31. Name and define the two kinds of muscles. Illustrate each. What is the structure of a muscle? Of what is a fibril itself composed? How does the peculiar construction of the muscle confer strength? 32. Describe the tendons. What is their use? Illustrate the advantages of this mode of attachment. 33. What two special arrangements of the tendons in the hand? Their use? How is the rotary motion of the eye obtained? 34, 35. What is a lever? Describe the three classes of levers. Illustrate each. Describe the head as a lever. What parts of the body illustrate the three kinds of levers? Give an illustration of the second class of levers. The third class. Why is the Tendon of Achilles so named? What is the advantage of the third class of levers? Why desirable in the hand? What class of lever is the lower jaw? 36. What advantages are gained by the enlargement of the bones at the joints? Illustrate. How do we stand erect? Is it an involuntary act? 37. Why can not a child walk at once, as many young animals do? Why can we not hold up the head easily when we walk on "all fours"? Why can not an animal stand erect as man does? 38. Describe the process of walking. Show that walking is a process of falling. Describe the process of running. What causes the swinging of the hand in walking? Why are we shorter when walking? [Footnote: Stand a boy erect against a wall. Mark his height with a stick. Now have him step off a part of a pace, and then several whole paces. Next, let him close his eyes, and walk to the wall again. He will be perceptibly lower than the stick, until he straightens up once more from a walking position.] Why does a person when lost often go in a circle? In which direction does one always turn in that case? [Footnote: Take several boys into a smooth grass lot. Set up a stick at a distance for them to walk toward. Test the boys, to find which are left-handed, or right-handed; which left-legged or right-legged. Then blindfold the boys and let them walk, as they think, toward the mark. See who varies toward the right, and who turns to the left.] 39. What is the muscular sense? Value of educating it? How do we gratify it? 40. What effect has exercise upon a muscle? Is there any danger in violent exercise? For what purpose should we exercise? Should exercise be in the open air? What is the rule for exercise? Is a young person excusable, who leads a sedentary life, and yet takes no daily outdoor exercise? What will be Nature's penalty for such a violation of her law? Will a postponement of the penalty show that we have escaped it? 41. Ought a scholar to study during the time of recess? Will a promenade in the vitiated air of the schoolroom furnish suitable exercise? What is the best time for taking exercise? What class of persons can safely exercise before breakfast? 42. What are the advantages of the different kinds of exercise? Should we not walk more? What is the general influence upon the body of vigorous exercise?