Both Paracelsus and Porta deprecate the use of foreign drugs, on the ground that in the country where a disease arises, there nature produces means to overcome it. This idea is one which constantly recurs in the herbals. In 1664 Robert Turner wrote, “For what Climate soever is subject to any particular Disease, in the same Place there grows a Cure.” There is ample evidence of the survival of this theory even in the nineteenth century; for instance, in the preface to Thomas Green’s ‘Universal Herbal’ of 1816 we find the remark, “Nature has, in this country, as well as in all others, provided, in the herbs of its own growth, the remedies for the several diseases to which it is most subject.” The notion persists indeed to the present day; there is a widespread belief among children, for example, that Docks always grow in the neighbourhood of Stinging Nettles, in order to provide a cure _in situ_! Whether this view contains any grain of truth or not, it certainly deserves our gratitude, since it led to Dr Maclagan’s discovery of Salicin as a cure for rheumatic fever. On the ground that in the case of malarial diseases “the poisons which cause them and the remedy which cures them are naturally produced under similar climatic conditions,” Maclagan sought and found, in the bark of the Willow, which inhabits low-lying, damp situations, this drug, which has proved so valuable in the treatment of rheumatism[40]. The doctrine of signatures is not the only piece of botanical mysticism associated with the name of Paracelsus. He was also a firm believer in the influence of the heavenly bodies upon the vegetable world, or, in other words, in botanical astrology. He considered that each plant was under the influence of some particular star, and that it was this influence which drew the plant out of the earth when the seed germinated. He held each plant to be a terrestrial star, and each star, a spiritualised plant. Giambattista Porta also believed in a relation between certain plants and corresponding stars or planets. A figure in his ‘Phytognomonica’ here reproduced (Text-fig. 110) shows a number of “lunar plants.” [Illustration: Text-fig. 110. Lunar Herbs [Porta, Phytognomonica, 1591].] In order to appreciate the attitude in which Paracelsus and his followers approached the subject of the relation between plants and stars, it is necessary to realise the position which Astrology had come to occupy in the Middle Ages[41].