Other examples of the application of the Doctrine of Signatures are not difficult to be found among the quaintly-named plants enumerated in English herbals. The Lung-wort (Pulmonaria), spotted with tubercular scars, was a specific for consumption. The Bullock’s Lung-wort (Verbascum Thapsis), so called from the resemblance of its leaf to a dewlap, was employed as a cure for the pneumonia of bullocks. The Liver-wort (Marchantia polymorpha), liver-shaped in its green fructification, was a specific for bilious complaints. The Blood-root (Tormentilla), which derives its name from the red colour of its roots, was adopted as a cure for the bloody flux. The throat-like corolla of the Throat-wort (Campanula Trachelium), better known as the Canterbury Bell, caused it to be administered for bronchitis. Tutsan (Hypericum androsæmum) was used to stop bleeding, because the juice of its ripe capsule is of a claret colour. Brunella (now spelt Prunella) was called Brown-wort, having brownish leaves and purple-blue flowers, and was in consequence supposed to cure a kind of quinsy, called in German die braune. This plant has a corolla, the profile of which is suggestive of a bill-hook, and therefore it was called Carpenter’s-herb, and supposed to heal the wounds inflicted by edge-tools. Pimpinella Saxifraga, Alchemilla arvensis, and the genus Saxifraga, plants which split rocks by growing in their cracks, have been named “Breakstones,” and were administered in cases of calculus. Clary was transformed into Clear-eye, Godes-eie, Seebright, and Oculus Christi, and eye-salves were consequently made of it. Burstwort was thought efficacious in ruptures. The Scorpion-grass, or Forget-Me-Not (Myosotis), whose flower-spike is somewhat suggestive of a scorpion’s tail, was an antidote to the sting of that or other venomous creatures. The Briony, which bears in its root a mark significative of a dropsical man’s feet, was adopted as a cure for dropsy. The Moon-daisy averted lunacy; and the Birth-wort, Fig-wort, Kidney-vetch, Nipple-wort, and Spleen-wort were all appropriated as their names suggest, on account of fancied resemblances. The Toad-flax (Linaria), it may here be pointed out, owes its name to a curious mistake on the part of some believer in the Doctrine of Signatures. According to Dodoens, it was useful in the treatment of a complaint called buboes, and received its Latin name, Bubonium. A confusion between the words bubo and bufo (Latin for toad) gave rise to its present name of Toad-flax; and soon arose legends of sick or wounded toads seeking this plant and curing themselves with its leaves.
The general rules that guided the founders of the system of Plant Signatures, which were supposed to reveal the occult powers and virtues of vegetables, would seem to have been as under:—
Vegetables, as herbs and plants, or their fruit, seed, flowers, &c., which resemble some human member in figure, colour, quality, and consistence, were considered to be most adapted to that member, and to possess medical properties specially applicable to it.
All herbs or plants that in flowers or juice bear a resemblance to one or other of the four humours, viz., blood, yellow bile, phlegm, and black bile, were deemed suitable for treating the same humour, by increasing or expelling it.
All yellow-hued plants, if they were eatable, were thought to increase yellow bile. In this category were included Orach, Melons, Crocus, yellow Turnips, and all other yellow plants which have a sweet flavour.
Plants or herbs of a dull blackish colour, or of a brownish or a spotted hue, were held to be serviceable in the treatment of black bile. Some of them had a tendency to increase it, while others assisted in carrying it off. Thus, Smilax, Mandragora, many kinds of Parsley, Nightshade, and Poppies, having partly black, ash-coloured, and spotted flowers, intermixed with pale tints, by causing bad dreams, excite giddiness, vertigo, and epilepsy. Napellus, also, indicates in a most marked manner its poisonous and virulent nature, for its flower represents the skull of a dead man.
Plants which bear white flowers and have thick juice, which often grow in moist and extremely humid places, and which resemble phlegm or rheum, were thought to increase the very humours they represented. Others of a drier temperament were thought to correct and purify the same. Milky plants, as Tithymallus, Polygala, Sonchus, and Britalzar Ægyptiaca, were supposed to increase and accumulate milk in nurses.
Some plants of a red colour were believed to increase blood; some to correct and purify it; and others to benefit hemorrhoidal and dysenteric affections from a similarity of colour.
Plants of a mixed colour, as they unite in themselves a diversity of temperaments, were thought to produce a diversity of effects; whence two-coloured herbs were believed to possess and exercise a double virtue. On this principle, diverse colours were said to cure diverse humours in the human body; for example, Tripolium, Panacæa, and Triphera were considered beneficial for all humours.
Plants whose decoction and infusion, as well as colour and consistence, were like some humour of the human body, were declared to be appropriate for the purpose of evacuating that humour by attraction, or increasing it by incorporation.