[Picture: Hercules fighting the Lion] There was a second labour ready for Hercules—namely, the destroying a serpent with nine heads, called Hydra, whose lair was the marsh of Lerna.  Hercules went to the battle, and managed to crush one head with his club, but that moment two sprang up in its place; moreover, a huge crab came out of the swamp, and began to pinch his heels.  Still he did not lose heart, but, calling his friend Iolaus, he bade him take a fire-brand and burn the necks as fast as he cut off the heads; and thus at last they killed the creature, and Hercules dipped his arrows in its poisonous blood, so that their least wound became fatal.  Eurystheus said that it had not been a fair victory, since Hercules had been helped, and Juno put the crab into the skies as the constellation Cancer; while a labour to patience was next devised for Hercules—namely, the chasing of the Arcadian stag, which was sacred to Diana, and had golden horns and brazen hoofs.  Hercules hunted it up hill and down dale for a whole year, and when at last he caught it, he got into trouble with Apollo and Diana about it, and had hard work to appease them; but he did so at last; and for his fourth labour was sent to catch alive a horrid wild boar on Mount Erymanthus.  He followed the beast through a deep swamp, caught it in a net, and brought it to Mycenæ.