PKOPERTIES AND COMPOSITION OF THE URINE. 411 



Quantity, Specific Gravity, and Reaction of the Urine. In estimating the total quan- 

 tity of urine discharged in the twenty-four hours, it is important to take into considera- 

 tion the specific gravity, as an indication of the amount of solid matter excreted by the 

 kidneys. We have already alluded to some of the variations in quantity constantly oc- 

 curring in health, as depending upon the proportion of water ; but the amount of solid 

 matters excreted is usually more nearly uniform. It must also be taken into account that 

 differences in climate, habits of life, etc., in different countries, have an important influ- 

 ence upon the daily quantity of urine. Dr. Parkes has collected the results of twenty-six 

 series of observations made in America, England, France, and Germany, and he finds the 

 average daily quantity of urine in healthy male adults, between twenty and forty years 

 of age, to be fifty-two and a half fluidounces, the average quantity per hour being two 

 and one-tenth fluidounces. The extremes were thirty-five and eighty-one ounces. 



In attempting to decide the question whether a certain quantity of urine passed be 

 abnormal or within the limits of health, it is important to recognize, if possible, certain 

 limits of physiological variation. Becquerel states that the variations in the proportion 

 of water in the urine likely to occur in health are between twenty-seven and fifty fluid- 

 ounces ; but his average of the total quantity in the twenty-four hours is only forty-four 

 ounces, which is rather lower than the one we are disposed to adopt. The circumstances 

 that lead to a diminution in the proportion of water are usually more efficient in their 

 operation than those which tend to an increase ; and the range below the healthy standard 

 is rather wider than it is above. All these estimates, however, are merely approxima- 

 tive. Assuming that the usual quantity in the male is about fifty ounces, it may be stated, 

 in general terms, that the range of normal variation is between thirty and sixty ; and 

 that, when the quantity varies much from these figures, it is probably due to some patho- 

 logical condition. 



According to the researches of Becquerel, the quantity of water discharged by the 

 kidneys in the twenty-four hours is a little greater in the female than in the male ; but 

 in the female the specific gravity is lower, and the amount of solid constituents is rela- 

 tively and absolutely less. 



The specific gravity of the urine should always be estimated in connection with the 

 absolute quantity in the twenty-four hours. Those who assume that the daily quantity 

 is about fifty ounces give the ordinary specific gravity of the mixed urine of the twenty- 

 four hours, at 60 Fahr., as about 1020. The specific gravity is liable to the same vari- 

 ations as the proportion of water, and the density is increased precisely as the amount of 

 water is diminished. The ordinary range of variation in specific gravity is between 1015 

 and 1025 ; but, without positively indicating any pathological condition, it may be as low 

 as 1005 or as high as 1030. 



The reaction of the urine is acid in the carnivora and alkaline in the herbivora. In 

 the human subject, it is usually acid at the moment of its discharge from the bladder ; 

 although at certain periods of the day it may be neutral or feebly alkaline, the reaction 

 depending upon the character of the food. The acidity may be measured by carefully 

 neutralizing the urine with an alkali, in a solution that has previously been graduated 

 with a solution of oxalic acid of known strength ; and the degree of acidity is usually 

 expressed by calling it equivalent to so many grains of crystallized oxalic acid. 



As the result of numerous observations made by Yogel and under his direction, the total 

 quantity of acid in the urine of the twenty-four hours in a healthy adult male is equal to 

 from two to four grammes, or, omitting fractions, to from thirty to sixty grains of oxalic 

 acid. The hourly quantity in these observations was equal, in round numbers, to from 

 one and a half to three grains of acid. The proportion of acid was found to be very vari- 

 able in the same person at different periods of the day. In one individual, upon whom 

 the greatest number of observations was made, the average hourly quantity of acid at 

 night was 2'9 grains; in the forenoon, 2 grains; and in the afternoon, 2'3 grains. "In 

 a series of experiments made upon four different persons, the quantity was found to be 



