Refluctuation

Now the Reason, or rather the Cause from whence this Imbecility or Weakness of the Head did proceed is, for as much as there is a Penury or lake of Spirits by their Refluctuation to their proper Fountain and Center, and that occasion'd by Sleep, they are not so quickly and readily distributed and diffused again through the Organs of the Senses.

Source: wiktionary

And it is more probable, that the Impressions made upon our Organs produce an Undulation and Refluctuation of the Spirits, or of Newton's materia subtilis in the Nervous Fibrils, which reaching the Sensorium, gives us the Ideas of objects; than that these Ideas should be excited by these Vibrations themselves."

Source: wiktionary

It is striking that the "sensorial motions" do not hinge on vibration or the flow of the spirit like the inflowing of animal spirits through the nerves to the muscles ("The sensorial motions...are not here supposed to be flutuations or refluctuation of the spirit of animation; nor are they supposed to be vibrations or revibrations") , but on the motions “peculiar to life."

Source: wiktionary

[…] production during years of stress, and its comparative refluctuation when social conditions are easy and prosperous.

Source: wiktionary