70 LOUIS PASTEUR 



Pasteur, as we have seen, had been brought, 

 through his studies of molecular asymmetry, into 

 contact with the problems of fermentation. Mo- 

 lecular asymmetry as revealed by its rotary effect 

 upon light, he looked upon as a characteristic of the 

 products of life. His observation that the right- 

 handed tartrate of ammonia would ferment while 

 the life-handed one would not, suggested a relation 

 between the asymmetry of the tartrate and the 

 asymmetry of some of the compounds of the living 

 substance of the yeast plant which has been com- 

 pared to the relation of a lock and key. In regard 

 to the agents causing the decomposition of organic 

 products a number of pertinent questions suggested 

 themselves to his fertile mind. Are fermentations 

 in general caused by living organisms, or may they 

 be provoked by various kinds of albuminous mat- 

 ter? Is putrefaction due to living germs, or does 

 it occur in material that is quite free from them 

 as stated by Liebig? Is each kind of decomposi- 

 tion produced by a specific organism? In what 

 relation does the yeast plant stand to the decom- 

 position with which it is associated? Is fermenta- 

 tion due to the life of the yeast plant or is it a 

 result of death and decomposition? Here are sev- 

 eral questions which have a close relation to the 



