THE ORGANS OF SPECIAL SENSE 



583 



the bony canal of the cochlea is a plate of bone, the bony spiral lamina 

 (Fig. 389, .t). This follows the spiral turns of the cochlea, ending at 

 the cupola in a hook-shaped process, the liamuJus. Along the outer 



— s 



Fig. 387. — Diagram of the Right ^Membranous Labyrinth. (Testut.) i, Utricle; 2 

 superior semicircular canal; 3, posterior semicircular canal; 4, external semicircular 

 canal; 5, saccule; 6, endolymphatic duct; 7 and 7', canals connecting utricle and saccule 

 respectively with the endolymphatic duct; 8, endolymphatic sac; 9, cochlear duct; 9', 

 its vestibular cul-de-sac; 9", its terminal cul-de-sac; 10, canalis reuniens. 



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Fig. 388. — The Membranous Labyrinth from the Right Internal Ear of a Human 

 Embryo at the Fifth Month; seen from the Medial Side. (After Retzius, from Barker.) 

 1-5, Utricle; 2, utricular recess; 3, macula acustica of utricle; 4, posterior sinus; 5, supe- 

 rior sinus; 6, 7, 8, superior, lateral, and posterior ampullae; 9, 10, 11, superior, posterior, 

 and lateral semicircular canals; 12, widened mouth of lateral semicircular canal open- 

 ing into the utricle; 13, saccule; 14, macula acustica of the saccule; 15, endolymphatic 

 duct; 16, utriculo-saccular duct; 17, ductus reuniens; 18, vestibular cul-de-sac of coch- 

 lear duct; 19, cochlear duct; 20, facial nerve; 21-24, auditory nerve; 21, its vestibular 

 branch; 22, saccular branch; 23, branch to inferior ampulla; 24, cochlear branch; 25, 

 distribution of cochlear branch within the bony spiral lamina. 



side of the canal, opposite the bony spiral lamina, is a projection of 

 thickened periosteum, the spiral ligament (Fig. 389, //). A con- 

 nective-tissue membrane, the membranous spiral lamina (Fig. 389, s) 



