​PANACEA (Gr. πανάκεια, all-healing, from πᾶς, all, and ἁκεῖσθαι, to heal), a universal remedy, or cure for all diseases, a term applied in the middle ages to a mythical herb supposed to possess this quality. Many herbs have had the power of curing all diseases attributed to them, and have hence had the name of " all-heal "; such have been, among others, the mistletoe, the woundwort (Stachys palustris), the yarrow or milfoil, and the great valerian.