Sphygmograph
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The sphygmograph was a mechanical device used to measure blood pressure in the mid-19th century. It was developed in 1854 by German physiologist Karl von Vierordt (1818-1884}. It is considered the first external, non-intrusive device used to estimate blood pressure.
The device was a system of levers hooked to a scale-pan in which weights were placed to determine the amount of external pressure needed to stop blood flow in the radial artery. Although the instrument was cumbersome and its measurements inaccurate, the concept of Vierordt's sphygmograph eventually led to the blood pressure cuff that's used today.
In 1863, Etienne-Jules Marey (1830-1904), improved the device by making it portable, also he used a metallic device applied above the radial artery which magnified and recorded pulse waves. In 1880 Samuel von Basch (1837-1905) invented the sphygmomanometer, which was the first accurate and practical instrument for estimating blood pressure.
