34. Can one tickle himself?
35. Why does a bitter taste often produce vomiting?
36. Is there any danger in looking "crosseyed" for fun?
37. Should schoolroom desks face a window?
38. Why do we look at a person to whom we are listening attentively?
39. Do we really feel with our fingers?
40. Is the eye a perfect sphere? (See Fig. 61.)
41. How often do we wink?
42. Why is the interior of a telescope or microscope often painted black?
43. What is "the apple of the eye"?