642 METABOLISM 



purine that is excreted. Thus, Mendel and Lyman have found recently 

 that about 60 per cent of injected hypoxanthine, 50 per cent of xan- 

 thine, 19-30 per cent of guanosine, and 30-87 per cent of adenine were 

 eliminated as uric acid. When combined purines i. e., nuclear mate- 

 rial are given, only a small proportion of the purine reappears as uric 

 acid in the urine. There is, therefore, a general parallelism between 

 the purine content of the food and that of the urine, which indicates that 

 purine-rich food should be eliminated from the diet of patients who are 

 suffering from deposition of insoluble urate in the tissues, as in gout. 

 The fate of the purine that disappears in the body is unknown ; some of 

 it may be decomposed in the intestine, but why so much of the remainder, 

 after absorption by the blood, should disappear is a mystery, since no 

 uricase can be discovered in any of the organs or tissues. The destroyed 

 purines can not be shown to influence any of the other well-known 

 nitrogenous metabolites of the urine. 



The following table of experiments by Taylor and Rose 45 may serve 

 to illustrate these points. The subject was placed on a purine-free diet 

 consisting of milk, eggs, starch and sugar, for three days. After this 

 period a part of the total nitrogen (3 grams) was supplied as sweet- 

 breads thymus gland, etc. containing a high percentage (0.482) of 

 purine nitrogen; for another period of four days still more of the nitro- 

 gen (6 grams) was replaced by sweetbread nitrogen; and this was fol- 

 lowed by a final period in which the original diet of milk, etc., without 

 purine substances, was restored. The following table gives the results: 



1ST PERIOD 4TH PERIOD 



PURINE-FREE 2ND PERIOD 3RD PERIOD PURINE-FREE 



DIET DIET 



The increase of uric acid accounted for less than half of the purine 

 nitrogen ingested. This appeared as uric acid, the excretion of purine 

 bases being practically unchanged. 



