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

• I then sent away the children, desiring the parents to acquaint me, in case 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 succeeding 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 small-pox.

• Having concluded from these experiments, that the children could not have escaped infection, but because the variolous matter might have lost that spring and that degree of energy, which, ferhaps, it may possess, on arising immediately from the human body, I placed a person in the eruptive fever of the small-pox by inocuilation, at the diftance of about half a yard from four children properly prepared; each exposure continued one hour, and was repeated daily for a fortnight, reckoning from the commencement of the fever till the pustules were become perfectly dry: not one of the four received infection. Two months afterwards, I inoculated three of these children; they had the distemper in a very mild manner and recovered without difficulty.

"Like experiments made with the blood, and with simy matter which runs from the eyes and nose of persons attacked by the mcalles have uniformly had the same result.?"

Dr. Paulet, it is remarked, has gone further, and contends that the poison is never communicated by the air alone. But we suspect that either hypothesis is untenable. If there is not something peculiar, at times, in the conftitution of the air, or the habits of patients, why should infection be less calily communicated at some periods than at others? If the infection may not exist in the constitution, without producing the site case, why should terror, causes of debility, or depreting palfions, immediately produce it? The disease is a specific onc : these causes are only general, and the eileet is immediate. The same effects follow similar causes in other epidemics, and the consequence is always the peculiar disease of the period, whether it be plague, small pox, measles, or nervous fever.

These are facts obierved at different times at various places, by different practitioners; nor can we see how they can pollibly be eluded. They ítrike then at the root of erery obkrva.' tion of this kind, and ought not to be allowed a moment's ata tention, as they would inipire a delusive security. It must be added, that, in various parts of the correspondence, the facts are in opposition, and a practitioner, Dr. Waterhouse, is at 'D 3

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variance with himself. We shall, at a future period, notice Dr. Haygarth's distinction between positive and negative facts, but, on this occasion, we must say, that one positive fact is of more consequence than ten negative ones. If a person has been exposed to causes of infection, which ever have produced the disease, and suffers from them, it is of more importance than if ten should escape in the same circumstances. Damp thecis, for in{tance, produce cold and fever; yet many have lain in them with impunity. Shall we, therefore, with Dr. Heberden, say that they are not injurious? In the cases adduced by Dr. Waterhouse, the wind blew across a wide channel, from the small-pox hofpital: those, in its direction were only affected, and eight of ten had the disease. Had one or two been af fected, it might have been accidental, but that eight of ten shouid be so, without having been exposed to infection from another source, is incredible, if this cause, though highly im. probable in its first appearance, should 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 ai. open window. This story is treated too lightly, The air might have been still; and, while talking to her, an artisi, cial draught of air might have been occasioned by a door being open opposite the window. If there was no other means of her being infected, the story ought at all events to keep practitioners on their guard. .

'I he arguments, by which these facts are obviated, rest on a ground the most uncertain, the nature of the variolous poion. It appears, says the author, in the form of pus, of other fluids, and of gas. On the contrary, there is not a fine gle fact to show what is its proper form ; not an argument ta prove that it is dissolved by air, or that, in consequence of fo. Jution, it is rendered harmless. Instead of being pus, the ina fectious matter is only combined with pus, for it exists 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 lome bodies, whose separate particles may be diffused and again collected; nor is it possible from our prefent experience to say, whether it is rendered effæte by solution or by diffufior. Such is our ignorance on this subject, that no argument againit any fact can be adduced from theoretical confidera. tion: ; and it is the rooft exceptionable part of the present work, that so much dependance is placed on reasoning, respeeling the nature of the virus. In this point we are not fin. gular. Dr. Aikin's letter is very explicit on this part of the subject : You may remember that I was never thoroughly satisf.ed with

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vour theory of the solution of variclous miasmata in the air, and the conclufions you deduce from it. I see clesriy the importance of this doctrine in laying down rules of prevention; but in a greetiçal matter of fo much consequence, I think it too hazardo!is to build upon a foundation of theory, unless perfectly demonstrated. I have just been reading over the chemical part of your inquiry, along with my intelligent friend Mr. Morya:), whom I congder as deep in chemical knowledge; and he is will lels convinced than myfclf with your reasoning on this head. He looks upon the test of trunjarency, as altogether inapplicable to particles of such extrenie tenuity; and he thinks that even adinitting the probability of the folution of these particles in air, the power of the air as a menftmum would be greatly affected by Farious circumftances, such as heat, nioitur, and the like, which would much impair your conclufions. The doctrine of affinities is known to admit of many excerxiutts from these causes, so that, in certain circumstances, a body full frequently take from another a third with which it has on the whole less al. liance. Then to come to analogy, we cannot but think that the faits in opposition to your doctrine, which you fo fairly ftute, (p). 69.) are really, upon the whole, decitive iguint von. Thus, the reinark in p. 71, concerning clothes acquiring the firell of tobacco, is certainly not ansivered by furtofing that lonr: smoke (afer a whole night) might remain in a diffuted state ; or that the perfons miglit get some foot upon him, which foot, you will observe, refults from a decompolition of the tobacco, and therefore probably would not (mell like it. In the case of woollen clothes becomirg dan p in a moif air, it is certain that they will do so in air which to the fisht does not shew diffusion of the watery particles. Mr. Howard's observation seems point blank against your opiniou ; for fuppolirg a soom equally supersaturated by variolous particies, why night they not be equally deposited upon clothes, papers, &c. The fact of clothes tainted by a privy, is equally to the purpose; for I am certain that this happens where nothing more ciifbie arises from thence, than from a small-pox patient. With respect to musk, it is also Surely not fufficient to say that its effluvia are poflìbly different bom all others; for it is an animal substance; and at any rate its estuvia are ixvibble, and yet toint clothes. It teems to me nerely that the impregnation is here njore perceptible on account of its stronger odour. On the whole, these analogies strike me so strongly, that I Thould scarcely doubt that the bed-curtains of a {mail-pox patient, who had the disease feverely, though not actually tainted with the matter, would yet imbibe miasmata fufhcient to insect a person to whom they were direfliy taken without ventilation. And if this excreme case 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 imprego nation, and subsequent ventilation; and that no ablolute line can be drawn, though, I think, rules sufficient for practice might be devis

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ed. To be perfe&tly explicit, then, as to your main question, respecting the sufficiency of the preventive rule, I shall go a step further than your medical correspondent in p. 81, and say, “ that as the theory that contagion cannot be conveyed by clothes, &c. of attendants, appears to me not clearly established, I think the rules defective in so much as they do not provide for such a possibility.”

In candour, we might be expected to produce the answer; but it is wholly hypothetical. The variolous matter has never been seen separate; and to apply the doctrines of elective attraction to this fubject, the affinities of this matter should be known. Even sulphur becomes invisible in the form of hepatic air: camphor, asfa fætida, mulk, tobaccy, the volatile oil of excrementitious substances, do not disturb the transparency of the air, yet they are diffused and deposited. To avoid cavil, we shall add, that we consider the air to be transparent, when objects are seen through it with their usual clearness :

trictly speaking, the air is never transparent, but when saturated with water in the moment of separating into distinct drops. The miasma may therefore exist, and appear only in a gilded stream of air, like motes, without disturbing the general transparency of the atmosphere.

If, from varicus circumstances, we were to fix on the state of air most favourable to the propagation of infection, we should lay it is moist, foggy, warm air; and this fact is favourable to the theory of folution, but the principle is not suf. ficiently established to rest on it a theoretical consequence, The facts, for instance, which shows that infection is difficult during the dryness of the Harmattan, those of professor Wa. terhouse, which show an unexpected facility in its propagation in foggy weather; those which prove, that the infection is not impaired in its power by being kept in a dry state, all contribute to establish this idea. Yet, admitting for a moment, the solution, while the affinity of the poison is unknown, we dare not say, that a change in the solvent power of the air may not again precipitate it. - And, in the midst of all these difficulties, these uncertainties, arguing in our present uninformeil state, from supposition, we are called on to apply our doctrines to practice, while facts we think clearly established, those mentioned in our former article, and repeated in the beginning of this, are forced to yield to gratuitous hypotheses, incapable, perhaps, of being brought to the test of experiment.

Profeffor Waterhouse's correspondence we consider as par. ticularly valuable. We are fully convinced, from what we liave seen and read, that the small-pox may be conveyed by cloaths, though there may be many times when cloaths, molt

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fully impregnated, do not propagate the infection. The dir. 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 esuvia from burning the infected cloachs, have communicated disease; nor ought we to deny that burning them cannot deprive them of the miasmata, while we know it will deprive putrid meat of its feptic particles.

In the Reply, Dr. Haygarth insists on the superior efficacy of negative proofs. If, in given circumstances of infection, no dilease is communicated, it is a negative proof that no infection existed: where it was communicated, therefore, fome other cause must be fought. Yet, in the cases alluded to, the probability is, that no infection would be conveyed, confequent ly one positive fact is more than equivalent to fifty negative arguments. The difference between us, rests wholly on the degree of the cause. Where the power is great, the negative argument holds: where it is inconsiderable, it fails. The damp sheets form a case in point: ten escape, but we ought not to conclude that they are harmless. Medical men scarce. ly ever convey the infection which, from the time of their stay with the patient, must adhere slightly: but we ought not to conclude, that they are incapable of ever doing so.

In Dr. Clark's correspondence, there are some facts of im. portance. He seems to think, and it is highly probable that; during the eruption, patients do not communicate the infection, even in the closet contact. This we consider well esta, blished as a fact; but every fact on this subject is too uncer. tain to be depended on in every instance, or at lealt to inspire implicit confidence. Dr. Clark never suffers his cloaths to touch the patient, and washes his hands after viñting them, He never conveyed the infeétion; but many practitioners cati say the same, who have never employed either precaution, Other diseases he seems to think have been conveyed by the cloaths; but, of these, the communication of dysentery is the most probable. The eruptive fever has, he finds, been sufpended beyond the fourteenth day. On this part of the sub. ject we shall take the present occasion to obferve, that though, in some instances, in some probably occurring at the same time, the infection from the natural (mail-pox has been apparently more quick than from inoculation, yet, in general, the common position is established from these volumes, that, in the greater number of instances, inoculation would supersede the natural infetion.

Dr. Odier's correspondence is very valuable. He confirms the opinion, that confinemeut after inoculation, and ever during the first eruptior, is una cutiry, as patients are then

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