THE EAR. 213 



Vestibule. 



i Semicircular Canals. 



3. Internal Ear, or Labyrinth \ 



Cochlea. 



Auditory Nerve. 



THE EXTERNAL EAR. 



Describe the Auricle. The Auricle or Pinna is the external irregularly 

 shaped appendage, fastened to the malar and temporal bones by elastic fibres. 

 It consists of a broad plate of yellow cartilage, deficient in places where its 

 parts are joined together by ligame itous tissue, and is covered by perichon- 

 drmm and integument, the latter containing sebaceous and sweat glands, and 

 provided with short, downy hairs. The Auricle presents several elevations 

 and depressions, named as follows: 



Concha, the central cavity leading into the canal. 



Tragus, a conical eminence in front of the concha, usually covered with 



hairs along its inferior border. 



Anti-tragus, a similar projection facing the tragus, from which it is sepa- 

 rated by a deep fissure, the Incisura Intertragica. 

 Helix, the outer curved edge of the pinna, beneath which is a deep groove, 



the Fossa Navicularis. 



Anti-helix, a curved ridge along the posterior boundary of the concha, 

 bifurcating above to enclose a triangular depression, nam^d the Fossa 

 Triangular is. 



Lobe or Lobule, the soft, pendulous portion, composed of integumentary, 

 adipose and connective tissues. 



Name the Muscles of the Auricle. The 

 EXTRINSIC MUSCLES are the 

 Attolens Aurem, Attrahens Aurem, Retrahens Aurem. 



[These muscles are described on page 68.] 

 INTRINSIC MUSCLES are but slightly developed. They are the 

 Tragicus, lies vertically on the outer surface of the tragus. 

 Anti -tragicus, on the posterior wall of the auditory canal. 

 Helicis Major, vertically on the anterior border of the helix. 

 Helicis Minor, on lateral surface of the root of the helix. 

 Transversus Auricula, on the posterior surface of the auricle, radiating 



outwards from the convexity of the concha. 

 Obliquus Auricula, also on the posterior surface, radiating upwards from 



the convexity of the concha. 

 Dilator of Concha, on the tragus. 



