200 



PHYSIOLOGY 



CHAP. 



The chain of ossicles consisting of the malleus, incus, and 



stapes (Fig. 77) makes the ana- 

 tomical connection between the 

 membrana tympani and the fenestra 

 ovalis, and forms a single apparatus 

 I'nr receiving the aerial vibrations 

 and transmitting them to the fluid 

 of the labyrinth. 



The handle (manubrium) of the 

 malleus is firmly united by fibrous 

 tissue to the tympanic membrane 

 (Fig. 78). This ossicle is further 

 ma fixed by two ligaments, one anterior, 



FIG. 77. The chain of auditory ossicles, the other posterior, which confine 

 to' 1 mal toaw'tvin in *^ brium a 'ttn? ied ^' s 111()V 6nients, and only permit it 

 articulating with in. -us : ,.. cervix t< > make slight excursions from with- 



pr.gr., proivs>u> <_nacilis 01 lateialK . P . . , , . 



partiaih converted i.. adults into iiga out inwards in an axis through its 



jiient : /.. Incus, forming an amphi ,,,,,,].. unfU.-if when the Ivnifllp fines 



arthrosis uith hea.i of maiieus: co. pecK, so mat w iu n me Handle iact 

 body; pr.6r., processus brevis; r.i inwards its head moves in the 



processns iiuiuus capped by the lent! . ,. 



ctllar process; /(./. ., foi ai t iciilat ion ( IppOSltC dirCCtlOll. 



with head of stupe.-, : >.. --tapes with rrri 1 ] 4-1,^ 



cavity for ai ticulation. a .short neck, Ifie inCUS IS attaClleU tO U1C 



ftnestra ra vi5te d : ' tos ' '' ui " K '"'" Th tympanic cavity by a ligament in- 

 serted on to its short process. It 



articulates with the head of the malleus by a saddle-joint, with a 

 very thick fibrous capsule. At the 

 lower edge of its articular head 

 the malleus forms a kind of spur 

 which, when the manubrium moves 

 forward, makes with the incus a 

 single, rigid piece, called by Weber 

 the angular lever, which moves 

 round the common axis formed by 

 the ligaments of the malleus. The 

 rotation of the two ossicles round 

 this axis takes place in a plane 

 vertical to that of the membrana 

 tympani. As the long process of 

 the incus is about shorter than 

 the handle of the malleus the ex- 

 cursions of its end must be corre- 

 spondingly smaller and more 

 powerful. 



The stapes is attached by an 

 almost rigid articulation to the 

 tip of the lenticular process of the 

 incus, so that the excursions of the latter are transmitted to the 

 fenestra ovalis, with which the stapes is connected. The excur- 



Fn.. 78. Membrana tympani attache I io 

 malleus viewed from the inner .surface. 

 (Xu^'l-) 1, Chorda tympani passing 

 through tympanic cavity ; 2, Eustachian 

 tube ; 3, insertion of tendon of tensor 

 tympani ; s.t.p., spina tympanicii posterior ; 

 pf.br., short process of malleus; l.m.ti.. 

 anterior ligament of malleus; m., head; 

 ma., manubrium ailheit-nt to membrana 

 tympani. 



