46 OUTLINES OF ANATOMY. 



Ligaments of the ossicles : 



Superior ligament of the malleus. 



Anterior ligament of the malleus. 



External ligament of the malleus. 



Ligament of the incus. 

 Muscles of the tympanum : 



Tensor tympani; arises, inserted. 



Stapedius ; arises, inserted. 



Nerves. 

 Mucous membrane of the tympanum : 



(a). 



(^) Obturator ligament of the stapes. 



(0- 

 Vessels and nerves of the tympanum. 



Arteries : 



Tympanic branch. Stylo-mastoid branch. Petrosal branch. 

 Veins. 

 Nerves : 



Tympanic plexus : 



Tympanic branch of glosso-pharyngeal. 



Communicating branch from carotid plexus of sympathetic. 



Great superficial petrosal. 



Small superficial petrosal. 



With a fine saw divide the petrous portion of a temporal bone by a coronal incision passing through 

 the external and internal auditory canals. Also divide, the petrous portion of a temporal bone by a ver- 

 tical incision, from the superior border downward through the middle of the mastoid process. Some 

 idea of the internal ear can be obtained by careful study of these sections. This should be supple- 

 mented by the study of specially prepared specimens, in which the osseous labyrinth has been exposed, 

 and by models and diagrams. 



Internal Ear, or Labyrinth, 916-17-18-19-20. (895-6-7-8-9) 

 Osseous labyrinth : 



Vestibule. Semicircular canals. Cochlea. 

 Vestibule : 



Outer wall, fenestra ovalis. 



Inner wall, fovea hemispherica, aqueductus vestibuli. 



Roof, fovea hemielliptica. 



Openings : Behind. 



In front, apertura scalae vestibuli, by which vestibular 

 cavity communicates with the scala vestibuli of 

 the cochlea. 



Three semicircular Canals, ampulla. 

 Superior semicircular canal. 

 Posterior semicircular canal. 

 External semicircular canal. 

 Cochlea : 



Base ; tractus spiralis foraminulentus. 

 Modiolus, or columella : 



Spiral canal, lamina spiralis, hamulus, heliocotrema. 

 Lamina spiralis. 



Scala vestibuli and scala tympani. 

 Scala vestibuli. 

 Scala tympani. 

 Central axis, or modiolus ; cupula, infundibulum. 



Central canal of the modiolus. 

 Membranous labyrinth: 



Perilymph. Canal of the cochlea. 

 Within the vestibule : 

 Utricle and saccule. 

 Utricle. 



