Travelling at a low speed is one of the important characteristics of PSC. However

the papers reported so far were almost the results of observations on individuals or a small number of subjects

and there still lacks of the re- sults of observations on the large sample.In order to remedy the shortcomi- ng in this respect

1100 times of observation have been made on 80 subjects with marked PSC in our laboratory.PSC was evoked by electrically stimu- lating the acupoints below the knee or elbow joint and the velocity of PSC was measured with a stop watch or with the add of a physiograph. The result demonstrate that the velocity of PSC was within the range of 10 cm/sec in most of the cases under observation and was basically steady in the same individual.It is particularly to be noted that PSC

evoked by sti- mulating the acupoints below the knee joint

travelled rather slow through the trunk than through the lower limb.In contrast

the paraesthesia was always skimmed over the trunk in sensory Jacksonian march.The comparison is obvious.It is well known that the representative area of trunk in SI and posterolateral ventral nucleus of thalamus are by far smaller than that of the upper and lower limb.However

the velocity of PSC travelling through the trunk was rather slow than that throagh the lower limb.This is hard to explain from the angle of“the spreading of excitation in CNS”.The fact that the velocity of PSC was markedly influenced by the variation of the skin temperature also suggest that there may be a certain substantial process proceeding along the channel during the advance of PSC.The above results further support the view point of“the integration of periphery and CNS under the guide of the substantial process proceeding along the channels in respect to the mechanism underlying the formation of PSC.