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CHAPTER IX. 



THE PHYSIOLOGY OF URIC ACID AND 

 OTHER URINARY DEPOSITS. 



Uric Acid : Derivation from foodstuffs ; Derivation from the 

 tissues ; The jjurin bodies ; Calcium oxalate — Cystin 



^["^HE substances which may form a crystaUine 

 X deposit in the urine are many, but we shall 

 here refer only to three, namely, uric acid and the 

 urates, oxalate of calcium, and cystin. 



URIC ACID AND THE URATES. 



For many years totally erroneous views were held 

 by physiologists with regard to the origin of these 

 substances. It has been customary to argue the 

 physiology of the mammal from that of the bird, 

 with disastrous results. Removal, or rather isola- 

 tion, of the liver in geese was shown by Minkowski 

 to diminish the output of uric acid, whilst ammonium 

 salts and lactic acid were increased in the urine. 

 Hence it was concluded that uric acid was formed 

 in the liver from ammonium salts and lactic acid ; 

 and for birds and reptiles this is true. In mammals, 

 the metabolism is totally different. The end product 

 of protein metabolism in birds and snakes is uric 

 acid ; in mammals it is urea. It by no means 

 follows, therefore, that uric acid is formed in the 



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