1020 ORGANS OF THE SENSES AND THE COMMON INTEGUMENT 



Structure. The lens is made up of soft cortical substance and a firm, central part, the nucleus 

 (Fig. 884). 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 

 (Fig. 885) ; on the anterior surface one line ascends vertically 

 and the other two diverge downward; on the posterior sur- 

 face 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 substance, which 

 dip into the substance of the lens. When the lens has been 

 hardened it is seen to consist of a series of concentrically 

 arranged laminae, each of which is interrupted at the septa 

 referred to. Each lamina is built up of a number of hexagonal, 

 ribbon-like lens fibers, the edges of which are more or less ser- 

 rated the serrations fitting between those of neighboring 

 fibers, while the ends of the fibers come into apposition at 

 the septa. The fibers run in a curved manner from the septa 

 on the anterior surface to those on the posterior surface. 

 No fibers pass from pole to pole; they are arranged in such 

 a way that those which begin near the pole on one surface 



FIG. 884. The crystalline lens, hardened and divided. (Enlarged.) 



FIG. 885. Diagram to show the direction and arrangement of the 

 radiating lines on the front and back of the fetal lens. .4 . From the 

 front. B. From the back. 



Fia. 886. Profile views of the lena at different periods of life 

 1. In the fetus. 2. In adult life. 3 In old age. 



FIG. 887. Section through the margin 

 of the lens, showing the transition of 

 the epithelium into the lens fibers. 

 (Babuchin.) 



of the lens end near the peripheral extremity of the plane on the other, and vice versa. The 

 fibers of the outer layers of the lens are nucleated, and together form a nuclear layer, most 

 distinct toward the equator. The anterior surface of the lens is covered by a layer of transparent, 

 columnar, nucleated epithelium. At the equator the cells become elongated, and their gradual 

 transition into lens fibers can be traced (Fig. 887). 



