Much honoured and worthy Gentlemen, Trustees of this Academy,

HAVING some Things to offer which I conceive may be of pub­lick Benefit, I thought they could not be more properly address'd, than to a Sett of Gentlemen, who were so sensible of the Neces­sity and Usefulness of Academical Learning, as to become, in the most generous and disinterested Manner, the first Promoters of it in this Place. In all Places for Education, Medicine has been ever accounted one of the most useful Branches of natural Knowledge; and every At­tempt to improve any Part of it, has been always countenanced and en­courag'd by the Friends and Well-wishers of the liberal Arts. I make no Doubt then but you will favour me with your Attention, while I propose some Things to your Consideration relating to the SMALL-POX, a Disease at present in this Place, and which oftentimes proves fatal in every Part of the World where it has hitherto been known. As I have not been us'd to ha­rangue in this publick Manner, I rely entirely on your Candour and Good-nature, to make a proper Allowance for all Defects in Point of Oratory. Truth, indeed, stands seldom in Need of any Embellishments, and often appears to the greatest Advantage when dress'd in its own native Simplicity; more especially these Sort of Truths which are rather intended to convince the Mind than excite the Passions. The Flowers of Rhetoric on such Oc­casions, appear, for the most Part, only as so many specious and superflu­ous Ornaments. I shall endeavour, therefore, to deliver myself with all the Plainness and Brevity I am capable, and the Nature of the Subject will admit.

[Page 8]EVER since the SMALL-POX appear'd in the World, it has always been accounted a dangerous, and frequently a mortal Distemper: When the Disease is violent, it is certainly extremely dangerous in its own Nature, but capable of being rendered much more so by a wrong Management. The hot Regimen, which was universally practis'd before Sydenham's Time, and by too many since, has hurried Numbers out of the World, which might have been easily sav'd by a different Treatment: But every Thing relating to the Management of the Patient thro' the Course of the Distem­per having been so fully handled by others, I propose not to dwell upon it in the present Discourse. My principal Design is, to offer some Things concerning the Preparation of the Body, and the Manner of receiving the Infection; which, from any Thing I have yet seen, appears to me, never to have been consider'd with that Attention the Importance of the Subject deserves: This too seems the more necessary, as there are some Points re­lating to this Matter, of the utmost Consequence to the Life and Safety of Numbers of Mankind, concerning which, People are by no Means agreed in their Opinions.

WITHOUT farther Introduction then in treating this Subject, I propose to observe the following Method.

I. I shall premise some general Things, and enquire a little into the Na­ture of this Disease.

II. From these Premises I shall endeavour to show what State of the Body is best fitted to receive the Infection, and how it ought to be prepared, as well in those who receive it in the natural Way, as in those who take it by Inoculation.

III. I shall try to discuss this Question, viz. Whether it be safest and most eligible to run the Risque of catching this Distemper without any Precaution in the natural Way; to take the Infection in the natural Way premeditately after due Preparation; or by Inoculation? And,

LASTLY, I shall conclude with a few Reflections on the whole.

To begin then with the first Thing in the Method, which was to pre­mise some general Things, and enquire a little into the Nature of this Dis­ease. Tho' ^* some have taken a good deal of Pains to show, that the SMALL-POX was described by the old Greek Physicians, under the Title of Carbuncle, yet I must own myself of the same Opinion with the learned and judicious Sydenham, ^† that the Places quoted in Proof of it, are most un­reasonably wrested, and that in Reality the SMALL-POX is not to be found described either in Hippocrates or Galen. Had it existed at that Time in the World, he thinks so sagacious an Observer as Hippocrates, would not fail'd to have described it with his usual Exactness and Accuracy, so as to [Page 9] leave no room for any Dispute. The Arabians, therefore, seem to have been the first who have handed us down any authentic Accounts of this Disease.

IT seems highly probable, as well from Reason as Observation, that those epidemic Diseases which cannot be accounted for from the manifest Qualities of the Air, ( viz. Heat and Cold, Moisture and Dryness) have their Beginning, Encrease, Perfection, Declination and Period; and this, perhaps, in a great Measure, from the various Exhalations, that according to the different and unknown Alterations happening in the Bowels, or on the Surface of the Earth, taint the Atmosphere with hurtful Miasmata, which, tho' they be too subtile to undergo the Examination of the Senses, may yet act at certain Conjunctures on the human Frame, and produce particu­lar Diseases. This, I say, may be, and very probably is the general Cause of all epidemic Diseases which do not depend upon the manifest Qualities of the Air. Now, tho' the variolous Contagion, is generally taken from an infected Person, yet it is plain from Facts that the Disease is often epidemic, and that this epidemical Constitution of the Air is sometimes more, and sometimes less pernicious: Nay, so strongly was the Air of England taint­ed with an epidemical Constitution of this Sort for the Space of near three Years ( viz. in the Years 1667, 1668, and Part of 1669) that great Num­bers during that Season, who had already suffered the SMALL-POX, were seized with what Dr. Sydenham calls a ^* Variolous Fever, from its having every distinguishing Symptom of that Distemper, the Eruption of Pustles alone excepted: At the same Time too, the SMALL-POX was very frequent among those who never had the Distemper before. It is very likely that the Fuel for this Disease always existed in the human Blood, for the In­dian Natives of America, where the SMALL-POX was never known, be­fore the Europeans came amongst them, catch it as readily from an in­fected Person, as any other. Yet it seems very probable the SMALL-POX never appear'd in the World, before a variolous epidemical Constitution of the Air called it forth.

BUT it will be more to the present Purpose to enquire a little into the Nature and Effects of this Disease, now it has appear'd, than to examine when, or how it came into the World. Now it appears in every In­stance, that after the Variolous Contagion, whatever Way communicated, is mix'd with the Mass of Blood of any Person who never had the Dis­ease, it always produces an inflammatory Fever. And in Proportion to the Violence of the Disease, so always are the Symptoms of this conta­gious Fever, in so much that from these, for the most part, a pretty ex­act Prognostic may be form'd, whether the Disease will be more or less [Page 10] dangerous in its Issue. ^† Blood taken from a Person in the Beginning of this first Stage of the Fever, makes the same Appearance as in sound Health; but after it has continued three or four Days, it looks inflam'd and sizy, exactly like the Blood of a Person in a Pleurisy, or any other inflammatory Disorder. So nearly allied are the Symptoms of this con­tagious Fever to that of a simple inflammatory One, that unless a Phy­sician from other ^§ Circumstances had Reason to suspect this Disorder, the very best might be liable to be deceiv'd. All the succeeding Appearances in the Progress of the Disorder are evidently of the same Kind. The Eruption is no other than a Number of small Inflammations, which, when the Disease is moderate, regularly ripen into thick white, or yellow­ish Matter, and form small Abscesses, from which, however numerous they may be, there is seldom much Danger under due Management. On the other hand, when the Disease is violent, the dangerous Appearances are all of the gangrenous Kind, arising from a putrid Dissolution of the Blood, which are still the genuine Effects of a higher and more exasperat­ed Degree of the inflammatory Fever. The narrow Limits of this De­sign will not permit me to enter into a more minute Detail of Particulars; but it would be easy to show, that every threatening and mortal Symptom of this Disease proceeds from the Causes assign'd. I shall conclude, therefore, what I propos'd to premise in general concerning this Disease, with sup­posing it sufficiently prov'd, that whatever be the more hidden and abstruse Nature of the Variolous Contagion, when it comes to be mix'd with the Blood of a Person who never had the SMALL POX, it is posess'd of a stimulating Power, which produces an inflammatory Fever, and that fre­quently of the worst and most dangerous Sort.

I proceed now to the second Thing propos'd, which was to endeavour to shew, from the foregoing Premises, what State of the Body is best fitted to receive the Infection, and how it ought to be prepar'd, as well in those who take it in the natural Way, as in those who take it by Inoculation. In general then, as it appears from what has been offer'd, that the whole Danger of this Distemper proceeds from a high inflammatory Fever, pro­ducing a putrid Dissolution of the Blood, that State of the Vessels which is the least dispos'd to favour Inflammation, and that State of the Fluids which will be aptest to resist Putrefaction, must certainly be that State of the Body which is best fitted to receive this Disease. Now soft and flexi­ble Vessels, containing a cool and temperate Blood, has been found, by uni­versal ^* Experience and Observation, to be this State. Hence it is that old People, whose Vessels are stiff and rigid, are more indanger'd by the SMALL POX, as well as all other inflammatory Disorders, than Young. [Page 11] And hence, likewise, those whose Blood is heated by High-living and strong Liquors, are in great Danger by the same Distempers, than those who live more temperately. A very small Attention will easily discover the Reason of this. Every inflammatory Fever, as well as every topical Inflammation, is attended with an Obstruction in the small Vessels; and surely the more lax, and moveable these Vessels are, the more easily will these obstructed Particles find a Passage through them. Again, Putrefac­tion is always occasion'd by too much Heat, and animal Heat is generated by the Attrition of the circulating Blood, and the Action of the Vessels: Now the more soft, rare, and inelastic the Bodies ingag'd in Attrition are, the less Heat will be produc'd, caeteris paribus: But it appears, by many Experiments, that hot and intemperate Blood is compos'd of much more dense, compacted, and elastic Parts, than cool and temperate, and the Vessels that contain it are generally more tense and rigid; therefore a much greater Degree of Heat will be excited, even supposing the same Celerity of Circulation in both. A very moderate Skill in the Doctrine of Attrition, I imagine, is sufficient to discover the Force of this Reasoning. But be­sides this, cool and temperate Blood would much longer resist Putrefaction in the same Degree of Heat and Motion with that of hot and intemperate. For the Blood is compos'd of what we eat and drink, considerably alter'd indeed by the Action of the animal Organs, yet still retaining a good deal of the Nature of the Food it was form'd from. Now the temperate Blood here spoken of, is such as is chiefly form'd from a cooling, vegetable, or Milk Diet; and the intemperate such as principally comes from hot, in­flaming, animal Food, with high season'd Sauces, diluted perhaps with spirituous Liquors. But Milk, and all Vegetables (a few hot Antiscor­buticks excepted) by heat turn acid, which is directly opposite to Putrefac­tion, and resists it: Whereas, on the other hand, all animal Food, either Flesh or Fish, naturally tends to Putrefaction, and stands in no need of the Heat introduc'd by high season'd Sauces, or spirituous Liquors, to encrease and assist it. On this Account it is that the Flesh of those Animals, who live upon other Animals, putrefies a good deal sooner, than the Flesh of those who live intirely on Vegetables, in the same Degree of heat. Nay, most of the rapacious Birds of Prey, even while alive, have a foetid Smell. And it is certain, from Experience, that the human Body cannot subsist long on animal Food alone, unless it be qualified with Salt or Acids, with­out falling into putrid Disorders. ^* Van Swieten relates as an Instance of this, that while the great Boerhaave was himself afflicted with violent rheu­matic Pains, he propos'd to live intirely for some Time on Veal-Broth without Salt, in hopes it would both serve for Nourishment, and as a soft [Page 12] Medicine to sheath and blunt the Acrimony of the Humours which caused the Pain; but he could not bear it beyond five Days, and was obliged to fly to the Use of acescent Whey, upon which he lived wholly for a long Time, with great Relief from his Pain. Whoever reflects duly on these Things will, I imagine, be fully satisfied, that soft and flexible Ves­sels, containing a cool and temperate Blood, prepared chiefly from a sub­acid vegetable, or Milk Diet, must be in general that State of the Body which is best fitted to receive an inflammatory Distemper, whose dange­rous Effects is a putrid Dissolution of the Blood, which was previously shewn to be the Case in the SMALL-POX.

BUT I foresee an Objection which may probably be raised against what has been advanced. It may be ask'd, if this Matter be as it has been stated, how comes it pass, that sometimes a strong, lusty, gross Person, who takes the SMALL-POX in the natural Way without any Precaution, shall have it very moderately, whilst another, again, of a thin, spare, and seemingly more advantageous Habit, perhaps too, after a careful Preparation, shall have it in a much more violent Manner? It is undeniable Matter of Fact, that there have been Instances, which if they do not come up fully to this Case, at least come very near it: No body, however, I believe, will alledge that I have not done compleat Justice to the Objection; and I con­fess, at first Sight, it looks very plausible, but I think [...] of a fair and satisfactory Answer: First, then▪ [...] to be remem [...] that a thin, spare Person, may have hot [...], whilst the same Fluid in a more corpulent Habit, may be much more cool and temperate. Second­ly; By a careful Preparation, is for the most Part meant, an abstemious Diet, with Bleeding and Purging: But I must beg Leave to observe, that Errors are easily committed in pursuing this Course. By such Evacuations, and too abstemious a Diet, the Patient may be render'd too weak to un­dergo so tedious a Disease, and by over-purging, the Blood may be easily rendered hot, acrid and putrescent, which would be much worse than no Preparation at all; so that it requires more Skill to judge how far that Re­gimen, and these Evacuations, are proper in different Constitutions, than is generally imagined: And if the Qualifications of those who are often en­trusted with the Direction of such Affairs be candidly considered, there can, I think, little Doubt be made that they are frequently injudiciously used. But, thirdly; To give the Objection its full Force, let it be granted that sometimes (for the apparent Instances are but rare) the best prepared Body has the Disease worst, nothing more will follow than that those rare In­stances are Exceptions from a general Rule, and it is said that all general Rules have Exceptions. The Observations of the ablest ^† Physicians are all in Favour of what has been advanced, particularly those of the judici­ous [Page 13] Sydenham, to whom the World is indebted for almost all they know, both of the History and Cure of this Distemper. No Man ever had bet­ter Opportunities of making Observations; no Man ever observed with more Accuracy; and it is universally allow'd, that no Man ever related his Observations with more Candour. He tells ^§ us, he observ'd in ge­neral, that old People fared worse under this Disease than young, and Men worse than Women, the latter being naturally of a softer and laxer Tex­ture: That young Men again, in the Flower of their Youth, whose Blood was heated by free Living, were more in Danger than those who had not yet entered into Company: Nay, that the Children of poor People, who live chiefly on a homely vegetable and Milk Diet, generally had this Disease more moderately than the Children of rich People, who were us'd to higher Feeding. These Things, I should think, are sufficient to esta­blish the Truth of what was laid down, and remove the Objection; but perhaps, before what is intended to be said on some other Matters relating to the Preparation of the Body, be finished, these Instances on which the Objection is founded, may be made a proper Use of, and accounted for. I go on, therefore, to offer something farther on that Subject.

Now tho' the State of the Vessels, and Temper of Blood described, be certainly a most useful and necessary Part of the Preparation, yet I am humbly of Opinion, something more may be done; I think too, I have Reason from what I have experienc'd in Practice, to be of that Opinion: However, I shall explain myself candidly on this Matter, with as much Perspicuity as I can, freely submitting it to the Judgment and future Ex­perience of others. It appears to me then, highly probable, that there is a certain Quantity of an infinitely subtile Matter, which may be called the variolous Fuel, equally, intimately and universally diffused through the Blood of every human Creature, in some more, in others less, that lies still and quiet in the Body, never showing itself in any Manner hitherto discovered, until put in Action by the variolous Contagion, at which Time it is totally expelled in the Course of the Disease. First, I say, this variolous Fuel seems to be infinitely subtile; that is, so subtile as to evade the Discovery of our Senses, assisted by the best Helps yet found; because the Blood of a Person who never had the SMALL-POX, makes the very same Appearance, and affords the same Analysis under the strictest Exami­nation, as the Blood of o [...] who had already suffered the Disease. Se­condly; It seems to be equally, intimately and universally diffused thro' the Blood of every human Creature; for we find the Infection may be com­municated at all Parts of the Body equally; and all the different Inhabi­tants of the Globe, Europeans, Asiaticks, Africans, and Americans, have been hitherto found equally susceptible of the Disease. Thirdly; This [Page 14] variolous Fuel, seems in some to be more, in others less in Quantity, and very probably different likewise in Quality, for we see People of the same apparent advantageous Habits, very differently affected with the same In­fection. Nor are there any Marks hitherto discovered by which it can be so much as guess'd at, whether any Person has a greater or less Quantity of this variolous Fuel in the Blood, or whether it be of a greater or less malignant Quality. And this I think would serve to account for these In­stances in a former Objection, where strong, lusty, gross People, sometimes have the Disease very moderately, whilst others again of apparently more advantageous Habits, have it with much greater Violence; because, if the Quantity of this variolous Fuel in the former be small, and its Quality be­nign, the Fever and all its consequent Effects upon the Blood will be pro­portionably small; whereas on the other Hand, should those of more ad­vantageous Habits, have it in greater Quantity, or more malign Quality, tho' the Body would be better prepared to sustain an equal Degree of Fe­ver, yet as this would by no Means be the Case, the Danger would be much greater. But fourthly and lastly; this variolous Fuel lies still and quiet in the Body, until it is put in Action by the variolous Contagion, at which Time it is totally expelled in the Course of the Disease: This is so plain that nothing farther need be offered in Proof of it, than that those who have once had the Distemper, let them be never so much exposed to the Infection afterwards, are not liable to have it a second Time. Yet whether ever there was a well attested Instance of the same Person having the Disease twice, I shall not take upon me to determine. Supposing there was, some uncommon Accident or Particularity in the Constitution may have prevented the total Expulsion of it the first Time. But if there be any such Thing at all, it happens so exceeding rare, that it ought to be consider'd as a Kind of Prodigy, and then the Answer is, that tho' uncommon and extraordinary Phenomena of Nature appear sometimes, yet it is never thought a good Argument against reasoning from its usual Course. All the general Appearances then of the SMALL-POX evidently favour this Hypo­thesis, which is more than can be said of any other that I know of; but it was not with a View to establish a Piece of Theory that it was first ad­vanced, I proceed therefore to make the intended Use of it.

IF then there be such a subtile Matter in the Blood of all those who ne­ver had the SMALL POX, as, from what has been offer'd, appears, at least, highly probable, it would certainly be of the greatest Benefit to Mankind to find out a specific Medicine, which would either expel it in­tirely, alter it so as to render it quite innocent, or mitigate its malignant Quality. A Specific possess'd of the former Virtues would undoubtedly be the most desirable; yet a Medicine capable only of mitigating the Malig­nity of the variolous Fuel, would certainly make a noble Preparative for [Page 15] the Disease. It has been the Opinion of very eminent ^* Physicians, that a Specific for the SMALL POX ought to be sought for, and may probably be found. ^§ Boerhaave seems to think (for he speaks with Reserve) that from some Things he had seen perform'd by the Use of some of the finer, and milder Preparations of Antimony and Mercury intimately united, it was well worth while to make farther Trials of them, in order to find out a Specific in this Distemper. As for the general ^‡ Antiphlogistic Method, by which the same great Man proposes to check the Distemper in its first Stage, and prevent the Eruption of Pustles, or even after the Pustles have appear'd, to cure the Inflammation, and stop its farther Progress, I can­not take upon me to say how far it may be certain or safe to pursue it, hav­ing never seen'd it tried. But ^‖ he asserts, there have been many Instan­ces of its Success, while Physicians not appris'd of the SMALL POX, treat­ed the Symptoms and Eruption in the same Manner as they would have done any other high inflammatory Fever. The Danger of such a Method would be, that if it did not succeed, the large Bleedings necessary to be us'd, must render the Patient so weak, that he would be very apt to sink under the tedious and trying Course which he must afterwards undergo. This Method, therefore, is not likely to take Place, unless, by repeated Trials on Criminals condemn'd to Death, it was found certain, and to be depended upon. But the Trial of an easy operating antimonial and mer­curial Medicine, as a Preparative for receiving the Disease can be attended with no Danger. If it does not alter the variolous Fuel, so as to render it perfectly innocent, or expel it intirely, it may perhaps expel it in Part, or mitigate its malignant Quality; and in either Case the Advantage would be considerable. Tho' I cannot take upon me to assert any Thing positive­ly on this Matter, yet there can be no Harm in relating what I have ex­perienc'd in this Affair. On every Occasion, for the Space of twelve Years that I have been call'd upon to prepare People for the SMALL POX, either for receiving it in the natural Way, or by Inoculation (for I have prepar'd many for both) I have constantly us'd such a Medicine as has been mention'd, and I can honestly declare I never saw one so prepar'd, in any considerable Danger by the Disease. One of them indeed that receiv'd the Infection in the natural Way, had the confluent Pock, but I attributed that to his having rid near twenty Miles in cold damp Weather the first Day of the contagious Fever, being taken unwell in the Morning before he set off. However tho' he was a young Gentleman in the Flower of his Youth, he got very safely over it. This Disease is often so easily got over without any Precaution, that many People are unwilling to be at much Trouble about preparing for it, so that eight, ten Days, or a Fortnight, has [Page 16] been the longest Time I have ever been able to persuade any body to set a­part for it, which was too little. For as the variolous Fuel is universally diffus'd, in order to obtain the full Efficacy of the Medicine, the whole Mass of Blood ought to be richly impregnated with it. I met with one Instance, however, which, as it seems a little remarkable, I will take the Liberty to relate. About ten Years ago, in the Family where I lodg'd, there were five Children who had never had the SMALL POX. The eldest was about twelve Years of Age, and the youngest about two. They were all of healthy Constitutions, born of the same Parents, and liv'd after the same Manner, eating and drinking together every Day. The SMALL POX came to the Place, and their Mother would not hear of Inoculation. They were kept as much as possible out of the Way of the Distemper; but at last the eldest and youngest were both taken with very violent Symptoms, that presag'd a high and dangerous Degree of the Disease, which indeed they both had, tho' they got over it. This alarm'd the Mother, upon which she desir'd I would prepare the other three for taking the Infection in the natural Way. I gave them a Fortnight's Preparation in the Man­ner aforesaid, and then they came freely into the Room where the others were. Two of them took the Disease, yet in the most moderate Manner, so as never to lie by an Hour with it. But the third could not catch it at all, notwithstanding he slept in the Bed with his Brothers and Sisters with the SMALL POX upon them. This young Man is now an Apprentice to a Practitioner in this Town, and he tells me he has been frequently among the SMALL POX since, and goes at this Time, as he has done for some Time past, freely amongst them every Day, dressing inoculated Sores, &c. yet never has catch'd it to this Hour. I would not be understood to offer this as a Demonstration of what has been suggested, for I know there are Instances of People having resisted very strong Degrees of the Infection, who have afterwards taken it on very slight Occasions, and perhaps this Youth may be amongst that Number. It is far from my Intention to im­pose by drawing certain Conclusions from doubtful [...]remises: But after having stated Things fairly, and in the clearest Manner I could, I leave every Man to judge for himself.

I HAVE purposely avoided giving any formal Directions about the Preparation, thinking it sufficient to propose the general Intentions to be pursued, which every judicious Physician easily knows how to exe­cute, and adapt to different Constitutions; for I think none else ought to be intrusted with a Matter of this Sort. Nor do I mean by such, all those who by the Courtesy of America are stil'd Doctors, because it is well known that Surgeons, Apothecaries, Chymists, and Druggists, or even mere Smatterers in any of these, are all promiscuously call'd by that Title, as well as real Physicians. I mention this as well to make [Page 17] People a little more careful in examining into the Pretensions of those they intrust as Physicians, for surely it is a most important Trust, as to gain the Method of Preparation propos'd fair play.

HAVING thus finish'd what I intended on the second Thing in the Me­thod, I proceed now in order to the third Thing propos'd, which was to try to discuss this Question, viz. Whether it be safest and most eligible to run the Risque of catching the SMALL POX in the natural Way without any Pre­caution, to take the Infection in the natural Way premeditately after due Pre­paration, or by Inoculation? Now whoever attentively considers what has been said concerning the Nature of this Disease, and the Advantages of a proper Preparation, must, I think, allow that the same Person would certainly have the Disease much more moderately, while his Body was in that State described as the fittest, than if he was to have it under the oppo­site Circumstances. But no one who runs the Risque of catching the Dis­ease at random can tell but the latter may be his Case. Nay it is most like­ly to be the Case; for the more hot and putrescent the Blood is, the more tense and active the Vessels are, the apter they will be to imbibe any Thing applied to them. An Instance of this we see in acute Fevers, where that is the State of the Blood and Vessels. Let a Person in this Condition drink as much as he will, the Moisture applied to the Vessels of his Mouth and Throat is soon suck'd up, and they quickly again feel parch'd and dry, which evidently shows that this Power of Absorption in the Vessels, by which Power alone it is that any Thing is taken into the Blood, is encrea­sed by that very State of the Body which is most unfriendly to the SMALL POX; consequently, a Person will be aptest to catch the Infection when he is worst prepared for it. Seeing this is the Case then, it must certainly be the most dangerous and unsafe Method to run the Risque of catching the Di­stemper in the natural Way, without any Precaution.

BUT to this some will reply, Allowing the Matter to be as it has been stated, as there are Instances of some who never get the Disease at all, there is a Possibility of escaping it entirely; and besides that, getting a Distemper industriously looks like Presumption, or a tempting of Provi­dence. These Things, I am sensible, have considerable Influence on some People, but, with Submission, they seem to me to have little of any Con­sequence in them. For first, the Instances of those who never have the SMALL-POX at all, in populous Cities, where the Distemper is frequently among the Inhabitants, (for I speak only of such,) are exceeding rare, at most not one in ten Thousand. This Chance then is so small as scarcely to deserve any Consideration, when the Danger of running the Chance, and the Advantages of the other Method are set in Competition.

But farther, as the Almighty has form'd us rational Beings, he surely intended we should act on rational Motives; now Certainty is often out of our Reach, [Page 18] and Probabilities are the only rational Motives we have to act upon in most Cases. The Probability therefore of the greatest Safety being so strongly on the Side contended for, there can be no Presumption in acting agreea­ble to it; otherwise taking the most probable Means for Self-preservation, a Principle ingrafted in us by the Author of our Nature, would be acting presumptuously against him, which is a palpable Absurdity. The Pre­sumption in neglecting the most probable Means of Safety, seems ra­ther to lie on the other Side. But, in truth, tho' it be reckoned Presump­tion by some, yet there are many Things of the same Sort practised every Day by these very People, without any Scruple. Who amongst them, for instance, would hesitate to bleed, vomit, or purge, in order to prevent any dangerous Disease, which they had but the slightest Reason to be ap­prehensive of? And yet Bleeding, Vomiting and Purging, are all as real Diseases as the SMALL-POX, while they last, and such as have proved mor­tal too, even when they have been industriously brought on: Yet no Body calls this Practice Presumption, or a tempting of Providence. The Case, I think, is exactly the same with respect to the voluntary Way of taking the SMALL-POX. A less Danger is willingly embraced to avoid a greater, not on slight Grounds, but with great Probability apprehended. Thus I have endeavour'd to obviate an Objection, which I have known to stick with Numbers of well-meaning but scrupulous Minds, and I thought it my Duty to do so in a Discourse intended for the Publick, tho' perhaps it may have been unnecessary to the Bulk of more intelligent People: But having already shewn that to run the Risque of catching the SMALL-POX in the natural Way without any Precaution, is by far the most unsafe Me­thod, I proceed to examine, Whether it be safest and most eligible to take the Infection premeditately in the natural Way, after due Preparation, or by Inoculation?

AND first it may not be improper to remark, that, after due Pains taken to prepare the Vessels, one cannot be so certain of taking the Infection in the natural Way, as by Inoculation. The Regimen and Medicines would probably render the Vessels not so ready to catch it, which might conside­rably prolong the Care and Caution necessary to be used before the Affair was over: So that supposing both Ways of receiving the Infection equally safe, Inoculation ought to be preferred. But that we may search into the Bottom of this Matter, let us in the next Place suppose the Body equally prepared in both Cases, when the Infection is received, and then the only Difference will be in the Manner of receiving it, which, if I am not much deceived, will appear, on a strict Examination, to be of much more Importance than is generally imagined, and greatly in favour of Ino­culation. As the Contagion in infected Places is always contained in the Air, when it is received in the natural Way, it must be taken in by the [Page 19] Vessels of the Nose, Mouth, Throat, Lungs, or Stomach, from the Air drawn in by Inspiration, or swallowed down by Deglutition. For, tho' the external Skin abounds with bibulous Vessels, yet but little of that is expo­sed; and besides, their Orifices neither being so open, nor so moist, are not so fitly disposed to take in any Thing applied to them in that Man­ner. But the internal Coats of the Nose, Mouth, Throat, Air Ves­sels of the Lungs and Stomach, are all lined with a lubricating Mucus, fit to entangle the infectious Miasmata, and the inhalant Vessels of these Parts are always open, and ready to suck up and convey into the Blood whatever is applied to them: So that should the Contagion in the Air at any Time be strong enough to enter the inhalant Vessels of the external Skin, it would certainly enter the Vessels of these internal Parts at the same time, as it must be applied to them with such superior Advantages. Now the peculiar Advantage of Inoculation, I take to be this, that by this Method the Infection is convey'd into the Blood by the external Ves­sels alone, and that only from one particular Spot, which may be chose in any Part of the Body. It may be worth while therefore, to examine in what this peculiar Excellency particularly consists.

It is a Thing well known, that the Danger of all inflammatory Distem­pers almost wholly depends upon the Nature and Function of the Part where the Inflammation principally fixes. An Inflammation in the Legs or Arms for Example, or any external Part, is not near so dangerous as one in the Viscera of any of the Cavities of the Belly, Breast, or Brain. When the Inflammation suppurates in the former Case, it may always be cured, and often when it gangrenes; but any considerable Quantity of Matter lodg'd in any of the three Cavities mentioned, almost always proves mortal, and a Gangrene there is certain Death. Whatever then will be instrumental in determining the Crisis of the inflammatory Fever rais'd by the variolous Contagion, towards the internal and more noble Parts, must be hurtful and dangerous; whereas on the other Hand, whatever tends to lead this Crisis outwardly, and to the more remote Parts, must be highly advantageous and serviceable. That the Method of receiving the variolous Infection in the natural Way is of the former, and that by Inoculation of the latter Sort, appears to me strongly supported by the following Observations.

FIRST, we observe, that in other Poisons which induce an Inflammation or Gangrene, it principally affects those Parts where the Poison first enters, whether it be the internal Coats of the Nose, Mouth, Throat, Lungs and Stomach, or the external Surface of the Body. Secondly; It has been re­mark'd that the Pustles round the inoculated Part are generally very thick; nay I have often observed the whole Side on which the Inoculation was made, to be much thicker of Pustles than the other. Thirdly; The Wound itself, tho' made small, which would otherwise heal up in a few [Page 20] Days, often becomes an ill-conditioned Sore, and keeps running in most Cases for the Space of a Month, and in some a good deal longer. Fourth­ly; I have taken particular Notice, that those who take the Disease by Ino­culation, even when the Pock is equally numerous upon the Surface of the Body, are not near so subject to Sore Throats, and these other Symptoms which show the internal Parts affected, as those who take the Infection in the natural Way. From all which it would appear, that [...] variolous Contagion, which Way soever it enters the Blood, disorders the whole Body, and raises an inflammatory Fever, yet that it affects those Parts it enters at, in a particular Manner, so as to determine the Crisis of the Fe­ver principally that Way. This then, I say, seems to me to be the pecu­liar Advantage of Inoculation, that it determines the Crisis of the contagious Fever, from the internal and dangerous Parts to the external and less dan­gerous, which, as has been already shewn, must be of the highest Benefit.

GIVE me Leave to add, as a corroborating Circumstance, that the Effects of the different Ways of taking the Infection as described, will, in my humble Opinion, clearly account for a very remarkable Phenome­non of this Distemper, taken Notice of by ^* Dr. Sydenham, which hi­therto has never been accounted for, at least, that I ever heard of. The Phenomenon is this: That the Danger of the SMALL-POX is entirely to be estimated by the Number and Nature of the Pustles upon the Face; so that however few and distinct they may be upon the rest of the Body, if they are numerous and confluent upon the Face, there is the same Danger as if the Body was cover'd with the same Sort: The Observation holds too, vice versa. Now, agreeable to what has been said, if the variolous In­fection enters chiefly at the Vessels of the Nose, Mouth and Throat, which has been shewn to be the Places it is most likely to enter at when the Infection is taken in the natural Way, the Crisis of the contagious Fe­ver will be principally determined that Way. But the Carotid Arteries and others, which supply those Places as well as the Face, send likewise consi­derable Branches into the Brain, so that a proportionable Part of the same Sort of inflammatory Particles that constitute the Pustles on the Face, must be lodg'd in the Membranes of the Brain; and as they are of a mild and benign Sort or otherwise, will produce more or less Danger in the Course of the Disease. For the Face consider'd in itself, is a Place of no Dan­ger, and consequently one would imagine, no such Prognostic could be taken from it, but when for the Causes assigned, it comes to give certain Indications of the State of so important a Part as the Brain, the Case dif­fers widely, and the Reason of Sydenham's Observation appears evident.

BUT besides this, the Advantages described, arising from the Manner of [Page 21] receiving the Infection by Inoculation, are confirm'd by Experience; for it is a Thing well known in this Place, that at different Times, while the SMALL-POX was very mortal among those who took the Infection in the natural Way, great Numbers were inoculated, a careful Preparation being little practised, yet few, very few indeed, miscarried. Nor can this vari­ous Success be ascribed to the Care taken in communicating the Infection from a Pock of a good Kind by Inoculation; for we see frequent Instances of those, who live in the House where the SMALL-POX of the worst Kind is, having, notwithstanding, the Disease mild and moderate; whilst others again, who never had been near any in the confluent Sort, yet have it in the most violent Manner: Nay, some who have been inoculated from a Pock of the best Kind, have nevertheless had the worst. So that tho' it be a Practice to be very careful in getting the Infection from a Pock of a good Kind, and to be sure there is no Harm in it, yet it would seem to be a Matter of small Importance. If therefore the experienced Success of Inoculation can neither be ascribed to the Preparation of the Body, which was but little practised, or to that of taking the Infection from a Pock of a good Kind, which appears to be of no Moment, I cannot see any other possible Way of accounting for it, but from the different Way of receiving the Infection. I have endeavour'd to do this by Arguments, as I think, drawn from fair Reason, and just Observation; and I hope by this Time it appears sufficiently plain, that it is by far the safest and most eligible Way to take the variolous Infection by Inoculation.

HAVING thus finished what I intended on the three Heads of the Dis­course, I come now in the last Place to make a few Reflections on the whole.

AND first, from what was hinted in the Beginning of this Discourse, that an epidemical Constitution of the Air for producing this Distemper is some­times more, and sometimes less pernicious: I should think the best Time for getting over this Disease would be when it was accidentally brought to a Place, and there was nothing in the Air to favour it at all, or when the epidemical Pock was of a good Kind: For the Disease is to be suffered but once, and once every one who travels, or is obliged to be often in large Cities where it comes, must in all human Probability have it. And the History of the Disease shows, that it is at some Seasons much more mortal, than at others. Certainly therefore it will be running the least Risque, to try to get over the threatening Danger at the Season abovementioned.

SECONDLY; If those Parts the Infection enters at, be of such Consequence as to determine the Crisis of the contagious Fever principally that Way, it will undoubtedly be best to convey it at those Branches of the vascular System which have the most distant Communication with the Vessels that supply the more noble Parts. For this Reason, I should imagine it would be safest to inoculate in the lower Extremities rather than the upper, because the axillary [Page 22] Arteries, which chiefly supply the Arms, come from the Subclavians, and they derive their Origin from what is called the ascending Trunk of the Aorta, which sends off all those Branches which supply the Head, and a great Part of the Thorax, where the vital and dangerous Parts are contain­ed. Now, should the Crisis be principally determined towards the Arm where the Inoculation was performed, the vital Parts will be in more Danger of partaking of it, than if it was determined towards the Legs and Feet, as the Course of the Blood in those Vessels from whence the lower Extremities are supplied, lead quite a different Way. I know the com­mon Practice is to inoculate in the Arm, and perhaps a Sore in the Feet or Legs may be somewhat more inconvenient; but a Probability of greater Safety, in a Matter where Life itself is concerned, ought certainly to take Place of a mere Convenience. These Sores are sometimes extreme­ly troublesome, and difficult to heal, giving forth a thin, ichorous, cor­roding Matter, which both eats and inflames the adjacent Parts. To pre­vent or remedy this, about three or four Half Drachms of Jesuits Bark given at so many Doses through the Day, will, I believe, seldom or never fail to bring good Matter into the Sore, and dispose it to heal. I am sensible this Effect of the Bark in bad Sores, and even in the Pustles of the SMALL-POX, has been taken Notice of, and made known to the World by the de­servedly famous ^* Monro, of Edinburgh, whose Name, as one of my first Masters in the healing Art, it is my Duty always to mention with Gratitude and Honour. But having often experienced its good Effects in this particu­lar Case, I judg'd there would be nothing amiss in mentioning it by the bye.

But thirdly; From what has been said concerning this Disease, and the Advantages of a well prepared State of Body for receiving it, I think it clearly follows, that it will be much the safest Method to have the Body put into that State at all Times when the Disease is expected, as well in those who are determined to wait for it in the natural Course of Things, as in those who premeditately take the Infection. For tho' the SMALL-POX be frequently got over in a very easy Manner without any Precaution, yet as it often proves a dangerous and mortal Distemper, too much Care can­not well be taken in a Matter of such Importance. Inoculation has been shewn to be much the best and fafest Way of taking the Infection, yet even in this way it sometimes proves mortal; and indeed, considering how uncautiously and precipitantly this is often done, I am surpris'd it has not been much more frequently the Case. Inoculation seems to be consider'd by many as a mere chirurgical Operation, and accordingly we see almost every one who knows how to handle a Lancet intrusted with the whole Management of it: But it has been shewn, that what ought to be done [Page 23] on this Occasion for the Safety and Security of the Patient, a judicious and skilful Physician only can judge. In Matters of Property and Interest prudent Men are always cautious and circumspect, in proportion to the Value of the Thing in Danger. Now here, Life itself, the most valua­ble of all earthly Things, is liable to be put in the most imminent Danger by Mismanagement and want of Skill; and yet of all Professions in A­merica, the true Qualifications of a Physician are the least examin'd into. This seems something strange and inconsistent, but the Fact is notorious. It may, perhaps, be occasion'd, in some Measure, by a Notion which prevails even among some from whom better Things might be expected, that Physic is not a real Science, founded on just and rational Principles, but a Sort of Knack to be got intirely by Practice, which an ignorant, il­literate Person, may as readily attain, as one of Learning and Knowledge, who had taken due Pains to study it. If this was the true Notion of Phy­sic, the Distinction betwixt Physician and Quack would be without Foun­dation, for that is in Reality the Principle on which Empiricism is founded. But the ablest Physicians in all Ages have repeatedly confuted it, and prov'd it to be in the highest Degree senseless and absurd. They have bore their publick Testimony against it, as an injurious Slander on their Profession, exceedingly hurtful too in its Consequences to Mankind, as serving for a Cloak to screen Impostors. In every Country of the known World, where Learning flourishes, Physic is regularly taught as a Science, and studied as such by all those who qualify for practical Physicians. But without entering minutely into the Argument, whoever will be at the Trouble of making only a slight Examination into this Matter, will soon be convinc'd that the human Body is a pure Machine, and that its Disorders are not to be understood, however often they may be seen in Practice, without a particular Knowledge of its Organization and Structure. They would soon confess with Dr. Mead, that " ^* He is likely to be the best Physician, who having the same Assistance of Observations and Histories with others, best understands the Human Oeconomy, the Texture of the Parts, Motions of the Fluids, and the Power which other Bodies have to make Alterations on any of these." In the Knowledge of these Things, consists what is call'd the Theory or Principles of Physic, without which, says Sydenham, ^† He who endeavours to conquer Diseases, will be something like the Roman Andabatae, a sort of Gladiators, that us'd to fight blindfolded; or like a Mariner, who goes to Sea without a Compass. That some Things in this Human Oeconomy are not thoroughly understood, may be easily granted, and is undoubtedly true; yet nothing follows from the Con­cession, but that the Science is not perfect; and I would desire to know [Page 24] what human Science is? Many Things are certainly known concerning it, and he who knows these Things best, must be best qualified to judge of Observations in Practice; and he who is ignorant of them, understands nothing that he sees, and is not qualified for Practice at all. Yet the Mis­chiefs committed by the ignorant Professors of Medicine are seldom pub­lickly known, because the noxious Things they administer work all their Effects in the dark, within the hidden Recesses of the Body, which the greatest Part of Mankind are not qualified to judge of; and therefore are easily made believe proceeded not from the injudicious Administration, but the Malignity of the Disease, or some other Cause, which either the Em­piric himself through Ignorance thinks the true One, or artfully invents to save his Character. This however is an Unhappiness much easier lament­ed than remedied, unless the Legislature was to interpose in Behalf of the Safety of the People, and appoint proper Persons to judge of the Qualifica­tions of those who were permitted to Practice. This, I believe, has been done by all the well regulated Governments of Europe; and there is cer­tainly a better Reason why it should be done in a young Country, where the Arts and Sciences are but in their Infancy, because there the Bulk of the People being more illiterate, are more liable to be impos'd on, as they will be less capable of detecting Impostors.

YOU, Gentlemen, have made a laudable Attempt to erect an Academy in this Place for the Advancement of Literature, and the Improvement of the liberal Arts; I heartily wish your generous Endeavours may be crown'd with Success, to the utter Mortification and Discouragement of Impostors of all Kinds, and the Increase of true Knowledge, which is the Source of all individual, as well as social Happiness.