Between the sixteenth and the nineteenth centuries, doctors and apothecaries conceptualized the medical use of sassafras within the framework of natural philosophy. Medicine in the early-modern era had more in common with the medieval worldview than with modern medicine. Natural philosophers read the “book of nature,” and accepted occult or secret ways of knowing that now seem antithetical to modern scientific methods. Most medical thought of the era was based on the teachings of Galen (119-216 CE), the physician to the emperors Marcus Aurelius (r. 161-180) and Commodus (r. 177-192). His teachings dominated medical thought in the medieval Latin, Greek, and Arab worlds. While Galen did not fully develop the theories of medical practice during his era, western physicians inherited his writings in the middle ages, particularly The Art of Medicine.
Galen’s works were printed in Greek in 1525 sparking a reinvigoration of Galenic thought and study. Galenism survived in academic medicine up to 1800 because no new discovery could undermine the entire system of thought. Galenism was flexible because its adherents were able to incorporate contradictory ideas and discoveries into the existing intellectual framework.
Classical, medieval, and early-modern Galenic medicine taught that the body was comprised of four humours. Each humour was comprised of the ancient elements of water, earth, fire, and air, and the amount of each element contributed to every humour possessing a quality. Phlegm was cold and wet; black bile, cold and dry; blood, hot and wet; and choler (yellow bile), hot and dry. Each humour contributed to a person’s temperament. Yellow bile made individuals quarrelsome and black bile made people melancholic. Every person’s temperament reflected the unique blend of humours within their body. In addition to the four classical elements and the four humours, the body was made up of five other “naturals:” complexions or temperament reflecting the individual’s blend of hot, cold, wet, and dry; parts of the body including the three major organs of the liver, heart, and brain; an animating spiritus which is an pneuma produced by the heart; virtues; and the operations of individual organs.
Galen viewed the body as a mass of fluids made up of the four humours rather than distinct body parts and biological systems. The body would fall sick when there was an excess of one humour. The physician’s role was to identify which humour was in excess and then to rebalance the humoural levels. Medicines were considered hot, wet, cold, or dry, and their effect on the body depended on their classification. Treatment of a sick patient was done through contraries, so, a cold medicine would cure a hot disease. However, diseases rarely affected just one humour. William Clowes, in his 1588 translation of the Spanish physician John Almenar entitled A prooed pratise for all young chirurgians, remarked “for as corruption seldome happeneth in one onely humour (sayth Galen. 1. regim. acut.) euen so you shall seldome finde the signes foretelling one onely humour.”
According to the notions of early-modern natural philosophy, sweating helped to rebalance humours and aided in curing certain diseases. Sassafras is a sudorific wood which, when ingested, made patients sweat. There were four known sudorific woods: sassafras, guaiacum, sarsaparilla, and china root. They were prescribed by doctors to be taken together to induce sweating in patients in order to rebalance humoural levels.