THE SPECIAL SENSES. 49 



thrown into a violent trembling. By these trem- 

 blings or vibrations of the material of the bell the 

 air is thrown into a wave-like motion all around it. 

 When these trembling air waves reach the ear, the 

 sensation of sound is produced and we say we hear 

 the bell. When a person speaks to us the voice 

 chords in his throat are set into rapid vibration. 

 These vibrations produce waves of sound in the air; 

 the air carries these waves to the ear, where, passing 

 in through the auditory canal they tremblingly beat 

 upon the drum-head; this carries the sounds to the 

 bridge of little bones. Having passed over these, 

 it enters the vestibule, then vibrates into the semi- 

 circular canals and rebounds into the cochlea, where, 

 as already stated, it is taken up by the nerve and 

 carried to the brain where the mind interprets it as 

 the voice and the language of the speaker. 



THE SENSE OF SMELL. 



The organ of smell is the nose and its cavities. 

 The nerve of smell is called the olfactory nerve. 

 This nerve is spread out in many branches over the 

 delicate mucous membrane which lines the inside of 

 the nose. To make the surface on which the nerve 

 of smell is distributed as large as possible, there is 

 set into the nostrils, against the outer walls, a pair 

 of scroll-like bones. These are the turbinatcd bones 

 of the face. Over their winding surfaces, covered 

 with the mucous lining, the nerve of smell is spread. 

 The two small nasal bones unite the nose to the 



