EXTERNAL STRUCTURE. 



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delicate membrane, with several apertures or holes, b, /, k, the principal 

 of which we shall describe. 



EXPLANATION OF THE CUT OF THE EAR. 



a The meatus externus, or outer passage. 



b The membi-ana tympani, or membrane stretched over the entrance to the drum of the 

 ear. 



c The malleus, or hammer, the first of the ossiculi (little bones), and resting upon the 

 membrana tympani. 



d The mcus, or anvil. 



e The orbiculare, or round bone. 



/ The stapes or stirrup bone, resting on the membrane which covers the foramen ovale, 

 or oval window, and which conducts to the labyrinth of the ear. 



g One of the muscles of the tympanum attached to the stapes. 



h The vestibule, or hall, the first portion of the labyrinth of the ear. 



i The semicircular canals. 



k Openings into the canals. 



I The tympanum, or drum of the ear. 



m The cochlea, or shell-like portion of the labyrinth. 



n The meatus auditorius internus, or internal passage, through which both divisions of the 

 seventh pair of nerves enter the ear. At the end of it is the cribriform sieve- 

 like plate, through which the portio mollis, or soft portion of the seventh pair of 

 nerves, an .. which is the auditory nerve, or nerve of hearing, enters to spread over 

 the cochlea and vestibule. 



The Eustachian tube, or communication between the tympanum and the mouth, so called 

 from its discoverer. 

 The cord, or nerve of the ear, corda tympani, a branch of the portio dura, hard portion, 

 of the seventh pair of nerves, united to a portion of the fifth pair, running across the 

 tympanum, and ramifying on it and on the membrane. 



q The exit of the portio dura from the temporal bone, to spread over the face. 



