DIGESTION. 



197 



ring of relaxation or inhibition. The rate of movement of the peristaltic wave 

 is usually extremely slow except in the duodenal region where it is quite rapid. 



After the peristaltic wave has advanced the food a variable distance, it 

 disappears and the food comes to rest. By this procedure the incoming food 

 from the stomach is readily accommodated in the duodenal portion of the 

 intestine. With the disappearance of the peristaltic wave, rhythmic seg- 

 mentation again arises in the portion of the intestine corresponding to the 

 new situation of the segment of food. This in turn is succeeded by another 

 peristaltic wave which advances the food to a more distant region of the 

 intestine. This continues until at the end of gastric digestion a more or less 

 continuous column of food occupies the lumen of the small intestine from the 

 stomach to the ileo-cecal valve. 



In addition to this characteristic physiologic movement it has also been 

 observed by different experimenters that the intestine manifests under special 

 circumstances two other forms of moving waves, waves moving downward 



FIG. 85. THE DIVISIVE OR SEGIMENTING MOVEMENTS OF THE SMALL INTESTINE. A, surface 

 of a portion of the intestine, showing six constrictions which divide the contents into five 

 segments, as shown in B: a~s these constrictions pass away new ones come in between them and 

 divide each segment of the contents 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. (Modified, after Hough andSedgewick, " The Human Mechanism") 



as well as upward from their point of origin, but without being preceded by 

 an inhibition or relaxation. These waves are therefore not regarded as true 

 peristaltic waves. To avoid confusion, the term diastalsis has recently been 

 employed (Cannon) to designate the true peristaltic movement, viz.: pro- 

 gressive contraction preceded by inhibition, and the terms katastalsis and 

 anastalsis to designate the descending and ascending contractions respectively, 

 that occur without a forerunning inhibition. 



Rush Peristalsis. Under conditions that are perhaps not strictly 

 physiologic, a rapid and far-reaching peristalsis is developed which may pass 

 over the intestine, from the duodenum to the cecum without stopping in the 

 course of 15 seconds, in the rabbit, and which has been designated rush 

 peristalsis. It is characterized by a wave of constriction preceded by a 



