FERMENTATION. 45 



being in contact with air. It is the dead portion of the 

 yeast that which has lived and is in the course of 

 alteration which acts upon the sugar. 



The new memoirs published on the subject agreed 

 in rejecting the hypothesis of any influence whatever 

 of organisation or of life in the process of fermentation. 

 Books, memoirs, dogmatic teaching, all were favourable 

 to the theoretic ideas of Liebig. If a few rare ob- 

 servers indicated the presence in certain fermentations 

 of living organisms, this presence was, in their opinion, 

 a purely accidental fact, which, instead of favouring 

 the phenomenon of fermentation, was injurious to it. 



From his first investigation on lactic fermentation 

 Pasteur was led to take an entirely different view of 

 the matter. In this fermentation he recognised the 

 presence and the action of a living organism, which 

 was the ferment, just as yeast was the ferment of 

 alcoholic fermentation. The lactic ferment was 

 formed of cells, or rather of little rods nipped at 

 their centres, extremely small, being hardly the thou- 

 sandth part of a millimeter in diameter. 1 It repro- 

 duced itself by fission that is to say, the little rod 

 divided itself at its middle and formed two shorter 

 rods, which became elongated, nipped, in their turn, 

 at their centres, each giving rise, as before, to two rods. 

 Each of these, again, soon divided itself into two, and 

 so on. Why had not this been observed prior to 



1 [A millimeter is ^th of an inch.] 



