So that there is at this time a kind of _Relaxation_ or Loosness of the moving Fibres of the several Members; or at least such a quiet Position and State of them, by which all the _Antagonist_ Muscles are in an _Æquilbrium_ and Equality of Action, not overpowering one another. For this indeed seems to be one great Design of Sleep, to recover to the Parts overstretched by Labour their former _Tone_ and Force; and therefore we do naturally, when composing our selves to _Rest_, put our Body into that Posture which does most Favour the _particularly_ wearied Limbs, and conduce to this end. In the next place, it is very plain that there is in _Sleep_ not only a Rest and Suspension from Acting of most of our Bodily Organs, but even of our _Thinking Faculty_ too. That is (for I would prevent Cavils) a ceasing from such _Thoughts_ as when Waking We are exercised about, which we do _Reflect_ upon, and _Will_ to employ our Mind with. For though _Dreams_ are Thoughts, yet they are but imperfect and incoherent Ones, and are indeed either so faint and languid _Representations_, as to be consistent with our _Sleep_, as some may be; or else if they be strong and lively, they are, as every one knows, the _Interruption_ and Disturbance of It. From hence It will follow, That the _Motion_ of the Arterial Fluid must be, _Ceteris Paribus_, more sedate, even and regular, in the time of _Sleeping_ than _Waking_; For, besides the various Alterations which in the latter State this receives from the several _Passions_ of the Mind, the very _Contractions_ of the Muscles themselves in Exercises of the Body do differently forward its Course; whereas in _Sleep_ the force of the Heart and Pectoral Muscles being more constant and uniform, gives it a more calm and equally continued Impulse. Hence also it will come to pass, that the _Influx_ of the _Liquor_ of the Nerves into the Organs of the Body, as also Its _Reflux_ towards the _Brain_, is in Sleep either none, or very inconsiderable; that is, that this Fluid has at this time but little or no _Motion_. For ’tis Muscular _Action_ and _Sensation_ that require It to be thus determin’d, this way or that, which are now hardly any. And yet by the arrival of Blood at the Brain, this _Juice_ will still be separated there, fit to be derived into its Canals or Tubes. So that by this means there will be a kind of _Accumulation_, or laying up in Store, of _Spirits_ for the Offices and Requirements of _Waking_.