Shearer, Nerve Terminations in the Sclachiaii Cornea. 2 1 5 



the epithelium which could in any way answer to the various 

 networks described by Klein (7). 



Klein states that the sub-epithelial network is situated 

 beneath Bowman's membrane and that he was able to remove 

 the entire epithelium without disturbing this net-work. On 

 examining a similar preparation from the dog-fish with the 

 epithelium so removed no trace of this plexus is found, but in- 

 stead we get a view of regular plexus of the corneal tissue 

 proper (Fig. 4) so very different in appearance from the much 

 larger nerves of the epithelium. 



This network, of which Fig. 4 is but a very poor represen- 

 tation, is of the very finest texture, the fibers forming it being of 

 the very finest in size, perfectly uniform throughout their course 

 and at once to be distinguished from the nerves of the epithe- 

 lium by the way in which they branch at right angles and their 

 irregular course and all pretty much within the same plane. 

 Every sheet of the corneal substance proper seems to have a 

 special network of these fibers over it. When one network is 

 within focus the the networks of the layers deeper can be faintly 

 made out, and by properly adjusting up and down one can bring 

 nearly all the networks into view one after the other. One pe- 

 culiarity of these nerve fibers is their sharply granular appear- 

 ance as if made up of a series of closely arranged dots one af- 

 ter the other in a delicate strand. These fibers in branching 

 and winding about amongst the corneal cells do not keep any 

 definite relation with them, and it is needless to say no anasto- 

 moses with them or their processes was to be distinguished. 

 As Dogiel has found in man, the nerve fiber never comes into 

 real relation with the cell but simply passes over it or along 

 one border. 



On comparing Fig. 4, with Fig. 7 of Dogiel's (2) pa- 

 per the general resemblances of this network in selachians and 

 man is very apparent. There is a tendency in selachians to 

 greater regularity of branching of the fibers at right angles, 

 they run in one direction for a certain distance then abruptly 

 turn and run at right angles to their former course, while in 

 man the change of direction is less sharp and sudden. 



