CLASSIFICATION 317 



of opinion that " only small quantities of nucleo-protein 

 occur in the entire seed, and that this will be found 

 chiefly in the tissues of the embryo in which the nuclei of 

 the cells are far more abundant than in the tissues of the 

 endosperm ". 



With regard to chromo-proteins and gluco-proteins, the 

 former possibly may be represented by phycoerythrin (p. 

 249) and the latter by the mucilage which occurs in the 

 roots of Dioscorea japonica, which in many of its char- 

 acters resembles mucin from animal sources. 

 Derivatives of proteins. — In this group are included a number 

 of substances obtained by the hydrolysis of proteins ; 

 they may be sub-divided as follows : — 



1. Meta-proteins, consisting of acid albumin and 

 alkali albumin, produced respectiv^ely by the action of 

 acid or alkali on proteins. 



2. Proteoses, represented by albumose, globulose, 

 gelatose, etc. These substances are produced from pro- 

 teins by the action of digestive juices such as pepsin and 

 trypsin. 



Pepsin, which acts in an acid medium, breaks up the 

 protein as follows : — 



Protein. 



Meta-protein (acid albumin). 



Primary Proteose (precipitated by half-saturated ammonium sulphate 



and by potassium ferrocyanide in the presence of acetic acid). 

 Secondary Proteose (precipitated by saturated ammonium sulphate, but 



only slowly by potassium ferrocyanide in the presence of acetic acid). 

 Peptone (not precipitated by saturated ammonium sulphate nor by 



potassium ferrocyanide in the presence of acetic acid). 

 Polypeptides and Amino Acids. 



The formation of amino acids from peptones takes 

 place only after prolonged action. 



Trypsin, which acts in an alkaline medium, produces 

 substantially the same series of changes, only that the 

 meta-protein in this case is alkali albumin ; furthermore, 

 the decomposition into amino acids takes place more 

 rapidly than with pepsin. 



A great many seeds have been found to contain 

 proteoses after the removal of the other proteins, and 

 substances resembling the proto- hetero- and deutero- 



