THE AUDITORY OSSICLES. 93 



existence of muscular tissue in this situation. Many of the fibres of the anterior 

 Hiram ent take origin from a bony prominence which projects from the margin of 

 the external meatus into the tympanum, and forms the anterior boundary of the 

 notch of Rivinus. This prominence is known as the anterior spinous process of the 

 tympanum (spina tympanica anterior) (fig. 101, sp) to distinguish it from another 

 smaller bony prominence or spine at the posterior extremity of the notch (see p. 81 ). 



Arri'xxort/ tintcr'nir lit/iDiH'nt. A comparatively stout sheath surrounds the tendon of the 

 tensor tympani as it passes from the end of the cochlearifonn process to the malleus, and a 

 flat ligamentous band with a thickened margin (fig. 101. /). which lies along 1 the anterior 

 border of this sheath, stretching- between the anterior wall of the tympanum and the upper 



Fig. 101. VlK\V OF THE CAVITY OK THE 



JO'f O ?/ S( 



TY.Ml'AM M. OPENED FROM ABOVE. 



(Magnified four times.) (E. A. S.) 



m, head of the malleus ; sp, spina 

 tympanica anterior ; I. a. m, anterior 

 ligament of the malleus ; Lc.ni, external 

 ligament of the malleus ; Ji, gap between 

 the two ligaments leading to the mem- 

 brana flaccida and notch of Rivinus ; i, 

 body of the incus ; I. i, posterior ligament 

 of the incus ; pr. o, processus orbicularis 

 of the incus seen in the depth of the 

 cavity, articulated with the head of the 

 stapes, at ; st', tendon of the stapedius 

 muscle emerging from the pyramid ; tt, 

 tendon of the tensor tympani, emerging 



from the conical end of its canal ; I, thickened edge of a flattened band of ligamentous fibres which lies 

 in the fold of the mucous membrane, m.m., and assists in fixing the malleus ; . I. m, superior ligament of 

 the malleus, cut short ; n, chorda tympani nerve. 



part of the manubrium and neck of the malleus, may be regarded as assisting in the fixation 

 of the malleus anteriorly. Toynbee described the sheath in question as acting as an accessory 

 ligament (tensor ligament). 



The external ligament of the malleus (fig. 101, l.e^n.), is a fan-shaped ligamentous 

 structure, the fibres of which arise from the margin of the notch of Rivinus, and 

 converge to the short process and adjacent part of the malleus. 



The posterior bundle of fibres of this ligament, together with the anterior bundle of the 

 anterior ligament are termed by Helmholtz the "axis-ligament of the malleus," since they are 

 attached nearly in the axis of rotation of that bone. 



The superior ligament of the malleus (figs. 101, loi, s.l.m.) consists of a 

 small bundle of fibres, which passes downwards and outwards from the roof of 

 the tympanum to the head of the malleus, and serves to check the outward move- 

 ments of the manubrium and membrona tympani. 



Inferior liija iiu-nt of tin- titnUetat. A small bundle of ligamentous fibres is occasionally found 

 passing from near the extremity of the handle of the malleus upwards and backwards behind 

 the long process of the incus, to be attached to the outer wall of the tympanum. This liga- 

 ment assists the external ligament in resisting a too violent action of the tensor tympani 

 muscle, and it serves also to restrict any rotating action which that muscle may tend to exert 

 upon the malleus. 



The ligament of the incus (figs. 90, 101, Li.) extends from near the point of the 

 short crus backwards towards the posterior wall of the tympanum, but some of its 

 fibres spread also outwards and inwards. It is attached below the entrance to the 

 mastoid cells. 



Muscles. There are only two well-determined muscles of the tympanum. 

 Sormnerring described four, and some authors have mentioned a larger number ; but 



