15 ANSWERS TO PRACTICAL QUESTIONS 



15. Why can we exert greater force with the back teeth 

 than with the front ones ? 



(See Physiology, page 49.) 



The lower jaw is a lever of the second class. In the 

 former case the resistance to be overcome, /". e., the 

 weight, is situated much nearer the power. 



1 6. Why do we lean forward when we wish to rise from 

 a chair? 



(See Philosophy, pages 57-8.) 



In order to bring the center of gravity over the feet. 



17. Why does the projection of the heel-bone make walking 

 easier ? 



(See Frontispiece, and also Fig. 18 in Physiology?) 



It brings the power further from the fulcrum or weight. 



1 8. Does a horse travel easier over a flat than a hilly 

 country 1 



No. The variety of travel in a hilly country, other 

 things being equal, tends to rest the horse, and enable 

 him to better endure the fatigue of the journey. 



19. Can you move your upper jaw? 



All the bones of the face, except the lower jaw, are 

 firmly and immovably articulated with one another and 

 with the cranium. LEIDY. 



20. Are people naturally right or left-handed? 



Many persons are naturally either right or left-handed ; 

 but most can and should learn to use either hand with 

 equal facility. 



