URINE AND ITS NORMAL CONSTITUENTS. 373 



deeper amber color, having a peculiar, faintly aromatic odor, a 

 bitter, saline taste, a distinct acid reaction on blue litmus-paper, 

 and a specific gravity heavier than water (average about 1020). 

 When urine is kept in a clean vessel it may remain unchanged 

 for several days, provided the temperature be not too high, and 

 the amount of total solid constituents not too small. 



In urine, shortly after cooling, especially if it be concentrated, 

 a light, cloudy film of mucus is formed, which slowly sinks to 

 the bottom; the acid reaction gradually increases, small yellow- 

 ish-red crystals of acid urates, or uric acid, are deposited. In 

 this condition, the urine may often continue unchanged for sev- 

 eral weeks, provided the temperature be low. If, however, the 

 urine be very dilute, and the temperature above the mean, a 

 decomposition speedily takes place. The urine is then found 

 to be covered with a thin, shining, and frequently iridescent 

 membrane, fragments of which sink gradually to the bottom. 

 The urine then becomes turbid, acquires a pale color, its reac- 

 tion becomes alkaline, and it begins to develop a nauseous 

 ammoniacal odor, due to the products formed during the de- 

 composition of urea and other substances. 



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 com- 

 position of normal human urine may be stated thus : 



"Water, 95.76 percent. 



Urea, 1.50 " 



Uric acid, 0.04 " 



Hippuric acid, 



Kreatin, 



Kreatinfti, j 4Q 



Coloring matter, 



Mucus, 



Unknown organic matters, 



f Sodium, ] 



Phosphates 1 Potassium, 1-30 



Chlorides I of J Calcium, 

 Sulphates Magnesium, i 



[ Iron, 



The above average composition of human urine varies con- 

 siderably, and is influenced by the water and food taken, amount 

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



