820 



SPECIAL SENSES. 



by its smaller extremity with the long process of the incus. Its base is oval (0*, Fig. 



259) and, with its annular ligament, is applied to the fenestra ovalis. The direction of 



the stapes is nearly at a right angle with the 

 long process of the incus in the natural state 

 (8, Fig. 260). 



There are three well-defined muscles con- 

 nected with the middle ear. Of these, two are 

 attached to the malleus, and one, to the stapes. 

 The largest of the three muscles is the tensor 

 tympani, called sometimes the internal muscle 

 of the malleus. Its fibres arise from the carti- 

 laginous 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 tympanic cavity. In front of the fenes- 

 tra ovalis, it turns, nearly at a right angle, over 

 a bony process, and its tendon is inserted into 



FIG. 259. Ossicles of tht 'tympanum of the right * . 



tide ; magnified 2 diameters. (Arnold.) the handle of the malleus at its inner surface 

 A, malleus; i, its head; 2, the handle; 3, long, or near the root. The tendon is very delicate, 



slender process; 4, short process; B, incus; 1, its J 



body; 2, the long process with the orbicular pro- and the muscular portion is about halt an inch 



in length (10, Fig. 258). 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 inem- 

 brana 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 are probably derived from the facial nerve. 



cess ; 3, short, or posterior process ; 4, articular 

 surface receiving the head of the malleus; C, 

 stapes; 1, head; 2, posterior crus; 3, anterior 

 crus ; 4, base ; C*, base of the stapes ; D, the three 

 bones in their natural connection as seen from the 

 outside; a, malleus; &, incus; c, blcpes. 



FIG. 260. The right temporal bone, the petrosal portion removed^ showing the ossicles seen from within. From 



a photograph. (Rudinger.) 



inSi^frpp - *? P r CeS8of whichis directed nearly in an horizontal direction backward; 5, the long processor the 



ono^raM \ of , tym P amc o^ty, articulated with the stapes; 6, the malleus, articulated with the incus; 7, the 



I the malleus in the Glasserian fissure ; 8. the stapes, articulated with the incus. This is drawn 



SESiji ? th .t rwise ' the base of the 8ta P es alone would be visible. This figure shows the handle of 



ic malleus attached to the membrana tympani. 



The laxator tympani, the external muscle of the malleus, arises from the spiaous pro- 

 cess of the sphenoid bone and, by a few filaments, from the cartilaginous portion of the 



