The Changes wrought in the Animal Oeconomy from the above-mention'd
Causes, may be reduced to such as depend either on the Increased Heat of
the Air join'd with its Humidity; Or to such as are produced from the
particular Qualities of the putrid and Contagious Particles floating in
it; Or to the united and complicated Effects of all together.
[Sidenote: _Effects of a hot and
moist Air._]
The Alterations produced in the Body from a greater Heat continually
surrounding it, provided it be not Excessive, are a Rarefaction of the
Juices, and Relaxation of the _Fibres_ on the Surface of the Body, and
greater Derivation of the Fluids that way. Whence proceeds a large
Evacuation of the perspirable Matter. This being continued in a greater
Proportion than in a Natural State, will gradually deprive the Blood of
its Aqueous and Spirituous Parts, and leave the remaining serous Part
more stock'd with acrid and pungent Salts, and the Gross, Terrestrious,
Oleaginous, and Viscous Particles more firmly united by their nearer
Approach, and stronger Cohesion to each other. This greater Heat or
Quantity of Fiery Particles, continually surrounding the Body, will
necessarily insinuate it self into, and unite with the Saline,
Sulphureous, and other Particles, in the same manner as we see it does
with other Substances, both Solid and Liquid[l]; And likewise by
increasing the Velocity of the Circulation and Attrition of the
Particles against each other, render them on these Accounts also more
Volatile, Pungent and Stimulating, and consequently the Blood will
consist of Particles more gross and inspissated or coagulated, and
likewise of those of a more acrid and pungent Disposition than in a
natural State.
[l] _Boyl_'s Experm. Nov. de Pond, Ignis & Flam. _Newtoni_
Optic. Quæst. 21 & 22.
The Blood being in this depraved Condition, the rest of the Animal
Juices must degenerate in Proportion thereto, and the Nervous Fluid, as
it consists of the most volatil and subtil Parts, be extreamly acrid and
pungent, as well as unequal in its Texture and Fluidity, from the more
viscous Parts contain'd in it.
[Sidenote: _Putrid Fevers how
produced._]
This then being the State of the Blood and other juices of the Body, it
is easy to perceive how from very Slight, and otherwise trivial
Occasions, a Fever of a very Malignant Nature may be produced. Thus the
perspirable Matter from a slight Cold taken being retained, or the
Vessels any otherwise filled by Irregularities in Diet, or others of the
Non-naturals, the Weight of the moving Fluid will be increased, and the
Circulation be more languid and slow. Whence the intestine Motion of the
Particles of the Blood being diminished, the viscous Parts will cohere
more strongly and in greater Quantities than before, and obstruct the
Capillary Arteries, especially in the Extremities, and a Coldness,
Stretching, Yawning, Torpor, _&c._ necessarily succeed, the constant
Attendants of a beginning Fever; All which will bear a Proportion to the
Quantity retain'd, and the Viscosity of the moving Fluid.
These Disorders will necessarily be increased on account of the Air's
Spring being weakned by its Heat, the Vessels of the Lungs being less
inflated, and the Globules of the Blood less broken and divided, and the
more especially in a humid Air, Heat and Moisture necessarily relaxing
the Tone of the Fibres and Vessels, and rendring them less Springy and
Elastic. Hence then the Quantity of Spirits being diminish'd, and their
Motion more slow, the Contraction of the Heart and other Muscles will be
more weak and languid, and being stimulated by the Acrimony of the
Circulating Liquors, must contract more frequently than in a Natural
State; The Consequence of which is Weakness, Faintness, Thirst, and
Dejection of Spirits.
These and the preceeding Symptoms will necessarily continue, 'til such
time as the gross and viscous Matter, being shook and loosen'd by the
Action of the Capillary Vessels, is washed away into the Veins by the
force of the Circulating Fluids, and there continues its Course with the
rest, 'til it be either attenuated and secreted, or lodged again in the
Capillaries to excite new Disorders.
[Sidenote: _Malignant Fevers._]
Now if to this evil Disposition of the Air be added a number of pungent
stimulating Particles, whether bred in the Body or floating in the Air,
and thereby communicated to the Blood, which are apt to coagulate the
Animal Juices, so as to form _Moleculæ_ of such Shapes and Sizes as more
firmly obstruct the Capillary Vessels, and at the same time stimulate
and corrode the nervous Parts; It will necessarily happen, that the
preceeding Symptoms must be highly exasperated, and a Fever of a much
worse Nature produc'd.
Hence then must follow a violent Hurry and Colluctation of the Fluids,
the Viscid and coagulated Parts of the Blood in some Parts obstructing
the Circulation of the Juices, and the Acrid, Volatil, and Fiery Parts,
rarefying and dissolving others of the more Liquid, to the greatest
degree of Pungency and Volatility imaginable.
Hence it is easy to perceive how the Motion of the Blood must
necessarily be in some Parts more languid, by the Cohesion of the more
Viscous parts, in others quicker, join'd with a pungent and stimulating
heat, from the increased Velocity and Acrimony of the moving Fluid, and
the various Actions of the Particles upon each other, and their Impulses
on the containing Vessels; As also how these are capable of almost
infinite Variations, in Proportion to the different Quantities and
Qualities of the constituent Particles. Hence then appears the Reason of
that wandering and uncertain Heat and Coldness, in different Parts of
the Body at the same time. Hence appears the Reason of that great
Inquietude and Anxiety, of those uncertain and partial Sweats,
Watchings, Tremors, stretching Pains of the head, and the like, as will
be more fully shown hereafter.
But before I proceed to explain the Nature of a Fever truly
Pestilential, it will be necessary to observe, that notwithstanding the
foremention'd putrid Disposition be generally a Prelude to a
Pestilential Constitution of the Air, yet it has never that I know of
been observ'd, that these Causes alone at their first Onset, produced a
real Plague or Pestilential Contagion, without the Concurrence of some
preceeding Infection, either brought from abroad, or gradually augmented
from the increased Putrifaction of the Air, and Poisonous Steams of
Morbid Bodies.
Thus the putrid Air of Camps in hot Countries is frequently found to
produce Pestilential Fevers, but this never happens at their first
Onset; The Diseases first appearing being Fluxes, Putrid, and afterwards
Malignant Fevers; which being exasperated and propagated by the Virulent
Effluvia of Diseased Bodies, and the increased Putrifaction of the Air,
grow up gradually to those of a Pestilential, and exceedingly infectious
Disposition.
[Sidenote: _Of Putrifaction &
Fermentation._]
Now Putrifaction being only a kind of Fermentation, wherein the
Particles of a putrifying Body are put into an intestine Motion, and by
their Action and Attrition broken and divided, and since all fermenting
Substances do emit vast Quantities of small separable Parts, it will
necessarily follow, that the most subtil and active Particles of the
Purifying Body will be elevated into the Air, and float in it.
[Sidenote: _Effluvia from putrified
Bodies what._]
These Effluvia consist of the finest and most volatil saline and
oleaginous Particles, highly attenuated and set at Liberty from the
gross Oil and Terrestrious Part, as appears from the Distillation of
such Substances, all which afford great Quantities of a pungent and
volatil Salt. It is likewise observable, that the subtil Oleaginous
Particles being specifically lighter, as well as more easily attenuated
and divided than those of a Saline Nature, will be thrown off in greater
Proportion in the beginning of the Fermentation or Putrifaction than the
heavier Salts will be, which must either be more attenuated and
volatilised, or require a greater force to raise them into, and sustain
them in the Air than the former, and consequently the greatest Emission
of these saline Particles will be after the Fermentation has been for
some time continued; As we find it happens in all fermenting Liquors, as
Wine, Beer, Cyder, and the like. All which emit, during the
Fermentation, greater Quantities of Particles of an active attenuated
Oil or Spirit for some time, than of a Saline Nature, which requiring a
longer time in order to attenuate them, are not raised till the former
are in a manner quite exhaled, as appears from collecting the Steams of
fermenting Liquors, and of those which are turn'd sower by Distillation,
and consequently the Exhalations arising from putrifying Bodies will
after some time consist mostly of Saline Particles highly attenuated and
volatilised, and those not wrapt up and sheathed in the Oily ones, and
thereby render'd innocuous, and often useful to the Body, but naked and
exceedingly acrid and poignant.
How unfit an Air stock'd with these kind of Particles is for
Respiration, appears from several of Mr. _Boyl_'s Experiments on
Animals, shut up with putrified Air in the Receiver, most of which with
incredible Inquietude die sooner than in _Vacuo_, as also from the
pernicious Effects of the Steams of Vaults, Mines, the _Grotto de Cane_,
and such like. But besides this Inaptitude of such Air to expand the
Pulmonary Vessels, these minute and pungent Particles may be considered
as so many _Stimuli_ or Lancets, acting upon and penetrating the Coats
of the Stomach, Lungs, and other Vessels. On which Account they are not
only capable of creating great Disordes, as Inflamation, Pain, Sickness,
Anxiety, Vomiting, _&c._ in the Stomach and Nervous Parts; But likewise
being carried immediately into the Blood, will there stimulate the
ultimate Vessels, ferment, dissolve, or coagulate the circulating Juices
according to the particular Qualities and Quantity of the Contagious
Particles. Nor is it unlikely, that from the various Action of the
Particles upon each other, and their different Combinations in a
stagnating Air, Particles may be formed of Qualities vastly differing
from, and in their Force almost infinitely exceeding those of their
Primogenial Salts and first Principles, as in Sublimate, some
Preparations of Antimony, _&c._ Instances of which those versed in
Chymistry are no Strangers to.
[Sidenote: _Infectious Particles how
produced._]
Now supposing the Blood Saturated with these kind of Particles, and a
Malignant Fever produced by their means, we all know that the Blood in
this State throws off vast Quantities of subtil and active Particles
thro' the Perspirable, Salival, and other Excretory Ducts of the Body,
which not only must load the adjoining Air with great Quantities of
them, and render it capable of producing more dismal Effects than the
preceeding, but also the Particles thus thrown off must be endued with a
more acrid and pungent Disposition than the former, inasmuch as they are
more subtily divided and attenuated by the Force of the Fever, than
those in the preceeding Disposition of the Air, where so powerful an
Agent was wanting, And consequently produce a Fever of a most infectious
and deleterious Nature; And especially when the Infection is taken
toward the latter end of the Disease, at which time the Saline Particles
will be more exalted and volatilised, as well as thrown off in greater
Quantities, and thereby made more capable of producing an infectious
Contagion.
For the Blood in these Circumstances may not unaptly be compared, as was
before hinted, to a fermenting Liquor, whose Parts being constantly in
Motion, are continually throwing off great Quantities of subtil and
active Spirits, capable of exciting the same Fermentation, and producing
the same Qualities in those of the like Species, as appears from our
manner of fermenting Ale, Beer, _&c._ with Yeast, which is a Spirituous
Ferment, and also from the Sower Ferments used in making Vinegar, _&c._
Analogous to this we may observe, that the Blood in different Diseases,
as well as different Animals, throws off great Quantities of active
Particles, which when mixed with the Blood of a Healthful Person, are
capable of exciting the same Fermentation and Disorder in the Animal
Juices, with those of the Morbid Animal from which they exhale, as we
find in the _Small-Pox_, _Measles_, _Saliva_ of a _Mad-dog_, and the
like.
This then being the Disposition of the Blood and other Juices, in those
Fevers which we call Pestilential, it is evident, that whatever the
particular Substance of the Contagious Particles may be, they must be
endued with such Qualities as will Coagulate the Animal Juices,
Stimulate the _Fibres_ to frequent Vibrations, cause Obstructions in the
Capillary Vessels, and render the Blood and other Juices of the Body
exceedingly Acrid and Pungent, as appears from hence and the foregoing
Propositions; The Symptoms and Consequences (_cæteris paribus_) being
the same, whether the Disease has gradually grown up to this Height, or
took its Rise only from Contagious Particles brought from abroad.
[Sidenote: _How propagated._]
This is the Method by which I suppose these Contagious and Pestilential
Particles to be first generated and produced, in those places which are
most subject to them, and thence propagated first into the
Neighbourhood, and afterwards to greater Distances by way of Intercourse
and Commerce. The Pestilential _Effluvia_ being pack'd up and conveyed
in Goods of a soft and loose Texture, as Silk, Wool, Cotton, and the
like; And so much the more easily, as the Air into which these infested
Materials are brought, is predisposed to act in full Concert with them;
as happens in all Places at some times more than others; At which time
if these infectious Particles be communicated, they exert their Rage
with the utmost Violence, but frequently are either dissipated and lost,
or produce Diseases of less fatal Consequence, in an opposite
Disposition of the Air.
[Sidenote: _Why the Plague ceases._]
Thus hard Frost, strong cold and Northerly Winds, are found frequently
to put an End to, or at least bridle the Fury of Contagious Diseases,
and render them more mild and curable, as was observable in the
Beginning of the last great Plague in _London_[m], and frequently taken
Notice of in other places by the Writers on this Subject. Consonant to
this we find in _Ægypt_, that the Rising of the _Nile_ by giving a fresh
Motion to, and altering the Disposition of their stagnating and putrid
Air, by the mild Vapours and Nitrous Exhalations[n] issuing from it,
immediately checks the Raging of the Plague, and reduces it to a Fever
of a more mild and curable Nature; insomuch that as _Purchas_ and others
inform us, if there die in _Grand Caire_ 500 Persons of the Plague the
Day before, yet upon the Increase of the River it ceases to be
Pestilential, and none die of it[o]. And indeed it can hardly be
imagin'd, how the Plague when it has once got establish'd in any Place,
shou'd cease but with the Destruction of all or most of the Inhabitants,
was it not checked by some Alteration in the Disposition of the Air, and
gradually reduced to a Fever of a more mild and curable Disposition.
[m] _Hodges_ de Peste.
[n] _Boyle_'s determ. Nat. Effluv. cap. 4. _Plot_'s Nar. Hist.
of _Staffordsh._ cap. 2. pag. 42.
[o] _Purchas_ Pilgrim, lib. 6, cap. 7. _Sandy_'s Travels, lib.
2. cap. 97.
It will I think be needless to show, that the Distempers here treated on
are propagated by Contagion; But it may not be altogether unnecessary to
explain by what Methods these Alterations in the Animal Oeconomy are
brought about, and especially as the Means by which they are chiefly
communicated, have not that I know of been fully examin'd.
[Decoration]