STUDIES ON FERMENTATION. 263 



selves more and more on our minds, in spite of a prima facie 

 improbability. This is exactly the character of those ideas 

 which we have just expounded. We propounded them in 1861, 

 and not only have they remained unshaken since, but they have 

 served to foreshadow new facts, so that it is much easier to 

 defend them in the present day than it was to do so fifteen years 

 ago. We first called attention to them in various notes, which 

 we read before the Chemical Society of Paris, notably at its 

 meetings of April 12th and June 28th, 1861, and in papers in 

 the Coniptes rendus de VAcadhnie des Sciences. It may be of 

 some interest to quote here, in its entirety, our communication 

 of June 28th, 1861, entitled, " Influences of Oxygen on the 

 Development of Yeast and on Alcoholic Fermentation," which 

 we extract from the Bulletin de la Societe Chimique de Paris : — 



" M. Pasteur gives the results of his researches on the fer- 

 mentation of sugar and the development of yeast-cells, accord- 

 ing as that fermentation takes place apart from the influence 

 of free oxygen or in contact with that gas. His experiments, 

 however, have nothing in common with those of Gay-Lussac, 

 which were performed with the juice of grapes, crushed under 

 conditions where they would not be afiected bj' air, and then 

 brought in contact with oxygen. 



" Yeast, when perfectly developed, is able to bud and gro w 

 in a saccharine and albuminous liquid, in the complete absence 

 of oxygen or air. In this case but little yeast is formed, and a 

 comparatively large quantity of sugar disappears — sixty or 

 eighty parts for one of yeast formed. Under these conditions 

 fermentation is very sluggish. 



" If the experiment is made in contact \vith the air, and 

 with a great surface of liquid, fermentation is rapid. For the 

 same quantity of sugar decomposed much more yeast is formed. 

 The air with which the liquid is in contact is absorbed by the 

 yeast. The yeast develops very actively, but its fermentative 

 character tends to disappear under these conditions ; we find, in 

 fact, that for one part of yeast formed, not more than from four 

 to ten parts of sugar are transformed. The fermentative 



