Stephen Hales

Stephen Hales, FRS (September 17, 1677 – January 4, 1761) was an English physiologist, chemist and inventor. Hales studied the role of air and water in the maintenance of both plant and animal life. He gave accurate accounts of the movements of water in plants, and demonstrated that plants absorbed air. Hales discovered the dangers of breathing stale air, and invented a ventilator which improved survival rates when employed on ships, in hospitals and in prisons. Hales is also credited with important developments in the collection of gases.

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Life and work

Stephen Hales was born at Bekesbourne in Kent. In June 1696 he was entered as a pensioner of Corpus Christi College, Cambridge, with the view of taking holy orders, and in February 1703 was admitted to a fellowship. In 1708 Hales was presented to the perpetual curacy of Teddington in Middlesex, where he remained all his life, notwithstanding that he was subsequently appointed rector of Porlock in Somerset, and later of Faringdon in Hampshire.

In 1717 Hales was elected fellow of the Royal Society, which awarded him the Copley Medal in 1739. In 1732 he was named one of a committee for establishing a colony in Georgia, and the next year he received the degree of Doctor of Divinity from Oxford. He was appointed almoner to the princess dowager of Wales in 1750. On the death of Sir Hans Sloane in 1753, Hales was chosen foreign associate of the French Academy of Sciences.

Known as a pioneer of experimental physiology, Hales showed that some reflexes are mediated by the spinal cord. Hales studied stones taken from the bladder and kidneys and suggested solvents which might reduce them without surgery. He also invented the surgical forceps.

Hales is best known for his Statical Essays. The first volume, Vegetable Staticks (1727), contains an account of numerous experiments in plant physiology — the loss of water in plants by evaporation, the rate of growth of shoots and leaves, and variations in root force at different times of the day. The second volume (1733) on Haemastaticks, containing experiments on the "force of the blood" in various animals, its rate of flow, and the capacity of the different vessels.

Stephen Hales died on January 4, 1761 in Teddington at the age of 84. He was buried under the tower of the church where he had worked many years.

Testimony

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. This scientifically interested layman undertook in Tordington (sic) in 1710, 53 years after the death of William Harvey (1578–1657), the first precise definition of the capacity of a heart. He bled a sheep to death and then led a gun-barrel from the neck vessels into the still-beating heart. Through this, he filled the hollow chambers with molten wax and then measured from the resultant cast the volume of the heartbeat and the minute-volume of the heart, which he calculated from the pulse-beat. Besides this, Stephen Hales was also the first, in 1727, to determine arterial blood pressure, when he measured the rise in a column of blood in a glass tube bound into an artery." ^[1]

The genus of trees Halesia is named after him.

Further reading

• Hales, Stephen (1727) Vegetable Staticks, London: W. and J. Innys — from the Missouri Botanical Garden's library
• Hales, Stephen (1738). "Philosophical experiments: containing useful, and necessary instructions for such as undertake long voyages at sea. Shewing how sea-water may be made fresh and wholsome: and how fresh water may be preserv'd sweet. How biscuit, corn, &c. may be secured from the weevel, meggots, and other insects. And flesh preserv'd in hot climates, by salting animals whole. To which is added, an account of several experiments and observations on chalybeate or steel-waters ... which were read before the Royal-society, at several of their meetings", London: W. Innys and R. Manby
• Biographical information (Dictionary of National Biography, 1890, pages 32–36)
• Parascandola, John and Ihde, Aaron J. (1969). "History of the Pneumatic Trough", Isis, vol. 60, no. 3, pages 351–361
• Stephen Hales at the Galileo Project — details on Hales's life and work

Notes and references