107. The chief source of injury, however, to the ear is from the introduction of solid substances into the auditory canal, with the design of removing insects or other foreign objects that have found their way into the ear; or with the design of scraping out the ear-wax. For displacing a foreign object, it is usually sufficient to syringe the ear gently with warm water, the head being so held that the {226} fluid easily escapes. If a live insect has gained entrance to the ear, it may first be suffocated by pouring a little oil upon it, and afterward removed by syringing the ear as just mentioned. 108. The removal of ear-wax is generally unnecessary; for, as we have before seen, Nature provides that the excess of it shall become dry, and then spontaneously fall out in the form of fine scales. The danger from the introduction of solid implements into the outer ear is chiefly found in the fact that the membrane which lies at the bottom of it is very fragile, and that any injury of it is liable to be permanent, and to permanently impair the hearing of the injured ear. QUESTIONS FOR TOPICAL REVIEW. _Give as full statements as you can on the following subjects_: 1. Production of sensation 177, 178 2. Variety of sensations 178, 179 3. General sensibility 179, 180 4. The sensation of pain 180 5. The uses of pain 180, 181, 182 6. Special sensation 182, 183 7. Organs of touch 183, 184 8. The sense of touch 184, 185, 186 9. The delicacy of touch 186, 187 10. Sensations of temperature and weight 187, 188 11. The organ of taste 188, 189 12. The sense of taste 189, 190 13. Relations of taste, etc. 190, 191 14. Influence of education, etc. 191, 192 15. The sense of smell 192, 193 16. The nerve of smell 193, 194 17. Uses of the sense of smell 194, 195 18. The sense of sight 196, 197 19. Light, and the optic nerve 197, 198 20. The organ of sight 198, 199 21. The orbits 199 22. The eyelids 200, 201 23. The lachrymal fluid 201, 202, 203 24. The eyeball 203, 204 25. The iris 205, 206 26. The retina 206, 207, 208, 209 27. The crystalline lens 209, 210 28. Uses of the lens 210, 211, 212 29. Long and short sight 212, 213 30. Function of accommodation 213, 214 31.