This experiment was made with the object of examining to what extent the disturbance of muscle action, which was required for maintaining of various standing postures, was brought about by the elimination of vision. Using two dogs, electromyographic recordings of successive discharges of single NMU were taken from the gastrocnemius, the biceps femoris, the quadriceps femoris and the flexor carpi ulnaris under four conditions: NV (the normal standing with vision), NN (the normal standing without vision), TV (the tripedal standing with vision) and TN (the tripedal standing without vision). Dogs were blindfolded by double black cloth when without vision, and were subjected to 3 or 4 repitition under each condition on different days. As a rule, the variation of the time series of discharge intervals is separable into two components : the slow undulation and the irregular fluctuation, and, therefore, discussions were made on respective components. (1)The variation of discharge intervals tends to be augemented a little by the visual elimination but this tendency is not highly distinguishable. (cf. Chart 1) (2)The visual elimination has marked effects on the slow undulation, but the extent of their manifestation is not uniform, that is, it is different according to kinds of postures and muscles involved. In the normal standing posture, the process of the slow undulation becomed rhythmic in Some muscles but it in others is subjected to only slightly noticeable changes. (cf. Table 1 and Chart 5) As a rule, when without vision, the amplitude of the slow undulation increase markedly, espescially in the tripedal standing posture, and the process of the slow undulation becomes strikingly unstable in the tripedal standing one, regardless of designation of muscle. (cf. Chart 3 and 5) Furthermore, in the tripedal standing posture, the effects of the visual elimination are more remarkable in the muscles which are concerned in the fixation of mechanically unstable joints like the knee joint, than in those which fix mechanically stable joints like the hock joint, that is, the former is more dependent upon vision to maintain stable muscle action than the latter. (cf. The quadriceps femoris and the gastrocnemius in Chart 3. And note that the marked increment of the inclination of the γ^^--A curve in TN occurs in the former, in comparison with the latter.) Thus, it follows that the manifestation of the effects is more striking in the tripedal standing posture than in the normal standing one. This indicates that the visually conducted adjustment of muscle action is more important in the insecurity of the bodily balance like in the tripedal standing posture. (3)It seems that the visual elimination has no effect on the irregular fluctuation. From these results, it has been demonstrated that stable maintenance of the various standing postures, especially the asymmetrical standing one, depends upon vision to a considerable extent.

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