f# 



402 



THE BEGINNINGS OF LIFE. 



I 



process two things are necessary: in the first place^ 



there must be 2. ft 



a body capable of 



undergoing chemical change — and, in the second place, 

 there must be 2. ferment^ or substance capable of initiat- 

 ing such a change. According to 



MM 



r 



Fremy^ ^ the decomposition of organic substances under 

 the influence of a body which acts only by its mere pre- 

 sence is called fermentation/ What, then, is the nature 



of the ferment ? It has generally been regarded as some 



nitrogenous substance, belonging to the albumenoid type, 

 though subject to much variation in actual composition, 

 Gerhardteven says that ^ a ferment is not a hod.^ sut generis ^ 

 but rather any substance in a state of decomposition/ 



In the opinion of some chemists — followers of 

 Gay-Lussac — the mere presence of the ferment in com- 

 pany with the fermentable substance is not sufficient. 

 Even its activity must be excited before it can act 

 upon the fermentable substance: a result generally 

 brought about by the action of the oxygen contained in 

 the air with which the ferment is in contact ^ But 

 according to other chemists — and more especially to 



it is only necessary to have a body which 

 decomposes, perhaps spontaneously, in the presence of 

 another (fermentable substance) whose elements are 

 held together by a feeble affinity. The more change- 

 able substance, by virtue of its own inherent instability, 



1 So that, as Gerhardt says, ' L'oxyg^ne de I'air, comme nous I'avons 

 dit, est done le primum movens des fermentations,' Loc. cit. p. 540. 



Liebig ^ 



8 



Annales de Chimie et de Physique,' 2nd serie, t. Ixxi. p. 1 78 



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 lilar effects upc 

 As are known 



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 ^^t with , 



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