CHAPTER II. 



EYELIDS. 



The eye is protected and covered by two mem- 

 branous, movable curtains — tlie palpebrse — superior 

 and inferior. Tliey serve to protect the eye and to 

 exclude excessive light. Another function is to secrete 

 and distribute a moisture to the eye. Their movements 

 are both voluntary and involuntary, the involuntary 

 due to the orbicularis muscle. The levator palpebrse 

 superioris opens the eyes by lifting the upper lid. The 

 space between the free margins of the lids is the pal- 

 pebral fissure. The angles of junction between the lids 

 are the canthi, the external being the most acute. At 

 the inner canthi are found two small elevations, one on 

 each lid — the lyunctum lachrymale — which are the be- 

 ginnings of the canals, or canaliculi., letiding to the tear 

 sac. The eyelids are composed of four layers : (1) the in- 

 tegument, (2) layer of muscular fibers, (3) the tarsus, and 

 (4) the conjunctiva. The muscular fibers consist of the 

 orbicularis palpebrarum, a wide, thin sphincter common 

 to both lids, having tendinous attachments at the angles 



of the lids, the tendons together with some muscle- 

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