The character and writings of Paracelsus are full of the strangest contradictions. Browning’s poem perhaps gives a better idea of his career than any prose account aiming at historical accuracy. His life was so strange that the imagination of a poet is needed to revitalise it for us to-day. His almost incredible boastfulness is the main characteristic that everyone remembers—the word “bombast” being, in all probability, coined from his name. In one of his works, after contemptuously dismissing all the great physicians who had preceded him—Galen, Avicenna and others—he remarks, “I shall be the Monarch and mine shall the monarchy be[36].” The conclusion that he was something of a quack can hardly be avoided, but at the same time it must be confessed that his writings were occasionally illumined with real scientific insight, and that he infused new life into chemistry and medicine. Paracelsus’ actual knowledge of botany appears to have been meagre, for not more than a couple of dozen plant names are found in his works. To understand his views on the properties of plants it is necessary to turn for a moment to his chemical theories. He regarded “sulphur,” “salt,” and “mercury” as the three fundamental principles of all bodies. The sense in which he uses these terms is symbolic, and thus differs entirely from that in which they are employed to-day. “Sulphur” appears to embody the ideas of change, combustibility, volatilisation and growth; “salt,” those of stability and non-inflammability; “mercury,” that of fluidity. The “virtues” of plants depend, according to Paracelsus, upon the proportions in which they contain these three principles. The medicinal properties of plants are thus the outcome of qualities that are not obvious at sight. How, then, is the physician to be guided in selecting herbal remedies to cure the several ailments of his patients? The answer to this question given by Paracelsus is summed up in what is known as the _Doctrine of Signatures_. According to this doctrine, many medicinal herbs are stamped, as it were, with some clear indication of their uses. This may perhaps be best understood by means of a quotation from Paracelsus himself (in the words of a seventeenth-century English translation). “I have oft-times declared, how by the outward shapes and qualities of things we may know their inward Vertues, which God hath put in them for the good of man. So in St Johns wort, we may take notice of the form of the leaves and flowers, the porosity of the leaves, the Veins. 1. The porositie or holes in the leaves, signifie to us, that this herb helps both inward and outward holes or cuts in the skin.... 2. The flowers of Saint Johns wort, when they are putrified they are like blood; which teacheth us, that this herb is good for wounds, to close them and fill them up” etc.