STUDIES ON FERMEMATIOX. 83 



it mixed with the plaster and absolutely inert at the bottom 

 of the saccharine liquid ; its cells were isolated, very old-looking 

 and granulated, without any appearance that might denote the 

 possibility of their ever budding again. 



Thus we determined that alcoholic ferment may be dried 

 at the ordinary temperature of the atmosphere, and preserved, 

 in the form of dust, for a period of seven months or longer, 

 without losing its faculty of reproduction. This faculty evi- 

 dently diminishes in the course of time, for our dried yeast, 

 after having been kept for seven months and a half — all the 

 other conditions of the two experiments having been precisely 

 the same — required about eight days to develop sufficiently 

 to reveal fermentation, whilst, immediately after the drying, 

 it only required three or four days to accomplish the same thing. 



Side by side with these experiments on alcoholic ferment, 

 we carried on exactly similar ones with yeast obtained from 

 "high fermentation " breweries. On December 16th, 1872, we 

 prepared a powder of this yeast and plaster as before. Our 

 last sowing took place on July 25th, 1873, in a flask of pure 

 wort, which showed signs of fermentation on July 27th. We 

 append a sketch (Fig. 16) which gives the general aspect of 



6 



Pig. 1(J. 



this " high ferment," when revived after such a lapse of time ; 

 it had preserved the distinctive features of the cells of "high 

 ferment." 



These facts can leave no doubt whatever as to the possi- 

 bility of cells of yeast existing, in a state of suspension in the 

 air, in the form of fine dust, particularly in a laboratory 

 where researches on alcoholic fermentation are pursued. 



