THE LENS. 



623 



the onter portion is soft and easily detached ; the succeeding layers 

 are of a firmer consistence ; and in the centre the substance becomes 

 much harder, constituting the so-called nucleus. On the anterior and 

 posterior surfaces are faint white lines directed from the poles towards the 

 circumference ; these in the adult are somewhat variable and numerous 



Flo-. 434. 



Fife. 43G. 



Fig. 434. — Front View of the Fibrotts 

 Structure of the Adult Lens (from 

 Sappey after Arnold), f 



In this figure more numerous planes of 

 intersection of the fibres are shown than in 

 fig. 4u3. 



Fi" 4.^.-. 



Fig. 435. — Laminated Structure op the 

 Crystalline Lens, shown after hard- 

 ening IN Alcohol (Arnold), l 



on the surface (fig. 434), but in the 

 foetal lens throughout, and towards 

 the centre of the lens in the adult, 

 they are three in number, diverging 

 from each other like rays at equal 

 angles of 120° (fig. 433, b and c). 

 The lines at opposite poles have an 

 alternating position (not being over 

 one another), thus of those seen on 

 the posterior surface, one is directed 

 vertically upwards (fig. 433, b), and 



Fig. 436. — Fibres of the Crystal- 

 line Lens. 350 Diameters. 



A, longitudinal view of the fibres of 

 the lens from the ox, showing the ser- 

 rated edges. B, transverse section of 

 the fibres of the lens from the human 

 eye (from Kolliker). C, longitudinal 

 view of a few of the fibres fi-om the 

 equatorial region of the human lens 

 (from Henle). Most of the fibres in C are 

 seen edgeways, and, tovrards 1, jiresent 

 the swellings and nuclei of the " nuclear 

 zone ; " at 2, the flattened sides of two 

 fibres are seen. 



