12 BACTERIA, YEASTS, AND MOLDS 



time, the German, Liebig. The history of bacteriology is 

 full of controversies between the French and the German 

 scientists; Pasteur, it will be seen, started the fashion 

 even before bacteriology had really come into existence. 

 The name of Liebig is best known to the housewife to-day 

 from the beef extract that bears the name; but his real 

 reputation is in far different fields. He was, without ques- 

 tion, one of the greatest chemists of the middle of the 

 century. By the time Pasteur began his work, Liebig had 

 won, and thoroughly deserved, an outstanding reputation. 

 It happened, however, that he made one mistake; and 

 Pasteur was successful in pointing out Liebig's error. 

 Liebig had scoffed at the idea that the microorganisms 

 seen in deca}dng organic matter were the cause of the 

 fermentations taking place; he insisted that fermentation 

 was a purely chemical process that took place in organic 

 matter if conditions were right, just as combustible ma- 

 terial in which a flame had once started would continue to 

 bum by purely chemical action. Others before Pasteur 

 had shown that such material would not decompose if it 

 was sterihzed and the microorganisms kept out but that 

 the fermentations would begin as soon as they were intro- 

 duced. Liebig could easily answer such an argument by 

 saying that Just as a pile of wood could not bum until the 

 conflagration had been kindled by a small flame,, so or- 

 ganic matter would not begin to decompose until the 

 process had been started by the spontaneous decomposi- 

 tion of the dead bodies of these microorganisms. This 

 answer convinced every one for many years ; Liebig was 

 too great a man to oppose lightly. But Pasteur proved 

 that he was mistaken. He showed that the same material 



