154 SOILS AND MANUBES 



Production of Ammonia from Proteids. The final stages 

 are simple and well understood. The changes antecedent 

 to the formation of ammonia are more obscure. It is 

 tolerably certain that amide 1 bodies, such as glycocine, 

 leucine, asparagine, tyrosine, cystine, etc., are formed in 

 most if not in all cases. 



Humus probably contains bodies of this class as well as 

 other compounds of nitrogen. They are always produced 

 by the decomposition of proteids by purely chemical means, 

 i.e., by acid or alkaline hydrolysis, and are called the 

 primary dissociation products. They are not directly 

 saponifiable, but ammonia is produced from them by the 

 action both of formless and of organised ferments, prob- 

 ably as a result of the complete or partial oxidation of the 

 non-nitrogenous part. 



1 Amides, properly so called, are acids in which the acid hydroxyl 

 is replaced by NH 2 , e.g., urea (carbamide) CO(NH. 2 )-2. In agricultural 

 chemistry the term is often used to include compounds in which an 

 alcoholic hydroxyl is replaced by NH 2 . Those mentioned in the text 

 except asparagine, which belongs to both all belong to the latter 

 type, and are more properly called amino-acids. The formulae 

 ascribed to them are as follows : 



Glycocine, amino-acetic acid, 



>NH\ rR 

 \CO / 



Leucine, isobutyl-amino-acetic acid, 



O 3 CH-CH 2 -CH 



Asparagine, amino-succinamide, 



O \?^ : ^> CH-CHo-CO-NH.> 

 \LU / 



Tyrosine, oxyphenyl-amino-propionic-acid, 



O <^cc^ 3 / CH-CH, C H 4 OH 

 Cystine, dithio-dialanine, 



