STRUCTURE OF THE LENS AND VITREOUS HUMOUR, 275 



Structure of the lens. The lens is a laminated fibrous body in- 

 closed by a transparent elastic capsule to which, around the circum- 

 ference, the fibres of the suspensory ligament are attached. Immedi- 

 ately within the capsule, in front and at the sides, there is a layer of 

 cubical epithelium termed the epithelium of the capsule, but at the 

 margin of the lens the cells become longer and pass by a gradual 

 transition into the lens-fibres (fig. 307). The fibres which compose the 

 lens are long and riband-shaped, with finely serrated edges (fig. 308, A) ; 

 in transverse section they appear prismatic (B). Many of the superficial 

 fibres are nucleated (c), the lens-fibres having originally been developed 

 by the elongation of epithelium-cells. 



The vitreous humour is composed of soft gelatinous tissue, appa- 

 rently structureless when examined in the fresh condition, but contain- 

 ing a few scattered amoeboid cells, the processes of which are often long 

 and varicose, and the cell-bodies distended by large vacuoles. The 

 hyaloid membrane, which invests the vitreous humour, is homogeneous 

 and structureless except in the region of the ciliary processes, where it 

 is fibrous in structure, forming the zonule of Zinn and spreading out 

 into the suspensory ligament of the lens. This part of the hyaloid 

 membrane is connected with a circular fibrous portion of the vitreous 

 humour which serves to give additional firmness to the attachment of 

 the fibres of the suspensory ligament of the lens (A. Stuart). 



