Haldan Keffer Hartline

ForMemRS^[1] (December 22, 1903 – March 17, 1983) was an American physiologist who was a co-recipient (with George Wald and Ragnar Granit) of the 1967 Nobel Prize in Physiology or Medicine^{[2][3][4][5][6][7][8]} for his work in analyzing the neurophysiological mechanisms of vision.^[9]

Leipzig and Munich as an Eldridge Johnson traveling research scholar from the University of Pennsylvania, he returned to the US to take a position in the Eldridge Reeves Johnson Foundation for Medical Physics at Penn, which was under the directorship of Detlev W. Bronk at that time. In 1940–1941, he was Associate Professor of Physiology at Cornell Medical College in New York City but returned to Penn and stayed until 1949. Then he became professor of biophysics and chairman of the Jenkins Department of Biophysics at Johns Hopkins University in 1949. One of Hartline's graduate students at Johns Hopkins, Paul Greengard, also won the Nobel Prize. Hartline joined the staff of Rockefeller University, New York City, in 1953 as professor of neurophysiology.^{[citation needed}

mollusks, because their visual systems are much simpler than those of humans and thus easier to study. He concentrated his studies on the eye of the horseshoe crab (Limulus polyphemus). Using minute electrodes, he obtained the first record of the electrical impulses sent by a single optic nerve fibre when the receptors connected to it are stimulated by light. He found that the photoreceptor cells in the eye are interconnected in such a way that when one is stimulated, others nearby are depressed, thus enhancing the contrast in light patterns and sharpening the perception of shapes. Hartline thus built up a detailed understanding of the workings of individual photoreceptors and nerve fibres in the retina, and he showed how simple retinal mechanisms constitute vital steps in the integration of visual information.^{[citation needed}

Foreign Member of the Royal Society (ForMemRS) in 1966.^[1] He was awarded the Nobel Prize in Physiology or Medicine in 1967.^[13][14]