16 PHYSIOLOGY OF ALIMENTATION. 



5. The Passage of Different Foodstuffs from the Stomach. 

 The Opening and Closing of the Pyloric Sphincter. It 

 is the function of the pylorus, through the contraction 

 of the muscular fibres contained in it, to keep the gas- 

 tric contents from being forced out of the stomach whi/e 

 subjected to the churning movements of this organ. At 

 certain times, however, the pylorus relaxes and allows a 

 part of the gastric contents to pass through. Some of the 

 older observers believed that the pylorus was contracted 

 during the entire digestive period and that only when the 

 food had been thoroughly mixed with the gastric juice did 

 it relax and allow the stomach to empty itself entirely and 

 at once. We know now, from the findings of EWALD, BOAS, 1 

 and PENZOLDT 2 with the stomach-tube, and the more per- 

 fect experiments of CANNON 3 with the x-rays, that the 

 stomach empties itself little by little through periodic open- 

 ings and closings of the pylorus. As has been shown above, 

 the peristaltic waves of the stomach pass continuously 

 under normal conditions from the middle of the stomach 

 to the pylorus. As long as the pylorus is closed these waves 

 serve only to churn the food and mix it thoroughly with 

 the gastric secretion. When the pylorus relaxes, how- 

 ever, these same waves serve to push the gastric contents 

 into the duodenum. What now determines this periodic 

 opening and closing of the sphincter? 



HIRSCH 4 observed in 1893 that when an acid is intro- 

 duced into the duodenum through a duodenal fistula the 

 escape of the gastric contents from the stomach is delayed 

 for some time. SERDJUKOW 5 confirmed this finding in 1899. 

 About the time of HIRSCH'S observations, PENZOLDT found 



1 EWALD and BOAS: Virchow's Archiv, 1885, CI, p. 364. 



2 PENZOLDT. Deut. Arch. f. klin. Med., 1893, LI, p. 545. 



3 CANNON: Am. Jour, of Physiol., 1898, 1, p. 368. 



4 HIRSCH: Centralblatt fur klin. Medizin, 1893, XIV, p. 73. 



5 SERDJUKOW: Russian dissertation reviewed in Hermann's Jahres- 

 bericht ub, d f Fortschritte d. Physiologic, 1899, VIII, p. 214, 



