THE EYE AND ITS APPENDAGES. 



345 



to the level of the underlying- ciliary muscle. The stroma of the 

 processes is a continuation of the connective tissue of the orbicular 

 zone, this layer being the true prolongation of the choroid, since the 

 muscular tissue must be regarded as an intercalation between the 

 sclerotic and choroid coats. The vitreous lamina is continued as a 

 delicate homogenous membrane, 3 to 4 fj. in thickness, over the inner 

 surface of the ciliary processes. Inside this layer the internal face of 

 this entire region, including the ciliary ring and the ciliary body, as 

 well as the iris, is covered by the deeply-pigmented rudimentary 

 layers of the pars ciliaris retinae, consisting of an inner small 

 row of tall columnar elements and an outer sheet of low pig- 

 mented epithelium. Since these layers represent the rudimentary 

 folded anterior laminae of the ectodermic optic vesicle, the ciliary 

 processes and the iris consist of two genetically distinct parts, the 



FIG. 372. 



Section through ciliary region of human eye : A, cornea; a, b, c, its epithelium, substantia propria, 

 and endothelium ; C, scleral conjunctiva, terminating at d; B, sclera/ e, sclero-corneal juncture ; D, 

 iris ; E, ciliary body covered by pigment-layer, /; k, fibrous stroma of ciliary processes ; /J bands of 

 pectinate ligament; g, spaces of Fontana ; s, canal of Schlemm; v, venous channels; m, n, o, 

 meridional, radial, and circular (Miiller's) fibres of ciliary muscle ; r, subscleral space bridged by 

 fibrous bands. 



mesodermal connective-tissue stroma, containing blood-vessels 

 and muscle-fibres, and the inner deeply-pigmented ectodermal 

 stratum. 



