THE MEMBRANOUS LABYRINTH 



1095 



termination. Each duct is less than a third of the diameter of the bony canal, 

 from which it is separated by a large perilymphatic space, except along the 

 greater cm-vature, where it is attached. The ducts are dilated in the bony 



Fig. 841. — Schematic Representation of the Right Membranous Labyrinth and the 

 Drv'isioNS of the Acoustic Nerve. Dorsal view. (Toldt, "Atlas of Human Anatomy," 

 Rebman, London and New York.) 



Utriculo-saccular duct 

 Macula acustica of utricle I 



Macula acustica of saccule 

 I 

 Vestibular ganglion 



Vestibular nerve 

 Saccular nerve \ 



Cochlear nerve.^ 



Cochlear duct ""- 



Saccule 

 Ductus reuniens (of Hensen) 



Posterior ampullary nerve 



-Superior semicircular duct 

 Ampullary cristje of the 

 • superior and lateral 

 semi-circular ducts 



— Lateral semicircular 

 duct 



^Endolymphatic 

 duct 



Posterior semicir- 

 cular duct 



Ampullary crista of 

 the posterior semi- 

 circular duct 



-" Endolymphatic sac 



Utricle 



ampullae, producing the lateral, superior, and posterior membranous ampullae, 



and on the attached surface of each of these there is a transverse groove, the 

 ampullary sulcus, for the ampullary division of the vestibular nerve, and corre- 

 sponding to the sulcus a ridge, the ampullary crista, projects into the interior. 



Fig. 842. — Axial Section Through the Decalcified Cochlea of a Newborn Child 

 (Toldt, "Atlas of Human Anatomy," Rebman, London and New York.) 



Hamulus of lamina spiralis ^ 'i^'^^^J'r^i^ 

 Apical spiral- 

 Middle spiral ^ 



Basal spiral v 



Vestibular mem-_ 

 brane (of Reissner) " 



Lamina basilaris 

 (membranous lamina' 

 spiralis) 



Helicotrema 

 ■^*;^'' Modiolus 



Scala vestibuli 

 Cochlear duct 



\>^ Spiral ligament of cochlea 

 v\ \ '%^ Scala tympani 



Perilymphatic space of 

 vestibule 



Macula acustica sacculi 



Osseous lamina spirahs 



Spiral ganglion of cochlea ^^ie^^? 



Base of modiolus 



Cochlear nerve 

 Internal acoustic meatus 



Acoustic nerve (cochlear divisionl 



Wall of saccule 

 Saccular nerve 



i^.y'~^^^$^f^ Vestibular ganglion 



Acoustic nerve (vestib- 

 ular division) 



The cristse in the ampullae of the membranous semicircular ducts and the maculae 

 in the saccule and utricle are superficially covered with fine crystals of calcium 

 carbonate, otoconia (otoliths). 



