METABOLISM 47 



for the same individual under the same conditions as 

 regards exercise, etc. It might be supposed that the 

 gouty person is one who produces an unduly large 

 amount of uric acid, but this is apparently not the case. 

 It is probable, also, that a mere fraction of the uric acid 

 produced endogenously ever reaches the urine, but that, 

 as happens with urates taken in with the food, a con- 

 siderable part is destroyed in the liver ; but this is a 

 matter very difficult to investigate at all accurately.. In 

 any case, the amount of uric acid produced endogenously 

 is almost beyond our control, and so our knowledge of 

 its production in this way cannot be turned to account in 

 treatment. 



3. A third way in which uric acid may, perhaps, be 

 produced in the human body is by synthesis from other 

 substances which do not contain the purin-ring at all. 

 We know that it is so produced in birds and reptiles 

 from ammonium lactate, but there is no reason to sup- 

 pose that any large production of it takes place by this 

 method in man. Still, a small percentage may be 

 derived from lactic, tartronic, and /3-oxybutyric acids, 

 and it may be that persons of the so-called ' uric acid 

 diathesis ' have a special aptitude for forming it in this 

 way. The supposed synthesis from glycin and urea, 

 which at one time was so prominent in physiological 

 teaching, is now discredited ; for glycin and urea, when 

 administered to mammals, cause no change in uric acid 

 excretion, and glycin is probably rather a decomposition 

 product than a precursor of uric acid. The same may 

 be true of urea. 



Quite as important in the pathology of gout as the 



