William says: "You will, nonetheless, find none that generates or creates a substance like itself either in itself or outside itself.  Of this kind is the fish--as I have elsewhere told you--which is called the sting ray (torpedo).  By mere contact with it it makes the hand of the one who touches it so numb that it can do nothing at all for a whole hour. 

"And what is even more amazing: if it is touched with a lance of whatever length, it produces the same numbness in the hand of the one who touches it--I do not mean: in the lance." 

Original Latin