URINE. 101 



and variable quantities. The most important of these are 

 the pentoses, glycuronates, and possibly dextrose. It is 

 still debatable whether dextrose is present in the urine under 

 absolutely normal conditions, or, better, under conditions 

 which do not permit of the slightest suspicion that the renal 

 function is impaired. If it does exist in the urine in such 

 cases, it is present in amounts which escape detection by the 

 usual methods. 



PENTOSES. 



As the methods for isolation and identification of the 

 pentoses improve, the presence of these substances in the 

 urine is being more frequently noted. Xylose, Arabinose, 

 and Rhamnose (methyl-pentose) have been described. They 

 originate in the organism after the ingestion of cherries, 

 plums, grapes, etc., which contain the mother substances 

 of the pentoses, the pentosanes. The pentoses are not 

 readily assimilable, and when ingested appear in part un- 

 changed in the urine. It must be remembered that the 

 tests which were given for pentoses (p. 3) are not abso- 

 lutely characteristic for these substances, since glycuronic 

 acid and related bodies also react positively with them. 

 The reactions may be used, nevertheless, as confirmatory tests 

 if the polarization and fermentative power of the urine are 

 also determined. The pentoses found in the urine are non- 

 fermentable and inactive toward polarized light, while the 

 glycuronates are Isevogyrate. 



(a) Test the urine in the polariscope. 



(6) Try the orcinol and phloroglucinol tests with 10 c.c. 

 of urine. 



(c) Heat to boiling 4-5 c.c. of Bial's reagent and then 

 add a few drops of the urine. 



