Nictitating membrane

Definition (http://en.wikipedia.org/wiki/Nictitating_membrane)

The nictitating membrane (from Latin nictare, to blink) is a transparent or translucent third eyelid present in some animals that can be drawn across the eye for protection and to moisten it while maintaining visibility. Some reptiles, birds, and sharks have full nictitating membranes; in many mammals, a small, vestigial portion of the membrane remains in the corner of the eye. Some mammals, such as camels, polar bears, seals and aardvarks, have full nictitating membranes. (Wikipedia)

Preferred Units: N/A

Scope Note:
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This term is used for the following terms: 
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Approved Date
05-Apr-2013

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