( fiB ) 



Besides, at its place of attaclinienl tlie lamella has been made 

 considerably thinner (thickness 0,02 cm.) and consequently tiexible 

 over a length of G cenlimeti-es. The result is that the lameUa, although 

 accurately placed in the node of the vibrating string, will slightly 

 deviate outward as soon as the excursions have l^ecome large enough. 

 The force by which the little fork is driven outward is undoubtedly 

 extremely small. Accordingly the deviation did not exceed 3 mm. 

 with a semi-amplitude of the string of 0,4 cm. The new position 

 can easily be tixed photographically and be compared with the 

 position of rest which is assumed as soon as the string stops vibrating. 

 This renders it possible to measure the force. But from a physiolo- 

 gical point of view it has no meaning to perform the actual measu- 

 rement on the model although it would be important if it could be 

 performed under the actual conditions, for this pressure must he the 

 immediate cause of heariih/. This will l)e easily perceived with 

 respect to the sensory elements at the modiolus side of the pillars. 



The pressure of sound acting at the base of these outer pillars is 

 in the direction of the string and hence of the modiolus. Jt has a 

 component in the direction of the pillar itself. Through this the outer 

 pillar, the upper end of which presses loosely against the capitulum 

 of the inner pillar, is displaced parallel to itself and the cells at the 

 modiolus side of the system must necessarily be compressed, although 

 slightly. The pressure which they experience is either entirely con- 

 tinuous or periodically feebly variable. Beginning at the foot of the 

 pillar the pressure varies from a maximum at the extreme deflection 

 of the string to zero in the position of equilibrium. Higher uj) in 

 the system these diiFerences will probably for the greater part have 

 disappeared, though they may remain to some extent. The pressure, 

 however, is at all times positive; it never becomes negative, as would 

 be the case if the Corti's arches and the loading cells followed the 

 vibrations of the string. Since they are at rest, the pressure met w itii 

 in the sensory cells at the modiolus side of the inner pillar must 

 always act in the same sense, which is in the direction of the modiolus. 

 It is quite possible that also the hairs of the hair-cells experience 

 its influence, the effect of which will also l)e in one direction. 



The matter is somewhat less simple for the sensory elements situated 

 at the inner side of the outer pillar. These appear to me to experience 

 no pressure at all from the outer pillar, which is retained in the soft 

 cell-mass of the bottom cell. On the othei- hand such a pressure is 

 present from the side of Henskn's cells and also to some extent from 

 the side of the supporting cells. 



We are at liberty to consider this cell-group, situated at the extei'ior 



