238 MEDICINE 



local industry. Pasteur's passion for knowledge 

 was only approached in intensity by his desire to 

 make that knowledge useful to his country, and 

 his surroundings at Lille stimulated the already 

 keen desire to explore the whole subject of fermen- 

 tation experimentally. He set himself to such 

 experiments with great energy, the use of the 

 microscope going hand in hand with chemical 

 studies. He investigated among other cases the 

 lactic acid fermentation which brings about the 

 souring of milk, the butyric fermentation, and, 

 in particular, alcoholic fermentation. To enlarge 

 upon the importance of these, his earlier studies, 

 would require pages; a bald statement calls for 

 some imagination to illumine it. Briefly stated, 

 what Pasteur established at this time was as follows : 

 (i) The deepseated chemical changes which occur 

 in fermentations of the kind studied are due to 

 the presence and influence of living organisms, and 

 not, as was believed and taught at the time, to the 

 supposed circumstance that putrefying animal or 

 vegetable matter transmits, in some very mysterious 

 way, its state of active decomposition to other 

 substances. (2) There is a special kind of organism 

 the activities of which are correlated with each 

 kind of fermentation. (3) Such organisms (bac- 

 teria, yeasts, etc.), are not born spontaneously in 

 the decomposing or fermenting material, but are 

 derived from 'infection.' They are born of parents 

 like unto themselves, and multiply when they 



