THE METABOLISM OF THE PURIN BODIES 413 



Haig, part at least of that which disappears becomes deposited 

 in an insoluble form in certain of the tissues, to be very gradually 

 removed by leucocytes. If this be a correct explanation, a much 

 larger amount of similarly injected hypoxanthin, which is readily 

 soluble in the tissue fluids, should be excreted in the urine. 

 Experiments show, however, that in this case also one-twentieth of 

 the injected hypoxanthin appears in the urine. We must conclude, 

 therefore, that it is destroyed. 



By what chemical process does this destruction take place ? In 

 the laboratory, uric acid may be decomposed by various agencies, 

 and the end products are different according to which of these 

 is used. The most important agencies, it will be remembered, 

 are: (1) Hydrolysis heating to 170 C. in a closed tube with 

 hydrochloric acid, yields glycin, carbonic anhydride, and am- 

 monia. (2) Mild oxidation treating with potassium perman- 

 ganate or with peroxide of lead, yields allantoin and carbonic 

 anhydride. (3) More powerful oxidation with nitric acid yields as 

 ultimate products oxalic acid and urea. To determine by which 

 of the processes destruction of the purin ring takes place in the 

 organism, it will be necessary to find out which of the possible 

 decomposition products becomes increased in the tissues or excreted 

 in excess after extensive purin break-down. 



Of the decomposition products above indicated, urea, allantoin, 

 and oxalic acid are normal constituents of the urine, although the 

 latter two only in minute traces, and glycin is a constituent of the 

 tissues. An increase in urea excretion could result from purin 

 destruction by any of the three ways indicated, for glycin, pro- 

 duced by the first process, and possibly the allantoin, produced by 

 the second, might be converted into urea before being excreted. 

 An increase of allantoin could only result from a process akin to 

 the second reaction, whereas an increase of oxalic acid might mean 

 processes like the second and third, for oxidation of allantoin in the 

 laboratory yields urea and oxalic acid. 



With regard to glycin^ most authors have considered this 

 rather as a precursor of uric acid than as one of its decom- 

 position products. As a matter of fact, however, Wiener ( 18> 20 ) 

 has definitely shown it to be a decomposition product, at 

 least in the rabbit. In these, as in all herbivorous animals, a 

 large part of the glycin in the organism unites directly with 

 benzoic acid in the kidney to form hippuric acid. If a large 



