68o THE SENSE OF HEARING. 



which those that line the ampullae are prolonged into stiff 

 hair-like processes ; the same appearance, but to a much 

 less degree, being visible in the utricle and saccule. In the 

 cavities of the utriculus and sacculus are small masses of 

 calcareous particles, otoconia or otolitJies ; and the same, 

 although in more minute quantities, are to be found in the 

 interior of other parts of the membranous labyrinth. 



The auditory nerve, for the appropriate exposure of 

 whose filaments to sonorous vibrations all the organs now 

 described are provided, is characterised as a nerve of 

 special sense by its softness (whence it derived its name 

 of portio mollis of the seventh pair), and by the fineness of 

 its component fibres. It enters the labyrinth of the ear 

 in two divisions ; one for the vestibule and semicircular 

 canals, and the other for the cochlea. The branches for 

 the vestibule spread out and radiate on the inner surface 

 of the membranous labyrinth : their exact termination is 

 unknown. Those for the semicircular canals pass into the 

 ampullae, and form, within each of them, a forked projec- 

 tion which corresponds with a septum in the interior of 

 the ampulla. The branches for the cochlea enter it through 

 orifices at the base of the mediolus, which they ascend, and 

 thence successively pass into canals in the osseous part of 

 the lamina spiralis. In the canals of this osseous part 

 or zone, the nerves are arranged in a plexus, containing 

 ganglion- cells. Their ultimate termination is not known 

 with certainty ; but some of them, without doubt, end in 

 the organ of Corti, probably in cells. 



Physiology of Searing. 



The acoustic portion of the physiology of hearing is thus 

 illustrated by Miiller: chiefly in applications of the results 

 of his experiments on the conduction of sonorous vibra- 

 tions through various combinations of air, water, and solid 

 substances, especially membrane. 



All the acoustic contrivances of the organ of hearing are 



