vi INTESTINE AS AN OEGAN OF EXCEETION 355 



forming daily 14-5 grins, faecal matter, consisting largely of 

 katabolites eliminated by the intestinal crypts. 



Fritz Voit's results further show that the nitrogen of the faeces 

 formed during a moderate flesh diet comes, not from the alimentary 

 residues, but almost exclusively from the intestinal secretions. 

 The ash of the ingested flesh, on the contrary, is not completely 

 absorbed, and partially mixes with the faeces. Lastly, he finds 

 that along with the waste nitrogenous products and a moderate 

 quantity of salts, the isolated intestine also excretes a not in- 

 considerable amount of fatty substances, which constantly appear 

 in the faeces. 



Fritz Voit also attempted to solve the problem of the absorption 

 and elimination of lime and iron. It is known that for adults the 

 quantity of lime introduced with the food is usually in excess of 

 what is required to maintain the calcium-balance in the body. 

 The question then arises as to whether the excess of lime is 

 absorbed or not, and if it is eliminated by the kidneys or by the 

 intestine. 



The experiments made on dogs show that with a normal mixed 

 diet, particularly when rich in calcium, the greater part of the 

 lime salts present in the faeces come directly from the food. A 

 certain proportion of the calcium salts eliminated from the body 

 are, however, secreted in the intestinal tube, as shown by the 

 calcium content of the faeces in fasting. This secretion of lime in 

 an isolated segment of intestine increases somewhat with feeding ; 

 but the increment is very slight, even on a diet rich in calcium. 

 In this case the lime salts excreted with the urine also increase 

 in a moderate degree, which leads us to the conclusion that most 

 of the excess lime introduced is not absorbed, but mixes with, and 

 is eliminated in, the faeces. 



As regards the absorption and elimination of iron, the results 

 of experiment lead us to conclude that its absorption in the 

 digestive canal is small ; that what is absorbed is eliminated to a 

 small extent by the kidneys, more by the intestine, least by the 

 liver; that, lastly, the small amount of iron eliminated with the 

 bile is mainly reabsorbed by the intestine. 



Since little of the iron of the food is absorbed, the amount 

 excreted by the intestine and mixed with the faeces is also small 

 (a few milligrammes only). Most of the iron found in the faeces 

 comes directly from the food. 



IV. Other interesting contributions to the theory of the 

 excretory function of the intestine were published from the 

 Institute of Hygiene at Prague by Prausnitz, Moeller, and 

 Kermauner (1897). 



From a series of careful microscopic investigations of human 

 faeces during an ordinary mixed diet, Moeller concluded that, 

 given a perfectly healthy condition of the digestive apparatus, 



