LESSON XXII. *HE EYE. 



1. Take a fresh eye of an ox or sheep, and note 

 The transparent cornea. Surrounding and continu- 

 ous with this, the dirty-white sclerotic which forms the 

 outer coat of the rest of the eye ; the posterior two-thirds 

 will probably be covered with fat. 



The conjunctiva, a continuation of the mucous mem- 

 brane of the eyelids. In taking the eye out of the orbit 

 this membrane is cut through where it passes from the 

 eyelids to the sclerotic. Dissect it forwards in any one 

 place; it will be traceable to the junction of the sclerotic 

 and the cornea. (Its epithelium is continuous with that 

 of the cornea.) 



2. Clear away the fat surrounding the four straight 

 muscles, it will be seen that their tendons form a layer 

 under the conjunctiva of the sclerotic. 



3. Cut away the conjunctiva and muscles, and re- 

 move the fat around the optic nerve ; this pierces the 

 sclerotic on the nasal side, and not in the axis of the 

 eye. 



4. Cut through the cornea close to its junction with 

 the sclerotic and remove it ; the anterior chamber of the 

 eye, containing clear, limpid aqueous humour, is thus 

 laid bare. Observe the iris with its central aperture 

 through which projects the anterior part of the lens. 



5. At a little distance from the cornea cut through 

 the sclerotic, being careful not to cut too deeply; it will 

 separate easily from the pigmented subjacent choroid, 



