Shortly after, he applied to join the London Missionary Society (LMS) and was accepted subject to missionary training. He was a student at the Charing Cross Hospital Medical School in 1838–40, with his courses covering medical practice, midwifery, and botany. During this period he also spent time on missionary training in London and in Ongar, Essex, to become a minister within the Congregational Union serving under the LMS. While training under the LMS, he and other students were taught Greek, Latin, Hebrew and theology by the Reverend Richard Cecil. Despite his impressive personality, he was a plain preacher, described by Cecil as "worthy but remote from brilliant" and would have been rejected by the LMS had the director not given him a second chance to pass the course. He qualified as a Licentiate of the Faculty (now Royal College) of Physicians and Surgeons of Glasgow on 16 November 1840, and was later made an Honorary Fellow of the Faculty, on 5 January 1857.