204 ANSWERS TO PRACTICAL QUESTIONS 



35. Wliy does a bitter taste often produce vomiting ? 



The fifth pair of nerves, which supplies the lip and sides of 

 the tongue, and perceives especially sweet and sour substances, 

 ramifies over the face, and hence an acid will "pucker" the 

 features ; while the ninth pair, at the base of the tongue, which 

 is sensitive to salt and bitter tastes, is distributed also to the 

 throat, and is in sympathy with the internal organs, since it 

 seems to be "a common nerve of feeling for the mucous mem- 

 brane generally." 



36. Is there any danger of looking "cross-eyed" for 

 fun ? 



The muscles used thus in sport may become permanently 

 distorted. 



37 Should school-room desks face a window ? 



No. The light should be admitted so as to fall over the 

 shoulder upon the book. Many school-rooms are arranged to 

 accommodate the teacher only, while a blinding flood of light 

 pours directly into the faces of the pupils. 



38. Why do we look at a person to ivhom we are listen- 

 ing attentively? 



One sense instinctively aids another. 



39. Do we really feel ivith our fingers ? 



No. All sensation is in the mind. 



40. Is the eye a perfect sphere ? 



No. The front projects somewhat, while, at the back, the 

 optic nerve is attached like the stein to a fruit. 



4=1. How often do we ivink? 



Five or six times a minute. 



42. Why is the interior of a telescope or microscope 

 often painted black ? 



To absorb the scattered rays of light which would confuse 

 the vision. For the same reason, the posterior surface of 



