EYELIDS. TEARS. 231 



sewing in such feeble light that the eyes feel strained, 

 will certainly injure them permanently. 



Long-sight and short-sight are not diseases. They 

 are due to the fact that the eyeball is not perfectly 

 shaped, but it may, nevertheless, be perfectly healthy. 

 Both defects are easily remedied by proper spectacles 

 or eye-glasses. If neglected, they lead not only to dis- 

 ease of the eye itself, but to headaches, and other 

 symptoms of nervous disorder. 



10. The Eyelids are folds of skin moved by muscles 

 so as to cover or uncover the front of the eyeball, or, as 

 we ordinarily say, to shut or open the eye. Opening 

 along the edge of each eyelid, are twenty or thirty small 

 glands. Their secretion is greasy and keeps the tears 

 from flowing over the edge of the eyelids, except when 

 they are secreted in large quantity. The eyelid-secre- 

 tion is sometimes too abundant, and then appears as a 

 yellowish matter along the edges of the eyelid. It often 

 dries during the night and causes the lids to be glued 

 together in the morning. 



11. Tears are secreted by the tear or lachrymal glands, 

 which lie, one in each eye-socket, above and to the outer 

 side of the eyeball. They are poured on the front of the 

 eye by the tear-ducts which open on the deeper or inner 

 side of the upper eyelid, near its outer corner. Tears 

 are secreted all the time, but usually only in small 

 quantity. Winking spreads them all over the front of 



darkness to bright light? How may short sight or long-sight be 

 remedied ? What happens if they are neglected ? 



10. What are the eyelids ? What open along their edges? Use of 

 these glands ? Why are the eyelids sometimes glued together in the 

 morning? 



11. Where are the tear-glands? Where do these ducts open? How 



