This story is excerpted and adapted from Brandy Schillace’s Mr. Humble and Dr. Butcher: A Monkey’s Head, the Pope’s Neuroscientist, and the Quest to Transplant the Soul, published in March 2021 by Simon & Schuster. A grainy black-and-white film shuddered across television screens in the last days of May 1958. A man in a long white lab coat gestures to a corner, where a figure waits, shadowy and indistinct. He leads the creature into the light of a courtyard, revealing a strange composite body: a large mastiff dog with a…