152 PKACTICAL PHYSIOLOGY 



reach the pylorus, and the waves occur about every 10 sec. The 

 fundus acts as a reservoir for the food, while the pylorus mixes, 

 triturates and expels the food into the duodenum. In the intestine 

 rhythmic segmentation of the food is brought about by constrictions 

 of the gut which continually occur at ever- varying points. There 

 may be 30 such segmentations per minute. Such movements mix 

 the food and juices, and express the contents of the venous and 

 lymphatic radicles. Peristaltic movements occur in addition to the 

 segmentation movements, and drive the contents onwards. Anti- 

 peristaltic movements are frequent in the large intestine. This 

 increases absorption. The ileo-caecal valve is normally competent, and 

 prevents the antiperistalsis returning any of the contents of the large 



Pio. 134. Pendulum movements of the intestine inhibited by excitation of the 

 splanchnic nerve during the period marked by the white line. (Starling.) 



into the small intestine. With the accumulation of material in the 

 colon deep tonic constrictions appear one after another and carry the 

 food into the descending colon. Fear or rage entirely inhibits the 

 movements of the intestines. 



Nutrient enemata (mixed with bismuth), when injected into the 

 large intestine under pressure, may be carried by the antiperistalsis 

 of the colon into the small intestine. 



In the anaesthetised animal placed in a bath of warm saline, the 

 bowels may be exposed, and a small indiarubber bag inserted in 

 the small intestine. The bag is connected with a recording tambour. 

 The splanchnic nerves are divided to prevent the reflex inhibition of 

 the movements which otherwise would result. The gut exhibits 

 rhythmic swaying movements caused by waves of constriction which 

 occur every 5-6 sees., and travel 2-5 cm. per sec. These movements 

 are myogenic, for they occur in the enervated intestine. If a bolus 

 of cotton wad and vaseline be introduced, or the gut be pinched below 

 the tambour it excites contraction above and dilatation below the 



