Scottish physician, chemist and agriculturalist, and one of the most important professors at the Edinburgh Medical School, during its heyday as the leading centre of medical education in the English-speaking world.
Cullen was also a central figure in the Scottish Enlightenment. He was David Hume’s physician and friend, and on intimate terms with Adam Smith, Lord Kames (with whom he discussed theoretical and practical aspects of husbandry), Joseph Black, John Millar, and Adam Ferguson, among others.
He was President of the Royal College of Physicians and Surgeons of Glasgow (1746–47), President of the Royal College of Physicians of Edinburgh (1773–1775) and First Physician to the King in Scotland (1773–1790). He was also, incidentally, one of the prime movers in obtaining a royal charter for the Philosophical Society of Edinburgh, resulting in the formation of the Royal Society of Edinburgh in 1783.
Cullen was a beloved teacher, and many of his students became influential figures in their own right. His best-known students—many of whom continued to correspond with him during his long life—included (in addition to Joseph Black, who became his colleague) Benjamin Rush, a central figure in the founding of the United States of America; John Morgan, who founded the first medical school in the American colonies (the Medical School at the College of Philadelphia); William Withering, the discoverer of digitalis; Sir Gilbert Blane, medical reformer of the Royal Navy; and John Coakley Lettsom, the philanthropist and founder of the Medical Society of London.
Special mention must be made of Cullen’s student-turned-opponent, John Brown, who developed the medical system known as Brunonianism, which rivalled Cullen’s. This was to have immense influence, especially in Italy and Germany, during the end of the eighteenth and beginning of the nineteenth century.
Cullen was also a successful author. He published a number of medical textbooks, mostly for the use of his students, though they were popular throughout Europe and the American colonies as well. His best known work was First Lines of the Practice of Physic, which was published in a series of editions between 1777 and 1784.
He died on 5 February 1790, aged 79, in Edinburgh, Scotland.

Link to Wikipedia biography