THE OCULAE CONTENTS 



667 



aqueous humor in which the surface of the lens is bathed. This change 

 is accompanied by a hardening or cornification and slight shrinkage 

 of the lens fibers, so that those prisms which come to occupy the center 

 of the lens form a dense, hard mass of non-nucleated fibrous cells with 

 faintly serrated margins; the peripheral fibers retain their smooth edges 

 and their nuclei, and form a protoplasmic mass of much softer con- 

 sistency. The hardened central mass is 

 the so-called nucleus of the lens. Any 

 opacity of the lens or its capsule is known 

 as a cataract. 



The nuclei of the lens fibers remain in 

 the neighborhood of the equator, where 

 they are first formed, and are thus con- 

 tained within a narrow, superficial, equa- 

 torial zone, the nuclear zone. 



Each lens fiber is disposed along a 

 meridian of the lens, and extends from 

 its anterior to its posterior hemisphere; 

 the fibers are so arranged that they abut 

 upon one another, end to end, along V-- 

 shaped lines which radiate from either 

 pole. This union is often quite firm, and 

 thus are formed long fibrous bands which 

 can be traced from the anterior to the 

 posterior hemispheres of the lens. These 

 bands are distributed in a peculiar man- 

 ner. Near each pole along the line of 

 abutment, the band may be said to bend 

 upon itself with a sharp curve making 



an angle of about 60 degrees whose convexity is directed toward the pole, 

 the parallel fibers being so arranged as to form a sector whose apex is 

 also directed toward the pole. The corresponding sectors of opposite 

 poles overlap one another so that the fibrous bands are continued from 

 one side of one polar mass to the reverse side of the overlapping sector 

 and so back, on the farther side, to the adjacent sector of the former 

 hemisphere. By teasing, fibrous bands can sometimes be traced suc- 

 cessively through all of the polar sectors and thus back to a sector be- 

 neath -that from which the start was made. Obviously no individual 

 lens fiber is of sufficient length to extend from pole to pole of the 

 lens. 



FIG. 564. LENS FIBERS. 



1, in profile, from the crystal- 

 line lens of the ox's eye; 2, in 

 transection, from the human crys- 

 talline lens. X 350. (After 

 Koffiker.) 



