It can be drawn across the eye to protect it from dust and keep it moist.
The nictitating membrane is the transparent layer the covers the outside of a frogs eye. Frogs have a so-called Nictitating membrane, which they can slide over their eyes for protection. They do this while jumping and swimming.
The membrane is. SOME problems with it are too.
In mammals (such as your pig) it is vestigial- meaning it most likely has no function but remains because its ancestors used it. It is a remnant of earlier evolution when this eyelid used to be used to help moisten and protect the eyeball.
The nictitating membrane.
Nictitating membrane
Nictitating Membrane
depends on the species.
The nictitating membrane is part of a frog's eye. It is just above the lower lid and acts as a protective third eyelid.
It's called the Nictitating membrane
A nictitating membrane The nictitating membrane is the THIRD eyelid, the SECOND eyelid that you asked about is just that, the eyelid, just like in humans
With the nictitating membrane, which keeps it moist
The color of the nictitating membrane, also known as the third eyelid, varies among different species. In many animals, it can range from translucent to white or pinkish in color.