URIC ACID. 211 



with alcohol, and afterwards with hot water; as the uric acid in 

 alkaline fluids, and consequently also in the serum, must be com- 

 bined with an alkali, it is in the aqueous extract that we must 

 always search for it ; during the evaporation of the aqueous extract 

 membranes usually form on the surface of the fluid, which must 

 be removed, but whose removal must slightly affect the accuracy of 

 the analysis ; when the aqueous extract has been concentrated to 

 a very small volume, it must be treated with an excess of acetic 

 acid. The uric acid, if its quantity be small, separates very 

 gradually, and unless the acetic acid has been added in great 

 excess, it is usually accompanied with the deposition of a little 

 protein-compound, of whose presence among the crystals of uric 

 acid we can readily convince ourselves by the microscope. It 

 must then be passed through a filter, whose weight has been pre- 

 viously ascertained; and, after careful drying, must be weighed. 

 When the blood is examined qualitatively for uric acid, we must 

 proceed in precisely the same way. 



Physiological Relations. 



Occurrence. Uric acid always occurs in the urine of healthy men, 

 in the ratio of about one to a thousand parts of urine, as appears 

 from the mean of numerous experiments instituted under different 

 conditions. While living on a mixed diet, the average amount of 

 uric acid which I excreted in 24 hours was 1*183 grammes; accor- 

 ding to BecquerePs observations made on 8 different persons, the 

 quantity excreted by healthy men in 24 hours, did not amount to 

 more than from 0*495 to 0*557 of a gramme. 



I regret that I must here remark, that the laborious analyses 

 which I made of my own urine cannot altogether serve as standards 

 of comparison for other urines, as when I instituted those obser- 

 vations I was affected with softening of the tissue of the left lung. 



Uric acid also occurs in the urine of carnivorous mammalia, 

 although generally in far less quantity than in that of man. In 

 the urine of omnivora, as, for instance, in that of the pig, neither 

 Boussingault* nor Von Bibraf succeeded in detecting uric acid. 

 In the urine of graminivorous mammalia this acid has never been 

 found, except by Bracket [and by Fownes G. E. D.], although 

 according to Wohler it occurs in considerable quantity in the urine 



* Ann. de Chim. et de Phys. 3 Se'r. T. 15, pp. 97-114. 

 t Ann. d. Ch. u. Pharra. Bd. 53, S. 98-112. 

 J Journ. f. pr. Ch. Bd. 25, S. 254. 

 Phil. Mag. vol. 21, p. 383. 



P 2 



