fections, vertigo and tremblings. Thefe re the principal diseases of the fpirits, which eing once known, the others may be eafily ccounted for.

The phrenetic delirium is a continual feer of the fpirits. A fever is only a fermenation of the blood, increased either by the xaltation of fome of its principles, or by he mixture of fome extraneous matters. When any principle of the fpirits is exalted, For when fome extraneous matter gets among hem, their natural fermentation increases, Find a kind of fever arifes in that fluid; which hiefly happens when the blood being rareied by the fever, and diftending the ftrainers, he fpirits do not come out of them pure, out carry along with them a coarfe falt, or ome other matter, the mixture whereof difurbs their regular motion. Such a difturbed motion occafions all the fymptoms of phrenfy, and offers the fame indications as continual fever. This motion of the fpirits must be abated by frequent bleeding and cooling remedies; emetics and purges muft difentangle them from an extraneous mix. ture, and anodynes and narcotics reftore them to their natural state.

The mania may be well deemed a lingering fever in the fpirits; for in the blood a lingering fever differs only from a continual fever by its duration and violence, which, being fometimes very great at first, is quickly abated; The fame causes that produce it, keep it up in that degree of diminution to which it is reduced. What is the mania but a longer and continual phrenfy? It begins fometimes with violence; but, being quickly allayed, continues in a moderate ftate.

In this cafe, it is not the blood rarefied by a fever, which diftends and relaxes the ftrainers of the spirits; they are fuch by their own conformation, which is either natural, or occafioned by fome excefs; from thence proceeds that ftubborn mania, which is proof against all remedies; it being extremely difficult to restore the tonus of thofe parts Or fome principle of the fpirits is exalted by fome excefs; and in this cafe the mania may be cured by the firft remedies; but the fame excess never fails to produce it again, and at laft it grows incurable.

:

The ufual method of curing the mania feems to be grounded upon that theory; the fame remedies are made ufe of for that disease as for a lingering fever: Phyficians allay the humours, temper the fpirits, and purify them by bleeding, purging, emetics, ábforbents, coolers, bathing, whey, and other remedies of that nature. We reckon emetics among them, because we are difCourfing of the lingering effential fever, the

principal whereof lies fometimes in the ftomach.

There is another lingering fever, called fymptomatic by phyficians, which depends upon another difeafe, fuch as an ulcer. To this may be compared melancholy, which is a particular mania about a single thing a It depends upon an impreffion made in one part of the brain by fome object, with which the fick perfon has been ftrongly affected: and as the blood, going through a vitiated part, contracts a matter proper to keep up a lingering fever; in like manner the spirits, going through that part of the brain which has been strongly affected, get a vicious configuration, which occafions the melancholy delirium. Hence it is that this kind of mania, befides the common remedies, requires fome others, to reftore and ftrengthen that part of the brain which has been affected; as, in a fymptomatic fever, the ufual remedies are attended with specific ones for the part affected.

It may perhaps be a matter of furprise, if we fhould reckon epilepfy among intermitting fevers; but the conje&ure will appear lefs bold by comparing together these two difeafes: Epileply has its periodical returns as well as the fever; and if they are neither fo regular, nor fo frequent, it is because the fpirits do not run fo regularly as the blood, and becaufe, being more volatile, they have alfo more strength to overcome the obstacles that might bring again the paroxyfm.

There are two ufual causes of intermitting fevers: Some believe they proceed from an acid chyle, or some other humour, which gets into the blood at feveral times. Others will have it that they are occafioned by an obftruction in fome part of the body, and in the whole habit at the extremity of the capillary veffels. In like manner physicians acknowledge two caufes of epilepfy. One of them is an acid humour, which the blood contracts in fome part of the body, and which being conveyed into the brain, by the laws of circulation, is feparated from it together with the fpirits. Such are the epilepfies, which depend upon fome imperfection of the parts lying out of the brain. The other caufe is an obstruction in the brain itself, occafioned either by an extraneous matter, or by the compreffion of the adjacent parts, or by an imperfect conformation either natural or accidental. Such epilepfies are called idiopathic by phyficians.

In the beginning of a fever, there happens fometimes a kind of interception of the circulation of the blood, which occafions a fhivering. The obftruction, which is the caufe of epilepfy, fufpends for fome time the motion and diftribution of the fpirits; and

this

this is the reafon why the fick perfon falls and lofes his fenfes. Some intermitting fevers are attended with no shivering, or only with a small one. There are alfo fome fits of epilepfy in which the fick perfon does not fall, and others in which he only grows a little giddy, without lofing his fenfes.

When the fhivering is over, the blood, being difturbed by that acid matter, ferments irregularly; or, having overcome the obftacle that ftopped its courfe, it runs with greater impetuofity, like thofe rivers, the waters whereof, being for fome time fufpended, overflow with more rapidity and violence; and the fick perfon, who had been for fome time without any motion, struggles and tumbles with irregular motions.

The blood, being thus agitated, carries along with it the feverish matter, and fubdues it: That matter comes out with the fweat, or finks into the primæ viæ; which puts an end to the fit, till a new one begins again by another like matter, produced in the blood, or gets into it from elsewhere. In like manner, the epileptic matter being carried away by the rapid motion of the fpirits, and wasted by their volatility, the fick perfon recovers his fenfes, and the fit is over, till a new one is occafioned by a new obftruction.

As for what concerns convulfions and convulfive motions, the former feem to be only a fwelling of the nerves, or a tenfion, occafioned by the great plenty of spirits determined towards that part which foffers an irritation, or by an impreffion made in the brain itself; fo that the fpirits have then the fame effect upon the nerves, as the obfructed blood, upon the flesh in the phlegmon. Hence it is that the confequences of both difeafes are equally dangerous, and that fuch remedies ought to be used, as are proper to moisten and relax the ftretched fibres, in both diffempers, and then thofe which are able to restore their elafticity, and to drive away the obstructed humour.

As for convulfive motions, either they begin in the parts or in the brain. Whether they begin in the one or the other, it is always an obftruction occafioned by fome matter, or by the great plenty of spirits conveyed to the part by its irritation, or determined by fome other caufe: And as the blood being obftructed in an inflammation, either external or internal, occafions a fever, in like manner the fpirits, when obtructed, break out into irregular motions, and, getting into the mufcles, move them against the will; from whence it appears that convulfive motions are like a fever, which follows an inflammation.

A malignant fever muft needs have an af

finity with some disease of the fpirits, as with madness, and other diseases of that kind. A malignant fever destroys the contexture of the blood to fuch a degree, that it diffolves; or feveral concretions are occafioned by it, which produce fo many dismal symptoms with which they are attended. Hydrophobia does so dissolve the contexture of the fpirits, that they fly out into many irregular motions, which disturb reafon and diforder the animal oeconomy. We omit explaining the principal fymptom, from which that difcafe has its name, as being too long to be here inferted.

In the vertigo and tremblings there hap❤ pens fomething fimilar to what happens in palpitation: That disease, which is reckoned among thofe of the heart, is nevertheless a fymptom of the motion of the blood interrupted, either by clods, or by a wrong conformation in the heart, or in the arteries. In fuch cafes, all the blood not being able to come out of the heart, what remains is driven back by the contraction of that vifcus ; and this fecond impreffion, added to the first, makes it go back by a circular motion, like a whirling, which communicates to the heart and arteries that precipitate motion, and that kind of trembling, which makes the palpitation.

To explain the vertigo according to that notion, it must be fuppofed that a circular motion is always compounded, either of many ftraight motions, which the frequent meeting of our bodies diverts at every moment, or of two opposite but unequal determinations.

If therefore the fpirits, running along a nervous tube, find from time to time small rubs, occafioned either by obftructed matters, or by the impreffion of the adjacent bodies, their direct motion will be inter rupted; and, the spirits being forced to turn afide at every moment, must move round; or the fpirits being forced by the meeting of an unfurmountable obftacle to run back, and being all along preffed by those that defcend, which have a greater force than those that flow back; the fpirits, I fay, being driven by two contrary and unequal motions, cannot avoid moving in a circular motion; Thus whirlings are formed in a fwift river, near a bridge, or near fome other dike, whereby the ftream is interrupted.

Objects feem to go round in that disease, because the fpirits that flow back from the organ, being moved with those of the brain, are carried away by the latter, according to their circular determination; and because they carry to the brain the impression of the object by their motion, and move round, the object must appear to move round also.

The

The fight is thought to be the only fenfe which receives the impreffion of that circular motion of the fpirits; but it may not be improperly faid, that the other fenfes are equally in fome measure affected with it: For thofe who are troubled with a vertigo have moft times a tingling in the ears, which is a motion like that of the turning round in the eyes. They have also a weakness in their legs, and would fall in turning round, if they were not fupported. Thus that im

rations. Thus it is we arrive at the know. ledge of any thing: We reflect with ourfelves upon its affections and properties, and, if we discover them to conftitute the nature of the thing, or belong to its effence, we then affert what we fee clearly and dif tinctly comprehended in its idea.

In the human mind, or rational foul, we perceive two operations; one by which the foul understands, and the other by which fhe wills. Thefe operations can neither proceed from the body, nor be in any refpect affections of matter: For, confidering matter, we find, that the first thing prefenting itself to us, or that we take notice of, is extenfion, which we make its first attribute, from whence all the other affections of matter muft neceffarily be derived; fuch as divifibility, mobility, figurability, impenetrability. Now, let matter be divided and fubdivided; let it be moved, let it be figured, let it receive all poffible modifications, it can never be brought to such a pass, as either to understand or to will: Such functions are intirely excluded from its idea, and must belong to a substance of a different nature, which can be nothing else than a spiritual substance, in whofe primary conception thought is included. Wherefore the human mind may be properly called a thinking or fpiritual fubitance, and of confequence it must be one and fimple; indivisible in itself, and in its operations, as affirmation and negation cannot be divided into parts. On the contrary, matter, ha ving extenfion in its primary conception, muft confift in a multiplicity of parts, which cannot square with the fimplicity of a thing that is fpiritual, much less be rendered capable of producing thought.

What can be imagined more abfurd, than that a minute portion of duft, or a fmall portion of matter, fhould be an intelligent being; and that it thould love not only things within the conception of the

3

fenfes, but alfo fpiritual things, removed as far as can be from a commerce with the fenfes? For we conceive not only material things, but understand also thofe which have no affinity with material things, as God, and his attributes, unity, eternity, infinity, immenfity, omnifeience, omnipotency; not to mention the laws of demonftration, the rules of equity and justice, and feveral other particulars. Who now would prefime to attribute to a minute portion of dua fuch a force and energy, as to measure the motions of the heavens; or to fix, by certain calculations, the changes and inequalities of days and nights, and the periods of times? All these things excite our admiration, and argue a more noble principle in us than rude and gross matter; whatever motion, whatever minuteness, whatever figure it may receive.

What fhall we fay of the acts of the will Muft they be attributed to a corporeal subftance? Can matter love faith, fincerity, justice, conftancy, and other virtues of the mind, as they are in reality loved by the will? It is evident it cannot be fo; and we may therefore conclude, that a thinking fubftance, and an extended substance, or the mind and the body, are intirely different in their kind; and that a corporeal fubftance cannot partake of thought, nor a fpiritual fubftance of extension.

Thus, as the human mind appears evidently to be a thinking fubftance, we may judge naturally, that it knows itself, and that it is confcious to itself of its own exiftence; for we cannot think, but we must manifeftly know, by attending a little to ourselves, that we do think, and that from thence, by an inward sense, we are privy to ourselves, that we exift; and, though the mind has not fo clear a knowledge of its own effence, as it has of the effence of material substances; yet it is more certain of its own exiftence, than of the existence of bodies; because it may have fome doubt concerning the existence of bodies, but by

no

no means of its own exiftence, when it thinks. Thought then must be the life of the human mind, and of all fpiritual fubtances; for it is an undoubted truth, that fpirits cannot live otherwife than by thought, and that they cannot perifh, but when they cease to think.

Now, when we confider whether the mind of man be immortal, or, rather, whether life always belongs to it, or whether it can live in a separate state from the body, we are certain, that, as it is a fubftance intirely diftinct from the body, it ftands not in need of the body to fubfift, and that it al ways lives; first, because it cannot tend to its own deftruction; fecondly, as it thinks, it cannot be conceived without life; there fore it must be immortal.

It is true, we have no metaphysical certainty of the fubfiftence of the mind, after its feparation from the body, though it be an incorruptible fubitance, which intrinfically in itself, and by itfelt, cannot be corrupted; yet extrinfically may ceafe to be, by the fubtraction of the influx of the cause from which it has received its being. The reafon is, because God, its caufe, exifting neceffarily, and all other beings, as beings by participation, having only a contingent existence; it is evident, that, if God with drew his influx for one moment only, there could be no longer an emanation from his being, and, of confequence, annihilation mult enfue. Juft fo, with regard to a dark place, inlightened by the fun, if any caufe has obftructed the paffages through which the rays of light enter, it must be reduced to darknefs. But as God, by an invioJable order, continually and conftantly preferves the things he extracted out of nothing, we may naturally conjecture, that the human mind cannot perish in a feparate ftate from the body, and that it is not of a worfe condition than a fubitance of an inferior rank to it; that is, a body, or portion or part of a body, which, by the continned concurrence of God, cannot be annihilated; yet with this difference, that, as a body in its nature is extended, and confits of many parts, fo, of confequence, it must go through a fucceffion of changes, and must be modified with different forms and configurations; whereas the mind, being in its nature one, fimple, and without any compofition of parts, must remain whole, intire, and incorrupt.

Several other reafons might be alledged, in confirmation of the never perishing state of the human mind; but one, as most fruitful in conclufions, fhould be particularly attended to; and this is the enlargement of the mind, or its tendency to

perfection, in proportion as its capacity; through the different stages of life, is actuated by the principles of reason.

Juftly speaking, the mind, being but one and fimple, cannot receive an enlargement; because a spiritual fubftance, having none of the dimenfions which are effential and conftitutive attributes of matter, cannot be made capable of the leaft commenfuration peculiar to a body. Now a body can be made bigger or less, according to the ampliation or diminution of its parts; but a mind cannot have that ampliation or diminution, being indivifible and having no parts. We must therefore conceive, that its enlargement depends on the multiplicity of its ideas, and that this idea of the enlargement of the mind belongs properly to man, when his body can aptly discharge all its organic functions, and his foul all her faculties; then it is that the union of the foul and body is intirely perfect, that the brain has its due confiftence, that the courfe of the fpirits is juft and regular, and that ideas are distinct and lively. The contrary happens when old age creeps upon us; the fubftance of the brain is languid and fluid; the traces begin to be defaced, and dwindle away; the fpirits are for the most part extinct; and, as the body is unapt to exert its organic functions, fo the foul, perceiving a kind of obftruction in the organs of the body fhe is united to, cannot exert her own faculties; becaufe, according to the laws of union established between the foul and body, there must be a reciprocal communication of thoughts and motions; that is, as often as thoughts happen in the mind, they muft neceffarily affect the nerves, and thereby excite a movement in the body; and as often as movements happen in the body, by the impulfe of external objects, they must first warn the fibres, the fibres must warn the nerves, and the nerves muft propagate the movement to the brain, to which the foul is principally united. Now, fhould there be a diffolution of any of the parts, or an obstruction in the organs of the body, the movement could not be propagated to the foul, nor the thoughts affect the body; and thus the union becomes imperfect.

Hence it will appear, that all things and all notions, whofe operations depend moftly on those of the mind, are enlarged and become more perfect, as the mind is enlarged and becomes more perfect. The mind cannot attain full perfection while cloathed with corruption and a mortal body; but, by its attention to its ideas, though one and fimple, it may be the fubject of increase; fo may all arts and fciences, when the mind

tends,