364 MIDDLE EAR. 



The external opening of the meatus is of oval form ; of 

 variable size, and often, in old people, containing coarse 

 hairs, which prevent the entrance of insects and foreign 

 bodies. 



The meatus is lined by the skin continued from the 

 auricle it becomes, however, very thin, vascular, and sen- 

 sitive, and set with delicate hairs. Beneath it are seen 

 numerous follicles, which appear upon its surface by many 

 orifices, and are called ceruminous glands. These glands 

 are little oval bodies, of a pale yellow, having a tortuous 

 ccecal tube ; they secrete the cerumen or wax of the ear. 



This secretion is a viscid matter, intensely bitter, at first 

 soft, but soon becoming solid, and designed to defend the 

 meatus from foreign intrusion. 



The ligaments of the pinna are the anterior, which con- 

 nects the tragus and anterior part of the helix to the root 

 of the zygoma; and the posterior, connecting the concha to 

 the mastoid process. Some fibres, extending from one em- 

 inence to another, are also spoken of as ligaments. 



The Arteries of the external ear come from the posterior 

 auricular of the external carotid, and the anterior auricu- 

 lar of the temporal. 



The Nerves are supplied by auricular branches from the 

 cervical plexus, and the fifth. At the anti-tragus a branch 

 perforates the meatus, and is distributed upon the inner 

 surface of the concha. 



Middle Ear, or Tympanum. Dissection. Kemove the 

 membrana tympani, or cut away the anterior part of the 

 base of the petrous .portion of the temporal bone, and the 

 tympanum will be exposed. The tympanum (tympanum, a 

 drum) is a small cavity of irregular form, situated between 

 the meatus externus and the labyrinth or internal ear, 

 having the mastoid portion of the temporal bone behind, 

 and communicating, in front, with the Eustachian tube. 



Its external boundary is the membrana tympani, or drum 

 of the ear. This membrane, situated at the bottom of the 

 meatus, is of a circular form, and directed obliquely down- 

 ward and inwardj in such way that the inferior wall is 



