THE URINE 



455 



gives one broad absorption band in the green between b and F. The 

 urine containing it is generally dichroic, appearing red by transmitted, 

 and green by reflected, light. If urobilinogen be in excess, it is found 

 that an acid solution of dimethylparaminobenzaldehyde (2 grammes 

 in 100 c.c. 5 per cent. HC1), when added to the urine, turns red in 

 the cold. With normal urine, such a red colour is only developed on 

 heating. 



Uroerythrin confers a dark pink colour on concentrated urine. 

 Spectroscopically, it yields two bands, one at E, the other at F. They 

 are not well defined. Urorosein is an indol derivative. 



Composition, Normal urine contains about 96 per cent, of water 

 and 4 per cent, of solids. The chief organic bodies are Urea, uric 

 -acid, purin bodies, creatinin, ethereal sulphates, neutral sulphur com- 

 pounds, oxalic acid, hippuric acid, enzymes, pigments. 



The inorganic solids are Chloride solids of sodium and potassium, 

 sulphates, phosphates, carbonates. 



The Nitrogenous Constituents. The chief of these are urea, am- 

 monia, uric acid, creatinin, hippuric acid. There are various other 

 substances in small quantities, including the purin bases. These 

 vary in percentage according to the intake of nitrogenous food in the 

 diet. With the exception of creatinin, the amount of these bodies 

 excreted falls as the amount of the nitrogen in the diet is decreased. 



According to the diet the percentage of urea varies in relation to 

 the percentage of other bodies, particularly to the percentage of 

 ammonia. 



This is shown by the following analyses of such urines : 



Total nitrogen excreted 

 Urea N 

 Ammonia N 

 Uric acid N . . 

 Creatinin N . . 

 Undetermined N 



Nitrogen-Rich Diet. Nitrogen-Poor Diet. 



Grms. 



16-8 



14-7 (87-5 per cent.) 



0-49 (3-0 ) 



0-18 (1-1 ) 



0-58(3-6 ) 



0-85 (4-9 ) 



Grms- 



3-60 



2-20(61-7 percent.) 



0-12 (11-3 ) 



0-09 ( 2-5 ) 



0-60 (17-2 ) 



0-27 ( 7-3 ) 



Almost the whole of the nitrogen taken in the food is excreted in 

 the urine. .Protein contains about 15 per cent, of nitrogen, and if 100 

 grammes are consumed, about 1 gramme nitrogen will be passed in the 

 faeces, a trace in the sweat, and the rest in the urine. By estimating 

 the total nitrogen of the twenty -four hours' urine the intake of protein 

 can be calculated. 



The Total Nitrogen of the Urine is estimated by means of Kjeldahl's 

 method, or one of its modifications. The process is carried out in 

 three stages: (1) The oxidation of the nitrogen present in the urine to 

 ammonia; (2) the distillation and collection of this ammonia in a 

 standard acid solution; (3) the ascertaining by titration of the amount 

 of this ammonia. 



