38 THE VITAMINES 



protein-free milk for its inorganic constituents, and prepared an 

 artificial protein-free milk having the same composition; this also 

 permitted of good growth. In a later communication, these inves- 

 tigators (73) pointed out that the results were not so favorable with 

 the artificial preparation. Their animals lived from 114 to 277 days, 

 but after this they died without the post-mortem giving any plausible 

 reason for death. In one case particularly, the addition of natural 

 food was ineffective in preventing death. 



Hopkins and Neville (74) reported that they attempted to replace 

 milk by a preparation made according to Osborne and Mendel. 

 They stated that when they used purified lactose, which had been 

 prepared from milk, the animals failed to grow. McCollum and 

 Davis (75) found that rats, weighing 40 to 50 grams, could grow 

 normally for about three months on the Osborne-Mendel diet. At 

 the end of this time the animals stopped growing, but were in good 

 general health. In the light of our work on vitamines, the authors 

 came to the conclusion that the failure to grow was not due to lack 

 of salt, fat and phosphatides, but to lack of vitamines. They found 

 the necessary substances in egg-yolk and butter, especially in the 

 ether-soluble portion. Besides this, they found that rats on the 

 above diet produced very little milk, and that the young were 

 stunted. Normal growth was restored upon the addition of the 

 ether extract of eggs or butter. 



Almost simultaneously with the work of McCollum and Davis, 

 there appeared the paper of Osborne and Mendel (76) in which they 

 confirmed their earlier findings. As a result of these studies, they 

 showed that artificial milk, like the natural protein-free variety, is 

 not sufficient for growth. To obtain adequate growth, either milk 

 powder or butter had to be added. 



In later publications, McCollum, as well as Osborne and Mendel, 

 disregarded the importance of the antiberiberi vitamine for growth 

 more and more, and reiterated the existence of a specific growth 

 substance in certain fats, like butter, egg-yolk and others. Little 

 by little, the entire vitamine structure became shaky, especially after 

 Osborne and Mendel (77) had started their studies on butter. By 

 centrifugation, they separated butter into three fractions. They 

 reported that the pure butter fat, supposedly nitrogen and phosphorus 

 free, still retained its activity. In particular, they were able to cure 

 ophthalmia (keratomalacia, a disease of which we shall speak 



