DEVELOPMENT OF THE SENSE ORGANS 



385 



n.coc 



B 



sc.tymp. 



FIG. 367. Three stages in the differentiation of the basal epithelium of the cochlear duct to form 

 the spiral organ (of Corti), internal spiral sulcus and labium vestibulare. A , section through the cochlear 

 duct of an 8.5 cm. pig fetus; B, the same from a 20 cm. fetus; C, from a 30 cm. fetus (near term). 

 ep. s. sp., epithelium of spiral sulcus; h.c., hair cells; i.ep.c., inner epithelial thickening; i.h.c., inner hair 

 cells; i.pil., inner pillar of Corti; lab. vest., labium vestibulare; limb, sp., limbus spiralis; m. bas., basilar 

 membrane; m. tect., membrana tectoria; m. vest., vestibular membrane; n. cock., cochlear division of 

 acoustic nerve; o.ep.c., outer epithelial thickening; o.h.c., outer hair cells; s.sp., sulcus spiralis; sc.tymp., 

 scala tympani; st.H., stripe of Hensen; t.sp., spiral tunnel. 

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