92 LOUIS PASTEUR. 



with sugar and mixed with phosphates of potash and 

 magnesia, a little sulphate of ammonia, and some car- 

 bonate of lime. In these conditions the lactic fermen- 

 tation was often seen to develop itself that is to say, 

 the sugar became lactic acid, which combined with the 

 lime of the carbonate to form lactate of lime. This 

 salt crystallises in long needles, and ends sometimes by 

 filling the whole vase, while a little organised living 

 thing is at the same time produced and multiplied. If 

 the experiment is carried on further, another fermenta- 

 tion generally succeeds to this one. Moving vibrios 

 make their appearance and multiply, the lactate of lime 

 disappears, the fluidity returns to the mass, and the 

 lactate finds itself replaced by butyrate of lime. What 

 a succession of strange phenomena ! How did life 

 appear in this sweetened medium, composed originally 

 of such simple elements, and apparently so far re- 

 moved from all production of life? This lactic fer- 

 ment, these butyric vibrios, whence do they come ? 

 Are they formed of themselves ? or are they produced 

 by germs ? If the latter, whence do the germs come ? 

 The appearance of living organised ferments had be- 

 come for Pasteur the all-important question, since in 

 all fermentations he had observed a correlation between 

 the chemical action set up and the presence of micro- 

 scopic organisms. Prior to the establishment of the 

 facts already mentioned, these difficulties did not exist. 

 The theory of Liebig was universally accepted. 



