NUTRITION. 357 



When all of the ingredients of the food were thoroughly extracted 

 with absolute alcohol, rats were unable to make more than very slight 

 growth. Whether this is due solely to the removal of all traces of fat- 

 soluble vitamine, or whether the alcohol removes some other hitherto 

 unsuspected essential of a perfect dietary, is a problem which we are 

 investigating at present. 



The study of the distribution of the fat-soluble and water-soluble 

 vitamines in different vegetable products, alluded to in the report for 

 1918, has been extended beyond the preliminary stage. The vegetable 

 products thus far studied include alfalfa, clover, timothy, spinach, and 

 cabbage leaves, the bulb of the onion, the roots of carrots and turnips, 

 the leaves, stems, and root of the beet, the tuber of the potato, and the 

 fruit of the tomato. All of these have been demonstrated to contain 

 more or less of the water-soluble vitamine, and all but the onion, turnip, 

 and beet roots have been found to furnish at least some of the fat- 

 soluble vitamine. 



In order that the various foods may be so used as to insure an ade- 

 quate supply of the vitamines, it is important to know not only how 

 widely these essential food factors are distributed, but also how the 

 different natural foods compare with each other as sources of these 

 accessories. Consequently a carefully controlled series of quantitative 

 experiments designed to show the relative abundance of these vita- 

 mines in some of these various vegetable products is now in progress; 

 but these investigations have not yet been continued long enough to 

 permit drawing final conclusions. 



In the case of the potato, the water-soluble vitamine is apparently 

 distributed throughout the entire tuber, although it is more concen- 

 trated near the surface than in the center; for potatoes which were 

 pared before cooking and then dried were found to be considerably 

 less rich in this food factor than were the whole potatoes, which were 

 cooked and dried without removing the skin. 



It has been stated that the fat-soluble vitamine can not be extracted 

 from plant tissues with ether. We have found, however, that the ether 

 extract of spinach leaves or of immature alfalfa or clover plants or of 

 yoting grass is comparatively rich in this vitamine. As little as 30 

 mg. of ' 'spinach oil" per day, fed to a rat which had declined in weight 

 owing to a lack of the fat-soluble vitamine in the ration, was sufficient 

 to restore the animal to a good nutritive condition, as well as to cure 

 the eye disease which frequently occurs as the result of the lack of this 

 food constituent. 



One feature, which hitherto has received no adequate consideration, 

 is the possible dependence of the vitamine content upon the maturity 

 of the plant product. To test this point samples of mature alfalfa, 

 clover, and timothy hay were obtained from the same fields from which 

 the immature specimens were obtained earlier in the season. In every 



