William Alexander Hammond, M. D. (1828 1900), one of the most successful American physicians of the nineteenth century, was first recognized in the 1850s as a natural history collector and as an original investigator in physiological chemistry. Appointed surgeon general of the United States Army in 1862, he supervised a sweeping reorganization of the Medical Department along lines of centralization and efficiency. Some of his more controversial projects, however, provided Hammond's political enemies with the opportunity to engineer his court-martial and dismissal from the army in 1864. He then established himself in New York as an exclusive specialist in neurology, one of the first in the country. In this first full-length biography of a major nineteenth-century American medical personality, Bonnie Ellen Blustein shows how Hammond developed his specialty practice as a vehicle for pursuing broad scientific interests within the limits set by the solo-practitioner structure of the medicine of his day.