When Jason arrived at Colchis, he sent to King Æetes, and asked of him the Golden Fleece.  To this Æetes replied that he might have it, provided he could yoke the two brazen-footed bulls with flaming breath, which had been a present from Vulcan, and with them plough a piece of land, and sow it with the dragon’s teeth.  Pallas had given Æetes half the teeth of the dragon of Thebes, which had been slain by Cadmus.