CONVERSION OF GLYCURONIC ACID 321 



cretion are at times found associated with diabetes, has been 

 the basis for regarding oxalic acid as an end-product of 

 sugar catabolism: 



Sugar ^ Giycuronic Acid ^ Oxalic Acid. 



That oxalic acid may be an end-product of all sorts of sub- 

 stances has probably been the uncomfortable experience of 

 every chemist, who after having carried out some tiresome 

 oxidation experiment has time after time been able to obtain, 

 instead of the product he hoped for, only the inevitable and 

 unwelcome oxalic acid. Of course, then, it cannot be denied 

 that sometimes sugar may also be converted into oxalic acid 

 in the body. When and under what circumstances this is 

 true is, however, unknown ; and thus far all told there has 

 very little of a positive nature been obtained from the 

 many studies of the elimination of the relatively incom- 

 bustible oxalic acid in physiological and pathological 

 conditions. 54 



Conversion of Giycuronic Acid into X-xylose. A very im- 

 portant phase of the glycuronic acid question has been 

 previously referred to, the conjectural relation of the acid 

 with the tissue pentoses. From E. Salkowski's and C. Neu- 

 berg's discovery it is at least quite probable that the tissue 

 sugar with five carbon atoms, A-xylose, arises from 

 glycuronic acid by cleavage of C0 2 , and that the latter may 

 be thus converted into pentose by the agency of putrefactive 

 microorganisms : 



GLYCURONIC ACID X-XYLOSE 



COH COH 



H.C.OH H.C.OH. 



OH.C.H OH.C.H. 



> \ + CO, 



H.C.OH H.C.OH 



H.C.OH H.C.OH 



COOH H 



64 Literature upon Oxaluria: A. Magnus-Levy, Bd., 1, 155-159, 1906. 

 21 



