Part 1 — 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, Diarrhœa, &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.