120 YEAST IV 



shows that, if a little yeast be introduced into 

 such wort, after it has cooled, the wort at once 

 begins to ferment, even though every precaution 

 be taken to exclude air. And this statement has 

 since received full confirmation from Pasteur. 



On the other hand, Schwann, Schroeder and 

 Dusch, and Pasteur, have amply proved that air 

 may be allowed to have free access to beer-wort, 

 without exciting fermentation, if only efficient 

 precautions are taken to prevent the entry of 

 particles of yeast along with the air. 



Thus, the truth that the fermentation of a 

 simple solution of sugar in water depends upon 

 the presence of yeast, rests upon an unassailable 

 foundation; and the inquiry into the exact 

 nature of the substance which possesses such a 

 wonderful chemical influence becomes profoundly 

 interesting. 



The first step towards the solution of this 

 problem was made two centuries ago by the patient 

 and painstaking Dutch naturalist, Leeuwenhoek, 

 who in the year 1680 wrote thus : — 



"Ssepissime examinavi fermentum cerevisise. semperqne hoc 

 ex globulis per materiam pellncidam fluitantibiis, qnam cere- 

 visiam esse censiii, constare observavi : vidi etiara evider_tissime, 

 unumqueinque hujus fermenti globiilnra denuo ex sex distinctis 

 globulis constare, accurate eidem quantitate et fornise, cui 

 globulis sanguinis nostri, respondentibns. 



*' Verum talis mihi de horam origine et formatione conceptus 

 formabara ; globulis nempe ex qnibus farina Tritici, Hordei, 

 Avenee, Fagotritici, se constat aquae calore dissolvi et aquse com. 



