110 INTRODUCTION TO ZOOLOGY. 



between the ribs, for nerves. How many pairs do 

 you find? 



3. Find nerves leading from the spinal cord to the 

 wings, and to the legs. How do these nerves com- 

 pare in size with other spinal nerves? 



4. Slice off the top of the skull and expose the 

 brain. Make out the following parts : the cerebrum, 

 in front, consisting of two lobes separated by a deep 

 groove ; the cerebellum, undivided, behind ; the optic 

 lobes, at the sides, below the cerebrum and cerebellum. 



5. Lift up the brain and see the optic nerves run- 

 ning to the eyes. Do they cross? Do they unite with 

 each other? 



6. Draw the brain. 



The Feathers. 



1. Study one of the large wing feathers. The 

 hollow rounded part is the calamus, or quill. The ex- 

 panded part is the vane. The central portion of the 

 vane is the rhachis. The small divisions on each side 

 of the rhachis are the barbs. 



2. Examine a few of the barbs. See the barbules, 

 interlacing between the barbs. These hold the barbs 

 in position. 



3. Do you find any barbules on the down? 



4. Draw a feather. 



An Egg. 



1. Note the shape, size, and smoothness of the 

 shell. Are the two ends alike? 



2. Break the shell and examine the lining. Of 

 how many layers is the lining composed? In which 

 end is the air bubble? 



3. Is the " white " all alike, or is there more than 

 one kind? 



