The Doctrine of Signatures

This week’s blooming plant is the lungwort, or pulmonaria officinalis, a low-lying shade plant with speckled leaves that has always been the best example of the pre-modern theory of the Doctrine of Signatures for me.  An ancient theory that was embraced and expanded by several influential Renaissance writers, the doctrine held that the appearance of plants was an indication of their potential curative powers, or “virtues”.  Just as God created disease, he also gave man cures, hidden in nature, but marked by clues, or divine signatures.  I use the doctrine in class as one example of how closely tied medieval and early modern people were to nature, as clever a manifestation of God’s creation as themselves.  Lungwort, with its speckled lung-shaped leaves, was widely believed to contain virtues which could cure diseases of the lung, hence the name.

Lungwort in my garden yesterday, in British Library MS Egerton 747 (Nicolaus of Salerno, Tractatus de herbis , c.1280-1310), and as drawn Elizabeth Blackwell for her Curious Herbal, 1739 and Magdalena Bouchard  for Giorgio Bonelli’s, Hortus romanus, vol. 2, Rome, 1774, tab. 27  (Wellcome Library).

Paracelsus, in most ways a Renaissance medical revolutionary, nevertheless embraced the ancient doctrine in his “great” surgery book (Die grosse Wundartznei), published in 1537:  “I have oft-times declared, how by outward shapes and qualities of things we may know their inward virtues, which God has put in them for the good of man.  So in St. John’s Wort, we may take notice of the form of the leaves and flowers, the porosity of the leaves, the veins [which] signify to us that this herb helps both inward and outward holes or cuts in the skin.  The flowers of St. John’s Wort, when they are purified are like blood; which teaches us, that this herb is good for wounds.”  St. John’s Wort doesn’t seem as conspicuously “signed” as lungwort to me, but this passages shows you how far Renaissance doctors were prepared to go. Paracelsus does not mention the plant’s medieval virtue (illustrated below):  that of demon repellent!

BL MS. Sloane 4016:  St. John’s Wort (Hypericum perforatum) repelling a demon, Northern Italy, c. 1440.

Later in the sixteenth century, another Renaissance “scientist” (you have to put that word in quotations before Sir Isaac Newton, at the very least) elaborated upon the doctrine in words and images.  Giambattista della Porta, who was also a relatively well-known playwright, was very interested in outward appearances, not only of plants but also of animals and humans, and how appearance affected behavior. His Phytognomonica (1588) contains wonderful, literal images of the doctrine, like the one below, of “ocular” plants like the aptly-named eyebright, which was said to improve sight.

Giambattista della Porta, Phytognomonica (1588), and a 1923 updated image from the Wellcome Library, London.

You can go on and on with the doctrine of signatures, so I’m going to end with one last image of a plant in my garden:  a maidenhair fern, which was (of course), perceived to be a plausible cure for that most common of ailments:  baldness.