While the cow's mammalian eye is a close parallel to the human eye, it does have some slight differences. Through dissection and examination, students should recognize that the cow's pupil, for example, is oval, while the human pupil is round. They should also notice that cow's irises are always brown, while human irises come in many colors, including blue, brown and green. If students have eye samples with the surrounding muscles intact, they should also be aware that cows can only use four muscles to move their eyes up and down and to the left and right, while humans have six muscles that also allow counterclockwise and clockwise movemen