456 



THE SPECIAL SENSES 



white coat known as the white of the eye or sclerotic coat. 

 In this layer are the blood vessels which supply the coat with 



C.P. 



Pig. 215 — Section of the eyeball; ^c, sclerotic coat; Con^ conjunctiva; C, cornea; 

 /, iris; 0, optic nerve; CA, choroid layer; CP, ciliary processes; Cm, ciliary 

 muscles and ligament; Ji, retina; L, crystalline lens; A, aqueous humor; Vt 

 vitreous humor. 



nourishment. At the front this layer is replaced by the 

 transparent layer of mucous membrane (the infolded con- 

 junctiva) and a transparent modification of the white of the 

 eye called the cornea. Back of this cornea is a colored, 

 circular, muscular curtain called the iris. 



If we split the eyeball vertically so as to split the optic 

 nerve it shows the following internal structure. The 

 conjunctiva in front folded back from the eyelids. . Over. 

 the whole surface, and covering the outside of the opticl 

 nerve, is the sclerotic layer just mentioned, with its trans- 

 parent window or cornea in the front. Inside the sclerotiQ 



