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Re: red eye



Further to the "red eye" discussion -- The book "From Cell to Organism"
(Reprints from Scientific American) has two pictures of alligators, one
with colourless eyes, the other with red eyes. From the book:

"Eye of the alligator, which has a white reflecting layer behind the
retina, illustrates how rhodopsin bleaches in the light and regenerates in
the dark. The eye of the alligator above is light adapted; the light of a
stroboscopic-flash lamp, reflected from the white layer through the
retina, is essentially colourless. The eyes of the alligator below are
dark-adapted; the light reflected is red."

The picture of the alligator with unbleached rhodopsin (aka "visual
purple," which sensitizes the retina for night vision) looks remarkably
like those of people with red-eye, except the teeth are a bit more pointy.
Perhaps part of the phenomenon of red eye is due to the presence of
rhodopsin in dark-adapted eyes.

Michael Porter
Gloucester High School
Gloucester, Ontario, Canada
mporter@ccs.carleton.ca