674 TIIE SENSE OF HEARING. 



cutaneous lining of the auditory canal, its inner surface 

 with, part of the ciliated mucous membrane of the tym- 

 panum. 



The small bones or ossicles of the ear are three, named 

 malleus, incus, and stapes. The malleus, or hammer-bone, is 

 attached by a long slightly -curved process, called its 

 handle, to the membrana tympani ; the line of attach- 

 ment being vertical, including the whole length of the 

 handle, and extending from the upper border to the centre 

 of the membrane. The head of the malleus is irregularly 

 rounded ; its neck, or the line of boundary between it and 

 the handle, supports two processes ; a short conical one, 

 which receives the insertion of the tensor tympani, and a 

 slender one, processus gracilis, which extends forwards, and 

 to which the laxator tympani muscle is attached. The incus, 

 or anvil-bone, shaped like a bicuspid molar tooth, is 

 articulated by its broader part, corresponding with the 

 surface of the crown of a tooth, to the malleus. Of its 

 two fang-like processes, one, directed backwards, has a 

 free end, the other, curved downwards and more pointed, 

 articulates by means of a roundish tubercle, formerly 

 called os orbiculare, with the stapes, a little bone shaped 

 exactly like a stirrup, of which the base or bar fits into 

 the fenestra ovalis. To the neck of the stapes, a short 

 process, corresponding with the loop of the stirrup, is 

 attached the stapedius muscle. 



The bones of the ear are covered with mucous mem- 

 brane reflected over them from the wall of the tympanum ; 

 and are moveable both altogether and one upon the other. 

 The malleus moves and vibrates with every movement and 

 vibration of the membrana tympani, and its movements 

 are communicated through [the incus to the stapes, and 

 through it to the membrane closing the fenestra ovalis. 

 The malleus, also, is moveable in its articulation with the 

 incus; and the membrana tympani moving with it is 

 altered in its degree of tension by the laxator and tensor 



