NERVES OF THE CORNEA. 



433 



Kuhne,* and still more completely, Engelmann,f have fol- 

 lowed the distribution of the nerves in the cornea of the Frog 

 examined in perfectly fresh aqueous humour. 



Trunklets composed of from five to fifteen or more medullated 

 fibres enter the cornea at six or eight points of its periphery. At 

 several points also isolated medullated fibres, or two together, 

 penetrate its substance. The greater number of these fibres 

 run at first in a straight direction, and for a distance of from 

 ()-'2 to O5 of a millimeter towards the centre of the cornea; a 

 few only are given off at right angles from the trunklets at the 

 margin of the cornea, and these, after running for some distance 

 parallel to the border, finally turn inwards. 



Fig. 392. 



Fig. 392. Portion of cornea of a Frog, prepared with chloride of 

 gold, nn, Nerves. 



The nerves usually lose their medulla at a short distance 

 from the corneal margin (0*3 to 0'5 of a millimeter) ; and then, 

 undergoing repeated dichotomous division, form a wide-meshed 

 plexus situated nearer to the posterior than to the anterior 

 surface of the cornea. The occurrence of true anastomoses has 

 not been demonstrated in this plexus of the Frog, any more 

 than in that of Mammals. The presence of sheaths is indicated 



* Untersuchungen uber das Protoplasm, etc., p. 132. 

 + Loc. cit., p. 15. 

 VOL III. F F 



