124 



THE HUMAN MECHANISM 



the one hand, good contact is secured between food particles 

 and digestive juices, while, on the other hand, the products 

 of digestion are quickly brought into contact with the villi for 

 absorption ; and, in the second place, the slow movement 

 of the food onwards in the intestinal tube. To accomplish 

 these ends there are two kinds of intestinal movements. 



FIG. 60. The divisive, or segmenting, movements of the small intestine 



A, surface view of a portion of the intestine, showing six constrictions which 

 divide the contents into five segments, as shown in B; as these constrictions 

 pass away, new ones come in hetween them and divide each segment of the con- 

 tents into two, the adjoining halves of neighboring segments fusing to make the 

 new segments shown in C. Repetition of this process results in the condition 



shown in D 



31. Divisive, or segmenting, movements. The food is not 

 distributed continuously along the entire length of the intes- 

 tine, but is subdivided into a number of separate portions 

 which lie in different loops of the tube. This is partly ex- 

 plained by the intermittent character of the discharge of the 

 chyme from the stomach. The number of these portions 

 varies at different times, but may be as many as twenty 

 or even more. A certain number, sometimes all, of these 



