DIGESTION 



201 



extreme upper portion of the duodenum presents, due to its distension by 

 food, it has been designated, the cap or pilleus ventriculi. 



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 

 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 peris- 

 taltic waves. To avoid confusion, the 

 term diastalsis has recently been em- 

 ployed (Cannon) to designate the true 

 peristaltic movement, viz.: progressive 

 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.-^^ conditions 



that are perhaps not Strictly physiologic, ones come in between them and divide 



a rapid and far-reaching peristalsis is 



developed which may paSS Over trie in- 

 testine, from the duodenum to the CCCUm C. 



without stopping in the course of 15 



seconds, in the rabbit, and which has Mechanism.") 



been designated rush peristalsis. It is . . 



characterized by a wave of constriction preceded by a completely inhibit* 



long section of intestine. The contents of the intestine are earned along 



with extreme rapidity and vigor. The contractions may be increased by 



purgative salts, ergot, barium chlorid, etc., the inhibition may be increased 



by calcium chlorid, magnesium chlorid, etc. A combination of ergot and 



calcium chlorid develops in the rabbit a pronounced rush peristalsis (Meltzer). 



This movement appears to be under the control of the central nerve system 



as it fails to develop after division of the vagus nerves. 



Bayliss and Starling state, from observations made on the exposed 

 intestine of a dog, that in addition to the usual peristaltic movement the 

 intestinal coils exhibit a swaying or pendulum movement accompanied by 

 slight waves of contraction which may arise apparently at any point and 

 pass down the intestine. These contractions may occur from ten to twelve 

 times a minute and travel at a rate varying from two to five centimeters a 



A, surface of a portion of the intestine, 

 showing six constrictions which divide the 



to make the new segments shown in 

 Reetition of this rocess results in the 



