780 PHYSIOLOGY 



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 Kruger and 

 Salomon succeeded in isolating the following purine bases : 



Xanthine 



Hypox.-.nthine 



Adenine 



10-1 grm. 

 8-5 

 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 composition 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 

 quant ty 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 diet the amount of uric acid increases 

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

 the Tables by Folin (already quoted) of the composition of the urine 

 on a low and a high protein diet respectively. Although in each case 

 care was taken to exclude purine-containing bodies from the food, 

 the output of uric acid on the high nitrogenous diet was double as 

 much as on the low diet. All we can say is that uric aeid is constantly 



