334 STUDIES ox FERMENTATION. 



When we laid these facts before the Academy,* M. Trecul 

 professed his inability to comprehend them : f 



"According to M. Pasteur," he said, "the yeast of beer is 

 anaerobian, that is to say, it lives in a liquid deprived of free 

 oxygen ; and to become mycoderma or peiticUUum it is above all 

 things necessary that it should be placed in air, since, with- 

 out this, as the name signifies, an aerobian being cannot exist. 

 To bring about the transformation of the yeast of beer into 

 mycoderma cerevisice or into penicillium glaucum, we must accept 

 the conditions under which these two forms are obtained. If 

 M. Pasteur will persist in keeping his yeast in media which are 

 incompatible with the desired modification, it is clear that the 

 results which he obtains must be always negative." 



Contrary to this perfectly gratuitous assertion of M. Trecul's, 

 we do not keep our yeast in media which are calculated to pre- 

 vent its transformation into penicillium. As we have just seen, 

 the principal aim and object of our experiment was to bring 

 this minute plant into contact with air, and under conditions 

 that would diWow ihe 2)eniciUinm to develop with perfect freedom. 

 "We conducted our experiments exactly as Turpin and Hoffmann 

 conducted theirs, and exactly as they stipulate that such ex- 

 periments should be conducted — with the one sole difference, 

 indispensable to the correctness of our observations, that we 

 carefully guarded ourselves against those causes of error which 

 they did not take the least trouble to avoid. It is possible to 

 produce a ready entrance and escape of pure air in the case of 

 the double-necked flasks which we have so often emploj^ed in 

 the course of this work, without having recourse to the con- 

 tinuous passage of a current of air. Having made a file-mark 

 on the thin curved neck at a distance of two or three centi- 

 metres (an inch) from the flask, we must cut round the neck at 

 this point with a glazier's diamond, and then remove it, taking 

 care to cover the opening immediately with a sheet of paper 



* Pasteur, Comptcs rendus de J' Academic, vol. Ixxviii. pp. 213-216. 

 t Teecul, Comptes rendus de V Acadeniie, vol. Ixxviii. pp. 217, 218. 



