What are the Most Useless Body Parts?

Third Eyelid 1 of 10

Did you know that you actually have three eyelids?

If you look closely at the inside corner of your eye, you'll see a tiny fold of tissue. This is known as the plica semilunaris. It's the remnant of the third eyelid (or nictating membrane) more commonly found in birds, fish, and reptiles.