SEC. 2. THE STRUCTURE OF THE LABYRINTH. 



821. The membranous labyrinth, into which the primitive 

 otic vesicle is developed, though very complicated in form, is 

 virtually a sac the cavity of which filled with endolymph is con- 

 tinuous throughout. We may in the first place consider it as 

 consisting of two divisions, which differ from each other both as to 



n aud 



l.sp mb Ig.sp 



r .ah ras chl' chl 



chC 



FIG. 175. THE MEMBRANOUS LABYEINTH (OF THE RIGHT EAR) AS SEEN FROM 

 ABOVE, MAGNIFIED six TIMES. (After Retzius.) 



The bony envelope has been wholly removed from the vestibular division, but only 

 in part broken through in the cochlear division. 



chl the cochlea, chl' the first part of the basal whorl, chl" the summit. To the 

 right, where the bony wall has been broken through, are seen : l.sp the spiral 

 lamina, m.b the basilar membrane, Ig.sp the spiral ligament. 



n aud the auditory nerve, lying along side of which is seen VII, the seventh, facial 

 nerve. 



m.s macula of the saccule. m.u macula of the utricle, cr.p the crista of the 

 posterior semicircular canal, with r.a.p the branch of the auditory nerve 

 distributed to it, cr.s crista of the superior canal with r.a.s its nerve, a.h 

 ampulla and cr.h crista of the horizontal canal, with r.ah its nerve. 



x the conjoined posterior and superior canals, d.e ductus endolymphaticus, with 

 c.u.s its junction with the utricle. 



