Jonny's little experiment

A teacher at an infant school is doing a science lesson and asks all the children to perform an experiment of their own choosing. After the children have been busy for a few minutes, she gets to the desk of little Johnny. Johnny has a spider on his desk and she asks what he was doing.

"Well Miss, the spider's name is Herbert and watch this." Jonny then bends down to the spider and whispers "Run, Herbert, Run" and the spider, as if by magic, moves across the desk. The teacher is a little mystified. Johnny then gets a hold of the spider and removes one leg. The teacher is taken aback but lets the experiment continue. Johnny again whispers "Run, Herbert, Run" and the spider, as if by magic, moves across the desk. Johnny then gets ahold of the spider and removes another 2 legs and repeats the experiment. "Run, Herbert, Run" and the spider does continue to move across the desk, a bit in a somewhat limp fashion. By this time the teacher is getting a little concerned.

The experiment continues in the same vein until Herbet, the spider, has one leg left (the teacher at this point is totally mortified). Johnny then bends down to the spider and again removes the last leg so that Herbert is now just a blob and again he whispers "Run, Herbert, Run" but Herbert doesn't move. He repeats the command again but a little bit louder. After serveral attemps, Johnny is now shouting at the spider "Run, Herbert, Run" but still no movement. Johnny then looks at the teacher and she asks "Well, Johnny, an interesting experiment, but what are you trying to prove with it?" Johnny replies, "Well, Miss, spiders with no legs are deaf"