THE MEMBRANOUS LABYRINTH. 



107 



Fig. 117. RIGHT HUMAN MEMBRANOUS LABYRINTH, REMOVED FROM ITS BONV ENCLOSURE, AND VIEWED 



FROM THE ANTERO-LATERAL ASPECT. (Gr. RetZUlS.) 



Fig. 118. THE SAME FROM THE POSTERO- MESIAL ASPECT. (Gf. Retzius.) 



1, external semicircular canal ; 1', its ampulla ; 2, posterior canal ; 2', its ampulla ; 3, superior 

 canal ; 3', its ampulla ; 4, conjoined limb of superior and posterior canals (sinus utriculi superior) ; 

 5, utricle ; 5', recessus utriculi ; 5", sinus utriculi posterior ; 6, ductus endolymphaticus ; 7, canalis 

 utriculo-saccularis ; 8, nerve to ampulla of superior canal ; 9, nerve to ampulla of external canal ; 10, 

 nerve to recessus utriculi (in fig. 117, the three branches appear conjoined) ; 10', ending of nerve in 

 recessus utriculi ; 11, facial nerve ; 12, lagena cochleae ; 13, nerve of cochlea within spiral lamina ; 

 14, basilar membrane ; lo, nerve fibres to macula of saccule ; 16, nerve to ampulla of posterior canal ; 

 17, saccule ; 18, secondary membrane of tympanum ; 19, canalis reunions ; 20, blind ending of cochlear 

 canal in vestibule; 21, outer wall of cochlea; 22, spiral ligament ; 23, section of the seventh and 

 eighth nerves within internal auditory meatus (the separation between them is not apparent in the 

 section). 



epithelium, is termed the crista acustica. Seen from above (i.e., through the roof of 

 the ampulla), the septum is somewhat fiddle-shaped, the ends being broader than 



Fig. 119. VIEWS OF THE EXTERNAL SEMICIRCULAR CANAL, HUMAN. Magnified. (Gr. Retzius.) 



A, The whole of the external canal attached to the utricle, the anterior and posterior canals having 

 been cut away. Amp.cxt., ampulla of the external canal ; Amp.ant., ampulla of the anterior canal : 

 Or., crista acustica of the same ; R.utr., recessus utriculi ; S.utr.s., sinus utriculi superior, cut short ; 

 S.utr.p.j sinus utriculi posterior, ditto ; C.utr.sac., canalis utriculo-saccularis ; M.utr,, fibres passing 

 to macula recessus utriculi ; M.ittr.', the same passing round the wall of the utricle. 



B, Lateral view of the external ampulla ; n, nerve bundle entering crista. 



C, View of external ampulla, showing the free surface of the crista acustica, Cr. 



D, Transverse sectional view of the external ampulla, showing the transverse extent of the 

 crista, Cr. ; n, nerve fibres. 



