THE EAR AND THE SENSE OF HEARING 



certain fibers have been traced to the corpora quadri- 

 gemina, while others convey the impression to the gray 

 matter of certain convolutions 

 of the temporal lobe of the 

 cerebrum. 



179. Function of the Vestibule 

 and Semicircular Canals. Much 

 research has in recent years 

 been directed to the part played 

 by these portions of the inner 

 ear, but no investigator has yet 

 reached a conclusion which is 

 accepted in all its details by all 

 others. It is, however, gener- 

 ally believed that these parts Fig. 78. Diagram of the path 

 have little, if any, direct con- 

 cern with the sense of hearing 



and discriminating sounds. 

 The nerve branches distributed 

 here arise in the brain from a 

 root of the auditory nerve dif- 

 ferent from that which sends nerves to the cochlea. The 

 cerebellum, from which some of its fibers come, is well 

 known to be the great center for coordination of muscular 

 movement, and experiments seem to indicate that what is 

 called the vestibular branch of the auditory nerve, which 

 ends in the vestibule and semicircular canals, conveys to 

 the brain impressions of position and of movement in 

 space which have to do with the sense of equilibrium. 



180. Hearing with Two Ears. The two organs and two 

 nerves of hearing convey to the brain, not two sensations, 

 but one. By means of two ears we are able to some 

 extent to determine the locality from which sounds come, 



of an auditory impulse. 



The impulse passes from the 

 auditory cells in the ear to the cen- 

 ter of hearing (Au C) in the tem- 

 poral lobe of the cerebrum. Some 

 fibers pass to the anterior corpora 

 quadrigemina (Q). 



