INTRODUCTION 643 



found. ^"^ One source of vitamin D in sea plants is the gulfweed (Sar- 

 gassum, spp.), a floating brown alga produced in enormous quantities in 

 the area near the Tortugas Islands. ^^^ Large masses of these plants break 

 away, and are carried in the Gulf stream to as far north as Iceland. The 

 alga becomes a major food for fish, especially after it becomes infested with 

 moUusks, shrimps, and other invertebrates. According to Darby and 

 Clarke,'^'* the sea-weed freed of extraneous matter contained about 3% of 

 oil on the dry basis, and thus was found to have an antirachitic potency 

 comparable to that of some of the poorer fish liver oils. It is uncertain to 

 what degree Sargassum may act as a contributor to the vitamin D in fish 

 liver oils. Copping'^^ reported that copepods contain some vitamin D. 



(a) Vitamins D in Fish Oils. The highest concentrations of vitamin D 

 found in nature are those present in fish oils; in most cases the vitamin D 

 is almost entirely concentrated in the Hver although, in some cases, rela- 

 tively large amounts may be concentrated in the viscera, and moderate 

 amounts are found in fish roe.'" Vitamin D occurs in most fish oils, but 

 there are marked differences in the quantities present, not only in different 

 species, but also in the case of different members of the same species. 

 Bills,'- in his most recent compilation of the vitamin D content of various 

 fish liver oils, recorded a maximum average value of 45,000 I.U./g. in the 

 liver oil of the oriental tuna {Thunnus orientalis) while European sturgeon 

 liver {Acipenser sturio) is practically devoid of this vitamin, bioassays 

 showing biopotencies of less than one unit/g. hver oil. Morton^^^ stated in 

 1942 that the vitamin D content of fish liver oils may reach 200,000 I.U./g. 

 in exceptional cases. The vitamin D in fish oils has been found to occur 

 hoih. in free and in esterified forms. ^^"^-^^^ Table 4 records the values for the 

 vitamin D content of one-hundred species of fishes as given by Bills,' on the 

 basis of earlier findings of Bills et al. ^^^ 



Although vitamin D is largely concentrated in the liver, Bills'^' first 



1" H. H. Darby and H. T. Clarke, Science, 85, 318-319 (1927). 



i«« A. M. Copping, Biochem. ./., 28, 1516-1520 (1934). 



'«« R. A. Morton, Ann. Rev. Biochem., 11, 365-390 (1942). 



1" K. C. D. Hickman, Ind. Eng. Chem., 29, 1107-1111 (1937). 

 . >«8 K. C. D. Hickman and E. L. Gray, Ind. Eng. Chem., 30, 796-802 (1938). 



1^9 C. E. Bills, F. G. McDonald, O. N. Massengale, M. Imboden, H. Hall, W. D. Her- 

 gert, and J. C. Wallenmeyer, J. Biol. Chem., 109, yii (1935). 



1™ D. S. Jordan, B. W. Evermann, and H. W. Clark, Check List of Fishes and Fishlike 

 Vertebrates of North and Middle America North of the Northern Boundary of Venezuela and 

 Columbia. Report of the U. S. Commissioner of Fisheries for the Fiscal Year 1928, with 

 Appendices, Part 2, Govt. Printing Office, Washington, 1930. 



1" C. E. Bills, Studies on the Antirachitic Vitamin, Dissertation, Johns Hopkins Press, 

 Baltimore, 1924; cited by W. H. Sebrell, Jr., and R. S. Harris, The Vitamins, Vol II. 

 1954, p. 164. 



