OrOTTRRENrE OF VITAMINS D 773 



the different tjTJes of vitamins D.^'* Moreover, Russian workers'^'^ have 

 reported that seal oil is a more effective antirachitic agent for man than it is 

 for rats. Vitamin D3 is reputedly somewhat more effective in man than is 



1. Occurrence of the Vitamins D 



Vitamin D is distributed in nature only to a limited extent. It is prac- 

 tically absent from the plant kingdom, although significant amounts of 

 provitamins D occur in vegetables. Vitamin D has been observed-'^--'" to 

 occur in vegetables. The presence of vitamin D has been noted^^'^'^'^ in 

 mushrooms growing in open woods, for instance, in the morel or May mush- 

 room {Morchella esculenta), the edible boletus {Boletus edulis, B. badius), 

 chanterelle {Cantharellus cibarius), and the edible turban-top {Helvella 

 mitra (esculenta)). It occurs in insignificant amounts in the edible meadow 

 (button) mushroom {Agaricus (Psalliota) campestris) grown commerciallj^ 

 in dark cellars, -^^ but was also found in slightly larger amounts in those 

 growing in open meadows. ^^^ These provitamins may, in exceptional cases, 

 be transformed into vitamin D in the plant, as has been reported for cacao 

 shells (Theobroma cacao)^^^ and for hay.^^^ 



On the other hand, vitamin D is widely distributed in the animal king- 

 dom, but the species which contain significant amounts of this substance 

 are relatively few.^^" The largest concentrations of the vitamins D are to 

 be found in the fishes, where they are chiefly present in the liver and in some 

 cases in the viscera. The amount of vitamin D present varies markedly in 

 different species. Thus, the liver oil of the blue-fin tuna (Thunnus thyn- 

 nus) contains as much as 40,000 I.U. per gram, while the liver oil of the 

 European sturgeon (Acipenser sturio) is devoid of this vitamin. ]\Ior- 

 ton^^^ has indicated that the vitamin D content of fish liver oils may reach 

 200,000 I.U. per gram in exceptional cases. The comparative values in 

 various fish liver oils are summarized in Table 4. 



The vitamin D content of fish oils varies with the season and with such 

 biological factors as age, food supply, climate, sex, and nutritional condi- 

 tion. ^-^ In the case of the halibut, there is a large amount of oil in the liver 



21^ T. H. .Jukes and T. D. Sanford, /. Nutrition, 18, 71-85 (1939). 



-'^ E. J. Michlina, M. J. Leiserovskaia, and X. X. Milanova, Kazan. Med. Chim. Zhur., 

 S3, 64-67 (1937); Chem. Zentr., 169, II, 3108 (1938); Chem. Abstr., 34, 5896 (1940). 



216 A. Scheunert and J. Reschke, Deut. med. Wochschr., 57, 349-351 (1931). 



2'- A. Scheunert, IM. Schieblich, and J. Reschke, Z. physiol. Chem., 235, 91-96 (1935). 



218 W. A. Knapp and K. H. Coward, Analyst, 59, 474^78 (1934). 



21s H. Steenbock, E. B. Hart, C. A. Elvehjem, and S. W. F. Kletzien, /. Biol. Chem., 

 66, 425-440 (1925). 



220 P. A. Coppen.s and G. A. Metz, Arch, neerland. Physiol, 18, 407^15 (1933). 



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



222 E. Poulsson and F. Ender, Skand. Arch. Physiol, 66, 92-96 (1933). 



