INTESTINAL DIGESTION 



209 



7AM 



8 AM 



FIG. 43. These figures are intended to show the probable advance 

 of the food during the next few hours after dinner. For the sake of 

 simplicity the tract is represented as free from food taken pre- 

 viously and no supper is eaten. The course of the small intestine is 

 diagrammatic. 



At 1 p.m. the stomach is full and active. 



At 3 the stomach is smaller, having forwarded part of its contents to 

 the small intestine. 



At 5 the stomach is about empty and digestion is in progress at in- 

 tervals all along the small intestine. 



At 10 the small intestine is clear. There is antiperistalsis in the 

 ascending colon. The foremost portion of the material is near the 

 spleen. The mass now consists less of food than of associated 

 secretions. 



At 7 a.m. the chief accumulation is in the sigmoid flexure. The lag- 

 ging part is near the spleen. 



Breakfast is eaten, the lower part of the tract wakes to activity 

 at the same time as the stomach, and at 8 the sigmoid has thrust its 

 contents to the rectum. This is the occasion for defecation. 



part in digestion. In the rabbit, for example, it begins 

 in a large pouch (cecum), usually distended with soft 

 contents undergoing a decomposition which is bacterial 

 in its nature but presumably productive of some com- 

 pounds profitable to the organism. Such an animal 

 might not absorb nearly so large a percentage of its diet 

 if deprived of the colon. A dog or a cat does very well 



14 



