Stephen Hales (17 September 1677 – 4 January 1761[1]) was an English clergyman who made major contributions to a range of scientific fields including botany, pneumatic chemistry and physiology.

He was the sixth son of Thomas Hales, heir to Baronetcy of Beakesbourne and Brymore, and his wife, Mary (née Wood), and was one of twelve or possibly thirteen children.

Hales was admitted as a Fellow of Corpus Christi in 1703, the same year as he obtained the degree of Master of Arts, and was ordained as Deacon at Bugden, Cambridgeshire.

He was an assiduous minister – in addition to parish duties he enlarged and repaired the church and commissioned a new water supply for the village – and well regarded although there is some evidence that his experimental work on animal physiology was viewed with misgivings.

At the age of seventy Hales was chosen by the president and fellows of the Royal College of Physicians to preach the annual Crounian Sermon in the church of St Mary-le-Bow.

The first volume, Vegetable Staticks (1727), contains an account of experiments in plant physiology and chemistry; it was translated into French by Georges-Louis Leclerc, Comte de Buffon in 1735[13] and into Italian by Maria Angela Ardinghelli in Naples in 1750-1752.

[18] In Vegetable Staticks Hales also described experiments that showed that "... air freely enters plants, not only with the principal fund of nourishment by the roots, but also thro' the surface of their trunks and leaves".

While Hales' work on the chemistry of air appears primitive by modern standards, its importance was acknowledged by Antoine Lavoisier, the discoverer of oxygen.

Hales and Stuckeley performed a wide range of studies including making casts of the trachea and bronchial trees of dogs using molten lead and measuring the water lost due to breathing.

[22] Hales also described a diverse range of work in Haemastaticks including his attempts to find substances that could be used to dissolve bladder stones or calculi.

This aim was unsuccessful but as part of this work he developed a double lumen bladder catheter and devised special forceps to enable the removal of urinary stones.

Hales was one of several people in the early 18th century (other notable inventors being John Theophilus Desaguliers, Mårten Triewald and Samuel Sutton) who developed forms of ventilators to improve air quality.

[3] They were widely installed in ships, prisons and mines and were successful in reducing disease,[2] and aerating the lower decks of Royal Navy vessels to combat dry rot in the hulls.

In 1723 Bray became ill and appointed trustees, including Hales, to administer a bequest from Abel Tassin, Sieur d’Allone for 'The Conversion of Negroes Slaves in the West Indies'.

These charities became incorporated into a scheme led by James Oglethorpe to establish a charitable colony for the poor, 'honest industrious debtors' and persecuted (Protestant) foreigners.

Hales may well have felt a personal commitment to this scheme since his brothers had been imprisoned for debt following the failure of the South Sea Company and one, William, died of Gaol Fever in Newgate Prison.

[2] From the Nobel Prize in Medicine acceptance speech given by Werner Forssmann in 1956: "The credit for carrying out the first catheterization of the heart of a living animal for a definite experimental purpose is due to an English parson, the Reverend Stephen Hales.