medical degree; T.C. Angus, a physician; F.A. Askew, a chemist; Hilda Bruce, a biologist, Kate Fischmann, a biologist, J. St.L. Philpott, a physical chemist, and T.A. Webster, a biologist. Collaborative work Callow became involved with a variety of problems related to the work on vitamin D, including the claim that rickets was produced by the action of certain cereals. This was shown to be due to interference with calcium absorption (working with Hilda Bruce). He also worked closely with Alan Parkes who was working on the physiology of reproduction, and C.W. Emmens. Steroids In the 1930s Callow became interested in the structure and action of sex hormones and identifying steroids in urine. In a 1936 paper, written with Frank Young, a footnote states "The term steroids is proposed as generic name for the group of compounds comprising the sterols, bile acids, heart poisons, saponins and sex hormones." Callow claimed that this was the first use of the term "steroids". He showed that androgens were excreted in the urine in similar amounts in men, women and eunuchs, which at the time was surprising. His conclusion was that these substances were produced by the adrenal cortex as well as by the gonads. This conclusion was supported by findings made jointly with A.C. Crooke, working at the London Hospital, that patients with Cushing's syndrome, caused by a tumour of the adrenals, had very high levels of androgenic substances in the urine. War service 1940 – 1945 Despite being in a reserved occupation, he joined the Royal Air Force in 1940. He became an armaments officer and spent much of the war in the NW Frontier area of India (Waziristan, now in Pakistan) defusing unexploded bombs. He was mentioned in dispatches for activity in the relief of Datta Khel. Later in the war he worked for the Inter-Services Research Bureau, a cover name for Special Operations Executive (SOE), an organisation responsible for sabotage in enemy-occupied territory, with A.G. Ogston, under the leadership of E. Gordon Cox, applying plant and medical chemistry, and developing unusual equipment. Cortisone In 1945 he returned to the NIMR, and worked with John Cornforth on a commercially attractive way of synthesising cortisone from naturally occurring steroids. (Merck & Co had a long and complex synthesis from bile acids, the only known source of cortisone in quantity.) One possible source was sarmentogenin, found in extracts of arrow poisons (heart poisons) from