THE EAR 1545 



inwards the handle of the malleus, and, along with it, the mem- 

 brane. 



Stapedius — Origin. — The wall of the canal within the pyramid, 

 and of the continuation of this canal in front of the descending 

 part of the aqueduct of Fallopius. 



The tendon emerges from the canal withia the pyramid through, 

 a small orifice on the apex. 



Insertion. — The posterior aspect of the neck of the stapes. 



Nerve-supply. — The facial nerve. 



Action. — ^To draw the head of the stapes backwards. The result 

 is that the front part of the foot-piece of the stapes is tilted away 

 from the vestibule, and its back part is pressed inwards towards 

 the vestibule. 



Movements of the Ossicles. — ^The malleus and incus move simul- 

 taneously, the movement being one of rotation round an axis 

 extending from the tip of the long process of the malleus to the 

 tip of the short process of the incus. During the action of the 

 tensor tympani muscle, when the handle of the malleus and the 

 membrana tympani are drawn inwards, the long process of the incus 

 is pushed inwards, and the stapes is thereby pressed inwards. The 

 result is that the foot-piece of the stapes presses upDn the peri- 

 lymph of the labyrinth, and the secondary- membrane of the 

 tympanum is pressed outwards. Probably the stapedius tends 

 to prevent undue pressure upon the perilymph of the labyrinth 

 during strong contraction of the tensor tympani by the tilting 

 action already ascribed to it. 



Mucous Membrane of the Tympanum. — ^The tympanic mucous 

 membrane is continuous anteriorly with that of the naso-phar^Tix 

 through the Eustachian tube. Posteriorly it is prolonged into the 

 mastoid antrum, and thence into the mastoid cells. It forms the 

 internal layer of the membrana t\^mpani, and the external layer 

 of the secondary membrane of the tympanum. It also furnishes 

 sheaths for the tendons of the tensor tympani and stapedius 

 muscles, and for the chorda tympani ner\'e. Two folds extend 

 downwards from the roof of the attic or epitympanic recess, one 

 in front of, and the other behind, the superior ligament of the 

 malleus. The former is connected with the head of the malleus, 

 and the latter (sometimes described as the superior ligament of 

 the incus) with the incus. 



Attic or Epitympanic Recess, and its Pouches. — ^The part of the 

 tympanic cavity which lies above the level of the upper margin 

 of the membrana tympani is called the attic or epitympanic 

 recess, as distinguished from the atrium or tympanum proper. 

 It contains the head and neck of the malleus, and the body and 

 short process of the incus. These di\'ide it incompletely into two 

 compartments — outer and inner. The outer attic is subdivided 

 into t\vo pouches — superior and inferior. The superior pouch is 

 partially separated from the inner attic by the two mucous folds 

 which have been already referred to as descending from the roof 



