386 NEUROLOGY, OR ANATOMY OF NERVOUS SYSTEM 



its layers and binding them together, are the radiating fibers, 

 or fibers of Miiller. They form at one extremity the membrana 

 limitans interna, and at the other the externa. 



The vitreous body is a transparent gelatinous fluid enclosed 

 in a transparent membrane, the hyaloid, and fills about four- 

 fifths of the eyeball. In front it is hollowed out to receive the 

 lens and its capsule, being adherent to the back of the latter. 

 In the centre of the vitreous from the entrance of the optic 

 nerve to the back of the lens runs a canal. It contains fluid, 

 is about T V inch in diameter, and is called the canal of Stilling. 



The crystalline lens is a solid transparent biconvex body 

 which lies, enclosed in its capsule, in front of the vitreous 

 and behind the iris. The greater convexity is behind, and the 

 lens measures anteroposteriorly J inch and transversely ^ inch. 

 It consists of concentric laminre which are progressively harder 

 from without inward. 



The capsule is an elastic, transparent, structureless mem- 

 brane, in contact anteriorly with the iris and held in place by 

 the suspensory ligament. 



The sy/.y/;r//,s'on/ lif/dinrnt is a thin, transparent membrane 

 placed between the vitreous humor and the ciliary processes, 

 and presents externally a number of folds which receive those 

 of the ciliary processes. It is really a part of the hyaloid mem- 

 brane, which runs forward to the front of the margin of the 

 lens. It is also called the zonula of Zinn, and is covered exter- 

 nally by the pars ciliaris retinae. Between its back part and 

 the lens is a space, the canal of Petit. This canal is bounded 

 in front by the suspensory ligament (zonula of Zinn), behind 

 by the vitreous, and at its base is the capsule of the lens. 



The aqueous humor is the fluid which fills the space between 

 the suspensory ligament and capsule behind and the cornea 

 in front. That part of this space which lies in front of the 

 iris is called the anterior chamber; the part behind the iris is 

 the posterior chamber. The latter is really only the small 

 interval between the iris, suspensory ligament, and ciliary 

 processes. 



For a more complete description of the minute structure 

 of the eye the reader is referred to the standard books on 

 anatomy and histology. 



