COMPOSITION OF THE UKINE. 219 



by the kidneys. The urea and uric acid are derived from muscular de- 

 cay ; perhaps, of -the two, the uric acid first arises, and is subsequently 

 converted into urea ; this is not, however, its exclusive source, since the 

 quantity of urea increases by the use of highly nitrogenized food. The 

 mucus and epithelial debris are derived from the mucous membrane lin- 

 ing the interior of the urinary apparatus. Of the salts, there are two of 

 unusual interest, the sulphates and phosphates, each having, like the 

 urea, a double origin, the food and tissue decay. Leaving out of consid- 

 eration that part which has been supplied by the food, we recognize in 

 the sulphates the final disposal of that sulphur which was once secreted 

 by the liver, and subsequently reabsorbed. In the phosphates we recog- 

 nize the oxidation of the free phosphorus of the nervous Constitution of 

 vesicles during their period of activity. That portion of the urine - 

 solid constituents of the urine which is due to decay or retrograde met- 

 amorphosis is shown when an animal is exclusively fed on sugar. 



Composition of Urine. (From Berzelius.} 



Water 933.00 



Urea 30.10 



Uric acid 1.00 



Lactic acid, lactate of ammonia, and extractive 1 7. 14 



Mucus 00.32 



Sulphate of potash 3.71 



Sulphate of soda , 3.16 



Phosphate of soda 2.94 



Bi-phosphate of ammonia 1.65 



Chloride of sodium 4,45 



Muriate of ammonia 1.50 



Phosphates of lime and magnesia 1.00 



Silica 0.03 



1000.00 



The composition of urine is not only disturbed by variations in the 

 amount of its normal ingredients, but likewise, in morbid states, by the 

 appearance of unusual ones. Among these may be more particularly 

 mentioned sugar, albumen, blood, bile, pus, fat. The presence of such 

 abnormal ingredients is determined by chemical tests or microscopic ob- 

 servations. 



Since the urinary apparatus is the sewer of the system, tables, like the 

 preceding, which purport to set forth the composition of its y ariabil ity O f 

 excretion, can only be received as general illustrations. In its constitu- 

 the urine must occur whatever materials have been gener- 

 ated in the complicated disintegration of the economy, and whatever use- 

 less substances have found their way in through the absorbents by rea- 

 son of their solubility in water. 



Eespecting the substances thus occurring, either normally or unusu- 

 ally, in the urine, the following are observations of interest : 



The quantity of urea excreted depends more upon the nature of the 



