Have you ever seen the glow of an
animal's eyes reflecting the headlights on a car or the
flashlight you are holding? If not, you can try it. You will need:
* a small flashlight * a cat, dog, rabbit or other
mammalian pet.
Take the animal and the
flashlight into a darkened room. It does not have to be totally dark, but the
dimmer the light is, the better. Place your pet on one side of the
room and move to the other side. This may be easier with some pets
than others. Hold the flashlight beside your head, near your eyes
and shine it towards your pet. You will see the animal's eyes
glowing.
Why do its eyes glow? It is
because of something called a tapetum lucidum. This is a shiny layer,
behind the light sensitive cells in the eye. When light enters the
animal's eye, it passes over the light sensitive cells, hits the shiny
surface of the tapetum lucidum and reflects back over the cells a
second time. Each cell gets twice as much stimulation, allowing the
animal to see in much dimmer light.
Interestingly, different animals
have different color eye shine. Cats and dogs usually have green eye
shine. So do deer. Alligators have red eye shine. Opossums eyes shine
pink. In spite of the red eyes that show up in photos, humans do not
have a tapetum lucidum and do not have eye shine. According to my
references, neither do monkeys or birds.
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to Krampf Index Including permission to post
these
experiments on my web site.
