416 THE ORGANS OF SPECIAL SENSE 



15. What structures are included under the lacrymal apparatus? 



16. How many lacrymal ducts are there and where do they drain? 



17. How do the tears reach the nasal cavity? 



18. Name the coats of the eye-ball. 



19. What muscle controls the diameter of the pupil? 



20. What structure contains the pigment which gives the eye 

 its color? 



21. Where is the vitreous humor found in the eye? The aqueous? 

 The crystalline lens? 



22. Where is the anterior chamber of the eye? The posterior 

 chamber? 



23. What is the function of the retina? 



24. What nerve expands into the retina and when does the 

 nerve enter it? 



25. How many layers of cells in the retina? Which layer of cells 

 is the most important as regards vision? 



26. Name the refracting apparatus of the eye. 



27. What is accommodation as regards vision? What is the 

 function of the lens in relation to accommodation? 



28. What is the function of the iris? 



29. Name the structures concerned in the sense of taste. 



30. Where are the end-organs or taste-buds located? 



31. Name the three divisions of the ear. 



32. How long is the external auditory canal? What is its direc- 

 tion? 



33. Describe the tympanum or middle ear. 



34. Where is the tympanic membrane located? What structure 

 covers its outer and inner surfaces? 



35. Through what tube does the tympanic cavity of the ear 

 communicate with the nasopharynx? 



36. What structures are included under the term internal ear? 



37. What are the divisions of the osseous labyrinth as regard its 

 formation? 



38. Where is the membranous labyrinth located. What fluid 

 does it contain. 



39. What fluid separates the membranous from the osseous 

 labyrinth? 



40. Where is the organ of Corti located? 



41. What relation do the hair cells in the organ of Corti bear to 

 the auditory nerve? 



42. How many ossicles are there in each middle ear? Name 

 them. 



43. In what state must all external stimuli be in to produce the 

 sense of sound. 



44. How do vibrating bodies affect the atmospheric air as regards 

 the sense of sound? 



45. Give a brief description of how the sound waves are con- 

 veyed from the external air to the filaments of the auditory nerve 

 in the organ of Corti. 



