MOVEMENTS OF THE ALIMENTARY CANAL. 729 



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

 first portion of food eaten entirely fills it and successive por- 

 tions find the wall layer occupied and are therefore received 

 into the interior. The ingestion of much liquid must interfere 

 somewhat with this stratification. Cannon* has reported some 

 interesting experiments upon the relative duration of gastric 

 digestion for carbohydrates, proteins, 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 

 carbohydrate food begins to pass out from the stomach soon after 

 ingestion, and requires only about one-half as much time as the pro- 

 teins for complete gastric digestion. Fats remain long in the 

 stomach when taken alone, and when combined with the other 

 foodstuffs markedly delay their exit through the pylorus. This 

 distinct difference in the main foodstuffs can hardly be referred to 

 mere mechanical consistency, since the fats are liquefied by the 

 heat of the body. Cannon has shown that this regulation is not 

 effected through the agency of the extrinsic nerves. After section of 

 the splanchnics and vagi the difference in time between the ejection 

 of carbohydrate and protein material still exists, so that the con- 

 trol in this matter must be exerted through some local mechanism 

 in the stomach itself. If, in a given diet, the carbohydrate is fed 

 before the protein, the former, having the position of advantage 

 toward the pyloric end, will be ejected promptly into the intestine, 

 while the protein is retained for gastric digestion. If the order is 

 reversed and the protein is fed first, the passage of the carbohydrate 

 out of the stomach will be retarded. This author has also reported 

 numerous interesting experiments, of medical and surgical interest, 

 which indicate that the motor activity of both stomach and intes- 

 tines may be greatly depressed by certain conditions, especially 

 by mechanical handling or by conditions of general asthenia. 



Regarding the general mechanism of the stomach, it may be 

 pointed out that it forms an admirably adapted apparatus for 

 receiving at once, or within a short period, a large amount of food 

 which it reduces to a liquid or semiliquid condition, partly by 

 digestion, partly mechanically, and that it charges the intestine 

 at intervals with small amounts of this chyme in such a condition 

 as to admit of rapid digestion. It seems obvious that without the 

 stomach our mode of eating would have to be changed, as it would 

 not be possible to load the intestine rapidly with a large supply of 

 food such as is consumed at an ordinary meal. 



* Cannon, "American Journal of Physiology," 12, 387, 1904. For a 

 general review of Cannon's work, see "American Journal of the Medical 

 Sciences," April, 1906. 



