COMPOSITION AND CHARACTERS OF URINE 1123 



amount of sugar in the blood is increased, and sugar appears in large quantities in the 

 urine. The sugar is practically always glucose or dextrose. Lactose may occur in the 

 urine of nursing women even in conditions of health. Since both these sugars will 

 reduce Fehling's solution it becomes important to be able to distinguish between them. 

 The following tests are used for the detection of abnormal amounts of sugar in the 

 urine : 



(1) FEHLING'S TEST. The urine is boiled with Fehling's solution (an alkaline 

 solution of copper sulphate to which Rochelle salt has been added to keep the cupric 

 hydrate in solution). Under the action of glucose or lactose the cupric hydrate is 

 reduced to an insoluble cuprous hydrate, which forms a yellow or red precipitate. 



(2) The phenylhydrazine test may be carried out as follows : 2 c.c. of 50 per cent, 

 acetic acid, saturated with sodium acetate, and two drops of phenylhydrazine 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 correspond- 

 ing osazone separate out in the hot liquid in the case of glucosazone, on cooling in the 

 case of lactosazone (Figs. 521, 522). 



(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 Isevulose, 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 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. Glycuronic 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 pen- 

 ultimate stages in the oxidation of the fats. Their relation to one another is seen from 

 their formulae : 



CH 3 CH 3 CH 3 



CHOH CO CO 



I I I 



CH 2 CH 2 CH 3 



COOH COOH 



Oxy butyric acid Aceto- acetic acid Acetone 



They may also occur in any condition of carbohydrate starvation, relative or abso- 

 lute. Thus they are found in the urine during absolute starvation as well as in 

 individuals on a pure fat and protein diet. The two acids are generally found associated 

 in the urine. 



The presence of aceto-acetic acid may be detected as follows : 

 (1) To some urine add ferric chloride as long as a precipitate of ferric phosphate con- 

 tinues to form. Filter this off and to the filtrate add a few more drops of ferric 

 chloride. If the acid be present a claret colour is produced. 



