VISION. 229 



limited behind by an elastic lamina, and covered in front 

 with epithelium. The lining membrane of the eyelids and 

 front of the eye is called the conjunctiva ; it is continuous 

 with the skin at the margin of the lids; inside the lids it is 

 pink with blood-vessels; where reflected on the sclerotic or 

 white of the eye, it becomes more delicate and transparent, 

 although still a distinct membrane easily detached; but when 

 ifc reaches the cornea, every structure corresponding with 

 the cutis vera is lost, and there remains only a stratified 

 epithelium closely adherent to the proper corneal structure. 

 No blood-vessels lie beneath this epithelium to interfere with 

 vision; but when inflammation is excited, vessels push their 

 way inwards with a rapidity which is exceedingly interest- 

 ing, as showing how speedily capillaries can be developed.* 



Fig. 113. HUMAN EYE enlarged, with part of the cornea and scle- 

 rotic removed, a-, Sclerotic; 6, cornea; c, choroid coat, showing 

 arteries and veins, and the ciliary nerves on the surface ; d, iris ; 

 e, pupil; /, ciliary muscle. , 



170. Looking at the living eye, one sees, through the trans- 

 parent cornea, the part which is coloured. This is a muscular 

 curtain, the iris, with a circular perforation in the centre, the 



* An injection by Stirling, in my possession, beautifully demon- 

 strates that the conjunctival network of capillaries, on reaching the 

 edge of the cornea, is reflected and continuous with a deeper network 

 belonging to the sclerotic. A similarly reflected sheet of capillaries 

 is described by Hyrtl at the attachment of the round ligament of the 

 hip-joint to the femur. 



