fllB' 



422 



THE BEGINNINGS OF LIFE. 



growth and reproduction of the old^ goes on simul- 

 taneously with the production of new living matter. 



Looked at from a chemical point of view, the most 

 essential feature of these changes seems to be that they 

 are successive, similar changes, induced by mere con- 

 tact with another body"^. As we have previously stated, 

 however, such changes do not form a group apart, they 

 blend insensibly into chemical actions in general. 

 To speak of certain chemical changes, therefore, as 

 fermentations, as though they were different in kind 



others, to be included in this category, it appears to 

 me that, from one important point of view, they may 

 be included under three principal groups 2. 



no new production of yeast either by growth or evolution, if no nitrogen 



xxists. 



We 



1 See the definition ofPelouze and Fr^my at p. 402. Liebigsays: 

 can resolve with a given quantity of sulphuric acid unlimited quantities 

 of alcohol into ether and water ; we can, by the help of the same acid, 

 convert a quantity of starch into grape sugar, without the acid bemg 

 neutralized in either case. These effects are utterly distinct from the 

 effects produced when sulphuric acid acts on metals or metallic oxides; 

 but it is quite absurd to ascribe them to a peculiar cause, altogether 

 -different from chemical affinity.' (Letters on Chemistry, 185T, p. 263.) 



2 These views are submitted, with all deference, to the consideration of 



chemists. 



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Thus, as 

 ^ith stroni 

 of cyanogei^ 



t dements of c)' 

 of the simple 



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:sch changes mie 



from other chemical changes, may be convenient, though H, [AnaljM Fen 



it must be acknowledged to be a mere arbitrary distinc- aiainore or less 



tion, and not justifiable from a philosophical point of ■« simpler pr 



view. Limiting ourselves, however, to such processes ;mtact with sulp 



as seem best entitled, in the opinion of Liebig and ijmsf^ or whi 



i, breaks up into 



111. [Analpico-syn 



I hfo processes 



( 



formed: (Liebig on Alcoholic Fermentation, loc. cit.) When a small •'' Substance brca 



quantity of yeast is added to a simple solution of sugar, there can be ;|j 



*^ products «. 

 may be cite 



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vol. 

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11. ch 



^P. xii. 



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