146 PRACTICAL ZOOLOGf. 



2. The liquid in the cavity back of the cornea is the 

 aqueous humor. 



3. Cut around the margin of the cornea and remove it. 



4. The dark membrane now exposed is the iris. Pinch 

 the eye slightly at the sides to make the iris show 

 more distinctly. The hole in its centre is the pupil. 

 With the forceps raise the edge of the iris around 

 the margin of the pupil to see that it is here unat 

 tached to the structures underneath. Observe the 

 color and markings of the iris. 



5. From one end of the pupil cut outward to the outer 

 margin of the iris, then cut around its outer margin 

 and remove it. Observe the color and markings of 

 its posterior surface. 



6. The body now laid bare is the crystalline lens. Touch 

 it. 



7. With a sharp knife make a quick light gash across 

 the surface of the lens to cut through the thin coat 

 which envelops it, the lens capsule. Enlarge the 

 opening thus made and carefully pry out the lens 

 with the handle of the forceps, noting closely, in so 

 doing, the difference between the front and back sur- 

 faces. Lay the lens on a piece of newspaper and look 

 through it at the letters. Make a drawing of the lens 

 as seen from the front, and as seen from one side, 

 naming the front and back surfaces. 



8. With the forceps seize the lens capsule where it was 

 cut and pull it gently but firmly to one side ; this 

 action will probably tear the mass within the eye 

 loose from the outer coats ; repeat the pull in all 

 directions. With the scissors now cut outward about 

 one-fourth of an inch from the edge of the hole marte 



