THE SENSE OF HEARING. 



167 



bone presents a concave, articular surface, which receives the head of the 

 malleus; the stapes, or stirrup bone, articulates externally with the long pro- 

 cess of the incus, and internally, by its oval base, with the edges of the fora- 

 men ovale. 



The tensor tympani muscle consists of a fleshy, tapering portion, half 

 an inch in length, which terminates in a slender tendon ; it arises from the 



11 



TYMPANUM AND AUDITORY OSSICLES (LEFT) MAGNIFIED. 



A.G., external meatus ; M, membrana tympani, which is attached to the handle of the 

 malleus, n, and near it the short process, /; h, head of the malleus; a, incus ; k, its 

 short process with its ligament ; /, long process ; s, Sylvian ossicle ; S, stapes ; A.X, 

 A-r, is the axis of rotation of the ossicles ; it is shown in perspective, and must be 

 imagined to penetrate the plane of the paper ; t, line of traction of the tensor tympani. 

 The other arrows indicate the movement of the ossicles when the tensor contracts. 



cartilaginous portion of the Eustachian tube and adjacent surface of the 

 sphenoid bone. From this origin the muscle passes nearly horizontally 

 backward to the tympanic cavity ; just opposite to the fenestra ovalis its 

 tendon bends at a right angle over the processus cochleariformis and then 

 passes outward across the cavity to be inserted into the handle of the mal- 

 leus near the neck. 



