THE METABOLISM OF THE PURIN BODIES 395 



stant proportion to the amount of purins set free in the tissues, 

 in which case it would be possible, by multiplying the excreted 

 amount by a certain factor, to determine how much purin forma- 

 tion is actually occurring in the body. It is only after the above 

 points have been cleared up that we can expect to understand what 

 the conditions are which influence this tissue formation of purins. 



THE CHEMICAL NATURE OF THE FOOD-STUFFS WHICH 

 INFLUENCE PURIN EXCRETION 



It is not so very many years ago since it was universally believed 

 that the urinary uric acid was derived solely from the proteid given 

 as food f 1 ). As proof of this, it was pointed out that the quantita- 

 tive relationship between urea and uric acid in the urine is a con- 

 stant one. This we would of course expect to find were both these 

 bodies derived from the same source (from proteid.) 



As a matter of fact the quotient ( - -^- rea - ^ ) which expresses this 



Vunc acid/ 



relationship was found to be fairly constant (viz. 45-65) when 

 flesh diet alone was given ; but when the diet was flesh-free (com- 

 posed of milk, pepton, and vegetable proteid) a quotient quite 

 different from that observed on flesh food was obtained. On such 

 a flesh-free diet, it was found that the uric acid excretion became 

 much smaller in amount, and remained at this low level however 

 much the amount of flesh-free proteid might be increased or 

 diminished in the diet, whereas on the other hand, the urea 

 excretion rose and fell with the amount of proteid ingested. For 

 example, Camerer ( 10 ) was able to double the total nitrogen ex 

 cretion without there being any change in the uric acid nitrogen, 

 so that a high quotient was obtained when much proteid was taken 



urea (raised) \ and & }QW Qne when there wag Qnl a 

 uric acid (constant)/ 



(n rf*n ^lOAV^pTprl^ \ 

 __L__ ). It is scarcely necessary 

 uric acid (constant)/ 



to dwell longer on this supposed relationship. The enormous varia- 

 tions which it undergoes under different diets even in the same 

 person, a variation between 23 -2 and 122-4 in some cases collected 

 by von Noorden ( 2 ), shows us, once and for all, that the uric acid 

 excretion can bear no relationship to the extent of proteid metabolism. 



