COMPOSITION AND CHARACTERS OF URINE 1255 



zine are added to 5 c.c. of urine. The mixture is evaporated down to 3 c.c., 

 rapidly cooled, and again warmed in a water bath. It is then allowed to cool 

 slowly. Crystals of the corresponding osazone separate out in the hot liquid in 

 the case of glucosazone, on cooling in the case of lactosazone (Figs. 519, 520). 



(3) The most convenient way of distinguishing between lactose and glucose 

 is by adding a little yeast to the urine in an inverted test-tube. If glucose be the 

 sugar present, it is fermented by the yeast with the production of carbon dioxide, 

 which collects at the top of the test-tube. 



In rare circumstances fructose or leevulose, or pentose may be 

 found in the urine. The former would be detected by the fact that 

 it rotates polarised light to the left, instead of to the right, as is the 

 case with glucose. 



GLYCURONIC ACID. Small traces of this are present in normal 

 urine. It occurs as a conjugated acid after the administration of 

 various substances, e.g. camphor and chloral. If phenol, indol, or 

 scatol be given to an animal which is receiving very little protein in 

 its diet, these substances will leave the body conjugated, not with 

 sulphuric acid, but with glycuronic acid. Grlycuronic acid may be 

 regarded as the first product of oxidation of glucose, having the 

 formula : 



COOH 



(CHOH) 4 

 CHO 



It reduces Fehling's solution and rotates the plane of polarised light 

 to the left. 



OXY-FATTY ACIDS AND ACETONE. These substances occur 

 often associated with glucose in diabetes, especially towards the latter 

 stages. They represent the penultimate stages in the oxidation oHhe 

 fats. Their relation to one another is seen from their formulse : 



CH 3 CH 3 CH 3 



CHOH CO CO 



CH 2 CH 2 CH 3 



COOH COOH 



Oxybutyric Aceto-acetic Acetone 



acid acid 



They may also occur in any condition of carbohydrate starvation, 

 relative or absolute. Thus they are found in the urine during 

 absolute starvation as well as in individuals on a pure fat and 



