642 PHYSIOLOGY OF DIGESTION AND SECRETION. 



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 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 be- 

 comes 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 

 especially those of Griitzner,* 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. Griitzner 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 

 gi S succeeding portions were arranged 



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

 colored differently: first, black; sec- & . J 



ond, white (indicated by vertical centnC fashion, as shown in the 



marking); third, red (indicated by r* n -i / 



transverse marking). figure. Such an arrangement of 



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 

 stratification. Whether the fact of this stratification has any 

 hygienic bearing with regard to the most desirable sequence in our 

 articles of diet is not yet apparent. Cannonf has reported some 

 interesting experiments upon the relative duration of gastric 

 digestion for carbohydrates, proteids, and fats when fed separately 

 and combined. The foods were mixed with subnitrate of bismuth 

 and their position in the stomach and passage into the intestine 

 were watched by means of the Roentgen rays. It was found that 



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

 t Cannon, "American Journal of Physiology," 12, 387, 1904. 



