434 THE CORNEA, BY ALEXANDER ROLLETT. 



both in the medullated as well as in the non-medullated fibres, 

 by nuclei elongated in the direction of the axis of the nerve. 

 As the nerves undergo progressive division, the nuclei become 

 less and less numerous, till they are at length only found in 

 the nodal points of the plexus, which they appear to distend. 

 Ganglion-like structures are thus formed similar to those that 

 have been observed in the corneal nerves of Mammals. Nei- 

 ther in the Frog nor in the Mammal, however, have we to deal 

 with true ganglia in the nodal points of the nervous tissue. 



From this plexus, which in the Frog lies almost entirely in 

 one and the same plane, very fine branches are given off at 

 various points, which, both in front and behind the coarse plexus 

 (as far as to about the junction of the anterior with the two 

 posterior thirds), form a close trellis-like nervous expansion in 

 the substance of the cornea. It is doubtful whether any anas- 

 tomoses exist in this trellis-work, but in the nodal points of its 

 finest fasciculi nuclei are here and there scattered. Here again, 

 however, there are no true ganglionic enlargements. The finest 

 fibres are gradually lost in the corneal tissue, without its being 

 possible to arrive at any definite conclusion of the exact mode. 

 Engelmann* has differentiated the above-described nervous 

 expansion from the nerves of the corneal epithelium, on the 

 ground of its being placed in the proper substance of the 

 cornea.f These last are branches of the above-described coarse 

 plexus, which run vertically or nearly so to the external epi- 

 thelium. Associated with these are a few fine non-medullated 

 fibres, which pass directly forwards to the epithelium from the 

 periphery. There are collectively from forty to sixty of these 

 nerve trunks in each cornea. At the line of demarcation between 

 the corneal tissue and the external epithelium these nerves 

 give off a variable number of branches, which run in all direc- 

 tions parallel to the surface, and ultimately, to some extent 

 undivided, but in part also after frequent subdivision, reach the 

 long cells of the deepest layer of the epithelium. A close plexus 

 is thus again formed at this point, the terminal fibres proceed- 

 ing from which reach those cell layers of the epithelium that 



* LOG. dt., p. 17. 

 t Loc. cit.j p. 19. 



