220 THE LIFE OF PASTEUR 



aerobia — that is, a being to the life and development of which 

 air was necessary — became, after being submerged, an 

 anaerobia, that is, a creature living without air in the depths of 

 the liquid, and behaving after the manner of ferments. 



This extended the notions on aerobian and anaerobise which 

 Pasteur had formerly discovered whilst making researches con- 

 cerning the vibrio which is the butyric ferment, and those 

 vibriones which are entrusted with the special fermentation 

 known as putrefaction. Between the aerobiae who require air 

 to live and the anaerobiae which perish when exposed to air, 

 there was a class of organisms capable of living for a time 

 outside the influence of air. No one had thought of studying 

 the mouldiness which develops so easily when in contact with 

 air ; Pasteur was curious to see what became of it when sub- 

 mitted like the mycoderma to that unexpected regime. He saw 

 the penicillium, the aspergillus, the mucor-mucedo take the 

 character of ferments when living without air, or with a quan- 

 tity of air too small to surround their organs as completely as 

 was necessary to their aerobia-plant life. The mucor, when 

 submerged and thus forced to become an anaerobia, offers bud- 

 ding cells, and there again it seemed as if they were yeast 

 globules. 'But," said Pasteur, "this change of form merely 

 corresponds to a change of function, it is but a self -adapta- 

 tion to the new life of an anaerobia." And then, generalizing 

 again and seeking for laws under the accumulation of isolated 

 facts, he thought it probable that ferments had, "but in a 

 higher degree, a character common to most mucors if not to all, 

 and probably possessed more or less by all living cells, viz., to 

 be alternately aerobic or anaerobic, according to conditions of 

 environment." 



Fermentation, therefore, no longer appeared as an isolated 

 and mysterious act; it was a general phenomenon, sub6rdinate 

 however to the small number of substances capable of a de- 

 composition accompanied by a production of heat and of being 

 used for the alimentation of inferior beings outside the presence 

 and action of air. Pasteur put the whole theory into this 

 concise formula, " Fermentation is life without air." 



'It will be seen," wrote M. Duclaux, "to what heights 

 he had raised the debate ; by changing the mode of interpreta- 

 tion of known facts he brought out a new theory." 



But this new theory raised a chorus of controversy. Pasteur 

 held to his proofs ; he recalled what he had published concern- 



