James MacDonald Troup, medical practitioner, was educated at the Madras Academy in Cupar, Scotland. Subsequently he studied mathematics at the University of Cambridge and was awarded the degree Bachelor of Arts (BA). He then switched to medicine and qualified as a licentiate of the Society of Apothecaries of London (LSA) in 1895, and in 1896 as Bachelor of Medicine (MB) and Bachelor in Surgery (ChB) at the University of Cambridge and King's College Hospital. Soon after qualifying he came to the Cape Colony, where he was licensed to practice on 13 March 1897.
Based on his background in mathematics and natural science Troup was appointed by the University of the Cape of Good Hope (which was an examining body only) as an examiner in mathematics (1901-1903) and in statics, hydrodynamics and optics (1903). Around this time he was awarded the degree Master of Arts (MA) by the University of St Andrews, Scotland. Several years later he and G.D. Maynard* published a paper on 'Modern statistical methods' in The Lancet (1910). Meanwhile Troup had moved to Pretoria at the conclusion of the Anglo-Boer War (1899-1902) and was registered to practice in the Transvaal in 1902. He remained in Pretoria for the rest of his life, as medical practitioner, district surgeon of Pretoria, honorary physician (later honorary consulting physician) to the Pretoria Hospital, and member of the Pretoria Suburbs Health Committee.
Troup was a tall, lean, reserved and soft-spoken man and an outstanding physician. From 1920 he became a friend of the pathologist Adrianus Pijper*, whom he often consulted in the course of his work. Pijper described him as an excellent and thorough diagnostician who treated his patients with care and good timing, had extensive experience to fall back on and an outstanding memory. His most remarkable achievement was his recognition, based on years of clinical observation, of tick-bite fever as a new disease. He and Pijper were the first to investigate the disease properly and published their findings in 'Tick-bite fever in South Africa' (The Lancet, 1931). They established that the disease was clinically typhus like and transmitted by a larval tick bite, and demonstrated its infectivity in guinea pigs.
Troup became a member of the South African Association for the Advancement of Science in 1906 and was still a member in 1918. In 1902 he married Ethel MacDonald, who died in 1908. In 1910 he married Alberta Beatrice Caroline Davis, with whom he had three daughters. After his death one of his daughters, Freda Troup, edited a memorial volume entitled Physician and friend: James MacDonald Troup (1947), a biography consisting mainly of the letters he wrote.