John Ledingham was born at Boyndie, Banffshire, the son of Rev. James Ledingham, and went to school at Banff Academy. His higher education took place at Aberdeen University, where he graduated as M.A. (1895), B.Sc. (1900) and M.B, Ch.B. (1902), and won the Simpson and Arnott prizes, the Carnegie research fellowship and the Anderson scholarship. He completed his training with a visit to Leipzig and with bacteriological research at Aberdeen and the London Hospital. In 1905 he was appointed assistant bacteriologist in the serum department of the Lister Institute at Elstree and a year later transferred to the main Institute in Chelsea. He succeeded George Dean as chief bacteriologist in 1909 and was given the title of professor of bacteriology by London University in 1920. His work at the Institute, meanwhile, had been interrupted by his war service in the R.A.M.C, first as bacteriologist at the King George Hospital, and then as a member of the Medical Advisory Committee in the Mediterranean and consulting bacteriologist to the Forces in Mesopotamia, with the rank of lieutenant-colonel. He was created C.M.G. in 1918.
On Sir Charles Martin’s retirement in 1931, Ledingham became director of the Lister Institute, while retaining his post as chief bacteriologist. Three years later he began a four-year term as a member of the Medical Research Council, on whose behalf he had helped to edit the encyclopaedic System of Bacteriology (1929-31). His own researches embraced a wide variety of subjects — kala-azar, phagocytosis, typhoid carriers — an early work by him and Arkwright to attract attention was The Carrier Problem in Infectious Diseases (1912) — virus diseases, diphtheria immunisation, and the safeguarding of milk supplies. He delivered the Harben lectures in London in 1924 and the Herter lectures at Baltimore in 1934. He was knighted in 1937. Although shy in manner, laconic in speech and sparing with praise, he encouraged his staff by his example and proved an able administrator. Ledingham derived his main interests outside his work from his love of the country. He married in 1913 Barbara, daughter of David Fowler of Broomie-knowe, Midlothian, and had a son and a daughter. He died in London.
G H Brown
[Lancet, 1944; B.M.J., 1944]