86 THE CHEMISTRY OF CATTLE FEEDING 



glucosides (p. 87), saponification of fats, and the peptonisa- 

 tion of proteins, all belong to this type. 



(3) Oxidation, eg. the conversion of alcohol into acetic 

 acid. 



C 2 H 5 OH + 2 -> C 2 H 4 2 + H 2 



(4) Reduction : changes which result in the formation of 

 hydrogen and substances containing a smaller proportion of 

 oxygen than the original compounds, e.g. formation of butyric 

 acid, etc., from lactic acid. 



2C 3 H 6 O 3 -> C 4 H 8 O 2 + 2CO 2 + 2H 2 



In addition to the compounds formed by the main reaction, 

 others are also produced by secondary changes, or by changes 

 of a different kind, which take place simultaneously in nearly 

 all fermentations. What actually occurs, therefore, cannot, as 

 a rule, be represented by a single chemical equation. Many fer- 

 mentations are extremely complex, and probably involve several 

 changes of different types at once, e.g. oxidation or reduction 

 together with hydrolysis and simple decompositions, each of 

 which may proceed in many different directions. The trans- 

 formations known generally under the name of putrefaction, 

 those which take place during the ripening of cheese, and pos- 

 sibly also certain stages in the processes of digestion, are of 

 such a complex character. When the changes occur under 

 carefully regulated conditions, the results are of a more or less 

 specific character, but the products are not constant either 

 qualitatively or quantitatively. 



The decomposition of cellulose, which takes place under 

 the anaerobic conditions prevailing in marshy soils, is probably 

 a very complex process ; but, as methane and free hydrogen 

 are amongst the products, it may be regarded as mainly a pro- 

 cess of reduction. Changes of a somewhat similar character 

 appear to take place during the digestion of cellulose by 

 herbivorous animals. The process has been artificially imi- 

 tated by inoculating nutritive matter with the contents of dif- 

 ferent portions of the alimentary tract. Two different types 

 of fermentation were observed, characterised by preponderance 



