STRUCTURE OP THE EYE. 383 



tween the back of the lens and the retina is filled with a substance ex- 

 tremely transparent, and known as the vitreous humor. The aqueous 

 humor, the crystalline lens, and the vitreous humor, by reason of their 

 transparency, offer, therefore, no obstacle to the passage of light. 



ILLUSTRATIONS OF THE EYE. 



Fig. 196 : #, a, sclerotic, turned over ; &, choroid ; c, <?, ciliary nerves 

 traversing sclerotic, and going between it and choroid ; d, retina ; 0, vit- 

 reous body ; f, crystalline ; g, middle section of iris ; A, middle section 

 of cornea ; i t anterior chamber ; j 9 posterior chamber ; &, canal of Fonta- 

 196. na, between the ciliary circle and iris 



on one side, and sclerotic and cornea on 

 the other. 



Fig. 197. 



Profile view of the eye. Front view of the eye. 



Fig. 197 : <z, transparent cornea ; , &, sclerotic ; , iris ; d, pupil ; 6, 

 ciliary circle ; /*, choroid, on which is seen the dichotomous termination 

 of the ciliary nerves ; <?, ciliary processes ; A, crystalline. 



SECTION OF THE EYE. 



fig. 198 : a, upper eyelid ; &, lower eyelid, showing the different lay- 



ers composing them ; c, c, conjunc- 

 tiva, reflected from posterior face of 

 eyelid upon the anterior face of the 

 globe of the eye ; d, d, orbito-oc- 

 ular aponeurosis, prolonged upon, 

 e, the sheath of the optic nerve, and 

 sending sheaths to the muscles ; f, 

 the superior rectus ; </, the inferior 

 rectus ; A, A, sclerotic, re-enforced 

 behind by sheath of optic nerve, 



section of the eye. and in front by aponeurotic expan- 



sion of recti muscles ; ', transparent cornea, cut to show its lamellar tex- 

 ture ; j, j, choroid ; &, ciliary circle ; Z, ciliary body and processes ; m, 

 iris and pupil ; n, n, canal of Fontana ; o, o, retina, continuous with sub- 



