424 THE NERVES AND THE SENSE ORGANS 



10. When a stick with a spark at one end is swung about in a circle, 

 the eye "sees" a continuous ring of light; why? Why does a meteor 

 (" shooting star") seem to have a "tail?" 



11. Why does it rest the eye, after we have been reading, to look at 

 a distant object? 



12. Adenoids, colds in the throat, etc., often cause deafness; what 

 part of the ear do they stop up first? 



