HEARING; STRUCTURE OF THE EAR 



413 



sound waves. The ear is usually considered under its 

 three divisions: (1) the outer ear; (2) the middle ear; 

 (3) the inner ear. 



The outer ear is a funnel-shaped structure made 

 of cartilage and skin; it is used for the purpose of 

 collecting sound waves. The tube that leads to the 

 middle ear is called the auditory canal. 



Cochlea 



Eustachian 

 Tube 



Fig. 299. 

 Structure of the Ear; Section through the Temporal Bone. 



The middle ear is a hollow in the temporal bone 

 (cf. Fig. 275, 354) ; it is called the ear drum, or 

 tympanum. Between the middle ear and the auditory 

 canal is stretched the membrane (tympanic membrane) 

 which corresponds to the " drum head." A chain of 3 

 small, connecting bones (cf. 354) stretches across the 

 middle ear. The first of them is attached to the 

 tympanic membrane, and the last reaches to the opening 

 of the inner ear. The middle ear is connected with 



