42 McCOLLUM— RELATION OF DIET TO PELLAGRA. 



designated " fat-soluble A " and " water-soluble B." The lack of 

 the former leads to the development of a specific eye trouble which 

 seems to be accurately described as a type of xerophthalmia. The 

 factor water-soluble B is we believe identical wtih the substance 

 which prevents or cures the disease beri-beri characterized by gen- 

 eral paralysis which is common in the Orient. 



Our experimental studies have now progressed so far as to 

 enable us to assert with confidence that a satisfactory diet cannot be 

 secured from mixtures containing any number of seeds or products 

 derived from the milling of seeds together with tubers, edible roots, 

 and meats. The vegetable foods which may be classed as seeds, 

 tubers, and roots are all functionally storage organs, and their 

 content of active protoplasm is relatively small in comparison with 

 their bulk because of the large amount of reserve food material 

 laid down in them. They may be sharply contrasted with the leaf 

 of the plant, which except in special cases is not a repository for 

 reserve proteins, carbohydrates, and fats, but represents, aside from 

 its skeletal tissues, functionally active protoplasm. The leaf has 

 very different dietary properties from those possessed by the tissues 

 which are modified as storage organs, and in many instances at 

 least represents complete foods for those types of animals whose 

 digestive tracts are so capacious as to permit them to eat a sufficient 

 amount of bulky material. We have been able to prepare fairly 

 satisfactory diets for an omnivorous animal, the rat, from these 

 two types of vegetable foods together, /. c, leaves and seeds, but 

 never from the group of vegetable foods which are functionally 

 storage organs. 



From this experience we have been led to differentiate sharply 

 between two classes of foods which are usually collectively desig- 

 nated as vegetables. Leaves are constituted so as to correct the 

 dietary deficiencies of the storage tissues, whereas the seeds, tubers, 

 and roots fail to supplement mutually each other's deficiencies with 

 respect to either the inorganic moiety or the fat-soluble A. They 

 do in some degree mutually enhance the quality of each other's pro- 

 teins, but to a lesser degree than we had supposed before the com- 

 pletion of a large amount of experimental work directed toward the 



