THE URINE 467 



necessary, extracted with amyl alcohol. The spectrum of acid haema- 

 toporphyrin can then be identified. 



Sugars in the Urine. The sugar which, under certain conditions, 

 appears in the urine is dextrose or glucose. Rarely levulose, lactose, 

 or pentose, may be excreted. 



Glycosuria is a symptom of the disease known as diabetes mellitus. 

 It does not follow, however, that every person who is found to have 

 dextrose in the urine has diabetes, although it is probable. Traces 

 of dextrose occur in normal urine, but not in sufficient amount to give 

 the tests for sugar as generally applied. Various other substances 

 in the urine, such as glycuronic acid, uric acid, creatinin, phosphates, 

 may give a positive reaction with Fehling's solution, which is the 

 test most frequently employed for the detection of dextrose. This is 

 a matter of considerable importance, for the presence of one or other 

 of these substances may lead to a false diagnosis of sugar in the urine, 

 a serious error, and one which falls particularly hard on candidates 

 for life insurance. Therefore, the tests for sugar in urine should 

 always be carefully applied. 



Trommer's test is not to be recommended, owing to the haphazard 

 proportions of the testing solutions copper sulphate and potash. 



Fehling's test is best applied by boiling the Fehling's solution and 

 the* urine in separate tubes, and then mixing the two. If reduction 

 occurs without further heating, it is almost certainly due to the 

 presence of dextrose in the urine. Glycuronic acid and compound 

 glycuronates, uric acid, creatinin, phosphates, do not cause reduction 

 under these conditions. 



A positive reaction obtained with Nylander's test is strongly con- 

 firmatory, for, besides sugar, only glycuronic acid and its compounds 

 will reduce the bismuth salt. 



The phenyl-hydrazine test helps to differentiate sugar, but the 

 most certain test of all is fermentation with yeast. This should 

 always be applied. 



An approximate estimate of the amount of sugar present in the 

 urine may be made by taking the specific gravity of the urine before 

 arid after it has been fermented with yeast for twenty -four hours. 

 Each degree of specific gravity lost equals 1 grain of sugar per ounce 

 of urine. The quantity of sugar in the urine may be estimated in 

 various other ways. The methods given here are not very exact, 

 but suffice for clinical work. The standard solution of Fehling is 

 generally used. A measured quantity of the solution is taken, and 

 kept boiling in an open dish, while the urine, suitably diluted, is 

 run in from a burette until the blue cupric solution is entirely reduced 

 and decolorized. Ten c.c. of Fehling's solution are reduced by 

 0-05 gramme of dextrose. The unmodified Fehling's method is 

 not to be recommended, owing to the difficulty of recognizing the 

 end-point. The use of an indicator, such as ferrous thiocyanate, 

 is helpful. The end-point is reached when a drop of the solution 

 no longer turns a drop of the indicator red. This shows that there is 



