390 PHYSIOLOGY CHAP. 



elimination of the purines. On administering water he saw that 

 the nitrogen of the uric acid and that of the purine bases was 

 almost doubled ; on administering milk the nitrogen of the purine 

 bases was more than doubled, while the uric acid, on the contrary, 

 diminished the normal ratio between the two being inverted. 

 These results were confirmed by Zagari and Pace. 



These and other experiments, which space compels us to omit, 

 are sufficient to show that the production of uric acid is largely 

 influenced by the nature of the diet ; it increases on ingestion of 

 substances rich in nuclein and purines, and diminishes on ingestion 

 of foods in which, as in milk, they are scanty. As urea represents 

 the final result of the conversion of alimentary protein, so uric acid 

 and the purines represent the katabolic products of the alimentary 

 nucleins. 



Of the later work on this subject special mention must be made 

 of that of E. Burian and H. Schur (1900-1). They endeavoured, 

 by a number of researches, to ascertain the fate of the purine 

 bodies in human metabolism, and arrived at the following results : 



Every healthy adult eliminates a definite and constant quantity 

 of purine bodies by the urine. These result from metabolic pro- 

 cesses, which are to a certain extent independent of the diet. The 

 amount of this endogenous purine, which, as we have said, is 

 approximately specific and constant for each individual, can be 

 directly determined on dieting the subject for a sufficiently long 

 period exclusively on foods that contain no nucleo-protein (milk, 

 cheese, eggs, potatoes, rice, salad, white bread, etc.). In ordinary 

 human diet these endogenous purines are reinforced in a variable 

 degree by other purines which are derived from the preformed 

 purines of the food, and must therefore be distinguished by the 

 name of exogenous or alimentary purines. The usual fluctuations 

 in the elimination of the purines depend mainly upon their varying 

 content in the food. The amount of exogenous puriue eliminated 

 with the urine does not, however, correspond exactly with the 

 amount of alimentary purine ; a greater or lesser part of the latter 

 is broken up in the body by decomposition of the purine-ring. 



The amount of nitrogen eliminated in the form of endogenous 

 purine in the course of the day fluctuates between O'l and 0'2 

 grins. The principal formation of endogenous purine takes place, 

 according to Burian's latest work, in the muscles. 



In all mammals, both the exogenous and the endogenous 

 acid are an intermediate product of metabolism, i.e. one whici 

 undergoes or may undergo further cleavage in the body. Thai 

 this holds also for endogenous uric acid is shown by the fact that 

 in dogs, after removal of the kidneys and the liver, which is 

 the most important organ in the destruction of uric acid, endo- 

 genous uric acid is found in the blood, which is not the case after 

 removing the kidneys only. Since, however, the mammalian body 



