300 PHYSIOLOGY. 



14. Color is due to difference in the rapidity of vibration in the 

 waves of light. 



15. Some eyes do not distinguish these differences and are color 

 blind. 



1 6. Pain in the eyes comes through the fifth pair of nerves, not 

 through the optic nerves. 



17. Binocular vision makes objects "stand out" more distinctly as 

 solid bodies. 



1 8. Impressions of light linger, making after-images. 



19. Defects in eyesight are much more common among civilized 

 men than with the uncivilized men or animals. 



20. The care of the eyes must be made a subject of study and care- 

 ful thought by all reading people. 



Questions. i. What iythe position of the eyeballs during sleep? 



2. What is "cataract"? 



3. What is the cause of " double vision "? 



4. Why does the well eye sympathize with the affected one? 



5. Why does looking at a bright light often cause a person to 

 sneeze ? 



6. Why is weeping associated with grief ? 



7. What is the condition of one who is "cross-eyed"? 



8. Compare the pupils of a man, a cat, and a cow. 



9. Does the color of the eye have any relation to the strength of 

 eyesight ? 



10. Why is one blinded on entering a bright room from the dark? 

 n. Why is one going from a bright room into the dark unable to 

 see at first, but gradually sees more distinctly ? 



12. Why can one not see well when the eye " waters "? 



13. If each eye has a blind spot, why are there 'not blank spaces in 

 the field of vision? 



14. What advantage has a stereoscopic view over a single view? 

 How are stereoscopic views made? 



15. Should the lights which illumine a pulpit or platform be so 

 placed that they can shine into the eyes of the congregation? How 

 should they be arranged? 



