姿勢と眼振

1) We devised a new method to provoke nystagmic responses of cervical origin in which a rabbit's trunk is hung and fixed with cloth while the head and four limbs are unrestrained. The head of the animal is then rotated around its longitudinal axis at the rate of 90 degrees either to the right or to the left. The nystagmic responses provoked in this way are recorded at the maximum point of torsion of the neck using ENG. We found that the appearance of nystagmic responses of cervical origin was more marked in the neck torsion test referred herein than in those reported by Philipszoon. The nystagmic responses thus provoked were oblique and directed to the same side as that of the torsion of the neck.<br>2) We made a series of experiments in which nystagmic responses of cervical origin were tested in the method described in (1) with the following postures: i) a posture of standing with the four limbs on a horizontal platform, ii) a posture of standing with the four limbs on a platform inclined forwards, iii) a posture of standing with the hindlimbs on a horizontal bar, iv) a posture of standing with the forelimbs on a horizontal bar, v) a posture in which the trunk and four limbs are fixed to a cage, while the head is unrestrained, vi) a posture, in which the hindlimbs are pulled and stretched down-wards, and vii) a posture in which the forelimbs are pulled and stretched downwards. From a series of experiments we found that the appearance of nystagmic responses of cervical origin was the most marked in the postures described in ii) and iii), whereas nystagmic responses were fewer in the posture described in vi). The nystagmic responses induced in the postures described in i), iv) and vii) were similar to that induced in the posture described in (1). In the posture described in v), most animals showed deviation of the eyes with some exceptions in which a weak and short-lasting nystagmic response was observed. Taking into account the hitherto reported results and our animal experiments which were recently performed, we concluded:<br>(a) The method referred to herein is useful in producing nystagmic responses of cervical origin.<br>(b) The proprioceptors of the hindlimbs, which are involved in the maintenance of the standing posture, play a major role in the promotion of nystagmic responses of cervical origin. In contrast, no significant role has been found in the proprioceptors of the forelimbs.<br>(c) The proprioceptors of the hindlimbs exert an inhibitory action on the development of nystagmic responses of cervical origin when the flexors and extensors of the hindlimbs are simultaneously stretched. In contrast, in the case of stretching both kinds of muscles of the forelimbs no significant effects have been found with regard to the appearance of the above-mentioned nystagmic responses.<br>(d) The results obtained in the present experiments indicate that the physiological meaning of nystagmic responses should be interpreted in relation to the bodily reflexes which appear simultaneously with the nystagmus.