226 THE EYEBALL. 



into it. To the inner or deeper side of the eyeball is 

 attached the optic nerve, 17, which runs to the brain, 

 and is the nerve of sight. 



5. The Eyeball has Three Coats, an outer, a middle, and 

 an inner. 



The outer coat is tough and strong: on the back and 



FIG. 55. The left eyeball in horizontal section, i, sclerotic; 2, junction of 

 sclerotic and cornea; 3, cornea; 10, choroid; 14, iris; 15, retina; 17, optic nerve; 

 26, 27, 28, are placed on the lens ; 29, vitreous humor ; 30, aqueous humor. 



sides of the eyeball it is opaque, that is to say, does not 

 let light go through it. A little of it can be seen be- 

 tween the eyelids, as the " white of the eye." The opaque 

 part of the outer coat is named the sclerotic (i, Fig. 55). 



on its front ? Where does the optic nerve join it ? Where does the 

 nerve go? Function of this nerve? 



5. What coats has the eyeball ? Nature of the outer. Describe the 

 sclerotic- The cornea, The choroid. The iris. The pupil. Why 



