Stephen HalesBorn 17 Sep 1677; died 4 Jan 1761 at age 83. English botanist, chemist and physiologist who pioneered the quantitative experimental approach in plant and animal physiology. He was a clergyman whose work in plant physiology, Vegetable Staticks (1787), included early demonstrations of the importance of air and light in plant growth, and of the role of transpiration in causing upward sap flow. He also measured the rates of growth of shoots and leaves and the pressure roots exert on sap, and he investigated plant respiration. Hales was the first to quantitatively measure blood pressure, measured the capacity of the left ventricle of the heart, and the output of the heart per minute. He invented an artificial ventilator that could convey fresh air into prisons, ships' holds, and granaries.[DSB gives date of birth as 17 Sep 1677. EB gives 7/17 Sep 1677.] |
