Lichen caninus (known today as Peltigera canina)
Illustration by James Sowerby for James Edward Smith's English Botany. In the text accompanying this plate Smith wrote:
This is the "Ash-coloured Ground Liverwort", once celebrated as a cure for the bite of a mad dog; but we believe it never acted, even on the imagination of the patient, though it might on that of the learned Dr. Mead.
Richard Mead (1673-1754) had advocated the use of this lichen as a treatment for rabies.