An astonishing group of sixty-nine "Character Heads" by German sculptor Franz Xaver Messerschmidt (1736-1783) has fascinated viewers, artists, and collectors for more than two centuries. The heads, carved in alabaster or cast in lead or tin alloy, were conceived outside the norm of conventional portrait sculpture and explore the furthest limits of human expression. Since their first exposure to the public in 1793, artists, including Egon Schiele (1890-1918),...