THE LARYNX AND THE EAR 



359 



waves that enter the auditory canal. In this way it serves 

 as a receiver of sound waves from the air. It also protects 

 The Middle Ear. The middle ear, or tympanum, 1 con- 

 sists of an irregular cavity in the temporal bone which is 

 lined with mucous membrane and filled with air. It is 



Coch/es 



Evstachian 

 tube 



FIG. 151. Diagram of section through the ear, showing relations 

 of its various parts. (See text.) 



connected with the pharynx by a slender canal called the 

 Eustachian tube. Extending across the middle ear and 

 connecting with the membrana tympani on one side, and 

 with a membrane closing a small passage to the internal 

 ear on the other, is a tiny bridge formed of three small 

 bones. These bones, named in their order from the mem- 

 brana tympani, are the malleus, the incus, and the stapes 

 (Fig. 151). Where the malleus joins the membrane is a 

 small muscle whose contraction has the effect of tighten- 



1 The middle ear is also called the ear drum, and, by the same system of nam- 

 ing, the membrana tympani is referred to as the drum membrane. 



