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Psyche 
[March 
problem with the oscillographic trace and a barely detectable clock- 
wise curvature of the femur tip relative to the base in ib and ic. 
This is caused by the fact that a video field is a metachronic series of 
241.5 lines each representing a “shutter speed” of 1/15,750 sec. The 
scanning time of the femur image in PI. ia is about 45 lines of 2.86 
msec. In other words, the tip of the femur, which is moving in an 
arc to the left, is imaged nearly 3 msec earlier than that of the femur 
base. Further magnification on the screen would result in greater 
temporal displacements and greater artifact in the shape of the organ. 
Any attempt to measure angles of rotation or points of displacement 
must take into account the video scanning time of the specific image 
and its vector relative to the vertical trace. 
7) Inability to record events after passage of the scanning trace: 
it is usually desirable to superpose the oscillotrace along the bottom 
of the video field (PI. ia-e) where the action is less likely to be 
obscured. However, the lower portion of the field will be scanned 
milliseconds after the action in the center. Nevertheless, visual- 
acoustic synchrony can be computed as shown in PI. id. The selec- 
tion of the horizontal sweep setting of the CRO is determined by the 
duration of the longest acoustical signal and should be about 40 or 
50 msec longer, so that the oscillotrace of the entire action can be 
visualized in one sweep, and traces in successive frames can be cross- 
referenced. The additional time allows some time before and after 
the signal on the screen so that the beginning or the end of the signal 
and its causative motion aren’t lost in the CRT retrace time, the 
vertical blanking interval, nor at the sometimes distorted edges of the 
monitor screen. Sometimes traces are badly reproduced or oriented, 
but constant inspection of the VTR 2 monitor will allow such mistakes 
to be corrected immediately by duplicating the sequence again. 
8) An alternative method to achieve visualization of motion-sound 
synchrony is shown in Fig. 1 and PI. if. Here the CRO is laid on 
its side so the oscillotrace will sweep from top to bottom of the 
camera pickup tube. The external trigger of the CRT electron-gun 
is triggered on the electronic transition from the vertical sync to the 
start of the first horizontal scanning line of the video field. The hori- 
zonal sweep of the CRT is set to equal the time constant of the video 
field (15 msec per sweep or 1 cm/msec), thus only the sound re- 
corded during the video scan will be oscillographed. The oscillotrace 
peaks appearing at the same horizontal plane as the video-recorded 
movement will be relatively synchronous with that movement, with 
