CHAP. XI.] PROCESSES OF SMALL INTESTINE RECAPITULATED. 443 



ministered to a large dog, 49d c.c. were expelled in the succeeding 

 20 minutes; .in another, 25 minutes after the administration of 500 c.c., 

 495 c.c. were expelled. 



Experiments further proved that a state of repletion of the small 

 intestine reflexly slows the evacuation of the stomach, and that psychical 

 excitement also inhibits its evacuation. 



By further observations, v. Mering shewed that when water 

 holding C0 2 in solution is introduced into the stomach the gas is 

 abundantly absorbed. Alcohol he found to be abundantly absorbed. 

 Grape-sugar, milch-sugar, cane-sugar, and maltose, when in solution 

 in water, are all absorbed by the stomach in considerable quantities, 

 and in larger quantities when in alcoholic solution. Dextrin and 

 peptone are absorbed by the stomach, but in smaller quantities than 

 the sugars. The quantity of the bodies absorbed increases with the 

 concentration of the solutions. Pari passu with the process of 

 absorption of the bodies above named, there occurs an excretion of 

 water by the stomach which is active in proportion to the amount of 

 substance absorbed. 



Recapitulation of the Chemical Processes occurring in the Small 



Intestine. 



We have seen that, at rhythmically recurring intervals, during 

 the process of gastric digestion, the fluid part of the contents of the 

 stomach is, little by little, expelled into the duodenum. Ultimately 

 (see p. 159) the more or less diffluent 'chyme,' containing both 

 soluble constituents which had escaped absorption in the stomach 

 and insoluble constituents not yet acted upon, is forced through the 

 pylorus. Coming into contact with the bile and the pancreatic juice, 

 peptic digestion comes to an end and digestion by trypsin commences. 

 The proteids which had escaped the action of the gastric juice now 

 succumb to the action of trypsin. The digestion of the starches, 

 which had been arrested in the stomach, recommences under the 

 influence of the diastatic ferment of the pancreas, and the maltose 

 thus formed has to be resolved into simpler saccharine molecules by a 

 ferment-product of the intestinal wall ; these molecules must yet, in 

 part, still further be resolved under the influence of lactic acid producing 

 micro-organisms which they encounter. The fats, under the influence 

 of the bile aided by the pancreatic juice, are rapidly emulsified. As 

 these various operations go on, the contents of the intestine undergo 

 a great and rapid diminution, owing to the absorption of water, holding 

 the diffusible products of digestion in solution, and to the passage of 

 the minutely-subdivided fats through the intestinal walls. 



Thedestmc- As the acid chyme penetrates into the duodenum 



tion of pepsin. ^ Unc [ er g 0es a t O rice a change of reaction due to ad- 

 mixture with the pancreatic juice, the bile and the intestinal juice. 

 Its reaction becomes alkaline or at least ceases to be distinctly acid. 



