12. Why do we tire when we stand erect?

13. Why does it rest us to change our work?

14. Why and when is dancing a beneficial exercise?

15. Why can we exert greater force with the back teeth than with the front
ones?

16. Why do we lean forward when we wish to rise from a chair?

17. Why does the projection of the heel bone make walking easier?

18. Does a horse travel with less fatigue over a flat than a hilly
country?

19. Can you move your upper jaw?

20. Are people naturally right or left-handed?

21. Why can so few persons move their ears by the muscles?

22. Is the blacksmith's right arm healthier than the left?

23. Boys often, though foolishly, thrust a pin into the flesh just above
the knee. Why is it not painful?

24. Will ten minutes' practice in a gymnasium answer for a day's exercise?

25. Why would an elastic tendon be unfitted to transmit the motion of a