880 PHYSIOLOGY 



excreted at different times. Under ordinary circumstances a man 

 excretes about half a gramme of uric acid per day. In addition the 

 urine contains a certain small amount of purine bases, the ratio of 

 these bases to the uric acid being generally about 1 : 6. From 10,000 

 litres of human urine Kriiger and Salomon succeeded in isolating the 

 following purine bases : 



Xanthine . . .10-1 grm. 

 Hypoxanthine . . . 8-5 

 Adenine . . .3-5 ,, 



The same urine would probably have contained about 500 grm. of 

 uric acid. As we should expect, the amount of uric acid in the urine 

 varies with the diet. The following Tables from Bunge give the com- 

 position of the urine secreted (1) on a mixed diet, (2) on a diet mainly 

 composed of meat, (3) on a diet mainly composed of bread : 



An attempt has been made to arrive at the amount of uric acid 

 produced endogenously, i.e. from the breakdown of the tissues, from 

 a study of the amount of uric acid in the urine under varying conditions 

 of food. During starvation, when the man is living on his own tissues, 

 one might expect the uric acid to be increased in consequence of 

 disintegration of the tissues. It has been suggested that the amount 

 of the endogenous uric acid in the urine would be obtained by an 

 analysis of the urine from patients taking a diet free from purine 

 bases, but containing sufficient nitrogen to maintain nitrogenous 

 equilibrium. It is impossible, however, to arrive at any constant 

 figure for the endogenous uric acid. Even in the entire absence of 

 purine derivatives from the body the amount of uric acid increases 

 with the total nitrogenous metabolism. This fact is well shown in the 

 Tables byFolin (already quoted) of the composition of the urine on a 



