594 



THE EYE 



THE CRYSTALLINE LENS. The crystalline lens with its sus- 

 pensory ligament forms a sort of diaphragm which separates the 

 ocular cavity into two compartments, of which the anterior is occu- 

 pied by the aqueous humor, the posterior by the vitreous humor. 



The lens is a biconvex transparent body having a somewhat 

 greater convexity on its posterior than on its anterior surface ; its 

 curvature is greater at its margin than toward its center. It con- 

 sists of a capsule, epithelium, and a substantia lentis. 



The capsule of the lens is a homogeneous membrane which 

 covers its entire surface and receives the attachment of the sus- 

 pensory ligament. It presents faint meridional striations and may 

 sometimes be separated into several lamellae (Berger *) ; this lamel- 

 lation may be purely artificial, but appears to be somewhat depen- 

 dent upon the attachment of the fibres of the suspensory ligament 

 to the surface of the lenticular capsule. 



The capsule is about twice as thick over the anterior as over the 

 posterior surface of the lens. On the former surface it is in rela- 

 tion' with the lenticular epithelium, but on the posterior surface 

 the capsule rests directly upon the substantia lentis. The anterior 



surface of the capsule is in gentle con- 

 tact with the free margin of the iris. 



The lenticular epithelium consists 

 of a single layer of cells which covers 

 the entire anterior convexity of the 

 lens, extending as far back as its 

 equator. The height of these cells 

 varies with the age of the individual. 

 In fetal life they are distinctly colum- 

 nar, in youth short columnar or cu- 

 boidal, in adult life low cuboidal or 

 flattened. Toward the margin of the 

 lens the epithelial cells become pro- 

 gressively elongated, and at its equa- 

 tor are transformed directly into the 

 fibres of the lenticular substance. 



The substantia lentis is, therefore, 

 the product of the epithelium of the 

 lens, whose cells become greatly elon- 

 gated to form slender hexagonal 

 prisms, known as the lens fibres. 



FIG. 437. LENS FIBRES. 

 1, in profile, from the crystalline 

 lens of the ox's eye ; 2, in transec- 

 tion, from the human crystalline 

 lens, x 350. (After Kolliker. ) 



* Anat. norm, et path, de 1'ceil, 1893. 



