The elements in Doyle's life that most influenced his Sherlock Holmes' stories were his background as a doctor and his pressing need to earn a living. Born in Scotland in 1859, Doyle entered medical school at the age of seventeen. One of his teachers was Dr. Joseph Bell, whose skill in diagnosing illness had sharpened his powers of observation and reasoning. As a result Bell could, while diagnosing a patient's illness, accurately read clues to his or her background and personality as well. Bell's unusual ability made a lasting impression on Doyle, who modeled some of Holmes' deductive powers on his teacher's example. Doyle served as a ship's surgeon in the early 1880s, traveling to Africa and the Arctic, before returning to England and finishing his degree. At that time, establishing a medical practice was difficult, and Doyle waited in vain for patients to appear.

Fortunately, Doyle...