Enlightenment London surgeon. Examining his personal, professional, and genteel achievements enhances our understanding of the boundary between surgeons and physicians in Enlightenment 'marketplace' practice. Turner's pioneering writing on skin disease, De Morbis Cutaneis, emphasizes the skin's role as a physical and professional boundary between university-educated physicians who treated internal disease and apprentice-trained surgeons relegated to the care of external disorders. Turner also argued that a pregnant woman's imagination could be transferred to her unborn child, imprinting its skin with various marks and deformities. This stance sparked a major pamphlet war between Turner and London physician James Blondel, raising this phenomenon from a folk belief to a chief concern of Enlightenment natural philosophy. Turner's career-long crusade against quackery and his voluminous writings on syphilis, a common 'surgical' disorder, provide a refined view into distinctions between orthodox and quack practices in 18th-Century London. Turner, long viewed as a pioneer in British dermatology, also holds the Anglo-American distinction of receiving a medical degree from Yale, the first such degree offered from Colonial America