CHAPTER XII 



THE FINAL DECOMPOSITION OF FOODSTUFFS IN THE BODY 



As already mentioned at page 27, the foodstuffs in their combustion do 

 not pass over immediately into their end products, but are gradually split 

 up into simpler and simpler substances, oxidation and reduction processes 

 probably succeeding each other in rapid succession. In order to secure more 

 light on these processes, investigators have studied the transformations which 

 organic substances, more or less closely related to the foodstuffs, undergo in 

 the body. Important as these investigations are, and significant as are the 

 results which we expect from this field in the future, we must limit ourselves 

 here, for want of space, to the transformations of the true foodstuffs. Un- 

 fortunately our knowledge of these subjects is still very imperfect and the 

 views of authors are considerably at variance with one another on many of 

 the most important points. 



1. THE FINAL DESTRUCTION OF PROTEID 



In its digestion in the alimentary canal, proteid is for the most part split 

 up into relatively simple products. To what extent it is absorbed in the 

 form of albumoses and peptones we cannot say definitely. Nor is anything 

 known concerning the extent to which synthesis of proteid from the end 

 products just named eventually takes place in the body. If the proteid is 

 not stored, both the primary and the final digestive products are still further 

 decomposed until the elements of proteid are ready to be eliminated as carbon 

 dioxide, water and urea. 



Formerly it was supposed that proteid in its decomposition is split up 

 into a nitrogenous and a nonnitrogenous portion. This view however is no 

 longer tenable, for from the fact that numerous nitrogenous compounds appear 

 successively in the hydrolytic cleavage of proteid, it follows that the final 

 separation of the carbon from the nitrogen takes place at a very late stage 

 of the process. 



In the body proteid and its digestive products do not undergo a continuous, 

 progressive cleavage by oxidation. There undoubtedly eccur a number of 

 synthetic processes by which the groups contained in the proteid molecule 

 undergo many changes of position of one kind and another. Hence, the 

 problem of the decomposition of proteid in the body is extremely complicated 

 and cannot be regarded as by any means solved. 



In the destruction of proteid by chemical reagents outside the body a 

 certain quantity of urea is formed, which comes from arginin, not by oxida- 



