Lichens and the Doctrine of Signatures

Long ago, it was reasoned that the universe was made for human beings, and that God, who designed everything for his “chosen ones,” wanted to provide clues to help people learn the purposes of various things. This concept was called the doctrine of signatures. In accordance with this doctrine, Lobaria pulmonaria, a foliaceous lichen having a surface suggestive of a lung, was at the time used to treat tuberculosis and pneumonia. Likewise, Peltigera canina, a foliaceous lichen having the appearance of a row of teeth, was used to treat rabies. According to the doctrine of signatures, then, were a lichen to grow on a skull, that lichen would be good for the treatment of epilepsy; and were it to grow on the skull of a hanged criminal, its efficacy would be greatly enhanced.

The doctrine of signatures applied not only to lichen. For example, eyebright (Euphrasia oficinalis), being marked with a spot like an eye, was considered an excellent treatment for diseases of the eye. Bugloss (Anchusa oficinalis and several other forms), resembling a snake’s head, was considered good for snake bites. And Celandine, having yellow juice, was used to treat jaundice. The age of Shakespeare, Francis Bacon, and Galileo was one of fetish cures and quack remedies-a time when it was said “things bad for the heart are beans, pease, sadness, onions, anger, evile tidings, and the loss of friends.” With at least some of this, you must agree.