Thus I have endeavour’d to shew some of the secret Advantages accruing to us from the frequent Use of Exercise; and by which it will appear, that the Fluids of the Body are of such a Texture, as will admit of Improvement from the greatest Rapidity of their Current, that is consistent with the Organs thro’ which they are convey’d.
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 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.
These are some familiar Instances of the Sense we have, after what manner we come to acquire more Strength upon the Use of Exercise, and which every Man almost may recollect, that he has experienc’d more or less in himself; tho’ in other Cases the solid Parts are always strengthening by Exercise, without so plain a Sense of it, as in the Instances above mention’d; as we see what excessive Strength some Men gradually acquire by a constant Practice of vehement Motions, begun when they are young, which growing upon ’em by degrees, they are not so sensible of the Encrease of it. This is the Case of Tumblers, Rope-dancers, and the like, in whom the Nervous and Solid Parts must be incomparably more wound up, more tense than in other People; and thus we see the strongest Men are often thin and Raw-bon’d, as we call it; that is, tho’ daily hard Labour, and great Perspiration carry off a great deal of the grosser Fluids of the Body; yet are the Muscles not Flaccid, but Tense and Firm, capable of greater Actions than the Muscles of those who seem to have a better Habit of Body; which plainly indicates, that Exercise does communicate some Strength to the Nervous Parts, which cannot be any other way procur’d; and that we may argue from the greater to the less; that if healthy Persons may acquire such monstrous Strength by Use, People that are Valetudinary may, by setting themselves upon a resolute and diligent Practice of moderate Exercise, obtain a proportionable Increase of Strength.
It may be expected, perhaps, that I should endeavour to explain, how the Fibres come to receive a greater Power to act, by being often put upon Action, and to shew wherein the Elater, the Spring of the Solids, does consist; but this has been attempted so largely by an Eminent Author, Dr. Baglivi, and so much to the Disgust of very many, that it’s better to rest contented with plain Experience, than to frame an Hypothesis for the Modus of so abstruse a Method of Nature, which, in all likelyhood, Mankind will ever be ignorant of; but as far as we may reasonably guess, by frequent Distension the Nerves receive a greater quantity of Animal Spirits, because the Limb which is most us’d, grows biggest; and there is reason to induce us to suspect, that the Fibre it self strengthens by Use, has a peculiar Faculty to exert it self more and more, as often as the Imperium Voluntatis, the Fiat of the Will, sets it upon Motion. But unless we knew the Bond of Union, and understood how the Rational Soul acts upon the Animal Powers, we must be content to be most ignorant, the nearer we approach in our Disquisitions to that Union; but the Experimental Knowledge of these Parts sufficiently reproves those who hope to be deliver’d from some Distempers seated in the Solids, without acting suitably to the Nature of the Solids, the Subject of their Distempers: As for Instance; Suppose a Person, by frequent and unnecessary Use of the Bagnio, and more unnecessary Bleedings; by the Use of hot Liquors, and a perfect Disuse of all Bodily Exercise; by Passions of the Mind, and other Irregularities, is brought into the very worst of Hysterick Symptomes, with a Flaccidity and Relaxation of the whole Nervous System; How ridiculous is it, for such a Person to expect to be perfectly restor’d to a firm Habit of Body by internal Alteratives, and Methods little different from those things which occasion’d the Distemper; which tho’ they may give wonderful Relief in the Paroxysm, yet can never restore the Tone of the Solids, which must be treated in a manner proper to themselves, by Frictions, Exercise of the Body, the Cold Bath, and the like; which are very likely to be able to succeed to a perfect Cure? For why ought we not to suppose, that as all Fluids have more or less a Tendency to purifie and exalt themselves by Fermentation, the Solids should otherwise have a Propensity proper to their Make, to recover themselves by a due Tension? And what can be more reasonable and natural, than to conclude, that if a Supine and Luxurious Course of Life has enervated the Body, an Active and Vigorous one should restore it? If it be objected, That gentle Emeticks have gone a great way towards procuring a perfect Recovery from some Hysterick Cases; I have premis’d already, that they act upon the Fibres, and put ’em upon frequent Contractions, much after the same manner as a total Exercise of the Body; and therefore in this last Case, where the first Passages are not in Fault, their way of acting illustrates what I assert, that the Solids must be made to strengthen themselves, and recover their Spring by frequent Endeavours. But for Alteratives, strictly taken, I think it may be justly a Question, Whether there is that Medicine in Nature, that can remove this Distemper, when it has been of long continuance, tho’ the World has been taught above an Age ago by Paracelsus and his Followers, to expect what I fear is not within the Extent of Nature; and the Impudence of Empiricks is so great, as to promise every thing that is absurd and Romantick; which keeps People up with hopes, that they may be so happy as to meet with that mighty Secret, which even in the quantity of a few drops, shall as it were charm away the most troublesome and riveted Distemper, and so instead of being Cur’d, they are Kill’d by Expectation; when the Power of Recovering their Health was in their own hands, if they had resolutely set about the proper means; like the Country-Fellow in the Fable, who when his Cart stuck fast in the Mire, must needs be calling upon Hercules to come and help him, when with setting his own Shoulders to the Wheels, he might easily have got clear.
But moreover, a second Advantage arising from Exercise, is, that it gives the Solid and Nervous Parts a grateful Sensation, which in some Cases is not contemptible; a gentle Agitation of the Spirits being able to remove some Pain situated in those Parts, which perhaps nothing else would remove so surely and so soon. To explain the manner of this by a trivial Observation (if any thing in Nature can be so) let us consider, how we can separate the Cuticle from the true Cutis without Pain; it can’t be done with an Instrument without extream Pain, it can’t be done by Vesicatories without some Pain; but it may be done with Chafing without any Pain at all, or rather with some Pleasure, till you leave off Rubbing, and the Air comes to act upon the naked Fibres. Now this can’t be attributed to the Heat of the Part only, for then hot Medicines apply’d to the Skin; would do it as easily but must be suppos’d to be owing to a certain Agitation of the Spirits in the Extremity of the Fibres, which affects ’em with so agreeable a Sensation, as to surmount even the Pain of a Separation of their Covering, the Scarf-Skin. Now it will be allow’d by all, that whatsoever Sensation there is in the Extremity of the Fibre, the same there is at the Origine of it in the Brain; so that a pleasant Sensation in the Extremity, must needs be the same in the common Sensorium; and therefore ’tis easie to account for the good Effects of Frictions of the Limbs in some sort of Fits, by giving a new and different Motion to the Spirits, and thereby disengaging ’em from their disorderly Motions. And then if acting thus upon the Extremity of the Fibres produces such an Effect in ’em, ’tis natural to imagine, that that Motion, or gentle Concussion, which much after the same manner, in some proportion acts upon the whole Body of the Nerves, must affect ’em with a Sensation proportionably agreeable, and may prove sufficient to dispose the Spirits to leave their Displosions, and irregular Motions, when they happen to be so discompos’d, and consequently remove the troublesome Watchings and painful Symptomes occasion’d by those Displosions, when other Means prove ineffectual. Thus we see how natural it is for those Hysterick Persons, who are vexed with obstinate Watchings, to fall into a true and refreshing Slumber, by the Motion of a Chariot, when Opiats will have no effect upon ’em, but rather encrease their Watchings: The Spirits being the most stubborn Part of the Animal Oeconomy, and not always to be compel’d, even by that potent Drug.