the Urine in Man and Carnivorous Animals. 463 



that these two substances, under the circumstances, cannot 

 give rise lo the formation of lactic acid, Jior to that of acetic 

 acid. The putrefaction of urea seems to be completely pre- 

 vented by the presence of sugar, or milk-sugar; at least, in 

 several experiments where one or the other of these two sub- 

 stances were present in the putrefying urine, the urea of the 

 urine had not, even after the lapse of three months, acquired the 

 property of eflf'ervescing with acids. I must here remark that 

 a considerable amount of ammonia is formed in the process 

 of putrefaction, owing to the resulting decomposition of an- 

 other nitrogenous organic substance. This ammonia causes 

 the protoxide of copper, formed upon testing the urine for 

 milk-sugar with potass and sulphate of copper, to remain in 

 solution, and to precipitate only upon the addition of acetic 

 acid. 



It follows from the preceding experiments and observations, 

 that the organic acids in the urine of man are uric acid and 

 hippuric acid, and another nitrogenous matter (most probably 

 the colouring matter of urine), which latter substance, upon 

 the access of air, resolves itself into acetic acid, and a substance 

 resembling resin. Gay Lussac has already observed that it 

 is only upon the access of air that urine passes into a state of 

 putrefaction with absorption of oxygen*. 



The considerations which I shall next adduce will prove 

 sufficient to remove all doubt as to the cause of the acid re- 

 action manifested by the urine of man. 



It must be assumed as an irrefutable fact, that the inorganic 

 bases present in urine, such as potass, soda, lime, &c., have 

 enteretl the organism through the medium of the aliments. 



Now, in the first place, with respect to the nutriment of 

 man, assuming it to consist of meat, that is, of animal sub- 

 stances and of aliments prepared from the flour of the cereals, 

 or of the seeds of leguminous plants, such as peas, beans, and 

 lentils, we know exactly the constitution of the ashes of flesh, 



* Urine which, as is well known, speedily putrefies and passes from an 

 acid to an alkaline state, keeps very long in well-closed vessels, when it has 

 scarcely been allowed to come into contact with the air. It retains, in such 

 case, its transparency, acidity, and odour; it deposits only uric acid, and 

 not the phosphate of ammonia and magnesia. If urine is left in contact 

 with a small amount of air it speedily absorbs the oxygen present, and de- 

 composition then ceases; hut if a sufficient amount of oxygen is present, a 

 considerable amount of carbonate of ammonia is formed, and phosphate of 

 lime and phosphate of magnesia and ammonia precipitate. It will be per- 

 ceived that the decomposition of urine has no analogy in this respect with 

 fermentation, since this latter process once set afloat continues without the 

 co-operation of oxygen. — Gay Lussac, Ann. de Chitnie, vol. Ixxvi, p. S45. 



