698 SCIENCE PROGRESS 



centage of phosphorus has not yet been definitely settled. It 

 may be mentioned here that, according to the unpublished 

 results of an investigation carried out by Dr. Kajiura and 

 the author on the proteins of rice, this cereal also contains 

 a similar substance, which forms the bulk of the rice pro- 

 teins. Curiously enough, although rice forms the staple food 

 of Oriental races, its proteins have not until now been 

 examined. 



The best-known representative of this class is gliitenin^ 

 the alcohol-insoluble part of gluten of wheat. This substance 

 may be easily prepared by the method explained above. In 

 distinction from its constant companion, the wheat gliadin, it 

 furnishes only 9 per cent, glutaminic acid, and contains 

 2 per cent, lysine amongst its cleavage products. The main 

 interest consists in its connection with gluten-formation. 

 There is still some uncertainty about the process of gluten- 

 formation and the conditions regulating it. The question is 

 an important economic one, as it is intimately connected with 

 the "strength" of flour — i.e. the property of wheat which 

 makes it pre-eminently suitable for bread-making.^ The stiff 

 coherent mass which is formed when wheat-flour is mixed with 

 cold water owes its formation to the presence of proteins, for 

 no such action takes place when pure wheat-starch is mixed 

 with cold water. The question arises whether the gluten 

 proteins exist pre-formed in the grain, or whether they are 

 produced by a secondary change. Weyl and Bischoff com- 

 pared this process to fibrin formation from fibrinogen in the 

 coagulation of blood, and they assumed the existence of a 

 ferment which transforms in the presence of water the gluten- 

 forming substances into gluten. They were, however, unable 

 to demonstrate such a ferment, and the experiments of Osborne 

 and Voorhees, although they do not exclude ferment action 

 altogether, seem to prove that gluten is formed by the chemical 

 or physical interaction of its two constituents — the gliadin and 

 glutenin. Attempts have been made to explain the relative 

 " strength " of flour from wheat and other cereals by the quan- 

 titative relationship of glutenin to gliadin. It seems, however, 

 to be more likely to depend on the physical state of the gluten, 

 which is, as already shown by Ritthausen and Osborne, 

 dependent on the presence of mineral salts. 



' See A. E. Humphries, Science Progress, vol. ii. 1907, 175. 



