150 THE PHYSIOLOGY OF URIC ACID 



from two main sources, the xanthin of the muscles 

 and the nucleoprotein of all cell nuclei. Much of 

 the purin bodies split off from these is oxidized into 

 uric acid by the above-mentioned ferments, but only 

 that which chances to be carried to the kidney before 

 it reaches the liver appears in the urine as uric acid 

 or urates. That which finds its way to the liver 

 appears in the urine principally as urea. 



The excretion of purin bodies on a purin-free diet 

 is of course entirely endogenous, and the daily output 

 is a constant for the individual, depending roughly 

 on the weight of his muscles. It is, however, 

 increased greatly by muscular exercise. Whilst the 

 hard work is proceeding the uric acid output falls 

 a little, while the xanthin output rises correspond- 

 ingly ; the muscles take up so much oxygen that 

 there is none to spare to oxidize xanthin. After 

 the work is over, the uric acid rises. Unaccustomed 

 work is much more effectual than routine work. 

 There is also a considerable rise in any conditions 

 where cell nuclei are rapidly broken down. As is 

 well known, there is an increase of both uric acid and 

 purin bodies in the urine in fever, and especially 

 in leukaemia. In gout, less uric acid than usual is 

 passed. 



It appears that purin bodies are not utilized by 

 the body in the synthesis of nucleoprotein in the 

 protoplasm. It seems to be formed from proteins. 



Indeed, it is very doubtful if purin bodies serve 

 any useful purpose. It is certain that they are power- 

 ful stimulants in some cases ; caffeine is of course 

 one of the most powerful and satisfactory stimulants 



