MECHANORECEPTORS AND BEHAVIOR 



355 



The form of the canals and their function— The important studies of 

 Steinhausen (1933) on the labyrinth of the pike showed that during rotatory 

 acceleration of the head the endolymph and cupula were rigidly coupled. 

 This lead him to develop the torsion-pendulum model of semicircular canal 

 function. 



Following Steinhausen, the general view has developed that the semi- 

 circular canals are responsive to angular accelerations and that linear acceler- 

 ations are registered by the other sense organs. Much evidence has been 

 accumulated that supports this view, although most recently it has been 

 shown that in some animals, including elasmobranchs (Lowenstein 1974), 

 the canals also respond to linear accelerations, presumably because slight 

 differences in density exist between the cupula and the endolymph (Gold- 

 berg and Fernandez 1975). 



Considerable insight into semicircular canal function was obtained from 

 elasmobranch preparations, in which the size, accessibility, and arrangement 

 of the nerve bundles permitted unit records to be taken from the afferent 

 fibres. The experiments, carried out on the horizontal canal of the dogfish 

 and on all three canals of the ray (Lowenstein and Sand 1936, 1940a, b), 

 established that at rest most units showed a steady discharge, which in- 

 creased during constant ipsilateral acceleration and decreased or stopped 

 during constant contralateral acceleration in the canal's plane (Figure 13B). 



I . ii I 



J 



3s 



psi lateral 



50 



40 



30 



ipsilateral 



3 ■► 



contralateral 



Seconds 



Figure 13 Directional responsiveness of horizontal semicircular canal and organ in Raja. 



(A) Tracing of single end organ discharge in response to continuous angular acceleration. 



(B) Changes in impulse frequency (s" 1 ) during ipsilateral and contralateral rotation (stop- 

 ping at arrow). (C) Change in impulse frequency during ipsilateral and contralateral rota- 

 tion at constant angular velocity (redrawn from Lowenstein and Sand 1940a). 



