CHAPTEE XIII 



THE METABOLISM OF URIC ACID AND THE OTHER 

 PURIN BODIES 



NOTHING is perhaps so bewildering in the whole of bio-chemistry 

 as are the various hypotheses regarding the metabolism of the purin 

 bodies. The discovery by Scheele in 1776 of uric acid (lithic acid) 

 in urinary calculi was followed, some years later, by a description 

 of its chemical characters by Wohler and Liebig ( 20 ). The main 

 outcome of the studies of these chemists was to show the close 

 relationship of uric acid to urea ; for example, Liebig found that 

 when uric acid was suspended in water and slowly heated with 

 peroxide of lead (mildly oxidised), it yielded urea, allantoin, and 

 oxalic acid. At this stage, and armed with little more than this 

 fact relating to its chemistry, the study of uric acid metabolism 

 in the animal was undertaken ; and for many years this subject 

 furnished a pet theme for physiological and clinical research. Most 

 of the earlier work on uric acid metabolism is, however, of very 

 little value, and for many reasons : there was no accurate method 

 for estimating uric acid in the urine ; its chemistry was little under- 

 stood ; erroneous hypotheses by eminent men biased the interpreta- 

 tion which other workers put on their results, the hypotheses being 

 considered more probable than the results when the results were 

 contrary to expectation ; no distinction was made between mam- 

 mals and birds, the results obtained on birds in which uric acid 

 is abundant and easy of estimation being directly applied to 

 explain its metabolism in mammals, in which the uric acid excretion 

 is small. 



Recently, however, dating from the discoveries by Emil Fischer 

 of the exact chemical structure of the purin bodies, and by 

 Kossel of the composition of nucleins, a great advance has been 

 made ; and, with accurate quantitative methods, we are now in 

 possession of a comparatively clear, though as yet fragmentary, 

 insight into the metabolism of the purin bodies in the animal body. 



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