CHAPTER IX. 



THE IRIS. 



Iris. — The Iris forms in the interior of the eye, in front 

 of the crystalline lens, a veritable diaphragm, with a cen- 

 tral opening — the pupil. Is a beautifully colored and 

 contractile membrane. It is attached at its periphery 

 to the sclera through the fibers of the ligamentum pec- 

 tinqtum. The shape of the iris is elliptical. It rests 

 (the pupillary margin) posteriorly,- on the lens cap- 

 sule. Its anterior surface is free. The iris is con- 

 tinuous with the ciliary body and choroid, and 

 together these constitute the uveal tract, upon which 

 the aqueous humor, the lens and vitreous, depend for 

 nourishment. The iris divides the space between 

 the cornea and the p,nterior face of the lens and 

 internal extremities of the ciliary processes into two 

 compartments of unequal size — the anterior being 

 the larger and the posterior having only a virtual ex- 

 istence, as the iris rests upon the lens capsule. Both 

 the anterior and posterior chambers contain the aqueous 

 humor in which the iris floats free. Tlie anterior 

 surface of the iris is lined with a layer of epithelial cells, 



which are continuous with those on the posterior sur- 



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