428 PRACTICAL ANATOMY. 



The stapes, or stirrup, presents a head, neck, two 

 branches, and an oval-shaped base, which is applied to 

 the fenestra ovalis. The ossicula are articulated and 

 held together by capsular ligaments. The joints are 

 covered by cartilage and lined by synovial membranes. 

 They are also attached to the walls of the tympanum by 

 delicate, ligamentous bands, and are moved by the three 

 muscles : 

 TENSOR TYMPANI. 



Origin Petrous portion of temporal bone. 

 Insertion Runs backward in the canal above the 

 processus cochleariformis and terminates in a tendon, 

 which is inserted into the root of the handle of the 

 malleus. 

 LAXATOR TYMPANI. 



Origin From the spine of the sphenoid. 

 Insertion Runs backward through the Glaserian fis- 

 sure, and is inserted on the neck of malleus above 

 the processus gracilis. 

 STAPEDIUS. 



Origin From within the pyramid. 

 Insertion Neck of stapes. 



The mucous membrane is reflected over the different 

 structures within the tympanum. 



THE INTERNAL EAR. 



The internal ear consists of the osseous and mem- 

 branous labyrinth. The osseous labyrinth contains the 

 vestibule, semicircular canals, and cochlea. The mem- 

 branous labyrinth presents the utricle, saccule, and 

 membranous cochlea and semicircular canals. The os- 

 seous labyrinth is developed in the substance of the 

 petrous portion of the temporal bone. 



The cochlea is in front ; the vestibule is the central 



