D. Sclater Lewis was born in Montreal and educated at McGill, where he received his B.Sc. (1907), M.Sc. (1908) and M.D.C.M. (1912). He taught briefly at Johns Hopkins Medical School, and joined the Canadian Army Medical Corps at the outbreak of World War I, rising to the rank of Major. After the war he joined the Faculty of Medicine of McGill University as Demonstrator in Medicine and Lecturer in Clinical Therapeutics. He became Assistant Professor in 1924, Associate Professor in 1939 and Professor in 1949. Throughout this period he was a physician at the Royal Victoria Hospital, and Acting Physician-in-Chief from 1943 to 1944. Lewis was President of a number of medical and medical-historical societies, and author of histories of the Royal College of Physicians and Surgeons of Canada and of the Royal Victoria Hospital.