R’ Akiva asked them further: A dangling limb of an animal — what is it [considered]? They replied to him: [This] we have not heard, but we have heard that a dangling limb of a human is tahor, for so were the lepers in Jerusalem wont to do: He would go to a surgeon on the eve of Pesach, and [the latter would] sever it until he would leave over a barleycorn’s breadth and impale it on a thorn, and he would pull away from it. Then, that person would make his pesach [-offering] and the surgeon would make his pesach [-offering], and we believe that the matter is a kal vachomer.