Simpson wrote Homœopathy, its Tenets and Tendencies, refuting the ideas put forward by Hahnemann.

[3] His services as an early founder of gynaecology and proponent of hospital reform were rewarded with a knighthood, and by 1847 he had been appointed as physician to the Queen in Scotland.

[8] His first role was as a general practitioner in the Stockbridge district based at 2 Deanhaugh Street,[9] and at the age of 28, he succeeded James Hamilton as Professor of Medicine and Midwifery at the University of Edinburgh.

The Air Tractor was the earliest known vacuum extractor to assist childbirth, however the method did not become popular until the invention of the ventouse over a century later.

[12] With regards to religion Simpson was a devout adherent of the Free Church of Scotland, but he refused to sign the Westminster Confession of Faith, because of what he believed to be its literal interpretation of the book of Genesis.

Dr Robert Mortimer Glover had first described the anaesthetic properties of chloroform upon animals in 1842 in a thesis which won the Harveian Society's Gold Medal that year, but had not thought to use it on humans (fearing its safety).

[20] On inhaling the chemical they found that a general mood of cheer and humour had set in, but suddenly all of them collapsed only to regain consciousness the next morning.

However, the son of the first baby delivered by chloroform explained that Simpson's parturient had been one Jane Carstairs, and her child was baptised Wilhelmina.

Subsequently, organising supplies to Florence Nightingale and Queen Victoria,[24] led to its use in obstetrics and for the military, and according to the British Medical Journal changed the face of medicine for a century.

[25] An account of some of Simpson's early uses of ether in childbirth are related by Manchester-based doctor Edmund Lund who visited him in 1847 and can be found in a manuscript held by special collections at the University of Manchester with the reference MMM/12/2.

[37] He was elected President of the Royal College of Physicians of Edinburgh in 1850[38] and an international member of the American Philosophical Society in 1863.

A burial spot in Westminster Abbey was offered to his family, but they declined and instead buried him closer to home in Warriston Cemetery, Edinburgh.

[20] Dr Alexander Russell Simpson, his nephew, inherited his town house at 52 Queen Street[45] and lived there until his death in 1916, when it was then bequeathed to the Church of Scotland.

Since then the building has been through many uses including being requisitioned by the army during the Second World War and being used as a centre for training Sunday School teachers in the 1950s.

The Quartermile development, which consists of the Old Royal Infirmary in Edinburgh, named its main residential street Simpson Loan in his honour.