390 SPECIAL HISTOLOGY. 



corona ciliaris, as I shall term these cells, is most distinctly 

 shown on the ciliary processes, as a clear border sharply defined 

 on the inner side, and often 0006 — 0008'" broad, whose large, 

 frequently shortly cylindrical cells, may usually be recognised 

 without any trouble, and are always rendered distinct by acetic 

 acid ; whence it is evident that the boundary is composed only of 

 them, and is not a special membrane. Posteriorly, this cellular 

 stratum reaches as far as the ora serrata, extending anteriorly 

 to the termination of the ciliary processes (fig, 296 w), and on 

 either side it is continuous, without any line of demarcation, 

 with the pigmentary layer, the clear cells being gradually 

 replaced by cells containing pigment. 



Excepting these cells, the zonula is a thin, transparent but 

 tolerably firm membrane, stretching from the ora serrata 

 retinae as far as the border of the lens, and appearing to be a 

 continuation of the hyaloid membrane. It consists of peculiar, 

 pale fibres, already very well characterised by Henle, resembling 

 certain forms of reticular connective tissue, except that they 

 are more rigid, usually present no distinct fibrils, and are 

 less swollen in acetic acid. They commence, very fine, a 

 little behind the ora serrata retince on the outer side of the 

 hyaloid membrane, although most intimately connected with 

 it, in part like fibrils of connective tissue, then run forwards, 

 forming a layer at first more lax, and becoming more and 

 more dense, and increasing in thickness (up to 0-004 — or even 

 O'OT" and more), with numerous divisions and anastomoses, 

 and for the most part parallel with each other, until they con- 

 stitute, at the free portion of the zonula, a perfect, continuous 

 layer — though still containing a few isolated bundles, and are 

 ultimately blended with the capsule of the lens. From the 

 ora serrata to the commencement of the " canal of Petit," no 

 hyaloid membrane besides the fibres of the zonula, can be any 

 longer distinguished, whilst at the canal itself, where the sub- 

 stance of the vitreous body is separated from the fibrous layer, 

 it is again furnished with a limitary membrane, only thinner 

 than before, which constitutes the posterior wall of the w canal of 

 Petit," and extends no farther than to the border of the lens, 

 where it ceases as a special membrane, the vitreous body being 

 most intimately united with the posterior lamina of the cap- 

 sule of the lens. 



