126 ANIMAL CHEMISTRY LECTURE VI. 



LECTURE VI. 



Uric acid Its excretion throughout the animal kingdom History of its 

 chemical examination Its undecomposibility save by oxidation Pro- 

 bable pre-existence in it of urea Classification of uric acid products into 

 an-ureides, mon-ureides, and di-ureides Also into carbonic, oxalic, and 

 mesoxalic compounds Oxidation of mesoxalic into oxalic, and of oxalic 

 into carbonic acid TJreides formed by an elimination of either one or two 

 atoms of water Hydrogenised carbonic, oxalic, and mesoxalic compounds 

 Table of uric acid products Additional intermediate and amidated bodies 

 Oxalic mon-ureides and di-ureides Mesoxalic mon-ureides associated 

 with barbituric acid Mesoxalic di-ureides, including hypoxanthine, xan- 

 thine, and uric acid Their mutual convertibility Eelationship of xan- 

 thine to guanine The pseudo-uric and uroxanic acids Uric acid viewed 

 simply as a compound of carbonic oxide and urea Excretion of urate of 

 ammonia by birds and insects Dynamic values of oxidation into uric 

 acid and urea respectively Function of lungs supplemented by discharge 

 of uric acid from kidneys Tissue metamorphosis affected by alterative 

 medicines Activity of loosely combined oxygen Nitric oxide as a carrier 

 of active oxygen Comparison of iodine with nitric peroxide Eesem- 

 blances and differences between iodine and chlorine Their actio*n as 

 oxygenants in presence of water Free chlorine more active than iodine, 

 and combined iodine more mobile than chlorine Eeducing action of iod- 

 hydric acid Alterative action of iodine dependent on its chemical mobi- 

 lity Similar characters of arsenic, mercury, &c. Effect of alkalies on 

 tissue-oxidation Gorup-Besanez's experiments with ozone Conclusion. 



(134.) OF all the incompletely oxidised products of tissue- 

 metamorpliosis, uric acid is, I suppose, the most important, whe- 

 ther regarded from a physiological and pathological, or from a 

 purely chemical point of view. In combination, chiefly with 

 ammonia, it forms the principal urinary constituent voided by 

 insects, land -reptiles, and birds. Normally, it occurs but in 

 small proportion in the urine of man, while it is found in yet 



