Although trained in medicine, Willem Einthoven was always very much interested in physics, and his greatest contributions to science involve the application of physical principles to the development of new instruments and techniques in physiological studies. One such instrument, the string galvanometer, made possible the first valid and reliable electrocardiogram, thereby providing physicians with one of their most valuable tools for the study of cardiovascular disorders. For his invention of the string galvanometer, Einthoven was awarded the Nobel Prize for Physiology or Medicine in 1924.

Einthoven was born on May 21, 1860, in Semarang, Java, in what was then the Dutch East Indies and is now Indonesia. His father, Jacob Einthoven, was a physician in Semarang. When Jacob died in 1866, his wife, Louise M. M. C. de Vogel, returned to her native Holland with her six children, Willem included. The family settled in Utrecht, where young Willem attended local grammar and...