NORMAL HISTOLOGY. 



homogeneous layers, which sometimes exhibit a delicate longi- 

 tudinal striation. 



The posterior corneal endothelium, or endothelium of Des- 

 cemet's membrane, consists of a single layer of regular poly- 

 hedral plates, whose oval nuclei project slightly beyond the bodies 

 of the cells. 



Blood-vessels are absent in the cornea, except within a narrow 

 zone, about i mm. in width, at the limbus or margin ; in the foetus, 

 however, the vessels extend well towards the centre and form the 

 precorneal capillary net-work. 



The lymphatics of the cornea are represented by the system of 

 intercommunicating spaces and canaliculi ; these clefts open 

 into lymphatic radicles at the periphery, which, in turn, communi- 

 cate with the larger anterior lymphatic vessels. Perineurial lymph- 

 channels enclose the larger nerve-trunks, which they accompany 

 for a variable distance into the corneal tissue; these lymphatic 

 channels communicate directly with the corneal spaces at frequent 

 intervals. 



The nerves of the cornea are very numerous, and are distributed 

 largely within the anterior layers. They enter at the corneal limbus 

 as some sixty radially-disposed twigs, each of which includes from 



FIG. 367. 



Subbasilar plexus of corneal nerves from rabbit ; gold preparation. 



three to twelve fibres; the latter almost at once, within .5 mm. of 

 the limbus, become non-medullated. 



Within the substantia propria the nerve-fibres form a coarse 

 ground-plexus at a level corresponding to about the middle third 

 of the corneal tissue ; from this net-work twigs are sparingly given 

 off to supply the deepest layers, while others pass towards the 



