Joseph Erlanger shared the 1944 Nobel Prize in Physiology or Medicine with Herbert Gasser for discoveries that fundamentally changed how scientists understood the nervous system. Born on January 5, 1874, in San Francisco to immigrant parents from the German state of Baden, Erlanger studied at the University of California and Johns Hopkins Medical School before joining the faculty at Washington University in St. Louis, where he spent the bulk of his career. The breakthrough came through a creative application of technology. Erlanger and Gasser adapted the cathode ray oscilloscope, originally developed for electronics, to measure the electrical impulses traveling through nerve fibers. The instrument was sensitive enough to detect signals measured in millivolts and milliseconds. What they discovered overturned existing assumptions about neural transmission. Nerve fibers of different thicknesses conducted signals at different speeds. Thick fibers transmitted motor commands rapidly; thin fibers carried pain signals more slowly. This explained why you feel the impact of a stubbed toe before the pain arrives, and why anesthetics could block pain without blocking motor function. The finding provided the first clear, experimentally verified picture of how the nervous system processes different types of sensation and laid the groundwork for modern neurology, pain management, and anesthesiology. Erlanger also contributed important early research on cardiac arrhythmia, developing methods to study the heart's electrical conduction system. He continued working at Washington University until his retirement and died in St. Louis on December 5, 1965, at age 91.