62 ORIGIN OF LOWEST ORGANISMS. 



nitrogenous material which may be contained in the 

 fluid. Any exceptions to the rule should at once 

 suggest doubts as to the validity of the explana- 

 tion. 



It was shown* in 1865 by M. Victor Meunier that 

 some fluids were preserved after having been boiled in 

 a vessel of this kind, whilst others, submitted to the 

 same treatment, speedily became turbid from the pre- 

 sence of Bacteria and other organisms.t By these 

 experiments he ascertained that strong infusions did 

 frequently change, whilst weak ones might be pre- 

 served ; and that even a strong infusion might be 

 prevented from undergoing change if the period of 

 ebullition were sufficiently prolonged. 



The fluids most frequently employed by M. Pasteur 

 were yeast-water, the same sweetened by sugar, urine, 

 infusion of beetroot, and infusion of pear. 



Taking urine as a fair example of such a fluid, I 

 have found that the statements of M. Pasteur and of 

 Professor Lister are perfectly correct. This fluid may 

 generally remain for an indefinite period in such ves- 



* ' Compt. Rend.,'t. Ixi. p. 1060. 



f When boiled solutions, containing mannite, with a little 

 nitrate and phosphate of ammonia, were employed, they always 

 remained sterile. Similar negative results followed the em- 

 ployment of ox-gall. Of three decoctions of beef with 

 which M. Meunier experimented, the two stronger of them 

 were found to contain swarms of Bacteria in about twelve days. 

 Of three other flasks containing boiled urine, two also proved 

 fertile. 



