PREFACE. ix 



it was also maintained that no fermentation could 

 be initiated without the agency of living things 

 in fact, that all ferments were living organisms. 

 The former may be called the physical theory of 

 fermentation, of which Baron Liebig is the most 

 prominent modern exponent ; whilst the latter may 

 be termed the vital theory of fermentation, and this 

 is the doctrine of M. Pasteur. All the facts which 

 I have to adduce, so far as the subject of fermenta- 

 tion is concerned, are wholly in favour of the 

 views of Baron Liebig. 



And, the conclusions arrived at in this work are 

 confirmed by the results of several unpublished 

 experiments, in which living organisms have been 

 taken from flasks that had, a few weeks before, been 

 hermetically sealed and heated for a variable time to 

 temperatures ranging from 260 F. to 302 F. 



With the view of aiding some of my readers 

 in their interpretation of the results of some of 

 the experiments contained in this volume, I would 

 call their attention to the following considerations. 

 If fluids in vacuo (in hermetically-sealed flasks), 

 which were clear at first, have gradually become 

 turbid ; and if on microscopical examination this 

 turbidity is found to be almost wholly due to the 

 presence of Bacteria or other organisms, then it 



