Herbert Spencer Gasser (1888-1963) deserves to be remembered for introducing the oscilloscope into biology and medicine; with a prototype still in the early stages of development he overcame the evanescent nature of the nerve impulse and thus opened the way to the study of cellular electrical potentials in the nervous system. In tracing the origins of the cortical extracellular currents reflected in the waves of the scalp electroencephalogram the oscilloscope has been indispensable.

The graphic methods developed in the nineteenth century were adequate (indeed, admirable) for recording events that were measured in seconds but even the Einthoven string galvanometer that conquered millivolt changes was defeated when the unit on the time scale was the millisecond. The stream of electrons from the cathode in an evacuated (Crookes) tube, which incidentally excited X-rays in Roentgen's tube and served for amplification purposes in the thermionic valve, provided the answer. Progressive refinement of Karl Ferdinand Braun's (1850-1918) original 1897 invention into the cathode ray oscilloscope had the versatility required to follow biological processes that had previously been inaccessible because of the exceeding brevity of their duration. The realisation that the oscilloscope would capture fleeting clinical and experimental events we owe to Herbert Gasser.

Herbert Spencer Gasser was born on 5 July 1888 in the small Wisconsin town of Platteville. After local schooling he entered the nascent medical school of the University of Wisconsin at Madison where Joseph Erlanger (1874-1965) had just set up the department of physiology. After completing his clinical under-graduate course at Johns Hopkins Medical School in 1915 Gasser returned for a year to Madison before rejoining Erlanger who had moved in 1910 to Washington University in St. Louis.