Born at St Lucia, West Indies, the eldest son of Surgeon General D R McKinnon, RAMC; was educated at the Aberdeen Grammar School, then at Marischal College, where he distinguished himself, and after graduation in 1882 was successively House Surgeon and House Physician at the Royal Infirmary. He went on to Vienna for a year, then in 1885 was appointed to the River Ambulance Service of the Metropolitan Asylums Board as Assistant Medical Officer during an epidemic of small-pox. Next he became Assistant Medical Officer at the Bethnal House Lunatic Asylum for three years, during which he attended the patients of the London Hospital, and acted as Clinical Assistant at the Royal Ophthalmic Hospital, Moorfields. In March, 1889, he proceeded to Belize, British Honduras, to join a practice. He devoted himself to the care of patients whilst yellow fever was rife, and to a study of the infection. On September 26th he himself developed symptoms, styled euphemistically 'bilious remittent fever', upon which, after a week, pneumonia supervened, and he died on October 4th. He had made many close friends both in Scotland and in London.