THE SENSES 



839 



a kind of bent lever, by which the oscillations of the membrana 

 tympani are transferred to the membrane covering the oval foramen, 

 and at the same time reduced in size. Two slender muscles, the 

 tensor tympani and stapedius, contained in the tympanic cavity are 

 also connected with and may act upon the ossicles. The former lies 



FIG. 324. DIAGRAM OF RIGHT MEMBRANOUS LABYRINTH (SEWALL, AFTSR 



TESTUT). 



i, utricle ;*2, 3, 4, superior, posterior, and horizontal semicircular canals ; 5, saccule ; 

 6, ductus endolymphaticus arising by two branches, 7, 7' ; 8, saccus endolymphaticus ; 

 9, canalis cochlearis (canal of the cochlea), ending at 9', and 9" ; 10, canalis reuniens. 



in a groove above the Eustachian tube, and its tendon, passing round 

 a kind of osseous pulley (processus cochleariformis), is inserted into 

 the handle of the malleus ; the stapedius is lodged in a hollow of the 

 inner bony wall of the tympanum. Its tendon is attached to the neck 



'Meissntr's membrane 



Seal a Vesttbuli 



s ccchleae 



t* c tor i a 



. 



*cciJct Tymnant X J|/ 



FlG 325. TRANSVERSE SECTION OK A TURN OF THE COCHLEA (DIAGRAM- 



MATIC). 



of the stapes near its articulation with the incus. This inner wall is 

 pierced not only by the oval foramen, but also by a round opening, 

 the fenestra rotunda, which is closed by a membrane to which the 

 name of secondary membrana tympani is sometimes given. 



