The duo swallow individual frames of 35mm film, excrete them and then wash them. Then the damage made to the surface of the film by the students' digestive system was examined using an electron microscope. These images were then blown up into large-scale black and white prints.
They were warned by medical experts that the biggest risk was colon perforation and obstruction, so they created a small capsule to loosely contain the rolled film frames. This would prevent the sharp edges from perforating the colon while allowing the acids and other digestive fluids to flush over the film. They then had to retrieve the film by doing their "business" in a bag, putting on gloves and sifting through.
I turn myself inside out: