Born in London on 5 November 1864, second son of the Rev Stanley Leathes DD, he was educated at Winchester, New College and Guy's Hospital. Very soon after obtaining his FRCS he forsook a surgical career and devoted himself to the study of physiology and biochemistry. Between 1895 and 1897 he worked in Berne and Strasbourg, and in 1899 he was appointed lecturer in physiology at St Thomas's Hospital, working at the Lister Institute at the same time. In 1909 he was appointed to the chair of pathological chemistry at Toronto and in 1915 to that of physiology in Sheffield from which he retired in 1933. A man of outstanding intellect, he had taken a first in Greats before taking up medicine; he was a brilliant and stimulating teacher, and at the same time modest, kindly and approachable. His wife was a talented musician and they both did much to stimulate an interest in music at the University. He was the author of numerous papers in medical and scientific journals, and at the Royal College of Physicians was a Croonian lecturer in 1923, Harveian Orator in 1930, served on the Council 1930-32, and was an examiner 1932-36. He was an Honorary Fellow of New College, Oxford. He died at Montreux on 14 September 1956 at the age of 91.