INTESTINAL JUICE 255 



6. INTESTINAL JUICE 



The intestinal juice of man is a thin, clear, alkaline fluid containing 

 epithelial cells, Bacteria and fat crystals, which effervesces on addition of 

 acids. Freed of solid bodies by means of the centrifuge, it contains from 0.2 

 to 0.5 per cent Na 2 C0 3 , 0.2-0.6 per cent 01, and about 1.1 per cent dry residue. 

 Its specific gravity is in the neighborhood of 1.007 (Hamburger and Hekma). 



Intestinal juice acts but feebly on starch. It inverts cane sugar, splits 

 maltose, and, in young animals at least, also milk sugar. According to Eoh- 

 mann and Nagano, the action of secreted intestinal juice on cane sugar and 

 malt sugar is much less than that of the intestinal mucosa: it might be 

 therefore that the cleavage of these sugars takes place in the mucosa itself, 

 or that mere contact with the surface of the mucous membrane is sufficient 

 for this purpose. 



Emulsified fats appear to be attacked to some extent by the intestinal juice. 



The native proteids, with the exception of casein and fibrin, are not 

 digested by the intestinal juice. On the other hand, an extract of the intes- 

 tinal mucosa in weakly alkaline or neutral reaction splits albumoses and pep- 

 tones into simpler compounds: NH 3 , leucin, tyrosin, lysin, arginin, histidin, 

 etc. (Cohnheim). This action is heightened by warming the solution, and 

 it is regarded therefore as the effect of a special enzyme called erepsin. The 

 normal secretion (man, dog) has the same effect, only to a less extent, from 

 which we may perhaps conclude that this cleavage of the primary products 

 of digestion really takes place in the mucous membrane. 



The nucleic acids are not decomposed by trypsin; but when they are 

 exposed to the action of erepsin they are split into phosphoric acid and the 

 purin bases. This fact speaks very strongly for the specific nature of erepsin 

 (Nakayama). 



Pawlow has discovered a new enzyme in the intestinal juice which he calls 

 enterolcinase, and which, as mentioned on page 252, transforms the raw mother- 

 substance of trypsin in the pancreatic juice into the active enzyme. We know 

 that this is not identical with erepsin from the fact that (in the human intes- 

 tinal juice) the latter is destroyed by a temperature of 59 0., whereas the 

 enter okinase is not destroyed below 67 0. 



Gachet and Pachon, as well as Glaessner, assert that the glands of Brunner, 

 which have an entirely different structure from that of the glands of Lieberkiihn, 

 secrete a proteolytic enzyme. 



The glands of the large intestine produce no enzymes, but secrete a mucus 

 which is of importance as a lubricant for the fecal mass. 



