THE EYE. 331 



the cornea, and, in fact, is continuous with it. The tunica 

 propria has an abundant supply of blood-vessels, and is loosely 

 connected with the sclera by fibres, which become more numer- 

 ous and firm in the vicinity of the corneal margin. 



The nerves of the conjunctiva may be seen by cutting small 

 pieces of fresh conjunctiva from a pig or calf and examining 

 them in aqueous humor, or in a 1 per cent, aqueous solution of 

 common salt care being taken to support the cover-glass at 

 the sides, in order to avoid pressure. The nerve-fibres can then 

 be seen passing under the epithelium ; they can be distin- 

 guished with certainty by their annular constrictions (anneaux 

 constricteurs) ; after penetrating a short distance, however, 

 they lose their medullary sheath and form open networks 

 under the epithelium ; a few fibres find their way toward the 

 surface between the epithelial cells. 



The gold method is of special use in exposing the finer 

 nerve-branches. The question of the manner in which the 

 nerves ultimately end is still a point in dispute. 



The lymph-spaces of the conjunctiva are quite numerous, 

 especially near the corneal border ; here they are narrow, and 

 finally pass forward to unite with the lymph-spaces of the cor- 

 nea, from which they can be injected by means of a solution 

 of alkanet-root in turpentine.' 



The normal conjunctiva does not have any true papillae, but 

 on the tarsal portion the surface often has small papilliform 

 projections covered with epithelium. 



The cornea. This tunic is covered with stratified epithe- 

 lium (a), comprising layers of flat, serrated, and cylindrical 

 cells. Directly beneath these is the anterior limiting or Bow- 

 man's membrane (b) ; this is a clear, homogeneous stratum, 

 which differs from the substantia propria of the cornea only in 

 containing no lymph-spaces or cells. It can be divided up 

 into the same tine fibres as the cornea itself, and its inner bor- 

 der has no distinct limit, the fibres passing directly into the 

 corneal tissue ; when this layer has been destroyed, as by a 

 perforating ulcer or wound, it is not regenerated. 



The substantia propria of the cornea (5, c) is made up of 

 lamellae, like the leaves of a book ; these lamellae, which at 

 first appear homogeneous, can be separated into fine fibres, just 



1 See chapter on General Methods. 



