EXPERIMENTAL DIABETES 375 



and, finally, whether proteid itself, apart from its carbohydrate 

 group, may not, under certain conditions, behave similarly. 



In this review some repetition will be unavoidable, and several 

 observations from the clinical study of diabetes in man, not yet con- 

 sidered in this article, will be cited to assist us in our conclusions. 



With regard to its derivation from a pre-formed carbo- 

 hydrate group in the proteid molecule. 



When other forms of proteid, and more especially the proteids 

 of blood serum, were examined for carbohydrate groups by Pavy's 

 method, much smaller yields were obtained than in the case of 

 egg proteid, and indeed in some proteids (e.g. casein) no carbo- 

 hydrate group at all could be detected. 



The carbohydrate group separable from egg proteid and from 

 serum proteid and from several other varieties of proteid is, more- 

 over, not dextrose, but glucosamin. Before any role in glycogen 

 or dextose formation could be ascribed to this substance, it would 

 be necessary to show that it can give up its amido (NH 2 ) group in 

 place of a hydroxyl (OH) group, so as to produce a nitrogen-free 

 sugar chitose. In the laboratory, this substitution can be brought 

 about (see p. 316), but there is no certain evidence that it 

 occurs in the animal body. Glucosamin, given by the mouth in 

 large doses, passes in part at least into the urine unchanged, and 

 does not seem to lead to the deposition of glycogen in the tissues. 

 Such a result must not of course be considered as furnishing a 

 final answer to our question, for, as Langstein points out, it is 

 quite conceivable that the glucosamin liberated in the organism 

 itself (i.e. of endogenous origin) is susceptible to quite a different 

 metabolic process from glucosamin introduced from without (i.e. 

 of exogenous origin). 



In this connection it is also of interest to note that there is 

 much evidence that the process of denitrification of amido bodies 

 can be carried out by living cells ; thus Hopkins and Cole have 

 recently shown that if anaerobic bacteria be grown in the presence 

 of tryptophane (skatol amido-acetic acid) they cause the amido 

 group (NH 2 ) to be eliminated and leave behind skatol-acetic acid. 

 Jones and others have also shown that amido-purins can be con- 

 verted into oxy-purins by a denitrifying ferment, and as is ex- 

 plained elsewhere, there is no doubt that this denitrification of 

 amido-purins is constantly going on in the body. 



There is also some indirect evidence that glucosamin can form 



