276 SPECIAL ANATOMY. 



Its longer, thinner process, passes parallel with manubrium mallei internal to 

 and behind it (chorda tympani between the two). On its hooked apex, which 

 is bent backwards, we find the ossiculum lenticulare Sylvii, a tubercle, which 

 is almost always united with the incus. It is situated freely in the tympanic 

 cavity. From its apex passes inwards to the fenestra ovalis. 



c. The Stirrup, stapes, horizontally, at a right angle. Its capitulum unites 

 with the ossicul. lenticulare; from it passes off inwards an anterior and a pos- 

 terior crus (on the concave surfaces of which, turned to one another, we find a 

 groove, sulcus stapedis), which become associated by a thin plate, the foot 

 piece (basis stapedis}. This basis passes directly into the fenestra ovalis, in 

 which it moves. 



Muscles of the ossicula. Sommerring admits four muscles, three of which 

 belong to the malleus, one to the stapes ; distinct muscular tissue is, however, 

 only found in the 



M. tensor tympani s. mallei internus. Or. : from the superior wall of the 

 cartilaginous tuba Eustachii and from the Sphenoid bone (behind foram. 

 spinosum}. Course: backwards in the osseous canal above the tuba, 

 enters into the cavity of the tympanum, where the tendon is reflected at, 

 almost, a right angle. Ins. : the anterior superior part ofmanubr. mallei. 

 Use : to draw the malleus inwards, and stretch the memb. tympani. 

 To the ligaments of the ossicula belong therefore, besides the capsular liga- 

 ments between malleus and incus, and between os lenticulare and stapes : 



1. Lig. mallei capituli s. superius passing from the superior wall of the 

 tympanum to the head of the malleus. 



2. Lig. mallei manubrii s. posterius (laxator tympani minor} ; passing from 

 the internal extremity of the auditory meatus, upwards and backwards, 

 to the manubrium. 



3. Ligg. processus longi anterius 8. mallei (laxator tympani major s. malleus 

 externus}, passes from proc. spinos. (of the sphenoid bone) through Jissura 

 Glaseri to the apex of proc. folianus. 



4. Lig. processus longi et brevis incudis come from the posterior and exter- 

 nal wall of the cavity of the tympanum. 



5. Lig. stapedis (muse, stapedius) ; very thin; arises inside the eminentia 

 papillaris, passes out of it into the tympanum, passes forwards and down- 

 wards, and is attached behind to the capitulum of the stapes ; it is said to 

 draw the stapes backwards, and thereby to press the posterior part of its 

 basis deeper into the fenestra ovalis, whilst the anterior part is raised. 

 The same thing happens when the tensor tympani draws the head of the 

 malleus backwards, and imparts the movement to the remaining ossicula. 



511. 3. The Trumpet of the Ear, Tula Eustachii, 



a straight canal, about two inches long, flattened at the sides, be- 

 tween the inferior anterior part of the tympanum and superior 

 lateral part of the pharynx, passing in an oblique direction from 



