most familiar degree of Tension; which we experience in Standing, which Posture has ever been esteem’d as a Tonick Motion. But the Stiffness or Strength of the solid Parts will appear more evident by that sensible encrease of the Strength, which Men experience when they set themselves upon any vigorous Exercise; which continues, till thro’ the Greatness of the Perspiration they grow tyr’d, and relax again; or, to borrow an Illustration from Beasts, It will appear by what _Jockeys_ observe, who when they design to take the Bearings of a Running Horse, that is, measure the Extent of his Stroaks, they usually let him gallop a Mile or more first, as supposing that he can’t come upon his Legs (as they term it) till he has run a considerable time; that is, he can’t strike out so far, tho’ press’d ever so much to it, upon his first setting out, as he can after he has run some time: which explains what I assert, That a proper or due degree of Exercise, enables the Nerves to dilate themselves sufficiently to take a greater Quantity of Animal Spirits, or some other way, to us unknown, gives ’em a better Tone, or Elater, and consequently fits ’em for more vigorous Actions. But to bring the Sense of this Tension nearer to a Case of Sickness; Let any Man reflect, how he found himself after an Acute Distemper, wherein the solid Parts were mightily relax’d by the Heat of the Fever; when a Man in that Case rises first from his sick Bed, and makes a shift to walk a very little in his Chamber, tho’ he quickly grows faint, and wants some Cordial to refresh him; that is, Tho’ his Vital Spirits sink, as the Antients lov’d to express it, yet he perceives a certain Stiffness, Tension, or Strength in the solid Parts, by that first attempt to walk, which never leaves him, but encreases daily, till he recover his perfect Health.