314 LOUIS PASTEUR 



of conidia. In mitcor, again, they are very marked, the 

 inflated filaments which, closely interwoven, present chains 

 of cells, which fall off and bud, gradually producing a mass 

 of cells. If we consider the matter carefully, we shall see 

 that yeast presents the same characteristics. * * * * 



It is a great presumption in favor of the truth of theoretical 

 ideas when the results of experiments undertaken on the 

 strength of those ideas are confirmed by various facts more 

 recently added to science, and when those ideas force them- 

 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 pronounced 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 So- 

 ciety of Paris, notably at its meetings of April I2th and 

 June 28th, 1861, and in papers in the Comtes rendus de 

 I'Academie 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 Develop- 

 ment of Yeast and on Alcoholic Fermentation," which we 

 extract from the Bulletin de la Societt Chimique de Paris: 



" M. Pasteur gives the result of his researches on the 

 fermentation of sugar and the development of yeast-cells, 

 according 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 affected by air, and then brought into contact with 

 oxygen. 



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

 grow in a saccharine and albuminous liquid, in the com- 

 plete absence of oxygen or air. In this case but little yeast 

 is formed, and a comparatively large quantity of sugar dis- 

 appears sixty or eighty parts for one of yeast formed. 

 Under these conditions fermentation is very sluggish. 



"If the experiment is made in contact with the air, and 



