1. A peculiar phase other than p. p can be seen in human natural sleep, . which might be called reverse paradoxical phase (r. p. p), for the relation between EEG pattern and the activity level of many other physiological. functions is the reverse of that in p. p.2. P. p and r. p. p are two different manifestations of the dissociation between EEG and many other physiological activities, especially vegetative functions.3. The fact that p. p is apt to appear at the end of each single sleep cycleand r. p. p comes at the beginning or in the middle of each single sleep cycle could account for the phasic shift of changes in EEG and other physiological functions.4. The prominent occurrence of p. p in the latter half and r. p. p in the first half of the natural night sleep could be attributed to the difference in distribution pattern of activity level of each physiological function. For instance, more occurence of EEG III can be seen in the earlier period of the night sleep, while the depressed or minor activity of GSR, blood pressure is distributed more in the latter half of the night sleep.