João Rodrigues de Castelo Branco, better known as Amato Lusitano and Amatus Lusitanus (1511–1568), was a notable Portuguese Jewish physician of the 16th century. He is sometimes is said to have discovered the valves in the azygos vein. Life Lusitano was born in 1511 in Castelo Branco, Portugal. He was a descendant of a Marrano family called Chabib (= Amatus, "beloved" in Latin), and was brought up in the Jewish faith. After having graduated with honors as M.D. from the University of Salamanca, he was unable to return Portugal for fear of the Inquisition. He went to Antwerp for a time and then traveled through the Netherlands and France, finally settling in Italy. His reputation as one of the most skillful physicians of his time preceded him there, and during his short sojourn at Venice, where he came in contact with the physician and philosopher Jacob Mantino, he attended the niece of Pope Julius III and other distinguished personages. In the 1540s Amatus was in Ferrara, where Giambattista Canano one of the leading anatomists of the time was performing numerous dissections. According to Amato they dissected twelve cadavers in a single year but it is unclear whether Amato was actively participating or only watching. He later reported Canano's finding of a valve at the beginning of the azygos vein which Canano had made on this occasion and has for this reason sometimes mistakenly taken for the discoverer of the venous valves. During his sojourn in Ferrara, which lasted for six years, Amatus Lusitanus received an invitation from the King of Poland to move to that country, which he declined, preferring to settle in Ancona, where religious tolerance existed. Meanwhile, his reputation grew higher and higher. Jacoba del Monte, sister of Pope Julius III, was one of his patients; and he prescribed also for Julius himself, to whose sick-bed he was later summoned. With the accession of Paul IV, Amatus underwent all the sufferings which the Marranos of Ancona had to endure from this pope. He took refuge in Pesaro, leaving behind him all his possessions, including several manuscript works, the loss of which he greatly deplored. One of these manuscripts, however, the fifth part of his Centuriæ, was later restored to him and published. During his sojourn at Pesaro he received an invitation from the municipality of Ragusa, After staying for some months he left the city for Thessaloniki, which