May 21, 1860 to Sep 29, 1927
Indonesia and NetherlandsWillem Einthoven (21 May 1860 – 29 September 1927) was a Dutch physician and physiologist. He invented the first practical electrocardiogram (ECG or EKG) in 1895 and received the Nobel Prize in Physiology or Medicine in 1924 for it ("for the discovery of the mechanism of the electrocardiogram").
Before Einthoven's time, it was known that the beating of the heart produced electrical currents, but the instruments of the time could not accurately measure this phenomenon without placing electrodes directly on the heart. Beginning in 1901, Einthoven completed a series of prototypes of a string galvanometer. This device used a very thin filament of conductive wire passing between very strong electromagnets. When a current passed through the filament, the magnetic field created by the current would cause the string to move. A light shining on the string would cast a shadow on a moving roll of photographic paper, thus forming a continuous curve showing the movement of the string. The original machine required water cooling for the powerful electromagnets, required five people to operate it and weighed some 270 kilograms. This device increased the sensitivity of the standard galvanometer so that the electrical activity of the heart could be measured despite the insulation of flesh and bones.