VITREOUS BODY 581 



Dissection. For the study of the vitreous body and the crystalline lens, 

 which together may be termed the "eye-kernel," it is better to take an 

 eyeball which is not perfectly fresh (Anderson Stuart). The. eyeball 

 selected for this purpose should be allowed to stand untouched from one 

 to three days, according to the season. The coats of the eye should then 

 be divided round the equator, and on gently separating the cut edges, and 

 turning the coats anteriorly and posteriorly, the " eye-kernel " will slip out. 

 It should be allowed to drop into a vessel filled with clean water. The 

 examination of the parts forming the "eye-kernel" will be greatly facilitated 

 by placing it en masse in strong picro-carmine solution for a few minutes. 

 When removed from the staining fluid, it should be well washed in water. 

 In this way the hyaloid membrane enclosing the vitreous body, the capsule 

 of the lens, and the zonula ciliaris, are stained red, and their connections 

 become very apparent (Anderson Stuart). 



Vitreous Body. This is a soft, yielding, transparent, 

 jelly-like body, which occupies the posterior four-fifths of the 

 interior of the eyeball. The retina is spread over its surface 

 as far forwards as the ora serrata, but is in no way attached 

 to it, except at the optic disc. Anterior to the ora serrata, 

 the ciliary processes are applied to the vitreous body and 

 indent its surface. More anteriorly, the vitreous body pre- 

 sents a deep concavity, the fossa hyaloidea, for the reception 

 of the posterior convex surface of the crystalline lens. 



The substance of the vitreous body is enclosed within a 

 delicate transparent membrane, which completely envelops 

 it, and receives the name of the hyaloid membrane. Extend- 

 ing anteriorly through the midst of the vitreous mass, from the 

 region of the optic disc to the crystalline lens, is a minute 

 canal, lined with a tube-like prolongation of the hyaloid 

 membrane, and containing a watery fluid. This is termed 

 the hyaloid canal ' it represents the path taken by a branch of 

 the arteria centralis retinae, which, in the foetus, extends to and 

 supplies the capsule of the lens, but afterwards disappears. 



The hyaloid canal, as~ a rule, cannot be seen in an ordinary dissection 

 of the eyeball ; but if the " eye-kernel " be shaken up in the picro-carmine 

 solution as recommended by Anderson Stuart, it may sometimes be rendered 

 evident through the staining fluid entering it. It is represented diagram- 

 matically in Fig. 251. 



Zonula Ciliaris (O.T. Zonula of Zinn). Between the 

 corona ciliaris externally and the margin of the lens internally 

 lies a fibrous membrane called the zonula ciliaris. Its 

 external margin is attached to the posterior surfaces of the 

 ciliary processes and the hyaloid membrane, and its internal 

 margin is connected with the lens. As it approaches the 

 margin of the crystalline lens, it splits into two parts, viz., an 



