356 MICROSCOPIC ANATOMY OF THE ORGANS. 



at the anterior surface are covered by a single layer of cubical 

 lens epithelium. This reaches as far as the equator of the lens, 

 where the cells increase in height to form lens fibres. The 

 lens fibres are flattened hexagonal prisms, which are thickened 

 at the posterior end. They run in a meridional direction from 

 the anterior surface backward. A small quantity of cement 

 substance joins the fibres together. The outer fibres in the 

 region of the equator possess oval nuclei, while in the centre 

 of the lens no nuclei are present. 



The lens capsule is a clear refractive membrane, which is 

 thicker on its anterior (10-15 p) than on its posterior surface 

 (5-7 /M). On its outer surface it shows parallel striations and 

 is lamellated. In its behavior toward reagents it resembles 

 neither white fibrous nor elastic tissue. It is probably partly 

 cuticular and partly connective tissue in nature. 



(6) The Vitreous Body and the Zonula Giliaris. 



The vitreous body is made up of a tissue which contains 

 about 98 per cent, of fluid substance, the vitreous humor. 

 The firm parts have the form of fine intercrossing connective- 

 tissue fibrils, connective-tissue cells of various kinds, and 

 wandering cells (leucocytes). 



The entire vitreous body is surrounded by a refractile 

 homogeneous membrane, the membrana hyaloidea, which 

 touches on the outside the membrana limitans interna retina*. 



In the region of the ora serrata fine fibres run from the 

 surface of the hyaloid membrane and the ciliary processes 

 in a meridional direction toward the lens and insert them- 

 selves in its capsule. The insertion of the fibres in the lens 

 occupies a wide zone at the equator, which reaches some dis- 

 tance on the anterior and posterior surfaces. Taken together, 

 these (fibres zonulares) form the zonula ciliaris, which serves 

 to hold the lens in place. 



The fibres of the zonula and the equatorial zone of the lens 

 form the boundaries of a whole system of large and small 

 spaces, the spatia zonularis (canal of Petit), which are in com- 

 munication with the posterior chamber of the eye. 



