SENSE OF HEARING. 



605 



remains so throughout the rest of its course. It is lined by 

 mucous membrane, the epithelium of which is ciliated. The direc- 

 tion of the motion of these cilia is from the tympanum to the 

 pharynx, so that the secretion of the membrane lining the tym- 

 panum will escape into the pharynx. Its opening in the pharynx 

 is ordinarily closed, except during the act of swallowing, when it 

 momentarily opens ; or it may be made to open by closing the 

 mouth, holding the nostrils closed with the thumb and finger, and 

 forcibly blowing. The pharyngeal opening is at the upper lateral 

 part of the pharynx behind the inferior turbinated bone. There 



Portion of Eusta 

 chian tube fre 

 from glands. 



Cartilage 



Mucosa of the 

 pharynx. 



Glands. 



FIG. 385. Cross-section of the Eustachian tube with its surrounding parts ; X 12 

 (from a preparation by Professor Eiidinger). 



is a band of muscular tissue, the dilatator tubce, which joins the 

 tensor palati. 



Mastoid Antrum. This is a cavity which opens into the attic 

 or epitympanic recess, an extension upward and backward of the 

 tympanic cavity. It is in this recess that the head of the malleus 

 and a part of the incus are situated. The antrum communicates 

 with the mastoid cells in the mastoid process. Antrum and cells 

 are lined by mucous membrane which is continuous with that of 

 the tympanum. This extension of the mucous membrane explains 

 how inflammation of the middle ear may extend to the mastoid 

 cells. 



Fenestra Ovalis (Fig. 386). This is an oval opening in the 

 internal wall of the tympanum into the vestibule of the internal 



