296 ISIDOR GREENWALD 



nuclein metabolism, involving, in some cases, a complete change of the 

 pentose in the body in less than twenty-four hours. 



It is most noteworthy that, of the more than thirty-five well-defined 

 cases of pentosuria, none approaches diabetes in severity. It is probable 

 that such severe cases do not exist, for, if they did, they should be the first 

 to be observed. The failure of carbohydrate metabolism, if it be such, is 

 never complete, nor even severe. At worst, it is only a slight impairment. 



It is remarkable that more attention has not been paid to the pos- 

 sibility of the formation of pentose from non-carbohydrate material. 

 Klercker observed that the diurnal curve of pentose excretion ran remark- 

 ably parallel with that of urea excretion, but he connected this only with 

 a possible derivation of pentose from the carbohydrate radical of protein, 

 glucosamin. He fed glucosamin to both his patients without affecting 

 the pentose excretion. He did not try other protein constituents. 



It appears to the author that the known facts regarding pentosuria are 

 best explained by the hypothesis that the condition is due to an anomaly 

 in the metabolism of one or more of the amino-acids. Those first to be 

 considered are those containing five or more carbon atoms in a straight 

 chain, such as leucin, normal a-aminocaproic acid, glutamic acid, lysin 

 or ornithin. This hypothesis is not contradicted by any known fact. It 

 is in harmony with the apparent differences in the character of the 

 pentoses excreted, with the optical inactivity of some and the activity of 

 others, and with the consistently small amounts excreted. The different 

 pentoses in the urine may be derived from different amino-acids. Direct 

 experimental evidence is lacking, but the hypothesis is presented in the 

 hope that those who may have the opportunity of studying cases of 

 pentosuria will put it to the test. 1 



Fructosuria 



Fructose. Recognition.- Soon after the introduction of polariscopic 

 examination of urine it was discovered that the observed rotation was 

 frequently less than that calculated from the content of reducing, or 

 fermenting, substance, assuming that to be glucose. The difference was 

 not due to the presence of protein and indicated the existence of a sub- 

 stance of unknown nature. Instead of recognizing clearly that nothing but 

 the difference between observed and calculated rotation was known, some 

 of the earlier observers assumed it to be due to the presence of fructose. 



1 Since the above was written, Cammidge and Howard have reported seven additional 

 cases o? pentosuria. Only one of these patients was a woman. Three were Jews, two 

 of whom were uncle and nephew. Two others were Greeks, father and son. The melt- 

 ing points of the various derivatives indicate that the pentose was inactive arabinoae 

 in all cases. The free sugar was isolated from the urine of three of the patients. In 

 the one patient studied, the excretion of pentose in the urine fell from 3.2 gm. per day 

 to 0.5 gm. as the protein intake was reduced and then gradually rose again as the 

 protein intake was increased. 



