DIGESTION IN THE INTESTINE 295 



With regard to the extent of digestion of proteids in the intestine, Zunz 

 has found that in the uppermost 50 cm. of its length the relative quantities 

 of albumose and end products varies in favor of the latter, the longer diges- 

 tion continues. After four hours, the nitrogen in the form of albumose 

 amounts to seventy-six to ninety-five per cent of the total nitrogen; after six 

 hours, seventy-one to eighty-three per cent; after eight hours, forty-four to 

 forty-six per cent; and after ten hours, thirty-two to forty-four per cent. 

 The end products increase therefore with the duration of digestion. We 

 cannot draw from this any positive conclusion as to the form in which the 

 digested proteid is chiefly absorbed, for it might very well be that the albu- 

 moses are more quickly absorbed from the intestine than are the end products. 

 We shall discuss this question more fully in our study of absorption. 



Proteid and its digestive products are attacked also by the Bacteria pres- 

 ent in the intestine. To judge from observations on men with intestinal 

 fistula?, this action is only very slight; and this is probably the reason why 

 the contents of the small intestine have no fecal odor. In the large intes- 

 tine the Bacteria act much more extensively on the proteid, and as a result 

 we find there besides carbon dioxide and marsh gas, sulphureted hydrogen, 

 methyl mercaptan, skatol, phenol, etc., which give the faeces their character- 

 istic odor. The bile pigments are destroyed in the large intestine by Bacteria, 

 and bilirubin is changed into sterkobilin, which is probably identical with 

 urobilin. 



The putrefactive products arising in the intestine, which in so far as they 

 are basic in character (like cholin and the different uric acid and creatin deriva- 

 tives), are called leucomaines, are taken up by the blood and are there changed 

 by chemical reactions into relatively harmless substances, and are finally elimi- 

 nated in the urine. Formed in too large quantities and absorbed, however, they 

 may remain in the body and cause a kind of poisoning, autointoxication, which 

 produces more or less profound disturbances of the system. 



Moreover, the body strives in many ways to overcome all kinds of poisonous 

 substances which may be taken up with the food. Some are not absorbed from 

 the intestine, some, as in the case of the different Bacterial decomposition prod- 

 ucts, are destroyed by the digestive fluids, some are retained and rendered 

 innocuous by the liver and the meseiiteric glands. It is plain that these proc- 

 esses, which cannot be discussed more fully here, are of the very greatest im- 

 portance for the body, although the protection provided by them is not in all 

 cases sufficient to save the body from poisoning. 



Until recently it was rather generally assumed that fat is partly broken 

 down by the pancreatic juice into the fatty acids and glycerin, that the former 

 unite with the alkalies of the intestine to form soaps, and that the soaps 

 bring about an emulsification of the fat. On account of its alkalies bile was 

 said to play a prominent part. Unlike the other nutritive substances fat 

 would then pass from the intestinal cavity into the mucous membrane, not 

 in solution but in the form of an emulsion. The following two facts support 

 this view: rancid fat is emulsified easily by alkalies, and the absorption of 

 fats from the intestine is very considerably reduced by exclusion of the bile. 



But by more exact investigation of the phenomena accompanying absorp- 

 tion of fat several facts have come to light which speak strongly against this 



