THE ROLE OF THE SEMICIRCULAR CANALS IN CAUSATION OF MOTION SICKNESS AND NYSTAGMUS IN THE DOG

The discrete surgical inactivation of all six semicircular canals was found to be equivalent to bilateral labyrinthectomy in eliminating motion sickness in dogs, even though the otolith organs remained functional. Inactivation of fewer than six of the canals reduced the susceptibility of dogs to motion sickness, but to a lesser degree than did inactivation of all six canals. These findings are consistent with the theory that stimulation of the semicircular canals causes motion sickness.Rotatory tests of the horizontal and vertical semicircular canals and tests of an otolith reflex, preoperatively and postoperatively, yielded information about the basic functions of the semicircular canals and confirmed that the surgical procedures had accomplished their objectives without unintended damage to other vestibular receptors.