586 



HANDBOOK OF PHYSIOLOGY. 



Structure of the Sclerotic Coaf.The sclerotic coat is composed of 

 connective tissue, arranged in variously disposed and inter-communicat- 

 ing layers. It is strong, tough, and opaque, and not very elastic. 



Structure of the Cornea. The cornea is a transparent membrane 

 which forms a segment of a smaller sphere than the rest of the eyeball, 

 and is let in, as it were, into the sclerotic with which it is continuous all 

 round. It is coated with a laminated anterior epithelium (, Fig. 393), 

 consisting of seven or eight layers of cells, of which the superficial ones 

 are flattened and scaly, and the deeper ones more or less columnar. Im- 

 mediately beneath this is the anterior elastic lamina (Bowman). 



FIG. 391. 



FIG. 392. 



FIG. 391. Vertical section of rabbit's cornea, stained with gold chloride, e, Laminated anterior 

 epithelium. Immediately beneath this is the anterior elastic lamina of Bowman, n, Nerves forming 

 a delicate sub-epithelial plexus, and sending up fine twigs bet veen the epithelial cells to end in a 

 second plexus on the free surface; d, Descemet's membrane, consisting of a fine elastic layer, and 

 a single layer of epithelial cells; the substance of the cornea, /, is seen to be fibrillated, and con- 

 tains many layers of branched corpuscles, arranged parallel to the free surface, and here seen edge- 

 wise. (Schofield.) 



FIG. 39 <?. Section through thechoroid coat of the human eye. 1, elastic membrane, structure- 

 less or finely fibrillated; 2, chorio-capillaris or tunica Ruyschiana; 3, Proper substance of the cho- 

 roid with large vessels cut through; 4, suprachoroidea; 5, sclerotic. (Schwalbe.) 



The cornea tissue proper as well as its epithelium is, in the adult, 

 completely destitute of blood-vessels; it consists of an intercellular 

 ground-substance of rather obscurely fibrillated flattened bundles of con- 

 nective tissue, arranged parallel to the free surface, and forming the 

 boundaries of branched anastomosing spaces in which the cornea-cor- 

 puscles lie. These branched cornea-corpuscles have been seen to creep 



