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 the sting of a scorpion. [The name forget-me-not was applied in England, until about a century ago, to the Ground Pine (Ajuga Chamœpitys), for the unpoetical reason that it left a nauseous taste in the mouth.] Oswald Crollius, who describes himself as Medicus et Philosophus Hermeticus, in his “Tractatus de Signatures,” writes a long and very pious preface explaining the importance of the knowledge of signatures. It is the most useful part of botany, he observes, and yet not a tenth part of living physicians have fitted themselves to practise from this study to the satisfaction of their patients. His inferences from the plants and animals he mentions are often very far-fetched, but he gives his conclusions as if they had been mathematically demonstrated. Never once does he intimate that a signature is capable of two interpretations. A few illustrations not mentioned above may be selected from his treatise.