THE BEGINNINGS OF LIFE. 423 



I. (Synthetic Fermentations^] In this group the changes 

 that occur are wholly synthetic, leading to the evolution 

 of compounds which have a higher molecular com- 

 plexity. Thus, as Schmitz and Glutz have observed, 

 contact with strong hydrochloric acid causes the con- 

 version of cyanogen into oxamide (C 2 N 2 -f-2H 2 O=C 2 

 O 2 N 2 H 4 ), by bringing about a combination between 

 the elements of cyanogen and those of water. This 

 is one of the simplest examples, though a large number 

 of such changes might be cited 1 . 



II. (Analytic Fermentations.) In these cases we find 

 that a more or less complex body breaks up into two 

 or more simpler products, as when starch and water, 

 in contact with sulphuric acid, is converted into dextrin 

 and glucose ; or when salicin, in contact with the same 

 acid, breaks up into saligenin and glucose. 



III. (Analytlco-synthetlc Fermentations^] In this group 

 the two processes occur simultaneously the ferment- 

 able substance breaks up into simpler compounds, and 

 at the same time gives origin to higher and more 

 complex products 2 . As a simple instance of such a 

 change may be cited the fact, that tartaric acid, when 

 heated, not only yields such lower derivatives as water 

 and carbonic acid, but also the decidedly more com- 



1 See vol. ii. chap. xii. p. 24. 



2 This is an occasion most favourable for the production of higher 

 compounds. Elements or compounds always unite most freely ' when 

 one or both are in the act of separating from some previous combination. 

 The state in which they are at that moment is called by chemists the 

 status nascens, or nascent state.' (Liebig.) 



