Chap. 40. ~| Structure of the Internal Ear. 379 



legs of the ftapes are bent nearly into a circle, and 

 where they unite at the bafis, cover th,' fc- "lira ovalis. 

 The ftapes is -fituated in a part of the .ymn;- -im, 

 feparated from the other parts by a particular a., . 

 brane. 



The ftapes and malleus are each of then: furnifhed 

 with a little mulcle, called, from the bones tawhicn they 

 belong, ftapedius and tenfor tyrnpani. The firft of thefe, 

 which is the fmalleft diftinft mufcle in the body, arifes 

 from a little cavity at the poflerior and upper part of 

 the cavity of the tympanum, and its tendon is inferted 

 at the back part of the head of the ftapes. This 

 mufcle, which draws the ftapes obliquely upwards, 

 aflifts in ftretching the membrana tympani. The 

 other mufcle is more remarkable, and as it operates 

 like the former in ftretching the membrana tympani, 

 has more particularly obtained the name of tenfor 

 tympani. It arifes from the cartilaginous extremity of 

 the Euftachian tube, and is inferted into the back part 

 of the handle of the malleus, which it helps to pull 

 inwards, and by that means to ftretch the membrana 

 tympani. 



That part of the ear which is fituated behind the 

 tympanum is called the labyrinth. The labyrinth is 

 feparated from the tympanum by a bony partition^ 

 and only communicates with it by means of two 

 openings of nearly equal fize, one of which is the 

 feneftra ovalis, which is fhut by the bafe of the ftapes, 

 the other the feneftra rotunda, which is clofed by a 

 continuation of the membrane which lines the "cavity 

 of the tympanum. 



In the labyrinth of the ear are fituated the veftibule, 

 the three femi-circular canals, and the cochlea. 



The veftibule or porch is a cavity of an irregular 

 round! (h form, and is placed nearly in the center of 



the 



