1540 



A MANUAL OF ANATOMY 



muscle) ; and (4) the iter chordae posterius, for the passage of the 

 chorda tympani nerve. 



Membrana Tympani. — ^This is the membrane which closes the 

 inner extremity of the meatus auditorius externus. It is situated 

 on the outer wall of the tympanum, of which it forms the chief part, 

 and it is set, for the most part, in the sulcus tympanicus, which 

 marks the inner surface of the tympanic annulus. Superiorly, 

 however, where the annulus is deficient, the membrane is attached 

 to the notch of Rivini. This part of it is thinner and looser than the 

 rest, and is called the membrana flaccida, or Shrapnell's membrane. 

 The attachment of the membrana tympani to the sulcus tympanicus 

 'is effected by means of a thickened band of fibres, disposed in the 

 form of a ring, called the annulus fibrosus. This annulus passes 



Superior Ligament of Malleus 



Head of Malleus 

 Insertion of Tensor Tympani 



Chorda Tympani Nerve ' 



Eustachian Tube--— 



Superior Ligament of Incus 

 Body of Ijicus 



/T 



^^Attic of Tympanum 



I Short Process of 

 -*" Incus 



'■''A'd f Long Process of 



Incus 

 _. Processus Orbicu- 

 y & ; laris of Incus 



Handle of Malleus 



Membrana Tympani 



Fig. 645. — The Right Membrana Tympani, Malleus, and Incus 

 (Internal, Posterior, and Superior View) (Spalteholz). 



from the extremities of the notch of Rivini to the short process of 

 the malleus in the form of two bands, which are known as the 

 anterior and external malleolar ligaments, and which form the lower 

 boundary of the membrana flaccida. Opposite the notch of Rivini 

 these annular fibres separate the membrana flaccida from the rest of 

 the membrana tympani. The membrane is set obliquely in the 

 sulcus tympanicus, so that its lower part forms an acute angle with 

 the floor of the meatus auditorius externus, and its upper part an 

 obtuse angle with the roof of the passage. 



The membrana tympani is somewhat oval. In the vertical 

 direction it measures about 10 mm., and horizontally from 8 to 

 9 mm. The handle of the malleus lies between the mucous and 

 fibrous layers of the membrane, and descends to a point a little 

 below its centre, where it ends in a small knob, from which the radi- 



