THE ANTIRACHITIC VITAMINE 223 



carrotin. They prepared vitamine A from alfalfa and found that 

 it withstood saponification with heat, oxidation with hydrogen 

 peroxide and reduction with nascent hydrogen. From the unsaponi- 

 fiable fraction, active crystalline acetylated products have been 

 prepared. Liver tissue contains, besides the two known yellow 

 pigments, another substance which gives the lipochrome reaction 

 and, in addition, the color reaction with sulphuric acid which is 

 regarded in the literature as being specific for cod liver oil. This 

 substance is not a casual impurity as it may always be demon- 

 strated in cod liver oil and in liver fats. Hijmans van den Bergh 

 and Muller (591) have described* methods which may be used for 

 the separation of the lipochromes in blood. In order to liberate 

 them, it was necessary to precipitate the serum proteins with alcohol. 

 It was assumed that other chemical substances were associated with 

 the pigments. Drummond and Coward C592) have investigated 

 the pigment and vitamine A content of a number of oils and fats, 

 and found that these two factors do not always occur together. In 

 butter, the pigment content was found to run somewhat parallel to 

 that of vitamine A, whereas certain pork fats and dog fat contain 

 no pigment, but a marked amount of vitamine. They came to the 

 conclusion that a relationship between the pigment and vitamine A 

 could not be maintained unless we assume, with Steenbock, that in 

 some cases the pigments occur in the leuco-form. As evidenced by 

 the above, the whole question still rests on an uncertain foundation 

 and can be solved only when a purification of this substance is made. 

 Properties of vitamine A. The characteristics of this vitamine are 

 as yet very little known. As for the question whether the substance 

 is soluble in water, it must remain open for the present. McCollum, 

 Simmonds and Steenbock (593) have stated that fat-free milk still 

 contains appreciable amounts of vitamine A, a finding which seems 

 to be in accord with the latest results. According to their work, the 

 vitamine may be extracted with small quantities of water from melted 

 butter by repeated extraction, the remaining butter being inactive. 

 On the other hand, Steenbock, Boutwell and Kent (594) showed that 

 both the residual butter and the watery extract were inactive. They 

 believed that heat and not oxidation is the reason for the destruction, 

 although we shall see that there is still another complication to be 

 considered. The finding of McCollum, Simmonds and Steenbock 

 (I.e. 593) that fat-free skimmed milk still contains vitamine A was 

 again confirmed by Hopkins (595). 



