You will be given a trivia clue, and the category it belongs to. You should answer with the best answer that belongs in the category and is described by the clue. For simplicity, answers should be in all lower cased letters.

Category: THE NATIONAL MUSEUM OF HEALTH & MEDICINE 
Clue: Among lesser-known body parts at the museum, see the leg Gen. Daniel Sickles lost at this July 1863 battle
gettysburg

Category: PEN NAMES 
Clue: He contributed to the Columbia Review under the name Jean-Louis Incogniteau, perhaps while he was "On the Road"
jack kerouac

Category: THE ELEMENTS 
Clue: In 1827 Friedrich Wohler produced this metal, the Earth's most common, as a powder

aluminum