. Applied physiology : including the effects of alcohol and narcotics . rsons the muscles of the eyes, like themuscles of the legs, do not act rightly. They often turnthe eyes in different directions. Then the person will becross-eyed, and every object will seem double. Tobacco, in some cases, causes the nerve of sight to wasteaway. Tobacco smoke makes the eyes smart so that thetears flow. 293. The ears. â We hear with our ears. Sound ismade by waves of air which beat upon special ear is a cavity, hollowed out of a very hard bone,and is divided into three parts. 294. The outer ear.
. Applied physiology : including the effects of alcohol and narcotics . rsons the muscles of the eyes, like themuscles of the legs, do not act rightly. They often turnthe eyes in different directions. Then the person will becross-eyed, and every object will seem double. Tobacco, in some cases, causes the nerve of sight to wasteaway. Tobacco smoke makes the eyes smart so that thetears flow. 293. The ears. â We hear with our ears. Sound ismade by waves of air which beat upon special ear is a cavity, hollowed out of a very hard bone,and is divided into three parts. 294. The outer ear. â The outer ear, which we see, isnot needed, but it does some good in catching the wavesof sound and throwing them into the tube in its center. 148 APPLIED PHYSIOLOGY This tube enters the skull. The tube and the ear whichwe see are called the outer ear. 295. The middle ear. â At the end of the tube of theouter ear a thin membrane is stretched like the head ofa drum. Beyond it is a hollow cavity which is like adrum, and is called the middle ear. Air waves strike. a outer air passage. b membrana tympani. c malleus, or hammer bone. d incus, or anvil bone. e stapes, or stirrup bone. Diagram of the ear. / semicircular vestibule of inner Eustachian tube. / tympanum, or middle ear. the drumhead and cause it to move rapidly back andforth, just as a drumhead moves when it is struck. Achain of three little bones stretches across the drum andcarries the movements of the drumhead to a third cavitycalled the inner ear. 296. The inner ear. â The inner ear is made up of coiledtubes. It is filled with a clear liquid into which the nervesof hearing project. The movements of the little bonesproduce waves in the liquid, which beat against the brains feel the waves as a sound. The outer ear con-ducts the sound to the middle ear. The middle ear acts THE SENSES 149 # Mke a sounding box to make it plainer and more inner ear is the real ear. Some an
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