362 EXTERNAL EAR. 



All the depressions and furrows of the pinna, converge 

 to a large, central, funnel-shaped cavity, the concha, 

 which leads obliquely downward and forward to the me- 

 atus auditorius externus. The soft and pendulous portion 

 of the pinna, at its lowermost part, is named the lobulus. 



The structure of the pinna consists of integument, fibro- 

 cartilage, muscles , and ligaments. 



The integument is remarkable for its strong adhesion to 

 the cartilage, and for its thinness and transparency. The 

 folding of the skin enclosing fat constitutes the lobule. 

 The skin is supplied with numerous sebaceous follicles, 

 which are most abundant in the concha and scaphoid fossa. 



The fibro-cartilage gives the shape to the auricle, forms 

 the framework of its support, and is the source of its elas- 

 ticity and pliability. It presents very nearly the same 

 eminences and depressions as those already described. The 

 lobule is without the cartilage. This cartilage is covered 

 with perichondrium, which becomes weak and brittle on 

 being removed. The tragus is separated from the helix by 

 fibrous tissue, and presents a deep fissure. A considerable 

 fissure separates the termination of the helix and anti- 

 helix from the concha. 



The muscles of the external ear consist of those which 

 attach it to the head, and of those passing from one car- 

 tilage to the other. The first division comprises three 

 muscles, the superior or attollens aurem } the anterior or 

 attrahens aurem, and the posterior or retraliens aurem, 



(fig- 82.) 



The attollens aurem is a triangular muscle, the largest of 

 the three, and arises, broad and tendinous, from the cra- 

 nial aponeurosis above the ear ; it descends, becomes fleshy, 

 and is inserted into the upper and anterior part of the 

 concha. 



Function. To raise the external ear, and deepen the 

 meatus. 



Anterior auris, also triangular, arises from the posterior 

 part of the zygomatic process and cranial aponeurosis, and 

 is inserted into the anterior part of the helix. 



