The Mind indeed is the first Principle of all Muscular Motion; but in such Cases as these, its Promptitude to Action or Habit being so great, it is in a manner surpriz’d, and cannot recover it self after the Spirits are with violent Force determin’d pursuant to the Representation of the Species. For, as in the former State of Things a Man is said to act Rationally, so this latter Case is call’d a Perturbation of Mind, that is, a Delirium; tho’ it is very manifest, that in reality the Defect is not in the Rational, but Corporeal Part; such Species being really presented to the Mind, upon which by the Order of our Constitution such Motions ought to follow in the Body.
Thus, for Instance, if the Liquor of the Nerves is, without the Presence of any thing hurtful, put into a Motion like unto that which a painful Impression makes in it, the same Bodily Actions must insue as proceed from Fear, Anger, or the like Passion, determining the Spirits towards the Muscular Parts; and a By-stander, who sees no reason for such a Representation made to the Mind, will presently conclude that the Person thus acting acts without or besides his Reason, that is, is Delirous; especially if the Hurry and Confusion of the Spirits be such, that not only one, but several different Species be at the same time presented to the Mind; for a Man in this Case may act the Part of one Joyful, Angry, Timorous, or the like, without any appearing Reason, and all this almost in the same Moment of Time.
In one Word, Deliria are the Dreams of those who are Awake; and as these in Us Sleeping are infinitely various and wonderfully Compounded, and all from the same common Cause, diversely pressing the Orifices of the Nerves, and thus making different Repercussions of their Fluid; and as we all know that this Confusion making the Representation of several Species to the Mind, there do hereupon follow, tho’ the Body seem now at Rest and in perfect Repose, such Motions in the Organs as are usually the Effect of the Arbitrary Determination of the Spirits thither; so We are now to enquire what Alteration of the Body made by this Venom, can be the Occasion of this Disorder and Tumult in the Nervous Fluid, which excites in the Party infected such surprizing, and almost contradictory, Representations.
Most of the Symptoms of those who are bitten by the Tarantula are at the first, that is, before they rise to a Delirium, plainly the same with those which the Bite of a Viper induces; without doubt therefore, as we have before observed of the common Spider, that it pierces the Flesh with its hooked Forceps, and at the same time instils from the Proboscis in the Mouth a liquid Venom into the Wound; so the like Claws in This (of which I have taken the Figure [(51)] out of P. Bonanni, very much magnified [(52)],) do serve to make Way for an active and penetrating Juice emitted from the same Part.
Of the Nature of which we may probably conjecture, that it is, when mixed with the Blood, being exalted by the Heat of the Climate, of so great Force and Energy, that it immediately raises an extraordinary Fermentation in the whole Arterial Fluid, by which its Texture and Crasis is very considerably altered; the Consequent of which Alteration, when the Ebullition is over, must necessarily be a Change in the Cohæsion of its Parts, by which the Globules, which did before with equal Force press each other, have now a very differing and irregular Nisus or Action, so that some of ’em do so firmly cohere together, as to compose Moleculæ, or small Clusters; upon which Account there being now a greater number of Globules contained in the same Space than before, and besides, the Impulse of many of these when united together differing according to the Conditions of their Cohæsion, as to Magnitude, Figure, &c. not only will the Impetus, with which this Fluid is drove towards the Parts, be at some Strokes at least greater than ordinary; but the Pressure upon the Blood Vessels must be very unequal and irregular; and this more especially will be felt in them which are most easily distended; such are those of the Brain, &c. And hereupon the Fluid of the Nerves must necessarily be put into various Undulatory Motions, some of which will be like unto those which different Objects acting upon the Organs or Passions of the Mind, do naturally excite in It, whereupon such Actions must follow in the Body, as are usually the Consequents of the several Species of Sadns, Joy, Despair, or the like Determinations of the Thoughts; and we shall readily pronounce one in this Condition, Sad, Joyful, Timorous, &c. and all without any apparent Reason or Cause; that is, in one Word, we shall say he is Delirous.
This is in some Degree a Coagulation of the Blood, which will the more certainly, when attended with an extraordinary Heat, as in the present Case, produce such like Effects as these, because the Spirits separated from the Blood thus Inflamed, and Compounded of hard, fixt and dry Particles, must unavoidably share in this Alteration; that is, whereas their Fluid consists of two Parts, One more active and Volatile, the Other more Viscid and Glutinous, which is a kind of Vehicle to the former; their Active Part will bear too great a Proportion to the Viscid; and thus they must necessarily be of more than ordinary Volatility and Force, and will therefore, upon the least Occasion imaginable, be irregularly determin’d to every Part; and hereupon will follow Tremblings of the Body, Anger or Fear upon a light or no Cause, extream Pleasure at what is but a Trivial Entertainment, as Red, Green Colours, or the like; and on the other hand, wonderful Sadness at any thing not agreeable to the Eyes, as dark and black Things; nay, ridiculous Laughter, obscene Talk and Actions, and such like Symptoms; because in this Constitution of the Nervous Fluid, the most light Occasion will make as real a Reflux and Undulation of it to the Brain; that is, will present as lively and vivid Species there, as the strongest Cause and Impression can produce in its natural State and Condition; nay, in such a Confusion, the Spirits cannot but sometimes, without any manifest Cause at all, be hurried towards those Organs, to which at other times they have been most frequently determined; and every one knows which they are in hot Countries and Constitutions.
We must however here remember what in the former Essay we mention’d of the Fluid of the Nerves, being immediately altered by the venomous Juice.
It will perhaps make this Theory more than probable, to consider that Baglivi [(53)], in the Dissection of a Rabbit kill’d by a Tarantula, found the Blood Vessels of the Brain very turgid, and the Substance of the Brain it self, that is, the Beginning of the Nerves, lightly inflamed, and with livid Spots here and there, the Lungs and other Viscera distended, with concrete glotted Blood, and large Grumes of Blood with Polypous Branches in the Heart, a large Quantity of extravasated Serum upon the Brain, which is (as he takes Notice) mostly observed in those Subjects which died by a Coagulation of the Blood.
Neither is it amiss to remark, that in a Chlorosis there is nothing preternatural but an infarctus of the Arteries, and hence a retarded Circulation, from an Evacuation suppress’d; and in this Country too much Heat; that is, a beginning Coagulation, together with an Inflammatory Disposition.
In short, Bellini has at large demonstrated, how Deliria, as well as Melancholic as Manaical, do proceed from a State of the Blood and Spirits, not unlike to that I have here described.