578 THE EYE 



present a toothed appearance ; the ligament derives its name from 

 this peculiarity. 



THE POSTERIOR CHAMBER is an annular cavity, somewhat 

 triangular or trapezoidal in transaction, whose lumen, like that of 

 the anterior chamber, is occupied by aqueous humor, suspended in 

 which are the fibres of the suspensory ligament of the crystalline 

 lens. 



It is limited anteriorly by the internal surface of the iris, and 

 antero-externally by the ciliary processes. Its postero-internal 

 boundary is formed by the marginal portion of the lens, together 

 with the adjacent portion of the hyaloid membrane, which incloses 

 the vitreous humor. 



THE INTERNAL COAT 



The internal coat of the eyeball is divisible into three portions : 

 1, the pars optica retinae or retina proper ; 2, the pars ciliaris reti- 

 nae, and 3, the pars iridis retinas. 



The last two portions, though morphologically continuous with 

 the pars optica retinae, differ therefrom in their physiological func- 

 tion ; they respectively form the innermost layer of the ciliary 

 body and iris. As such they have already been described. 



The Retina. The retina (pars optica retinae) may be said to be 

 formed by the radial expansion of the fibres of the optic nerve 

 which enters the eye at the inner side of its posterior pole, piercing 

 the sclera and choroid and spreading out over the inner surface of 

 the eyeball. 



These nerve fibres arise from groups of nerve cells which are 

 disposed in layers to form the optic and retinal ganglia (ganglion 

 nervi optici and ganglion retince). The association of nerve cells 

 and fibres with their supporting tissues forms the inner, cerebral, 

 or neural portion of the retina. The dendritic arborizations of 

 many of these nerve cells lie within the outer half, or neuro-epithe- 

 lial portion of the retina. 



The retina may be said to extend forward from the entrance of 

 the optic nerve as far as the posterior margin of the ciliary body, 

 where it apparently ends abruptly with an indented border, the ora 

 serrata. From this border the retina is continued farther forward, 

 but only as the dark pigmented layers of the ciliary processes and 

 iris. In the usual preparations these layers contrast intensely with 

 the opaque white color of the true retina." Like all the other tissues 

 which are placed in the optical axis of the eye, the retina, during 



