SYSTEMATICALLY SELECTED YEASTS. 



59 



described by P. Lindner, Brown and Morris, Wichmann, 

 Thausing, the Chicago Experimental Station, and others. 



Velten, as long ago as 1878, 

 had patented his so-called 

 " generateur." For the pur- 

 pose of purifying the air he 

 employed heat in accordance 

 with Schwann's method, and as far as can 

 be judged from the imperfect description 

 of his apparatus, the construction of the 

 latter is altogether faulty. It was, indeed, 

 never employed outside his brewery at Mar- 

 seilles, and the main reason for this is that what was most 

 essential was wanting namely ', pure yeast itself (see p. 1 36). 



