THE MIDDLE EAR. 



[499 



3. The lateral ligament of the malleus is somewhat fan-shaped and extends between the 

 roughened neck of the malleus and the external wall of the tympanum above the Rivinian notch. 

 The posterior fibres of this ligament are called the posterior ligament of the malleus ( Helmholtz) , 

 and, together with the fibres of the anterior ligament lying in the same plane, form the "axis- 

 ligament of the malleus," since the axis on which the malleus turns passes through the attach- 

 ment of these two fibrous structures. 



4. The posterior ligament of the incus extends from the apex of the short process of the 

 incus to the tympanic wall at the lower part of the mouth of the antrum. It is fan-shaped, the 

 incudal attachment being less extensive than that of the tympanic. The superior ligament 

 of the incus is variable and consists chiefly of a fold of mucous membrane. 



The Intratympanic Muscles. — The muscles within the tympanum connected with thg 

 ossicles (musculi ossiculorum auditus) are : (i) the iensor tyinpani axid (2) the stapedius. 



The tensor tympani is a diminutive spindle-shaped muscle, about 1.25 cm. long, lying in the 

 bony canal directly above the osseous part of the Eustachian tube, from which it is partly 



Fig. 1259. 



Facial uerv-e 



Secondary tytn- 

 panic membrane 



Ramus utriculus 

 ampulla ris 



Utricle 



Foot of stapes i: 



Cisterna peri- »fl 

 lymphatica ■■, 



Lowest part of _}J^ 

 spiral lamina "^^^ 



Beginning of '^\( /y.^'V-^^ 



posterior ^"vj^ ^ ' 



ampulla "^' ' 



Stapedius 

 muscle 



External 

 auditory canai 



\ ~''^ Handle of 

 malleus 



Promontory 



Drum-head or 



tympanic 



membrane 



Tympanic cavity 



N ^fl^^^ -.. 



Vertical section through human middle and internal ear. X 5^. Drawn from preparation made by Dr. Ralph Butler. 



separated by the bony scroll, the processus cochlearifonnis. The posterior fibres arise from 

 the top of the cartilage of the Eustachian tube and the adjoining part of the great wing of the 

 sphenoid. Some of the fibres are connected with the tensor palati muscle and others arise 

 from the wall of the canal which the muscle occupies. The fibres converge in a feather-like 

 manner to the tendon, which begins within the muscle about the middle of the canal, and, pass- 

 ing through the tympanic opening of the canal, turns at nearly a right angle over the end or 

 rostrum of the processus cochleariformis to be inserted into the anterior part of the inner 

 margin of the malleus-handle just below the short process. The tendon is almost per- 

 pendicular to the plane of the tympanic membrane, is oblique to the long axis of the manu- 

 brium and is enveloped, along with the muscle-belly, in a fibrous sheath. The tensor tympani 

 and tensor palati muscles receive their nerve supply from the same source, namely, the trigem- 

 inus, through the otic ganglion. ^ 



The stapedius muscle lies within the triangular canal of the eminentia pyramidalis, arising 

 from its floor and sides. Its fibres converge to the tendon, which, passing through the opening 

 at the apex of the canal, extends forward, slightly upward, and outward, to be inserted into the 

 lower posterior part of the head of the stapes. Some of the fibres of the tendon also pass to the 



