Studied at St Bartholomew's Hospital, and after qualifying was for forty years Resident Medical Officer to the Small-pox and Vaccination Hospital, Holloway, London, N, and was a Principal Vaccinator of the National Vaccine Establishment. From the time of the institution of educational vaccinating stations, he was in charge of that in Blackfriars Road. He became one of the highest authorities in this country on the subject of vaccination and small-pox, complicated by the prevalence of septic infection and of syphilis in the practice of the arm-to-arm method in cities, a complication which Jenner had escaped by practising in the country. He was a man of retiring habits, little known beyond his immediate circle, and was one of the oldest members of the Epidemiological Society, who several times refused the Presidency for reasons of health. Attacked by a painful malady whilst living in retirement at Liverpool Terrace, Worthing, he succumbed to it on November 15th, 1877. Publications: Marlon published many articles of importance at the time on vaccination and small-pox.