William Cullen FRS FRSE FRCPE (/ˈkʌlən/; 15 April 1710 – 5 February 1790) was a British physician, chemist and agriculturalist from Hamilton, Scotland, who also served as a professor at the Edinburgh Medical School.

The competition between the two systems had knock-on effects in how patients were treated worldwide, especially in Italy and Germany, during the end of the eighteenth and beginning of the nineteenth century.

His best known work was First Lines of the Practice of Physic, which was published in a series of editions between 1777 and 1784,[9] and inventing the basis of modern refrigeration.

[10] His father William was a lawyer retained by the Duke of Hamilton as factor, and his mother was Elizabeth Roberton of Whistlebury.

[13] After two years as assistant apothecary to Mr Murray of Henrietta Street, London, he returned to Scotland in 1732 to establish himself in general medical practice in the parish of Shotts, Lanarkshire.

His great abilities, enthusiasm, and use of practical demonstrations for instruction, made him a successful and highly popular teacher, attracting large classes.

In 1747, Cullen was awarded Britain's first independent lectureship in Chemistry and was elected President of the Faculty of Physicians and Surgeons of Glasgow.

[14] In 1755 he was enticed by Lord Kames to become Professor of Chemistry and Medicine at the University of Edinburgh in place of Prof Andrew Plummer.

[17] In 1748, an account had been published in The Edinburgh Physical and Literary Essays of an experiment in which Cullen used an air pump to create a partial vacuum over a container of diethyl ether, which then boiled, absorbing heat from the surroundings.

[14] On the death of Robert Whytt, the professor of the institutes of medicine, in 1766, Cullen accepted the chair, at the same time resigning that of chemistry.

[10] On 8 January 1790 he was presented with a silver platter costing 50 guineas by the Lord Provost, Thomas Elder and the city baillies, for his long service in the university.

Indeed, a large number of the doctors who taught in Edinburgh's medical school from the 1790s to 1810s had studied with him, including the chemist Joseph Black, the anatomist Alexander Monro Secundus, and the naturalist John Walker.

Cullen's emphasis on the practical benefits of chemistry made his ideas popular amongst farmers, industrialists, naturalists and doctors alike.

[24] Because medical practitioners were not as established as they are now, patients generally took advice from a myriad of sources, including personal experience, books, and several consultations.

[24] Cullen managed his consultations with great efficiency; he usually read the letters early in the morning and his secretary-amanuensis would record and mail back his responses.

"[24] Like many physicians in his time, Cullen would often prescribe therapeutics "to support the patient's endangered constitution and assist the body's natural healing tendencies.

[25] Despite the lack of original work, some believed that Cullen's attempt to organize existing knowledge was actually a sign of his "practical sagacity" as a practitioner.

[24] Like many prominent medical figures in the 18th century, William Cullen took a great interest in the nervous system.

He defined the nervous system as an "animated machine" whose main function is to "perform a variety of motions," communicate and interact with "external bodies.

His first book-length publication was Synopsis Nosologiae Methodicae (1769), Cullen's very influential nosology, or classification of diseases.

Work on his magnum opus, First Lines of Practice of Physic, occupied much of his time in the 1770s and 1780s, but he did manage one final publication.