Stephen Hales

Stephen Hales

Portrait of Stephen Hales

Born	17 September 1677
Birth place	Bekesbourne, Kent, England
Died	4 January 1761
Place of death	Teddington, Middlesex, England
Nationality	British
Known for	Measuring blood pressure, plant physiology

Stephen Hales (17 September 1677 – 4 January 1761) was an English clergyman who made significant contributions to a variety of scientific fields, including physiology, botany, and chemistry. He is best known for his pioneering work in measuring blood pressure and for his studies on plant physiology.

Early Life and Education

Stephen Hales was born in Bekesbourne, Kent, England. He was the sixth son of Thomas Hales, a wealthy landowner. Hales was educated at Corpus Christi College, Cambridge, where he initially studied theology. However, his interests soon turned to the natural sciences, and he began conducting experiments in botany and physiology.

Contributions to Physiology

Hales is perhaps most famous for his work in physiology, particularly his experiments on blood pressure. In 1733, he published "Statical Essays: Containing Haemastaticks," in which he described his method of measuring blood pressure in animals. Hales inserted a glass tube into the artery of a horse and observed the rise of blood in the tube, thus providing the first recorded measurement of blood pressure. This work laid the foundation for modern cardiology and the study of hemodynamics.

Contributions to Botany

In addition to his work in physiology, Hales made significant contributions to the field of botany. He conducted experiments on plant transpiration and water uptake, demonstrating that plants absorb water through their roots and lose it through their leaves. His work "Vegetable Staticks" (1727) detailed these experiments and introduced the concept of "root pressure," which explained how water moves through plants. Hales' research in this area helped establish the field of plant physiology.

Contributions to Chemistry

Hales also made contributions to chemistry, particularly in the study of gases. He developed a method for collecting gases over water, which was an important technique for later chemists. His work in this area contributed to the understanding of the properties of gases and laid the groundwork for future discoveries in chemistry.

Legacy

Stephen Hales' work had a lasting impact on multiple scientific disciplines. His innovative methods and careful experimentation set new standards for scientific research. Hales was elected a Fellow of the Royal Society in 1718, and he was awarded the Copley Medal in 1739 for his contributions to science.

Also see

• Blood pressure
• Plant physiology
• Cardiology
• Royal Society
• Copley Medal