THE SPECIAL SENSES. 47 



such a way that an impression is made and carried 

 to the brain to be recognized by the mind. 



The ear is divided into the outer, middle 

 Outer Ear. and inner ear. Tne outer ear has a 



more or less cartilaginous frame. This 

 allows motion, and, at the same time, keeps it in 

 shape and position. It has also a few small muscles. 

 But in the human ear these are nearly altogether 

 useless, since men do not move or flop their ears. 

 In animals which move their ears in various ways, 

 these muscles are quite well developed. 



(Sense of Hearing.) 



From the outer ear (1) a tube, a little 

 Ear Middle over an inch long, called the auditory 



canal (2), leads in to the middle ear, 

 where it is closed by a membrane called the mem- 

 brana tympani, which means the membrane of the 

 tympanum or drum (3). The middle ear is often 

 called the "ear-drum," and the membrane just men- 

 tioned may be called the "drum-head," for it does, 

 indeed, act very much like the head of a drum. 

 Between this membrane of the drum and its inner, 

 opposite side or end, there is stretched a very curious 

 little suspension bridge of four small bones. The 

 first of these is attached to the drum-head, and from 

 its shape like a hammer is celled the malleus (4). 

 The next is called the incus, because it is shaped 

 like an anvil (7). The third is a very small pebble 

 of a bone called the orbicular or round bone (10). It 



