The physician and author John Ayrton Paris (1785-1856), several of whose other medical and popular works have been reissued in the Cambridge Library Collection, published the first edition of this book in 1812. It was immediately successful, and went into eight further editions until 1843: this reissue is of the 1820 third edition. Many volumes on materia medica existed at the time, and Paris claims in his preface that he is not disparaging these competitor works, but that they presume too much prior knowledge on the part of the reader. His own work is designed to inform the student of the properties and effects of each medicinal substance, and how they function, both alone and in combinations. This will lead to greater understanding of the efficacy of medicines, and also help to prevent their adulteration. The qualities of each ingredient are discussed, and formulae and doses provided.