290 DIGESTION. 



previous and subsequent to the meal, gentle exercise being 

 favourable, over-exertion injurious to digestion ; the state 

 of mind tranquillity of temper being apparently essential 

 to a quick and due digestion : the bodily health : the state 

 of the weather. But under ordinary circumstances, from 

 three to four hours may be taken as the average time 

 occupied by the digestion of a meal in the stomach. 



Dr. Beaumont constructed a table showing the times 

 required for the digestion of all usual articles of food in 

 St. Martin's stomach, and in his gastric fluid taken from 

 the stomach. Among the substances most quickly digested 

 were rice and tripe, both of which were chymified in an 

 hour ; eggs, salmon, trout, apples, and venison, were 

 digested in an hour and a half; tapioca, barley, milk, 

 liver, fish, in two hours ; turkey, lamb, potatoes, pig, in 

 two hours and a half; beef and mutton required from 

 three hours to three and a half, and both were more 

 digestible than veal ; fowls were like mutton in their degree 

 of digestibility. Animal substances were, in general, con- 

 verted into chyme more rapidly than vegetables. 



Dr. Beaumont's experiments were all made on ordinary 

 articles of food. A minuter examination of the changes 

 produced by gastric digestion on various tissues has been 

 made by Dr. Eawitz, who examined microscopically the 

 product of the artificial digestion of different kinds of 

 food, and the contents of the faeces after eating the same 

 kinds of food. The general results of his examinations, 

 as regards animal food, show that muscular tissue breaks 

 up into its constituent fasciculi, and that these again are 

 divided transversely ; gradually the transverse striae become 

 indistinct, and then disappear ; and finally, the sarcolemma 

 seems to be dissolved, and no trace of the tissue can be 

 found in the chyme, except a few fragments of fibres. 

 These changes ensue most rapidly in the flesh of fish and 

 hares, less rapidly in that of poultry and other animals. 

 The cells of cartilage and fibro-cartilage, except those offish, 



