280 STUDIES ON FERMENTATION. 



all other vegetable cells do, the presence of oxygen, whether 

 gaseous or held in solution in liquids, this new theory would 

 lose all value, its very rakon d^etn would be gone, at least as 

 far as the most important part of fermentations 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, arrived at conclusions 

 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 supposi- 

 tion 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 experi- 

 mental proof. Moreover, since, according 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 fermentation, it follows that the whole 

 theory, commanding though it does such general assent, is 

 shown to be imtenable ; 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. Brefeld, without knowing it, operated on yeast in one of 

 the states in which it requires gaseous oxygen to enable it to 

 germinate again. A perusal of what we have previously 

 written on the subject of the revival of yeast, according to its 

 age, will show Low widely the time required for such revival 



