i io PASTEUR 



of lactic acid. He was willing to place material at the 

 disposal of the Professor ; and Pasteur made endless 

 experiments, microscopic researches, notes, and at 

 length had the satisfaction of isolating the organism 

 which produces the lactic acid fermentation, and of 

 proving that that, and that alone, was capable of 

 setting up this particular form of fermentation. Whilst 

 in the middle of his investigations on milk and the 

 cause of its turning sour, Pasteur was summoned to 

 return to Paris, and installed as scientific Director at 

 his old college, the Ecole Normale. 



This was in 1857. The second Empire was at its 

 zenith, and the Government had little money to spend 

 on science. Pasteur had to install his laboratory in 

 a garret, without even a boy to aid him. In this 

 garret he completed his work on alcohol fermentation, 

 proved it to be ' un acte correlatif d'un phenomene 

 vital, d'une organisation de globules.' During this 

 work he noted a fact hitherto overlooked. It w r as 

 that the alcoholic fermentation is accompanied by 

 the formation of small quantities of glycerine and of 

 succinic acid, which had up till that date escaped the 

 notice of chemists. 



During the seven years which followed, Pasteur 

 was ceaselessly engaged in investigations on fermenta- 

 tion and on all those processes for which micro- 

 organisms are responsible. Whilst researching on 

 the cause of butyric acid formation, he discovered the 

 remarkable fact that the Bacillus butyricus, which 

 causes the unpleasant flavour in rancid butter, will 

 not grow in the presence of free oxygen. Until this 

 discovery it had been accepted as an axiom that all 

 living beings, plants as well as animals, require free 

 oxygen for the manifestation of their energies. Here, 

 however, was a bacillus which not only did without 

 oxygen but was injured by its presence. This obser- 

 vation, it is needless to remark, excited much adverse 



