344 THE VITAMINES 



contain substances which, after hydrolysis, cannot be isolated 

 and which thus far remain unknown among the cleavage products. 

 McCollum and Davis (I.e. 97) believed that when casein is 

 autoclaved, its nutritive value decreases markedly; but, according to 

 Funk and Macallum (I.e. 98), this deficiency may be overcome by 

 the addition of vitamine-containing products. Yet, it is not impos- 

 sible that heating may decrease the nutritive value of some proteins. 

 Mueller (I.e. 167a), in this connection, made an interesting observa- 

 tion in the culture of streptococci, namely, that peptone, casein, 

 edestin, in the tryptophane fraction, contains a substance seemingly 

 indispensable for the growth of this microorganism. Mueller was of 

 the opinion, that he was dealing with a new amino acid, in which 

 belief he was strengthened by the fact that reprecipitated casein 

 possessed the same ability. Still, this condition does not militate 

 against the possibility that the substance may be of a vitamine nature, 

 for in the first place, the active substance is so markedly adsorbable 

 that it may be completely removed with animal charcoal; second, if 

 the substance is carried down in the first precipitation of the casein, 

 it would, in all probability, be carried down on reprecipitation. By 

 reprecipitation of the casein, therefore, no separation can be obtained. 

 We saw in the case of other bacteria that the vitamine-like substances 

 there could not be filtered, even through paper, without being 

 adsorbed. Mueller found that wool, silk, gelatin and hydrolyzed 

 yeast do not contain this substance ; it was found in the tryptophane 

 fraction; but when the known substances in this fraction were 

 tested for the above action, no result was obtained. If the fraction 

 is precipitated with phosphotungstic acid, the substance disap- 

 pears from the precipitate as well as from the filtrate. If the 

 fraction is crystallized, the substance remains in the filtrate and 

 appears unstable, de Souza and McCollum (I.e. 529) observed 

 that hydrolyzed meat exerts some action on the growth of yeast. 

 Funk and Dubin (unpublished work) noted that a completely 

 extracted meat (the last extract being no longer active for yeast), 

 when hydrolyzed, shows definite action. The question whether we 

 are dealing here with a vitamine or an unknown amino acid must be 

 left open for the time being, though it seems to us not impossible 

 that the above finding will give a new stimulus to protein research, 

 in that we have a biological reaction that may be of value in a frac- 

 tionation. In addition, the nutritive value of the proteins may 

 appear to us in a new light, for the experiments show that some 



