Chapter 3

Of the PLAGUE in general.

CHAP. I.

_Of the Origine and Nature of the Plague._

MY Design in this Discourse being to propose what Measures I think most proper to defend the Nation against the _Plague_, and for this End to consider the Nature of _Pestilential Contagion_ as far as is necessary to set forth the Reasonableness of the Precepts I shall lay down; before I proceed to any particular Directions, I shall enquire a little into the Causes, whence the _Plague_ arises, and by what Means the Infection of it is spread.

IN the most ancient Times _Plagues_, like many other Diseases, were looked upon as _divine Judgments_ sent to punish the Wickedness of Mankind: and therefore the only Defence sought after was by Sacrifices and Lustrations to appease the Anger of incensed Heaven.[15]

HOW much soever may be said to justify Reflexions of this Kind, since we are assured from sacred History, that divine Vengeance has been sometimes executed by _Plagues_; yet it is certain, that such Speculations pushed too far, were then attended with ill Consequences, by obstructing Inquiries into natural Causes, and encouraging a supine Submission to those Evils: against which the infinitely good and wise Author of Nature has in most Cases provided proper Remedies.

UPON this Account, in After-Ages, when the Profession of Physick came to be founded upon the Knowledge of Nature, _Hippocrates_ strenuously opposed this Opinion, that _some particular Sicknesses were Divine, or sent immediately from the Gods_; and affirmed, that _no Diseases came more from the Gods than others, all coming from them, and yet all owning their proper natural Causes: that the Sun, Cold, and Winds were_ divine; _the Changes of which, and their Influences on human Bodies, were diligently to be considered by a Physician_.[16]

WHICH general Position this great Author of Physick intended to be understood with respect to _Plagues_ as well as other Distempers: How far he had reason herein, will in some measure appear, when we come to search into the Causes of this Disease.

BUT in order to this Inquiry, it will be convenient, in the first place, to remove an erroneous Opinion some have entertained, that the _Plague_ differs not from a _common Fever_ in any thing besides its greater Violence. Whereas it is very evident, that since the _Small-Pox_ and _Measles_ are allowed to be Distempers distinct in _Specie_ from all others, on account of certain Symptoms peculiar to them; so, for the same reason, it ought to be granted, that the _Plague_ no less differs in Kind from ordinary Fevers: For there are a Set of distinguishing Symptoms as essential to the _Pestilence_, as the respective Eruptions are to the _Small-Pox_ or _Measles_; which are indeed (as I have mentioned in the Preface) each of them _Plagues_ of a particular kind.

AS the _Small-Pox_ discharges itself by _Pustules_ raised in the Skin; so in the _Plague_ the noxious Humour is thrown out either by _Tumors_ in the Glands, as by a _Parotis_, _Bubo_, and the like; or by _Carbuncles_ thrust out upon any part of the Body. And these Eruptions are so specific Marks of this Distemper, that one or other of them is never absent: unless through the extreme Malignity of the Disease, or Weakness of Nature, the Patient sinks, before there is time for any Discharge to be made this way; that Matter, which should otherwise have been cast out by external _Tumors_, seizing the _Viscera_, and producing _Mortifications_ in them.

SOMETIMES indeed it happens, by this means, that these _Tumors_ in the _Glands_, and _Carbuncles_, do not appear; just as a bad kind of the _Small-Pox_ in tender Constitutions sometimes proves fatal before the _Eruption_, by a _Diarrhoea_, _Hæmorrhage_, or some such Effect of a prevailing Malignity.

THE _French_ Physicians having distinguished the Sick at _Marseilles_ into five _Classes_, according to the Degrees of the Distemper, observed _Bubo's_, and _Carbuncles_, in all of them, except in those of the _first Class_, who were so terribly seized, that they died in a few Hours, or at farthest in a Day or two, sinking under the Oppression, Anxiety, and Faintness, into which they were thrown by the first Stroke of the Disease; having Mortifications immediately produced in some of the _Viscera_, as appeared upon the Dissection of their Bodies[17]. And this Observation of the _French_ Physicians, which agrees with what other Authors have remarked in former _Plagues_, fully proves, that these Eruptions are so far from being caused solely by the greater _Violence_ of this Disease, than of other Fevers, that they are only absent, when the Distemper is extraordinary fierce; but otherwise they constantly attend it, even when it has proved so mild, that the first Notice, the Patient has had of his Infection, has been the Appearance of such a _Tumor_: as, besides these _French_ Physicians, other Authors of the best Credit have assured us. From whence we must conclude, that these _Eruptions_ are no less a Specific Mark of this Disease, than those are, by which the _Small Pox_ and _Measles_ are known and distinguished. And as in the first _Class_ of those attacked with the Plague, so likewise in these two Distempers we often find the Patient to dye by the violence of the Fever, before any Eruption of the Pustules can be made.

THIS Circumstance of the Plague being mortal before any Eruptions appeared, was attended with a great misfortune. The Physicians and Surgeons appointed to examine the dead Bodies, finding none of the distinguishing Marks of the Disease, reported to the Magistrates that it was not the _Plague_; and persisted in their opinion, till one of them suffered for his Ignorance, and himself, with part of his Family, dyed by the Infection: this Assurance having prevented the necessary Precautions[18].

AND this in particular shews us the difference between the true _Plague_, and those _Fevers_ of extraordinary Malignity, which are the usual Forerunners of it, and are the natural Consequence of that ill State of Air, we shall hereafter prove to attend all _Plagues_. For since all those Fevers, from which People recover without any Discharge by Tumors in the Glands, or by _Carbuncles_, want the _characteristic_ Signs, which have been shewn to attend the slightest Cases of the true _Plague_; we cannot, upon any just Ground, certainly conclude them to be a less Degree only of that Distemper: but as far as appears, they are of a different Nature, are not ordinarily _Contagious_ like the _Plague_, nor yet have any such necessary relation to it, but that such Fevers do sometimes appear, without being followed by a real _Pestilence_.

ON the other hand, I would not be understood to call every _Fever_ a _Plague_, which is followed by Eruptions resembling these here mentioned: For as every _Boil_ or _Pustule_, which breaks out upon the Skin, is not an Indication of the _Small Pox_, nor every Swelling in the _Groin_ a _Venereal Bubo_; so there are _Carbuncles_ not Pestilential, and other Fevers, besides the _Plague_, which have their Crisis by _Tumors_ and _Abscesses_, and that sometimes even in the _Parotid_ or other Glands. There is indeed usually some difference between these Swellings in the _Plague_, and in other Fevers, especially in the time of their coming out: for in the _Plague_ they discover themselves sooner than in most other Cases. But the principal difference between these Diseases, is, that the Plague is infectious, the other not; at least not to any considerable Degree.

AND this leads me to another Character of this Disease, whereby it is distinguished from ordinary Fevers, which is the _Contagion_ accompanying it. This is a very ancient Observation. _Thucydides_ makes it a part of his Description of the _Plague_ at _Athens_[19]; and _Lucretius_, who has almost translated this Description of _Thucydides_, dwells much upon it[20]. _Aristotle_ makes it one of his[21] _Problems_, How the _Plague infects_ those who approach to the Sick. And what is of more Consequence, _Galen_ himself is very clear in it[22]; for he has these words: +hoti syndiatribein tois loimôttousin episphales, apolausai gar kindynos, hôsper psôras tinos+, _&c. that it is unsafe to be about those, who have the Plague, for fear of catching it, as in the Itch_, &c. Indeed this is a thing so evident, that we find it at present the current Opinion of all Mankind, a very few Persons only excepted, who have distinguished themselves by their Singularity in maintaining the opposite Sentiment. And it is something strange that any one should make a Question of a thing so obvious, which is proved sufficiently by one Property only of the Disease, that whenever it seizes one Person in a House, it immediately after attacks the greatest part of the Family. This Effect of the _Plague_ has been so remarkable at all times, that whoever considers it well, cannot possibly, I think, have any Doubt remaining, or require any stronger Argument to convince him, that the Disease is infectious. For this very reason the _Small-Pox_ and _Measles_ are generally allowed to be _contagious_; because it is observed, that when either of these Diseases is got among a Family, it usually seizes successively the greatest part of that Family, who have not had it before: at least if such in the Family hold free Communication with the Sick. And by the same Argument the _Plague_ must be concluded to be infectious likewise. It cannot be pretended, that this is occasioned in the _Plague_ from this only, that the sound Persons are render'd more than ordinarily obnoxious to the unhealthy Air, or whatever be the common Cause of the Disease, by being put into fear and dispirited, upon seeing others in the same House taken sick: For if this were the Case, _Children_, who are too young to have any Apprehensions upon this Account, would escape better than others, the contrary of which has been always experienced.

IT is true, some have not been attacked by the Disease, though constantly attending about the Sick. But this is no Objection against what is here advanced: for it is as easily understood how some Persons, by a particular Advantage of Constitution, should resist Infection, as how they should constantly breath a noxious Air without hurt. An odd Observation of _Diemerbroek_ deserves notice in this Place; That, part of a Family removed into a Town free from the _Plague_, was observed by him to be taken ill of it soon after the part left behind in the diseased Town fell sick: which certainly could scarce have happened, unless a Communication between the Healthy and the Sick, by Letters or otherwise, was capable of causing it[23]. Of the same Nature is a Circumstance recorded by _Evagrius_ of the _Plague_, which he describes, and what, he owns, surprized him very much: That, many of those, who left infected Places, were seized with the _Plague_ in the Towns to which they had retired, while the old Inhabitants of those Towns were free from the Disease[24]. But to multiply Proofs of a thing so evident, is needless; innumerable are at hand, and several will occasionally occur in the following Parts of this Discourse, when we come to speak in particular of the ways, by which this Infection is conveyed about. I shall therefore say no more in this Place, but only, that all the Appearances attending this Disease are very easily explained upon this Principle, and are hardly to be accounted for upon any other. We learn from hence the reason why when the _Plague_ makes its first Appearance in any Place, though the Number of Sick is exceeding small, yet the Disease usually operates upon them in the most violent manner, and is attended with its very worst Symptoms. Now was the Disease produced not by imported _Contagion_, but from some Cause, which had its Original in the diseased Place, and consequently from a Cause gradually bred, the contrary must happen: the Diseased would at first not only be few in Number, but their Sickness likewise more moderate than afterwards, when the morbific Causes were raised to their greatest Malignity. From the same Principle we see the reason, why People have often remained in Safety in a diseased Town, only by shutting themselves up from all Communication with such, as might be suspected of giving them the Disease. When the _Plague_ was last in _England_, while it was in the Town of _Cambridge_, the Colleges remained entirely free by using this Precaution. In the _Plague_ at _Rome_ in the Years 1656 and 1657, the _Monasteries_ and _Nunneries_, for the most part, defended themselves by the same Means[25]: Whereas at _Naples_, where the _Plague_ was a little before, these _Religious Houses_, from their Neglect herein, did not escape so well[26]. Nay the Infection entered none of the _Prisons_ at _Rome_[27], though the Nastiness of those Places exposes them very much. But, to avoid Prolixity, I shall give only one Instance more. I think it cannot be explained in any other reasonable manner, how the last _Plague_ in the City of _London_, which broke out in the parish of St. _Giles's in the Fields_ towards the latter end of the Year 1664, should lie a-sleep from _Christmas_ to the middle of _February_, and then break out again in the same Parish; and after another long rest till _April_, shew itself again in the same Place[28].

TO proceed: Whoever examines the Histories of _Plagues_ in all times, which have been described with any Exactness, will find very few, that do not agree in these essential Marks, whereby the _Plague_ may be distinguished from other _Fevers_. I confess an Instance or two may be found to the contrary; perhaps the History of our own Country furnishes the most remarkable of any[29]. But Examples of this kind are so very rare, that I think it must be concluded, that the _Plague_ is usually one and the same Distemper.

IN the next place I shall endeavour to shew, that the _Plague_ has always the same Original, and is brought from _Africa_, the Country which has entail'd upon us two other infectious Distempers, the _Small-Pox_ and _Measles_. In all Countries indeed _Epidemic Diseases_ extraordinarily mortal, are frequently bred in _Goals_, _Sieges_, _Camps_, &c. which Authors have often in a large Sense called _Pestilential_: But the true _Plague_, which is attended with the distinguishing Symptoms before described, and which spreads from Country to Country, I take to be an _African_ Fever bred in _Æthiopia_ or _Egypt_, and the _Infection_ of it carried by Trade into the other Parts of the World.

IT is the Observation of _Pliny_, that the _Pestilence_ always travels from the _Southern_ Parts of the World to the _Western_, that is, in his Phrase, into _Europe_[30]. And the most accurate Accounts in all Times of this Disease, wherever it has raged, bring it from _Africa_. _Thucydides_[31], in his admirable Description of the famous _Plague_ of _Athens_, says, that it began in Upper _Æthiopia_, then came into _Egypt_, from whence it was spread first into _Persia_, and afterwards into _Greece_.

THERE is in all ancient History no Account of any _Plague_ so dreadful as that, which broke out at _Constantinople_ in the time of the Emperor _Justinian A. D._ 543. This is said to have spread its Infection over all the Earth, and to have lasted fifty two Years. The History of it is very well told by _Evagrius_[32], and yet more learnedly by _Procopius_[33]: and they both observe, that the Distemper had its Birth in _Æthiopia_ or _Egypt_.

THIS is likewise agreeable to the modern Relations of Travellers and Merchants from _Turkey_, who generally inform us, that the frequent _Plagues_, which depopulate that Country, are brought thither from the Coast of _Africa_: insomuch that at _Smyrna_, and other Ports of that Coast, they often know the very Ship which brings it. And, in these latter Ages, since our Trade with _Turkey_ has been pretty constant, the _Plagues_ in these Parts of _Europe_ have evidently been brought from thence.

THE late _Plague_ in _France_ came indisputably from _Turkey_, as I shall particularly shew in some of the following Pages. The _Plague_, which broke out at _Dantzick_ in the Year 1709, and spread from thence to _Hamburgh_, _Copenhagen_, and other Cities in the _North_, made its way thither from _Constantinople_ through _Poland_, &c. And the last _Plague_ in this City, if we may believe Dr. _Hodges_, had the same Original, being brought to us from _Holland_, but carried to them by _Cotton_ imported from _Turkey_[34].

THE greatest _Mortality_ that has happen'd in later Ages, was about the middle of the fourteenth Century; when the _Plague_ seized Country after Country for five Years together[35]. In the Year 1346 it raged in _Egypt_, _Turkey_, _Greece_, _Syria_, and the _East-Indies_; in 1347 some Ships from the _Levant_ carried it to _Sicily_, _Pisa_, _Genoa_, &c. in 1348 it got into _Savoy_, _Provence_, _Dauphiny_, _Catalonia_, and _Castile_, &c. in 1349 it seized _England_, _Scotland_, _Ireland_, and _Flanders_; and the next Year _Germany_, _Hungary_ and _Denmark_: and in all Places, where it came, it made such heavy Destruction, that it is said to have dispeopled the Earth of more than half its Inhabitants[36]. Now since _Africa_ had a share of this _Plague_ in the very beginning, I question not but it had its first Rise in that Country; and not in _China_, as _M. Villani_, in his History of those Times, relates from the Report of _Genoese_ Seamen, who came from those Parts, and said it was occasion'd there by a great _Ball of Fire_, which either burst out of the Earth, or fell down from Heaven[37]. But this Relation is so very incredible, that I cannot think we ought at all to rely upon it: seeing we have no Instance of a _Plague_, which was originally bred in that Country.

IT is very remarkable, that the several Countries of _Europe_ have always suffered more or less in this way, according as they have had a greater or lesser Commerce with _Africa_; or with those Parts of the _East_, that have traded thither. Which Observation, by the by, may help to solve a Difficulty concerning the great Increase of People among the _Northern_ Nations in ancient Times, more than at present; for in those Ages, having no Communication at all with _Africa_, they were not wasted with _Plagues_, as they have been since.

AS the People of _Marseilles_, from the first Foundation of their City by the _Phoceans_, were famous for Trade, and made long Voyages Southwards on the _African_ Coast[38]; so they have in all times been very liable to the Plague. A French Author[39] in a History of the late Plague at _Marseilles_ reckons up twenty Plagues that have happened in that City; notwithstanding it is by its situation one of the most healthy and pleasant Places in _France_, and the least subject to epidemic Distempers. But if we had no Records of this in History, an odd Custom among them, mentioned in Antiquity[40], of the way they made use of to clear themselves from this Distemper, would be a proof of it. Their manner at such times was, that some one poor Man offered himself to be maintained at the publick Expence with delicate Food for a whole Year: at the end of which he was led about the City dressed in consecrated Garments and Herbs; and being loaded with Curses as he went along, that the Evils of the Citizens might fall upon him, he was at last thrown into the Sea[41].

AGREEABLE to this Remark upon Trade is the Observation of _Procopius_ in his forecited History, that the _Plague_ was always found to spread from _Maritime_ Places into the _Inland_ Countries: which has ever since been confirmed by Experience.

HAVING shewn this Disease to be a Distemper of a distinct Species, and to take its Rise only in _Africa_; we must next seek for its Cause in that Country and no where else. We ought therefore to consider, what there is peculiar to that Country, which can reasonably be supposed capable of producing it. Wherefore I shall briefly set down as much as serves for this purpose of the State of _Grand Cairo_ in _Egypt_, and of _Æthiopia_, the two great Seminaries of the _Plague_: Travellers relating that these Countries are more infested with it than most other Parts of _Africa_.

_GRAND CAIRO_ is crouded with vast Numbers of Inhabitants, who for the most part live very poorly, and nastily; the Streets are very narrow, and close: it is situate in a sandy Plain at the Foot of a Mountain, which by keeping off the Winds, that would refresh the Air, makes the _Heats_ very stifling. Through the midst of it passes a great _Canal_, which is filled with Water at the overflowing of the _Nile_; and after the River is decreased, is gradually dried up: Into this the People throw all manner of Filth, Carrion, _&c._ so that the Stench which arises from this, and the Mud together, is insufferably offensive[42]. In this Posture of things, the _Plague_ every Year constantly preys upon the Inhabitants; and is only stopt, when the _Nile_, by overflowing, washes away this Load of Filth; the _Cold Winds_, which set in at the same time, lending their Assistance, by purifying the Air.

IN _Æthiopia_ those prodigious Swarms of _Locusts_, which at some times cause a Famine, by devouring the Fruits of the Earth, unless they happen to be carried by the Winds clear off into the Sea, are observed to entail a new Mischief upon the Country, when they die and rot, by raising a _Pestilence_[43]; the Putrefaction being hightened by the excessive _Intemperance of the Climate_, which is so very great in this Country, that it is infested with violent _Rains_ at one Season of the Year, for three or four Months together[44]. And it is particularly observed of this Country, that the _Plague_ usually invades it, whenever Rains fall during the sultry Heats of _July_ and _August_[45], that is, as _Lucretius_ expresses it, when the Earth is

_Intempestivis pluviisque et solibus icta_[46].

NOW if we compare this last Remark of the _Intemperance of the Climate_ in _Æthiopia_, with what the _Arabian_ Physicians[47], who lived near these Countries, declare, that _Pestilences_ are brought by _unseasonable_ Moistures, Heats, and want of Winds; I believe we shall be fully instructed in the usual Cause of this Disease. Which from all these Observations compared together, I conclude to arise from the _Putrefaction_ so constantly generated in these Countries, when _that_ is hightened and increased by the ill State of Air now described; and especially from the _Putrefaction_ of animal Substances.

IT is very plain, that animal Bodies are capable of being altered into a Matter fit to breed this Disease: because this is the Case of every one who is sick of it, the Humours in him being corrupted into a Substance which will _infect_ others. And it is not improbable, that the volatile Parts with which Animals abound, may in some ill States of Air in the sultry Heats of _Africa_ be converted by Putrefaction into a Substance of the same kind: since in these colder Regions, we sometimes find them to contract a greater Degree of Acrimony than most other Substances will do by _putrefying_, and also more dangerous for Men to come within the reach of their Action; as in those pernicious, and even poysonous Juices, which are sometimes generated in corrupted Carcasses: Of which I have formerly given one very remarkable Instance[48], and, if it were necessary, many more might be produced, especially in _hydropic Bodies_, and in _cancerous Tumors_. Nay more, we find _animal Putrefaction_ sometimes to produce in these _Northern_ Climates very fatal Distempers, though they do not arise to the Malignity of the true _Plague_: For such _Fevers_ are often bred, where a large Number of People are closely confined together; as in _Goals_, _Sieges_, and _Camps_.

AND perhaps it may not be here amiss to remark, that the _Egyptians_ of old were so sensible how much the _Putridness_ of dead Animals contributed towards breeding the _Plague_, that they worshipped the Bird _Ibis_ for the Service it did in devouring great Numbers of Serpents; which they observed did hurt by their Stench when dead, as well as by their Bite when alive[49].

BUT no kind of _Putrefaction_ is ever hightened in these _European_ Countries to a degree capable of producing the true _Plague_: and we learn from the Observation of the _Arabian_ Physicians, that some Indisposition of the _Air_ is necessary in the hottest Climates, either to cause so exalted a Corruption of the forementioned Substances, or at least to enforce upon Mens Bodies the Action of the _Effluvia_ exhaled from those Substances, while they putrefy. Both which Effects may well be expected from the sensible ill Qualities of the _Air_ before described, whenever they continue and exert their Force together any considerable time.

WHAT I have here advanced of the first Original of the _Plague_, appears to me so reasonable, that I cannot enough wonder at Authors for quitting the Consideration of such manifest Causes for _Hidden Qualities_; such as _Malignant Influences of the Heavens_; _Arsenical_, _Bituminous_, or other _Mineral Effluvia_, with the like imaginary or uncertain Agents.

THIS however I do not say with design absolutely to exclude all Disorders in the _Air_, that are more latent than the intemperate _Heat_ and _Moisture_ before mentioned, from a Share in increasing and promoting the Infection of the _Plague_, where it is once bred: for I rather think this must sometimes be the Case; like to what is observed among us in relation to another infectious Distemper, namely, the _Small-Pox_, which is most commonly spread, and propagated by the same manifest Qualities of the _Air_ as those here described: Notwithstanding which, this Distemper is sometimes known to rage with great Violence in the very opposite Constitution of _Air_, _viz._ in the Winter during dry and frosty Weather. But to breed a Distemper, and to give force to it when bred, are two different things. And though we should allow any such secret Change in the _Air_ to assist in the first Production of the Disease; yet it may justly be censured in these Writers, that they should undertake to determine the _Specific Nature_ of these secret Changes and Alterations, which we have no means at all of discovering: Since they do not shew themselves in any such sensible manner, as to come directly under our Examination; nor yet do their Effects, in producing the _Plague_, point out any thing of their _Specific Nature_.

ALL that we know, is this, that the Cause of the _Plague_, whatever it be, is of such a Nature, that when taken into the Body, it works such Changes in the Blood and Juices, as to produce this Disease, by suddenly giving some Parts of the Humours such corrosive Qualities, that they either excite inward _Inflammations_ and _Gangrenes_, or push out _Carbuncles_ and _Bubo's_; the _Matter_ of which, when suppurated, communicates the like Disease to others: But of the manner how this is done, I shall discourse in the following Chapter.

CHAP. II.

_Of the Causes which spread the Plague._

I HAVE been thus particular in tracing the _Plague_ up to its first Origine, in order to remove, as much as possible, all Objection against what I shall say of the Causes, which excite and propagate it among us. This is done by _Contagion_. Those who are Strangers to the full Power of _this_, that is, those who do not understand how subtile it is, and how widely the Distemper may be spread by _Infection_, ascribe the Rise of it wholly to the malignant Quality of the _Air_ in all Places, wherever it happens; and, on the other hand, some have thought that the Consideration of the infectious Nature of the Disease must exclude all regard to the Influence of the _Air_: Whereas the _Contagion_ accompanying the Disease, and the Disposition of the _Air_ to promote that _Contagion_, ought equally to be considered; both being necessary to give the Distemper full force. The Design therefore of this Chapter, is to make a proper Balance between these two, and to set just Limits to the Effects of each.

FOR this purpose, I shall reduce the Causes, which spread the _Plague_, to three, _Diseased Persons_, _Goods transported from infected Places_, and _a corrupted State of Air_.

THERE are several Diseases, which will be communicated from the Sick to others: and this not done after the same manner in all. The _Hydrophobia_ is communicated no other way than by mixing the morbid Juices of the diseased Animal immediately with the Blood of the sound, by a _Bite_, or what is analogous thereto; the _Itch_ is given by _simple Contact_; the _Lues Venerea_ not without _a closer Contact_; but the _Measles_, _Small-Pox_, and _Plague_ are caught by a _near Approach_ only to the Sick: for in these three last Diseases Persons are render'd obnoxious to them only by residing in the same House, and conversing with the Sick.

NOW it appears by the Experiments mentioned in the _Preface_, of giving the _Plague_ to _Dogs_ by putting the _Bile_, _Blood_ or _Urine_ from infected Persons, into their Veins, that the whole mass of the animal Fluids in this Disease is highly corrupted and putrefied. It is therefore easy to conceive how the _Effluvia_ or Fumes from Liquors so affected may taint the ambient Air. And this will more especially happen, when the Humours are in the greatest Fermentation, that is, at the Highth of the Fever: as it is observed that fermenting Liquors do at the latter end of their intestine Motion throw off a great Quantity of their most subtile and active Particles. And this Discharge will be chiefly made upon those Glands of the Body, in which the Secretions are the most copious, and the most easily increased: such are those of the Mouth and Skin. From these therefore the Air will be impregnated with _pestiferous Atoms_: which being taken into the Body of a sound Person will, in the Nature of a _Ferment_, put the Fluids there into the like Agitation and Disorder.

THE Body, I suppose, receives them these two ways, by the _Breath_, and by the _Skin_; but chiefly by the former.

I THINK it certain that _Respiration_ does always communicate to the Blood some Parts from the Air: Which is proved from this Observation, that the same Quantity of Air will not suffice long for breathing, though it be deprived of none of those Qualities, by which it is fitted to inflate the Lungs and agitate the Blood, the Uses commonly ascribed to it. And this is farther confirm'd by what the learned Dr. _Halley_ has inform'd me, that when he was several Fathom under Water in his _Diving Engine_, and breathing an Air much more condensed than the natural, he observed himself to breath more slowly than usual: Which makes it more than probable, that this conveying to the Blood some subtile Parts from the Air, is the chief Use of _Respiration_; since when a greater Quantity of _Air_ than usual was taken in at a time, and consequently more of these subtile Parts received at once by the Blood, a less frequent _Respiration_ sufficed.

AS to the _Skin_, since there is a continual Discharge made thro' its innumerable _Pores_, of the matter of _insensible Perspiration_ and _Sweat_; it is very possible that the same Passages may admit subtile Corpuscles, which may penetrate into the inward Parts. Nay it is very plain that they do so, from what we observe upon the outward Application of _Ointments_ and warm _Bathings_: which have their Effects by their finest and most active Parts insinuating themselves into the Blood.

IT is commonly thought, that the _Blood_ only is affected in these Cases by the morbific _Effluvia_. But I am of opinion, that there is another Fluid in the Body, which is, especially in the beginning, equally, if not more, concerned in this Affair: I mean the _Liquid of the Nerves_, usually called the _Animal Spirits_. As _this_ is the immediate Instrument of all Motion and Sensation, and has a great Agency in all the glandular Secretions, and in the Circulation of the Blood itself; any considerable Alteration made in it must be attended with dangerous Consequences. It is not possible that the whole Mass of Blood should be corrupted in so short a Time as that, in which the fatal Symptoms, in some Cases, discover themselves. Those Patients of the _first Class_, mentioned in the beginning of this Discourse, particularly the _Porters_ who opened the infected Bales of Goods in the _Lazaretto_'s of _Marseilles_, died upon the first Appearance of Infection, as it were by a sudden Stroke; being seized with Rigors, Tremblings, Heart-Sickness, Vomitings, Giddiness and Heaviness of the Head, an universal Languor and Inquietude; the Pulse low and unequal: and Death insued sometimes in a few Hours.

EFFECTS so sudden must be owing to the Action of some Corpuscles of great Force insinuated into, and changing the Properties of, another subtle and active Fluid in the Body: and such an one, no doubt, is the _Nervous Liquor_.

IT is not to be expected that we should be able to explain the particular manner by which this is brought about. We know too little of the Frame of the Universe, and of the Laws of _Attractions_, _Repulsions_ and _Cohesions_ among the minutest Parcels of Matter, to be able to determine all the Ways by which they affect one another, especially within animal Bodies, the most delicate and complicated of all the known Works of Nature. But we may perhaps make a probable Conjecture upon the Matter. Our great Philosopher, whose surprising Discoveries have exceeded the utmost Expectations of the most penetrating Minds, has demonstrated that there is diffused through the Universe a _subtile_ and _elastic Fluid_ of great Force and Activity. This he supposes to be the Cause of the _Refraction_ and _Reflection_ of the Rays of Light; and that by its _Vibrations_ Light communicates Heat to Bodies: and, moreover, that this readily pervading all Bodies, produces many of their Effects upon one another[50].

NOW it is not improbable that the _Animal Spirits_ are a thin Liquor, separated in the Brain, and from thence derived into the Nerves, of such a Nature that it admits, and has incorporated with it, a great Quantity of this _elastic Fluid_: which makes it a vital Substance of great Energy. And a Liquor of this kind must be very susceptible of Alterations from other active Bodies of a different Nature from it, if they approach to and are mixed with it: as we see some _Chemical Spirits_ upon their being put together, fall into a Fermentation, and make a Composition of a quite different kind.

IF therefore we allow the _Effluvia_ or _Exhalations_ from a corrupted Mass of Humours in a Body that has the _Plague_ to be volatile and firey Particles, carrying with them the Qualities, of those fermenting Juices from which they proceed; it will not be hard to conceive how these may, when received into the _nervous Fluid_ of a sound Person, excite in it such intestine Motions as may make it to partake of their own Properties, and become more unfit for the Purposes of the animal Oeconomy. But of this more in another Place.

THIS is one means by which the _Plague_, when once bred, is spread and increased: but the second of the forementioned Causes, namely, _Goods from infected Places_, extends the Mischief much wider. By the preceding Cause, the _Plague_ may be spread from _Person_ to _Person_, from _House_ to _House_, or perhaps from _Town_ to _Town_, tho' not to any great Distance; but this carries it into the remotest Regions. From hence the trading Parts of _Europe_ have their principal Apprehensions, and universally have recourse to _Quarantaines_ for their Security. The Universality of which Practice is a strong Argument, that _Merchandize_ will communicate _Infection_: for one cannot imagine, that so many Countries should agree in such a Custom without the most weighty Reasons. But besides, there is not wanting express Proof of this, from particular Examples, where this Injury has been done by several sorts of Goods carried from infected Places to others. Some of these I shall hereafter be obliged to mention; at present I shall confine my self to three Instances only. The _first_ shall be of the Entrance of the _Plague_ into _Rome_ in the Year 1656, which we are assured was conveyed thither from _Naples_ by Clothes and other Wares from that Place, brought first to Port _Neptuno_, and carried from thence to the Neighbouring Castle of St. _Lawrence_: which after having been kept some time there, were conveyed into _Rome_[51]. The _second_ Instance I shall take is from the Account given us of the Entrance of the Plague into _Marseilles_[52]; which being drawn up with great Exactness, may be the more rely'd on. It appears indisputably by this Account, that the Mischief was brought thither by Goods from the _Levant_. For the first, who had the Distemper, was one of the _Crew_ of the _Ship_, which brought those _Goods_: the next were those, who attended upon the same _Goods_, while they were under _Quarantaine_; and soon after the _Surgeon_, whom the Magistrates of _Marseilles_ appointed to examine the Bodies of those, who died.

THIS Relation, if duly consider'd, is, I believe, sufficient to remove all the Doubts any one can have about the Power of _Merchandize_ to convey _Infection_: for it affords all the Evidence, the most scrupulous can reasonably desire. Possibly there might be some Fever of extraordinary Malignity in _Marseilles_, such as is commonly called _Pestilential_, before the Arrival of these Goods: But no such Fever has any indisputable Right to the Title of _Pestilence_, as I have before shewn. On the contrary, these two, the real _Pestilence_, and such _Pestilential Fevers_, must carefully be distinguished, if we design to avoid all Mistakes in reasoning upon these Subjects.

SOME such Fever of uncommon Malignity, I say, might perhaps be in _Marseilles_ before the Arrival of these Goods. There might likewise perhaps be an Instance or two of _Fevers_ attended with _Eruptions_, bearing some Resemblance to those of the _Plague_: for such I my self have sometimes seen here in _London_. But it is not conceivable, that there should be any Appearance of the true _Plague_ before that time: for it was full six Weeks from the time of the Sailor's Death, which had given the Alarm, and raised a general Attention, before the Magistrates received Information of any one's dying of the _Plague_ in the City. And I believe it was never known, that the _Plague_, being once broke out, gave so long a Truce in hot Weather.

THE _Plague_, which has this present Year almost depopulated _Messina_, affords a _third_ Instance of the same kind. By an authentic Relation of it, published here[53] we are informed, that a _Genoese_ Vessel from the _Levant_, arrived at that City; and upon notice given that a Sailor, who had touched some Cases of _Cotton Stuffs_ bought up at _Patrasso_ in the _Morea_, where the Distemper then raged, was dead of the Plague, in the Voyage; the Ship was put under _Quarantaine_: during which time the _Cotton Stuffs_ were privately landed. The Master and some Sailors dying three days after, the Vessel was burnt. These Goods lay for some time concealed, but were soon after publickly sold: upon which the Disease immediately broke out in that _Quarter_ where they were opened; and afterwards was spread through the whole City.

I think it not improper, for the fuller Confirmation of the present Point, to give a Relation communicated to me by a Person of unquestionable Credit, of the like Effect from Goods, in respect to the _Small-Pox_; which Distemper is frequently carried in the Nature of the _Plague_ both to the _East_ and _West-Indies_ from these Countries, and was once carried from the _East-Indies_ to the _Cape of Good Hope_, in the following manner. About the Year 1718, a ship from the _East-Indies_ arrived at that Place: In the Voyage three Children had been sick of the _Small-Pox_: The foul Linen used about them was put into a Trunk, and lock'd up. At the Ship's Landing, this was taken out, and given to some of the Natives to be washed: Upon handling the Linen, they were immediately seized with the _Small-Pox_, which spread into the Country for many Miles, and made such a Desolation, that it was almost dispeopled.

IT has been thought so difficult to explain the manner how _Goods_ retain the Seeds of _Contagion_, that some[54] Authors have imagined _Infection_ to be performed by the Means of _Insects_; the _Eggs_ of which may be conveyed from Place to Place, and make the Disease when they come to be _hatched_. But as this is a Supposition grounded upon no manner of Observation, so I think there is no need to have recourse to it. If, as we have conjectured, the _Matter_ of _Contagion_ be an active Substance generated chiefly from animal Corruption; it is not hard to conceive how this may be lodged and preserved in soft porous Bodies, which are kept pressed close together.

WE all know how long a time _Perfumes_ hold their Scent, if wrapt up in proper Coverings: And it is very remarkable, that the strongest of these, like the Matter we are treating of, are mostly _animal Juices_, as _Mosch_, _Civet_, &c. and that the Substances, found most fit to keep them in, are the very same with those, which are most apt to receive and communicate Infection, as _Furrs_, _Feathers_, _Silk_, _Hair_, _Wool_, _Cotton_, _Flax_, &c. the greatest part of which are likewise of the _animal_ kind.

NOTHING indeed can give us so just a Notion of _Infection_, and more clearly represent the manner of it, than _Odoriferous_ Bodies. Some of _these_ do strangely revive the animal Spirits; others instantaneously depress and sink them: We may therefore conceive that, what active particles emitted from any such Substances do, is in the like way done by _Pestiferous_ Bodies; so that _Contagion_ is no more than the effect of volatile offensive Matter drawn into the Body by our _Smelling_.

THE third Cause we assigned for the spreading of _Contagion_, was a corrupted State of _Air_. Although the _Air_ be in a right State, yet a sick Person may infect those who are very near him: As we find the _Pestilence_ to continue sometimes among the _Crew_ of a Ship, after they have sailed out of the Infectious Air wherein the Disease was first caught. A remarkable Accident of this Nature is recorded to have happened in the _Plague_ at _Genoa_ in the Year 1656. Eleven Persons put to Sea in a _Felucca_, with design to withdraw themselves from the _Contagion_, and retire into _Provence_; but one of them falling sick of the _Plague_ soon after they had imbarked, infected the rest; insomuch that others being taken ill, and dying in their turns, they were not admitted any where, but were forced to return from whence they came: and by that time the Boat arrived again at _Genoa_ no more than one of them survived[55].

HOWEVER in this Case the Malady does not usually spread far, the _contagious_ Particles being soon dispersed and lost. But when in a corrupt Disposition of the _Air_ the _contagious_ Particles meet with the subtile Parts generated by that Corruption, by uniting with them they become much more active and powerful, and likewise of a more durable Nature; so as to form an infectious Matter capable of conveying the Mischief to a greater distance from the diseased Body, out of which it was produced.

IN general, a _hot Air_ is more disposed to spread _Contagion_ than a cold one, as no one can doubt, who considers how much all kinds of _Effluvia_ are farther diffused in a _warm Air_, than in the contrary. But moreover, that State of _Air_, when unseasonable Moisture and want of Winds are added to its Heat, which gives birth to the _Plague_ in some Countries, will doubtless promote it in all. For _Hippocrates_ sets down the same Description of a _Pestilential State_ of Air in his Country, as the _Arabians_ do of the Constitution, which gives Rise to the _Plague_ in _Africa_[56]. _Mercurialis_ assures us the same Constitution of _Air_ attended the _Pestilence_ in his time at _Padua_[57]: and _Gassendus_ observed the same in the _Plague_ of _Digne_[58]. Besides, it is easy to shew how the _Air_, by the sensible ill Qualities discoursed of in the last Chapter, should favour infectious Diseases, by rendering the Body obnoxious to them.

INDEED other hurtful Qualities of the _Air_ are more to be regarded than its Heat alone: for the _Plague_ is sometimes stopt, while the Heat of the Season increases, upon the Emendation of the _Air_ in other respects. At _Smyrna_ the _Plague_, which is yearly carried thither by Ships, constantly ceases about the 24th of _June_, by the dry and clear Weather they always have at that time: the unwholsome Damps being then dissipated that annoy the Country in the _Spring_. However, the Heat of the Air is of so much Consequence, that if any Ship brings it in the Winter Months of _November_, _December_, _January_, or _February_, it never spreads: but if later in the Year, as in _April_ or afterwards, it continues till the time before mentioned.

BUT moreover, what was said before of some latent Disorders in the _Air_ having a share in spreading the _Plague_, will likewise have place in these Countries; as the last _Plague_ in the City of _London_ remarkably proves, the Seeds of which, upon its first Entrance, and while it was confined to a House or two, preserved themselves through a hard frosty _Winter_, and again put forth their malignant Quality as soon as the Warmth of the _Spring_ gave them force: but, at the latter end of the next Winter they were suppressed so as to appear no more, though in the Month of _December_ more than half the _Parishes_ of the City were infected.

A _corrupted State_ of Air is, without doubt, necessary to give these contagious Atoms their full force; for otherwise it were not easy to conceive how the _Plague_, when once it had seized any Place, should ever cease but with the Destruction of all the Inhabitants: Which is readily accounted for by supposing an Emendation of the Qualities of the _Air_, and the restoring of it to a healthful State capable of dissipating and suppressing the Malignity.

ON the other hand, it does not appear, that the _Air_, however corrupted, is usually capable of carrying Infection to a very great distance; but that commonly the _Plague_ is spread from Town to Town by infected Persons and Goods: for there are numberless Instances, where the _Plague_ has caused a great Mortality in Towns, while other Towns and Villages, very near them, have been entirely free. And hence it is, that the _Plague_ sometimes spreads from Place to Place very irregularly. _Thuanus_[59] speaks of a _Plague_ in _Italy_, which one Year was at _Trent_ and _Verona_, the next got into _Venice_ and _Padua_, leaving _Vicenza_, an intermediate Place, untouched, though the next Year that also felt the same Stroke: a certain Proof that the _Plague_ was not carried by the _Air_ from _Verona_ to _Padua_ and _Venice_; for the infected _Air_ must have tainted all in its Passage. We have had lately in _France_ one Instance of the same Nature, when the _Plague_ was carried at once out of _Provence_ several Leagues into the _Gevaudan_. Usually indeed the _Plague_, especially when more violent than ordinary, spreads from infected Places into those which border upon them: which probably is sometimes effected by some little Communication infected Towns are obliged to hold with the Country about them for the sake of Necessaries, the Subtlety of the Venom now and then eluding the greatest Precautions; and at other times by such as withdraw themselves from infected Places into the Neighbourhood.

I OWN it cannot be demonstrated, that when the _Plague_ makes great Ravage in any Town, the Number of Sick shall never be great enough to load the _Air_ with infectious _Effluvia_, emitted from them in such Plenty, that they may be conveyed by the Winds into a neighbouring Town or Village without being dispersed so much as to hinder their producing any ill Effects; especially since it is not unusual for the _Air_ to be so far charged with these noxious _Atoms_, as to leave no Place within the infected Town secure: insomuch that when the Distemper is at its Highth, all shall be indifferently infected, as well those who keep from the Sick, as those who are near them; though at the beginning of a _Plague_ to avoid all Communication with the Diseased, is an effectual Defence. However, I do not think this is often the Case: just as the _Smoak_, with which the _Air_ of the City of _London_ is constantly impregnated, especially in _Winter_, is not carried many Miles distant; though the Quantity of it is vastly greater than the Quantity of infectious _Effluvia_, that the most mortal _Plague_ could generate.

BUT, to conclude what relates to the _Air_, since the ill Qualities of it in these _Northern_ Countries are not alone sufficient to excite the _Plague_, without imported _Contagion_, this shews the Error of a common Opinion, countenanc'd by Authors of great Name[60], that we are necessarily _visited_ with the _Plague_ once in thirty or forty Years: which is a mere Fancy, without Foundation either in Reason or Experience; and therefore People ought to be delivered from such vain Fears. Since the _Pestilence_ is never originally bred with us, but always brought accidentally from abroad, its coming can have no relation to any certain Period of Time. And although our three or four last _Plagues_ have fallen out nearly at such Intervals, yet that is much too short a Compass of Years to be a Foundation for a general Rule. Accordingly we see that almost fourscore Years have passed over without any Calamity of this kind.

THE _Air_ of our Climate is so far from being ever the Original of the true _Plague_, that most probably it never produces those milder infectious Distempers, the _Small-Pox_ and _Measles_. For these Diseases were not heard of in _Europe_ before the _Moors_ had entered _Spain_: and (as I have observed in the _Preface_) they were afterwards propagated and spread through all Nations, chiefly by means of the Wars with the _Saracens_.

MOREOVER, we are so far from any Necessity of these periodical Returns of the _Plague_, that, on the contrary, though we have had several Strokes of this kind, yet there are Instances of bad _Contagions_ from abroad being brought over to us, which have proved less malignant here, when our _Northern Air_ has not been disposed to receive such Impressions.

THE _Sweating Sickness_, before hinted at, called _Sudor Anglicus_ and _Febris Ephemera Britannica_, because it was commonly thought to have taken its Rise here, was most probably of a foreign Original: and though not the common _Plague_ with _Glandular Tumors_, and _Carbuncles_, yet a real _Pestilence_ from the same Cause, only altered in its Appearance, and abated in its Violence, by the salutary Influence of our Climate. For it preserved an Agreement with the common _Plague_ in many of its _Symptoms_, as _excessive Faintness_ and _Inquietudes_, _inward Burnings_, &c. these _Symptoms_ being no where observed in so intense a Degree as here they are described to have been, except in the true _Plague_: And, what is much more, it was likewise a _contagious_ Disease.

THE first time this was felt here, which was in the Year 1485, it began in the Army, with which King _Henry_ VII. came from _France_ and landed in _Wales_[61]: and it has been supposed by some to have been brought from the famous Siege of _Rhodes_ by the _Turks_ three or four Years before, as may be collected from what Dr. _Keyes_ says in one Place of his Treatise on this Disease[62]. Besides, of the several returns which this has made since that time, _viz._ in the Years 1506, 1517, 1528, and 1551, that in the Year 1528 may very justly be suspected to have been owing to the common _Pestilence_, which at those times raged in _Italy_[63] as I find one of our Historians has long ago conjectured[64]: and the others were very probably from a _Turkish_ Infection. If at least some of these Returns were not owing to the Remains of former Attacks, a suitable Constitution of Air returning to put the latent Seeds in Action before they were quite destroyed. It is the more probable that this Disease was owing to _imported Contagion_; because we are assured, that this Form of the Sickness was not peculiar to our Island, but that it made great Destruction with the same Symptoms in _Germany_, and other Countries[65].

I call this Distemper a _Plague_ with lessened Force: because though its carrying off thousands for want of right Management was a Proof of its Malignity, which indeed in one respect exceeded that of the common _Plague_ itself (for few, who were destroyed with it, survived the Seizure above one Natural Day) yet its going off safely with _profuse Sweats_ in twenty four Hours, when due care was taken to promote that Evacuation, shewed it to be what a learned and wise Historian calls it, _rather a Surprize to Nature, than obstinate_ to _Remedies_; who assigns this Reason for expressing himself thus, that _if the Patient was kept warm with temperate Cordials, he commonly recovered_[66]. And, what I think yet more remarkable, _Sweating_, which was the natural _Crisis_ of this Distemper, has been found by great Physicians the best Remedy against the common _Plague_: by which means, when timely used, that Distemper may sometimes be carried off without any external _Tumors_. Nay besides, a judicious Observer informs us, that in many of his Patients, when he had broken the Violence of the Distemper by such an artificial _Sweat_, a natural _Sweat_ not excited by Medicines would break forth exceedingly refreshing[67].

AND I cannot but take notice, as a Confirmation of what I have been advancing, that we had here the same kind of Fever in the Year 1713, about the Month of _September_, which was called the _Dunkirk Fever_, as being brought by our Soldiers from that Place. This probably had its Original from the _Plague_, which a few Years before broke out at _Dantzick_, and continued some time among the Cities of the _North_. With us this Fever began only with a Pain in the Head, and went off in large _Sweats_ usually after a Day's Confinement: but at _Dunkirk_ it was attended with the additional Symptoms of _Vomiting_, _Diarrhoea_, &c.

TO return from this Digression: From all that has been said, it appears, I think, very plainly, that the _Plague_ is a real Poison, which being bred in the Southern Parts of the World, is carried by Commerce into other Countries, particularly into _Turky_, where it maintains itself by a kind of Circulation from Persons to Goods: which is chiefly owing to the Negligence of the People there, who are stupidly careless in this affair. That when the Constitution of the _Air_ happens to favour _Infection_, it rages there with great Violence: that at that time more especially diseased Persons give it to one another, and from them _contagious Matter_ is lodged in Goods of a loose and soft Texture, which being pack'd up and carried into other Countries, let out, when opened, the imprisoned Seeds of _Contagion_, and produce the Disease whenever the _Air_ is disposed to give them force; otherwise they may be dissipated without any considerable ill Effects. And lastly, that the _Air_ does not usually diffuse and spread these to any great Distance, if Intercourse and Commerce with the Place infected be strictly prevented.