44 THE VITAMINES 



In a great number of experiments, Osborne and Mendel (103) 

 showed that the nutritive value of lactalbumin is much greater than 

 that of casein, and they attributed it to the nature of the particularly 

 favorable amino acid composition of this protein. 4 Edelstein and 

 Langstein (104) recently arrived at the conclusion that the superiority 

 of mother's milk over cow's milk for the child is due to the greater 

 content of lactalbumin in mother's milk. 



In a series of papers, which are not altogether clear in their mean- 

 ing, Emmett and Luros (105) sought to show that while lactalbumin 

 of itself was a complete protein for growth, the specially favorable 

 results obtained must be attributed to the influence of the protein- 

 free milk added at the same time. In this, they coincide with 

 the view of McCollum, Simmonds and Parsons (106). In other 

 words, the favorable influence of lactalbumin on the growth of rats 

 was to be attributed to the presence of a vitamine in the protein-free 

 milk or the lactose. This vitamine was supposed to be different 

 from vitamines B and A. 



Emmett and McKim (107) have also assumed the existence of 

 two vitamines in yeast one that cures beriberi and one that pro- 

 motes growth in animals. They reached these conclusions from 

 adsorption experiments with fuller's earth. They showed that the 

 activated fuller's earth was protective against beriberi, but did not 

 influence the weight of the animal. Such experiments, unless well 

 controlled, can have no real significance, considering the possibility 

 of incomplete adsorption, the relative amounts used and other 

 factors. 



Sugiura and Benedict (108) point out that certain diets with the 

 addition of yeast serve to increase the growth of young rats, although 

 the mothers appear to be lacking in milk. They conclude therefore 

 that for this purpose a special vitamine is desirable. As an illustra- 

 tion of this, the example is given that an addition of casein exerts a 

 much greater influence than a simple addition of extra protein. In 

 one particular case it was shown that purified casein could not be 

 replaced by purified meat. In a second experiment, they diminished 

 the amount of the added yeast to 0.5 per cent of the total diet and it 

 therefore appeared not impossible that the failure of milk production 



4 Later, these investigators showed that this is true only when protein-free 

 milk is used as source of vitamine B. This addition seemed to have the effect 

 of completing the value of that particular protein. 



