SENSE OF HEARING. 



603 



The manubrium or handle is attached to the membrana tympani. 

 The processus gracilis is attached to the Gasserian fissure by bone 

 and ligament. The processus brevis presses against the membrana 

 flaccida, and its location is visible by inspection of the external 



FIG. 382. The incus of the right side: A, anterior face; B, internal face: 1, 

 body of incus; 2, processus brevis; 3, processus longus; 4, articular surface for the 

 malleus ; 5, a convex tubercle, processus lenticularis, for articulation with stapes ; 6, 

 rough surface for attachment of the ligament of the incus (after Testut). 



surface of the membrana tympani, through which it shows (Fig. 

 379). The malleus is held in place by ligaments (Fig. 384). 



Incus (Fig. 381). This is called also ambos and anvil-bone. 

 The body is characterized by the presence of an articular surface 

 for articulation with the malleus. It has two processes processus 

 brevis and processus longus. The processus brevis is attached by 

 ligament to the margin of the opening that leads into the mastoid 

 cells. The processus longus is nearly parallel with the handle 



FIG. 383. The stapes: 1, 

 base ; 2, anterior crus ; 3, pos- 

 terior crus ; 4, articulating 

 surface of head of the bone ; 

 5, cervix or neck (after Tes- 

 tut). 



f 



FIG. 384. Ligaments of the ossicles and 

 their axis of rotation. The figure represents 

 a nearly horizontal section of the tympanum, 

 carried through the heads of the malleus and 

 incus : M, malleus ; I, incus ; t, articular tooth 

 of incus ; Ig.a. and Ig.e, external ligament of 

 malleus; Ig.inc, ligament of the incus; the 

 line a-x represents the axis of rotation of the 

 two ossicles (from Foster, after Testut). 



of the malleus and ends in a round projection, os orbicular e or 

 lenticular process, which articulates with the head of the stapes. 

 During fetal life the os orbiculare exists as a separate bone. 



Stapes (Fig. 383). This bone is so called from its resemblance 



