222 THE VITAMINES 



insoluble portion, the ether solution, after washing with water, was 

 shown to be active. From this residue, the carrotin was separated 

 from xanthophyll by extraction with petroleum ether, showing the 

 carrotin fraction to be active and the xanthophyll fraction, inactive. 



THE NATURE OF VITAMINE A 



Drummond (I.e. 582) in one of his papers proposed the conception 

 that vitamine A was of the nature of a ferment and was a more or 

 less unobtainable body. He carried out experiments with various 

 known substances and found that fatty acids, glycerol, cholesterol, 

 lecithin, sphingosine, phrenosine, kephalin, lipochrome and carrotin 

 could not simulate the action of vitamine A. Steenbock (587) made 

 the interesting observation that the vitamine A content of maize 

 goes parallel with the content of yellow pigment; white maize was 

 found free from this vitamine, and the same was also true of most 

 kinds of vegetables. According to Steenbock and Boutwell (588) 

 when white corn is supplemented by butter, clover or spinach, the 

 rat resumes growth. Palmer (589), on the contrary, was opposed 

 to this finding. In the first place, he showed that chickens could 

 live on a diet free from carrotinoids, at least through one generation, 

 although it is of course quite possible that chickens may live without 

 vitamine A, or at best with very little. Second, it was possible for 

 him to raise mammals (rats; Palmer and Kennedy, 589a), the blood 

 and subcutaneous tissue of which were pigment free. Despite the 

 fact that the milk of these animals was practically pigment-free, 

 it was possible for them to suckle and rear their young. Palmer 

 observed also that there are oils, such as cottonseed oil, which, 

 although containing pigment, show a lack of vitamine A. Rosen- 

 heim and Drummond (590) took up this question and in general 

 were able to confirm the fact that, as a rule, foodstuffs containing 

 lipochrome also contain vitamine A. Still, it was found that a 

 pure carrotin solution is free from this vitamine, and the authors 

 believed that although the latter must be different from carrotin 

 and xanthophyll, it is nevertheless associated with these pigments. 

 As to what action chemically pure carrotin has on rats, opinions 

 differ. While Stephenson (590a) finds that pure carrotin (m.p. 

 172-173C.) is entirely inactive and while butter decolorized with 

 charcoal and free from pigment is still active, Steenbock, Sell, 

 Nelson and Buell (590b) have obtained normal growth with pure 



