[Petrus Hispanus, medieval physician elected as Pope named John XXI: Sketck of medicine in the Middle Age].

The Pope John XXI, named Pedro Rebuli Guiliani, was born in Lisbon, Portugal, around 1215. Known as Petrus Hispanus, Master Jullian, Peter of Spain, among other names. Besides medical studies, he studied Theology , Aristotelic Physics and Metaphysics at the University of Paris. He was named Professor of Medicine and Ophthalmology at the University of Sienna in 1247. In addition to several works about medicine, logic, and phylosophy, he authored the Tesaurus Pauperum ("Treasure of the Poor"), a prescription handbook of home-made, simple and cheap remedies. He was archbishop of Braga and Cardinal in 1272 and 1273, respectively. Elected Pope in 1276, he died tragically on May 20, 1277. Precedes this article a sketch of Medieval Medicine with emphasis on the XII and XIII centuries.