So, what was a third eyelid doing in a human? Most refer to such bits of tissue as vestigial. The word means a structure that ...

Our pets, like dogs and cats, have a third eyelid known as the nictitating membrane. This thin, moist membrane protects the ...

2. Cats Have a Third EyelidCats possess a third eyelid, called the nictitating membrane, located at the inner corner of their eyes. This transparent eyelid moves horizontally and provides ...