TEXT-BOOK OF PHYSIOLOGY 



time to time and the passage of the protein into the duodenum begins and 

 gradually increases in rapidity until the maximum speed is attained, about 

 two hours after ingestion; from this time on, the speed of discharge gradually 

 diminishes until the end of the observation period. 



When fat, e.g., beef, mutton, or pork fat, is administered, they remain 

 in the stomach for some time and when they begin to leave, the rate of dis- 

 charge is so slow that they are digested and absorbed almost as fast as 

 discharged and hence seldom accumulate in the small intestine. These 

 compounds delay the secretion of gastric juice and therefore free hydrochloric 



acid, the presence of which appears to be neces- 

 sary for the relaxation of the pyloric sphincter. 

 When carbohydrates, e.g., starch paste, boiled 

 rice, boiled mashed potatoes are administered, 

 their discharge begins shortly after their entrance 

 into the stomach; they [pass out rapidly, the 

 velocity of discharge reaching its maximum at 

 the end of two hours, after which the speed de- 

 clines to the end of the observation period. The 

 reason for the early and rapid discharge is to be 

 found in the fact that while the carbohydrates 

 excite the secretion of gastric juice they do not 

 absorb the hydrochloric acid to any appreciable 

 extent. A combination of equal quantities of 

 protein and carbohydrate varies the rate of dis- 



Ant 



Left 



FIG. 74. SHADOW SKETCHES 

 OF THE OUTLINES OF THE STOMACH 

 OF A CAT IMMEDIATELY AFTER A 

 MEAL (n.o), AND AT VARIOUS IN- 

 TERVALS AFTERWARD (AT 12.0, AT 

 2.0, 3.30, 4.30). (W. B. Cannon.} 



Post 



FIG. 75. The cardiac portion is all that part to the 

 left, as the stomach lies in the body, of W X. The cardia 

 is at C. The pylorus is at P, and the pyloric portion is 

 the part between P and WX. This has two divisions: 

 the antrum, between P and YZ, and the preantral part, 

 between WX and YZ. The lesser curvature is on the top 

 of the outline between C. and P, and the greater curva- 

 ture between the same points along the lower border. 

 (Amer. Jour, of Physiology, Cannon^} 



charge of each separately. Thus under these circumstances the carbohy- 

 drates are not discharged so rapidly nor are the proteins detained so long as 

 usual; a combination of fat with either protein or carbohydrate delays the 

 time of discharge of both. From these facts it may be inferred that the 

 time any given food remains in the stomach will depend on its chemic com- 

 position or the relative amounts of its contained protein, fat, and carbo- 

 hydrate principles. 



Movements of the Stomach. During the period of gastric digestion 

 the muscle walls of the stomach become the seat of a series of movements, 

 usually described as peristaltic in character, which not only incorporate the 



