THE URINE. 



333 



FIG. 81. 



diabetes mellitus. In this disease the urine is generally increased in 

 quantity and of unusually high specific gravity, namely, from 1035 to 

 1050. It is of a light straw color, and so transparent that it has the 

 appearance of being dilute, though 

 really denser than usual, owing to the 

 glucose which it holds in solution. The 

 glucose may be detected by Tronimer's 

 or Fehling's test, or by fermentation. 

 For the latter purpose a little yeast is 

 mixed with 15 or 20 times its volume 

 of water, and the mixture allowed to 

 remain at rest in an upright cylindrical 

 vessel until the yeast globules have 

 subsided to the bottom. The super- 

 natant fluid, containing the soluble 

 impurities of the yeast, is poured off, 

 and a small quantity of the moist 

 deposit added to the urine. The mix- 

 ture is then placed in a ferment-appa- 

 ratus and kept at a temperature of 

 about 25 C., for forty-eight hours, 

 when the gaseous products of fermen- 

 tation will have been completely dis- 

 engaged. The most convenient form 

 of apparatus is a graduated test-tube, 

 supported by 'a foot and provided with 

 an India-rubber stopper, through which 

 passes a narrow glass tube, open at 

 both ends. Its inner extremity, reach- 

 ing to the bottom of the test-tube, is 

 bent upward, to prevent the escape of gas, while its outer portion is 

 bent downward, to allow the liquid expelled through it to drop freely 

 from its orifice. The test-tube being filled with the fermenting urine, 

 the disengaged gas rises to its upper part and collects there, while the 

 urine is forced out through the bent tube. Every cubic centimetre of 

 carbonic acid produced corresponds to 0.26 milligrammes of sugar 

 decomposed. A similar apparatus, containing the same quantity of 

 healthy urine and yeast, should be kept at the same temperature for 

 an equal time, as a comparative test ; since a small quantity of gas 

 might be produced from the yeast, owing to its imperfect purification. 

 But in this case the disengagement of gas soon ceases ; while in the 

 fermenting solution it continues until all the sugar has been decom- 

 posed. This method does not give the precise quantity of glucose 

 contained in any single specimen, since some of the urine escapes 

 before fermentation is complete ; but it is at the same time the surest 

 indication of the presence of sugar, and a ready means of ascertaining 

 its comparative amount in different specimens. 



rine urine in fermentation. a. Upper 

 part of the test-tube containing carbonic 

 acid. b. Lower part of the test-tube con- 

 taining the fermenting liquid, c. Bent 

 glass tube, to allow the escape of liquid. 

 d. Liquid which has been forced out from 

 the test-tube by the accumulation of gas. 



