MOVEMENTS OF THE ALIMENTARY CANAL. 663 



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 observations, 

 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. This fact is of impor- 

 tance in connection with the salivary 

 digestion of the starchy foods. 

 Obviously salivary digestion may 

 proceed for a long time 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 

 food first taken lay next to the 

 walls of the stomach, while the stom S of 2 ^rS g n 

 succeeding* portions were arranged show the stratification of food given 



i i . i . . at different times. (Grutzner.) The 



regularly in the interior in a COn- food was given in three portions and 



j. i -, . , colored differently : first, black ; sec- 



CentriC fashion, as Shown in the ond, white (indicated by vertical 



d "" 



figure. Such an arrangement of SSSSSj S&3? 



the food is more readily understood 



when one recalls that the stomach has never any empty space 

 within; its cavity is only as large as its contents, so that the first 

 portion of food eaten entirely fills it and successive portions find 

 the wall layer occupied and are therefore received into the interior. 

 The ingestion of much liquid must interfere somewhat with this 

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



