THE VITAMINES IN THE ANIMAL KINGDOM 125 



by the addition of vitamines A and B, tomato juice, small quantities 

 of milk, and by the substitution of casein for meat. Although some 

 of these modifications were effective for a short time, the growth 

 curve was nevertheless flat. That the animals were still able to 

 grow, was demonstrated by placing them on the usual normal diet. 

 Hopkins (341a) recently also reported that rats failed to grow on ade- 

 quate food mixtures, and he ascribes this to the seasonal variation 

 of the growth impulse. Osborne and Mendel (I.e. 336) also showed 

 that it is not so easy to raise rats with an addition of yeast as with 

 the addition of protein-free milk; it was particularly noticeable that 

 there was a difference in the ability of the rats to raise their young. 

 Sugiura and Benedict (I.e. 108) obtained similar results, as did also 

 Freise (342), who ascribed a particular r61e to milk. 



In collaboration with Dubin we (342a) have recently demonstrated 

 that what has up to now been known as vitamine B does not appear 

 to be sufficient for the growth of rats. Thus, it seems that autolyzed 

 yeast contains besides vitamine B something else of a vitamine nature 

 without which the rat does not grow. This will be discussed more in 

 detail in the chapter on the "Chemistry of Vitamine B." Judging 

 from the data recorded here, it appears desirable to study the nutri- 

 tive requirements of rats still further. 



Mice 



As we have already seen, the pioneer work of Stepp, Rohmann, 

 Lunin, Socin and others on artificial feeding was done with mice. 

 Getting away from the older work, which has more of a historical 

 interest, and coming to the modern investigations, we see in the work 

 of Brailsford Robertson (343), statistical data in relation to growth 

 of mice, which could be useful in judging the effect of experimental 

 diets. Thompson and Mendel (344) studied the food requirements 

 necessary for the growth and maintenance of the mouse, the suppres- 

 sion of growth, shown by undernourishment, and the amount of food 

 necessary to overcome this suppression. Mendel and Judson (345) 

 working with mice analyzed the total dry substance, fat and ash of 

 various dietary constituents. M. B. Schmidt (346) made the inter- 

 esting observation that if a deficient diet has no effect on the first 

 generation in these animals ; its results are apparent in subsequent 

 generations. Morpurgo and Satta (347) worked with mice in 

 parabiosis in which one animal received only cane sugar while the 



