PROPORTIONS OF THE TECTORIAL MEMBRANE 61 



ess, the outer supporting cells of the spiral organ increase in 

 size and height, producing growth pressure on the outer side of 

 the membrane and producing an inclination axisward of the 

 apical surface of the organ. In the apical turn, where these 

 changes are greatest, the hair cells of the organ may be carried 

 axisward a distance nearly half the width of the membrane. The 

 upgrowth of the outer supporting cells also forces axisward the 

 apical ends of the elements of the spiral organ and in this 

 way contributes a small part to the shift in the relative position 

 of the hair cells. A slight increase in width of the vestibular 

 lip of the spiral limbus may contribute a still smaller part by 

 extending the membrane outward. 



15. The outspanning zone of the tectorial membrane is, and 

 of necessity becomes, free with the completion of the recession 

 and disintegration of the cells which produce it, and by the move- 

 ment axisward under it of the spiral organ. Such of the few 

 fibrils produced earlier by the lesser ridge as may persist are 

 of necessity torn away in the changes in position and all of 

 them probably disintegrate. 



