THE ORGANS OF SPECIAL SENSE 



559 



are meridionally-running folds of the chorioid from wliich are given 

 off numerous irregular secondary folds. The processes begin low 

 at the ora serrata, gradually increase in height to about i mm., and 

 end abruptly at the margin of the iris. The ciliary processes consist 

 of connective tissue containing many pigmented cells and supporting 

 numerous blood-vessels. Invaginations lined with clear columnar 

 epithelium have been described as ciliary glands. The ciliary folds 



Cornea 



Anterio? chamber 



Iris 



Pars iridica retinn 



CaDal of Sclilemm- 

 Spaces of Fontaua- 



Conjunctiva^ 





Ciliary process 

 Ligaini-ntum 

 pectinatuni iridis 

 Circular fibres 

 of ciliary muscle 



P 



Pars ciliaris retinae 



Sclera — \ 



Perichorioidal lymph space- 



Zonule of Zinn 



Retina 



Fig. 371. — Vertical Section through Human Sclero-corneal Junction. (Cunningham.) 



are covered by the vitreous membrane, and internal to the latter is a 

 continuation forward of non-nervous elements of the retina — pars 

 ciliaris reiince (Fig. 371). This consists of two layers of columnar 

 epithelial cells, the outer layer being pigmented, the inner non- 

 pigmented. 



The ciliary muscle (Fig. 371) is a band of smooth muscle which 

 encircles the iris. It lies in the outer anterior part of the ciliary 

 body, and on cross section has a generally triangular shape. It is 

 divisible into three groups of muscle cells: {a) An inner circular 

 group near the base of the iris — circular muscle of Miiller; {h) an 



