TASTE, SMELL, AND HEARING 329 



which are so well developed in some persons that they can 

 move their ears as a horse does. 



601. Ear wax. The epithelium of the outer half of the 

 passage secretes a kind of bitter and sticky wax which 

 keeps insects and dust from reaching the drum mem- 

 brane. The epithelium grows outward towards the surface 

 like the nails, and carries the wax with it, thus preventing 

 its accumulation. Often in picking the ears the wax is 

 pushed against the drum membrane so that it cannot 

 vibrate. Next to throat trouble this is the most common 

 cause of deafness. The accumulated wax can be softened 

 and removed by gently syringing with warm water. Wax 

 can best be removed with the loop of the smallest-sized 

 hair pin, taking care not to insert it far enough to touch 

 the drum membrane. 



602. Illusions of hearing. Too dense or too rare air in 

 the middle ear, too much blood circulating in the inner ear, 

 the use of certain drugs, as quinine, blows upon the head 

 or wax in the ear, are all causes which may excite the 

 nerves of hearing. Then the impression goes to the 

 brain as though a real sound had excited the nerves. 



The cells of the brain itself may interpret a sensation 

 wrongly ; thus an insane person may think that the sound 

 of his own pulse beating in his ears is the echo of the 

 blows of demons within his head. 



Sometimes persons recall memories of sounds so vividly 

 that they seem to be real. This occurs naturally in dreams, 

 but it may occur in an insane person at any time. 



603. The ear in lower animals. In four-footed animals 

 and in birds the ear is the same as in man. In turtles and 

 frogs there is no outer ear, but the drumhead lies just 

 under the skin, forming a visible circle behind the eyes, 

 while the middle ear contains a single bone. In the snake 



