STUDIES ON FEKMENTATIOX. " 81 



^ VI, — Yeast may become Dry and be Reduced to Dust 



WITHOUT LOSING ITS FACULTY OF ReI'RODUCTION. 



In the preceding paragraphs we have given examples of 

 liquids becoming impregnated with self-sown alcoliolic ferments. 

 We shall proceed to show that this little cellular plant may 

 actually exist in the form of dust, floating in the air, after 

 the manner of spores of fungoid growth and the encysted forms 

 of certain infusoria, without losing its powers of reproduction. 



On December 16th, 1872, we collected and pressed all the 

 yeast resulting from a brewing of about one hectolitre (about 

 22 gallons). From the centre of the cake we took a few 

 grammes (50 or 60 grains) of yeast, which we mixed in a 

 porcelain mortar with five times its weight of plaster — both 

 mortar and plaster having been heated, just before, in an oil bath, 

 to a temperature of about 200° 0. (392° F.), and then cooled 

 rapidly. The powder thus prepared was immediately done up 

 in a twist of paper, which had been passed through the flame 

 of a spirit lamp, and the twist and its contents were then 

 placed in an oven at a temperature of from 20° C. to 25° 0. 

 (about 75° F.). The object of these several precautions was 

 to free the powder composed of the yeast and plaster, if not 

 from the germs contained in floating particles of dust, at all 

 events from those contained in the dust existing on the surface 

 of the articles we used — the mortar, plaster, and paper. 



On December 18th, we took up with a platinum spatula. 



Fig. 14. 



previously passed through the flame, a pinch of the j^cast-and- 

 plaster powder, and sowed it in a two- necked flask (Fig. 14) 



