ULTIMATE CONSTITUTION OF URIC ACID. 14! 



known but very imperfectly. Unlike pseudo-uric acid, it really 

 results from the absorption of water by uric acid, and is produced 

 in the form of its potassium-salt by boiling uric acid for a long 

 time in solution of caustic potash. In the free state it occurs as 

 a white, glistening, sparingly soluble powder. The absorption of 

 a fourth atom of water by uric acid would doubtless lead, not to 

 the formation of a new hydrate, but to the breaking up of the 

 acid itself, most likely into tartronic acid and urea. 



(148.) I have already referred to upwards of forty uric acid 

 products, by no means all that are known, and I have indicated 

 the existence of many more, as yet unknown, to fill up gaps in 

 the different series. Now, when we reflect that in all probability 

 most of these compounds, actual and problematical, do not stand 

 alone, but are associated each with a more or less numerous set 

 of isomers, that is to say, of bodies having the same ultimate 

 composition, but a different molecular arrangement we scarcely 

 venture to contemplate the almost overwhelming intricacy with 

 which we are threatened. To us, as physicians, however, the 

 subject is capable of assuming a simpler aspect. On any view of 

 its constitution, hydrated uric acid differs in composition from 

 two atoms of urea by the addition of three atoms of carbonic 

 oxide CO, capable of oxidation into carb-anhydride C0 2 , and by 

 that oxidation of generating a certain amount of heat, or its equi- 

 valent of motion : 



Water "Uric acid Oxygen Carb-anhyd. Urea 



*H a O -f C 5 N 4 H 4 3 + C 



or C 3 3 (CN a H 4 0) 3 



CM 

 3 [ 



Hence, uric acid must be considered to result from an incomplete 

 oxidation of nitrogenous tissue, whereby, in addition to urea, 

 carbonic oxide is produced instead of carbonic anhydride. In 

 accordance with this deduction, then, we are not surprised to 

 find that the tissue-metamorphosis of reptiles, whose motions are 

 so sluggish and temperature is so low, should yield imperfectly 

 burned and used carbonic oxide in the form of uric acid, or 

 rather ui#te of ammonia, instead of the perfectly burnt and used 

 carb-anhydride excreted by mammals. On the other hand, this 



