When he has transferred all the fleas in this way, he removes one from the now full jar, carefully pulls off its back legs, and places it on the table before the original jar. He commands "Jump," but the flea does not move. He takes another flea from the jar, carefully pulls off its back legs, and places it on the table. Again he commands "Jump," but the flea does not move. Methodically, he goes through this same procedure with the remaining fleas, and gets the same results.

The scientist records in his notebook, "A flea, when its back legs are pulled off, cannot hear."