Years ago, in the pioneer days of aviation, a pilot was making a flight around the world. After he had been gone for some two hours from his last landing field, he heard a noise in his plane, which he recognized as the gnawing of a rat. He realized that while his plane had been on the ground a rat had gotten in. For all he knew the rat could be gnawing through a vital cable or control of the plane. It was a very serious situation. He was both concerned a…