Hydra. Name of a monstrous serpent in the Lake Lerna, with numerous heads. When one of these heads was cut off, another or two others immediately grew in its place, unless the blood of the wound was stopped by fire. The destruction of the Hydra was a labor assigned to Hercules, which he accomplished by the aid of Iolaus, who applied lighted brands or a heated iron as each head was removed. The arrows of Hercules, being dipped in the Hydra's blood, caused incurable wounds.
