THE MECHANISMS OF DIGESTION 505 



lation of hair and undigested detritus at the opening between the op- 

 posed loops. Another objection to lateral anastomosis is the fact that 

 in performing the operation a considerable amount of the circular muscle 

 is cut, which interferes with peristaltic activity. Moreover, the end of 

 the proximal loop beyond the opening is in danger of becoming filled up 

 with hardened material, and the end of the distal loop may become 

 invaginated and induce obstruction in the region of the anastomosis. 



Observations have also been made by the x-ray method on the be- 

 havior of the intestinal contents following intestinal obstruction. It has 

 been observed that, as the material collects in the gut just above the 

 obstruction, strong peristaltic waves are set up, which move the food 

 toward the obstruction so powerfully as to cause the walls of the canal 

 in front to become bulged, until at last the pressure causes the con- 

 tents to be squirted back through the advancing ring of peristaltic con- 

 traction. These waves were observed to succeed one another rapidly. 

 When a portion of gut is reversed in position, the peristaltic waves con- 

 tinue to travel in their old direction toward the duodenum. The effect of 

 this is to produce a partial obstruction at the upper end of the re- 

 versed gut. 



The type of peristalsis known as the peristaltic rush can be induced 

 experimentally in animals by intravenous injection of ergot. It prob- 

 ably also occurs in conditions of abnormal irritation of the gut in man, 

 and is believed to be the characteristic activity of the gut after a 

 strong purge. 



