SUMMARY OF THE ANATOMY OF THE EYE. 69 



terior chamber is much the larger. The iris, in its central 

 portion surrounding the pupil (P), is in contact with the lens. 

 Its circumference is just in front of the line of origin of the 

 ciliary muscle. 



Ket. The retina ; an exceedingly delicate, transparent 

 membrane, lining the choroid and extending to about -^ of 

 an inch behind the ciliary processes, the anterior margin form- 

 ing the ora serrata. O. The optic nerve penetrating the 

 retina a little internal to and below the antero- posterior 

 axis. The layer of rods and cones is situated externally, 

 next the choroid. Internal to the layer of rods and cones, 

 are the four granular layers ; next, the layer of nerve-cells ; 

 next, the expansion of the fibres of the optic nerve ; and 

 next, in apposition with the hyaloid membrane of the vitre- 

 ous humor, is the limitary membrane. The layer of rods 

 and cones is supposed to be the portion which receives visual 

 impressions, the rods and cones being connected with the 

 nerve-cells, and through them with the fibres of the optic 

 nerve, by delicate filaments. The macula lutea and the fo- 

 vea centralis are exactly in the axis of vision. 



C. The crystalline lens ; elastic, transparent, enveloped 

 in its capsule and surrounded by S. L.J the suspensory liga- 

 ment. 



S. L. The suspensory ligament ; the anterior layer con- 

 nected with the anterior portion of the capsule of the lens, 

 and the posterior, with the posterior portion of the capsule. 

 The folded portion of this ligament, which is received be- 

 tween the folds of the ciliary processes, is called the zone of 

 Zinn. The triangular canal between the anterior and the pos- 

 terior layers of the suspensory ligament and surrounding the 

 equator of the lens is called the canal of Petit. 



Y. The vitreous humor ; enveloped in the structureless 

 hyaloid membrane, which membrane is continuous in front 

 with the suspensory ligament of the lens. 



