350 EXCRETION. 



gravity, 1024. Both its total quantity, however, and its mean 

 specific gravity are liable to vary somewhat from day to day, owing 

 to the different proportions of water and solid ingredients entering 

 into its constitution. Ordinarily the water of the urine is more 

 than sufficient to hold all the solid matters in solution; and its pro- 

 portion may therefore be diminished by accidental causes without 

 the urine becoming turbid by the formation of a deposit. Under 

 such circumstances, it merely becomes deeper in color, and of a 

 higher specific gravity. Thus, if a smaller quantity of water than 

 usual be taken into the system with the drink, or if the fluid ex- 

 halations from the lungs and skin, or the intestinal discharges, be 

 increased, a smaller quantity of water will necessarily pass off by 

 the kidneys ; and the urine will be diminished in quantity, while its 

 specific gravity is increased. We have observed the urine to be 

 reduced in this way to eighteen or twenty ounces per day, its specific 

 gravity rising at the same time to 1030. On the other hand, if the 

 fluid ingesta be unusually abundant, or if the perspiration be dimi- 

 nished, the surplus quantity of water will pass off by the kidneys; so 

 that the amount of urine in twenty-four hours may be increased to 

 forty-five or forty-six ounces, and its specific gravity reduced at 

 the same time to 1020 or even 1017. Under these conditions the 

 total amount of solid matter discharged daily remains about the 

 same. The changes above mentioned depend simply upon the 

 fluctuating quantity of water, which may pass off by the kidneys 

 in larger or smaller quantity, according to accidental circumstances. 

 In these purely normal or physiological variations, therefore, the 

 entire quantity of the urine and its mean specific gravity vary 

 always in an inverse direction with regard to each other ; the former 

 increasing while the latter diminishes, and vice versa. If, however, it 

 should be found that both the quantity and specific gravity of the 

 urine were increased or diminished at the same time, or if either 

 one were increased or diminished while the other remained station- 

 ary, such an alteration would show an actual change in the total 

 amount of solid ingredients, and would indicate an unnatural and 

 pathological condition. This actually takes place in certain forms 

 of disease. 



The amount of variation in the quantity of water, even, may be 

 so great as to constitute by itself a pathological condition. Thus, 

 in hysterical attacks there is sometimes a very abundant flow of 

 limpid, nearly colorless urine, with a specific gravity not over 1005 

 or 1006. On the other hand, in the onset of febrile attacks, the 



