THE ANATOMY OF THE EAR 



649 



FIG. 430. Diagrammatic View from Before of the Parts Composing the Organ of 

 Hearing of the Left Side. The temporal bone of the left side, with the accompanying 

 soft parts, has been detached from the head, and a section has been carried through it 

 transversely, so as to remove the front of the meatus externus, half the tympanic membrane, 

 the upper and anterior wall of the tympanum and Eustachian tube. The meatus internus 

 has also been opened, and the bony labyrinth exposed by the removal of the surrounding 

 parts of the petrous bone, i, The pinna and lobe; 2, 2', meatus externus; 2', membrana 

 tympani; 3, cavity of the tympanum; 3', its opening backward into the mastoid cells; 

 between 3 and 3', the chain of small bones; 4, Eustachian tube; 5, meatus internus, contain- 

 ing the facial (uppermost) and the auditory nerves; 6, placed on the vestibule of the laby- 

 rnth above, the fenestra ovalis; a, apex of the petrous bone; b, internal carotid artery; c, 

 siyloid process; d, facial nerve issuing from the stylo-mastoid foramen; e, mastoid process; 

 at squamous part of the bone covered by integument, etc. (Arnold.) 



FIG. 431. Tympanic Ossicles of Left Ear. A, Incus seen from the front; B, malleus, 

 viewed from behind; C, incus, and D, malleus, seen from inner aspect; E, stapes, i, Body 

 of incus, with articular surface for head of malleus; 2, processus longus; 3, processus 

 lenticularis; 4, articular surface for incus; 5, head, 6, neck; 7, processus brevis; 8, manu- 

 brium; 9, body; 10, short process; n, long process; 12, processus longus; 13, head, 14, 

 facet for incus; 15, manubrium; 1 6, head; 17, neck; 18, crus anterius; 19, crus posterius; 

 20, foot plate. 



