THE MIDDLE EAR 717 



tween the long process of the incus and the stapes ; but this is seldom 

 distinct, usually being united either with the incus or with the stapes. 



There are two well-defined muscles connected with the ossicles of 

 the middle ear. One of these is attached to the malleus, and the other, 

 to the stapes. The so-called laxator tympani probably is not composed 

 of muscular fibres and should not be enumerated with the muscles of 

 the tympanum. 



The larger of the two muscles is the tensor tympani. Its fibres 

 arise from the cartilaginous portion of the Eustachian tube, the spinous 

 process of the sphenoid bone and the adjacent portion of the temporal. 

 From this origin it passes backward, almost horizontally, to the tym- 

 panic cavity. In front of the fenestra ovalis it turns at nearly a right 



Fig. 186. Ossicles of the tympanum, X 4 (modified from Riidinger). 



I, ossicles of the left ear; i, malleus; 2, incus; 3, stapes. II, ossicles of the right ear; i, malleus; 

 2, long process; 3, handle; 4, long process of the incus; 5, short process of the incus; 6, stapes. 



angle over a bony process, and its tendon is inserted into the handle of 

 the malleus at its inner surface near the root. The tendon is very deli- 

 cate, and the muscular portion is about half an inch (12.7 millimeters) 

 in length (10, Fig. 185). The muscle and its tendon are enclosed in 

 a distinct fibrous sheath. The action of this muscle is to draw the 

 handle of the malleus inward, pressing the base of the stapes against 

 the membrane of the fenestra ovalis and producing tension of the 

 membrana tympani. The fibres of this, and of all the muscles of the 

 middle ear, are of the striated variety. The tensor tympani is supplied 

 with motor filaments from the otic ganglion, which probably are derived 

 from the facial nerve. 



The stapedius muscle is situated in the descending portion of the 

 acquaeductus Fallopii and in the cavity of the pyramid on the posterior 

 wall of the tympanic cavity. Its tendon emerges from a foramen at 



