THE METABOLISM OF THE PURIN BODIES 407 



others can take place a preliminary disruption, of CH 3 in the 

 case of methyl-purins, and of NH 2 in the case of amido-purins. 

 has to occur. 



Confining our considerations for the present to man, it will be 

 seen that for the purpose of our experiment it is unnecessary to 

 determine the endogenous excretion. All that is necessary is to 

 keep him on a constant diet, and, when the purin excretion is con- 

 stant, to administer a carefully weighed amount of the purin, or 

 purin containing food-stuff under investigation. As a result of in- 

 vestigations on this plan it has been found that of hypoxanthin 

 given with the food, one -half of that administered reappears in the 

 urine as uric acid. The same result is obtained if flesh, liver, or 

 spleen be given, for, as our table shows, these contain mainly hypo- 

 xanthin. Thus in an experiment of Burian and Schur's 100 grm. 

 of meat (containing therefore 0'06 grm. purin nitrogen) caused an 

 increase of O'Oo grm. in the purin nitrogen content of the urine : 

 100 grm. calf's liver (containing 0'12 grm. purin nitrogen) caused an 

 increase of 0*06 grm., and 100 grm. calf's spleen (containing 0'16 

 grm. purin nitrogen) an increase of 0*08 grm. In all these cases it 

 was uric acid which was increased, and the increase was present 

 for two or three days succeeding the day on which the purin was 

 given. 



Taking the amido-purins next. It has already been pointed 

 out (p. 399) that adenin and guanin, the purin bodies present 

 in nuclein, when added in a pure state to the diet do not 

 cause any change in the uric acid excretion. This does not 

 mean that the purin excretion is unaffected, for it has been 

 found a certain amount of these purins of guanin at least 

 reappears unchanged in the urine. It passes through the 

 organism intact. When presented in a combined state as 

 nuclein, however, quite another result is obtained : there is a 

 distinct increase in the uric acid excretion. Thus 100 grm. of the 

 thymus of the calf (containing 0'40 grm. nuclein-purin nitrogen) 

 gave an increase of O'lO grm. urinary purin nitrogen, the increase 

 being in uric acid. In the case of the methyl -pur ins, 100 grm. 

 coffee containing 0- 20-0 "22 caffein nitrogen yielded 0'075 grm. 

 purin nitrogen. 



To sum up, then about one-half of hypoxanthin-^ reappears 

 in the urine as uric acid, about one-fourth of nuclein purin-N, 



