combination. If the proportion of cxygen be increased to 37 parts in the hundred, a gas or vapour is formed, which was termed by Dr. Priestley depblogificated nitrous air, but by Dr. Mitchill, gafous oxyd of fepton, or feptic oxyd. This is eipecially the compound, which Dr. M. confiders as acting the most confpicuous part in contagions and peftilential affections; in other words, as the principle of contagion itself.

If fepion (azote) be united with a ftill greater proportion of oxygen, it forms feptic gas (nitrous air or gas). This air, united with water, forms the fuming nitrous acid, or aqua fortis of the fhops; it attracts oxygen greedily from the furrounding air, and, when faturated with this principle, is the feptic or nitric acid. There are the only combinations of fepton and oxygen which are diftin&tly known, although Dr. Mitchill fuppofes they are capable of combination in every poffible proportion; and that the varieties of contagions may thus be explained and accounted for *.

It would be unphilofophical to infer a lameness of properties in any two bodies, becaufe they contained the fame principles; for they may be fo differently combined, as to produce different and even opposite effects. Thus, for example, a mixture of oxygen and hydrogen aus forms a compound which is highly combustible and explofive; but if the electric fpark be made to pass through them, or they be inflamed together, they immediately lofe their aerial form, and are converted into water, equal precifely in weight to the airs from which it was produced. Although, therefore, Dr. Mitchill had attributed peltilential properties to that combination of fepton with oxveen, which he terms the gafcous oxyd fpion (depblog ifticated nitrous air), he might not neceflarily conclude the other feptic compounds which have been mentioned to poffefs analogous effects: yet this, he and his followers actually do. Thus, he observes in his addrefs to the Legiflature of New York, when employed as counted for the foap-boilers and tallow. chandlers of that city, whofe occupations had been fuppofed to increafe, if not to produce, the peftilential ftate of the atmofphere: "Peftilential air is nitrous gas (jeptic gas), faturated with oxygen,

and volatilized by heat; that is to fay, the fame fort of fluid which is produced in Eudiometrical Experiments." Many other pallages in Dr. Mitchill's writings might be adduced, to fhew that he attributed peftilential properties to the dif ferent compounds of fepton and oxygen, and that they differed merely in degree of power, from the feptous oxyd, to the moft concentrated, the nitric or feptic acid.

This acid principle, which is confidered by Dr. Mitchill as the matter of contagion and peftilence, it is well known, is furnished by animal matters whilft undergoing putrefaction. To putrefaction, therefore, he, in common with many others, refers the fource of contagious and peftilential difeafes. This opinion, it must be acknowledged, is by no means devoid of probability. When men are crowded together for a length of time within a narrow space, and cleanliness and ventilation are neglected, disorders arife, and a poifon is generated, which, when applied to the bodies of perfons in health, excites in them the fame affection, with the fame power of generating anew the infectious principle. In this way, the contagious difeafes known under the denomination of hofpital, jail, and ship fever, are produced. As the fame circumftances occur in the habitations of the poor, efpecially during the winter feafon, when a defire of warmth leads to the exclufion of fresh air, fo in thefe a fimilar difeafe is generated, with a similar infectious power, and is called low, nervous, putrid, or typhous fever. In hot climates, the plague or peftilence feems to be produced in much the fame way. In all the fituations mentioned, animal exhalations and impurities are accumulated; and putrefaction, to which all animal matters are prone, is of neceffity continually going on.

In marthy fituations, again, efpecially in tropical climates, vapours arife, and are conveyed to fome distance, which affect the bodies of men with many virulent diforders, as dyfentery and fevers. The poifon thus ariling has been termed marjb effluvia, or miafmata, produced by the decay and decompofition of vegetable, and perhaps animal, matters.

As, then, putrefaction is fo often prefent in the fituations here enumerated, it

was

was very natural to look to this, as the immediate fource of the diforders in queftion, and to conclude the infectious matter which was produced to be of a putrid nature. This opinion has not only been adopted by Dr. Mitchill, but has been very generally entertained among

mankind.

A material difference, how ever, exists with regard to the particular principle evolved during putrefaction, fuppofed to produce the deleterious effects.

By putrefaction, bodies are refolved into their component elements, and new combinations between thefe take place. By far the greatest part of the putrifying body is diffipated in the furrounding air, in the form of invifible and elaític va. pours; a fmall portion only of earthy matter remaining behind. Thus, for inftance, there are extricated from a putrefying mafs ammoniacal air, or the volatile alkali in the fate of vapour; bydrogene, or inflammable air, either fimple or holding in folution charcoal, fulphur, or phofphorus: there are the fubftances which afford the ftrong and offenfive odours that exhale from bodies in a putrefying ftate. They are all alkaline in their nature, and therefore deftructible by acids; and are the matters which, for the most part, have been fuppofed to afford the infectious principle. According to Dr. Mitchill's hypothefis, however, it is that other product of putrefaction, the combination of fepton with oxygen (the feptic oxyd or acid), which affords the contagious principle; and which, being acid in its nature, calls for means to deftroy it di. rectly the reverse of the former.

With this idea of the nature of contagion, Dr. Mitchill is led to reject all those means which have been hitherto commonly employed for its deftruction, and which are of an acid kind; fuch as vinegar and its fumes, but more efpecially the vapour difengaged from nitre by the action of the vitriolic acid, according to the procefs recommended by Dr. Carmichael Smyth, and employed by him and others for the deftruction of contagion, with at least apparent fuccefs. The acid vapour thus let loofe, is confidered by Dr. M. as not only nugatory and unavailing, but as furnithing the very principle of contagion itfelf. In place of this, he advifes the ufe of lime

and alkaline fubftances in general, with the view of neutralizing the fuppofed acid principle, and thus of deftroying its deleterious properties.

In order to induce us to adopt the idea that any one of the principles given out in putrefaction is the immediate caufe of contagious or peftilential difeafes, it fhould he fhewn that contagion and putrefaction are much more clofely allied than we find to be actually the cale. Putrefaction exifts in innumerable fituations; and men are immerfed, more or lefs, in putrid vapours, without having fever induced in them. Slaughter-houtes, tan-yards, catgut-manufactories, graveyards, and various others, abounding in putrid exhalations, exift, without producing contagion. Nor can it be faid, that perfons employed in fuch fituations are rendered, by habit, infenfible to their effects; for it has not been shewn that they are lefs open to the action of contagion otherwife excited: nor is the vicinity of fuch fituations more infefted by contagious diforders, than others where putridity is lefs obferved, fhort, putrefaction is fo often prefent without contagion and, on the other hand, contagion is fo often unaccompanied by any putrefaction obvious to the fenfes, that it is exceedingly difficult to imagine any immediate connection between the two, or that one is the direct confequence of the other.

In

But even admiting that contagion were the direct effect of putrefaction, it would in no wife explain the further propagation of infection from ore fubject to another. Suppofe a man to be placed in the midst of putrefying bodies, and a contagious fever fhould arife, if he were removed to another fituation, where no putrefaction was going on, he would ftill be capable of communicating infection to another, and this to a third, and fo on. But this could not be on the hypothefis of Dr. Mitchill; for there is often no appearance of putrefaction going on in or about a person so diseated. Indeed Dr. M. exprefsly fays, that the feptic acid, though the product of putrefaction, is at the fame time a powerful preventive of it: "fuch fubftances as are feptic in their origin, are antifeptic in their effects." The caufe of contagion, therefore, must be fomething different from putridity.

With respect to the fuppofition of the feptic acid, or its modifications, being the principle of contagion, facts are still more against it. We can produce by art all the feptic compounds which are accufed as conftituting this poisonous principle, and can apply them in various ways to the human body: indeed they are daily and hourly fo applied, in a number of proceffes in the arts; yet it has never till now been fufpected that they gave birth to contagion. The feptic (nitric) acid has of late been employed in medicine to a great extent; both internally and outwardly applied. In the laboratory of the chemift, the feptic acid is often afloat in all its modi fications. In nitre-works, the fame thing takes place: the feptic vapours must continually be applied to the lungs and furface of the body, without being influenced by the fixed alkali employed in the process. In none of thefe has it been fhewn that contagion exerts its deadly influence more than in other fituations; nor has it been found, that the fumigating process of Dr. Carmichael Smyth, above alluded to, has given increafed energy to the contagion on board of fhips, or in hofpitals, where it has been employed. On the contrary, there is all the evidence which can be had, that thefe very fumes operated to the deftruction of the contagion which before exifted. When the fumigating procefs was begun, a fever of a mott malignant kind was making dreadful ravages, attacking almost all that came within its influence in rapid fucceffion. A few days employment, however, of the fumigation fufficed to check its progrefs; and in a fhort time it fubfided altogether.

Laftly, the gafcous oxyd of fepton, that compound of fepton and oxygen, which Dr. Mitchill fuppofes to act the most confpicuous part, in cafes of peftilence and contagion, has of late been proved to be harmlefs, when inhaled into the lungs; and even to fupport animal life longer, and to give greater vigour to the fyftem, than atmospheric air itself*.

If the queftion be taken in another view, and the effects of lime and alkalies, which Dr. Mitchill fuppofes to be the antidotes of contagion, be looked to, we fhall find nothing, I apprehend, on which to fupport his hypothefis. He was, doubtles, well employed in averting, by unanfwerable arguments, the public odium from a particular clafs of manu. facturers in the city of New York, who had been ftigmatized by public authority as giving birth, by their occupa tions, to noxious and peftilential vapours. He adduced very fufficient evidence to fhew, that the foap-boilers and tallowchandlers had no fhare in the generation of the prevailing peftilence. But his arguments go no further. The matter of contagion is probably deftructible by both acids and alkalies, and is not neceffarily, therefore, either one or the other but a certain fomething, generated in the living proceffes of the animal fyftem, of the intimate nature of which, as well as of the matter fo produced, we shall ever perhaps remain ignorant. It is at leaft certain, that no good purpofe can be answered by assuming a knowledge of it on infufficient grounds. (To be continued.)

THIS in Went of HIS beautiful place is fituated

Tame, and about eight miles Eaft from Oxford. It belonged anciently to the Quatermans, and to the Veres, Earls of Oxford. Both Great and Little Ricot were, in the reign of Henry VIII. purcafed of Giles Heron, of Shacklewell (who had bought them of Sir Richard

whose daughter carried them in Fowler), by John Lord Williams, of

marriage to Henry Lord Norris. They afterwards went by marriage to Montague, Earl of Lindfey, whole fon, James Earl of Abingdon, inherited her estate here; and from him it descended to the prefent Earl.

MACK.