1 66 GLIMPSES OF NATURE. 



and the other of rounded outline. The next part of 

 the ear consists of a chain of three small bones or 

 "ossicles" (see between 3 and 6, fig. 33), which lie 

 across the drum in such fashion that all vibrations of 

 that membrane must, of necessity, be communicated 

 to the bones. One bone is like a hammer in shape, 



Fig- 33- View of the parts of the ear from the left side. i, outer ear ; 

 2, external opening and ear passage ; 2', drum-membrane ; 3, cavity of the 

 tympanum ; between 3 and 6, the chain of small bones ; 4, Eustachian tube ; 

 5, facial and auditory nerves ; 6, internal ear ; b, internal carotid artery ; 

 d, facial nerve ; a, c, e, f, portions of bone. 



the second like an anvil, and the third like a stirrup. 

 The flattened plate of the stirrup-bone is placed on 

 the oval opening in the bony partition already named. 

 The next part of the ear is the labyrinth, which con- 

 tains fluid, and which receives the ends of the nerves 

 of hearing whose mission it is to carry the messages 

 they receive from the outer world to the brain. 



The labyrinth itself is composed of two parts. Of 



