240 NORMAL HISTOLOGY. 



exact mode of termination of the nerve-fibrils in the 

 cornea is not yet sufficiently definitely known ; cer- 

 tain of them, however, seem to pass between the 

 anterior epithelial cells, and are believed by some 

 investigators to end in free extremities at the 

 surface. 



THE CHOROID. 



In the posterior portion of the eye, the choroid 

 presents four layers, which, although intimately con- 

 nected, and presenting no sharp line of division, may 

 yet be more or less completely separated by a care- 

 ful dissection. Directly beneath the lamina fusca of 

 the sclera, and forming the inner wall of the above- 

 mentioned lymph-sac, is the outermost layer, called 

 the lamina supra-choroidea; it is composed of a 

 series of superimposed connective-tissue membranes 

 containing delicate elastic fibres and numerous flat- 

 tened, irregular-shaped, often branching pigmented 

 cells. The layers are covered with endothelium, 

 and the spaces between them are lymph-spaces or 

 sinuses. 



Within the lamina supra-choroidea lies a layer, 

 containing the larger arteries and veins of the 

 choroid, called the external vascular layer, or the 

 layer of Haller. This layer is composed of a ground- 

 work similar to the supra-choroidea, in which the 

 vessels are imbedded, the arteries being often closely 

 surrounded by dense masses of pigmented cells. 



