The alimentary canal is classic Mary Roach terrain: the questions explored in Gulp are as taboo, in their way, as the cadavers in Stiff and every bit as surreal as the universe of zero gravity explored in Packing for Mars. Why is crunchy food so appealing? Why is it so hard to find words for flavors and smells? Why doesn't the stomach digest itself? How much can you eat before your stomach bursts? Can constipation kill you? Did it kill Elvis? In Gulp we meet scientists who tackle the questions no one else thinks of-or has the courage to ask. We go on location to a pet-food taste-test lab, a fecal transplant, and into a live stomach to observe the fate of a meal. With Roach at our side, we travel the world, meeting murderers and mad scientists, Eskimos and exorcists (who have occasionally administered holy water rectally), rabbis and terrorists-who, it turns out, for practical reasons do not conceal bombs in their digestive tracts.