The pharmacist Theodoro Peckolt was one of the most important figures in the history of the chemistry of natural Brazilian products. Like other nineteenth-century pharmacists in Brazil, he developed formulations and sold them at his pharmacy in Rio de Janeiro, and these enjoyed great prestige in the eyes both of the public and the medical community. The article discusses the relation between the illness originally called "opilação" (ancylostomiasis, or hookworm) and nineteenth-century treatment. It focuses especially on Peckolt Pharmacy's "Doliarina and iron powder," a formulation extracted from the Ficus gomelleira rubber plant. One of the article's goals is to use modern methods to analyze Ficus gomelleira and identify the chemical composition of the drug.