274 PRACTICAL PHYSIOLOGY 



nursing mothers, and the latter may appear in the urine when 

 pentoses 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 VII. Fehling's Test. Boil 5 c.c. of Fehling's 

 solution in order to ascertain that the Rochelle salt which it con- 

 tains 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. 



Fehling's test is quite satisfactory, when sugar is present in 

 considerable quantity. When the amount of reduction is small, 

 however, it may be due to the presence of other substances than 

 sugar. In such cases the following tests should be applied, as they 

 are positive for sugars only. 



EXPERIMENT VIII. Boettger's Test. To 

 10 c.c. urine add 1 c.c. Nylander's reagent. 1 

 Heat for five minutes on the water bath. 

 If sugar is present to the extent of at least 

 0-08 per cent., a black precipitate of bis- 

 muth forms. 



Though not so delicate, the following 

 tests are valuable, in that they indicate the 

 nature of the sugar : 



EXPERIMENT IX. 1. The Fermentation 

 Test. Place some diabetic urine in a small 

 beaker, and boil it on a sand bath for ten 

 minutes, to expel any air it may contain. 

 Cool the urine and test its reaction ; if 

 alkaline, render faintly acid with a weak 

 solution of tartaric acid. (This precaution 

 FIG. 194.-TJreometer. ig necessary in order to preven t putrefac- 

 tion, which would lead to the evolution of ammonia.) Add 

 a small piece (about the size of a split pea) of yeast, and stir 

 it in the urine until a milky solution is obtained. Now transfer 

 the fluid to a Doremus ureometer so that the upright limb is 

 completely filled with fluid. Place this in an incubator, or in a 

 warm place, as on the mantelpiece, overnight when it will be 

 found that gas carbon dioxide has collected in the upper por- 

 tion of the vertical limb. 



Two control tubes one with a weak solution of dextrose and 

 yeast, the other with normal urine and yeast should be arranged 

 so as to prevent any fallacy due to inactive or impure yeast. If 

 the amount of sugar present be very small, the fermentation test 

 may give a negative result. 



1 Nylander's solution : dissolve 4 gms. Rochelle salt in 100 gms. of a caustic 

 soda solution of 1-12 sp. gr. ; add 2 gms. Bismuth subnitrate and heat on water 

 bath until it is dissolved. 



