CHAP. XXIV.] KATE OF STOMACH DIGESTION. 209 



years ago by Sir B. C. Brodie, and with great kindness placed at 

 our disposal by him, we find the following statement : ' ' when 

 dogs were fed on lard, the lard passed into the small intestine 

 unchanged." 



It would seem to be the most reasonable conclusion which we 

 can deduce from the preceding statements, that in man and the 

 carnivora the fluid secreted by the stomach during digestion simply 

 dissolves animal and vegetable substances of the azotised kind 

 without altering their chemical constitution, leaving amylaceous, 

 oily, saccharine, and the allied substances but little or not at all 

 acted upon. 



The Chyme. The mass that is contained in the stomach after 

 digestion has been going on for four or five hours, and which is 

 commonly known by the name of chyme, consists of aliments dis- 

 solved, or softened and prepared for solution or other change by the 

 gastric juice. As they are mostly of the same kind, this mass 

 presents a homogeneous appearance, except when substances are 

 present which either require a longer sojourn in the stomach or are 

 only digestible by some lower portion of the intestinal tube. 



Rate of Stomach Digestion. The process of stomach digestion is 

 a slow one. In the artificial digestions above referred to, it took 

 from eight to twelve hours to produce any marked effect upon 

 the pieces of meat and albumen submitted to the action of the 

 digestive fluid. This, however, is much longer than the natural 

 process. According to Dr. Beaumont's researches upon Alexis St. 

 Martin, it took three or four hours before the stomach became empty 

 after a meal, consisting chiefly of azotised food and his tables show 

 that the mean time required for the digestion of the principal 

 animal substances in common use, such as butcher's meat, fowl, 

 game, was from two hours and three-quarters to four hours. 



In experiments on dogs, it has been found by most experimenters 

 that no great advance in the solution of the contents of the sto- 

 mach is made under from two to four hours. Gosse, who possessed 

 the power of disgorging the contents of his stomach by previously 

 swallowing a quantity of air, found that no change had taken place 

 in the food after it had remained half an hour in the stomach : after 

 the lapse of an hour he found the food much softened but not 

 reduced in weight : while, after two hours, it was not only much 

 softened but considerably reduced in quantity, so that he could not 

 return from his stomach more than half what he had taken.* 



Purkinje and Pappenheim found, in their experiments upon 

 * (Euvres de Spallanzani, par Senebier, t. ii. 



