106 CONSCIOUS NERVOUS OPERATIONS 



outer coat is called the sclerotic coat, and forms the " white 

 of the eye." At the back of the eyeball the optic nerve 

 pierces through this coat to reach the retina. Both the 

 cornea and the sclerotic coat on the front of the ball are 

 covered with a thin layer of modified mucous membrane, 

 called the conjunctiva, which is folded back to form the 

 lining of the eyelids. 



Sc 



Fig. 63. Cross section of the eye. 



Sc sclerotic coat. Ch choroid. optic nerve. 



C cornea. / iris. B blind spot. 



con conjunctiva. H retina. 1' yellow spot. 



L lens. A anterior chamber, filled with aqueous humor. 



V posterior chamber, filled with vitreous humor. 



A second coat of the eyeball consists of the choroid, 

 made up largely of blood vessels and loose connective tis- 

 sue, and containing in the inner layers a dark pigment. 

 Just before it passes into the iris which is that part 

 of the choroid forming the colored ring in the front of 

 the eyeball, pierced by the pupil the choroid is laid 



