388 THE URINE. 



poses is that of Dr. Roberts, 1 which depends upon the loss of specific 

 gravity occasioned by the decomposition of the glucose in fermentation. 

 A portion of the urine is taken and its specific gravity ascertained at 

 the temperature of 25 (77 F.). A little yeast is then added and the 

 mixture kept at the same temperature until fermentation has ceased ; 

 when the specific gravity is again taken. The diminution in density 

 caused by the conversion of the glucose into alcohol and carbonic acid 

 is such that the loss of one degree in specific gravity indicates the dis- 

 appearance of 2.191 milligrammes of glucose for every cubic centimetre 

 of urine. 



The glucose can be obtained directly from diabetic urine, according to 

 the method of Hoppe-Seyler, by evaporating the urine over the water- 

 bath to the consistency of a syrup, and allowing it to remain at rest for 

 some days or weeks until completely crystallized. The crystalline mass 

 is triturated and washed with a small quantity of cold alcohol, to re- 

 move tire- urea. The residue is then extracted with boiling alcohol, and 

 the alcoholic solution filtered while still hot, after which the glucose is 

 deposited in a crystalline form. 



The glucose of diabetic urine is not formed in the kidneys, but pre- 

 exists in the blood, from which it is eliminated in the renal circulation. 

 If a solution of sugar be introduced in sufficient quantity directly into 

 the bloodvessels of the rabbit, or injected into the subcutaneous con- 

 nective tissue so as to be absorbed thence by the blood, it is soon 

 discharged by the kidneys. It has been shown by Bernard, 2 that the 

 time within which sugar appears in the urine under these circum- 

 stances varies with the quantity injected and the rapidity of its absorp- 

 tion. If a solution of one gramme of glucose in 25 cubic centimetres of 

 water be injected under the skin of a rabbit weighing a little over one 

 kilogramme, it is entirely destroyed in the circulation, and does not pass 

 out with the urine. A dose of 1.5 gramme, however, injected in the 

 same way, appears in the urine at the end of two hours, 2 grammes in 

 an hour and a half, 2.5 grammes in an hour, and 12.5 grammes in fifteen 

 minutes. Whenever, accordingly, glucose accumulates in the circula- 

 tion beyond a certain quantity in proportion to the whole mass of the 

 blood, it is eliminated as a foreign substance, and appears as an in- 

 gredient of the urine. 



Biliary Matters. In some cases of jaundice, the coloring matter of 

 the bile passes into the urine in sufficient abundance to give to the fluid 

 a deep yellow or yellowish-brown tinge, so that it may even stain linen 

 or cotton fabrics, with which it comes in contact, of a similar color. 

 The saline biliary substances, namely, sodium glycocholate and tauro- 

 cholate, according to Lehmann, have also been detected in the urine. 

 In these instances, the biliary matters are reabsorbed from the hepatic 

 ducts and conveyed by the blood to the kidneys. 



1 Urinary and Renal Diseases. Philadelphia edition, 1872, p. 198. 



2 Leqons de Physiologic Expe>imentale. Glycog6nie. Paris, 1855, p. 216. 



