324 



ESSENTIALS OF PHYSIOLOGY. 



B 



THE COMPOSITION OF THE INTESTINAL JUICE. 



Intestinal juice is obtained, like the other digestive secretions, by 

 means of a fistula. A segment of intestine of sufficient length is 

 separated by incisions ; one end of the separated portion is closed by 

 sutures, and the open extremity is sutured into the abdominal wall, the 



continuity of the remainder 

 of the bowel being restored 

 by stitching the free ends 

 together. The detached 

 segment retains its normal 

 blood and nerve supply. 

 In another method, both 

 ends of the segment are 

 left open, and each is 

 sutured separately into the 

 abdominal wall (fig. 123). 



The juice obtained from 

 such a fistula has a specific 

 gravity of about 1010, and 

 is alkaline. It contains 1 

 to 2 per cent, of solids, 

 half of which ar,e organic 

 and half inorganic. The 

 organic solids consist 



^. mainly of serum albumin, serum globulin, and enzymes. The inorganic 

 substances are chiefly sodium chloride and sodium carbonate. 



THE FUNCTIONS OF THE INTESTINAL JUICE. 



It has already been pointed out that the intestinal juice converts 

 trypsinogen into trypsin by virtue of the enzyme, enterokinase, which it 

 contains, and also that another of its enzymes, maltose, shares with a 

 similar ferment in the pancreatic juice the function of completing the 

 digestion of starch by converting maltose into dextrose. The 

 intestinal juice also contains two enzymes which convert the di- 

 saccharides, cane sugar and lactose, into monosaccharides. One of 

 these ferments, invertase, converts a molecule of cane sugar into one 

 molecule of dextrose and one molecule of fructose. The other, lactase, 

 hydrolyses lactose in a similar way into dextrose and galactose. Lactase 

 is most abundant in young animals, at the period of life when lactose 

 is an important constituent of the dietary. The terminal stages of 

 the hydrolysis of protein are effected by a ferment, erepsin, existing in 



FIG. 123. Scheme of intestinal fistula. 

 A, first stage of operation ; B, fistula completed. 



