134 BACTERIOLOGICAL AND ENZYME CHEMISTRY 



its absence no change would take place. He considered 

 that oxygen set up, as it were, a movement among the particles 

 of the ferment which was communicated throughout the 

 liquid. The true explanation of Gay Lussac's results was 

 reserved for later investigators. 



It was Cagniard de Latour who made a careful examination 

 of the fermentation process and suggested that the decom- 

 position of the sugar was due to the growth of yeast. Shortly 

 after this began the long conflict of opinion between the 

 supporters of the purely biological and of the purely chemical 

 theory of fermentation. It was in 1836-37 that Schwann 

 furnished his famous experiment of passing air through 

 red-hot tubes and afterwards into fermentable solutions, 

 when no change took place. Gay Lussac's notion that 

 fermentation was due to oxygen was thus shown to be 

 untenable. Schwann concluded that fermentation must be 

 due to living organisms suspended in the air, which were 

 destroyed when they passed through a red-hot tube. 



The great authority of Liebig was thrown on the side of 

 the purely chemical explanation of fermentation. It was he 

 who developed the idea of catalysis, a word already invented 

 by Berzelius. Liebig compared fermentation changes to such 

 catalytic actions as have been mentioned in the first chapter 

 of this book, e.g., the effect of finely divided platinum in 

 accelerating the union of gases at low temperatures, etc. 

 He considered the ferment or catalyst to be itself in a state 

 of unstable equilibrium or decomposition, which it communi- 

 cated to its surroundings, producing chemical change, as 

 the additional snowflake may precipitate an avalanche. To 

 Liebig' s purely chemical explanation were opposed the famous 

 researches of Pasteur and Tyndall on the possibilities of 

 spontaneous generation. Briefly Pasteur's method was to boil 

 fermentable solutions in flasks provided with finely drawn 

 out necks, which after the solution was boiled would either 

 be sealed or bent in such a way that germs could not enter. 



