I once saw a monkey jerking it. It was at the zoo, of course, where several blue-faced baboons swung over plaster tree trunks and romped across a funny little walkway modeled after a hanging bridge. As much as schools want zoo visits to be positive, educational experiences that transform the lives of young people forever, what has stuck with me in a lifetime's worth of field trips is deflated polar bears, hobbled cheetahs, and a monkey ignoring all the other monkeys to beat his meat.