 Since 1868, when he became a lecturer on pathological anatomy in the College of Physicians and Surgeons, Delafield had been a member of the Faculty of Columbia University.In 1875, he was appointed adjunct professor of medicine under Professor Alonzo Clark, and upon the latter's retirement in 1882 was elected his successor, as professor of pathology and the practice of medicine, being made professor emeritus in 1901.For a number of years since 1874, he was attached to the staff of Bellevue Hospital, at first as a member of the house staff, later as attending physician, and finally as consulting physician.