, 4 8 



APPLIED PHYSIOLOGY 



This tube enters the skull. The tube and the ear which 

 we see are called the outer ear. 



295. The middle ear. At the end of the tube of the 

 outer ear a thin membrane is stretched like the head of 

 a drum. Beyond it is a hollow cavity which is like a 

 drum, and is called the middle ear. Air waves strike 



Diagram of the ear. 



a outer air passage. f semicircular canals. 



b membrana tympani. g vestibule of inner ear. 



c malleus, or hammer bone. h cochlea. 



d incus, or anvil bone. i Eustachian tube. 



e stapes, or stirrup bone. j tympanum, or middle ear. 



the drumhead and cause it to move rapidly back and 

 forth, just as a drumhead moves when it is struck. A 

 chain of three little bones stretches across the drum and 

 carries the movements of the drumhead to a third cavity 

 called the inner ear. 



296. The inner ear. The inner ear is made up of coiled 

 tubes. It is filled with a clear liquid into which the nerves 

 of hearing project. The movements of the little bones 

 produce waves in the liquid, which beat against the nerves. 

 Our brains feel the waves as a sound. The outer ear con- 

 ducts the sound to the middle ear. The middle ear acts 



