116 



THE VITAMINES 



added to a carefully purified food mixture, resulted in normal growth 

 of rats; at the same time the food intake increased markedly. The 

 favorable effect of these small amounts of milk is best shown in the 

 accompanying curve. Since Hopkins fed milk in the natural state, 

 its effect could be due to the cumulative influence of several unknown 

 factors which was found later to be the case. Subsequently, Funk 

 (325), and also Osborne and Mendel (326), showed that milk does 



2.5- 50 



FIG. 22. GROWTH CURVES (HOPKINS) 



Lower curve (up to eighteenth day), vitamine-free diet; then 3 cc. milk 

 daily; upper curve, the reverse. 



not exert such a great influence as Hopkins first found; however, we 

 must not forget that the vitamine content of milk and other food 

 stuffs does not represent a constant mathematical unit and can under- 

 go great variations. 



McCollum and Davis (I.e. 75), and shortly thereafter also Osborne 

 and Mendel (I.e. 76), showed that protein-free milk was not sufficient 

 for the growth of rats and that the diet needed certain fatty con- 

 stituents, found in- egg-yolk and in butter. The lack of these factors 



