Born 3 July 1877 at Holywood, Co Down, Ireland, eldest of the three children and only son of David Johnston, MD, who was in general practice there, and of his wife Clara Agnes Dalton. He was educated at Upper Sullivan School, Holywood, and at Queen's College, Belfast, then a constituent of the Royal University of Ireland where he won scholarships. After qualifying in 1903 he was appointed demonstrator of physiology at Trinity College, Dublin, under Professor W H Thompson, whose daughter he married many years later (see below). From 1904 till 1910 he was chief demonstrator of anatomy to Professor A F Dixon, and some of his beautiful plaster models of the carpal bones were retained permanently at Trinity. Johnston decided to practice surgery although a brilliant career as an academic anatomist was open to him. He consequently moved to London in 1910, worked at the London Hospital, and served as clinical assistant at St Bartholomew's and at Great Ormond Street. He took the Fellowship in 1911 and served as resident medical officer at the Royal National Orthopaedic Hospital. He now developed his interest in radiology, and combining this with his excellent craftsmanship equipped himself very thoroughly for orthopaedic work. He always fashioned his own absorbable ox-bone screws, plates, and bolts for bone-surgery, and was an early advocate of plaster jackets. He was also much interested in the surgery of the jaws, and especially in reparative surgery of the face. He settled at Newcastle-on-Tyne in 1912 on appointment as resident medical officer at the Royal Victoria Hospital, and did very good work there in the early years of the war with a half-trained staff of students, when the more senior men were called to active service. He was commissioned in the RAMC, in 1917 and served at the Queen's Hospital, Sidcup, where he became adept in plastic surgery of the face. He went back to Newcastle in 1920, was appointed assistant surgeon at the Infirmary under Sir Joseph William Leech, FRCSEd, and became surgeon in 1927 and consulting surgeon in 1937. He was also surgeon to the Children's Sanatorium at Stannington, Morpeth. Johnston was a lucid and stimulating teacher, with a ready Irish wit and a fund of bonhomie. He was beloved as "Pa J" by generations of students, who delighted in his originality and carelessness for convention. After retirement he took much interest in compensation for injury and other medico-legal problems. Johnston married in 1928 Muriel, elder daughter of Sir Henry Thompson, his former chief at TCD. She survived him with their two sons. They lived at 36 Jesmond Road, Newcastle, where he was a keen gardener. He died on 22 June 1951, aged 74. Publications: Epilunar and hypolunar ossicles, division of the scaphoid and other abnormalities in the carpal region. *J Anat* 1907, 41, 59. Varying positions of carpal bones in the different movements of the wrist-joint. *J Anat* 1907, 41, 109 and 280. Anatomy of the mandible in relation to injury and disease. *Brit dent J* 1922, 43, 889. Non-malignant tumours of the jaw, diagnosis and treatment. *Brit dent J* 1924, 45, 1437.