. ELEMENTARY PHYSIOLOGICAL CHEMISTEY 273 



Unlike the two previous forms the percentage of sugar in the blood 

 is normal, or even sub-normal. On this account, it is supposed that 

 phloridzin produces glycosuria by disturbing the controlling mechanism 

 of the kidney, whereby the latter allows too much dextrose to escape into 

 the urine, in consequence of which the percentage tends to become 

 sub-normal in the blood. Increased demands are therefore made on 

 the stored up glycogen, which at last becomes used up, and then the 

 supply has to be furnished by the proteids, and these break down. 

 In both pancreatic and phloridzin diabetes, therefore, proteid is split 

 into its nitrogenous and carbonaceous moieties, and these appear in the 

 urine, the former as urea, the latter as- dextrose. 



The other sugars which the urine may contain are lactose and 

 pentose. The former of these is sometimes found in the urine of 

 nursing mothers, and the latter appears in the urine whenever pentoses 

 (Wood Sugars, p. 417) are given in the food. 



Tests for Dextrose in the Urine. The tests for dextrose, as 

 described, can, with slight modifications, be applied to its detection 

 in urine. 



The most important of these are : 



EXPERIMENT V. Trommer's Test. Make 5 c.c. urine strongly 

 alkaline with strong KOH solution, then add copper sulphate solution 

 to it a drop at a time, shaking vigorously between each addition, until 

 a trace of cupric hydrate remains undis solved. Heat to near boiling. 

 A red precipitate of cuprous oxide forms if dextrose be present. 1 



EXPERIMENT VI. Fehling's Test. Boil 5 c.c. of Fehling's solution 

 in order to ascertain that the Rochelle salt which it contains, has not 

 decomposed into reducing bodies. If no reduction occur, add a drop of 

 the suspected urine and boil again. If no result, go on adding 

 small quantities, boiling between each addition, till 5 c.c. have been 

 added. If no reduction now ensue no pathological amount- of sugar can be 

 present. 



A negative result with either of these tests excludes the presence of 

 dextrose, although a positive result does not necessarily imply that it 

 is present, since there are several other bodies in urine, e.g. uric acid, 

 creatinine, glycuronic acid, etc., which are capable of reducing metallic 

 oxides in alkaline solution. 



1 The slight excess of cupric hydrate also becomes reduced. If the urine con- 

 tain much ammonia (e.g. after standing some time) it will dissolve a large amount 

 of cupric hydrate, so that this part of the reaction (the ^resolution of cupric 

 hydrate) is no indication of the presence of dextrose. In such urines, too, the 

 cuprous oxide formed by reduction will also become dissolved, and a colourless 

 solution instead of a red precipitate will result. 



