XI 



THE EAR 



In birds, the ear does not form any external 

 appendage to the head. An opening, sur- 

 rounded by a fringe of feathers, leads into a 

 canal which ends at the tympanic membrane, 

 a thin partition separating the external passage 

 from the tympanic cavity. The tympanum, 

 or drum of the ear, is an irregular cavity in 

 the temporal bone placed in communication 

 with the throat by the auditive or Eustachian 

 tube, which opens in common with its fellow 

 of the opposite side of the head. Across the 

 tympanic cavity stretches a rod-like bone, the 

 columella, one end of which is in contact with 

 the tympanic membrane, while the other, 

 somewhat expanded and disc-hke, fits into 

 an oval opening, the fenestra vestibuli, in the 

 inner wall of the cavity. 



101 



