882 



ORGAXS OF SPECIAL SEXSE 



The membranous canal of the cochlea is connected with the saccule by a short 

 canal; canalis reuniens. 



The two sacs are indirectly connected by means of a small tube, ductus endo- 

 lymphaticus. which leaves the saccule, joins the commencement of a minute canal 

 which passes to the utricle, and descends in the aqueductus vestibuli to terminate 

 in an enlargement, the saccus endolymphaticus. 



Fig. 504. — Membranous Labyrixth (magnified), with Nerves. 

 (Modified from Breschet.) 



BRANCH TO POSTERIOR 

 CANAL 



SACCULE 

 BRANCH TO SACCULE 

 BRANCH TO COCHLEA 



BRANCH TO SUPERIOR AND 

 EXTERNAL CANALS 



BRANCH TO UTRICLE 

 FACIAL NERVE 



Within each semicircular canal the membranous labyrinth occupies less than 

 a third of the area of the tube, but follows its curves and repeats its ampullary 

 enlargement; and here the wall of the membranous canal is thicker and more 

 opaque, and more completely fills the cavity. The membranous ampullse are 

 flattened on their external walls, where they receive vascular and nervous' filaments, 



Fig. 505.— Enlarged Diagrammatic View of Membranous Labyrinth. 



SCALA MEDIA OF 

 COCHLEA 



SUPERIOR 

 SEMICIRCULAR 

 CANAL 



EXTERNAL 

 SEMICIRCULAR 

 CANAL 



POSTERIOR 

 SEMICIRCULAR 

 CANAL 



and their cavities are partially divided by a transverse crest or ridge (crista acustica). 

 The outer convex l)order of each membranous canal is fixed to the osseous wall. 



Structure. — The membranous labyrinth consists of three layers: a tunica 

 propria, witli a fibrous investment externally, and an epithelial lining Avithin. 



Within the cochlea, the membranous structures divide the canal into thrcii 

 compartments. The lamina spiralis (which in macerated specimens only partially 



