Beaumont, Connecticut-born and the son of a farmer, worked briefly as a school teacher, then studied medicine at St. Albans, Vermont. He received a license to practice medicine in time to serve as an assistant army surgeon during the War of 1812. Although he left the army in 1815 to start a medical practice in Plattsburgh, New York, he returned in 1820 and remained an Army surgeon, serving at various posts, until 1839.

It was at one of those army posts, Fort Mackinac in northern Michigan, that Beaumont met the patient that was to make both of them famous. The patient was a 19-year-old French Canadian trapper, Alexis St. Martin, who was accidentally shot on June 6, 1822, while visiting the Mackinac branch of the American Fur Company. The bullet wound tore a deep chunk out of the left side of St. Martin's lower chest; and, although Beaumont was sent for immediately, everyone assumed...