

 caecal sphincter is refiexly inhibited, and the last 

 contents of the ileum pass through. 



The rectum is of course under direct control of 

 the centre near the tip of the spinal cord, the motor 

 path being the pelvic visceral nerves from the second 

 to the fifth sacral roots ; the sympathetic system 

 also supplies the rectum. The physiology of defeca- 

 tion is well known, and need not detain us. 



In the caecum and the ascending, transverse, 

 descending, and pelvic portions of the colon, however, 

 the motor functions are involuntary, as in the small 

 intestine, but with some striking differences. The 

 food residue does not travel at a slow regular rate 

 of progress through the large intestine. It lingers 

 in particular locaUties, such as the caecum and 

 ascending colon, the middle of the transverse colon, 

 the pelvic colon, and the rectum, for hours at a time, 

 and although it has been denied, it is certain that 

 antiperistalsis occurs, but not over great lengths of 

 the bowel. In the small intestine antiperistalsis is 

 rare and pathological. Three or four times a day, 

 and especially by a gastrocohc reflex after taking 

 food, the intestinal contents are carried onwards 

 for several feet by massive waves of peristalsis, 

 of which the patient is normally quite unconscious. 

 These waves have been witnessed by a number of 

 observers. Here we have the explanation of " lien- 

 teric " diarrhoea immediately following a meal, and 

 also of the pain after food met with by some sufferers 



