27.9 MB (9.8 MB compressed)
2892 x 3366 pixels
24.4 x 28.4 cm ⏐ 9.6 x 11.2 in (300dpi)
COLLECTION ABECASIS / SCIENCE PHOTO LIBRARY COLLECTION ABECASIS / SCIENCE PHOTO LIBRARY
19th Century sphygmograph. 1881 illustration showing a man using a sphygmograph. This mechanical device was developed by the German physiologist Karl von Vierordt (1818-1884) to measure blood pressure and was the first external, non-intrusive device to do so. It used a system of levers attached to a weighing scale pan in which weights were placed in order to measure the amount of external pressure needed to stop blood flow in the radial artery. The device was cumbersome and inaccurate but led to the design of the modern blood pressure cuff still used today.
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