<i54 MAyURES THE PUTREFACTIVE FEHy.ENTATION. 



upon herbage contained only 2 per cent, of uric acid. That of a 

 pheasant fed upon barley contained, on the contrary, 14 per cent.; 

 and that of a falcon which fed upon flesh alone, yielded scarcely any 

 thing but uric acid. The urine of an ostrich was found by Fourcroy 

 and Vauquelin to contain uric acid in the proportion of about one six- 

 teenth of its mass. 



I have already given the composition of urea. Hippuric acid is 

 an azotized acid which is readily obtained by "adding a little hydro- 

 chloric acid to the fresh urine of the horse reduced by evaporation to 

 about one tenth of its original volume, when a granular crystalline 

 mass is precipitated. If the urine have been stale instead of fresh, 

 benzoic acid and not hippuric acid is obtained ; benzoic acid was, in 

 fact, long admitted as one of the elements of the urine of herbivorous 

 animals ; but it is derived from the transformation of hippuric acid 

 into benzoic acid and ammonia, the change being produced by con- 

 tact with the organic matters which putrefy so (juickly in urine. 

 Liebig was the author of this observation ; it was in operating upon 

 unchanged urine that he discovered hippuric acid. The following is 

 its composition : — 



Carbon G0.7 



Hydropcn ."i.O 



Oxyptii 2G.3 



Azute 80 



1«)0.U 



Uric acid has not yet been met with in the urine of mammiferous 

 herbivora ; but it e.vists in lliat of man, having been first discovered 

 in calculi from the bladder ; w hence it received the name of lithie 

 ncid. Liebig's analysis shows it to be composed of: — 



CarU)!! 3f).l 



llycirogeii -.4 



U.xyRcn 2S.'2 



Azoic 33.4^ 



IW).0 



The litter most commonly used to absorb the urine of stall-kept 

 animals is wheat straw, which consists in principal part of lignine 

 or woody fibre : like all vegetable tissues, however, it contains an 

 azotized [irinciple, and substances that are soluble in caustic alkalies. 

 In the aslu's of straw, we have indicated .'silica as abundant, and va- 

 rious alkaline and earthy salts, 'i'he proportion of azote appears to 

 vary in the ratio of from 3 to G per lOOO. An analysis which I made 

 of dry wheat straw gave the following ekinents : — 



G:»rl)on 4-'.4 



Ilv<lrogcn .'i.3 



Oiiyccn 38.1) 



Azoto 00.4 to 0.6 



Ashes 070 



100 



Agriculturists have, in all ages, admitted that the most powerful 

 manures are derived from animal substances, an opinion or rather a 

 fact, which, expressed in scientific language, aiAoimts to this, that 



