244 FOOTNOTES FROM 



known writer upon the subject in the Comhill Magazine, 

 may determine the matter. " If the force given out by 

 the liquid in fermenting be the cause of the growth of the 

 plant, yeast should never be formed unless fermentation 

 is going on. If on the other hand the growth of the plant 

 be (as has been supposed by some) the cause of the de- 

 composition, then fermentation should never occur un- 

 less that growth takes place. But it is well known that 

 the yeast-plant is never developed except during fermen- 

 tation, while fermentation will take place, although more 

 slowly, without any formation of yeast. It follows, 

 therefore, that the growth depends on the decomposition, 

 and not the decomposition upon the growth. But fer- 

 mentation is excited by the addition of yeast, and pro- 

 ceeds more successfully in proportion to the rapidity with 

 which the yeast cells are developed. Why should this 

 ]>e if the formation of the living cells is only the effect, 

 and not the cause of fermentation ? The intimate con- 

 nexion of growth and decay explains this fact. The 

 yeast excites fermentation because it is itself exceedingly 

 prone to decompose ; more prone than the liquid to 

 which it is added. And in decomposing, it communi- 

 cates the impulse of its own change to the matter around 

 it, so disturbing the equilibrium of the elements, and 

 bringing about, in a few hours, chemical changes that 

 would otherwise have occupied a much longer time. And 

 this more active decomposition in the fermenting fluid 

 reacts again upon the cells of the yeast, and produces 

 in them a rapid growth and multiplication. They afford 

 the outlet, as it were, for the force given out by the chemi- 

 cal changes to which they have furnished the stimulus." 



