Fig. 5. Trajectories in “joint angle space” during grooming of each site for animal with all legs intact (A–C, E) and for animals in which EMGs were implanted in one hindleg and adjacent legs were removed (D, F).A–D, Each open symbolindicates the femoral elevation angle (x-axis) and the tibial extension angle (y-axis) calculated from one pair of digitized video images. Sequential open symbols are 1/60 sec apart. Arrows indicate the sequence of points when it was the same for all cycles shown. InA and C–F, joint angles are for the hindleg; in B, joint angles are for the middle leg. A, B, Three consecutive cycles of grooming for hindleg grooming of the posterior abdomen and middle leg grooming of the anterior hindleg coxa from the episodes in Figures 1 and 4, respectively. In each case, open squares indicate the first cycle, open circlesindicate the second cycle, and open triangles indicate the third cycle. C, D, Comparison of joint angle trajectories for grooming of the three sites by the hindleg. One cycle each is plotted from the episodes in Figures 1, 2, 3(for C) and from the episodes in Figures 6, 7, and9E (for D), using open symbols (circle for ventral hindleg coxa;square for posterior abdomen; trianglefor ear). The corresponding filled symbol in each case indicates the “center of mass” of the cycle, i.e., the mean femoral elevation and mean tibial extension values. C, All legs intact. D, EMG experiments. E,F, Center of mass of each cycle is plotted for all analyzed cycles of hindleg grooming of each site; symbols as inC and D. E, All legs intact; F, EMG experiments.