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 eye (Fig. 121). The opening of one of the canals may be seen by looking into a mirror. Sometimes these canals are stopped up, and what is called a "weeping eye" results. A temporary stoppage may occur during a cold in the head.

Tears prevent friction between eye and lid. Winking applies the tears to the ball. Small glands along the edges of the lids form a kind of oil which usually prevents the tears from flowing over the lids. Sometimes this oily secretion is so abundant, especially during sleep, as to cause the lids to stick together. The mucous membrane of the eyelids continues as a transparent membrane (the conjunctiva) which passes over the front of the ball.

The globe of the eye consists of its outer wall and the soft contents (Fig. 122). The wall has three layers or coats. The outer coat is the tough sclerotic (Greek, skleros, hard), composed of dense connective tissue (Exp. 14). It gives strength and firmness to the eyeball. It shows between the lids as the "white of the eye." It is white and opaque except in front; there it bulges out to form the transparent cornea. This clear portion of the wall may be seen by looking at the eye of another from the side.

The second coat, called the choroid, consists of blood