DIGESTION 249 



intestine begins slowly, and continues at about the same 

 rate as their absorption or their passage onward into the 

 large intestine. Carbohydrates begin to leave the 

 stomach soon after their ingestion (within ten minutes). 

 They pass out with rapidity, and at the end of two hours 

 reach a maximum amount in the small intestine, almost 

 twice the maximum for proteins, and two and a half 

 times the maximum for fats, both of which maxima are 

 reached only at the end of four hours. Proteins 

 frequently do not leave the stomach at all during the 

 first half-hour, and, occasionally, not for an hour. The 

 initial departure of proteins from the stomach, therefore, 

 is much later than that of carbohydrates, and the rate of 

 discharge slower than that of either carbohydrates or 

 fats. The pylorus evidently permits the carbohydrates 

 not digested by the gastric juice to pass quickly into the 

 intestine, where they are digested, and retains the 

 proteins, digested in the stomach, there to undergo 

 digestion. When proteins are fed first, and carbo- 

 hydrates later, the proteins occupy the pyloric end of 

 the stomach, and the carbohydrates lie mainly in the 

 cardiac end. Under these circumstances the presence of 

 the proteins near the pylorus causes a characteristic 

 slow discharge, which thereby checks the carbohydrate 

 departure. If, on the other hand, the carbohydrate is 

 fed first, it passes on at once to the small intestine for 

 further digestion and absorption, and the protein remains 

 to undergo the changes produced by the stomach. It 

 would seem from these experiments that the American 

 breakfast, in which the cereal precedes the meat, has a 

 rational and physiologically economic arrangement ; and 



