|Henry Gray (18251861). Anatomy of the Human Body. 1918.|
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 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 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 laminæ, 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 serratedthe 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 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).
FIG. 884 The crystalline lens, hardened and divided. (Enlarged.) (See enlarged image)
FIG. 885 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. (See enlarged image)
FIG. 886 Profile views of the lens at different periods of life. 1. In the fetus. 2. In adult life. 3. In old age. (See enlarged image)
FIG. 887 Section through the margin of the lens, showing the transition of the epithelium into the lens fibers. (Babuchin.) (See enlarged image)