The chemistry of irradiated ergosterol

At the invitation of the Secretary of the Royal Society, I present to you an account of my work on the chemistry of irradiated ergosterol. Since it became known that ergosterol, on irradiation with ultra-violet rays, is converted into an antirachitic substance of high activity, presumably identical with the vitamin D of cod-liver oil, the study of t he most favourable conditions for the course of this photochemical process has continued, together with attempts to prepare the active substance in pure crystalline condition, and to obtain knowledge of its physical and chemical properties.