774. 



THE SENSE OF HEARING 



of the stapes are propagated through them in the direction from the 

 vestibule to the fenestra rotunda. This is of importance, because it 

 enables the membranes closing the aforesaid foramina, to vibrate in 

 unison. In other words, an inward movement of the membrane of 





mmi^ttS^mMf^^ 







Fig. 392. — 'Diagram of a Transverse Section of the Cochlea. 

 Sc.V, scala vestibuli; Sc.T, scala tympani; C.Chl, canalis cochlearis; Lam.sp, lamina 

 spiralis; Gg.sp, ganglion spirale; n.aud, auditory nerve; m.R, membrane of Reissner; 

 Str.v, stria vascularis; Lg.sp, ligamentum spirale; t.l, lymphatic epithelioid lining of 

 basilar membrane on the tympanic side; m.b, basilar membrane; Org. C, organ of Corti; 

 L.t, labium tympanicum; lb, Iimbus;Z/.v, labium vestibulare; m.t, tectorial membrane. 

 (After Foster.) 



the fenestra ovalis gives rise to an outward movement of the mem- 

 brane of the fenestra rotunda. If no provision had been made for this 

 interchange of pressure within the internal ear, the membrane of the 



