SUMMARY. 117 



Their proportion is also nearly the same, for practically the same amount of 

 gliadin can be obtained from the gluten as from the flour, if allowance is 

 made for the small amount of gluten that is mechanically carried away in 

 the process of washing out the starch. This loss is largely made up by the 

 presence of non-protein constituents in the gluten, so that the weight of the 

 dried gluten usually corresponds closely with the amount calculated for the 

 sum of gliadin and glutenin, as computed from the nitrogen belonging to 

 these proteins. 



The gluten is not formed from globulins by the action of a ferment in a 

 manner analogous to the formation of fibrin from fibrinogen, as was asserted 

 at one time. The observations on which this supposition was founded were 

 incorrect. 



The glutenin probably forms the nucleus to which the gliadin adheres, 

 and thus binds the gluten proteins into a coherent elastic mass. 



Both gliadin and glutenin are necessary for the formation of gluten, for a 

 dough made with starch and gliadin, or one made with flour from which the 

 gliadin has been extracted with alcohol, yields no gluten when washed with 

 water. That the gliadin is capable of taking part in gluten formation under 

 such conditions is shown by the fact that when dry and finely ground glia- 

 din was added to wheat flour the amount of gluten obtained on subsequently 

 washing out the starch was increased by the full amount of the gliadin that 

 was added. 



THE NUTRITIVE VALUE OF THE WHEAT PROTEINS. 



It has recently been shown that in the process of digestion the protein 

 molecule is very largely broken down into amino-acids, and that the animal 

 forms from these, by the processes of assimilation, the proteins of its blood 

 and tissues. How this change is effected is not known, nor is it known 

 whether the food protein is converted into the body protein and then ox- 

 idized and eliminated, or is partly converted into body protein and partly 

 burned directly in the form of amino-acids. It is also a question whether 

 or not the animal has the power to convert one amino-acid into another, and 

 thus obtain material suitable for the construction of its own body protein. 



Directly connected with these important problems are the facts presented 

 by the determination of the relative amounts of the different amino-acids 

 yielded by the proteins of wheat flour, for these are used in enormous quan- 

 tities as food by man, and, as an examination of the analyses of their decom- 

 position products show, present marked differences from similar analyses of 

 all the other food proteins thus far examined. 



As gliadin and glutenin together form about 85 per cent of the proteins of 

 wheat flour, they deserve especial consideration in this respect. If it is 



