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cafual small-pox; and I copioufly impregnated with it, balls of cotzon, lint, wool, and filk. This operation, repeated during a whole week, morning, noon, and night, for an hour at each fitting, produced no effect,

I then fent away the children, defiring the parents to acquaint me, in cafe any indifpofition appeared, and to bring them to me a fortnight afterwards, although no alteration fhould have taken place in their health. I declare that, not only for that term, but for many fucceeding months, during which I took care frequently to visit them, they all enjoyed perfect health. It was not till nine months after this time that four of these children had a mild kind of fmall-pox.

Having concluded from thefe experiments, that the children could not have escaped infection, but because the variolous matter might have loft that spring and that degree of energy, which, perhaps, it may poffefs, on arifing immediately from the human body, I placed a perfon in the eruptive fever of the fmall-pox by inoculation, at the diftance of about half a yard from four children properly prepared; each expofure continued one hour, and was repeated daily for a fortnight, reckoning from the commencement of the fever till the puftules were become perfectly dry: not one of the four received infection. Two months afterwards, I inoculated three of thefe children; they had the diftemper in a very mild manner and recovered without difficulty.

Like experiments made with the blood, and with flimy matter which runs from the eyes and nose of perfons attacked by the meafles have uniformly had the fame refult.'

Dr. Paulet, it is remarked, has gone further, and contends. that the poifon is never communicated by the air alone. But we fufpect that either hypothefis is untenable. If there is not fomething peculiar, at times, in the conftitution of the air, or the habits of patients, why should infection be lefs eafily com municated at fome periods than at others? If the infection may not exist in the conftitution, without producing the dif cafe, why fhould terror, caufes of debility, or depreffing palfions, immediately produce it? The difeaie is a fpecific one: these causes are only general, and the effect is immediate. The fame effects follow fimilar caufes in other epidemics, and the confequence is always the peculiar difcafe of the period, whether it be plague, fmall pox, measles, or nervous fever. Thefe are facts obferved at different times at various places, by different practitioners; nor can we fee how they can poffi bly be eluded. They ftrike then at the root of every obferva tion of this kind, and ought not to be allowed a moment's attention, as they would inspire a delufive fecurity. It must be added, that, in various parts of the correfpondence, the facts are in oppofition, and a practitioner, Dr. Waterhouse, is at

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variance

variance with himfelf. We fhall, at a future period, notice Dr. Haygarth's diftinction between pofitive and negative facts, but, on this occafion, we muft fay, that one pofitive fact is of more confequence than ten negative ones. If a perfon has been expofed to caufes of infection, which ever have produced the difeafe, and fuffers from them, it is of more importance than if ten fhould escape in the fame circumftances. Damp fheets, for inftance, produce cold and fever; yet many have lain in them with impunity. Shall we, therefore, with Dr. Heberden, fay that they are not injurious? In the cafes adduced by Dr. Waterhouse, the wind blew across a wide channel, from the fmall-pox hofpital: thofe, in its direction were only affected, and eight of ten had the disease. Had one or two been affected, it might have been accidental, but that eight of ten fhould be fo, without having been exposed to infection from another fource, is incredible, if this caufe, though highly improbable in its firft appearance, fhould not be admitted. Again, the gentleman, who had ridden two miles in the air, communicated the disease to his daughter, to whom he talked at an open window. This story is treated too lightly, The air might have been still; and, while talking to her, an artificial draught of air might have been occafioned by a door being open oppofite the window. If there was no other means of her being infected, the ftory ought at all events to keep praçtitioners on their guard.

The arguments, by which thefe facts are obviated, reft on a ground the most uncertain, the nature of the variolous poifon. It appears, fays the author, in the form of pus, of other fluids, and of gas. On the contrary, there is not a fine gle fact to fhow what is its proper form; not an argument to prove that it is diffolved by air, or that, in confequence of folution, it is rendered harmlefs. Inftead of being pus, the infecious matter is only combined with pus, for it exifts equally in the watery fluid of the early puftule. It exifts in the air, though we know not whether in a state of combination, or, like fome bodies, whofe feparate particles may be diffused and again collected; nor is it poffible from our prefent experience to fay, whether it is rendered effete by folution or by diffufior. Such is our ignorance on this fubject, that no argument against any fact can be adduced from theoretical confiderations; and it is the most exceptionable part of the prefent work, that fo much dependance is placed on reafoning, ref pecting the nature of the virus. In this point we are not fingular. Dr. Aikin's letter is very explicit on this part of the Subject:

You may remember that I was never thoroughly fatisf.ed with

your

your theory of the folution of variolous miafmata in the air, and the conclufions you deduce from it. I fee clearly the importance of this doctrine in laying down rules of prevention; but in a practical matter of fo much confequence, I think it too hazardous to build upon a foundation of theory, unless perfectly demonftrated. I have just been reading over the chemical part of your Inquiry, along with my intelligent friend Mr. Morgan, whom I connder as deep in chemical knowledge; and he is fill lefs convinced than myself with your reasoning on this head. He looks upon the teft of transparency, as altogether inapplicable to particles of fuch extreme tenuity; and he thinks that even admitting the probability of the folution of thefe particles in air, the power of the air as a menftruum would be greatly affected by various circumftances, fuch as heat, moisture, and the like, which would much impair your conclufions. The doctrine of affinities is known to admit of many exceptions from thefe caufes, fo that, in certain circumflances, a body flail frequently take from another a third with which it has on the whole lefs alliance. Then to come to analogy, we cannot but think that the facts in oppofition to your doctrine, which you fo fairly ftate, (p. 69.) are really, upon the whole, decitive against you. Thus, the remark in p. 71, concerning clothes acquiring the fimell of tobacco, is certainly not anfwered by fuppofing that fone: fmoke (after a whole night) might remain in a diffused state; or that the perfons might get fome foot upon him, which foot, you will obferve, refults from a decompofition of the tobacco, and therefore probably would not fmell like it. In the cafe of woollen clothes becoming damp in a moist air, it is certain that they will do fo in air which to the fight does not fhew diffusion of the watery particles. Mr. Howard's obfervation feems point biank against your opinion; for fuppofing a room equally fuperfaturated by variolous particles, why might they not be equally depofited upon clothes, papers, &c. The fact of clothes tainted by a privy, is equally to the purpofe; for I am certain that this happens where nothing more vifibie arifes from thence, than from a fmall-pox patient. With refpect to musk, it is alfo furely not fufficient to fay that its effluvia are poflibly different from all others; for it is an animal fubftance; and at any rate its effluvia are invisible, and yet taint clothes. It seems to me merely that the impregnation is here more perceptible on account of its furonger odour. On the whole, these analogies ftrike me to firongly, that I should fcarcely doubt that the bed-curtains of a fail-pox patient, who had the disease feverely, though not actually tainted with the matter, would yet imbibe miafmata fufficient to infect a perfon to whom they were directly taken without ventilation. And if this extreme cafe be true, it will follow that the danger of infection from clothes in all others will be in a ratio of the degree of original impregnation, and fubfequent ventilation; and that no abfolute line can be drawn, though, I think, rules fufficient for practice might be devif

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ed.

To be perfectly explicit, then, as to your main queftion, refpecting the fufficiency of the preventive rule, I fhall go a step forther than your medical correfpondent in p. 81, and fay, "that ar the theory that contagion cannot be conveyed by clothes, &c. of attendants, appears to me not clearly established, I think the rules defective in fo much as they do not provide for fuch a poffibility."

In candour, we might be expected to produce the answer; but it is wholly hypothetical. The variolous matter has never been feen feparate; and to apply the doctrines of elective attraction to this fubject, the affinities of this matter should be known. Even fulphur becomes invifible in the form of hepatic air: camphor, affa foetida, mufk, tobacco, the volatile oil of excrementitious fubftances, do not difturb the transparency of the air, yet they are diffufed and depofited. To avoid cavil, we fhall add, that we confider the air to be transparent, when objects are feen through it with their ufual clearness; ftrictly speaking, the air is never tranfparent, but when faturated with water in the moment of feparating into distinct drops. The miafma may therefore exift, and appear only in a gilded fream of air, like motes, without difturbing the geperal transparency of the atmosphere.

If, from varicus circumftances, we were to fix on the state of air moft favourable to the propagation of infection, we hould fay it is moist, foggy, warm air; and this fact is favourable to the theory of folution, but the principle is not fufficiently established to reft on it a theoretical confequence, The facts, for instance, which shows that infection is difficult during the drynefs of the Harmattan, thofe of profeffor Wa▾ terhouse, which fhow an unexpected facility in its propagation in foggy weather; thofe which prove, that the infection is not impaired in its power by being kept in a dry state, all contribute to eftablish this idea. Yet, admitting for a moment, the folution, while the affinity of the poifon is unknown, we dare not say, that a change in the folvent power of the air may not again precipitate it. And, in the midst of all thefe difficulties, thefe uncertainties, arguing in our present uninformed ftate, from fuppofition, we are called on to apply our doctrines to practice, while facts we think clearly established, thofe mentioned in our former article, and repeated in the beginning of this, are forced to yield to gratuitous hypothefes, incapable, perhaps, of being brought to the teft of experi

ment.

Profeffor Waterhoufe's correfpondence we confider as particularly valuable. We are fully convinced, from what we have feen and read, that the fmail-pox may be conveyed by cloaths, though there may be many times when cloaths, moft

fully

fully impregnated, do not propagate the infection. The dif tance to which it may be conveyed is certainly not known; nor can it be ascertained, till the nature of the infectious mat ter is better understood. The effluvia from burning the infected cloaths, have communicated difeafe; nor ought we to deny that burning them cannot deprive them of the miafmata, while we know it will deprive putrid meat of its feptic par

ticles.

In the Reply, Dr. Haygarth infifts on the fuperior efficacy of negative proofs. If, in given circumftances of infection, no difeafe is communicated, it is a negative proof that no infection exifted: where it was communicated, therefore, fome other caufe must be fought. Yet, in the cafes alluded to, the probability is, that no infection would be conveyed, confequently one pofitive fact is more than equivalent to fifty negative arguments. The difference between us, refts wholly on the degree of the caufe. Where the power is great, the negative argument holds: where it is inconfiderable, it fails. The damp fheets form a cafe in point: ten efcape, but we ought not to conclude that they are harmless. Medical men fcarcely ever convey the infection which, from the time of their stay with the patient, muft adhere flightly: but we ought not to conclude, that they are incapable of ever doing fo.

In Dr. Clark's correfpondence, there are fome facts of importance. He feems to think, and it is highly probable that, during the eruption, patients do not communicate the infec tion, even in the clofeft contact. This we confider well esta blifhed as a fact; but every fact on this fubject is too uncer tain to be depended on in every inftance, or at least to infpire implicit confidence. Dr. Clark never fuffers his cloaths to touch the patient, and washes his hands after visiting them, He never conveyed the infection; but many practitioners cant fay the fame, who have never employed either precaution. Other difeafes he feems to think have been conveyed by the cloaths; but, of thefe, the communication of dyfentery is the moft probable. The eruptive fever has, he finds, been fufpended beyond the fourteenth day. On this part of the fubject we fhall take the prefent occafion to obferve, that though, in fome inftances, in fome probably occurring at the fame time, the infection from the natural finail-pox has been apparently more quick than from inoculation, yet, in general, the common pofition is established from thefe volumes, that, in the greater number of inftances, inoculation would fuperfede the natural infection.

Dr. Odier's correfpondence is very valuable. He confirms the opinion, that confinement after inoculation, and even during the firft eruption, is unneceflory, as patients are then

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