The _cornea_ is the transparent, bulging, central portion of the eye
covering the pupil and the colored iris. Made of tiny transparent cells
closely packed together, the cornea is not nourished by blood carried to
it by the blood-vessels but by lymph which permeates through it in the
tiny channels between the cells. By its curved surface it plays a part
in focusing rays of light on to the lens situated just behind the iris.
[Illustration: =PICTURE DIAGRAMS SHOWING THE DELICATE STRUCTURE OF THE
EYE AND EAR=]
Directly behind the cornea come the _iris_ and _pupil_. The latter is
nothing more than a hole in the center of the iris through which light
enters the eye.