Healing by herbs has always been popular both [xviii] with the classic nations of old, and with the British islanders of more recent times. Two hundred and sixty years before the date of Hippocrates (460 B.C.) the prophet Isaiah bade King Hezekiah, when sick unto death, "take a lump of Figs, and lay it on the boil; and straightway the King recovered." Iapis, the favourite pupil of Apollo, was offered endowments of skill in augury, music, or archery. But he preferred to acquire a knowledge of herbs for service of cure in sickness; and, armed with this knowledge, he saved the life of AEneas when grievously wounded by an arrow. He averted the hero's death by applying the plant "Dittany," smooth of leaf, and purple of blossom, as plucked on the mountain Ida. It is told in _Malvern Chase_ that Mary of Eldersfield (1454), "whom some called a witch," famous for her knowledge of herbs and medicaments, "descending the hill from her hut, with a small phial of oil, and a bunch of the 'Danewort,' speedily enabled Lord Edward of March, who had just then heavily sprained his knee, to avoid danger by mounting 'Roan Roland' freed from pain, as it were by magic, through the plant-rubbing which Mary administered." In Shakespeare's time there was a London street, named Bucklersbury (near the present Mansion House), noted for its number of druggists who sold Simples and sweet-smelling herbs. We read, in [ix] _The Merry Wives of Windsor_, that Sir John Falstaff flouted the effeminate fops of his day as "Lisping hawthorn buds that smell like Bucklersbury in simple time." Various British herbalists have produced works, more or less learned and voluminous, about our native medicinal plants; but no author has hitherto radically explained the why and where fore of their ultimate curative action. In common with their early predecessors, these several writers have recognised the healing virtues of the herbs, but have failed to explore the chemical principles on which such virtues depend. Some have attributed the herbal properties to the planets which rule their growth. Others have associated the remedial herbs with certain cognate colours, ordaining red flowers for disorders of the blood, and yellow for those of the liver. "The exorcised demon of jaundice," says Conway, "was consigned to yellow parrots; that of inflammatory disease to scarlet, or red weeds." Again, other herbalists have selected their healing plants on the doctrine of allied signatures, choosing, for instance, the Viper's Bugloss as effectual against venomous bites, because of its resembling a snake; and the sweet little English Eyebright, which shows a dark pupil in the centre white ocular corolla, as of signal benefit for inflamed eyes.