THE EAR 205 



stapedius, are found in the middle ear. The former occupies 

 a small bony canal, placed just above the auditory (Eustachian) 

 tube, and passes backwards to be inserted into the upper end 

 of the handle of the malleus. As the tensor tympani 

 approaches its insertion, it winds round a small bony process, 

 termed the processus cochleariformis, so that, when it con- 

 tracts, it draws the handle of the malleus in a medial direction, 

 and thus increases the normal slight concavity on the lateral 

 surface of the tympanic membrane. In this way the membrane 

 is rendered tense. The muscle receives its nerve-supply from 

 the otic ganglion (p. 70), but it is believed that the fibres 

 originate in the nucleus of the facial nerve and are conveyed 

 to the ganglion by the lesser superficial petrosal nerve (p. 92) 

 (Sahli). 



The stapedius arises within the posterior wall of the middle 

 ear and passes forwards to be inserted into the neck of the 

 stapes. The precise action of the stapedius is somewhat 

 doubtful, but it has been suggested that it is antagonistic to 

 the tensor tympani. On this supposition, it is clear that 

 paralysis of the stapedius will lead to the condition of 

 hyperacousis (p. 80), since the tensor tympani is no longer 

 opposed. The stapedius receives its nerve-supply from a 

 small branch of the facial nerve. This branch arises as the 

 facial nerve descends to reach the stylo-mastoid foramen, and 

 it passes forwards in a minute canal in the posterior wall of 

 the middle ear. 



The Tympanic (Mastoid) Antrum lies in the posterior part 

 of the petrous portion of the temporal bone. It varies some- 

 what in size, but it always communicates with the epitympanic 

 recess (attic) of the middle ear through a passage termed the 

 adituS) which is placed in the upper part of the anterior wall of 

 the antrum. In addition, it communicates, either directly or 

 indirectly, with the air-cells of the mastoid process, and the 

 whole system is lined by a prolongation of the muco-periosteum 

 of the middle ear. 



The relations of the antrum are very similar to those of the 



