THE TYMPANUM. 443 



2. The Tensor Tympani is placed in the canal just above 

 the Eustachian tube. It arises from the posterior extremity of 

 the cartilaginous portion of the latter, and having got into the 

 tympanum, is changed into a small tendon, which, going out- 

 wardly, is inserted into the neck of the malleus, just beloW'its 

 processus gracilis. 



It draws the malleus inwardly; consequently makes tense 

 the membrana tympani, and drives the stapes into the fenestra 

 ovalis. 



3. The Stapedius arises from the bottom of the cavity in the 

 pyramid, and terminates in a small round tendon, which, going 

 through the apex of the latter, is inserted into the head of the 

 stapes. 



It draws the stapes backwards, and perhaps fixes it more 

 firmly by its contractions. 



4. There is a fourth muscle mentioned by anatomists, the 

 existence of which is more equivocal; it is called the Laxator 

 Tympani Minor. It is said to arise from the superior margin 

 of the orifice of the tympanum, and to be inserted into the pro- 

 cessus brevis of the malleus. It is by some considered only as 

 a ligament, to which opinion I am inclined. 



Of the Lining Membrane of the Tympanum. 



This membrane is a continuation of the lining membrane of 

 the pharynx, being introduced into jhe tympanum through the 

 Eustachian tube. It covers completely the surface of the tym- 

 panum, and is reflected over its little bones so as to give them 

 a covering also; in addition to which, it lines such of the mas- 

 toid cells as communicate with the tympanum.* 



This membrane is extremely delicate: on its surface, adja- 

 cent to the bones, it is somewhat fibrous, and thereby resem- 

 bles periosteum; but the other surface has the characters of the 

 mucous membranes generally, in the nature of its secretion, 

 and in its vascularily, which is very strongly marked in in- 

 flammations, and by fine injections. Bichat mentions, that in 

 certain catarrhal affections its mucous secretion is so abundant 



