220 



ELEMENTARY PHYSIOLOGY 



called the perilymph (Gr. peri, around ; and lympka, clear water). The 

 membranous labyrinth is itself filled with a liquid called the endolymph (Gr. 

 endo, within ; and lympha). A number of minute crystals of carbonate of 

 lime, called otoliths (Gr. ous, the ear ; and lithos, stone) are suspended in 

 the endolymph of the membranous labyrinth. 



Fig. 211. Plan of the Bight Membranous Labyrinth. 



Branches of the auditory nerve supply fibres to the membra- 

 nous labyrinth. The terminations of these fibres end in cells 

 which are provided with delicate hair-like processes projecting 

 into the endolymph, some of them lying in close proximity to the 

 otoliths. 



We may now trace the path along which the sound vibrations 

 travel. The waves collected by the pinna are reflected into the 

 auditory canal, at the extremity of which they impinge against the 



Fig. 212. Diagram illustrating the relative positions of the various 

 parts of the Ear. 



i, auditory canal : 2, tympanic membrane ; 3, malleus ; 4, incus ; 5, stapes ; 6, fenestra 

 oyalis ; 7, fenestra rotunda ; 8, Eustachian tube ; 9, membranous labyrinth ; 10, semi- 

 circular canal ; ii, vestibule ; 12, cochlea. 



drum. The vibrating membrane then communicates its motion 

 to the chain of small bones, by which it is transmitted to the peri- 

 lymph of the inner ear. This fluid communicates the vibration to 



