146 DIGESTION. 



in opening the abdomen, any such energetic or extensive contrac- 

 tions of the stomach, even when full of food, as may be easily 

 excited in the small intestine by the mere contact of the atmosphere, 

 or by pinching them with the blades of a forceps. This action of 

 the stomach, nevertheless, though quite gentle, is sufficient to pro- 

 duce a constant churning movement of the masticated food, by 

 which it is carried back and forward to every part of the stomach, 

 and rapidly incorporated with the gastric juice which is at the 

 same time poured out by the mucous membrane ; so that the 

 digestive fluid is made to penetrate equally every part of the ali 

 mentary mass, and the digestion of all its albuminous ingredients 

 goes on simultaneously. This gentle and continuous movement of 

 the stomach is one which cannot be successfully imitated in experi- 

 ments on artificial digestion with gastric juice in test-tubes ; and 

 consequently the process, under these circumstances, is never so 

 rapid or so complete as when it takes place in the interior of the 

 stomach. 



The length of time which is required for digestion varies in 

 different species of animals. In the carnivora, a moderate meal of 

 fresh uncooked meat requires from nine to twelve hours for its 

 complete solution and disappearance from the stomach. According 

 to Dr. Beaumont, the average time required for digestion in the 

 human subject is considerably less ; varying from one hour to five 

 hours -and a half, according to the kind of food employed. This 

 is probably owing to the more complete mastication of the food 

 which takes place in man, than in the carnivorous animals. By 

 examining the contents of the stomach at various intervals after 

 feeding, Dr. Beaumont made out a list, showing the comparative 

 digestibility of different articles of food, of which the following are 

 the most important : 



Time required for digestion, according to Dr. Beaumont : 



KIND OF FOOD. HOURS. MINUTES. 



Pig's feet 1 00 



Tripe 1 00 



Trout (broiled) 1 30 



Venison steak 1 35 



Milk 2 00 



Roasted turkey 2 30 



" beef 3 00 



" mutton 3 15 



Veal (broiled) 4 00 



Salt beef (boiled) 4 15 



Roasted pork ........ 5 15 



