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AUDITORY BIOPHYSICS 



Tensor tympani 



a o 



Ligaments 

 A Anterior 

 S Superior 

 L Lateral 



Fig. VII-8. Detailed scale structure of the attachments of the malleus and 

 tympani. View of left ear. (Stuhlman.) 



long crus lies about parallel to the manubrium of the malleus but behind 

 it. The end of its long crus is turned up at an angle of about 23°. 

 It terminates at the point where it articulates with the head of the stapes 

 in the lenticular process, which is a planoconvex lenslike button with its 

 rounded face set in a shallow socket at the top of the stapes. Its short 

 crus is a compression member set practically at right angles to the face 

 of the malleus-incus articulation. Its blunt end rests in a shallow hole, 

 the fossa incudis of the tympanic cavity. 



The incus is supported by two ligaments. The superior ligament 

 extends from the top of the incus to the roof of the tympanic cavity, and 

 the posterior, which is a short dense ligament attaching the end of the 

 short crus, to the fossa incudis. 



The average mass of this bone was found to be 27.5 ± 2.5 mg (Stuhl- 

 man [1937]). The angle between the short crus and long crus was found 

 to be 85° to 90°. The incus has an average overall height, measured 

 along the axis of the long crus, of 7.0 mm, and a horizontal length 

 through the axis of the short crus of 5.0 mm. Its center of gravity lies 

 5.0 mm above the lenticular process on the axis of the long crus. 



