334 FUNCTIONS OF NUTRITION. 



The quantity of glucose in a given specimen may be determined 

 with sufficient accuracy for clinical purposes by the method of Rob- 

 erts,* which depends upon the loss of specific gravity from the de- 

 composition of glucose by fermentation. A portion of the urine is 

 taken and its specific gravity ascertained at the temperature of 25 C. 

 A little yeast is then added and the mixture kept at the same temper- 

 ature until fermentation has ceased ; when the specific gravity is again 

 taken. The diminution in density caused by the decomposition of 

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

 the disappearance of 2.1 9f milligrammes of glucose for every cubic 

 centimetre of urine. 



Glucose can be obtained 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 until com- 

 pletely crystallized. The crystalline mass is triturated and washed 

 with a small quantity of cold alcohol, to remove the urea. The resi- 

 due is then extracted with boiling alcohol, and the alcoholic solution 

 filtered while hot, after which the glucose is deposited in a crystalline 

 form. 



The glucose of diabetic urine is derived from the blood, from which 

 it is eliminated in the renal circulation. It has been shown by Ber- 

 nard^ that when glucose is injected into the blood-vessels or the sub- 

 cutaneous connective tissue, the time within which it appears in the 

 urine 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 destroyed in the circulation, and does not pass 

 out with the urine. A dose of 1.5 gramme, 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. When glucose accordingly accumulates in the circulation 

 beyond a certain proportion to the volume of the blood, it is elimi- 

 nated as a foreign substance, and appears in the urine. 



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

 the bile passes into the urine in sufficient abundance to give it a deep 

 yellow or yellowish-brown tinge. 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. 



Potassium ferrocyanide, when introduced into the circulation, ap- 

 pears with great readiness in the urine. According to Bernard, it may 

 begin to be eliminated within twenty minutes after its injection into 

 the duct of the submaxillary gland. 



Iodine, in all its combinations, passes out by the same channel.. 



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



f Lefons de Physiologic Experimentale. Glycoge"nie. Paris, 1855, p. 216. 



