THE APPARATUS OF Till: * i:\SES. 



fig, S0Q, 



CAPJLLARIKS IN THE VA8CCLAR 

 LAYER OF T1IK RETINA. 



continuous with tho posterior face of the ciliary process, s. where it 



afterwards forms the zouula of Zinn. 



(At tho papilla conica, all the other elements 

 than the nerve-fibres are entirely absent ; henee tliis 

 is presumed to be a 

 " blind spot.") 



Blood-vessels. T 1 1 o 

 retina possesses a par- 

 ticular vascular distri- 

 bution. Tho 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 unite the vessels of 



DIAGRAM OF THE OTRcc- tne retina with the ciliary vessels at the back of the 



TL'RE OF THE RETINA. 



p, Pigment cell of the 

 retina connected with a 

 rod ; , Cone seated on 

 the membrana liinitans 

 externa, the inner seg- 

 ment containing a cone I he lens, as its name implies, 18 a (solid) trans- 

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

 m, /, Proper fibre con- o f ^ e zono formed by the ciliary processes (behind 

 wrth^e'ofthT cells of *^ e P U P^' and partially imbedded in the vitreous 

 the membrana fenestra, 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 R U red the lens of the Horse's eye, and find the follow- 

 membrana limitans in- dimensions : vertical diameter Aths, and trans- 

 terna, m, /, i, by means ,. , r , . i ml 

 of a thick radial fibre verse diameter T %ths of an inch. 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 y^ths, 



dement?- 11 !) 011 ^ cTtic &nd th&t f the fir8t thS f an iDCh> 



fibriUaYj/.rt't, Supposed STBUCTUBE. 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; tho outer layers are almost 

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

 centre. Between the proper tissue and tho 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. 



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



THE MEDIA OP THE EYE. 



TJie Crystalline Lens. (Fig. 383, >.) 



