792 



THE SENSE OF EQUILIBRIUM 



continued for a brief period of time, a point will be reached when the 

 walls and the water move with practically the same velocity. Im- 



FiG. 402. — Diagrammatic Representation of a Model Illustrating the Deviation 

 OF THE Hair Processes of the Ampulla. 

 D, disc rotated by hand; T, circular glass tube filled with water; B, bulbular enlarge- 

 ment containing a long camel's hair brush, vertically placed. 



mediately upon ceasing the rotation, the walls are brought to a stand- 

 still, while the water continues to move in this direction until it is 



finally stopped by the friction. These 

 phenomena may be illustrated in a more 

 striking manner with the help of a cir- 

 cular glass tube filled with water and 

 enlarged at one point for the reception 

 of a bundle of soft hairs placed trans- 

 versely into its lumen (Fig. 402). When 

 rotated, this primary and secondary 

 dissociation between the movements of 

 the walls of the tube and the water are 

 now made more evident by the devia- 

 tion of the hairs, first against and then 

 in the direction of the rotation. 



If this hydrodynamical principle 



is applied to the semicircular canals, 



Fig. 403.— Diagram Illustrat- it must be concluded that the move- 



iNG THE Position of the Hair Pro- ment of the head gives rise to a move- 



cesses of the Ampulla on Rotation ^^^^ ^f ^^le canals situated in this 



of the Canal. . mi- • ^ ^ 



A, the canal being moved in the Particular plane. To begm with, the 



direction of the black arrow, the en- endolymph lags behind the Walls of 



T^® the canals, but soon attains the same 

 speed as the latter. Lastly, it con- 

 tinues in this direction even after the 

 canals have ceased to move until its 

 motion has again been arrested. This 

 implies that the hair processes are first 

 turned against the rotation, then vertically into the fluid, and lastly 



dolymph at first lags behind, 

 hairs processes are deviated against 

 the rotation from a to h. On stop- 

 ping the rotation of the canal, the 

 endolymph is carried onward in the 

 direction of the red arrow deviating 

 the hair processes from a to c. 



