568 



THE EYE 



FlG. 420. CORNEAL CORPUSCLES, ISOLATED. 



Highly magnified. (After Waldeyer.) 



face. The fibrous bundles of these lamellae, being arranged in 

 meridional curves parallel to the surface, appear to cross one an- 

 other at right angles in the central portion of the circular cornea. 



Other fibres, arcuate fibres, 

 pass from one layer to an- 

 other ; so firmly uniting them 

 that it is impossible to tease 

 the cornea into its component 

 lam ell 33. 



The intervals between the 

 fibrous layers are occupied 

 by interlamellar, cement, or 

 ground substance, in which 

 lymphatic channels and large 

 flattened cells, the corneal 

 corpuscles, can be demon- 

 strated. The corneal corpus- 

 cles are branched lamellar 

 connective tissue cells, which 

 occupy the large lymphatic 



spaces or lacunae of the interlamellar ground substance, and which 

 send fibre-like processes into the interlacing lymphatic channels. 



The posterior homogeneous membrane, or membrane of Desce- 

 met (posterior basal membrane), is similar in structure to the ante- 

 rior. Like the latter, though formerly considered an elastic mem- 

 brane it does not give the specific reactions of elastic tissue. It is 

 somewhat thicker than Bowman's membrane. At its margin the 

 membrane is continuous with fibrous bundles which are directed 

 outward into the ligamentum pectinatum, and, at least in some 

 animals, through this ligament into the ciliary margin of the iris. 

 The membrane of Descemet can be readily detached from the 

 corneal substance by teasing. 



. The posterior epithelial layer (corneal endothelium) consists of 

 clear, cuboidal or flattened cells, placed edge to edge, and bound 

 together by intercellular bridges. At the margin of the cornea it 

 is reflected over the lateral wall of the anterior chamber to the 

 anterior surface of the iris. Its cells rest upon the posterior homo- 

 geneous membrane. 



All the tissues of the cornea, during life, are absolutely trans- 

 parent. The elements of which they consist are of almost iden- 

 tical refractive indices, so that in very fresh, or in living tissue, it is 



