826 THE APPARATUS OF THE SENSES. 



continuous with the posterior face of the ciliary processes, where it 

 afterwards forms the zonula of Zinn. 



p. 389 



(At the papilla conica, all the other elements 

 than the nerve-fibres are entirely absent ; hence this 

 presumed to be 



s presume o e a 

 "blind spot.") 



Blood-vessels. The 

 retina possesses a par- 

 ticular vascular distri- 

 bution. The arteria 

 centralis retince, with its 

 vein, enters the optic 

 nerve at a short distance 

 from the globe, and 

 with it passes into the 

 eye; they traverse the 

 papilla, and immediate- 

 ly divide into two 

 branches, one of which 

 is directed upwards, 

 the other downwards. 

 Close and fine anastomoses 



Fi S- 390 ' 



* ne 



CAPILLARIES IN THE VASCULAR 

 LAYER OF THE RETINA. 



unite the vessels of 

 with the ciliary vessels at the back of the 



DIAGRAM OF THE STRUG' 

 TITRE OF THE RETINA. 



p, Pigment cell of the 



retina connected with a THE MEDIA OP THE EYE. 

 rod; n, Cone seated on 



the membrana limitans The Crystalline Lens. (Fig. 383, j.) 

 externa, the inner seg- 

 ment containing a cone The lens, as its name implies, is a (solid) trans- 

 ellipsoid, and a needle ; parent body, sustained at the smaller circumference 

 m i /> Proper fibre con- o f ^h e zone, formed by the ciliary processes (behind 

 wtth^e^f thTcells of *^e P U P^> and P arti ally imbedded in the vitreous 

 the membrana Irenestra, humour). It is biconvex in shape, and flatter on its 

 whose cells are in com- anterior than its posterior surface. We have mea- 

 munication with the gured the lens of the Horse's eye, and find the follow- 

 terna 5 ^ 11 ^ ^"b^means * n Dimensions : vertical diameter T %ths, and trans- 

 of 1 a, a 'thi'ck radial fibre verse diameter y^ths f an i ncn The posterior face 

 with an oval nucleus is evidently more convex than the anterior, for we 

 attached ; g, g, Multi- found the transverse diameter of the last to be T 4 ot ns 

 polar ganglion of nerve ftnd ^. Q f fa Q firgt ^ths of an inch. 



fibrilla *q r\ Suppose**! STRUCTURE. The lens is enveloped in a trans- 



connection of the nucleus parent membrane, the capsule, which contracts no 

 with prolongation of a adhesions with it. Its thickness is uniform in the 

 ganglion cell. Horse, and its tissue is slightly striated transversely ; 



its internal face is lined by a layer of pavement epithelium. 



The proper tissue of the lens is disposed in concentric layers, which the 

 microscope proves to be composed of fibres; the outer layers are almost 

 fluid (gelatinous), but their consistence gradually increases towards the 

 centre. Between the proper tissue and the epithelium of the capsule are 

 two or three layers of round cells, whose dissolution some time after death 

 forms the liquor Morgagni which is consequently nothing more than the 

 result of a cadaveric phenomenon. 



(The capsule of the lens is composed of tissue exactly similar to the 



