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The black eye patch was used by pirates to quickly get used to a change of lighting
Actually, not only pirates were those bandages. Any sailor who had often visited the hold, wearing a bandage on the eye. The reason was that the ocean, lit by sunlight, blinded eyes, but in the holds was very dark. In order not to waste time to get used to the change of light eyes, one eye sailors were kept in constant darkness, and going down into the hold, opened it and immediately saw well. That's the whole trick.
via factroom.ru
There are "forbidden colors", for example, red-green and yellow-blue
In hagfish 4 hearts, 2 of the brain, one nostril is the skull, but no spine