28 PHYSIOLOGY OF ALIMENTATION. 



aid in the propulsion of the blood into the portal circulation 

 and the movement of the lymph through the lacteals. As 

 absorption and secretion by the intestinal mucosa are both 

 markedly influenced by the character of the blood which 

 flows through this tissue, it can at once be seen how impor- 

 tant these rhythmical contractions are. 



We turn now to a consideration of the peristaltic move- 

 ments in the small intestine. Peristalsis shows itself in two 

 forms, first as a slow advancement of the food for a short 

 distance in a coil, and secondly, as a rapid movement which 

 sweeps the food through several loops of the gut. The latter 

 is frequently seen under normal conditions when the food is 

 carried forward from the duodenum. It is produced arti- 

 ficially by injecting soap-suds into the rectum. 



When a mass of food has been subjected to the already 

 described segmenting movements for a time, the latter may 

 suddenly cease and the separate segments begin to move slowly 

 forward, each segment following closely upon its predecessor. 

 .After moving forward in this way for a few centimeters the 

 anterior segment comes to a stop, and the 

 succeeding ones are swept into it, until 

 the food lies stretched along the intestine 

 as a solid, resting string of food. 



Sometimes a single large mass of food, 

 sucn as ls indicated in Fig. 7, is pushed 

 forward. A long string of food is first 

 >(^ ^) 4 crowded together into a more rounded mass, 

 such as is shown in line 1. Suddenly this 



(CopifdfromcL, ^^ is indented in the middle and assumes 



NON: American in consequence the shape shown in line 



Journal of Ky- 2. A second division now occurs in the 



siology, 1902, VI posterior portion a which may cause the 



p. 260.) severed part to fly backward for some 



distance in the intestine, when a succeeding contraction 



again unites all the pieces into a rounded mass and pushes the 



whole slightly forward. This is shown in line 4 of Fig. 7. 



