For some people, a sliced tongue can be fatal.
For some people, a sliced tongue can be fatal. Erik Isakson/Getty Images

A person with normal clotting ability would have to lose nearly 40 percent of his blood immediately to die of blood loss. The arteries with this bloodletting potential, though, such as the radial artery in the arm and femoral artery in the leg, are buried under too much flesh to be nicked by even the heaviest manila cardstock. “It would be tough to kill yourself on a paper cut,” says Beau Mitchell, a bleeding-disorder specialist at the New York Blood Center, an organization that supplies blood to hospitals.

A stationery slice could turn deadly, however, for the 12,600 people in the U.S. with severe hemophilia and the 200 Americans with a disorder called Glanzmann’s thrombasthenia. If one of these people sliced an exposed blood vessel, like the one under the tongue, their blood would not be able to clot to plug the wound. Glanzmann’s patients are especially vulnerable, Mitchell says, and could lose 25 percent of their blood within eight hours from such a cut. Without medical treatment, their bodies couldn’t produce enough new blood cells to replenish those lost, and they would die within a few days.

Although people with these diseases should probably avoid licking envelope seals, we should all avoid ninjas armed with paper daggers. According to Ronald Duncan, a master of the martial art ninjitsu, anyone can fold a piece of paper, origami-style, to fashion a sharp knife. Duncan trains police officers and the military to look out for these weapons because a jab to the carotid artery in the neck could be fatal. “A few other parts of the body can bleed out in 35 seconds if someone is really adept,” he says. “But we try not to make this information available to too many people.”

This article originally appeared in the December 2009 issue of Popular Science_ magazine._