I5i8 



A MANUAL OF ANATOMY 



Crystalline Lens. — ^The crystalline lens is situated directly behind 

 the pupil and iris, from which latter it is separated by the posterior 

 chamber. It is a solid, transparent, biconvex body, the posterior 

 surface being more convex than the anterior, and it is enclosed 

 within a homogeneous, transparent envelope, called the capsule 

 of the lens. The centre of the anterior surface is called the anterior 

 pole, and that of the posterior surface the posterior pole. The line 

 connecting these two poles constitutes the axis of the lens, and a 

 line surrounding the periphery represents the equator. The trans- 

 verse measurement of the lens is about ^ inch, and its axis 

 measures about ^ inch. The anterior surface at its central part 

 faces the pupil. External to this, the pupillary margin of the 

 iris rests upon it, and, external to this again, is the posterior chamber. 



Fig. 640. — Fibres of the Crystalline Lens (highly magnified) 

 (After Kolliker). 



A, Fibres of the Ox (seen on edge) ; B, Human fibres (seen on end). 



with part of the aqueous humour. The posterior surface is received 

 into the patellar fossa on the anterior aspect of the vitreous body. 

 The periphery is related to the suspensory ligament, the canal of 

 Petit, and the ciliary processes. From the anterior and posterior 

 poles delicate lines radiate towards the equator. In early life these 

 are three in number on each surface. Those on the anterior surface 

 are directed as follows : one vertically upwards, and the other two 

 downwards and outwards in a diverging manner, thus X- Those 

 on the posterior surface are directed as follows : one vertically 

 downwards, and the other two upwards and outwards in a diverging 

 manner, thus Y. These lines represent the free margins of septa 

 within the lens, upon which the ends of the lens-fibres terminate. 



Structure. — ^The lens is laminar in structure. The outer laminae 

 are soft in consistence, but the succeeding ones gradually become 



