62 THE EYE. 



the pigment is often detached from these processes. Over the intervals between 

 the ciliary processes the zonula is, however, less closely applied to the pars ciliaris 

 retinas, so that a series of pouches, narrowing posteriorly and widening anteriorly, 

 where they communicate with the posterior chamber, become left between zonula and 

 ciliary body (recesses of the posterior chamber, Kulmt). It is into these recesses that 

 the ciliary glands (see p. 55) open. The recesses are occupied by aqueous humour, 

 and traversed by fibres belonging to the zonula of Zinn, which serve to attach 

 the outer surface of that membrane to this portion of the pars ciliaris retinae : 

 they are also partly subdivided by small subsidiary folds of the ciliary body which 

 project into the recesses. Opposite the most prominent part of the ciliary body the 

 zonula gives off bundles of fibres which pass meridionally inwards towards the 

 margin of the lens, some reaching and extending a short distance over its anterior 

 surface, others just reaching its posterior surface, and others again occupying inter- 

 mediate positions at the margin (fig. 70). They are all firmly cemented to the lens- 

 capsule. Those which pass anteriorly originate mainly from the part of the zonula which 

 lies in the intervals between the ciliary processes : they form a radially fibrous mem- 

 Fig. 71. VlEW FROM BEFORE OF THE CAIsAL OF PETIT INFLATED (from 



Sappey). 



The anterior parts of the sclerotic, choroid, iris and cornea having been 

 removed, the remaining parts are viewed from before, and the canal of Petit 

 has been inflated with air through an artificial opening. 1, front of the 

 lens ; 2, vitreous body ; 3, outer border of the canal of Petit ; 4, outer part 

 of the zonule of Zinn ; 5, appearance of sacculated dilatations of the canal of 

 Petit. 



branous layer, but it is not quite complete, for coloured injection can be easily 

 made to pass from the interstices between the lens capsule and the ciliary body into 

 the aqueous humour and vice versd. The clefts in it are fine enough, however, to 

 retain air if blown into this interstice : if this be done after removal of the whole 

 vitreous body (a removal which can be easily effected in an eye which has been 

 left for a day or two at the ordinary atmospheric temperature), the interstices which 

 correspond with the eminences of the ciliary processes are most distended, and the 

 appearance of a sacculated canal (canal of Petit), encircling the lens, is produced as 

 in fig, 71. 



The canal which is thus artificially produced is bounded behind by the part of 

 the hyaloid membrane which covers the front of the vitreous humour, and in front 

 by the imperfect membrane above alluded to as formed by the fibres of the zonula 

 which are passing to the anterior surface of the lens margin. Since these fibres 

 spring most abundantly from the part of the zonula which is opposite the intervals 

 between the ciliary processes, the membrane is as it were tied down at those intervals 

 and can only be distended between them ; hence the sacculated aspect of the so-called 

 canal. 



Berger states that in the foetus the anterior free surface of the zonula is covered 

 with a layer of endothelial cells which disappears by birth. 



As just stated, in addition to this anterior membranous prolongation of the 

 zonula, other fibres, more scattered in their disposition, pass at intervals across to 

 the periphery of the lens, some being attached to the extreme edge, others coming 

 into continuity with the posterior capsule, and others again occupying intermediate 

 positions (fig. 70). Those which pass to the posterior surface of the lens capsule 

 and to the extreme edge of the lens are stated to come for the most part from the 

 part of the zonula which overlies and is adherent to the most prominent portion of 

 the ciliary body, and these fibres therefore partially cross in direction those which 

 are corning from the depressions and passing to the anterior surface. 



