Few cases of pathological laughter have been reported, says Ramachandran, but all seem to involve parts of the limbic system affecting emotions. Q. An overindulgent parent, you buy your kid too many helium balloons at the fair, then look back shocked to see her soaring 100 feet into the sky. Just hope there's no big wind. As the gas leaks out, your high-flying daughter should come back down to Earth. Could cause little reaction, or death if vital tissue is involved.
Accidents happen, as when a strike badly misses target prey.
Then there are those stories of cornered or injured snakes biting themselves to commit suicide. Certainly a snake under stress may self-inflict, most notably when it's pinned with a hook or stick and goes into a frenzy. Brought into a TV studio, a sidewinder rattlesnake began self-biting and died shortly afterward. Extreme cold is another factor. On several instances I found rattlesnakes with their fangs embedded mid-body after euthanization.