INTRODUCTORY 43 



such as casein, lactalbumin, and partly also to lactose. Obviously 

 another conclusion is possible here, namely, that milk contains the 

 most suitable combination of amino acids for the animal body. It 

 was pointed out by McCollum and Davis (97) that heating of casein 

 for one hour, at one atmosphere in an autoclave, materially decreases 

 its food value; Funk and Macallum (98), attempting to confirm this 

 observation, found that the facts were somewhat in accord, but that 

 the diminished nutritive value of casein could be remedied by the 

 administration of fresh orange juice. 3 



We believed, at that time, that heating of the casein destroyed the 

 adsorbed C-vitamine, and our view was strengthened by the later 

 work of Harden and Zilva (100) and Drummond (I.e. 79). We (101) 

 had already been able to show that beriberi in pigeons could be cured 

 by the addition of the vitamine fraction of lime juice, although we 

 were not certain if this effect was not due to the presence of vita- 

 mine C. Still later, Osborne and Mendel (I.e. 92) showed that the 

 favorable influence of orange juice on the growth of rats was due to 

 the presence of vitamine B. This observation was further confirmed 

 by the work of Byfield, Daniels and Loughlin (I.e. 90), in which they 

 showed that orange juice treated with fuller's earth exerted no 

 growth-promoting influence either on young or grown rats, in spite 

 of still containing vitamine C. Till now, there has been no explana- 

 tion of why, when the diet already contains apparently sufficient 

 vitamine B, upon the addition of more of this vitamine the organism 

 should respond with an acceleration of growth. There is a possi- 

 bility here that orange juice may contain a new vitamine which, 

 together with B vitamine, is adsorbed by fuller's earth. 



Osborne, Wakeman and Ferry (102) showed that certain types 

 of proteins, for instance, edestin, manifest a greater capacity for 

 adsorbing vitamine B than do other proteins, and that the latter, by 

 means of thorough washings, could not be freed from it. It would be 

 plausible to assume that casein, as well as lactalbumin, might show a 

 selective adsorptive capacity for some new vitamine. As we shall 

 show towards the end of this book, the acceptance of a new and 

 important amino acid or of a new vitamine appears inviting for the 

 elucidation of the etiology of certain pathological conditions, and 

 also for the explanation of the difference in food value between 

 proteins of vegetable and animal origin. 



3 Hogan (99) found that heating of proteins, casein in particular, does not 

 impair their effectiveness. 



