EXTERNAL STRUCTURE. 



7& 



ielicote membrane, with several apertures or holes, J, /, k, the principal 

 of ivhich we shall describe. 



STRUCTURE OF THE EAR 



EXPLANATION OF THE PRINCIPAL PARTS, 



WITH THEIR ANATOMICAL TERMS. 



Meatus extemus, or outer passagre. 



Membrana tympani, or membrane stretched over the entrance to the dri a of tlia 

 ear. 



Malleus, or hammer, the first of the osslculi (little bones), and resting ufon tha 

 membra.na tympani. 



Incus, or anvil. 



Orbiculare, or ro«n-A bone. 



Slopes, or stirrup bcris, resting' on the membrane which covers the .^» >men ovale, 

 or oval windu--v, and which conducts to the labyrinth of the ear. 



One of the muscles of the tyiVipanum attached to the stapes. 



Vestibule or hall, the first portion of the labyrinth of the ear. 



Semicircular canals. 



Opening's into the canals. 



iSjmpanum, or drum of the ear. 



Cochlea, or shell-like portion of the labyrinth. 



Meatus auditorius intemus, 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 ihc portio mollis, or soft portion of the seventh pair of 

 nerves, and which is the auditory nerve, or nerve of hearing-, enters to spread over 

 the cochlea and vestibule. 



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

 from its discoverer. 



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 ac'oss thfl 

 tympanum, and ramifying on it and on the membrane. 



Exit, of the portio dura from the temporal bone, to spread over the face. 



