CORNEA STRUCTURE. 341 



pies the anterior fifth of the globe of the eye, and is con- 

 nected with the sclerotica at the ciliary ligament, by a 

 very firm union. The cornea stands out prominent from 

 the sclerotic, somewhat after the manner of the crystal of a 

 watch. It is a perfectly transparent body, highly polished, 

 convex on its anterior surface, and concave on its posterior; 

 thus presenting a lens of the concavo-convex form. Its shape 

 is spherical, and represents the segment of a smaller sphere 

 placed on that of a larger. Its transverse diameter ex- 

 ceeds the vertical by about one line, which is found to be 

 owing to the overlapping of the sclerotic upon its superior 

 and inferior border. Its density is slightly greater in the 

 centre than at the circumference. Its structure is complex 

 and consists of a variety of different tissues, as the tunica 

 conjunctiva, the cornea proper, cornea elastica, and the lining 

 membrane of the anterior chamber. 



The tunica conjunctiva is a fine layer, so closely adhering 

 to the cornea as to have its existence denied by some anat- 

 omists, though prolonged maceration has satisfactorily 

 proven its presence, and its continuity with that covering 

 the sclerotic. It is found to be very sensitive, and to con- 

 sist of cells, of which the superficial are flat, while the 

 deeper are round, and contain a transparent fluid which, 

 soon after death, becomes opaque and white, forming that 

 peculiar film seen then upon the eye. 



The cornea proper is composed of transparent lamina, 

 which may be few or many, according to the pleasure of 

 the dissector, and which are connected together by the most 

 delicate cellular tissue containing, it is said, a small quan- 

 tity of fluid by which these lamina are kept in their proper 

 relations with each other. 



These lamina can, by a slight rubbing between the fin- 

 gers, be made readily to glide the one upon the other. 

 Their transparency is destroyed by boiling, and they be- 

 come permanently opaque; deposition of lymph among the 

 layers, from inflammation, produces the same result, causing 

 what is called, opacity of the eye. The several layers of 

 the cornea proper, though somewhat resembling cartilage, 



