HEARING 



347 



THE TRANSMITTING APPARATUS AND FUNCTIONS OF THE EAR include 



the pinna and the external auditory meatus (making up the outer ear), 



FIG. 199 



Diagram of the grosser mechanism of the ear: au, auricle or pinna; gg, external auditory 

 meatus; tr, membrana tympani; h, malleus; a, incus, attached to the head of the stapes whose 

 foot is in the foramen ovale of the labyrinth; h' ' , p, p f , perilymphatic space of the labyrinth; c, 

 membranous labyrinth; c', one of the three semicircular canals; u, utricle; s, saccule; ph, drum 

 or middle-ear cavity; eus, Eustachian tube extending to the posterior nares; el, endolymphatic 

 duct extending to a blind bulbous ending between layers of dura mater above; ac, eighth cranial 

 or auditory nerve shows its two parts, cochlear and vestibular. (Czermak.)JS 



FIG. 200 



Diagram of the internal ear: RT, scala tympani; RV, scala vestibuli; CC, canalis cochlearis; OC, 

 Corti's organ; GC, Cord's ganglion; S, sacculus; UT, utriculus; VA and VP, two of the three 

 semicircular canals; ma, auditory maculae; ca, auditory crests of the ampullse; GS, Scarpa's 

 ganglion. (Duval.) 



