732 



SPECIAL HISTOLOGY. 



Fi" 



29S. 



Rabbit, according to Ralira, in the posterior half of the globe), and 

 thence enter the fibrous layer of the cornea. In Man, they are readily 

 found at the margin of that tunic, in the form of 24-36 finer and 

 thicker twigs, but scarcely exceeding 0*02 of a line in size. What 



especially characterizes these nerves, 

 is not so much their mode of dis- 

 tribution, Avhich takes place with 

 numerous bifurcations and anasto- 

 moses, so as to produce a Avide ner- 

 vous plexus extending throughout 

 the cornea, as the circumstances that 

 they still contain dark-bordered 

 though fine (0-001-0-002 of a line), 

 primitive tubules, only at the mar- 

 gin of the cornea, in a zone not 

 always of uniform width, |-1 line 

 broad, and in their further course 

 present nothing but non-medullated 

 perfectly clear and transparent fibres, 0*0005-0-001 of a line at most in 

 diameter, so that they offer, at any rate, no more obstacle to the pas- 

 sage of the rays of light than the other corneal elements, as is evident 

 from the difficulty with which they are traced under the microscope. 

 The trunks of these nerves exhibit, though rarely, bifurcations of the 

 primitive tubules, but divisions of this kind are never presented in the 

 plexus formed by them, the conditions in which, however, on account of 

 their paleness, scarcely admit of being quite certainly traced. This 

 plexus is situated in the proper cornea, although nearer to its anterior 

 surface, and from the absence of any indication of free terminations to 

 the nerve-fibres, appears to consist altogether of anastomosing branches 

 of the finest sort, so that, though not in the form of loops, a mutual 

 connection of the nerve-tubes may be assumed to exist. 



The bloodvessels of the conjunctiva cornece, in the healthy condition 

 of the organ, are very scanty, and the figures given by Roraer (Am- 

 mon's " Zeitsch." V. 21, Tab. I. Figs. 9, 11), and Arnold (" Icon. org. 

 sens," II. Fig. G), I regard as exceptional instances ; but, as is well 

 known, they may become so much developed, in inflammations, as 

 almost to cover the entire cornea. The proper corneal vessels also, in 

 such cases, appear to be developed more deeply in the interior. With 

 regard to the vam serosa of the cornea, vid. § 217. The statements 

 that have been made respecting the bloodvessels of the memhrana De- 

 moursii, in inflammation of the eye [vid. Henle, "De memb. pupill.," p. 



Fig. 29S. — Coarser ramifications of the nerves of tlie cornea of the Rabbit. Where the 

 trunks are represented as dark, they contain dark-bordered primitive fibres. 



