Following his promotion, Van Swieten started a medical practice in Leiden. He initially ran his pharmacy in parallel, but in 1727 he handed this over to a son of his guardian Arnold Frans Coops. He saw many patients and soon, apparently with Boerhaave's permission, also started giving private lessons in pharmacy and
materia medicae, drawing 60 British students for his first course alone. He never was officially licensed to do so, and in 1734 the university forbade him to continue. Within a year or two, he could afford buying a stately house. Though they had no close personal relationship, Van Swieten was a great admirer of Boerhaave. After his study, Van Swieten kept attending Boerhaave's classes, making extensive notes on each and purportedly missing only one lecture between 1725 and 1738. Eventually, Van Swieten published these notes in five volumes between 1742 and 1771. When Boerhaave died in 1738, Van Swieten was by many considered his natural heir and he did take over part of Boerhaave's practice. However, he was not and had not expected to be offered his chair, since Catholics were not accepted as faculty at Leiden University. In September 1729, Van Swieten married Maria L. E. T. ter Beeck van Coesfelt (c.1711–1784), the daughter of a notary in
The Hague and the sister of a fellow student in Leiden. Though she did not feature prominently in Van Swieten's public life, contemporaries reported a very happy marriage. Between 1731 and 1746 they had six children, five in Leiden and one in Vienna. The first (1731) was named Elisabeth after his mother, the oldest son (1733) was named
Godfried after her father, and the youngest child (1746) was named Maria Theresia after
the Empress, who was also her godmother. Their son Godfried (later in Austria spelled Gottfried) became famous in his own right as Austrian ambassador and patron of the great
classical composers. November 1742 saw the death of Joannes Baptista Bassand, personal physician of the Holy Roman Empress
Maria Theresia and a former student of Boerhaave. As a Catholic and a foremost student of Boerhaave, Van Swieten received an offer to fill this position as well as that of director of the court library in early 1743. He respectfully declined, writing to a friend that he much preferred to remain "a small republican than to carry a pompous title that simply conceals a slavish existence". After one-and-a-half years of enticements, Van Swieten finally accepted the offer in October 1744. Before his letter of acceptance had arrived, Van Swieten found himself called to the court in
Brussels, where Maria Theresa's younger sister,
Maria Anna, Governor of the
Austrian Netherlands, was ailing following the birth of a stillborn child. While Maria Anna did not recover and died in early December, Van Swieten's swift response and confident actions had nevertheless endeared him further to Maria Theresa. By May 1745, the Van Swieten family had sold all their belongings in the Netherlands and traveled to Vienna. ==Career in Austria==