KIDNEYS. 



153 



The average quantity of the principal constituents excreted in twenty- 

 four hours is as follows: 



Water 52.0 fluidounces. 



Urea 512.4 grains. 



Uric acid 8.5 grains. 



Phosphoric acid 45 .o grains. 



Sulphuric acid 31.11 grains. 



Inorganic salts 323 . 25 grains. 



Lime and magnesia 6.5 grains. 



To determine the amount of solid matters in any given amount of urine 

 multiply the last two figures of the specific gravity by the coefficient of 

 Haeser, 2.33 e. g., in 1,000 grains of urine having a specific gravity of 1022, 

 there are contained 22X2.33 =51.26 grains of solid matter. 



Organic Constituents of Urine. Urea is one of the most important 

 of the organic constituents of the urine, and is present to the extent of from 

 2.5 to 3.2 per cent. Urea is a colorless, neutral substance, crystallizing in 

 four-sided prisms terminated by oblique surfaces. When crystallization is 

 caused to take place rapidly, the crystals take the form of long, silky needles. 

 Urea is soluble in water and alcohol; when subjected to prolonged boiling, 

 it is decomposed, giving rise to carbonate of ammonia. In the alkaline 

 fermentation of urine, urea takes up two molecules of water with the pro- 

 duction of carbonate of ammonia. 



The average amount of urea excreted daily has been estimated at about 

 500 grains. As urea is one of the principal products of the breaking up of the 

 protein compounds within the body, it is quite evident that the quantity 

 produced and eliminated in twenty-four hours will be increased by any 

 increase in the amount of protein food consumed, or by a rapid destruction 

 of protein tissues, as is observed in various pathologic states, inanition, 

 febrile conditions, fevers, etc. A farinaceous or vegetable diet will diminish 

 the urea production nearly one half. 



Muscular exercise when the nutrition of the body is in a state of equilibrium 

 does not seem to increase the quantity of urea. 



Seat of Urea Formation. As to the seat of urea formation, little is posi- 

 tively known. It is quite certain that it preexists in the blood and is merely 

 excreted by the kidneys. It is not produced in muscles, as even after pro- 

 longed exercise hardly a trace of urea is to be found in them. Experimental 

 and pathologic facts point to the liver as the probable organ engaged in urea 

 formation. Acute yellow atrophy of the liver, suppurative diseases of the 

 liver, diminish almost entirely the production of urea. It is at present 



