Author Mary Roach takes readers through the digestive system in her new book, "Gulp: Adventures on the Alimentary Canal." The book uses science, history and popular culture to discuss gastrointestinal issues, such as fecal transplantation and the role of gut bacteria in health. Discussing the book, Roach says "Every step of the way, I was kind of floored by how effortlessly complex and amazing it all is, and I would like to impart a little bit of that to people. You go through life with these things inside you—these guts, these organs—and you never see them and consequently you never think about them. Until something goes wrong, and then you think about them all the time."