A mother saw her three-year-old son put nickel in his mouth and swallowed it. She immediately picked hime up, turned him upside down and hit him on the back, whereupon he coughed up two dimes. Frantically, she called to the father outside. Your son just swallowed a nickel and coughed up two dimes! What shall I do? Yelled back the father, Keep feeding him nickels!