​The Elements of Materia Medica by Jonathan Pereira is a seminal work in the field of pharmacology, first published in 1839. Spanning two volumes, it offers a comprehensive examination of medicinal substances, focusing on their natural history, preparation, properties, composition, effects, and uses. Pereira’s approach is methodical and scientific, aiming to provide medical professionals with a systematic understanding of the substances they prescribe.​

The first volume delves into the general actions and classifications of medicines, with a particular emphasis on mineral substances. Pereira categorizes these substances based on their chemical properties and therapeutic effects, offering detailed descriptions and analyses. He also discusses the processes involved in preparing these medicines, ensuring that practitioners are well-informed about their origins and transformations before administration.​

The second volume shifts focus to vegetable and animal materia medica. Pereira explores a wide range of plant and animal-derived substances, detailing their natural history, chemical composition, and therapeutic applications. He provides insights into the preparation methods for these substances, highlighting the importance of proper handling to maintain efficacy. The volume concludes with an analysis of the effects and uses of these medicines, offering guidance on their application in various medical contexts.​

Throughout the work, Pereira emphasizes the importance of a scientific approach to medicine, advocating for a thorough understanding of medicinal substances to ensure their safe and effective use. His meticulous research and detailed descriptions have made The Elements of Materia Medica a valuable resource for medical professionals and scholars, contributing significantly to the development of pharmacology as a scientific discipline.