But, _Lastly_, to put these things past all Doubt, by a well-known Observation; we need but consider what is sometimes the Effect of too much Exercise upon taking a Purging Medicine, and that is an _Hypercatharsis_. The Particles of the Drug being sublim’d, and render’d more active by the greater Agitation in the Body, display a much greater Violence than otherwise they would have done in a Person of the same Constitution, who had given himself to Repose. This has been long ago observ’d by _Hippocrates_, in the _fourteenth_ and _fifteenth Aphorisms_ of his _fourth Section_; From whence it naturally follows, that the Motion of the Body may cause great Alterations in the Blood; may very much improve any Juices that are convey’d into it; and that in some nice Cases, where the Alterative Physick is very mild, and perhaps given in too small a Quantity, it is absolutely necessary to have Recourse to the Use of Exercise, to give an Energy to it, that it may produce the desired Effect. Having thus briefly consider’d the Power of the Use of Exercise, I come now to shew, after what manner it affects the Solids; and that I take to be, _first_, by giving a greater Tension to ’em, or restoring the true Tone of the Parts, by curing the Relaxation by which they were weakned. That I may explain what I mean by this _Tension_ or _Tone_ of the Parts, it will be necessary to consider, _first_, how great is the Benefit we daily receive by only changing the Position of our Bodies, from an Horizontal to an Erect Position when we quit our Beds, where in the time of Sleep the Body has been relaxed; and this will appear best by the ill Consequences which follow upon a Person’s being confin’d by an Accident to keep his Bed for a few days; for such a one always finds upon his getting up again, that his Spirits are disorder’d; he finds himself Vertiginous in some measure, and a great deal weaker than he was, before he betook himself to that Posture: From whence it evidently appears, that Standing or Sitting, the familiar Exercises (if I may so call ’em) of the most sedentary Life, are absolutely requisite to keep up the Balance on the part of the Solids, even in a State of Health, and that more violent Exercises are as requisite to recover this Balance, when sunk by Sickness. I know it may be objected here, that this Observation is chiefly owing to the Custom of changing the Posture of the Body alternately, in such a space of time, and that the breaking of that Custom occasions those Disorders; but this will not suffice; for an erect Position is essential to the well being of the Body of Man: and if the Infant was not at such an Age brought to it by degrees by the Nurse, tho’ it might grow up to the Bulk of a Man, and live many Years, yet it would be a kind of bedridden Creature; Paralytick, as to the Use of its Limbs, tho’ with the Sense of Feeling; and much weaker internally, for want of that Advantage, which the Fluids receive from the Solids by this