THE CRYSTALLINE LENS 



1109 



The capsule of the lens (capsula lentis) (Fig. 778) is a transparent, highly elastic, 

 and brittle membrane, which closely surrounds the lens, and is composed in part of 

 cuticular and in part of connective tissues. It is not white fibrous tissue, and is 

 not true elastic tissue (Szymonowicz). Its outer surface is composed of lamellae 

 and possesses transverse striations. It rests, behind, in the fossa hyaloidea in 

 the fore part of the vitreous body (Fig. 815); in front, it is in contact with the free 

 border of the iris, this latter receding from it at the circumference, thus forming 

 the posterior chamber of the eye (Fig. 820) ; and it is retained in its position chiefly 

 by the suspensory ligament of the lens, already described (Fig. 820). The capsule 

 is much thicker in front than behind, and when ruptured the edges roll up with the 

 outer surface innermost, like the elastic lamina of the cornea. 



ANTERIOR 

 SURFACE 



ANTERIOR/ 

 POLE 



POSTERIOR 

 SURFACE 



POSTERIOR 

 POLE 



FIG. 817. The crystalline lens, hardened 

 and divided. (Enlarged.) 



FIG. 818. The terms used in the orientation of 

 the lens. (Toldt.) 



The lens is a transparent, biconvex body, the convexity of the posterior surface 

 being greater than that of the anterior. The central points of these surfaces are 

 termed respectively the anterior and posterior poles (polus anterior et polus posterior 

 lentis). A line connecting the poles constitutes the axis of the lens (axis lentis), 

 while the marginal circumference is termed the equator (aequator lentis). The 

 lens measures from 9 to 10 mm. in the transverse and vertical diameters and 

 about 4 mm. from anterior to posterior pole. 



FIG. 819. Diagram to show the direction and arrangement of the radiating lines on the front and back 

 of the fetal lens. A. From the front. B. From the back. 



Structure. The lens consists of an outer, soft part, easily detached (substantia corticalis\ 

 and a central, firm part (nucleus lentis) (Fig. 817). Faint lines (radii lentis) radiate from the 

 poles to the equator. In the adult there may be six or more of these lines, but in the fetus they 

 are only three in number and diverge from each other at angles of 120 degrees (Fig. 819). On 

 the anterior surface one line ascends vertically and the other two diverge downward and outward. 

 On the posterior surface one ray descends vertically and the other two diverge upward. They 

 correspond with the free edges of an equal number of septa composed of an amorphous sub- 

 stance, which dip into the substance of the lens. When the lens has been hardened (as in alcohol), 

 it is seen to consist of concentric layers, or laminae, each of which is interrupted at the septa. 

 Each lamina is built up of a number of parallel, hexagonal lens fibres (fibrae lentis}, the edges of 

 which are serrated to fit similar serrations of adjacent lens fibres, while the ends of the fibres 



