S:N ////: AITM: in > Of mi 8EN81 9. 



twisting downwards, forwards, and upwards, around a central conical axis 

 (the modioliu) ; BO that its centre nearly corresponds to tho inner wall of the 



tympanum. A partition the 



Fig. :>0-. lamina xjiirnlix, spiral like tin: 



cavity divides it into two dis- 

 tinct sections or scales : a > 

 rior and inferior ; this lamina is 

 attached by its inner border to 

 tho central axis of tho cochlea, 

 but is free at its external margin, 

 which does not quite reach the 

 periphery of tho cavity. Tho 

 two scalte, therefore, communi- 

 cate, in the skeleton, by means 

 of an opening (the lielico-lrema) 

 that follows the free border of 

 the lamina spiral is throughout 

 its extent. 



The inferior scale (or scala 

 ST, Scala tympani ; sv, Scala vestibuli ; cc, Canalis ves tibuli} enters the vestibule : 



3?=SSXl^* l tho commencement of the a^- 



rails; ss, Sulcus spiralis; gs, Ganglion spirale nor Scale, or Scala tympam, 18 



situated on nc, the nervous cochlearis indicated formed by the fenestra rotunda 



by the black line; /so, Lamina spiralis ossea; /, (fenestra cochlea), which brings 



Membrana tectoria; b Membrana basilaris ; Co, Jfc j fo communication with the 

 Organ ot Corti ; /so, Ligamentum spirale; Cc, .,.. . . 



Cells of Claudius. 1, Rod of Corti of the first middle ear, without the presence 

 order ; 2, Rod of Corti of the second order. of a membrane exactly closing 



that aperture. 



THE MEMBRANOUS LABY.BINTH. 



The membranous labyrinth comprises three parts, corresponding to tho 

 three cavities of the osseous labyrinth: 1, Tho vestibule; 2, The semi- 

 circular canals ; 3, The cochlea. 



SECTION THROUGH ONE OF THE COILS OF Till: 

 COCHLEA. 



Fig. 393. 



1. The Membranous Vestibule. 



This is composed of two sacs with thin, 

 soft walls, lodged in the osseous labyrinth ; 

 the superior is tho largest, is oval-shaped, 



1, Modiolus; 2, Infundibulum in whirh the mo- 

 diolus terminates; 3, 3, Cochlear nerve, send- 

 ing its filaments through the centre of the 

 modiolus; 4, 4, Scala tympani of the first 

 turn of the cochlea; 5, 5, Scala vt-stibuli 

 of the first turn ; the septum between 4 and 

 5 is the lamina spiralis: a filament of the 

 cochlear nerve is seen passing between the 

 layers of the lamina to be distributed in the 

 membrane investing the lamina; 8, Loops 

 formed by the filaments of the cochlear 

 nerve on the lamina spiralis; 9, 9, Scala tympani of the second turn of the cochlea; 

 10, 10, Scala vestibuli of the second turn; the septum is the lamina spiralis; 11, 

 The remaining half turn of the scala vestibuli ; the dome above is the cupola, the line 

 passing through it leads to the remaining half turn of the scala tympani. The 

 osseous lamina forming the floor of the scala vestibuli curves spirally round to con- 

 stitute the infundibulum (2) ; 14, The helicotrema through which a bristle is passed: 

 it* lower extremity issues from the scala tympani of the middle turn of the cochlea. 



ri^S r ^ 



SECTION OF THE COCHLEA PARALLEL TO 

 ITS AXIS, THROUGH THE CENTRE OF 

 THE MODIOLUS. 



