372 WILLIAM ROBERT SMITH. 



ferment, and later on Boerhaave, in a work published in London 

 in 1732, makes direct mention of the presence of ammonia in 

 urine as the result of decomposition. 



The source of the ammonia was, however, first clearly under- 

 stood in 1799, when Cruickshank, Fourcroy, and Vauquelin 

 discovered urea, the two latter observers showing that carbonate 

 of ammonia was the principal product of its distillation, and 

 they further pointed out the relationship between the conver- 

 sion of urea in solution in water into carbonate of ammonia by 

 heat, and the spontaneous " fermentative " decomposition of 

 urine. With a more accurate knowledge of the composition of 

 urea the reason of its conversion into carbonate of ammonia 

 became clearer, but the discovery of Proust that freshly voided 

 urine could be kept for years in a well-stoppered flask without 

 undergoing any change first led him to conclude that the action 

 of air, especially of its oxygen, was necessary for its decompo- 

 sition. Later authorities attributed the decomposition to the 

 presence of a ferment^ taking its origin in the putrid destruction 

 of the mucus. 



Our ideas on the subject were, however, thoroughly changed 

 by the work of Pasteur in 1860. He introduced fresh urine 

 into a glass flask, boiled it for a few minutes, and then efi'ectu- 

 ally closed the flask by fusing its neck. He then found that 

 urine thus treated remained fresh for an indefinite period. 

 If, after the lapse of five or six weeks, he introduced into such 

 urine pieces of asbestos which had been freely exposed to the 

 air, decomposition speedily occurred, giving rise to the am- 

 moniacal smell and the development of numerous organisms, 

 monads, vibriones, bacteria, &c. If, however, the asbestos, 

 previous to its introduction, had been well heated in a blow- 

 pipe flame, no change whatever took place in the urine. It 

 was thus clearly shown that the ammoniacal change in urine 

 was directly owing to the introduction of germs from the air, and 

 subsequently Pasteur and Van Tieghem' showed that in every 

 fermenting ammoniacal urine the presence of micro-organisms 



1 "Reclierches sur la fermentatiou de I'uree, etc.," ' Comptes rendus,' T. 

 Iviii, p. 210—264, 1864. 



