UEINE AND ITS NORMAL CONSTITUENTS. 453 



coccus urese) upon urea, which is converted into ammonium carbonate. 

 The change from an acid to an alkaline urine causes the precipitation 

 of earthy phosphates, ammonium-magnesium phosphate, ammonium 

 urate, etc. 



Composition. Urine is chiefly an aqueous solution of urea and 

 inorganic salts, containing, however, always some uric acid, mucus, 

 coloring and other organic matters. The average composition of 

 normal human urine may be stated thus : 



Water . 95.76 per cent. 



Urea 2.50 " 



Uric acid 0.04 



Hippuric acid . 



Kreatin . 



Kreatinin . . . , 0.40 per cent. 



Coloring matter 



Mucus .... 



Unknown organic matters 



f sodium 



Phosphates^ potassium 



Chlorides [ of -{ calcium 



Sulphates - | magnesium 



I iron 



1.30 per cent. 



The above average composition of human urine varies considerably, 

 and is influenced by the water and food taken, amount of work done, 

 time of day, temperature of air, age, sex, etc. 



Urine also contains gaseous constituents, amounting to about 16 

 per cent, by volume ; these gases are chiefly carbon dioxide (88 per 

 cent.), and nitrogen (11 per cent.), with very little oxygen (1 per 

 cent.). 



The quantity of urine passed in a day also varies widely, an adult 

 discharging from 500 to 2300 c.c. in twenty-four hours; a normal 

 average quantity is about 1400 to 1600 c.c. (about 49 to 56 ounces). 

 The quantity of total solids contained in this urine varies from 55 

 to 60 grammes (840 to 920 grains), and over one-half of this quantity 

 is urea. 



NH 2 .CO 



Urea, Carbamide, COH 4 N 2 , or CO il ( or N 2 =H 2 or 



X NH 2 % H 2 



CO(NH 2 ) 2 . Urea is the most important constituent of urine, and is 

 the substance which carries oif by far the largest quantity of all 

 nitrogen taken in the food. Urea has never yet been found as a 

 product of vegetable life, but is found as a normal constituent of the 



