“A basic characteristic of the scientific enterprise is its continuity. It is an organic growth, to which each worker in his time brings what he can; like Chartres or Hagia Sofia, to which over the centuries a buttress was added here, a tower there.” George Wald, Nobel lecture, 1967
In 1967 the Harvard University professor George Wald shared, with two other scientists, the Nobel Prize in Physiology or Medicine for his “discoveries concerning the primary physiological and chemical visual processes in the eye.” Wald inherited from his teacher, Selig Hecht, a universalist theory of light sensitive photochemistry. This universalist theory stipulated that the biochemical mechanisms of light sensitivity were conserved across animals. Hecht, and then Wald, argued that any organism that is sensitive to light uses the same biochemical mechanisms to do so.
In order to appreciate their contributions to the field, we must first understand the research tradition of Hecht and Wald and introduce some of the problems in the world that motivated their research, and to which they offered successful answers. First, the ‘duplicity theory’ of human vision, which is covered in Section 1, is motivated by a phenomenon called the Purkinje shift. In low light, color sensitivity decreases, shifting the perceivable colors towards the red end of the light spectrum during dark adaptation and making blue-end visual spectra disappear rapidly in low light until fully achromatic night vision takes over. The question then is, are there two systems of vision, one achromatic and for night/dark vision, the other for chromatic and for day/light vision? Or is there one system that handles both sensory settings? Duplicity theorists insist that the Purkinje shift (that is, the fact that night vision is achromatic and slowly takes over for day vision when light levels drop) is evidence that there are two systems, served by different photopigments in the retina.
In addition to the problem of light and dark adaptation, photochemical theories of vision need to solve the problem of how one photopigment could possible be infinitely exposable. The idea that the eye works like a kind of biochemical camera motivated scientists to wonder about just how the eye never never runs out of exposable film, so to speak. The eyes 'film' is composed of photopigments. Kühne and Boll, two figures we will meet shortly, demonstrated that photopigments regenerate after multiple episodes of bleaching from light exposure. But how exactly that process worked was a mystery until first Hecht and then Wald filled in the theoretical and molecular details.
Note: There is no science without a scientist, and so the author has attempted to maintain the essential truth of that—namely that at each stage of the scientific process there is a person looking at evidence and making judgments. However there is almost no personal biography, and much of the professional biography of each author has been abridged dramatically. In spite of this, the reader should keep in mind that each of these individuals were complicated people who share at least a job description. George Wald once said, “A scientist should be the happiest of men. Not that science isn't serious; but as everyone knows, being serious is one way of being happy, just as being gay is one way of being unhappy”. Each of these individuals had a scientific ethic, as well as a body of scientific work, and where possible, the author of each section has attempted to not forget the romanticism of the spirit of investigation, or the fact that many of these people were excited by a simple truth—after all, they were seeing things no one else had seen before. That majesty can be easy to forget if you are an outsider new to the complexities of visual physiology, but these scientists never forgot it.
Bibliography
Universalizing Photochemical Theories of Vision: Hecht, Wald, and the Marine Biological Laboratory
- Applebury, Meredith. "Establishing the Molecular Basis of Vision: Hecht and Wald." In The Biological Century, by Robert Barlow, John Dowling and Gerald Weissmann, 175-202. Cambridge, Massachusetts: Harvard University Press, 1993.
- In The Biological Century, by Robert Barlow, John Dowling and Gerald Weissmann. Woods Hole, Massachusetts: The Marine Biological Laboratory, 1993.
- Boll, Franz. "Zur Anatomie und Physiologie der Retina (on the anatomy and physiology of the retina)." Monatsberichte der Königlich Preussischen Akademie der Wissenschaften zu Berlin, Akademie der Wissenschaften (Monthly reports of the Royal Prussian Academy of Sciences in Berlin), 1877: 783-788.
- Boll, Franz. "Zur Physiologie des Sehens und der Farbenempfindung (the physiology of vision and color perception)." Monatsberichte der Königlich Preussischen Akademie der Wissenschaften zu Berlin (Monthly reports of the Royal Prussian Academy of Sciences, 1878: 2-7.
- Dowling, John. "George Wald 1906-1997, A Biographical Memoir." National Academy of Sciences 78, no. Biographical Memoirs (2000).
- Gregory, Richard L. Eye and Brain: the psychology of seeing. Fourth Edition. Princeton, New Jersey: Princeton University Press, 1990.
- Hecht, Selig. "Intensity and the process of photoreception." Journal of General Physiology 2 (1919/1920): 337-347.
- Hecht, Selig. "Rods, cones, and the chemical basis of vision." Physiological Review 17 (1937): 239-290.
- Hecht, Selig. "The dark adaptation of the human eye." Journal of General Physiology 2 (1919/1920): 499-517.
- Hecht, Selig. "The nature of foveal dark adaptation." Journal of General Physiology 4 (1921/1922): 113-139.
- Hecht, Selig. "The photochemical nature of the photosensory process." Journal of General Physiology, 2 (1919/1920): 229-246.
- Hecht, Selig, C. Haig, and George Wald. "The dark adaptation of retinal fields of different size and location." Journal of General Physiology 19 (1935/1936): 321-337.
- Helmholtz, Hermann von. Handbuch der Physiologischen Optik (handbook of physiological optics. Leipzig: Voss, 1867.
- Kühne, Wilhelm. "Chemische Vorgänge in der Netzhaut (Chemical Processes in the Retina)." In Handbuch der Physiologie (Handbook of Physiology), 235-342. Leipzig: F.C.W. Vogel, 1880.
- —. Ueber den Sehpurpur (about the visual purple). Heidelberg: Untersuehungen aus dem physiologischen institute der universität Heidelberg (from the physiological institute of the univeristy of Heidelberg)., 1877-1878.
- Müller, George Ellias. "Über die Farbenempfindungen (about color sensations)." Zeitschrift für Psychologie und Physiologie der Sinnesorgane (journal of psychology and physiology of the sense organs) Ergänzungsband (supplement) (1930): 1-434.
- Müller, George Ellias. "Zur Psychophysik der Gesichtsempfindungen (Towards a psychophysics of visual sensations)." Zeitschrift für Psychologie und Physiologie der Sinnesorgane (Journal of psychology and physiology of the sense organs, 1896: 321-413.
- Marr, David. Vision. New York, NY: W.H. Freeman and Company , 1982.
- Schultze, Max Johann Sigismund. "Zur Anatomie und Physiologie der Retina (The Anatomy and Physiology of the Retina)." Archiv für mikroskopische Anatomie (Archive for microscopic anatomy). 2 (1866): 175-286.
- Stabell, Bjørn, and Ulf Stabell. Duplicity Theory of Vision. Cambridge, Massachusetts: Cambridge University Press, 2009.
- Wald, George. "Selig Hecht 1892-1947." National Academy of Science, 1991.
- Wald, George. "The molecular basis of visual excitation." Nobel Lecture, December 1967.
- Wald, George. "The photochemistry of vision." Documenta Ophthalmologica 3 (1949): 94-137.
- Wald, George. "The porphyropsin visual system." Journal of General Physiology 22 (1938/1939): 775-794.
- Wald, George. "Visual purple system in fresh-water fishes." Nature 139 (1937): 1017-1018.
- Wald, George. "Vitamin A in the retina." Nature, no. 132 (1933): 316-317.
- Wald, George. "On the mechanism of the visual threshold and visual adaptation." Science 119 (1954): 887-892.
- Young, Thomas. "The Bakerian Lecture: On the theory of light and colours." Philosophical Transactions of the Royal Society of London 92 (1802): 12-48.
Haldan Keffer Hartline, a Prize, and Two Accidents
- Bang, Frederick. "A bacterial disease of limulus polyphemus." The Marine Biological Laboratories, Woods Hole, Massachusetts, and the Department of Pathobiology, School of Hygiene and Public Health, The Johns Hopkins University, 1955.
- Barlow, Robert. "From string galvanometer to computer: Haldan Keffer Hartline (1903–1983)." Trends in Neuroscience 9 (1986).
- Graham, C.H., and Haldan Keffer Hartline. "The response of single visual sense cells to lights of different wave lengths." Journal of General Physiology, 1935: 917-931.
- Grant, R, and F Ratliff. "Haldan Keffer Hartline." Biographical Memoirs of Fellows of the Royal Society (The Royal Society) 31 (Nov 1985): 262-292.
- Hartline, Haldan Keffer. "Influence of light of very low intensity on phototropic reactions of animals." Journal of General Physiology 6, no. 2 (1923): 137-152.
- Hartline, Haldan Keffer. "Inhbition in the eye of limulus." Journal of General Physiology 39, no. 5 (1956).
- Hartline, Haldan Keffer. "intensity and duration in the excitation of single photoreceptor units." Journal of Cellular and Comparative Physiology, 1934: 229-247.
- Hartline, Haldan Keffer. "The dark adaptation of the eye of Limulus, as manifested by its electric response to illumination." Journal of General Physiology 13, no. 3 (1930).
- Hartline, Haldan Keffer. "Visual receptors and the retinal interaction." Nobel Lecture, December 1967.
- Hartline, Haldan Keffer, and Floyd Ratliff. "Inhibitory interaction of receptor units in the eye of Limulus." Journal of General Physiology, 1957: 357-376.
- Hartline, Haldan Keffer, and Floyd Ratliff. "Spatial summation of inhibitory influences in the eye of Limulus, and the mutual interaction of receptor units." Journal of General Physiology, May 1958: 1049-1066.
- Madrigal, Alexis. "The Blood Harvest." The Atlantic, Feb 26, 2014.
- Nobelprize.org. Haldan K. Hartline - Biographical. Nobel Media AB 2014. 1967. http://www.nobelprize.org/nobel_prizes/medicine/laureates/1967/hartline-bio.html (accessed 2015 14, 2015).
- Ratliff, Floyd. "Haldan Keffer Hartline 1903-1983." National Academy of Sciences, 1990.
- Shuster, Carl N, Robert B Barlow, and H Jane Brockmann. The American Horseshoe Crab. Cambridge, Massachusetts: Harvard University Press, 2003.
Roger Hanlon, Universal Camouflage, and Studying Vision at the MBL in the 21st Century
- Allen, J.J., L.M. Mäthger, A. Barbosa, and R.T. Hanlon. "Cuttlefish use visual cues to control 3-dimensional skin papillae for camouflage." Journal of Comparative Physiology, 2009: 547-555.
- Chiaoa, Chuan-Chin, J. Kenneth Wickiser, Justine J. Allen, Brock Genter, and Roger T. Hanlon. "Hyperspectral imaging of cuttlefish camouflage indicates good color match in the eyes of fish predators." PNAS 108, no. 22 (May 2011): 9148-9153.
- Hanlon, Roger. "Cephalopod dynamic camouflage." Current biology , 2007: 400-404.
- Hanlon, Roger. Rapid adaptive camouflage and signaling in cephalopods. PART I: Concepts and questions. Performed by Roger Hanlon. iBiology.org. 2011.
- MBL. Hanlon lab - overview. 2011. http://www.mbl.edu/bell/current-faculty/hanlon/.
- Ulmer, K.M., K.C. Buresch, M.M. Kossodo, L.M. Mäthger, L.A. Siemann, and R.T. Hanlon. " Vertical Visual Features Have a Strong Influence on Cuttlefish Camouflage ." Biological Bulletin 224, no. 2 (2013): 110-118.
- Zimmer, Carl. "Cuttlefish camouflage." New York Times, February 13, 2008: http://www.nytimes.com/video/science/1194817111131/cuttlefish-camouflage.html.