MECHANICS OF THE INNER EAR 13 



the part of the partition next to the windows must follow 

 the movement of the fluid and move downwards. But soon 

 it has reached its lower limit. Consequently it acts now as 

 an unyielding partition, the effect of which we studied in 

 our second case above. The fluid just above and below this 

 temporarily unyielding part can now move only horizontally, 

 but the particles of fluid next to the end of this now motionless 

 piece move down and push the underlying piece of the par- 

 tition down until it has reached its lower limit. And so, 

 gradually, further and further pieces of the partition come 



1 



2 , , 



3 r 



4 v 



5 v- --■ 



6 /^ v 



7 *^^_^ 



8 / . - v - 



Fig. 6. The partition moves within an upper 

 and a lower limit 



down until the stirrup stops moving inwards. Figure 6 

 shows a number of successive stages of the position of the 

 partition during this process. The vertical scale in this rep- 

 resentation is, of course, enormously exaggerated relative to 

 the horizontal scale. But at once after stopping, the stirrup 

 begins to move in the opposite direction. At once the par- 

 ticles of fluid next to the windows (not those which have 

 moved down last) move upwards and take the corresponding 

 part of the partition with them until it has reached its upper 

 limit. Now the following parts come up, and so on in exactly 

 the same way as before, except that we have now an upward 

 instead of a downward movement. — until the stirrup 

 stops moving in this direction. Let us remember by all 



