the Urine in Man and Carnivorous Animals. 457 



was immaterial whether the presence of lactic acid was de- 

 tected in fresh or in putrid urine; if it was found to exist in 

 the latter, this fact must be considered as a confirmation of 

 Berzelius's examination of fresh urine; whilst its absence from 

 putrid urine would justify us positively to assert that it does 

 not form a constituent of fresh urine; and, moreover, that 

 urine contains no substance giving origin, by putrefaction, to 

 the formation of lactic acid. 



1 have come to the latter conclusion. I found it impossible 

 to detect the presence of lactic acid in putrid urine; and if 

 we examine somewhat more closely and minutely the experi- 

 ments made by Berzelius, and from which he inferred the 

 presence of lactic acid in urine, we find that not one of them 

 amounts to a positive proof that lactic acid really forms a con- 

 stituent of fresh urine. 



The experiments which I made for the purpose of ascer- 

 taining the presence of lactic acid in putrid urine are the fol- 

 lowing: — 



Putrid urine was first evaporated over an open fire, and af- 

 terwards to dryness in a water-bath ; the residue was treated 

 with a mixture of alcohol and sulphuric acid, which caused 

 the solution of phosphoric acid, hydrochloric acid, and of 

 lactic acid also, if this latter substance were really present. 

 The fluid obtained was saturated with oxide of lead, and then 

 filtered off from the phosphate, sulphate, and chloride of lead 

 formed; the lead contained in the filtered solution was sepa- 

 rated by sulphuretted hydrogen. The solution thus freed 

 from lead, and which ought to have contained the lactic acid, 

 had there been any present, was evaporated in a water-bath, 

 and the residue treated with alcohol, — a quantity of common 

 salt remained. In order to remove the soda from the alco- 

 holic solution, effloresced oxalic acid was dissolved in the 

 latter, at a high temperature, and the oxalate of soda formed 

 was separated from the fluid by filtration; the fluid was then 

 saturated with oxide of lead, which again gave rise to the 

 formation and separation of chloride of lead. The solution 

 was again freed from the lead which had dissolved sulphuretted 

 hydrogen, then concentrated in the water-bath, and basic ace- 

 tate of lead added in excess; a copious white precipitate was 

 formed, from which the fluid was filtered off. This fluid 

 must contain the lactic acid if any had been present in the 

 urine; the lead which this fluid held in solution was precipi- 

 tated by sulphuretted hydrogen, the fluid filtered off" from the 

 precipitate, concentrated in the water- bath and boiled with hy- 

 drate of bary tes, — a quantity of ammonia was expelled by this 



