Abstract
To inquire into the physiological relationship between the unidirectionality of the labyrinthine reflex to rotatory stimulation and the unidirectionality of the optokinetic reflex five leghorns, whose eyes were covered unilaterally, were rotated with an angular acceleration of 1°/sec2 for a minute and the following facts were disclosed.
(1) During rotation the deficiency due to the unidirectionality of the optokinetic reflex is compensated for by unidirectional excitation of the labyrinth and perrotatory head nystagmus occurs. (2) The purpose of this compensation exists in inducing head nystagmus and thereby enabling the individual to perceive moving objects one by one and to keep the body in equilibrium during rotation. (3) In considering nystagmus from the point of view of evolution, it is inferred that the unidirectionality of the optokinetic reflex existed at first and, for the purpose of compensating for this unidirectionality, semicircular canals with their unidirectional nature evolved.
