XUCLEIC ACIDS 153 



But these considerations are somewhat speculative. There is but 

 one way to prove the presence of a ferment. The substance supposed to 

 bo decomposed must be introduced; as digestion proceeds it must disap- 

 pear, and in its place must be found a reasonable equivalent, of the sub- 

 stance supposed to be formed. Accordingly, dilute aqueous extracts of 

 the various tissues were prepared and portions taken so small that the 

 purine bases formed from the extract itself could be ignored. The purine 

 base in question was then added to the tissue extract, the material was 

 allowed to digest at 40 under antiseptic conditions, and the product 

 was finally examined for purine bases. In this way each of the glands 

 was found to possess the ferments that had been indicated by the results 

 of autodigestion. Thymus converted guanine into xanthine, and adenine 

 into hypoxanthine. Pancreas did the same. Spleen converted adenine 

 into hypoxanthine, but left guanine unchanged. Liver converted adenine 

 into hypoxanthine, and hypoxanthine into xanthine, but left guanine un- 

 changed. Three independent factors of purine fermentation are thus 

 disclosed (Jones (a), 1905). 



1. guanase, 2. adenase, 3. xanthine oxidase 



Dog's liver contains guanase but not adenase ; pig's spleen contains adenase 

 but not guanase ; neither tissue contains xanthine-oxidase. The three fer- 

 ments are therefore independent of one another. 



THE PHYSIOLOGICAL DESTRUCTION OF URIC ACID 



Many experimenters have observed that uric acid may be made to dis- 

 appear by digestion at 40 with aqueous extracts of certain glands in the 

 presence of a sufficient supply of oxygen. But the disappearance of uric 

 acid and its physiological destruction are two different things. While 

 undoubtedly an element of truth permeated all of the earlier work, this 

 work is so full of error and confusion that we must look upon much of it as 

 a fortunate accident. Uric acid was destroyed by laboratory methods used 

 in examining the products of digestion, or was lost in coagula. Its de- 

 struction product was incorrectly stated to be glycocoll, oxalic acid or 

 nothing at all. So that even now a considerable amount of ingenuity is 

 required to value the results of the early workers. A great deal of time 

 can be saved and annoyance avoided by proceeding directly to the mod- 

 ern well-established conclusion that certain tissue extracts are capable of 

 bringing about the conversion of uric acid into the more soluble allantoine 

 provided that a sufficient amount of air be supplied. (Wiechowski (a) 

 (6)(c)(d).) The gradual emergence of this truth from a mass of ob- 

 structing error is most interesting. While the principal credit is given to 

 Wiechowski, it is difficult to say who really made the discovery. 



