the Urine in Man and Carnivorous Animals. 461 



urine presents the same long, shining, transparent, four-sided, 

 obliquely-truncated prisms, by which the hippuric acid pro- 

 cured from the urine of animals is so easily detected and di- 

 stinguished from benzoic acid. The hippuric acid of human 

 urine is not volatile at the subliming temperature of benzoic 

 acid ; at a higher temperature it undergoes fusion, forming a 

 brown-red liquid, and yields upon dry distillation the same 

 products which common hippuric acid forms under the same 

 circumstances, viz. a red-coloured oil, smelling like tonka- 

 beans, ammonia, benzoic acid, and a copious residue of car- 

 bon. It dissolves in nitric acid at a high temperature, and 

 yields, upon cooling, crystals of benzoic acid, owing to the 

 decomposition which it undergoes. 



From 0*4'99 grm. of hippuric acid produced from urine, 

 1*0791 of carbonic acid and 0-2317 of water were obtained. 

 This gives for 100 parts — 



Found. Calculated. 



Carbon . . 59-47 60-89 



Hydrogen . 5*15 4*45 



This analysis corresponds sufficiently with the calculated re- 

 sults to remove all doubt as to the nature of this acid; it will 

 be perceived that it contains 10 per cent, less carbon than 

 benzoic acid. 



As far as our investigations into the composition of the ali- 

 ments of man will allow us to judge, they contain no benzoic 

 acid from which hippuric acid might have been formed, and 

 as the urine of cows is invariably rich in hippuric acid, no 

 matter whether the cows have been fed upon hay or upon 

 beet-roots, — of which latter plants we know positively, from 

 the results of several examinations, and from experience de- 

 rived from the manufacture of beet-root sugar, that they con- 

 tain no benzoic acid, — we can come to no other conclusion 

 concerning the presence of hippuric acid in the urine of the 

 herbivorous animals, and in the urine of persons living upon 

 a mixed vegetable and animal diet, than that it is a product 

 formed in the organism, to the formation of which the ele- 

 ments of their non-nitrogenous aliments give birth. 



The presence of acetic acid in putrid urine does not war- 

 rant us to infer that this acid is also present in fresh urine; 

 on the contrary, the experiments made with regard to this 

 matter prove that fresh urine contains no acetic acid. I have 

 treated fresh urine exactly in the same manner as putrid urine, 

 and have by distillation with oxalic acid, for instance, obtained 

 a fluid of a strongly resinous odour, but not possessing any 



