CHAPTER XXVIII 

 THE EYE 



THE eye may be said to consist of the visual organ, or globe, 

 together with its appendages the eyelids, conjunctiva, and lachry- 

 mal apparatus whose function is chiefly protective. 



The globe of the eye, or eye proper, is contained within the 

 cavity of the orbit, its posterior two-thirds being embedded in a 

 mass of intraorbital fat whose inner surface is covered by a thin 

 fibrous membrane or fascia which is clothed with endothelium. 

 The endothelium is reflected from this fascia to the surface of 

 the ocular globe, along a line just posterior to the border of the 

 conjunctiva, whence it passes over the surface of the globe as far 

 posteriorly as the optic nerve, on the surface of which it again be- 

 comes continuous with the endothelium of the fascia. Thus a 

 serous sac or lymphatic space is formed by the parietal layer of this 

 sac, which lines the orbital cavity, in conjunction with the visceral 

 layer which covers the posterior two-thirds of the globe of the eye ; 

 this sac is the capsule of Tenon. 



The anterior third of the globe is covered by the palpebral por- 

 tion of the conjunctiva, which also clothes the inner surface of the 

 eyelids, and at the fornix conjunctivas is reflected upon the eye- 

 ball a little in front of its equator, whence it is continued forward, 

 as the ocular or scleral conjunctiva, as far as the margin of the 

 eye ; here it becomes continuous with the anterior corneal epi- 

 thelium. 



The globe of the eye or eyeball is a spheroidal body whose surface 

 consists of three coats, an outer, middle, and inner, and whose con- 

 tents are the vitreous and aqueous humors and the crystalline lens. 



The eyeball is not a true sphere, but may be said to comprise 

 segments of two spheres, the smaller of which is inserted into the 

 anterior surface of the larger. The anterior or smaller segment 

 consists chiefly of transparent tissues which permit the entrance of 

 light. Its border nearly corresponds to the posterior margin of the 



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