NUTRITION — OSBORNE. 217 



products. As only the purest attainable preparations were suitable for this 

 work, a large amount of time and labor was required for making them. 



Over 80 per cent of the proteins of the wheat kernel consists of gliadin 

 and glutenin, which, in most varieties of wheat, are present in about equal 

 proportions. Several kilograms of each of these proteins were made and 

 used in the work described in Part III. The remainder of the proteins of 

 this seed are leucosin, a globulin, and a mixture of several proteoses. The 

 combined quantity of all these proteins is only about i per cent of the seed, 

 and consequently the preparation of large quantities of them would be 

 impossible if it were not for the fact that they are constituents of the 

 embryo and can be obtained from the commercial germ meal of the flour 

 mills. A sufficient quantity of leucosin was prepared from this source to 

 enable us to make a nearly complete analysis. Attempts to prepare the 

 globulin from the germ meal failed, as we were not able to separate it from 

 the nucleic acid, which is present in the wheat embryo in relatively large 

 proportion. No attempt was made to prepare the proteoses, as there is no 

 available method by which products of definite character could be obtained. 

 The amount of these proteoses is too small to make their analysis important. 



The results described in Part III are summarized as follows : 



The extensive use of wheat flour makes it of great importance to know 

 as much as possible regarding its chemistry and especially regarding the 

 chemistry of its protein constituents. This is of importance not only in 

 relation to problems of vegetable chemistry and physiology, as well as to 

 problems of protein chemistry, but especially so in connection with the 

 nutrition of man. In connection with the latter question, it has become of 

 fundamental importance to know the nature and proportion of the products 

 which the food proteins yield when decomposed by boiling acids, for the 

 recent progress in our knowledge of digestion has shown that the digestive 

 enzymes convert the food protein very largely into the same substances as 

 those produced by boiling acids. These final products of hydrolysis are 

 consequently the units with which the process of assimilation chiefly deals. 



Furthermore, as the wheat kernel is the only seed from which practically 

 all of the protein constituents have been isolated and of which we have the 

 most definite knowledge both in respect to their kind and proportion, it is 

 especially desirable to supplement our present knowledge by as full informa- 

 tion as possible concerning the primary decomposition products of these 

 proteins in order that something in regard to their structural relations may be 

 known and the kind and amount of the possible products of the metabolism 

 of this seed may be ascertained. 



The investigation of this problem has accordingly been undertaken, the 

 results of which are given in the following pages. 



As stated in Part II of this series of papers, ghadin, glutenin, and leucosin 

 were the only proteins of the wheat kernel which could be obtained in 



