Willem Einthoven

Einthoven, Willem (1860–1927), Dutch physiologist, awarded the 1924 Nobel Prize for physiology or medicine for his invention of, and investigation of heart action with, the electrocardiograph. In 1903 he devised the string galvanometer, a single fine wire placed under tension in a magnetic field. Current passed through the wire causes a deflection that can be measured, for greater accuracy, by a microscope. This galvanometer was sensitive enough for him to use it to record the electrical activity of the heart.