NUTRITION. 343 



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vitamine-bearing product are necessary for adequate nutrition. Larger 

 animals may even decline in weight on a daily dosage which suffices for 

 adequate growth for small animals. 



In view of the widespread use of eggs in the dietary of man and the popular 

 belief that these products are especially rich in vitamines, so that they are 

 frequently classed with milk in such generalizations, we have lately recorded 

 experiences which we have incidentally gained in recent years. By extraction 

 of egg yolk with water it is possible to secure a product comparatively rich in 

 vitamine B, the daily dose required for a 100-gram rat being considerably less 

 than that of the most potent dried yeast hitherto examined. The content of 

 the entire egg-yolk, however, in vitamine B is not large, a daily intake of at 

 least 1.5 grams of the fresh yolk being required when it furnishes the sole 

 source of vitamine B to a 100-gram rat. The whole egg is accordingly not 

 exceptionally rich in vitamine B when contrasted with other foods already 

 investigated. Judged by the comparative trials on rats, the average sized 

 hen's egg is equivalent in vitamine B potency to about 150 c.c. of cow's milk; 

 or a quart of milk and six or seven whole eggs of the average sort have an 

 approximately equivalent vitamine-B value. 



The problem of the origin and storage of vitamines in the animal body is one 

 which has been much debated in recent years. There is a widespread and well- 

 founded impression that these food factors are not synthesized in the animal 

 organism but are derived exclusively from plant sources. It has been debated 

 whether, when an animal is maintained for some time on a diet devoid of one 

 or another of the vitamines, its organism becomes depleted in any way with 

 respect to vitamines which may have been stored therein. In order to secure 

 some evidence regarding this, we have compared the content of vitamine B 

 in comparable quantities of liver tissue obtained from rats which have been 

 respectively fed on diets devoid of vitamine B and on a mixed diet demon- 

 strably rich therein. The outcome has been very striking ; for example, whereas 

 a dose of 200 mg. of the dried liver tissue of adequately fed rats suffices as a 

 source of vitamine B for a 100-gram rat subsisting on a diet adequate in every 

 respect except this vitamine, the same amount of hepatic tissue from animals 

 which have been deprived of vitamine B for some time is entirely inadequate. 

 Obviously, therefore, when vitamine B is furnished in insufficient abundance 

 with the diet, whatever store thereof may be in the organism becomes 

 destroyed or depleted in some way. Thus far our observations have been 

 confined to a single storage organ — the liver. It will require further extensive 

 investigations to ascertain whether and to what extent similar phenomena of 

 storage and depletion occur in other tissues of the body. The answer to such 

 inquiries may throw some light upon the possible role of vitamine B in meta- 

 bolic processes. 



We have lately repeated our earlier demonstration that rats can grow to 

 considerable size on diets consisting of nine-tenths or more of protein, pro- 

 vided they receive a suitable supply of vitamines A and B as well as of inor- 

 ganic salts. Both casein and washed meat were used as the sources of protein. 

 Similar tests have since been made with rations containing about 75 per cent 

 of protein in the diet. It seemed unlikely that rations on which young rats 

 grew from 60 to 260 grams could be extremely harmful to the organism. How- 

 ever, there is a widespread popular belief that a high-protein diet in man is a 

 renal irritant; and the production of arteriosclerosis in rabbits has been 



