452 



THE EYE. 



D. THE VASCULAR TUNIC OF THE EYE. 



THE CHOROID, THE CILIARY BODY, AND THE IRIS. 



From without inward the following layers may be differentiated 

 in the choroid : (i) the lamina suprachoroidea ; (2) the lamina vas- 

 culosa Halleri ; (3) the lamina choriocapillaris ; and (4) the glassy 

 layer, or vitreous membrane. 



The lamina suprachoroidea consists of a number of loosely 

 arranged, branching and anastomosing bundles and lamellae of 

 fibrous tissue, joined directly to the sclera. These bundles and 

 lamellae consist of white fibrous connective tissue containing numer- 

 ous elastic fibers, among which a few connective-tissue cells are dis- 

 tributed. Pigment cells are also present in varying numbers. The 

 bundles and lamellae are covered by endothelial cells, and the spaces 

 and clefts between them, and between the lamina suprachoroidea 

 and the lamina fusca, constitute a system of lymph-channels the 

 perichoroidal lymph-spaces. 



Sclera 



Lamina supra- ._ 

 choroidea. 



Lamina vascu- 

 losa Halleri. 



Lamina chorio- 



Fig. 355. Section through the human choroid ; X I 3 ( >- 



The lamina vasculosa of the choroid fs also composed of simi- 

 lar lamellae, which, however, are more closely arranged. The blood- 

 vessels constitute the principal portion of this layer, the vessels 

 being of considerable caliber, not capillaries. They are so distrib- 

 uted that the larger vessels, the veins, occupy the outer layer of 

 the lamina vasculosa. The venous vessels converge toward four 

 points of the eyeball, forming at the center of each quadrant one 

 of the four vena vorticosce. The arteries, on the other hand, describe 

 a more meridional course. 



