THEORY OF FERMENTATION 329 



graphs may be briefly put in the statement that ferments 

 properly so called constitute a class of beings possessing 

 the faculty of living out of contact with free oxygen; or, 

 more concisely still, we may say that fermentation is a 

 result of life without air. 



If our affirmation were inexact, if ferment cells did re- 

 quire for their growth or for their increase in number or 

 weight, as all other vegetable cells do, the presence of oxy- 

 gen, whether gaseous or held in solution in liquids, this new 

 theory would lose all value, its very raison d'etre would be 

 gone, at least as far as the most important part of fermenta- 

 tions is concerned. This is precisely what M. Oscar Brefeld 

 has endeavoured to prove in a Memoir read to the Physico- 

 Medical Society of Wurzburg on July 26th, 1873, in which, 

 although we have ample evidence of the great experimental 

 skill of its author, he has nevertheless, in our opinion, ar- 

 rived at cpnclusions entirely opposed to fact. 



"From the experiments which I have just described," 

 he says, "it follows, in the most indisputable manner, that 

 a ferment cannot increase without free oxygen. Pasteur's 

 supposition that a ferment, unlike all other living organisms, 

 can live and increase at the expense of oxygen held in 

 combination, is, consequently, altogether wanting in any 

 solid basis of experimental proof. Moreover, since, accord- 

 ing to the theory of Pasteur, it is precisely this faculty of 

 living and increasing at the expense of the oxygen held in 

 combination that constitutes the phenomenon of fermenta- 

 tion, it follows that the whole theory, commanding though 

 it does such general assent, is shown to be untenable; it is 

 simply inaccurate." 



The experiments to which Dr. Brefeld alludes, consisted 

 in keeping under continued study with the microscope, in 

 a room specially prepared for the purpose, one or more 

 cells of ferment in wort in an atmosphere of carbonic acid 

 gas free from the least traces of free oxygen. We have, 

 however, recognized the fact that the increase of a 

 ferment out of contact with air is only possible in the 

 case of a very young specimen; but our author employed 

 brewer's yeast taken after fermentation, and to this fact 

 we may attribute the non-success of his growths. Dr. 



