90 



STI Dir.S ox FERMENTATION. 



shall thus obtain with most certainty spores of penicillium free 

 from impurities. 



Our readers will excuse the length of these details and the 

 minutiae of our precautions, but we shall again and again see 

 that to neglect them, or any part of them, is to expose ourselves 

 to hazard in drawing sure conclusions from facts which come 

 under our observation. 



Fig. 18. 



On June 17th, 1872, we placed some pure spores of pruicil/ium 

 in a series of three flasks containing wort (Fig. 18), observing all 

 the precautions that we have indicated. We shall designate 



We should add that, if we wish to use for our purpose spores oi penicillium 

 from a closed flask, in which the plant has fructified, we must be careful 

 not to leave the plant too long closed up. A few daj-s after the sowing 

 the growth of the fungus is arrested, in consequence of all the oxygen 

 being absorbed, and its place being sujiplied by a mixture of carbonic 

 acid and nitrogen ; and the spores, if ki'pt too long in this atmosphere, 

 will all perish. 



