234 FORMATION OF SUGAR FROM PROTEIN 



suffice to cover even a small fraction of the large amount of 

 sugar which the body under certain circumstances is capable 

 of producing from protein. Before long, too, the previously 

 mentioned (v. sup., p. 231) fact became unexpectedly appar- 

 ent that the body, which, with a readiness that almost smacks 

 of play, performs so many chemical transformations that 

 put to shame the art of the chemist, is unable to bring about 

 the simple substitution of the amine group of glucosamine by 

 a hydroxyl radical; and that for this reason glucosamine 

 cannot be classed among the typical sugar- and glycogen- 

 formers. The logical conclusion was, therefore, that the 

 sugar which in human diabetes, pancreatic diabetes, phlorid- 

 zin-diabetes, etc., to all appearances originated from proteins 

 is not a direct hydrolytic protein cleavage-product, but must 

 be due to some more complicated chemical changes. 



Elimination of Sugar and Protein Decomposition. For 

 several decades a bitter controversy was waged upon the 

 question of accepting the reality of sugar being formed 

 from protein. Most prominent of all its opponents, Edward 

 Pfliiger, with an obstinacy here as inseparable from the char- 

 acter of this great physiologist as was his earnestness in the 

 search for the truth, never wearied of contesting by one new 

 ingenious argument after another against the doctrine of 

 sugar production from protein ; and yet in the end he was 

 unable to prevent the theory, well founded as it now is, from 

 taking a permanent place in our science. Today the details 

 of this controversy have no more than historical interest; 

 and there is no occasion for us to enter into the matter more 

 fully at this time. It will probably be sufficient to briefly 

 call to mind the steps by which we have come to know that 

 sugar may be formed from protein. 



For this we are indebted primarily to a long series of 

 metabolic researches upon human diabetes, and, too, upon 

 pancreatic diabetes and phloridzin diabetes in animals, with 

 which are prominently connected the names of Claude 

 Bernard, Kiilz, Wolfberg, Naunyn, v. Mering, Minkowski, 



