420 THE BEGINNINGS OF LIFE. 



Gruithuisen's experiment and one of my own with the 

 same fluid. Let him fill a stoppered bottle with a boiled 

 infusion of hay or turnip and then close it hermetically, 

 and he will almost certainly find, as I and others have 

 found, that such an infusion will keep for an indefinite 

 time without exhibiting any trace of turbidity ] . Let 

 him, at the same time, treat some of the same boiled 

 infusion of hay or turnip in a different manner : let it 

 only half fill a hermetically-sealed flask from which all 

 air has been expelled. He will then learn, better than 

 by any amount of mere idle conjecturing, whether there 

 is any real contradiction between the results of my 

 experiments, and generally admitted facts. 



The conclusions to which I have been compelled to 

 arrive, therefore, on the subject of Fermentation, are 

 these. The c Vital theory' is untrue on account of its 

 exclusiveness ; some organisms are ferments, though all 

 ferments are not organisms. Organisms may be either 



1 Although hay and other infusions will yield these results which are 

 comparable with the majority of cases in which provisions are properly 

 preserved in tins still it has been shown by M. Pouchet (' Nouvelles 

 Experiences,' Paris, 1864, p. 190), that beer-wort which has been boiled 

 will undergo change even in a full vessel, and give rise to an abundance 

 of yeast-cells. This, therefore, is an example which is comparable with 

 those exceptional cases in which meats undoubtedly become putrid in 

 spite of every care in their preparation, and notwithstanding the fact of 

 their being contained in filled-tins which are hermetically closed. Some 

 fermentations are doubtless attended by a less copious emission of waste 

 gases than that which characterizes other fermentations ; and some 

 fermentations will progress in spite of an amount of pressure which, 

 in other cases, would quite put a stop to the process. 



