80 LOUIS PASTEUR 



monly designate as putrefaction is simply fermen- 

 tation which generates substances having a bad 

 smell. Commonly, but not necessarily, putrefac- 

 tions are caused by anaerobic bacteria. 



The result of Pasteur's numerous labors on fer- 

 mentation was to bring order out of chaos. No 

 longer were the phenomena obscure or mysterious. 

 Fermentation was shown to be associated with the 

 functioning of minute living organisms instead of 

 with the decomposition of dead nitrogenous matter. 

 Different kinds of organisms were proven to cause 

 each its own peculiar kind of fermentation in a 

 given substance such as sugar. The products of 

 one ferment, it was shown, might be split up again 

 by another kind of an organism. The influence of 

 these living ferments was shown to be specific or 

 limited to certain kinds of transformation. The 

 loose ideas which then prevailed concerning the 

 ready transformation of one type into another were 

 proven to be based on faulty observation or incon- 

 clusive experiments. We now know that micro- 

 organisms produce their own kind as faithfully as 

 do cabbages or turnips, and a transformation of a 

 bacterium into a yeast plant, or an infusorian would 

 nowadays be no more expected than the conversion 

 of a cow into a horse, or a maple into an oak tree. 



