190 EXCRETION. 



alkaline, 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 grad- 

 uated with a solution of oxalic acid of known strength ; and 

 the degree of acidity is usually expressed by calling it equiv- 

 alent 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, 

 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 variable 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 fore- 

 noon, 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 greatest at night, least in the fore- 

 noon, and between these extremes in the afternoon." 1 The 

 observations upon this subject by Prof. Dalton show that 

 the variations noted by Yogel, in Germany, probably exist 

 in this country, under the conditions of life met with in our 

 large cities. Dr. Dalton found, in his own person, that the 

 maximum of acidity was at night and in the early morning, 

 the minimum being in the forenoon, and the mean in the 

 afternoon and evening. 2 



In estimating the degree of acidity of the urine, it is 

 necessary to test the fluid as soon as possible after it is dis- 

 charged from the bladder ; for its acidity rapidly increases 

 after emission until ammoniacal decomposition sets in by 

 the formation of organic acids, particularly the lactic. 



1 NEUBAUER AND VOGEL, A Guide to the Qualitative and Quantitative Analysis 

 of the Urine, TJie New Sydenham Society, London, 1863, pp. 296, 389. 



2 DALTON, A Treatise on Human Physiology, Philadelphia, 1867, p. 335. 



