In 1966 he became professor and chairman of the Department of Medicine at Cornell University Medical College and physician-in-chief at New York Hospital.
He remained at Cornell until 1979 when he was named senior vice-president for medical and scientific affairs of Merck, Sharpe & Dohme, International Division, from which he retired in 1988.
This protein was later shown to be of great immunological importance as a part of the human leukocyte antigen histo-compatibility system.
He has also written three scientific biographies Archibald Garrod and the Individuality of Man, (Oxford University Press, 1993), Sir Clifford Allbutt (1834-1925): Scholar and Physician (Royal College of Physicians of London, 2007, ISBN 9781860163029), and Sir Francis Fraser: A Canny Scot Shapes British Medicine.
He was elected a member of the American Philosophical Society in 1972 and served as a vice president (1988–1996), and executive officer (from 1997 until his retirement in 2002).
During the academic year 1996–97, he was named Distinguished Visiting Fellow at Christ's College where he began his research on Clifford Allbutt.