Not long ago, writer Mary Roach got a real hands-on lesson on the gut: she got to stick her hand inside a real live cow stomach, and experience digestion from the inside. When we heard about her adventure, we had to try it ourselves—so producer Tim Howard headed to Rutgers University to see, feel...and smell...a fistulated cow firsthand.

Then, we get a peek inside another stomach, this time a human one. Mary returns, with help from writer Fred Kaufman, to tell the improbable story of Dr. William Beaumont and hunter-turned-living-science-experiment Alexis St. Martin. In 1822, an accidental shooting left St. Martin with a hole in his gut that wouldn't heal, but didn't kill him either. Instead, the opening gave Dr. Beaumont a one-of-a-kind window into the human body. And the strange relationship that developed between doctor and patient changed the way we understand digestion.

Read more:

Fred Kaufman, A Short History of the American Stomach