PROBLEM 2. Why CojHplex Behavior Is Possible 285 



11. How do nearsighted and farsighted persons see? Copy the upper 

 diagram in Figure 267, which illustrates how the light rays from a candle 

 are thrown on the retina. Leaving the image where it is, erase the back 

 of the eyeball and draw a long eyeball instead of a spherical one. Where 

 does the image fall with relation to the retina? A nearsighted person has 

 eyeballs Hke this. Why does he not see objects clearly when held at the 

 normal distance from the eve? A farsighted person has eyeballs that are 

 too short so that the imagre falls back of the retina. Draw this condition. 



12. Answer these questions: (a) Examine the diagram of the ear. Why 

 may ear trouble follow a sore throat or a cold in the head? (b) What 

 advice would you give if an insect crawled into the outer ear? What 

 would stop its passage? If it should be a stinging insect what treatment 

 would be most likely to make it use its sting? Some insects move toward 

 the light; what might you try? 



Further Activities in Biology 



1. Prepare a simple model to show afferent, efferent, and intermediary 

 neurons. Use strings of different colors. 



2. Dissect out the brain, spinal cord, and large nerves of a large frog. 

 This takes skill and patience because the organs are soft and easily 

 damaged. Ask your teacher what instruments to use for cutting bone, or 

 try several to find which works best. 



3. It might interest you to learn about the sense organs of some of the 

 lower animals. Do the following: (a) Is the earthworm equally sensitive 

 to light at both ends? What experiment would you use to determine this? 

 (b) Devise an experiment to find out how an earthworm responds to the 

 vibration of a nearby blow, (c) Put a splint that has been dipped in xylol 

 near an earthworm. What do you observe? Find out if all parts of the 

 body are equally sensitive to smell, (d) Look up and report on color 

 perception in bees. 



