American physiologist, who received (with Herbert Gasser (Gasser, Herbert Spencer)) the Nobel Prize for Physiology or Medicine in 1944 for discovering that fibres (axon) within the same nerve cord possess different functions.

Erlanger's research into nerve function was the product of a profitable collaboration with Gasser, one of his students at the University of Wisconsin, Madison (1906–10). Soon after Erlanger's appointment as professor of physiology at Washington University, St. Louis (1910–46), Gasser joined him there, and they began studying ways in which the recently developed field of electronics could be applied to physiological investigations.

By 1922 they were able to amplify the electrical responses of a single nerve fibre and analyze them with a cathode-ray oscilloscope that they had developed. The characteristic wave pattern of an impulse generated in a stimulated nerve fibre, once amplified, could then be seen on the screen and the components of the nerve's response studied.

In 1932 Erlanger and Gasser found that the fibres of a nerve conduct impulses at different rates, depending on the thickness of the fibre, and that each fibre has a different threshold of excitability—i.e., each requires a stimulus of different intensity to create an impulse. They also found that different fibres transmit different kinds of impulses, represented by different types of waves.