Complex sentence: Also, self-appointed chief physician D. Willard Bliss, who had supplanted Garfield's usual physician, Jedediah Hyde Baxter, and the other doctors had guessed wrong about the path of the bullet in Garfield's body.
Split into simpler sentences: Also, self-appointed chief physician D. Willard Bliss had supplanted Garfield's usual physician, Jedediah Hyde Baxter. Bliss and the other doctors who attended Garfield had guessed wrong about the path of the bullet in Garfield's body.