CLASSIFICATION OF VEGETABLE PROTEINS 79 



(c) Glutelins. 



This group includes those proteins which are not dissolved by 

 neutral aqueous solutions, by saline solutions, or by alcohol. The 

 glutenin of wheat is the only well-characterised representative of this 

 group which has yet been obtained. The seeds of other cereals ap- 

 parently contain protein of similar character, but, owing to the diffi- 

 culties encountered in extracting this protein, no preparations have 

 been made which appeared to be at all definite. That such proteins 

 exist in the seeds of other cereals is assumed from experience obtained 

 in studying wheat. Wheat, rye and barley yield similar quantities of 

 albumins and globulins which appear to be identical and also nearly 

 the same quantity of protein soluble in alcohol. Protein matter can 

 be extracted from rye and barley flour by treating the residue, from 

 which the other proteins have been removed, with dilute alkaline solu- 

 tions, but the preparations obtained are manifestly impure, and, owing 

 to the difficulty of filtering the alkaline extracts, only very small 

 quantities of any of them have ever been obtained. Since much nitro- 

 gen remains in the extracted residue, it is fair to presume that the 

 greater part of it belongs to protein matter, as is the case with wheat. 

 From a bye-product of maize starch manufacture, which is known as 

 " gluten," a considerable quantity of protein can be extracted with al- 

 kaline solutions after the alcohol-soluble zein has been removed. In 

 its products of hydrolysis this protein differs, both quantitatively and 

 qualitatively, from zein, and preparations which have thus far been 

 made are probably impure preparations of the glutenin of this seed, 

 but these have not yet been sufficiently studied to justify definite 

 statements. A similar protein has been described by Rosenheim and 

 Kajiura (439) from rice under the name of oryzenin, which they state 

 represents the greater part of the protein of this seed. 



The residues of most seeds after extraction with neutral solvents 

 usually contain a small quantity of nitrogen which may or may not 

 belong to protein matter. It is probable that most of this nitrogen is 

 protein nitrogen, as alkalies usually extract from such residues a small 

 quantity of impure protein which may be either a protein of the pro- 

 perties of glutelin, or a portion of the proteins which failed to be 

 extracted by neutral solvents, either because this was contained in 

 unruptured cells which were afterwards destroyed by the alkaline 

 solution or was retained in the meal residue in combination with 

 other substances, such as nucleic acid or tannin, which rendered it 

 insoluble in neutral solutions. Although it is possible that proteins 



