 He assisted Simpson in his experiments in anaesthetics, and on 4 November 1847 experimentally inhaled chloroform to the point of insensibility.At the end of 1849, after some months of travel in attendance on the Marquess of Bute, Duncan began practice in Edinburgh, mainly as an obstetrician.He became a fellow of the Edinburgh College of Physicians in 1851, and in May 1853 began a course as an extra-academical lecturer on midwifery.