NUTRITION. 329 



Having learned much concerning the relative value of many indi- 

 \idual proteins obtained from various seeds, the next subject for 

 investigation should be the nutritive value of the total proteins as they 

 naturally occur together in the seed. A beginning has already been 

 made along these lines, using certain seeds rich in oil, e. g., the cotton 

 seed ; for after removing the oil the residues contain enough protein for 

 use under the conditions of our methods of experimental feeding. 



Heretofore seeds rich in starch, e. g., the cereals, could not be studied 

 in this way, although some information of value has been obtained by 

 feeding protein concentrates produced commercially. We are now en- 

 gaged in developing methods for removing starch with the least possible 

 loss of protein and have every reason to expect results which will mate- 

 rially increase our knowledge of the food value of such seeds. We also 

 believe we shall be able to secure from several important seeds prepara- 

 tions of some of their proteins which will be better than those heretofore 

 obtained only in small quantities and in a state of doubtful purity. 



In the past it has been the custom of those concerned with problems 

 of nutrition to assume that all of the nitrogen present in seeds which 

 can not be extracted by the solvents usually employed belongs to pro- 

 teins. While this assumption may be correct, it is supported by such 

 very unsatisfactory evidence that efforts should be made to determine 

 as definitely as possible the nature of this insoluble nitrogen. The 

 work which we now have under way, involving the removal of starch, 

 ought to give us an opportunity to investigate this problem more thor- 

 oughly than heretofore, and attention is now being directed to this end. 



The pmpose of these experiments is to bring the results of our 

 past work into closer relation to the problems presented by the prac- 

 tical feeding of domestic animals, for we believe that when we know as 

 accurately as possible the actual nutritional requirements essential 

 for normal growth and continued maintenance, and how these can be 

 supplied by the use of such foodstuffs as are available, improvements 

 and economies can be introduced into practice. Our investigations of 

 the past years have shown us how to prepare the individual proteins 

 contained in many of the more important food products, what the 

 characteristics of their chemical constitution are, and how far each of 

 these proteins meets the needs of growing or adult animals. We have 

 learned that many of these proteins are inadequate as the sole source of 

 protein and have shown that this is in most cases due to a deficiency 

 in one or more amino-acids. We have shown that these deficiencies 

 can be overcome by adding the lacking amino-acids themselves or 

 by combining two proteins which supplement each other in respect to 

 chemical structure. We have obtained some data concerning the 

 relative nutritive value of a few seeds when fed as a whole, but still 

 require further knowledge regarding many others, especially the cereal 

 grains. It is our hope that investigations along the lines just indicated 

 will supply much of the information which is still needed. 



