228 



INTESTINAL DIGESTION. 



possessing digestive powers. The epithelium contains mucus- 

 secreting or goblet-cells, and their product is principally mucus. 



Succus Entericus or Intestinal Juice. This is the secre- 

 tion of all the glands of the small intestine ; but the follicles of 

 Lieberkiihn, being vastly more numerous than the others, con- 

 tribute by far the greater part of the fluid. It is obtained from 

 animals by making a " Thiry-Vella fistula." This consists in 

 cutting out a piece of intestine, from 10 to 30 cm. long, without 

 interfering with its nerves or blood-supply, and sewing the open 

 ends to two openings in the abdominal wall. The severed ends 

 of the intestine, from which the piece has been isolated, are also 



sewn together. The fluid ob- 

 tained from the portion thus iso- 

 lated is pure intestinal juice, with- 

 out admixture with food or other 

 substances. This operation has 

 been performed on the dog, and 

 the juice obtained is described as 

 being limpid, yellowish, having a 

 specific gravity of 1010, and a 

 strongly alkaline reaction, due to 

 the presence of sodium carbonate. 

 The fluid has also been ob- 

 tained from a human being, from 

 a piece of intestine 9 cm. long, 

 situated about 20 cm. above the 

 ileocecal valve. The daily prod- 

 uct averaged 27 c.c. The spe- 

 cific gravity averaged about 1007. 

 The fluid was opalescent and often 

 of a brownish color. It was always alkaline, and when treated 

 with acids carbonic acid gas was evolved. It gave all the proteid 

 reactions, but did not reduce Fehling's solution or change the 

 color of a solution of iodine. 



Action of Intestinal Juice. Although the chemical composition 

 of this fluid is not well understood, it is, nevertheless, known to 

 possess several enzymes : amylolytic, sugar-splitting, and activating 

 (p. 119). The amylolytic enzyme changes starch to maltose, and 

 possibly some dextrose. It has been claimed that the maltose is 

 converted into glucose by the product of Peyer's patches. Another 

 enzyme, invertin or invertase, changes saccharose into dextrose and 

 levulose. The changes undergone in this process have been 

 already described (p. 93). The succus entericus contains no pro- 

 teolytic enzyme, nor is fat split up by it. Its alkalinity aids in 

 the emulsification of fats. The activating enzyme is enterokinase, 

 which changes trypsinogen into trypsin. 



FIG. 123. Mucous membrane of the 

 jejunum (Testut) : 1, Peyer's patch; 

 2. its border ; 3, solitary follicles ; 4, 4, 

 valvulse conniventes. 





