A prominent Polish scientist conducted very important experiment. He trained a flea to jump upon giving her a verbal command (Jump!).

In a first stage of experiment he removed flea's leg, told her to jump, and the flea jumped. So he wrote in his scientific notebook: Upon removing one leg all flea organs function properly.

So, he removed the second leg, asked the flea to jump, she obeyed, so he wrote again: Upon removing the second leg all flea organs function properly.

Thereafter he removed all the legs but one, the flea jumped when ordered, so he wrote again: Upon removing the next leg all flea organs function properly.

Then he removed the last leg. Told flea to jump, and nothing happened. He did not want to take a chance, so he repeated the experiment several times, and the leg less flea never jumped. So he wrote the conclusion: Upon removing the last leg the flea loses sense of hearing