Gasser, Herbert Spencer (1888-1963), an American physiologist, carried out research that helped identify the functions of different fibers in the same nerve. He shared the 1944 Nobel Prize in physiology or medicine with American physiologist Joseph Erlanger, a former instructor and then colleague of Gasser's.

In 1922, Gasser and Erlanger succeeded in amplifying the electronic impulse passing through a single nerve fiber. This achievement enabled them to analyze the impulse on a cathode-ray oscilloscope (an instrument for displaying varying electric voltage or current). In 1932, the two scientists discovered that different fibers conduct impulses at different speeds depending on their thickness. Gasser and Erlanger also found that different fibers required a different level of stimulus to form an impulse. This research showed that different kinds of nerve fibers transmit different kinds of impulses, such as pain, pressure, or heat. Their research also furthered our understanding of the mechanisms of pain and reflex action.

Gasser was born in Platteville, Wisconsin. In 1910, he graduated from the University of Wisconsin. After earning an M.A. degree at the same university, he entered the Johns Hopkins Medical School in Baltimore for his clinical studies and, in 1915, received his M.D. degree. He studied pharmacology for a year at Wisconsin and then went to teach at Washington University in St. Louis, Missouri. In 1921, he became professor of pharmacology. Ten years later, he became professor of physiology at Cornell University. From 1935 to 1953, he worked as director of the Rockefeller Institute. He served as coeditor of The Journal of Experimental Medicine.