THE MECHANISMS OF DIGESTION 



493 



evacuation. The sphincter opens in response to every peristaltic wave 

 arriving at the antrum and apparently does so blindly without regard to 

 the reaction of the gastric or duodenal contents. That some factor other 

 than gastric peristalsis, however, may influence the emptying time is 

 probable. It is difficult, otherwise, to account for the rapid passage from 

 the stomach of water and egg-white and the retention of other substances 

 until they reach a more or less fluid consistency. 



The later work of Wheelon and Thomas 33 points to the existence of 

 an intimate relationship between the activities of the duodenum below 



Fig. 159. Diagram of the relationships of the contractions of antrum, sphincter and duo- 

 denum and of the passage of chyme from the antrum into the duodenum 3, Ci, Cz. The seg- 

 mental waves of the duodenum are marked A, B, C t D, and E and it will be noted that A oc- 

 curs when the antrum is completely relaxed and the sphincter contracted. It will therefore 

 assist to empty the "reservoir cap" of the duodenum. The duodenum is seen to be relaxed to 

 its greatest extent after the antrum has ceased contracting and when the sphincter is contracted. 

 (After Wheelon and Thomas.) 



the " reservoir cap" and the movements of the antrum and pyloric sphinc- 

 ter. When simultaneous tracings were taken of the antrum and sphinc- 

 ter and of the duodenum below the "cap" definite relationships were 

 found to exist between the activities of these portions of the digestive 

 tube. These relationships are shown diagrammatic ally in Fig. 159. The 

 duodenum enters upon its positive phase 2% seconds after the commence- 

 ment of the sphinster contraction and at this moment the antrum is relax- 

 ing and remains relaxed throughout the sphincter and duodenal contrac- 

 tions. The sphincter enters upon its negative phase a short time prior 

 to the maximal contraction of the duodenum and the greatest relaxation 



