170 VITAMIN D GROUP 



trace forms of vitamin D. The vitamin D of tuna liver oil was so unstable 

 that good curves could not be obtained. White sea bass liver oil gave an 

 unusually pure curve, indicative of a preponderance of one form of vitamin 

 D. Spearfish liver oil gave a fairly good curve, with a somewhat higher 

 elimination maximum, suggesting a vitamin D of higher molecular weight. 

 Albacore liver oil had chiefly one form of vitamin D, with lesser amounts of 

 higher and lower boiling forms. The most volatile vitamin D of cod liver 

 oil was one of the minor forms, and this, when assayed^^^ with rats 

 and chicks, exhibited an efficacy ratio of between 25 % and 50 %. 



In two instances the vitamin D of fish oils has been isolated. The vitamin 

 D from halibut liver oiP^^ was identified as vitamin D3, and that from tuna 

 liver oiP^^ was vitamin D3 with an admixture of vitamin D2. It is therefore 

 established, by efficacy ratio studies, by molecular distillation, and by 

 actual isolation, that more than one kind of vitamin D occurs in fish oils, and 

 it seems probable that several kinds may be present. Whether or not the 

 oil of any given species always contains the same kind or mixture is not 

 known, but it would be reasonable to assume that some qualitative varia- 

 tion, as well as quantitative, occurs as a result of differences in food and 

 other environmental factors. 



Little but conjecture can be written about the origin of vitamin D in 

 fish oils. Steenbock and Black, ^ in one of their early papers on the activation 

 of foods, emphasized the suggestion that vitamin D is formed by the inso- 

 lation of plankton, which is ingested by little fish, and these in turn by 

 larger fish, and so on. So far as green phytoplankton is concerned, this 

 hypothesis has received no experimental support, but the discovery of vi- 

 tamin D in the brown alga, Sargassum, renews interest in it.^^^ Furthermore, 

 since ergosterol is a vegetable sterol, it seems more likely than not that 

 the activated ergosterol (vitamin D2) found in tuna liver oil originated in 

 the vegetable kindgom, although it could be that the ergosterol was ab- 

 sorbed as such and activated in a mollusk or fish. On the other hand, the 

 activated 7-dehydrocholesterol (vitamin D3) which was the only form of 

 vitamin D identified in halibut liver oil and the predominant one in tuna 

 liver oil, almost certainly originated in an animal, because cholesterol is 

 never found in the vegetable kindgom. 



Marine animal life other than fish does not exhibit much ^atamin D. 

 Drummond and Gunther"^ found a small amount in zooplankton oil. Belloc 

 et al}^^ found that zooplankton collected in the spring contained provita- 



'83 C. E. Bills, O. N. Massengale, K. C. D. Hickman, and E. L. Gray, J. Biol. Chem. 



126, 241 (1938) . 

 184 H. Brockmann, Hopp^-Seyler's Z. physiol. Chem. 245, 96 (1937). 

 186 H. Brockmann and A. Busse, Naturwissenschaften, 26, 122 (1938) ; Hoppe-Seyler's 



Z. physiol. Chem. 256, 252 (1938). 

 —y 186 G. Belloc, R. Fabre, and H. Simonnet, Compt. rend. 191, 160 (1930). 



