J8 ANATOMICAL AND PHYSIOLOGICAL STUDIES ON 



ment, and at birth their cell bodies are short and undeveloped, 

 so that they hardly suggest the adult cells. 



Hensen's supporting cells (fig. 10, at maturity) are as yet 

 undeveloped and nearly uniform in height, their nuclei being 

 at nearly the same level. 



Outward from the Hensen's cells the height of the epithelial 

 cells at maturity rapidly diminishes and passes over to the 

 cylindrical cells of sulcus spiralis externus. At birth no such 

 distinction is present. Through all the turns the surface of the 

 lesser epithelial ridge remains about parallel to the plane of the 

 membrana basilaris. 



The membrana basilaris, which stretches from the labium 

 tympanicum outward to the crista basilaris of the ligamentum 



Figs. 4 to 12 Showing the increase in size and morphological changes in 

 each part of the tympanic wall of ductus cochlearis of the cochlea during 

 growth, in the radial vertical section albino rat. All the figures have been 

 uniformly enlarged. 



Fig. 4 One day. C, greater epithelial ridge; L, lesser epithelial ridge. 



Fig. 5 Three days. 



Fig. 6 Six days. 



Figs. 7 to 8 Showing the differences in size and morphological changes in 

 the tympanic wall of ductus cochlearis between a nine-day-old rat which can 

 already hear (fig. 8) and one that cannot (fig. 7) 



Fig. 9 Twelve days. 



Fig. 10 Twenty days. In figure 10 we have drawn all the elements of the 

 organ. 



ABBREVIATIONS 



M.T., membraua tectoria a. Corti O.P., outer pillar 



L.V., labium vestibulare of crista B.C., basal cells 



spiralis D.C., Deiters' cells 



S.S.I., sulcus spiralis interims Bo.C., Boettcher's cells 



S.I.C., cells of sulcus spiralis interims L.S., ligamentum spirale 



I.S., inner supporting cells N.F., myelinated fibers of ramus 

 I.H., inner hair cells acustici 



O.H., outer hair cells R.F., radial fibers of ramus basilaris 

 H.S., Hensen's supporting cells acustici in the tunnel of Corti 



S.E.C., cells of sulcus spiralis externus T., tunnel of Corti 



M.B., membrana basilaris B., blood vessels 



I. P., inner pillar 0., bone 



Fig. 1 1 One hundred days. 



Fig. 12 546 days. 



