226 



Organ of Vision. 



305. The View with the Ophthal- 

 moscope of the Pigmeiited Fun- 



dus OcillL Magn. = 7. After E d. v. J a e g e r. 



306. The View with the Ophthal- 

 moscope of the Unpigmented (al- 

 bino tic) Fundus Ocidi. 



Magn. = 7- After Ed. v. Jaeger. 



The retina, expansion 

 of the optic nerve, is the 

 innermost layer of the eye- 

 ball, the real organ of vision. 

 The place where the optic 

 nerve pierces the sclerotic 

 and choroid coats, is marked 

 by an eminence, the Colli- 

 culus sen Papilla nervi opticl ; 

 here the bloodvessels, Art. 

 and Vena centralis retinae, 

 find their entrance and exit. 

 At the point of entrance of 

 the optic nerve the power of 

 vision is absent (blind 

 spot), and this part lies a 

 little to the inner side of the 

 point of most perfect vision. 

 This latter point has a 

 slight central depression, 

 Fovea centralis ; in the eye of 

 the cadaver it is seen as a 

 yellow spot, Macula lutea, 

 and only there it is connec- 

 ted by two eminences, Plicae 

 centrales, with the papilla. 

 The layers of the retina (see 

 Fig. 307) are distinct up to 

 the region of the Ora scrrata; 

 from here on only the struc- 

 tureless Membrctna limitans, 

 lying between the layer of 

 rods and cones and innermost 

 layer of the choroid, remains. 



The vitreous body, 

 Corpus vitreum, occupies the 

 greater portion of the eyeball ; 

 it is covered by a thin glassy 

 membrane, the Hyaloidea, 

 which, in front, where it pas- 

 ses forwards to the margin 

 of the crystaline lens, is 

 known as the Zonula Zinnii. 

 Between the anterior and 

 posterior fibres of the zonula 

 is the Canalis Pet it i (see 

 Fig. 301). 



