DEVELOPMENT OF THE MEMBRANA TECTORIA 



443 



are seen. In the upper turn (fig. 14, 3 and fig. 9) the epithelial 

 cells just external to the teeth of the labium vestibulare have 

 become lower, free from the membrana and tend to form a sim- 

 ple epithelium. The space left between the membrana and the 

 shortening cells is the spiral sulcus. 



The cells remaining between the spiral sulcus and the pillars 

 of Corti still form a very high pseudostratified epithelium. In 

 the middle turn (fig. 14, 2) the cells lining the spiral sulcus are 



Fig. 9 Section of 3d (upper) spiral of cochlear duct of the 18.5 cm. stage; 

 i.h.c, inner hair cells; o.h.c, outer hair cells; lab.vest., labium vestibulare; limb.sp., 

 spiral limbus; m.bas., membrana basilaris; m.tect., membrana tectoria; m.vest., 

 membrana vestibularis; n.coch., cochlear nerve; sc.tymp., scala tympani; t.sp., 

 spiral tunnel. Oc. 4, Obj. 4, t. 1. 190. 



of the low columnar type with one or two rows of nuclei while 

 the cells internal to the pillars are but little higher than the 

 pillars themselves. Finally, in the lower turn {1) the cells lining 

 the spiral sulcus are of the cubical type, in a single layer, and the 

 remaining columnar cells persist as the internal supporting cells 

 of the spiral organ. It seems probable that large numbers of 

 the cells of the greater epithelial thickening degenerate, liquefy 

 and disappear; those remaining flatten out and form the simple 

 epithelium of the spiral sulcus. 



THE AMERICAX JOURNAL OF ANATOMY, VOL. 14, XO. 4 



