The Nictitating Membrane: The Third Eyelid

From the picture above you could easily imagine that the animal kingdom had suddenly been enveloped in its own zombie apocalypse.  Yet this is not a still from a forthcoming episode of The Squawking Dead. Thanks to high speed photography, these photographs capture the nictitating membrane in action. It is also known as the third eyelid, haw and the inner eyelid. It is drawn across the eye to protect and moisturize it while retaining visibility. The Ark in Space today has a feature on this extraordinary structure of the eye.

Image Credit Flickr User Simon