THE announcement appeared in NATURE of Oct. 31, 1931, p. 758, of the preparation of ‘calciferol’, a crystalline compound of the highest known vitamin D activity, by a team of workers at the National Institute for Medical Research, under the leadership of Dr. Bourdillon. Calciferol is probably the pure vitamin, although this is not quite certain: members of this group of compounds, in mixtures of varying composition, frequently form crystals which cannot be separated into their components by simple recrystallisation but only by the formation of derivatives. Calciferol is formed from ergosterol by the action of ultra-violet rays, and up to the present no other method of conversion of ergosterol into vitamin D has been successfully used. It is now reported in the Times of Jan. 1 that C. E. Bills and F. G. McDonald, of Evansville, Indiana, U.S.A., have claimed the first chemical synthesis of this vitamin, in a paper at the recent meeting of the American Association for the Advancement of Science. They treated ergosterol with methyl alcohol, ether, and ethylacetate under low temperature, with a rigid exclusion of oxygen, and obtained the vitamin, but in less pure form than by the irradiation of ergosterol.