CHAPTER VII 

 PHYSIOLOGY OF PURIN METABOLISM 



HAVING in the last several lectures dealt with the nitrog- 

 enous end-products of protein metabolism, we may next 

 take up the difficult subject of purin metabolism. First, 

 however, it should be said that the general mass of observa- 

 tions bearing upon this phase of our subject is so huge that 

 no honest man, even if he has busied himself with nothing 

 else for years, dare feel that he has reached the bottom facts* 

 and become thoroughly conversant therewith. The author 

 would be presumptuous, moreover, being himself not con- 

 tinuously engaged in this field, but concerned rather with 

 the single purpose of tracing the general subject, to attempt 

 to surround himself here with dogmatic assertions. The 

 purpose of these lectures does not go beyond the arrange- 

 ment and presentation of a picture of this world of phe- 

 nomena so far as the writer has from honest study come to 

 understand and appreciate them ; and it should not be for- 

 gotten at any time that this picture may for other eyes have 

 a very different aspect. In the end every man has a right to 

 use his own eyes in inspecting the things about him ; only he 

 should realize that his impressions in such case are essen- 

 tially subjective ones. So much in introduction. 



Exogenous and Endogenous Formation of Uric Acid. 

 The first question to occupy us is what do we know of 

 the origin of uric acid in the mammalian body? 



In precise answer it might be replied : it originates from 

 the free nuclein bases and the nuclein bases fixed in the molec- 

 ular structure of nucleinic acids. These are in part intro- 

 duced into the living body with food (exogenous fraction) 

 and in part are freed by nuclear disintegration or other 

 processes within the living organism from its molecular com- 

 binations of which they are structurally a part (endogenous 

 fraction) . 



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