88 THE EYE 



ii. The anterior chamber of the eye is the space between 

 the cornea and the lens : it is small and contains 

 the aqueous humour, a watery fluid. 



iii. The posterior chamber of the eye is a large space 

 behind the lens : it is filled by the vitreous 

 humour, a gelatinous body. 



iv. The choroid is the black pigmented layer lining 

 the sclerotic, and continuous in front with the 

 iris. 



v. The retina is a delicate transparent membrane 

 lining the eyeball. It is readily detached from 

 the choroid, except at the point where the optic 



nerve enters. 



\ 



B. The Eye of the Sheep or Ox. 



1. Dissect off the muscles of the eyeball, and the fat which 

 surrounds the optic nerve : note the following points : 



i. The shape. The eyeball is more spherical than in 

 the frog. 



ii. The sclerotic covers about five-sixths of the eyeball : 

 it is tough, white, and opaque. 



iii. The cornea, which covers the outer sixth of the 

 eyeball, is circular, transparent, and continuous at 

 its margin with the sclerotic : it is more convex 

 than the sclerotic. 



iv. The conjunctiva is a delicate epithelial layer, con- 

 tinuous with the skin, covering the front of the 

 cornea and part of the sclerotic. 



v. The iris is the oval pigmented ring seen through 

 the cornea. 



vi. The pupil is the central, oval, or dumb-bell shaped 

 aperture surrounded by the iris. 



vii. The optic nerve is a thick white bundle of nerve 

 fibres piercing the sclerotic at the back of. the 

 eye. 



2. Cut all round the cornea, with stout scissors, about | inch 



