LENS AND ITS CAPSULE. 



669 



Covering the anterior surface of the lens, and connecting it with the 

 capsule, is a layer of very transparent nucleated polygonal cells, which 

 can be recognized only in a fresh eye : these become elongated towards the 

 circumference of the lens, and seem to pass into the superficial lens-fibres. 



Structure. After the lens has been hardened by spirit or boiling, it may 

 be demonstrated to consist of a series of layers (tig. 236) arranged one 

 within another, like those in an onion. Under the microscope each layer 

 may be seen to be constructed of minute parallel fibres. It consists mostly 

 of albumen, and no bloodvessels are found in its texture. 



The laminae of each surface have their apices in the centre, where the 

 septa meet ; they may be detached from one another at that spot, and may 

 be turned outwards towards the equator of the lens. 



The constituent fibres of the laminae are about 5oViy tn f an i ncn ^ n 

 diameter, solid, and flattened at the margin of the lens ; and the deeper 



Fig. 236. 



Fig. 237. 



A REPRESENTATION OF THK LAMINAE IN A HARDENED 

 LENS. 



a. The nucleus. 



b. Superficial laminae. 



fibres are narrowed and less distinct. In 

 the superficial softer fibres are contained 

 granular nuclei (fig. 237, a). 



The edges are slightly waxy ; and each 



fibre touches six Others (fig. 237, 6), viz., 



two on each side, with one above, and an- 

 other below : contiguous fibres are there- 

 fore dovetailed together, and this inter- 



, , . . . . . , ,, . , 



locking is best seen m the lens of the cod- 



VIEWS OF THE LENS FIBRES, AFTEB 



HE.NLE. 



a - Surface fibres with their nuclei, in 

 the e i liatorial r ^' lon of the lens - 



6. Transverse section of the fibres of 



the surface of the Ien8) ghowing 



their union with others. 



The ends are soft and not well-defined, 

 and are connected with the partitions on the opposite surfaces of the lens 

 in this way : those attached at the union of two septa on the one aspect, 

 are fixed to the extremity of a septum on the other aspect : and the fibres 

 passing between two septa are nearer to the pole at one end, and farther 

 from it at the other, while the middle ones are at the same distance from 

 the ends of the septa on both aspects. 



Changes in the lens with age. The form of the lens is nearly spherical 

 in the foetus ; but its convexity decreases with age, particularly on the an- 

 terior aspect, until it becomes flattened in the adult. 



In the foetus it is soft, is reddish in color, and is not quite transparent ; 

 in mature age it is firm and clear; and in old age it becomes flatter on both 

 surfaces, denser, and of a yellowish color. 



