134 PHYSIOLOGY AND TEMPERANCE. 



12. The Eye-lids. In order that the eyes may serve the 

 body, it is necessary they should be placed in a prominent 

 position, consequently their front parts are more or less 

 exposed. To afford protection to the eyes, and at the same 

 time to shut out the light when too intense, we have the 

 eye-lids. They are folds of skin, to which are attached 

 delicate muscles for moving them up and down. To give 

 firmness to the lids, there is a plate of cartilage in the fold. 

 At the edge of the lids the skin turns in to join the lining 

 membrane. This membrane is called the conjunctiva, because 

 after it has lined the eye-lids for a considerable distance back, 

 it folds on to the eye-ball. It covers the surface of the eye 

 from this point forward. On the cornea it is extremely 

 delicate and transparent. 



The upper eye-lid is larger than the lower, and much more 

 movable. The nerve influence to the eye-lids is wonderful. 

 Their movements are partly voluntary and partly involuntary. 

 We wink continuously while awake. This act, intended to 

 keep the eye moist and free from dust, is involuntary. We 

 can open and shut the eye by a voluntary act when we will, 

 but the flash-like closing of the eye when suddenly threatened 

 is involuntary. The extreme sensitiveness of the exposed 

 parts of the eye is also a protection. Small particles getting 

 into the eye are not allowed to remain there without causing 

 a good deal of pain and irritation. 



The upper and lower lids come together at their two 

 extremities, forming the outer and inner angles of the eye. 

 The space between the two angles varies in different per- 

 sons, and has the effect of making one's eyes appear large 

 or small. 



The eye-lashes are short, curved hairs, arranged in one, two 

 or more rows along the border of the lids. They shade the 

 eye and protect it from tiny insects, dust and other particles 

 of matter floating in the air. Small oil-glands in the margins 



