176 



SENSE OF HEARING. 



monly looked upon as an acoustic instrument, for collecting the so- 

 norous rays or vibrations, and directing them, in a concentrated state, 

 to the parts within. It is composed of the pavilion, and meatus audi- 

 torium externus. 



The pavilion varies in size and position in different individuals. It 

 is the fibro-cartilaginous, thin, expanded portion, which is an append- 

 age, as it were, to the head. It is irregular on its anterior surface ; 

 presenting several eminences and depressions. The eminences are five 

 in number; and have been called, by anatomists, helix, anthelix, tragus, 

 antitragus, and lobe. The helix forms the rim of the pavilion: the 

 tragus is the small nipple-like projection on the facial side of the 

 meatus auditorius; the antitragus is the projection opposite to this, 

 forming the lower portion of the anthelix; and the lobule is the fatty, 

 pendulous portion, to which ear-rings are attached. The depressions 

 are three in number the groove of the helix or cavitas innominata ; 

 the fossa navicularis or scapha ; and the concha. The name of the 

 first sufficiently indicates its situation; the second is nearer the meatus 

 auditorius; and the third is the expanded portion, which joins the com- 

 mencement of the meatus, and is bounded by the anthelix, tragus, and 

 antitragus. The pavilion is supple and elastic ; and, beneath the skin 

 are numerous sebaceous follicles, which are distinctly perceptible, and 

 give the skin its polish, and probably a portion of its suppleness. On 

 the different eminences, some muscular fibres are perceptible, which it 

 is not necessary, for our purpose, to distinguish ; for in man at least 

 they are but vestiges as the French term them to indicate the uni- 

 form plan that appears to have prevailed in the formation of verte- 

 brated animals : if they have any office it must be unimportant. Nu- 



merous vascular and nervous ramifications 

 are distributed on the pavilion. It is at- 

 tached to the head by different ligaments, 

 called from their situation or attachments 

 zygomato-auricular or anterior-auricu- 

 lar : temporo-auricular or superior-au- 

 ricular, and mastoido-auricular or posteri- 

 or-auricular ; all of which terminate on 

 the convex part of the concha. Three 

 muscles, in animals at least, are attached 

 to the ear to move the pavilion. These 

 occupy the same position as the ligaments 

 described; and have similar names. In 

 man, they, again, are mere vestiges; but in 

 many animals as the horse they are 

 largely developed, and capable of moving 

 the pavilion in various directions; and 

 there are persons, who possess a degree of 



Voluntary pOWCr OVCr it. 



The mecttus auditorius externus extends 



Fig. 65. 



Anterior View of the External Ear, 

 as well as of the Meatus Audito- 

 rius, Labyrinth, &c. 



1. The opening into the ear at the 

 bottom of the concha. 2. Meatus au- 

 ditorius externus or cartilaginous ca- _ .. 



3. Membrana tympani stretched from the inner extremity of the concha to 



4. Malleus. 5. Stapes. ^ rt rv l_ ^ ; J n the a( Jult, it 





the membrana tympani. 



