In 1903, in Batavia, Java, Dutch East Indies, Willem Einthoven devised the first string galvanometer. It enabled him to measure electrical action currents (potential differences) of cyclical depolarization and repolarization waves of contracting heart muscle and to record them graphically from the surface of the body. He hypothesized that the heart constitutes an electrical dipole, lying at the center of an equilateral triangle. This hypothesis was supported by R. P. Grant, the father of spatial vector cardiography, but has been proved wrong since. Little did Einthoven know the extent to which his new invention would alter the practice of medicine. Electrocardiography has become an indispensable tool for all clinicians.
Einthoven served as professor of physiology at my alma mater, the Rijksuniversiteit of Leiden in the Netherlands. When he applied his invention to the first actual patient at the Academic Hospital at the edge of the city and laid a cable