CHAPTER XIII. 



CRYSTALLINE LENS. 



Crystalline Lens. — A transparent, biconvex body, 

 solid and inclosed in a membrane which is transparent 

 and called its capsule. According to Chauveau the 

 measurements are vertically j\ of an inch ; trans- 

 versely yV- The posterior face, measuring transversely 

 ■^, is the more convex, for the anterior transverse 

 diameter is but -^\j. The lens is enveloped in its cap- 

 sule but nonadherent to any part of it, and this capsule 

 is of uniform thickness. Is composed of an elastic 

 homogeneous membrane, being lined anteriorly with a 

 layer of cells which give nutrition to the lens. The 

 zonule of Zinn or suspensory ligament supports the 

 lens, maintaining it in its position. This ligament, 

 you will remember, is the continuation of the mem- 

 brana limitans of the retina which passes over the 

 ciliary process to the border of the lens and separ- 

 arately passes to the front and rear of the capsule, thus 

 enveloping it and making a capsule. The canal of 

 Petit, you see, is the space between the dividing sur- 

 faces and the circumference of the lens. Function of 



this canal is in doubt ; supposed, however, to convey 

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