Biology Reference
In-Depth Information
the seventeenth century, when Kepler, Huygens, Hooke and Newton
entered the stage. The two serious errors had then been dominating
thinking for about two millennia (see Polyak (
1948
) for an excellent
review of the ancient conception of the structure and function of the
visual organ, and also Goethe's (
1810
) historical review).
Nevertheless, the Ancient Greeks, although led far astray in
their thinking about visual information processing, may be seen as the
originators of the scientific study of vision. Indeed, even the roots of
the duplicity theory may be found in their research. Thus, the Ancient
Greeks discovered that the ability to see by day and night differs markedly
between animal species. Empedocles (fifth century BC) attempted to
explain this difference by suggesting that it was due to differences in the
relative amount of 'fire' and 'water' in the inner eye. A relatively small
amount of 'fire' or 'water' produced poor night and day vision, respec-
tively (Goethe,
1810
, pp. 524-525, and p. 530). Similarly, Theophrastus
(the successor of Aristotle at the Lyceum at Athens) suggested that
nocturnal animals may see much better than humans by night due to
more of the 'fire' element in their eyes. Interestingly, he also suggested
that 'fire' from the sun may drastically reduce the amount of 'fire' in the
eye and, thereby, reduce the ability to see by night (Hanssen,
2000
).
1.2 F u r t h e r d e v e l of p m e n t of f t h e d u p l i c i t y
theory
Further progress in our understanding of the differences in visual
processing in day and night vision had to wait for about 2000 years.
Thus, the first modern breakthrough was accomplished by Schultze
(
1866
). Based on comparative histological as well as psychophysical
evidence, he suggested that (1) night and day vision were mediated,
respectively, by rod and cone receptors in the retina, (2) the cones
mediated both achromatic and chromatic sensations, while the
rods mediated achromatic vision only, (3) the rod and cone systems
functioned independently of each other, and (4) the cones provided
for better spatial resolution. (For an evaluation of Schultze's duplicity
theory, see Saugstad & Saugstad (
1959
).)
