_Of the_ SMALL-POX.
From what has been said of the Nature of Malignant and Pestilential
Diseases it will follow, that the Contagious Matter producing the
Small-Pox does likewise Coagulate the Blood, and increase the Bulk of
its constituent Particles, and that in such a Proportion as are capable
of obstructing only the ultimate and perspirable Vessels, as appears, in
that it principally, if not solely affects the membranous Parts of the
Body, as well External as Internal. Now these Parts being formed of such
Vessels, the Pustules could not happen in these more than other Parts of
the Body, were not their Vessels thus obstructed, and obstructed they
cou'd not be, but from the increased Bulk of the Sanguineous Particles,
and that in such a Proportion as renders them capable of penetrating
into, but not passing thro' the Cavities of the ultimate Vessels, as
appears from the preceeding Propositions, and consequently, the
contagious Matter producing the Small-Pox, must be indued with this
peculiar Property. And indeed if we allow the different Degrees of
Coagulation in these Contagious Diseases, and which appear even to our
Senses, it will appear, that the Principal if not the sole Difference
proceeds only from the greater or less Bulk and Number of the Coagulated
_Moleculæ_, and Acrimony of the Coagulating Matter. Thus we see that in
Pestilential Diseases, where the Degree of Coagulation and Acrimony of
the Juices are superior to the rest, the Obstructions happen in the
larger Glands, as are those of the Armpits, Groin, _&c._ The Circulation
of the Blood being obstructed, or at lest much retarded in the Capillary
Blood Vessels, as appears from the weak Pulse, Coldness of the
Extremities, and the like, which constantly accompany it; And
consequently the _Moleculæ_ form'd by the Coagulation of the Animal
Juices must be larger, than these in the Small Pox, which proceed to the
ultimate Vessels before the Obstructions are formed. The _Measles_ are
another Confirmation of this Theory, whose _Moleculæ_ are still less
than the preceeding, as appears by their Eruption with greater Flatness,
and less Extension of the Obstructed Vessels. Thus also we see that in
all these Diseases where the Contagious Matter is more Virulent than
ordinary, or the Constitution of the Year more productive of these
Diseases, or join'd with a Hot Tense and Scorbutic Disposition,
Diarrhea's, Dysenteries, Purple Spots, Hemorrhages, Phrensies,
Convulsions, Inflammations, _&c._ equally accompany these as
Pestilential Diseases.
From what has been said in this and the foregoing Chapters may be
deduced the Reasons of the greater or less Virulency of the Small-Pox,
Measles, _&c._ in some Years more than others; As also why these
Diseases shou'd rage with the greatest Violence when join'd with, or
immediately preceeding a Pestilential Constitution of the Air. Hence
also appears the Reason why Pains of the Head, Stomach, Loins and Back,
preceed the Eruption of the Pustules, these Parts as nearest the Heart
being soonest obstructed, and the _Impetus_ of the Blood against the
obstructed Canals much greater than in the rest of the Body. As also why
the Pustules should appear so much sooner in the Face, Neck and Breast,
than other Parts of the Body, as appears from _Prop. 2_.
Hence likewise appears the Reason why the Fever, Vomiting, Pains, _&c._
preceeding the Eruption of the Pustules should cease or be much
diminish'd upon their Appearance; The _Moleculæ_, by the Force of the
Circulating Fluids, being driven into and fixt in the Cutaneous Glands,
and Secretory Vessels, whereby the Capillary Arteries being freed from
them, a more easy Passage is allowed to the Circulating Fluids. Hence
also appears the Reason why the Fever gradually increases with the
Augmentation of the Pustules, the Contiguous Vessels being compress'd by
their Distention, and the Obstructions in the Secretory Vessels made
more Numerous; whence the Quantity of the Perspirable Matter being
Diminished, and the Canals streightned, the Vessels will be more full,
and the Pulse more strong and frequent. Hence likewise it will follow,
that the more numerous the Obstructions are, and more pungent the
Contagious Matter, the more Violent the Symptoms will be, and the Matter
of the Pustules when suppurated become an Acrid and pungent gleety
Substance, or Laudable _Pus_. As also why the Time of Suppuration shou'd
vary in Proportion to the Virulency of the obstructing Matter; and
consequently the Reason of the Difference between the _Distinct_ and
_Confluent Small-Pox_. Hence also it will appear, that Bleeding, in the
Beginning of the Disease, ought only to be Administred where the
_Impetus_ of the Circulating Fluids is so great, that notwithstanding
the Diminution of the Force of the Blood by it, the protrusive Force of
the Circulating Mass will exceed the _Impetus_ made on the Obstructing
Matter by the Vibrations of the _Fibres_, and likewise why on its
imprudent Use in the Beginning of the Disease, the Pustules shou'd
disappear, and be driven back into the sanguineous Vessels. Hence also
may be deduced the Reason of the Flux by the Salival Glands, the
Swelling of the Face, Hands, and Feet, in the height of the Disease, the
Vessels being at this time Turgid by the Suppression of the perspirable
Matter; And likewise the Necessity of such Evacuations, as may reduce
the Pressure of the Fluids upon them to such a Proportion, as the Tone
of the _Fibres_ may be able to resist; And why where this is neglected,
a _Peripneumonia_, Phrensy, Delirium, _&c._ do frequently succeed.
_Lastly_, Hence may be deduced the Reason why the Small-Pox shou'd
rarely seize those twice, who have had a Competent Number of them. For
the Ultimate Perspirable Vessels being distended much beyond their
Natural Tone, by the Bulk of the Obstructing _Moleculæ_, the Secretory
Vessels must be left wider than before, and consequently less subject to
be obstructed by Particles of this Size; Agreeable to this is that
Observation of Dr. _Sydenham_ and others, That in those Constitutions of
the Air where the Small-Pox were very _Epidemic_, many (especially such
as attended the Sick) who before had been affected with this Disease,
were seized with a Fever in all Respects the same with that attending
the Small-Pox, except only the Eruption of the Pustules, and the
Symptoms which necessarily attend on them.
[Illustration]
THE
APPENDIX.
[Illustration]
The Pressure of the Atmosphere on the internal Surface of the Lungs, as
computed in the foregoing Pages, so much exceeding that made by the
ingenious Dr. _Kiel_, in the last Edition of his Book of Animal
Secretion, it may not be amiss for the farther Illustration of it, to
show that the Weight computed by that Learned Author is not really the
whole Pressure of the Atmosphere, but the Force of the Lungs in
Expiration, by which they exceed the Pressure of the Air upon them. For
let the Tube A B be inserted into the Vessel C D E F of any given
Dimension, and both the Tube and Vessel fill'd with Water or any other
Fluid, it is evident from the Writers in Hydrostatics, that the Vessel C
D E F will be pressed upon on every Part of its Internal Surface equal
to the Basis of the Tube, by the Weight of a Column of the contained
Fluid of the same Height with the Fluid, and whose Base is equal to that
of the Tube, and consequently every Inch Square on the Internal Surface
of the Lungs will be pressed upon by a Column of Air, whose Height is
equal to that of the Atmosphere, and base one Inch Square, which will
amount to the aforesaid Sum. _Vide Pag._ 34 & 35. Now if we suppose the
Tube X inserted into the Neck of the Bladder Y and the Air forced into
the Bladder in Expiration, to an equal Density with that of the
incumbent Atmosphere, it is evident that the Air will not go out by the
Tube without some external Force, being in _Æquilibrio_ with the
Atmosphere, and consequently the Force by which it is expressed thro'
the Tube, must be that by which it exceeds the Pressure of the
Atmosphere, upon the Orifice of the Tube.
[Illustration]
If any one think that I have allowed too large a Quantity of Air to be
taken into the Lungs in an Ordinary Inspiration, That is sufficiently
recompensed by supposing the Diameter of the _Larynx_ equal to O.5 and
its Orifice O.19 which is more than it can be, for the Diameter does not
exceed O.4, and consequently its Orifice will be but O.12. Now it being
demonstrated by the Writers in Hydrostatics, that Weights forcing equal
Quantities of the same Fluid out of the same Orifice, are to each other
as the Squares of the Times in which the Fluid is forced out, and that
in equal Times and Quantities of the same Fluid forced thro' unequal
Orifices, the weights are Reciprocally as the Orifices; The Powers
forcing an equal Quantity of Air thro' the Orifices O.19 and O.12 must
be to each other in a Reciprocal Proportion, compounded of the Squares
of the Times and Orifices of the Tubes; Which will be found sufficient
to answer any Objection of this kind, by any who will give himself the
Trouble to compute it.
_FINIS._
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Transcriber Notes:
Passages in italics were indicated by _underscores_.
Small caps were replaced with ALL CAPS.
Throughout the document, the oe ligature was replaced with "OE".
Errors in punctuation, spelling, and hyphenation were not corrected
unless otherwise noted. Many of the spellings look strange by modern
standards, but then the rules for spelling changed since 1721.
Footnotes were moved to after the paragraph they were referenced in. The
footnote identifiers are the same as in the book, with the identifier
"s" being used twice,
On page 38, "Convnlsions" was replaced with "Convulsions".