THE FISH 157 



these up carefully at the end and find the small olfactory 

 lobes, from which small nerve cords may be traced, toward 

 the nostrils. 



b. Back of the optic lobes is the cerebellum. Note its 

 size, shape and location in socket. The enlargement back 

 of this has important work of its own to accomplish and is 

 known as the medulla oblongata. Draw brains (X4)- 



c. The nerves to the eye, optic nerves, may now be seen 

 by lifting up the olfactory and the optic lobes. How do they 

 appear at the base of the lobes? How many nerves go out 

 from the brain ? Trace the nerve to the eye (cut out the skull 

 where necessary). Does the nerve branch before leaving the 

 eye ? Remove the eye from its socket and notice the muscles 

 attached. Are they arranged in pairs? How many? 



d. Dissect the eye from the front. Cut the cornea, or 

 front part, at one side and allow the thin aqueous humor to , 

 run out. What is the use of this humor? Do you think 

 it could help vision in any way? With the scissors remove 

 all of the cornea. What is now exposed? With a needle 

 lift up this curtain, the iris. How thick is it? What is its 

 color ? What is the opening called ? What is meant by the 

 color of the eye in any animal? Look closely around the 

 edge to see if there is any increase in thickness. 



Remove the iris by cutting around the eye next to the 

 outer wall. Back of the pupil find a thickened ball of trans- 

 parent matter suspended in a transparent liquid mass. This 

 is the crystalline lens suspended in the vitreous humor, of 

 which it is a specialized part. 



Remove the crystalline lens and lay it on a piece of news- 

 paper. Can you see the letters through it? How does it 

 affect them? 



