Nils Rosén, ennobled Rosén von Rosenstein in 1762, has been characterized as the father of Swedish medicine. He was born in Sexdräga outside Gothenburg. In 1720 his father sent him to the University of Lund in order to study theology to be a clergyman. But at Lund Rosén in 1723 began to attend the lectures in medicine given by Kilian Stobaeus, who also permitted Rosén to accompany him during professional calls as well as availing him his extensive library. For financial reasons Rosén left Lund in 1724, accepting a tutorship in Stockholm, where he continued his medical studies and soon became well known for his profound knowledge and great talents in medical matters. In 1728, as a result of the efforts of his friend and patron, Casten Rönnow in Stockholm, Rosén was offered an assistant professorship in medicine at Uppsala by Olof Rudbeck the Younger. At Uppsala Rosén defended a dissertation under Professor Lars Roberg and at the age of 22 he was officially appointed. But to be a university teacher Rosén had to acquire a doctor's degree, which at this time could not be done in Sweden. Rosén therefore arranged for a study trip abroad in company and at the expense of a young baron, Mauritz Posse. This tour continued for three years and included visits to Friedrich Hoffmann in Halle, where he also attended the lectures by Juncker at the "Orphanotropium" (which may have inspired his interest for pediatrics), to Montpellier, Paris, Geneva, and to the famous Boerhaave in Leyden. He also met Albrecht von Haller, with whom he later maintained a lively correspondence. The main destination was the small university of Harderwijk in Holland, where he, in 1730, defended his doctor's degree with a dissertation on the writing of medical case records. Five years later Linnaeus got his doctor´s degree at the same university.In 1731 Rosén was back in Uppsala to start his academical teaching, where he promptly roused the medical teaching from its deep decline. Anatomy was restored to its previous place of honor under Olof Rudbeck the Elder. Rosén conducted a public demonstration of the human body in the anatomical theatre built by Rudbeck and performed dissecting exercises on animal and human corpses. In 1736-38 he published his Compendium Anatomicum, which is the first really good anatomical textbook in Swedish. In 1734 he became Assessor of the Collegium Medicum and in 1735 was appointed physician to King Fredrik I.When professor Olof Rudbeck the Younger died in 1740 Rosén was appointed the chair of anatomy and botany and upon the retirement of Professor Lars Roberg, Carl Linnaeus was appointed professor of theoretical and practical medicine. However, with the consent of the Chancellor they changed the subjects of their professorships. Rosén assumed responsibility of anatomy, physiology, pathology, therapeutics and chemistry as well as the directorship of the Nosocomium Academicum (Akademiska Sjukhuset), while Linnaeus assumed responsibility for botany, materia medica, dietetics and the directorship of the Botanical Garden.Rosén was one of the first Swedish physicians to use quinine as a remedy against malaria and he also propagated for variolation to immunize against smallpox. A sample of the purulent exudate for a smallpox victim was transferred to the person to be immunized in order to provoke a mild attack of the disease. The benignity of the infection produced by the inoculation was not always assured. Indeed Rosén had the tragic experience of having inoculated his three-year-old twin daughter, who later died. But he also inoculated the children of the royal family, the crown-prince (later King Gustav III) and his sisters and brothers, for which he was granted a national reward of 100 000 Swedish daler.However, the most important contribution by Rosén was to introduce better understanding among physicians and mothers of the children. Twenty percent of the infants died before nine year of age. For several years Rosén wrote advice on the care and feeding of infants and on the most common children's diseases and their treatment for publication in the Swedish almanacs. In 1764 these were collected and published in book form - a book that, translated into many languages, have had immeasurable importance in all civilized countries, especially because it was written in an easily understood language intended for the common man. It is said to be one of the most influential medical books ever written by a Swede and still ranks as a milestone in the history of pediatrics.Nyström Eva, in Svenskt Biografiskt Lexikon, Band 30 (1998-2000), pp 425-433, with full bibliography; Vahlquist, Bo & Arvid Wallgren (eds) Nils Rosén von Rosenstein and his Textbook on Paediatrics (Supplement 156 of Acta Paedicatrica), 1964.