World of Scientific Discovery on Haldan Keffer Hartline
Haldan Keffer Hartline was born on December 22, 1903, in Bloomsburg, Pennsylvania, to Daniel Schollenberger Hartline and Harriet Franklin Hartline. He attended college at Lafayette College in Easton, Pennsylvania, graduating with a B.S. in 1923. He went on to study retinal electrophysiology as a graduate student at Johns Hopkins University, obtaining his M.D. in 1927. Hartline spent the next two years at Johns Hopkins University as a National Research Council fellow in medical sciences.
Between 1929 and 1931, Hartline was a Johnson Traveling Research Scholar from the University of Pennsylvania to the universities of Leipzig and Munich. He travelled extensively in Germany during those years before returning to the United States, where he joined the Eldridge Reeves Johnson Research Foundation for Medical Physics as an assistant professor of biophysics at the University of Pennsylvania. Hartline married Mary Elizabeth Kraus on April 11, 1936. They had three sons: Daniel Keffer, Peter Haldan, and Frederick Flanders.
From the early days of his career, Hartline was fascinated by the metabolism of nerve cells, and he eventually focused his attention on the workings of individual cells in the retina of the eye. During the late 1920s and early 1930s, Hartline used recently-developed methods of fiber isolation to record the activity of single nerve fibers in the retina. He began by experimenting with Limulus Polyphemus, the horseshoe crab. He chose this primitive creature because it possessed a feature that was ideal for his research: a compound eye with a long optic nerve and large individual photoreceptors. It seemed to Hartline that working with the horseshoe crab might allow him to record the electrical behavior of single nerve fibers. He succeeded in 1932, while working at the Eldridge Reeves Johnson Foundation. Hartline and Columbia University psychophysiologist Clarence H. Graham managed to isolate single nerve fibers from the optic nerve, placed electrodes on those single fibers, stimulated them with light, and recorded the nerve impulses that occurred. This was the first record of the activity of a single optic nerve fiber, and it proved to Hartline and Graham that their theories had been correct: information is relayed through individual optic nerve fibers by a series of uniform nerve impulses.
Hartline moved into another field of vision in 1938, when he began to study the vertebrate eye, using microdissection techniques to record the activity of individual fibers in the optic nerve of frogs. While recording the nerve impulses from the single nerve fibers lying behind the rods and cones of the eye, he found that the fibers making up the nerve did not all behave in the same way. Some were stimulated by steady light, others were stimulated by the light when it first hit the retina, and still others were stimulated only as the light was shut off. Hartline demonstrated that visual information begins to be differentiated in the retina and in the receptors themselves, as soon as the stimulation occurs, before the information can be conducted more deeply into the central nervous system. This research afforded new insights into the working of the retina. It also provided a new understanding of how the mechanisms of vision were integrated with, and how they affected, the nervous system as a whole. For this discovery, Hartline was awarded the Howard Crosby Warren Medal of the Society of Experimental Psychologists in 1948.
Hartline continued his teaching and research at the University of Pennsylvania, becoming professor of biophysics and chair of the department at Johns Hopkins in 1949. In 1953, Hartline joined the faculty of Rockefeller University in New York as professor of neurophysiology. There, Hartline began investigating the phenomenon of inhibition in the retina of the compound eye, using the horseshoe crab as a subject once again. He and his colleague, Floyd Ratliff, demonstrated the electrical response of nerve fibers and cells to light hitting the retina, and the mechanism by which this response allows the eye to differentiate shapes. He found that the receptor cells in the eye are interconnected in such a way that when one is stimulated, others nearby are depressed, thus sharpening the contrast in light patterns. In the 1960s, Hartline extended these studies to the dynamics of the receptors and their interactions, with a view to understanding visual phenomena such as motion detection. Hartline's findings eventually led to the development of a set of mathematical equations expressing the interrelationship of the receptor units of the compound eye; this information has been key to understanding brightness and contrast in the retinal image.
For his work on electrical activity on the cellular level within the eye, Hartline shared the 1967 Nobel Prize for physiology or medicine with the American biologist George Wald and the Swedish neurophysiologist Ragnar Granit. This was not the only award received by Hartline during this period; he also received the A. A. Michelson Award of Case Institute, 1964, and the Lighthouse Award in 1969. In addition to the Nobel Prize and the other awards and honors received during his lifetime, Hartline was also presented with a number of honorary degrees. He was awarded doctorates from Lafayette College in 1959, the University of Pennsylvania in 1971, Rockefeller University in 1976, the University of Maryland in 1978, and Syracuse University in 1979; an LL.D. from Johns Hopkins University in 1971; and an M.D. from the University of Freiburg in 1971.
Hartline was a member of many important scientific organizations, many of them elective. He was elected to the National Academy of Sciences in 1948, and to the American Academy of Arts and Sciences in 1957. Hartline also held memberships in the American Philosophical Society and the Biophysics Society, and in 1966 was elected a foreign member of the Royal Society, London. The Optical Society of America made him an honorary member, as did the Physiology Society (U.K.).
Hartline died on on March 17, 1983, in Fallston, Maryland.
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