722 PHYSIOLOGY OF DIGESTION AND SECRETION. 



gastric secretion. Solid objects forced against the pylorus prevent 

 relaxation and retard the passage of the chyme into the intestine. 

 When liquid food alone is taken into the stomach numerous ob- 

 servations, made by means of intestinal fistulas, prove that the 

 material may be forced into the duodenum within a few minutes. 

 Hydrochloric acid in the stomach seems to favor or produce a 

 relaxation of the pyloric sphincter, while in the duodenum, on the 

 contrary, it causes a contraction of the sphincter. In this way it 

 may be imagined that after each ejection of acid chyme the sphinc- 

 ter is kept closed until the acid material in the duodenum is neutral- 

 ized, and so, automatically, a mechanism is provided by means of 

 which the duodenum is charged at intervals and at such times as it 

 is prepared to receive and neutralize a new quantity of the chyme. 

 According to this description, the portion of the food toward the 

 pyloric end of the stomach is the first to be thoroughly mixed with 

 the gastric juice, and to be broken down partly by digestion and 

 partly by the mechanical action of the contractions. This portion, 

 as it is liquefied, is expelled, and its place is taken by new material 

 forced forward from the fundic end. It would seem that this latter 

 portion of the stomach is in a condition of tone, and the pressure 

 thus put upon the contents is sufficient to force them slowly toward 

 the pyloric end as this becomes emptied. The older view was that 

 the contents of the stomach are kept in a general rotary movement 

 so as to become more or less uniformly mixed; but Cannon's obser- 

 vations, and also those of Grutzner,* indicate that the material at 

 the fundic end may remain undisturbed for a long time and thus 

 escape mixture with the acid gastric juice, so far at least as the 



interior of the mass is concerned. 

 This fact is of importance in con- 

 nection with the salivary digestion 

 of the starchy foods. Obviously, 

 salivary digestion may proceed for 

 a time in the fundic end without 

 being affected by the acid of the 

 stomach. Grutzner fed rats with 

 food of different colors and found 

 that the successive portions were 

 arranged in definite strata. The 



tO the 



food was i given in three portions and Walls of the Stomach, while the 

 colored differently: first, black; sec- ,. 



ond, white (indicated by vertical succeeding portions were arranged 



marking); third, red (indicated by i i ,1 , 



transverse marking). regularly in the interior in a con- 



centric fashion, as shown in the 



figure. Such an arrangement of the food is more readily understood 



when one recalls that the stomach has never any empty space 



* Grutzner, "Archiv f. die gesammte Physiologie," 106, 463, 1905. 



