AN animal can either obtain the necessary supply of vitamin D for skeletal growth from its food or it can make it for itself from some precursor, if its surface is sufficiently exposed to sunlight or ultra-violet rays.The principle which is activated to form vitamin D has hitherto been found associated with cholesterol, but from observations of Rosenheim and Webster [1926; 1927, 1, 2] and Heilbron, Kamm and Morton [1927] the precursor of vitamin D is not ordinary cholesterol, although it clings to it during successive recrystallisations. Rosenheim and Webster [1927, 2] adduce good reasons for supposing that it is ergosterol. They find that ergosterol is 2000 times as rich in the provitamin as brain cholesterol. Ergosterol unlike ordinary cholesterol has three double bonds and has three absorption bands in the ultra-violet, the strongest being at a wave length of 280 ,u,u, accompanied by two others of less intensity, at wave lengths of about 270 ,up and 295 p,pu.
of dl-rx-tocopheryl acetate as a possible international standard for vitamin E. It has in the interval been decided that it would be more accurate to use the name synthetic racemic tocopheryl acetate, and this will be done in future. A supply of the substance sufficient for extensive biological and stability tests, and to provide a standard should the substance ultimately be adopted, was very kindly provided by Messrs. Hoffmann-La Roche of Bas le, through the British associated company, Messrs. Roche Products, Ltd., Welwyn Garden City. Workers in Europe and the United States experienced in vitamin E tests were invited to participate, and solutions were prepared by Dr. P.
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