CHRONIC PENTOSURIA 291 



of the quantity of pentoses in the ingested nucleoproteids. 

 There is just as little reason to refer it to the pentoses in 

 combination in the tissue proteins, as the whole supply of 

 pentoses in the human body is estimated at only about ten 

 grams, while the amount of urinary pentose which may be 

 excreted in a single day may reach thirty grams or more. 

 Ingested xylose in a pentosuric (just as in a healthy person) 

 may at least in part pass into the urine. There is no more 

 evidence of connection between pentosuria and the metab- 

 olism of dextrose ; it is not influenced by total withdrawal of 

 carbohydrates, or by administration of phloridzin; and 

 glycuronic acid excretion takes place in normal measure, 

 according to Blumenthal and Bial, after administra'tion of 

 chloral or menthol. There is nothing left except to conclude 

 that the pentosuric individual synthesizes his urinary pen- 

 tose; where, how, or why, we do not know. Neuberg has 

 suggested a possible connection between galactose and 

 arabinose on the basis of their stereochemical molecular 

 configuration : 



.-GALACTOSE A-ARABINOSE 



C.OH COH 



H.C.OH H.C.OH 



OH.C.H OH.C.H 



OH.C.H OH.C.H. 

 H.C.OH CH 2 .OH 



CH 2 .OH 



Finally, Luzzatto 61 has shown in a case of pentosuria that 

 even the exhibition of large quantities of glucose, cane-sugar 

 or starch is incapable of modifying it in any way. If, how- 

 ever, galactose be given, it is in greater part decomposed, 

 but a small portion would seem to be transformed into 

 pentose and the amount of the five-carbon-atom sugar in- 



81 R. Luzzatto (Camerino), Arch. f. exper. Pathol., Schmiedeberg Festsehr., 

 1908, 366. 



