LENS AND ITS CAPSULE. 801 



the lens-capsule, which joins externally the hyaloid membrane opposite 



the anterior termination (ora serrata) of the retina. After the extent ; 



ciliary processes of the choroid coat are detached from it, dark lines 



of pigment cover the surface ; and when these are washed away, is marked 



plaits 'ciliary processes) come into view, which are less prominent b - v folds ; 



and longer than the processes of the choroid coat, but do not 



quite reach the lens-capsule internally. The two sets of prominences 



are dovetailed together, the projections of one being received into 



hollows between the other ; and in the fresh state the two structures inner 



are closely adherent. The membrane contains numerous stiff attachment 



radiating fibres, which internally become collected into bundles, 



and are attached to the margin, and the adjacent part of the 



anterior surface of the lens-capsule. The tenseness is influenced by condition 



the state of the ciliary muscle, for during its contraction the how alte 



membrane is rendered lax by the drawing forwards of the ciliary 



processes. 



Canal of Petit. Around the margin of the lens-capsule is a narrow Canal of 

 space (fig. 288, o) about one-tenth of an inch across, which is situate 

 between the suspensory ligament and the front of the vitreous situation ; 

 humour. When the canal has been opened, and filled with air by anterior 

 means of a blow-pipe, it is sacculated at regular intervals, like the StS^ 

 large intestine, by the inflation of the plaits of the anterior 

 boundary. The margin of the capsule of the lens bounds the space 

 internally. 



LESS AND ITS CAPSULE. The lens is situate behind the pupil of Lens of the 

 the eye (fig. 288, g\ and brings to a focus on the retina the rays of es 

 light entering through that aperture. 



The CAPSULE is a firm and very elastic transparent case, which Capsule of 

 closely surrounds the lens proper. The anterior surface is free, 

 and projects towards the pupil, around which it touches the iris ; relations of 

 but externally the two are separated by a small interval the surface, 

 posterior chamber (i) ; close to the margin of the lens it is joined 

 by the suspensory ligament (f). The posterior surface is received posterior 

 into a hollow on the front of the vitreous body, to which it is surface ' 

 inseparably united. The circumference of the case gives attachment and cir- 

 to the posterior fibres of the suspensory ligament, and behind this cu 

 bounds the canal of Petit (o). 



The capsule is a structureless glassy membrane, much thicker is a homo- 

 over the front of the lens, as far out as the attachment of the membrane ; 

 suspensory ligament, than over the back, where it is very thin in 

 the centre. In the adult human eye the capsule of the lens is not 

 provided with blood-vessels ; but in the f cetus a branch of the vessels only 

 central artery of the retina supplies it. 



Dissection. The lens will be obtained by cutting across the Open cap- 



,, . , ,.,.,.. , , sule of lens. 



thin membranous capsule m which it is enclosed. 



The LENS is a solid and transparent doubly convex body ; but gjjjjjjjj re 

 the curves are unequal on the two surfaces, the posterior being equally ; 

 greater than the anterior. Its margin is somewhat rounded ; and 

 the measurement from side to side is one-third of an inch, but dimensions 

 from before back about one-fifth of an inch. The density increases density ; 



D.A. 3 F 



