98 THE EYE AND EAR. 



ii. The anterior chamljer 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 chamher of the eye is the 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 0^ the muscles of the eyeball, and the fat which sur- 

 rounds 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, cover- 

 ing 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. 



