10 ANATOMICAL AND PHYSIOLOGICAL STUDIES ON 



Fig. 1 Showing the localities for the measurement of each part of the tym- 

 panic wall of ductus cochlearis in the albino rat, 100 days old — radial vertical 

 section. 1-1, height from the basal plane to the surface of pillar cells; 1-1', 

 greatest height of the tunnel of Corti; 2-2, height of papilla spiralis at the third 

 series of the outer hair cells; 3-3, height of Hensen's supporting cells; 4~4', 4 

 indicates the extension of the membrana basilaris and 4' the extension of the 

 lamina reticularis. The two lines subtend the angle 0. The radial breadth 

 of the membrana tcctoria is taken as the sum of the four segments between the 

 Hues 5-6' and 9-9'. 



Fig. 2 Showing the method of measurement for several parts of the tym- 

 panic wall of the ductus cochlearis in the albino rat, 100 days old. 1-1, length 

 of inner pillar cell without head; 2-2, length of outer pillar cell without head 

 Distance 3 shows radial distance between habenula perforata and the outer 

 corner of inner pillar at base — after twelve days of age this equals the radial basal 

 breadth of inner pillar. Distance 4, radial distance between habenula per- 

 forata and the inner corner of outer pillar at base. Distance 5, radial breadth 

 of the zona arcuata (Deiters') of membrana basilaris, and at the same time it 

 indicates radial distance between habenula perforata and the outer corner of 

 outer pillar at base. Distance 6, radial distance between the outer corner of 

 inner pillar and the inner corner of outer pillar at base. Distance 7/ radial 

 basal breadth of outer pillar. Distance 8, radial distance between the habenula 

 perforata and outer corner of inner pillar cell at base. Distance 9, radial basal 

 breadth of the outer pillar cell. Distance 10, radial breadth of zona pectinata 

 of the membrana basilaris. Distance 11, radial breadth of entire membrana 

 basilaris. 



Fig. 3 Showing the general outline of the cochlea in the radial vertical 

 section — albino rat, 100 days of age. 



ABBREVIATIONS 



Line /, /, distance between two basal L.L.S., limbus laminae spiralis 



spiral ligaments L.S., ligamentum spirale 



Line .\ .?, distance between two apical L.S.O., lamina spiralis ossea 



spiral ligaments M.T., membrana tectoria 



/, first turn N.C., nervus cochlearis 



//, second turn 0., bone 



///, third turn P.S., papilla spiralis 



/ 1'. fourth turn S., stria vascularis 



D.C., ductus cochlearis S.T., scala tympani 



G'..S'., ganglion spirale S.V., scala vestibuli 

 G V., ganglion vestibulare 



