Haldan Keffer Hartline

Did You Know?

• Hartline began his study of retinal electrophysiology as a National Research Council Fellow at Johns Hopkins School of Medicine.
• He was elected to the United States National Academy of Sciences in 1948.
• He was elected a Foreign Member of the Royal Society in 1966.

Scientific career

After studying at Leipzig University and the Ludwig-Maximilians-Universität München as an Eldridge Johnson traveling research scholar from the University of Pennsylvania, Hartline returned to the United States to join the Eldridge Reeves Johnson Foundation for Medical Physics at Penn, then directed by Detlev W. Bronk. He served as Associate Professor of Physiology at Cornell Medical College in 1940–1941, then returned to Penn until 1949. That year he became professor of biophysics and chairman of the Jenkins Department of Biophysics at Johns Hopkins University. One of his graduate students at Johns Hopkins, Paul Greengard, also won the Nobel Prize. In 1953 Hartline joined Rockefeller University as professor of neurophysiology. He investigated the electrical responses of retinas of arthropods, vertebrates, and mollusks, focusing on the horseshoe crab (Limulus polyphemus). Using minute electrodes, he obtained the first record of electrical impulses from a single optic nerve fibre when its receptors were stimulated by light. He found that photoreceptor cells interconnect so that stimulation of one depresses nearby cells, enhancing contrast and sharpening shape perception. Hartline built a detailed understanding of individual photoreceptors and nerve fibres, showing how simple retinal mechanisms integrate visual information.