CHOROIDAL COAT WITH ITS STRUCTURE. 



659 



If a vertical section is made of another eyeball, it will show the ciliary 

 processes in their natural position, and will demonstrate the relative situa- 

 tion of all the parts. This section, which is made with difficulty, should 

 be attempted in water with a sharp large knife, and on a surface of wax or 

 wood, after the cornea and sclerotic have been cut with a scissors. When 

 the eye has been divided, the halves should remain in water. 



The CHOROID COAT (fig. 227, b) is a thin membrane of a dark color, 

 and extends from the optic nerve to the fore part of the eyeball. When 

 viewed on the eye in which the ciliary muscle is entire, it appears to ter- 

 minate there ; but it may be seen in the other dissections to bend inwards 

 behind that muscle, and to end in a series of projections (ciliary processes) 

 behind the iris. 



This covering is rather thicker and stronger behind than in front. It 

 is supported at the bottom of the eyeball by its close connection to the 

 sclerotic coat, and in front by the ciliary muscle. Posteriorly it is pierced 

 by a round aperture for the passage of the optic nerve ; and anteriorly it 

 is united with the iris. 



The outer surface (fig. 231) is flocculent, and is covered by the rem- 

 nants of a thin membranous layer, (membrana fusca, supra-choroidea) be- 

 tween it and the sclerotic coat : on it may be seen small veins arranged 

 in arches, and the ciliary arteries and nerves. The inner surface is smooth, 

 and touches the thin dark pigmentary layer of the retina (fig. 227). 



Fig. 229. 



Fig. 230. 



INNER VIKW OF THE FRONT OP THE CHOROID PIGMENT CELLS OF THE EYEBALL (Kolliker). 



COAT WITH ITS CILIARY PROCESSES, AND THE A. Ramified pigment cells of the choroid coat. 



BACK OF THK IRIS. B. Front view of the hexagonal cells of the 



a. Anterior piece of the choroid coat pigmentary membrane. 



6. Ciliary processes. 



c. Iris. 



d. Sphincter of the pupil. 



e. Bundles of fibres of the dilator of the pupil. 



The ciliary processes (fig. 229, b) are solid projections on the inner 

 surface of the choroidal coat, and are arranged in a circle. About 85 in 

 number, they lie side by side, and consist of larger and smaller eminences; 

 at their inner extremity they are united by transverse ridges. 



About T \jth of an inch in length, they increase in depth internally, and 

 projecting around the lens, bound circumferentially by their free ends the 



