I FEEL myſelf impelled to addreſs the public a ſecond time on the ſubject of the inoculation for the Cow-pock, not only becauſe an enlarged experience of it has now enabled me to produce more deciſive evidence of its advantages, but becauſe ſome remarks upon my practice of this new inoculation have lately been made, which call upon me for an immediate reply.

I truſt it will be generally acknowledged, that the obſervations and opinions formerly adduced by me on this ſubject, are ſtrictly impartial and unprejudiced; alſo, that the facts on which they are founded, have been [2]related without the leaſt reſerve, and with the moſt ſcrupulous fidelity: notwithſtanding, my concluſions in reſpect to a point of conſider⯑able importance have been oppoſed in a man⯑ner which I deem wholly unwarrantable. I allude to the puſtular eruptions which appeared on more than half the patients firſt inoculated for the Cow-pock, under my direction; Dr. Jenner, in a late publication,^* having main⯑tained that thoſe puſtules could only proceed from variolous matter, introduced by inocula⯑tion into the conſtitution along with that of the vaccine. That objections would be made to this effect might be foreſeen, and they were accordingly anticipated in my Reports, where ſeveral facts and arguments are brought for⯑ward to prove, that all the caſes which I had repreſented as caſes of Cow-pox, were pro⯑duced [3]from the inoculation of the matter of that diſeaſe, uncontaminated with any other. Having done this in a manner which has generally been deemed ſatisfactory, I did not now expect that any gentleman would pub⯑lickly attempt to ſubvert my concluſion with⯑out firſt doing me the juſtice to ſhow, that the reaſons on which it was founded were defective or fallacious. Although I have been diſappointed in this expectation, yet as I have no other object in view than a diſcovery of the truth, I will fully ſtate all the reaſons which the ingenious inventor of the new ino⯑culation has advanced in ſupport of a contrary opinion. He firſt enters upon the conſidera⯑tion of puſtules at page 7, where he ſays, ‘"When I conſider the great number of caſes of caſual inoculation immediately from cows, which have from time to time pre⯑ſented themſelves to my obſervation, and [4]the many ſimilar inſtances which have been communicated to me by medical gentlemen in this neighbourhood: when I conſider too, that the matter with which my inocu⯑lations were conducted in the years 1797, 1798, and 1799, was taken from different cows, and that in no inſtance any thing like a variolous puſtule appeared, I cannot feel diſpoſed to imagine that eruptions, ſimilar to thoſe deſcribed by Dr. Woodville, have ever been produced by the pure uncontami⯑nated Cow-pox virus: on the contrary, I do ſuppoſe that thoſe which the Doctor ſpeaks of originated in the action of vario⯑lous matter which crept into the conſtitution with the vaccine: and this, I preſume, hap⯑pened from the inoculation of a great num⯑ber of the patients with variolous matter, (ſome on the third, others on the fifth day) after the vaccine had been applied; and it [5]ſhould be obſerved, that the matter thus propagated became the ſource of future ino⯑culations in the hands of many medical gentlemen, who appeared to have been pre⯑viouſly unacquainted with the nature of the Cow-pox."’

Were I to allow the above obſervations all the force which the author of them could reaſonably expect, they would ſtill amount to no more than negative proof, and conjectural inference againſt the evidence of poſitive facts. It muſt, however, be remembered, that the Cow-pox, as caſually produced by milking infected cows, differs conſiderably from that which is the effect of a regular ino⯑culation; the local affection in the former caſe conſtantly exhibits a deep blue colour, an appearance which the inoculated diſeaſe never aſſumes. The Cows alſo, according to Dr. Jenner's own ſtatement, readily communicate [6]the infection to the perſons who milk them, although ſuch perſons have undergone the Small-pox.^* Dr. Pearſon, on the other hand, has informed us, that he made numerous trials to give the vaccine diſeaſe, by inoculation, to thoſe who had previouſly received the Small-pox, but that all his attempts proved ineffec⯑tual. Therefore any arguments wholly founded upon the ſtrict analogy between the inoculated and caſual Cow-pox, muſt be conſidered as inconcluſive.

From the manner in which Dr. Jenner has referred to the inoculations conducted by him during the years 1797, 1798, and 1799, the reader may be led to infer, that his experience had been ſufficiently extenſive to equal mine. But it appears, from his publication in the ſummer of 1798,^† that his practice had not [7]then extended to more than eight caſes, and no opportunity to inoculate the Cow-pox was offered to him again till he obtained from me matter for the purpoſe in February 1799. With this matter, which the Doctor now reprobates as the contaminated ſource of puſtules, he inoculated twenty perſons, and in a letter to me at that time ſaid, ‘"The riſe, progreſs, and termination of the puſtule created by this virus on the arm, was exactly that of the true uncontaminated Cow-pox."’ This virus, however, which Dr. Jenner from his own experience declared to be ſo perfectly pure and genuine, was taken from the arm of an hoſpital patient, who had 310 puſtules, all of which ſuppurated. On what ground then can he ſay, ‘"I cannot feel diſpoſed to imagine that eruptions ſimilar to thoſe deſcribed by Dr. Woodville, have ever been produced by the pure uncontaminated Cow-pox virus."’

As a farther evidence of the genuineneſs of the Cow-pox matter which I ſent to Dr. Jenner, I have the teſtimony of Dr. Marſhall, who procured ſome of it from the perſons inoculated by Dr. Jenner, and in the courſe of five weeks extended its effects in Glouceſterſhire to 107 perſons, all of whom underwent the inocula⯑tion in the moſt favourable manner, nor did any puſtules that ſuppurated appear in a ſingle inſtance.^*

Dr. Jenner, in his laſt publication, has given a tranſcript of a great part of Dr. Marſhall's letter, in which the above 107 caſes are ſtated; but he does not repreſent theſe caſes as the effect of the vaccine matter ſent by me from the Hoſpital; on the contrary, he profeſſes to lay Dr. M's communication before his readers, to ſhow the reſult of the inoculation in par⯑ticular with the matter which he procured [9]from a cow at Mr. Clark's farm, at Kentiſh Town.^*

Now it is very extraordinary, but certainly a truth, that Dr. Jenner did not even obtain the matter from Clark's cow till after the date of Dr. M's letter, which is ſaid to contain an account of its effects by inoculation. Nor does Dr. Marſhall mention the matter received by him from Dr. J. till he had inoculated 423 perſons, when in a poſtſcript to the letter, giving a detail of the ſucceſs of theſe inocula⯑tions, he ſays, ‘"I ſhould have obſerved, that of the patients I inoculated, and enumerated in my letter, one hundred and twenty-ſeven were infected with the matter you ſent me from the London cow. I diſcovered no diſſimilarity of ſymptoms in theſe caſes from thoſe which I inoculated from the matter procured in this county: no puſtules oc⯑curred, except in one or two caſes, where a ſingle one appeared on the inoculated [11]arm: no difference was apparent in the local inflammation."’ ^*

Here the whole of what Dr. Marſhall has ſaid militates moſt pointedly againſt the opi⯑nion of Dr. Jenner, who in the above citation is plainly told, that the effects of the matter which he conveyed to Dr. M. differed in no reſpect from that which had been employed before, and which was ſent from the Inocula⯑tion Hoſpital.

Dr. Jenner has not only given an opinion, that the vaccine matter uſed by me at the Hoſpital was variolated, but he has alſo ven⯑tured to point out how it happened, viz. ‘"From the inoculation of a great number of the patients with variolous matter (ſome on the third, others on the fifth day) after the vaccine had been applied."’ The opinion here given would have had greater influence [12]had the Doctor firſt condeſcended to anſwer the reaſons I gave twelve months ago, to ſhew that it was unfounded: for I can hardly believe that mere conjecture on his part will be thought of ſufficient authority to diſannul the facts and arguments I had advanced.

Should all that Dr. Jenner contends for be granted, ſtill none of his obſervations can apply to thoſe patients who had puſtules, though inoculated with matter taken imme⯑diately from the cow, and to whom no variolous matter was applied during the whole progreſs of the infection. Inſtances of this kind the Dr. muſt have read in my Reports, and muſt at the ſame time have known them to be irreconcileable with his opinion. But I have diſcovered from repeated experience, that if the matter of Cow-pox, and that of Small-pox be inſerted in the arm of a patient, even within an inch of each other, ſo that on the [13]ninth day the ſame effloreſcence becomes com⯑mon to both the local infections, nevertheleſs, upon inoculating with matter taken from the Cow-pock tumour, the genuine vaccine diſeaſe is invariably produced. And I am convinced from experience, that the matter thus taken would not be more liable to produce puſtules, or a leſs favourable diſeaſe, than matter pro⯑cured directly from the cow.

I have already publiſhed ſeveral other expe⯑riments, to ſhew that the Cow-pox does not hybridiſe with the Small-pox, even when ino⯑culation is performed with the matter of theſe diſeaſes intimately mixed together in equal quantities. Dr. Jenner muſt likewiſe know, that his friend Dr. Marſhall has com⯑municated to him the following fact, which corroborates this opinion: ‘"I viſited a patient with the confluent Small-pox, and charged a lancet with ſome of the matter. Two [14]days afterwards I was deſired to inoculate a woman and four children with the Cow-pox, and I inadvertently took the vaccine matter on the ſame lancet which was before charged with that of Small-pox. In three days I diſcovered the miſtake, and fully expected that my five patients would be infected with Small-pox; but I was agree⯑ably ſurpriſed to find the diſeaſe to be the genuine Cow-pox, which proceeded with⯑out deviating in any particular from my former caſes."’ ^*

I have now, I preſume, ſaid enough to convince the reader, that Dr. Jenner's ſuppo⯑ſition is directly incompatible with eſtabliſhed facts; and I hope in future he will do the Hoſpital matter the juſtice to ſpeak of it as it deſerves. It has been employed by many medical gentlemen, both in London and in [15]the country, and I do not know of one in⯑ſtance in which it has not fully anſwered the utmoſt expectations of the inoculator. In making this remark I do not exclude^* Dr. [16]Jenner, for in a letter to me the Dr. acknow⯑ledges that it had ſucceeded better than any of the vaccine matter which he had tried before. I beg alſo to obſerve, that it had a very ſtrong claim to the Doctor's gratitude; for of the four hundred and twenty-three inoculations brought forward by him to ſhew the advantages of the vaccine virus as uſed by Dr. Marſhall, two hundred and ninety-ſix were performed with the matter ſent from the Hoſpital.

Laſt ſummer Mr. Abernethy procured at the Hoſpital ſome Cow-pock matter, which he tranſmitted to the Rev. Mr. Holt, Rector of [17]Finmere, near Buckingham: with this matter the Rector inoculated upwards of three hun⯑dred of his pariſhioners, in all of whom the diſeaſe proved mild and tractable. No vario⯑lous-like eruptions were produced, except on two perſons, who had each one hundred puſ⯑tules.^*

The Rev. Mr. Finch, who was ſupplied by Mr. Holt with ſome of this vaccine matter, inoculated 714 perſons, on none of whom did any puſtules, reſembling thoſe of the Small-pox, appear. Now as Dr. Jenner does not believe that variolous-like puſtules have ever been produced by the pure uncontaminated Cow⯑pock virus, he is involved in the dilemma of either relinquiſhing this opinion, or of admit⯑ting that the above were not caſes of genuine Cow-pox, becauſe in two of Mr. Holt's caſes puſtules occurred.

Although I differ in opinion from Dr. Jen⯑ner in not imputing the puſtular eruptions, produced in the caſes at the Hoſpital, to any adulteration of the vaccine matter, employed in the inoculations, yet I readily admit that they have been and ſtill continue to be the effect of ſome adventitious cauſe, independent of the Cow-pox.

This will clearly appear, from the following obſervations, which likewiſe tend to place the ſubject in a new light.

I had not long practiſed the vaccine inocu⯑lation at the Hoſpital, before I was requeſted to extend it into private families in the Metro⯑polis, where I ſoon diſcovered that the Cow-pox uniformly appeared in its mildeſt form, and was never attended with eruptions. I alſo ſupplied ſeveral medical gentlemen with the vaccine matter, which was uſed by them with the like reſult. Hence I began to ſuſpect [19]that there exiſted ſome peculiar cauſe which rendered the patients under the vaccine inocu⯑lation in the Hoſpital more liable to puſtules than others: and that this ſuſpicion was well founded I have ſince, from daily experience, been fully convinced.

At various times I procured the vaccine virus, as produced in different cows, and with it inoculated patients in the Hoſpital; but the effects of all the matter I tried were perfectly ſimilar: and puſtules proved to be not leſs frequently the conſequence of theſe trials than of thoſe made with the matter formerly em⯑ployed.

The laſt matter of the vaccine poiſon which I introduced into the Hoſpital, was obtained from Dr. Jenner, and originally taken from Clark's cow, before noticed: with this matter I inoculated at the Hoſpital on the ſame day three patients, on one of whom about 100 [20]variolous-like puſtules were produced. This inſtance, and numerous others of the like kind which I could adduce, decidedly prove, that where there can be no doubt entertained of the purity of the Cow-pock matter, with which the patients in the Hoſpital are inocu⯑lated, puſtules will frequently be the conſe⯑quence.

On the other hand I have to obſerve, from daily experience during the laſt twelve months, that among the great numbers of children re⯑ſiding in various parts of London, to whom I have transferred the Cow-pock infection, no inſtance of puſtules that maturated has occur⯑red. Now as theſe different effects of the diſeaſe between the patients in, and thoſe out of the Hoſpital did not depend upon any difference or alteration of the matter with which the inoculations were performed, the only cauſe remaining to which the frequent [21]occurrence of puſtules on the former can be rationally referred, is the variolated atmoſ⯑phere of the Hoſpital, which thoſe patients were neceſſarily obliged to inſpire during the progreſs of the Cow-pox infection.

Did it not lead me too much into detail, I ſhould ſhow from many circumſtances relating to the patients in the Inoculation Hoſpital, that other reaſons might from thence be ad⯑duced to ſupport the opinion here advanced.

Mr. Evans, Surgeon, at Ketley, in Shrop⯑ſhire, is the only perſon, except myſelf, who has given an account of the variolous and vaccine inoculations carried on ſeparately in different perſons at the ſame time, and in the ſame houſe, ſo that ſeveral of his patients, while under the vaccine infection, were ex⯑poſed to the variolous effluvia. The number of thoſe which he inoculated for the Cow-pox amounted to ſixty-eight; and it is worthy of [22]remark, that more than one-half of theſe patients had puſtules.^* It is true that the eruptions very rarely maturated; but ſtill their frequent occurrence would ſeem to ſhow they aroſe from the ſame cauſe as thoſe at the Hoſ⯑pital. I ſuſpect alſo, that in thoſe places where the Small-pox is epidemick, or very generally prevailing, the Cow-pox will be found to be equally liable to excite puſtules as in the Hoſpital.

During the very general and fatal preva⯑lence of the Small-pox at a village eight miles diſtant from London, more than 100 perſons were inoculated under my direction for the Cow-pox, of whom one in five had eruptions; and as theſe furniſh the only inſtances which I have experienced, out of the Hoſpital, of the Cow-pox producing the variolous-like puſtules, [23]I am diſpoſed to attribute them to the adven⯑titious co-operation of the variolous atmoſ⯑phere, to which the patients were expoſed.^† In what way the variolous miaſms act in thus modifying the Cow-pox, or why they co-operate in ſome and not in all caſes of vac⯑cine infection, I ſhall not even venture a con⯑jecture: the cauſes probably will continue as inexplicable as thoſe conſtitutional peculiarities which produce all the varieties of Small-pox.

A month had ſcarcely elapſed after the publication of my Reports on the vaccine diſeaſe, before I thought it neceſſary to inform the public, that the Cow-pock caſes at the Hoſpital had become conſiderably milder: obſerving that out of the 310 inoculations, only 39 were attended with puſtules, viz. out [24]of the firſt 100, nineteen produced puſtules; out of the ſecond, 13; and out of the laſt 110, only ſeven excited puſtules. Since the above ſtatement, which was publiſhed in July, 1799, the new inoculation has by me, or under my immediate direction, been extended to about 2000 perſons, with none of whom did the infection occaſion a ſevere diſorder, or excite one alarming ſymptom.

In the Hoſpital, however, the diſeaſe ſtill continues to occaſionally produce puſtules, though not more than in the proportion of three or four caſes out of 100. But in my private practice of inoculation for the Cow-pox, which has been very extenſive, I have not met with one inſtance in which any puſtules, reſembling thoſe of the Small-pox, occurred. Hence the advantages of this ino⯑culation over thoſe of that of the variolous, are (as far as relates to the comparative [25]ſeverity of the diſorder which they reſpec⯑tively excite) moſt ſatisfactorily evinced.

In order to ſhow that thoſe who had under⯑gone the Cow-pox reſiſted the infection of the Small-pox, I obſerved in my Reports, that up⯑wards of 400 of the patients who had received the former diſeaſe, were afterwards inoculated for the latter, which in no inſtance was pro⯑duced; though more than 100 of the patients had the vaccine diſeaſe ſo very ſlightly, that it neither produced any perceptible indiſpoſition nor puſtules. In addition to this, I can now ſay, that more than 1000 of thoſe who had undergone the new inoculation, have been put to the ſame teſt, and that the like reſult has been experienced.

The above facts, added to a multiplicity of others of a ſimilar import, publiſhed by ſeveral profeſſional men, clearly demonſtrate, that the Cow-pox inoculation promiſes moſt impor⯑tant [26]benefits to ſociety; and under this con⯑viction I congratulate the public on the great progreſs it is making, by which the real value of the invention will ſoon become generally acknowledged, and duly appreciated.

It was not to be expected that a diſeaſe originating in Brutes ſhould be recommended as a ſubſtitute for the Small-pox, and for this purpoſe be transferred to the human race, without exciting much obloquy and oppoſi⯑tion: indeed, ſeveral of the moſt valuable diſcoveries in medicine, have met with a ſimilar reception; among theſe may be in⯑cluded inoculation of the Small-pox, againſt which the clamour became ſo conſiderable, that it fell into diſuſe for ſeveral years. To regulate the diſputes which the introduction of that practice into this country occaſioned, and to direct the controverſy to the true points at iſſue, Dr. Jurin, then ſecretary to the Royal [27]Society, judiciouſly ſtated, that the fate of ino⯑culation depended upon the deciſion of the two following queſtions:

Firſt, "Whether the diſtemper, given by inoculation, be an effectual ſecurity to the patient againſt his having the Small-pox after⯑wards in the natural way?

Secondly, "Whether the hazard of the inoculation be conſiderably leſs than that of the natural Small-pox."

The application of theſe remarks to our inquiries into the merits of the vaccine, com⯑pared with thoſe of the variolous inoculation, is too obvious to require being pointed out. Now, if by diſtemper in the firſt query we underſtand that of the Cow-pox, and if in the ſecond we add new immediately before ino⯑culation, and ſubſtitute inoculated for natural, I would anſwer both queſtions in the affirma⯑tive, preſuming that the facts already brought forward on the ſubject, clearly decide the [28]Cow-pock inoculation to be preferable to that of the Small-pox.

An opinion has been propagated, and with ſeveral perſons has had conſiderable influence, that the power of reſiſting the inſection of the Small-pox, which the conſtitution derives from the vaccine diſeaſe, will continue only for a few years: but this is mere conjecture, contradicted by facts of caſual caſes of Cow-pox, and contrary to analogy.

We have abundant evidence to ſhew, that the Cow-pox and Small-pox are cloſely allied, and the effects of the former, by pre⯑venting the action of the latter, ſeem to prove that theſe diſeaſes, are in reſpect to a very principal point, eſſentially the ſame: and as the change which the conſtitution under⯑goes from the vaccine diſeaſe producing the effect above-mentioned muſt be ſimilar to that occaſioned by the Small-pox, why ſhould it not be equally permanent?

In regard to the comparative mildneſs of the vaccine and variolous diſeaſes, as produced from inoculation, I have been enabled to give a very different report from that which I publiſhed laſt year. The reaſon why ſeveral of the Cow-pox caſes then at the Hoſpital proved ſevere, like thoſe of the ino⯑culated Small-pox, has already been ſufficiently explained, and will, I truſt, have the effect of placing the Cow-pock inoculation in a more advantageous point of view than my former Reports preſented.

I have before obſerved, that of the laſt 2000 caſes of Cow-pox under my care, not a ſingle alarming ſymptom was excited; and I may now add, that during the laſt eight months I have not met with one inſtance of the vaccine diſeaſe, which has not been as favourable as the mildeſt caſes of variolous inoculation. I have no doubt, therefore, that [30]the inoculated Cow-pox is as much milder than the inoculated Small-pox, as the latter diſeaſe is milder than the caſual Small-pox: nay, it ſeems to me from the very benign form in which the vaccine pock has of late invariably appeared, that it may be conſidered as a diſeaſe perfectly harmleſs in its effects.—Indeed, upon this conſideration, ſeveral per⯑ſons have been perſuaded to have their chil⯑dren inoculated for the diſeaſe, although they were very doubtful of the reality of its anti⯑variolous power. For if it proved a ſecurity to the children againſt the infection of the Small-pox, the object would be attained by the ſafeſt means: if it did not, no harm would ariſe from the experiment, ſince it was tried merely as a preliminary expedient to the inoculation for the Small-pox. The reſult, however, has conſtantly furniſhed additional evidence in favour of the new inoculation, [31]and of courſe has tended greatly to promote the adoption of it in London.

Another conſideration, highly important to the community is, that as the Cow-pox, unleſs from the adventitious circumſtances before-mentioned, very rarely, if ever, appears with variolous-like puſtules, it would ſeem incapa⯑ble of propagating itſelf by effluvia.^* Hence by the ſubſtitution of the vaccine for the variolous inoculation, the caſual ſpreading of the Small-pox from the inoculated, a circum⯑ſtance which has greatly contributed to ſwell the bills of mortality for the metropolis, and of which the public has long juſtly com⯑plained, is completely avoided. Nor is it unreaſonable to conclude, that if the new ino⯑culation [32]were to be univerſally adopted, the variolous diſeaſe, in proceſs of time, may be wholly extinguiſhed.

In my former publication on the Cow-pox I ſubjoined a tabular ſtatement of the caſes, in order to ſhew at one view the reſult of each; and it was my intention to continue this table, ſo as to include all the inoculations that have ſince been under my direction: but as I now find ſuch a ſtatement could not be compriſed in leſs than one hundred pages, and from what has already been obſerved would be rendered in a great meaſure uſeleſs, I truſt the reader will readily excuſe its omiſſion. I ſhall there⯑fore conclude the ſubject with ſome practical remarks.

Thoſe who have had much experience in inoculating with the matter of the vaccine pock, muſt have obſerved that it is more apt to fail in communicating the infection than [33]variolous matter, eſpecially if it be ſuffered to dry upon the lancet before it is uſed. This does not ſeem to depend upon the virus of the former being more volatile and more eaſily carried off by evaporation than that of the latter, but from its becoming more hard and leſs diſſoluble upon exſiccation. Care ſhould therefore be taken to moiſten it a conſider⯑able time before it is uſed. When fluid matter is employed, the lancet ſhould be held nearly at a right angle with the ſkin, in order that the infectious fluid may gravitate to the point of the inſtrument, which in this direction ſhould be made to ſcratch the cuticle repeatedly, until it reach the true ſkin, and become tinged with blood. This method has many advantages over the common punc⯑ture, and I have found it a more conve⯑nient and effectual mode of performing the inoculation than any other. It may be re⯑marked, [34]however, that there are perſons who have never had the Small-pox, and are in⯑capable of receiving it by inoculation, or by any other means whatever. The proportion of theſe to thoſe liable to the diſeaſe have been differently ſtated by authors; I have not found them to be more than about one in ſixty; but as ſuch perſons alſo reſiſt the in⯑fection of the Cow-pox, the inoculation of the latter muſt therefore ſometimes fail, in⯑dependently of the mode in which it is per⯑formed, or of the matter employed.

When a conſiderable tumour, and an exten⯑ſive redneſs take place at the inoculated part within two or three days after the infectious matter has been applied, the failure of inocu⯑lation may be conſidered as certain, as where neither redneſs nor tumour is the conſe⯑quence. This rapid and premature advance⯑ment of the inflammation will always be [35]ſufficient to prevent the inoculator from miſ⯑taking ſuch caſes for thoſe of efficient inocu⯑lation. But there are other circumſtances under which I have found the inoculation to be equally ineffectual, and which as being more likely to deceive the inocula⯑tor, require his utmoſt circumſpection and diſcrimination. I here allude to caſes in which it happens, that though the local af⯑fection does not exhibit much more inflam⯑mation than is uſual, yet neither veſicle nor puſtule ſupervenes; and in which, about the ſixth or ſeventh day, it rapidly advances into an irregular ſuppuration, producing a feſter⯑ing, or cruſtaceous ſore. Care, however, ſhould be taken to diſtinguiſh this caſe from that in which the inoculated part aſſumes a puſtular form, though it continue for one or two days only, when the ſame appearances follow as thoſe above deſcribed; for I have experienced the latter inoculation to be as [36]effectual as where the tumour has proceeded in the moſt regular manner. Theſe obſer⯑vations, which I hope will be found uſeful to inoculators, are drawn from a conſiderable number of caſes, ſome of which created in my mind much anxiety for the reputation of the Cow-pox. For until I had aſcertained the diſcriminating circumſtances here pointed out, I conſidered every new appearance of morbid action, which ſeemed to take place at the inoculated part before the uſual period at which the diſeaſe affects the conſtitution, as ſuggeſting a doubt with reſpect to the efficacy of the inoculation. Hence I ſometimes judged it neceſſary to inoculate the ſame patient a ſecond, third, and even a fourth time. Some parents, however, were unwilling to ſubject their children to a repetition of the inocula⯑tion, and could not be prevailed upon to com⯑ply without much difficulty, even where their [37]refuſal might have been of fatal conſequence. I inoculated two children of the ſame fa⯑mily for the Cow-pox, the younger of whom was 18 months, and the elder four years old. On the fourth day the redneſs of the local affection in the elder extended to about one-third of an inch or more in diameter, and no veſicle appeared. On the ſixth day the red⯑neſs of the tumour was much increaſed. On the following day the tumour ſuppurated and produced a ſuperficial ulcer for two or three days, when the induration and inflam⯑mation of the part wholly went off, and the fore healed. In the younger child the pro⯑greſs of the infection was perfectly regular throughout all its ſtages, and the diſeaſe was extremely mild. On the ſixth day I told the parents of theſe children that the elder had not received the Cow-pox, and that a ſecond inoculation would be neceſſary; at this they [38]appeared ſurprized, and obſerved, that the inoculation had produced more effect upon the elder than the younger child. However, on the ninth day they ſuffered me to re⯑inoculate the elder in both arms, when each puncture produced the true vaccine puſtule, and the infection proceeded in the moſt re⯑gular manner.

Of miſtakes, ariſing from ineffectual caſes of the variolous inoculation, many inſtances have come under my knowledge, one of which was ſo very remarkable that I ſhall re⯑late it here. Not more than two months ago I was deſired to attend a boy about five years old affected with the caſual Small-pox, of the moſt confluent kind.

I was informed by the father that his ſon who was then ill of the Small-pox had been inoculated for this diſeaſe three years before by Mr. —, who was a profeſſional man of much experience; but as no puſtules were [39]produced from the inoculation, he requeſted Mr. — to try the effect of a ſecond inocula⯑tion, and this requeſt he earneſtly repeated at different times. Mr. — however declined it, and aſſured him that his child was perfectly ſecure againſt the Small-pox. The boy was therefore ſuffered to play with his ſiſter while ſhe was under inoculation, and from her he received the diſeaſe, of which he died. Were the vaccine inoculation to be followed with a ſimilar event, it is highly probable, that without adverting to the cauſe, it would be brought forward as a proof that the Cow-pox has not the power of preventing the Small-pox; and conſidering that of late the new inoculation has been very generally practiſed, I am ſurpriſed that evidence againſt it of this deſcription has not yet been brought before the public.

The time at which the Cow-pox affects the [40]conſtitution after the virus has been applied, appears to be differently ſtated by inoculators: according to my obſervations it correſponds nearly to that of the variolous inoculation: however, it not unfrequently happens, that a raſh takes place as ſoon as the local action of the infectious matter becomes evident. The effloreſcence at the inoculated part which ſel⯑dom ſupervenes before the eighth, or latter than the eleventh day, is to be regarded as an indicacation that the whole ſyſtem is affected; and if the patient has not felt any indiſpoſition on or before its approach, he may be aſſured that there will not be any afterwards. When the effloreſcence does not commence till the eleventh day, it is almoſt always attended with more indiſpoſition than when it occurs on the eighth or ninth day. The effloreſ⯑cence is more frequent in young infants than to children advanced to three or four years of [41]age, and the former have the effloreſcence ſooner, and the diſeaſe more favourably than the latter, inſomuch that by far the greater part of them have no perceptible illneſs, and require no medicines. On the other hand, in adults, the Cow-pox frequently produces head-ache, pain of the limbs, and other febrile ſymptoms, for two or three days, which are greatly relieved by a briſk purgative.

After the local tumour has advanced ſo far as to become a dry ſcab, a few ſcattered papu⯑lous, or puſtular eruptions, ſometimes appear: theſe however are ſeldom of long continuance, and the puſtules rarely ſuppurate, but when they do, the pus they contain is capable of producing the diſeaſe by inoculation. I have inoculated ſome children for the Cow-pox, whoſe parents have been deſirous that two or three variolous-like puſtules, ſhould be pro⯑duced, which I have generally, though not [42]always, been able to accompliſh, by taking a little of the vaccine matter from the inocu⯑lated part upon a needle, and with it making a ſlight puncture in thoſe parts where it was wiſhed the puſtules ſhould appear. This ſhould be done about the eighth or ninth day, or when the effloreſcence commences. If recent variolous matter be uſed inſtead of the vaccine, the effect will be the ſame. With regard to the appearance of puſtules from the vaccine inoculation, I ſhall extract the following communication by Dr. Pearſon, which clearly ſhews, that Dr. Jenner's opinion upon this ſub⯑ject is contradicted by facts:—‘"1. In a perſon inoculated by Dr. Jenner, in the country, who came to town, and was under the care of Mr. Cotton,"’ ‘"the eruptions bore much reſemblance to the inoculated Small-pox, in number from twelve to twenty."’ See Mr. Cotton's letter to Dr. Pearſon.—‘"2. No [43]one has been more active and ſucceſsful than Mr. Ring; this gentleman, whoſe experience I know has been very extenſive, could not avoid eruptive caſes, although he got matter with great pains, from different ſources."’ ‘"I have,"’ ſays Mr. Ring, in his letter to Dr. Pearſon, ‘"inoculated thirty patients, with matter given to me by Mr. Paytherus, and to him, by Jenner. One of theſe had about 150 puſtules; theſe were not diſtinguiſhable from variolous ones, by any diagnoſtics with which I am acquainted. The matter was purulent; became perfectly opaque, and on exſiccation, formed a ſcab as large as that left by the Small-pox."’ Was the virus uſed in theſe caſes pure and uncontaminated?^*