428 



ON SENSATION, AND THE ORGANS OF THE SENSES. 



[Fig. 189. 



The soft parts of the Vestibule taken out of their bony case, so as to show the distribution of the Nerves 

 -ii the Ampullae ; 1, the superior semicircular membranous canal or tube ; 2, the external semicircular 

 tube ; 3, the inferior semicircular tube ; 4, the tube of union of the superior and inferior canals ; 5, the 

 sacculus ellipticus ; 6, the sacculus sphericus ; 7, the portio dura nerve; 8, the anterior fasciculus of the 

 auditory nerve ; 9, the nerve to the sacculus sphericus ; 10, 10, the nervous fasciculi to the superior and 

 external ampullae; 11, the nerve to the sacculus ellipticus ; 12, the posterior fasciculus of the auditory 

 nerve, furnishing 13, the filaments of the sacculus sphericus, and 14, the filaments of the cochlea, cut off.] 



iff. 190. 



The Ampulla of the External Semicircular Membranous Canal, showing the Mode of termination of its 

 Nerve.] 



ing body is placed in connection with any other, of which one or more parts 

 may be thrown into reciprocal vibration, even though the tone of the whole 

 be different, or it be not capable of producing a definite tone at all. This is 

 the case, for example, when a tuning-fork in vibration is placed upon a sound- 

 board ; for even though the whole board have no definite fundamental note,* 



* The fundamental note of a body is the lowest tone which it will yield, when the whole 

 of it is in vibration together. By dividing the body into two or more distinct parts, it may 



