967. Why do some persons squint?
Because it sometimes happens that a muscle of the eye acts too powerfully for its companion muscle, and draws the eye too much on one side.
968. Why does the pupil of the eye look black?
Because the pupil is an opening through which the rays of light pass into the chamber of the eye. There is, therefore, nothing in the pupil, of the eye to reflect light.
"Keep me as the apple of thine eye; hide me under the shadow of thy wings."—Psalm xvii.
969. Why is the pupil of the eye larger sometimes than at others?
Because the iris, a ring of extremely fine muscles which surround the pupil, contracts when too much light falls upon the retina, and dilates when the light is feeble. It therefore enlarges or diminishes the size of the pupil to regulate the admission of light.