THE BEGINNINGS OF LIFE. 1 3 



universal, is only occasional, and whether this or an 

 opposite fate awaits the different fluids, is shown, as 

 already stated, to be almost wholly dependent upon their 

 nature. The comparative experiments not only lend 

 no countenance to M. Pasteur's theory, that fermentation 

 cannot be initiated without the agency of living fer- 

 ments — they are, on the contrary, wholly opposed to 

 this restriction. 



The plug of cotton-wool, or the narrow and bent 

 tube, may, it is true, protect the boiled fluid from subse- 

 quent contact with living ^ germs;' but that the fluids 

 do not undergo change on account of such deprivation 

 cannot be safely aflBrmed, when the same means would 

 also filter from the fluid some of the multitudinous 

 particles of organic matter (dead), which the air un- 

 doubtedly contains, and which may act as ferments. 

 It must be remembered that the main object of M. 

 Pasteur's investigation was to determine whether fer- 

 mentation took place under the agency of mere dead 

 nitrogenous matter, as Liebig and others affirm, or 

 whether it is only initiated by living organisms, as 

 he himself supposes. Obviously, therefore, the same 

 filtration which purified the air from any living organ- 

 isms would filter from it its nitrogenous particles, 

 which are the other possible ferments : so that no con- 

 clusion could be drawn from such experiments more 

 favourable to the one than to the other of these two 

 hypotheses. All that could have been safely affirmed 

 was, that by boiling the fluid, and then protecting it 



