LENS 583 



the ciliary muscle, which by their contraction pull upon the 

 ciliary processes, and produce relaxation of the zonula 

 ciliaris. 



Spatia Zonularia (O.T. canal of Petit). In reality the 

 spatia zonularia constitute a more or less continuous circular 

 lymph space, which surrounds the circumference of the lens. 

 It lies between the anterior and posterior layers of the 

 suspensory ligament and is filled with a watery fluid. 



By introducing the point of a fine blow-pipe into the spatia zonularis 

 through the suspensory ligament, it can be partially, or, perhaps, com- 

 pletely, inflated with air. It then presents a sacculated appearance. 



Dissection. The crystalline lens may be removed by snipping through 

 the suspensory ligament with scissors. 



Lens Crystalline The crystalline lens is a biconvex, 

 solid, and transparent structure which lies between the iris 

 and the vitreous body. It is enclosed within a glassy, elastic 

 capsule, to which the different parts of the zonula ciliaris 

 are firmly cemented, and it presents for study an anterior 

 surface, a posterior surface, and a circumference or equator. 



The anterior surface is not so highly curved as the posterior 

 surface. Its central part, which corresponds with the pupillary 

 aperture of the iris, looks into the anterior chamber of the 

 eye. Around this part the margin of the pupillary orifice of 

 the iris is in contact with the lens, whilst nearer the equator 

 the anterior surface of the lens is separated from the iris by 

 the fluid in the posterior chamber of the eyeball. The posterior 

 surface of the lens presents a higher degree of curvature than 

 the anterior surface, and is received into the fossa hyaloidea 

 of the vitreous body. The equator or circumference is rounded. 

 It forms one of the boundaries of the spatia zonularia, and 

 the manner in which the zonula ciliaris is attached to the 

 capsule in this vicinity has been described already. 



Faint radiating lines may be seen on both surfaces of the 

 lens. These give a clue to the structure of the lens. They 

 indicate the planes along which the extremities of the lens- 

 fibres come into apposition with each other. 



The capsule of the lens is a resistant glassy membrane, 

 which is considerably thicker anteriorly than posteriorly. 



The anterior wall of the capsule may now be divided with a sharp knife. 

 A little pressure will cause the body of the lens to escape through the 

 opening. The stained capsule can be very advantageously studied whilst 

 floating in water. 



