There were improvised surgeons among the Spanish soldiers, who faced the American natives in the name of universal empire and church. There were also native physicians, organized around an important cultural center: the Franciscan college of Holy Cross in Tlatelolco. They perpetuated the ancestral medical traditions. In the dawning of New Spain, arrived here some physicians and surgeons prepared in important medical centers, such Sevilla, Salamanca, and Alcalá de Henares. Soon after a noteworthy exchange of medicinal plants and, generally, of therapeutic products between the old and new world took place. Likewise arrived here medical books printed in Europe and, in the second half of such century, appeared Newspanish medical books. When the first chair of medicine was established in the Royal University of México (1578), the number of medical publications increased until, in 1598, appeared the first medical thesis printed in America.