660 



DISSECTION OF THE EYE. 



space (fig. 227, ?') (posterior chamber) behind the iris. In front they cor- 

 respond with the back of the iris towards their inner end, but arc sepa- 

 rated from it by pigment ; and behind they are closely connected with the 

 membrane (t) (suspensory ligament) on the front of the vitreous body, 

 and n't into hollows between eminences on the anterior surface of that 

 membrane. 



Structure The choroid coat and its ciliary processes are formed prin- 

 cipally of bloodvessels. Ramified pigment cells make up most of the rest 

 of the coat. 



The stroma or web of the choroid is formed by the outrunners of spe- 

 cial pigment cells (fig. 230, c ) which unite together, and construct, with 

 fine areolar tissue, a fibrous network. Its meshes are finer towards the 

 inner than the outer surface of the choroid. On the exterior and interior 

 of the fibrous web the vessels ramify, with the following difference in their 

 arrangement. 



At the outer part (fig. 231) the larger branches of both arteries and 

 veins are situate ; and the veins (//) form curves (vasa I'orticosa) as they 

 end in four or five chief efferent trunks. In the interspaces of the vessels 

 are the ramified pigment cells (fig. 230-, A ), which contain a nucleus and 

 molecular grains of dark-brown coloring matter. At the inner part of 

 the choroid the vessels form a network of capillaries without pigment 

 cells, and with meshes smaller than elsewhere, whose interstices are 

 rather less towards the back than the front of the eyeball : this part of 

 the choroidal coat is described sometimes as a separate layer (tunica 

 Ruyschiana). 



In the ciliary processes there is a similar texture of ramified blood- 

 vessels, though with larger capillary meshes than in the choroid ; and 



Fig. 231. 



a. Sclerotic, cut, and reflected. 



b. Choroid coat. 



c. Iris. 



d. Circular. 



e. Radiating fibres of ciliary mus- 



cle. 

 /. Ciliary nerves, and g, ciliary 



arteries between the two 



outer coats. 

 h. Veins of the choroid coat. 



VIEW OF THB FROST OF THE CHOROIDAL COAT AND IRIS EXTERNAL SURFACE (Zinn). 



the intermixed pigment cells lose their coloring matter towards the free 

 ends. 



CILIARY MUSCLE (fig. 231). In the eye from which the sclerotic coat 

 has been removed, the white band of the ciliary muscle (e) (annulus 



