396 THE METABOLISM OF THE PURIN BODIES 



One fact, however, stands out clearly in the results of the 

 numerous researches which were recorded in connection with the 

 influence of diet on the uric acid excretion, and this is that 

 flesh contains something which influences the excretion. What 

 could this be ? The chemical relationship between the xanthin 

 bases, and uric acid, already described in the chemical introduc- 

 tion, suggested these bases as possible precursors of uric acid, 

 and experiments were accordingly undertaken in which purin 

 bodies were given in the food to animals, and their influence 

 on the uric acid excretion observed. The first experiments along 

 these lines yielded, however, entirely negative results ; the 

 cause of which was later shown to be that unsuitable animals 

 (dog, rabbit) had been chosen for the experiments, i.e. animals 

 in which an extensive break-down of the purin ring ensues. 

 More recently by experimenting on man, it has been definitely 

 established that hypoxanthin at least causes quite a distinct 

 increase in the excretion of uric acid, and that meat extract, 

 which contains a considerable amount of this oxy-purin and also 

 of xanthin, had the same effect ( 3 ). There can be no doubt then 

 that xanthin and hypoxanthin can cause a marked increase in 

 the excretion of uric acid in man. 



There are certain animal food-stufTs (thymus gland, &c.), 

 however, which do not contain, in simple extracts of them, any 

 large amount of these oxy-purins, and which nevertheless cause, 

 even in dogs, a distinct increase in the purin excretion. A clue 

 to the influence of these foods on the uric acid excretion was 

 furnished in 1882 by Kossel ( 4 ). By this worker it was shown 

 that certain xanthin bases are among the chief decomposition 

 products of nucleins, which are very abundant in these food- 

 stufTs, and the idea was suggested by him that uric acid might 

 be derived from those, hypoxanthin being formed as an inter- 

 mediate product. It was, however, several years later before it 

 could be conclusively shown that this supposition of Kossel was 

 correct. This Horbaczewski ( 5 ) succeeded in doing. He allowed 

 a mixture of one part of spleen pulp and eight parts of water 

 to stand at a temperature of about 50 C. for eight hours. After 

 this time, moderate putrefaction had set in. By filtering he 

 obtained a fluid from which after precipitating various substances 

 with lead acetate, and separating the proteid by boiling he was 

 able to isolate a large amount of xanthin and hypoxanthin, On 



