5. _Sprains_ are produced when the ligaments which bind the bones of a joint are strained, twisted, or torn from their attachments. They are quite as serious as a broken bone, and require careful attention lest they lead to a crippling for life. By premature use a sprained limb may be permanently impaired. Hence, the joint should be kept quiet, even after the immediate pain is gone. 6. _A Dislocation_ is the forcible displacement of a bone from its socket. It is, generally, the result of a fall or a violent blow. The tissues of the joint are often ruptured, while the contraction of the muscles prevents the easy return of the bone to its place. A dislocation should be reduced as soon as possible after the injury, before inflammation supervenes. PRACTICAL QUESTIONS. 1. Why does not a fall hurt a child as much as it does a grown person? 2. Should a young child ever be urged to stand or walk? 3. What is meant by "breaking one's neck"? 4. Should chairs or benches have straight backs? 5. Should a child's feet be allowed to dangle from a high seat? 6. Why can we tell whether a fowl is young by pressing on the point of the breastbone? 7. What is the use of the marrow in the bones? 8. Why is the shoulder so often put out of joint? 9. How can you tie a knot in a bone? 10. Why are high pillows injurious? 11. Is a stooping posture a healthful position? 12. Should a boot have a heel piece? 13. Why should one always sit and walk erect? 14. Why does a young child creep rather than walk? 15. What is the natural direction of the big toe? 16. What is the difference between a sprain and a fracture? A dislocation? 17. Does the general health of the system affect the strength of the bones? 18. Is living bone sensitive? _Ans_.--Scrape a bone, and its vessels bleed; cut or bore a bone, and its granulations sprout up; break a bone, and it will heal; cut a piece away, and more bone will readily be produced; hurt it in any way, and it inflames; burn it, and it dies. Take any proof of sensibility but the mere feeling of pain, and it will answer to the proof.--BELL'S _Anatomy_. Animal sensibility would be inconvenient; it is therefore not to be found except in diseased bone, where it sometimes exhibits itself too acutely.--TODD'S _Cyclopedia of Anatomy_. 19. Is the constitution of bone the same in animals as in man? _Ans_.--The bones of quadrupeds do not differ much from those of man. In general they are of a coarser texture, and in some, as in those of the elephant's head, we find extensive air cells.--TODD'S _Anatomy_. II. THE MUSCLES. "Behold the outward moving frame, Its living marbles jointed strong With glistening band and silvery thong, And link'd to reason's guiding reins By myriad rings in trembling chains, Each graven with the threaded zone Which claims it as the Master's own." HOLMES. ANALYSIS OF THE MUSCLES.