The signatures of some drugs were no doubt observed after their virtues had been discovered. Poppy, for instance, under the doctrine was appropriated to brain disorders, on account of its shape like a head. But its reputation as a brain soother was much more ancient than the inference.
It is only necessary to give a few specimens of the inductive reasoning involved in the doctrine of signatures as revealed by the authors of the old herbals. The saxifrages were supposed to break up rocks; their medicinal value in stone in the bladder was therefore manifest. Roses were recommended in blood disorders, rhubarb and saffron in bilious complaints, turmeric in jaundice, all on account of their colour. Trefoil "defendeth the heart against the noisome vapour of the spleen," says William Coles in his "Art of Simpling," "not only because the leaf is triangular like the heart of a man, but because each leaf contains the perfect icon of a heart and in the proper flesh colour." Aristolochia Clematitis was called birthwort, and from the shape of its corolla was believed to be useful in parturition. Physalis alkekengi, bladder wort, owed its reputation as a cleanser of the bladder and urinary passages to its inflated calyx. Tormentilla officinalis, blood root, has a red root, and would therefore cure bloody fluxes. Scrophularia nodosa, kernel wort, has kernels or tubers attached to its roots, and was consequently predestined for the treatment of scrofulous glands of the neck. Canterbury bells, from their long throats, were allocated to the cure of sore throats. Thistles, because of their prickles, would cure a stitch in the side. Scorpion grass, the old name of the forget-me-not, has a spike which was likened to the tail of a scorpion, and was therefore a remedy for
