Percival Thomas (1740–1804), English physician and author of Medical Ethics (1803). He was central in bringing the Western traditions of medical ethics from prayers and oaths (e.g., the Hippocratic oath) toward more detailed, modern codes of proper professional conduct. His writing on the normative aspects of medical practice was part ethics, part prudential advice, part professional etiquette, and part jurisprudence. Medical Ethics treated standards for the professional conduct of physicians relative to surgeons and apothecaries (pharmacists and general practitioners), as well as hospitals, private practice, and the law. The issues Percival addressed include privacy, truth telling, rules for professional consultation, human experimentation, public and private trust, compassion, sanity, suicide, abortion, capital punishment, and environmental nuisances. Percival had his greatest influence in England and America. At its founding in 1847, the American Medical Association used Medical Ethics to guide its own first code of medical ethics. M.J.M.