470 DIGESTION 



gut through centers located in the spinal cord. The impulses from these 

 centers, besides contracting the rectum, etc., also coordinate the contrac- 

 tion of the abdominal muscles and the relaxation of the sphincter ani 

 so as to bring about the act of defecation. By the skiagraphic method it 

 has been found that the pelvic colon gradually becomes filled with feces 

 from below upward, and that the rectum remains empty until just before 

 defecation. 



Effect of Clinical Conditions on the Movements 



Observations of practical value have been made on the behavior of the 

 peristaltic wave after various intestinal operations. After an end-to-end 

 anastomosis of the gut, no evidence can be obtained by the x-ray method 

 that any hesitation occurs in the movement of the shadows at the anas- 

 tomosis. On the other hand, when a lateral anastomosis is established, 

 stagnation of the food in the region of the junction may occur, this 

 having been found, on opening the gut, to be caused by the accumu- 

 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 

 stroncr purge. 



