THE SPECIAL SENSES 



307 



the external ear, the middle ear, and the internal ear. (In the 

 diagram, Fig. 70, A, the first is not shaded, the second is lightly 

 shaded, and the last has a dark background.) 



91. The External Ear. The external portion of the organ 

 of hearing, designated in Fig. 70, A, includes, first, that outer 

 part (a), which is commonly spoken of as "the ear," but which 



Fie. 70. THE EAR AND ITS DIFFERENT PARTS 



A, Diagram of the Ear 



a, 6, External Ear d , Middle Ear 



c, Membrana tympani , Internal Ear 



B to B'", Bones of the Middle Ear (magnified) 

 C, The Labyrinths or Internal Ear (highly magnified) 



in fact is only the portal of that organ; and, secondly, the 

 auditory canal (b). The former consists of a flat, flexible piece 

 of cartilage, projecting slightly from the side of the head, 

 attached to it by ligaments, and supplied with a few weak 

 muscles. Its surface is uneven, and curiously curved, and from 

 its resemblance to a shell it has been called the concha. It 

 probably serves to collect sounds, and to give them an inward 

 direction, although its removal is said not to impair the aqute- 

 ness of hearing more than a few days. 



91. Of what does the external portion of the organ of hearing consist ? Describe th 

 portal of that organ known as the ear. Its use ? 



