THE MIDDLE EAR 691 



ward, the muscle makes its exit at the apex of the pyramid, and is di- 

 rectly inserted into the neck of the stapes close to the articulation 

 of the orbicular process of the incus. , 



The ligaments of the malleus are the anterior, the external, and 

 the superior. The anterior ligament firmly attaches the head of the 

 malleus to the margin of the Glaserian fissure in the anterior wall of 

 the tympanum. The processus gracilis of the malleus is inclosed by 

 the fibers of this ligament. It is also in close relation with the chorda 

 tympani nerve, which, being clothed by the tympanic mucosa, trav- 

 erses this portion of the tympanic cavity and enters the iter chordae 

 anterius. 



The external ligament connects the neck of the malleus with the 

 upper portion of the external wall of ^he tympanum. It is somewhat 

 fan-shaped. The space lying between the external ligament of the 

 malleus and the membrana flac'cida is known as Prussak's space. The 

 superior ligament is a looser fibrous band which passes from the head 

 of the malleus to the superior wall of the tympanum. 



The ligament of the incus is decidedly fan-shaped, its straight, coarse, 

 fibrous bands radiating from the short process of the ossicle to the ad- 

 jacent portion of the posterior wall of the tympanum. 



The articulation of the malleus with the incus, as also that of the 

 latter bone with the stapes, is supplied with a delicate capsular liga- 

 ment. 



The annular ligament of the stapes connects the margin of the 

 foot plate of this bone with the adjacent portions of the cartilaginous 

 and bony wall of the vestibule at the margin of the fenestra vestibuli. 

 The articulation which is thus inclosed is directly formed by an an- 

 nular plate of cartilage investing the margin of the oval foot of the 

 stapes, and a similar annular plate of hyaline cartilage which lines the 

 borders of the foramen vestibuli. The fibers of the annular ligament 

 are continuous with those of the perichondrium and adjacent periosteum. 



THE AUDITORY (EUSTACHIAN) TUBE 



The auditory or Eustachian tube connects the cavity of the tym- 

 panum with that of the nasopharynx. Its first portion, including 

 about one-third of its entire length, is surrounded by a bony wall; be- 

 yond this it is supplied with a cartilaginous plate ; its pharyn^eal ostium 

 is entirely membranous. 



The mucosa consists of an entodermal epithelium, which is of the 



