John Watson, the companion and biographer of Sherlock Holmes, was hit by a Jezail bullet while serving with the British army in Afghanistan.

Curiously, though, the wound migrates.

In “A Study in Scarlet” (1887), Watson says he was struck in the shoulder, but in “The Sign of Four” (1890) the wound has moved to his leg, which Watson says aches at changes in the weather.

One would think that this might have drawn Watson’s attention, as he was a medical doctor. But evidently he lacked his friend’s perspicacity — in “The Adventure of the Noble Bachelor” (1892) he refers only to a bullet wound in “one of my limbs.”