88 STUDIES ON FERMENTATION. 



The operator, without knowing it, may frequently sow, 

 besides the penicillium, which is all he can see, spores of mucor 

 Diucedo and mycoclerma vini, in short, of all the most common 

 fungoid growths. 



This process of impregnation, therefore, does not afford us 

 sufficient safeguards, but b3aneans of the following device we shall 



Fig 



render it more satisfactor3^ Let us take a series of flasks shaped as 

 in Fig. 17, containing an organic liquid suitable to the develop- 

 ment of fungoid growths, that is to say, slightly acid — yeast- 

 water, plain or sugared, the wort of beer, or Raulin's fluid* 



course of time, the number of those changing and the nature of their 

 changes being in close proportion to the probable number and nature 

 of the floating germs able to develop in the particular nutritive 

 liquid used. If we work at great elevations, far from houses and 

 the dirt of towns and inhabited plains, as we did at Montanvert, 

 near the 3fer de 0/ace, change will seldom occur. The opposite will be 

 the case if we work in a place like the living-room of the little, dirty, • 

 ill-kept inn at Montanvert. In a laboratory where fermentation is 

 studied we obtain certain kinds of germs which often differ from those 

 found in the air of the open country. If we desii'e to have organisms in 

 all our flasks, we have only to stir up the dust on the ground or on sur- 

 rounding objects at the moment when we open the flasks. This simple 

 and easy experiment clearly shows us that it is impossible for a field of 

 sporanges of fungoid growth, existing in an uncovered vessel or on the 

 surface of a fruit, to escape becoming mixed with germs that are foreign 

 to the little plant ; in other words, the student who sows spores of 

 penicilUam, which ho has collected from one place or another on a brush, 

 exposes himself to serious causes of error. 



* M. Jules Rauliu has published a well-known and remarkable work 

 on the discovery of the mineral modium best adapted bj' its composition 



