HORIZONTAL RECTILINEAR MOVEMENTS

Abstract

Rabbits whose eyes were covered were moved 20-30 cm.in 1-2 seconds on the horizontal plane in the sagital or frontal direction, giving rectilinear accelerated stimuli composed of acceleration and deceleration.The attitude of the head, the trunk and the limbs during the movement were observed.Electromyograms were taken from the deep nape muscles, the deep dorsal muscles, and the extensor and the flexor muscles of the anterior limbs.The same was studied in the rabbits with unilateral or bilateral labyrinthectomy or decerebration.1.When the normal rabbits were moved in the sagital direction, the electromyographical findi- ngs of the deep nape muscles did not correspond to the posture, the electrical discharge being decreased by foreward acceleration and increased by the backward acceleration.In the accelerated stage of the movement in the frontal direction, the decrease of the discharge was seen in the muscles on the side to which the movement was directed, and the increase of the discharge was seen in the muscles on the other side.The reaction of the decerebrated rabbits was almost the same to that of the normal rabbits, However, the interval diagrams of discharge of the deep nape muscles were usually more smooth than that of normal rabbits.2.In the unilaterally labyrinthectomized rabbits, the continuous regular discharge was not demonstrated in the deep nape and dorsal muscles on the healthy side.In the bilaterally labyrinthe ctomized rabbits, the continuous regular discharge was hardly demonstrated in the deep nape and dorsalmuscles on both sides, No respense was observed for the accelerated stimulation.3.In the bilaterally labyrithectomized rabbits, the response of the anterior limbs was usualy difficult to demonstrate, showing opposite tendency to that of decerebrated rabbits.On the electro- myograms of the anterior limbs, normal rabbits showed two types of response to the rectilinear acceleration seen in bilaterally labyrinthectomized and decerebrated rabbits.4.The labyrinthine muscular innervation to the deep nape and dorsal muscles seemed mainly to be contralateral.The vestibulo- spinal muscular response was more remarkable in the deep nape muscles and dorsal muscles than in the limbs.