AND PHYSIOLOGY. 



389 



THE SENSE OF HEARING. 



DEFINITIONS AND DESCRIPTIONS. 



714 Parts of the Ear. — The organ of hearing is made 

 up of three distinct portions : the Pinna or external ear, the 

 Tympanum or middle ear, and the Labyrinth or internal ear. 



715. The Pinna. — The Pinna, commonly known as the 

 Ear, is a cartilaginous plate with numerous irregularities upon 

 its surface, and having upon it a few muscular fibers, which 



Tig. 357. Fig. 358. 



A View of the Left Ear in its Natural 

 & \to. 1, 2, The origin and termination 

 of 'the Helix. 3, The Anti-Helix. 4, The 

 Anti-Tragus. 5, The Tragus. 6, The Lo- 

 bus of the External Ear. 7, Points to the 

 Scapha, and is on the front and top of the 

 Pinna. 8, The Concha. 9, The Meatus 

 Auditorius Externus. 



An Anterior View of the External Ear, 

 as well as of the Meatus Auditorius, Laby- 

 rinth, etc. 1, The Opening into the Ear 

 at the bottom of the Concha. 2, The Mea- 

 tus Auditorius Externus or Cartilagin- 

 ous Canal. 3, The Membrana Tympani 

 stretched upon its King. 4, The Malleus. 

 5, The Stapes. 6, The Labyrinth. 



714. What are the three parts of the organ of hearing ? 715. Describe the pinna. 



