Fig. 41— Growth of the lens. 



a, diagram of the equatorial region of a growing lens, showing how the cells of the lens 

 epithelium, e, elongate and reorient their axes of polarity to convert into lens fibers, /, whose 

 ends slide forward under the epithelium and backward under the capsule, c, as they take 

 on a circumferential course. 



b, diagram showing growth of lens fibers; the youngest, in the vicinity of /, are still in 

 contact with the epithelium e and capsule c (c/. a). /'- cortical fibers which are still grow- 

 ing as indicated by the arrows, and have not yet reached suture planes. Their nuclei, 

 distributed along the nuclear bow nb, slowly fade as the fibers gradually sclerose upon being 

 marooned in the heart of the lens by the addition of newer fibers peripheral to them. 

 Oldest, hardest fibers of all are those of the 'embryonic nucleus' en, formed direaly from 

 the posterior wall of the lens vesicle (c/. Fig. 40). /"- fibers which have reached the suture 

 plane sp. (All fibers in the section are shown as if in one plane — aaually, they spiral so 

 that the suture planes of the front and back halves of the lens are at right angles; c/. c). 



c, superficial fibers of the adolescent nucleus of the human lens, showing the 'lens stars' 

 which represent the intersections of the branched suture planes with the surface. Redrawn 

 from Mann. 



d, portion of equatorial section of human lens, showing radial lamellae of lens fibers and the 

 hexagonal shape of the latter in cross seaion. x 500. From Maximow and Bloom, after 

 Schaffer. b- branching of a radial lamella, which occurs repeatedly as the equatorial peri- 

 meter of the lens enlarges during growth. (All the fibers shown in a lie in one radial lamella). 



Ill 



