SURGEON GENERAL'S OFFICE % UBRARY. V J (J Section, ■*• JVo. hj^Xddmm / \ REMARKS ON THE GASEOUS OXYD O F AZOTE OR OF NITROGENE, AND ON THE EFFECTS IT PRODUCES WHEN GENERATED IN THE STOMACH, INW$L$D INTO THE LUNGS, AND APPLIED^*',, "\ TO THE SKIN : / /""" \J / \>v BEING \v A ' ' -£. AN ATTEMPT ''; ^ 'TO ASCERTAIN THE TRUE NATURE >. V; AND TO EXPLAIN THEREUPON THE PHENOMENA OF FEVER. ,y / —-—tr~ By Samuel Latham Mitchill,m.d.f.r.s.e. Profeflbr of Chemiftry, Natural Hiftory and Agriculture in the College of New-York. NEfT-YORK: Printed by T.and J. Swords, Printers to the Faculty of Phyfic of Columbia College. — i 795— PREFACE. 1 7* has a long time appeared to me highly pro- bable, that contagion was an aeriform fluid, produced occajionally, and exerc'ifing for afea- fon its deflruclive effecls. Since my appoint- ment to the Profejfbrflip of Chemiftry in the College ofNew-Tork, my mind has been parti- cularly engaged in acquiring as full a knowledge as I could of the gaffes. In the courfe of my experiments and inquiries, I have become fatif- fied my original conjecture was right; and I have to acknowledge the pneumatic philofophy has led the way to an elucidation of this hitherto dark and intricate fubjecl. The combination of thebafe of vital ahzvith the radical of nitrous acid forms a compound which, though little known, pojfeffcs very remarkable qualities. If A 2 the ( 4 ) the principles laid down in the following pages are true, a confiderable number of interejiing deductions maybe drawn from them, both in the theory and practice of phyfie, and in relation to health offices and the means to be adopted for guarding againjl infectious diflempers. Under theperfuafion, that the mode of confidcring this fuhjccl is novel, the performance is fubmitted to the confideration of the public. Afy fellow citizens, for whom it was written, will learn hoiv much the prefervaticn of health is in their own power. Plandame, Auguft 20, 1795. REMARKS REMARKS ON THE Gafeous Oxyd of Azote, &c. JL HIS is the air mentioned by PriefHey (ii. Exp. & Obf. 54, &c.) under the title of Dephlo- gifticated Nitrous Air.. He difcovered it by ex- pofing nitrous gas to iron, whereby that aeri- form fluid was transformed in about two months to a fpecies of gas of a very remarkable kind, " which keeps up combuftion naturally and " freely in a candle immerfed in it, but is at the " fame time highly noxious to animals, and " deftroys their life the moment they are put into it:" whereas it commonly happens, that animals can live tolerably well in air fo vitiated by inflammation, that a candle will v.o longer burn in it. He obtained this air too by applying heat to a diflblution of iron in nitrous acid, after the production of nitrous gas was finifhed; in a di- rect procefs by the diflblution of zinc and tin in nitrous acid; by expofing nitrous gas to a mixture of iron filings and fulphur moifrened with water, and to hepar fulphuris; and like- wife by iron and folution of copper in the ni- trous acid. A 3 He ( 6 ) He found, that when phlogifticated air (ni- trogene or azotic gas) and dephlogifticated ni- trous air (gafeous oxyd of nitrogene or azote) were mixed together, it was an eafy matter to feparate them by means of water; for the lat- ter, by reafon of its readier mifcibility with wa- ter, will combine with that fluid in a very pure form, while the former will remain unabforbed. Prieftley's fpeculations concerning the con- fiitution of this air are attended with all the difficulty which befets the doctrine of phlogif- ton; and its true composition feems not to have been detected until fince he wrote. In the fecond number of the Recherches Phy- fico Chymiques, publifhed at Amfterdarn, an ac- count is given, which confirms the facts related by Prieftley. For this gafeous oxyd was ob- tained by expofing nitrous gas for three days over water to the action of wetted iron filings; by the fubtraction of part of the oxygene of ni- trous gas; by the moiftened fulphures of pot- afh and foda; by the muriate of tin; and by ammoniac with a bit of copper in it: it is relat- ed alfo, that folutions of iron and tin in ex- tremely diluted nitric acid, afford this gafeous oxyd, and that the nitrate of ammoniac heated after mixture with three times it quantity of fand, gives toward the end of the operation a large quantity of it. One of the moll happy difcoveries of mo- dern fcience is that of the principle of acidity cr oxygene being capacitated to afford products poffefling very different qualities, by combin- ing in greater or lefs proportion with the fame radical. ( 7 ) radical. Thus, for example, azotic or nitro- gene gas conftitutes -^th parts of our atmof- phere. Simple nitrogene, the bafe of this gas, is capable of combining with the principle of acidity as well as the matter of heat (caloric) in four diftinct proportions. Azote, in its higheft degree of oxygenation, forms nitric acid; in its next, it conftitutes nitrous acid; in a lower, ni- trous gas; and in the fourth or loweft degree"1 it affords the compound, now more particularly under confideration, the gafeous oxyd of azote, of nitrogene. We hence know, with the utmoft certainty, that oxygene, or the bafe of refpir- able air, which compofes the remaining -^th parts of the atmofphere, is in many proceffes blended with azote in various quantities.. In the gafeous oxyd, produced by the union of thefe two atmofpheric ingredients, the por- tion of the acidifying principle combined with its nitrogene bafe is too fmall to manifeft the fmalleft degree of acidity; not even fo much as to have any effect wrought upon, it by ex- pofure to liquid cauftic alkali, nor muiiated tin; and in its pure ftate undergoes no fhrink- ing, decompofition, or change, by mixture with the atmofpheric fluid, nitrous gas, or vital air. The properties of this oxyd are fo fingularand extraordinary, that Prieftley affirms, (ii. 55.) at the time of his firft publication on the Sub- ject, he fkould not have hejitated to pronounce them impoffible; to wit, a power, at the fame time, of fupporting flame, and of extinguifhing life. This furprifing quality is however doubtlefs owing to the difference.in the attractive force which ( 8 ) which its oxygene exerts for hydrogene in the one cafe, and for carbone in the other; for it is known, that by mixing the gafeous oxyd of nitrogene with carbonated hydrogene gas, the carbone is precipitated from its folution. Hence it appears, that the attraction for charcoal is much weaker than for hydrogene, and that al- though carbone may be made to burn in the ga- *-feous oxyd, hydrogene is the fubftance for which it has the clofeft affinity. And we can now readily conceive how the hydrogene of the candle may, in an efpecial manner, contribute, by attracting the principle of acidity from the gafeous oxyd, to keep up the inflammation, wherein fome part of the charcoal may like- wife, though in a fecondary way, be converted to carbonic gas. It may be underftood too, wherefore it is not capable of fuftaining life. There-are two important purpofes anfwered by animal refpiration ; the one tofurnifh oxygene to the phofphoric, fulphureous and carbonic matter of the blood; the other to carry off its furplufage of charcoal by means of the lungs. Kow the gafeous oxyd has lefs action upon phofphorus and fulphur than it has upon char- coal. Hence it is a very natural conclufion, that in ordinary breathing, the gafeous oxyd does not only not yield its principle of acidity to the blood in the pulmonic circulation, but at the fame time does not fufficiently attract carbone from the venous portion of it; whence it comes to pafs, that an animal inhaling an air, contributing to neither of thefe falubrious pro- cefles, muft fpeedily die; its blood being both in ( 9 ) in a difoxygenated and fuper-carbonated ftate; hydrogene alone being the ingredient in phlo- giftic operations which readily attracts its oxy- gen from the gafeous oxyd. The proportion of oxygene entering into gafe- ous oxyd is £b;\ the other 63 parts being nitro- gene; whereas in nitrous gas, the oxygene con- ftitutes 68 parts of the 100. On reflecting upon thefe facts, it occurred to me this fubjedt merited confideration in fe- veral other points of view : As, 1. Since this remarkable aeriform product is afforded by a variety of artificial proceffes, whether it is not generated likewife by a natu- ral operation in the decay of organized bodies, containing both nitrogene and oxygene ? The hiftory of nitre throws great light upon this query. That fubftance is known to con- fift of nitrous acid joined topot-afh. It is ufu- ally formed during the decay of animal and ve- getable bodies, and by a fpontaneous procefs, is produced from their ruins. We are quite fatisfied that azote and oxygene entered into the compofition of thofe bodies when alive, and have gone into new combinations on their difengagement by death. One of thefe recent compounds muft be nitrous acid, conftituting byjunction with a faline bafe, the nitrate of pot-afh. Thus, the theory of the formation of falt-petre neceflarily prefumes the genera- tion of nitrous acid from two of the elements difengaged from organic texture. And as azote, the radical of the acid, is efpecially abundant in animal bodies, and asLavoifier (i. Traite ele- mentaire ( xo ) mentaire deChimie, 155.) hys, favorife merveil- ieufement la putrefaflion, wonderfully promotes putrefaction, there is little difficulty in conceiv- ing, both how infuch circumftances it attracts the acidifying principle, and afterwards attaches itfelf to the alkali. But further than this, the authority of Mr. Becker (Notes to Bergman's Elective Attrac- tions, 327.) has been advanced in favour of the production of nitrous acid without the aid of the putrefactive fermentation at all. He found ni- trous-acid in the urine of cows, which had been eight days expofed to the fun. He mixed fome of thefoakings of a dunghill with a ley of burnt fheep's dung and chalk in powder. The mix- ture be^an to ferment on the following day, and on the fourth, the internal commotion hav- ing ceafed, he found at the bottom of the phial regular chryftals of prifmatic nitre. He a- fcribes the nitrous acid not to a procefs going on in the air, but brought about by the excre- tions of animals. On examining the earth of ftables and cow-houfes, he found its lixivium to yield prifmatic nitre, while that of the dung would afford only fmall chryftals, which re- quired an addition of nitre in order to be re- duced to a prifmatic form ; and he declares he can attract falt-petre at pleafure, in the courfe of three days, from the earth of ftables and cow- houfes, by ufing for faturation well-purified pot-afhes. In the production of falt-petre, the putrefied fubftance, if of the animal kind, affords little more than the nitrous acid. This was known to ( « ) IoJBoerhaave, who (i. ElementaChemie, 44.^ fays, the nitrons quality of the earth is derived from the excrements of animals and their pu- trefied carcafes, particularly fuch as do not ufe fea-falt, as birds, which, by the addition of the afhes procured from the burning of plants and of quick-lime, forms falt-petre, &c. This fact of the animal origin of the nitrous acid is confirmed by the teftimony of Macquer, (hi. Dictionaire de Chimie, 18.) who declares, that in the putrefactive procefs which affords nitrous acid, animal fubftances have a decided preference; fo that, in order to make chryftal- lizable falt-petre from fubftances purely animal, a quantity of the vegetable alkali muft be added; while the falt-petre produced in the putrefaction of vegetables alone is naturally found to be fur- nifhed with that quantity of fixed alkali which is neceffary to form good nitre. To this may be added the authority of Fotjr- croi, (ii. Lecon Elementaires, &c. 842.) who fpeaks of acidity as one of the early figns of ani- mal putrefaction; and of the proper putrid ex- halation as not to be confounded with carbonic acid, (fixed air) hydrogene gas, (inflammable air) which are at the fame time let loofe, nor with the phofphoric emanation which fometimes glows on thefurfaceof corrupting animal folids. When to all this it is fubjoined, that on ana- lizing the foil taken from the bottoms of graves where human bodies have putrefied, it has been found, though having no communication with the external air, to be highly charged with ni- trous C ** ) ffous acid, the animal origin of this acid is put entirely out of doubt. We hence fee the reafon why the French ehemifts have advifed the ufe of wood afhes to neutralize the redundant nitrous acid in their falt-petre works, and have even gone fo far as to recommend foreign pot-afh as greatly prefer- able. On this fubject, the valuable paper of Mr. Massey may be confulted in the Memoirs of the Manchefter Society, where it is made to appear, that earths become impregnated with nitrous acid during the putrefaction of animal fubftances, but will not afford a cryftalof nitre until the vegetable alkali is added.* * It is a pity, that notwithfianding all thefe things, the French Academicians who framed the new Nomenclature, fuffered themfelves to retain the words nitrous acid, nitrous gas, &c. which feem to me to be vety improper, and to be quite as fubjeft to objection as the terms azote and nitrogene, for their radical. The mind becomes unhappily impref- fed with the notion of thofe products being derived from nitre, whereas the fail is, nitre derives its origin from this animal acid. Had 1 been a mem- ber of that committee of the academy, 1 Jhould have propofed to derive the name of the radical from the Greek verb awa, putrefacio; to call it eryiflov, pu- trid u m; and have made the Nomenclature ft and'thus i 1 . '* 3 4 Septon;in- Septousgas; Gafeous oxyd of Septicgas: ftead of a- inftead of fepton; inftead of inftead zote or ni- azoticgasor gafeous oxyd of of trogene. nitrogene azote or of ni- nitrous gas. trogene. gaa. ( «3 ) In thefe feveral ways, we find nitrous acid afforded by the putrefaction of animals them- felves, and by changes in their excretions. Now, nitrous acid, differing from the gafeous oxyd, barely in the degree of oxygenation, there is no difficulty in comprehending, that if there was in any inftance afpontaneous formation of the former, there would, a fortiori, be a more eafy and frequent production of the latter. And here it happens, that the very thing which reafon feeks for, nature affords. That particular gas, defcribed by Mr. St. John (Preface to Method of Chemical Nomenclature, xi.) as produced at certain times during the putrefac- tion of human bodies in differing rooms, and as being a moft active and dreadful poifon, is, in all probability, the very aeriform product which is the fubject of this memoir. That ex- halation is not only incapable, in its concen- trated condition, of fuftaining life, but, like the gafeous oxyd, though it may be rendered lefs B injurious 5 6 7 Septous acid ; Septic acid ; Septate ; inftead of inftead of feptite, &c. nitrous acid. nitric acid. &c. and then, the original of the thing, being always fuggefted to the mind in the phrafeotogy, truth would have found a more ready reception, and nofuch diffi- culty interpofed as now befets us, prepoffeffed as we are with the notion, that the nitrous is a mineral acid. For itfJiould be remembered, that although it is obtained from nitre, a fait claffed among the mine- ral fubftances, yet it was produced by animal putre- J lclion before the nitre was formed. ( H ) injurious by dilution, does not however change its original virulence in the leaft, by the pre- fence of the atmofpherical fluids; and, like the gafeous oxyd too, it is not remarkable for any foetor or particular badnefs of fmell; both of them differing entirely from the loathfome and naufeous odour proceeding from dead bodies in a lefs dangerous ftage of corruption. The deleterious production, fo particularly mentioned by Mr. Fourcroi, in his report on the removing the Cimiterie" des Innocens at Paris, and now and then fatal to the grave- diggers, appears to be a gas of precifely the fame origin and qualities, and as in the former inftance, is generated in the abdomen. The gafeous oxyd of nitrogene in thefe in- ftances is always, as far as obfervation goes, of local origin, and feldom fpreads very far in form fufficiently condenfed to do mifchief. In large cities it is generally moft abundant, by reafon of the greater collection, along fome of their ftreets, fewers, wharfs, docks, &c. of thofe materials, which afford it, and, on account of the difficulty of ventilation, in certain lanes, yards and alleys, which allows the noxious vapour to fettle there. In few inftances that I have heard of, has it extended over a" large tract of country; in the greater number of cafes, it invades but a limited part of a large city, and that only, when a temperature of the weather, between 75 and 85° of Farenheit's fcale, favours the formation of the oxyd. When applied to a living body, frefh and ftrongon its firft formation, it produces violent inflammation inflammation and ulceration of the fingers or hand which come in contact with the body from which it proceeds; or drawn into the nof- trils, it excites alarming tumefaction, with heat and pain in the fauces and nares; or, if infpir- ed fully into the lungs, it brings on inftant death. 2dly. If the firft queftion is fatisfactorily de- cided in the affirmative, where large maffes of animal and vegetable matter, in hot feafons and confined places, undergo refolution into their conftituent parts, and form new combinations; then is it not prefumeable that gafeous oxyd may be extricated from fimilar materials by like caufes, occafionally, in the alimentary ca- nal, or prima via of human bodies while alive? For the fupport of animal life, it is neceffary that fupplies of food be, from time to time, re- ceived into the ftomach. The ingredients of diet are of the animal and vegetable kinds, and confequently contain all the materials, after their introduction into the body, that are proper to fimilar fubftances out of the body. And were it not for the mixture with faliva, gaftric liquor, pancreatic juice and gall, thefe alimen- tary matters would, from the operation of con- ftant heat and moifture, undergo putrefactive alterations in the ftomach and fmall inteftines. By the operation of thefe animal fluids, the nu- tritious part of the aliment is diflblved, and pre- pared for undergoing the procefs of animaliza- tion. For it is to be remarked, that no living thing in the perfectly healthy ftate exifts in the animal ftomach; the deftruction of life, even in B 2 oyfters, ( 16 ) oyfters, fifties, frogs, &c. fwallowed entire, be- ing a preparatory ftep to their converfion into nutriment; and worms and other animals in- fefting the guts, being enabled to live there only by poflefllng a. conftitution capable of counter- acting the digeftive procefs. Nobody has affirmed, that in the animal in- teftines, the fluids are endued with animation, any more than the aliment they contain. Our reasoning then concerning the whole contents of the firft paflages, cannot be governed by the laws which regulate animated fvftems, but muft proceed according to the rules governing the decompofition of organic bodies in fuch cir- cumftances. Chemical inveftigation here med- dles not with living nerves and fibres, whofe functions are not to be interpreted by its aid, but limits itfelf to the watching into what new forms the inanimate parts of plants and ani- mals are changed after introduction into the belly ; a fubject on which it is certainly com- petent to decide. It has been confidered, that in ordinary cafes, the folution of food in the gaftric fluid regularly takes place, and the dis- covery has been acknowledged to be one of the happieft which phyfiology has to boaft of. Be- yond this, our inquiries are very little fatisfac^ torv; and the inteftines, though fo eflential to health, and fo frequently the feat of difeafe, have, in the midft of much curious refearch, been, ftrangely overlooked. If, in confidera- tion of their containing inanimate 'fubftances, prone tr> undergo the putrefactive procefs, i$ on be fhewn, that the caufes ufuclly preventa- tive < *7 ) five thereof are, duringcertain feafons, fufpended or weakened, then it will be evident that changes may take place within the inteftines, correfpon- dent to thofe which go on without them, and that fimilar productions will flow from the one which are known to characterize the other. Sydenham, (continual fever of the year 1661 and feq.) fays, *' he would give an emetic in the " beginning of that fever, that the fick might " be preferved from thofe dreadful fymptoms " that arife from the filth of thofe humours that " lurk in the fiemach and neighbouring parts, &c." and feems to have a good general idea of the noxious quality which the contents of the guts fometimes poffefs. In his account too of the peftilential fever and plague which raged in London in 1665 and 1666, he enumerates " violent vomiting?, a pain about the region of " the heart, as if it were oppreffed, and a burn- ing fever," among the earlieft fymptoms. Huxham, (Effay on Fevers, chap, viii.) de- fcribing the fymptoms of the fevers which he terms putrid, malignant, and petechial, men- tions, that together with " head-ach and giddi- "• nefs, ravfia and vomiting are much more con- " fidercble than in the flow nervous fever, even " from the very beginning.'''' In fliort, in the collected opinions of thofe phvficians, whom Mr. Howard confulted on the plague, as prevailing in the fouth of Europe and in Afia, (Account of Lazarettos) drynefs of the tongue, vomiting, hiccough, naufea, lofs -of ftrength and fever, are enumerated among the firf fymptcir.s. B 3 Indeed, ( i8- ) Indeed, the obfervation of any phyfician of much practice, in complaints of thefe kinds, as well as in the yellow fever, bilious fever, &c. is fufficient in fatisfying him, without recurring to written authorities, that the difeafed ftate of the alimentary canal is not only one of the firft group of fymptoms that attract his notice, but is of the mod troublefome and dangerous nature too. It has been doubted what could be the caufe of fo much difturbance in the ftomach and bowels, The diforders incident to thefe are peculiar to animals, and are derived from the neceffity we are under, becaufe of our locomo- tive faculty, of carrying a quantity of manure conftantly within us; on which account our or- ganization in this particular differs exceedingly from the vegetable creation, who have their food brought them, but are under no need of taking the crude mafs within them. If vege- tables then have no analogous ailments, it muft be owing to their inhaling their chyle from their external furface, and the inconvenience experi- enced by animals, be referred to their taking into their bellies a good deal of matter beyond what is convertible to nourifhment, and carry- ing the fceculent collection about with them. Qur locomotive power is indeed a capital en- dowment ; but the difeafes of the alimentary tube, with their endlefs train of fymptoms and confequences, are the immenfe price we pay for it. Upon this view of the comparative ftructure of plants and animals, it would feem that we fliould examine the kinds and qualities of ( *9 ) of food in the latter, in order to afcertain the caufes of thofe complaints to which they are- peculiarly fubjected. And here it happens, we have a moft ftriking and inftructive fact to guide us. Mr. Verdoni declares, " that the. " Greek chriftians in Smyrna, during the fea- " fon in Lent, when they eat only vegetables, are " very feldom attacked by the plague; while " among thofe who eat fiefli, the contagion makes " great havock. Hence the beft means of pre- " vention are to eat moderately, and not at all 44 of animal food, &c." And I believe a multitude of facts tending toward the fame conclufion, could eafily be collected. The caufe of plague, and confequently of other analogous fevers, would feem to refide then, in the animal part of the ingefta; and fo, according to the theory, it ought: for, from that fource fhould flow the azote, or bafe of the gafeous oxyd, the caufe of the moft alarming and dangerous fymptoms accompanying this clafs of diftempers. It is a fact worthy of particular regard, that the two cafes of contagion caufed by the gafe- ous oxyd, one produced from external caufes, contaminating the air, and affecting the lungs and refpiration, and the other arifing from cir- cumftances exifting within the body itfelf, and difturbing the ftomach and inteftir.es, fhould have been diftinguifhed by Hippocrates. In his book, De ftatibus, he, with great fagacity, notes the "air" operating without the body, and the "fpiritus" acting within, and both of them utufing fevers; to the former he afcribes epide- mics, ( 20 ) raia, where, from a change in the qualities of the air, many perfons are incommoded, as in pef- tis; to the latter, he attributes_/rwW/Y.r, where, from bad diet, flatulencies proceed, creating dif- turbance in the whole animal frame. There are four facts concerning the alimen- tary mafs which imprefs the mind with the be- lief of the actual extrication of the gafeous oxyd in the prima; vise. Firft, The production of a gas is manifefted by tenfion, oppreffion, and belching, as unequivocal figns denoting wind, diftending the bowels. Secondly, On fome oc- cafions, there is a vomiting of black matter, which confifts frequently of extravafated blood ; this tends to determine the gas to be of fuch a fort as to afford no oxygene to the blood, which therefore requires no rloridity. Thirdly, The exiftence of green ftools, in certain ftages of the difeafe, point with more certainty to this oxyd as their caufe, particularly fince it has been ob- ferved to tinge both water and glafs of a re- markable green colour. And fourthly, There is no inftance related of perfons afflicted prima- rily with this malady, except flefh-eaters. A fource of poifonous effluvia thus feems to exift in our own bodies, fufficient to difturb the animal machine exceflively, and even to efiect its deftruction. There can hardly exift a doubt, that the greatquantitiesof butcher's meat, poul- try and fifh which we confume, are the mate- rials which chiefly afford the gafeous oxyd, and that in our choiceft viands, we fwallow down the principle of ficknefs and decay. Ti e £efh of flaugh'ered animals, prone in hot v. ei « ther ( 21 ) ther to enter upon an incipient putrefaction, may, in fome cafes, not meet with a fufficienii corrective in the ftomach, and purfuing its propenfity there, may go on to rot and rot, and induce, by its mifchievous productions, the moft calamitous confequences. It has been long ago doubted, by confiderate and humane perfons, whether man was juftifi- able in preying upon his fellow animals. The authority of revelation, added to the make of his teeth, and the conclufions of reafon, have decided in favour of his right. But how far this indulgence, or luxury, for animal food can fcarcely be called a neceffary of life, may be gra- tified, is left wholly undetermined. Our own experience alone, of the wholefome or perni- cious effects refulting from its ufe, muft guide us. Judging by this, there appears a phyfical certainty, that we devour more of it than does us good ; nay, that in the enormous deftruction of animal matter, raifed in fuch abundance for cur riot and gluttony, fome of the moft ferious of bodily evils are generated, and thefe particu- larly in cities, camps and fhips,badly regulated. The caufes of fuchdiftempers are deeply found- ed in our ftate of fociety and way of life, and as long as we gorge ourfelves with animal food, r.nd dwell among its putrefactive recrements, the poifonous gafeous oxyd of azote proceeding therefrom, muft be expected to difturb both our refpiratory and digeftive functions, and be fol- lowed by fcenes of diftrefs and woe. 3dly. Provided, the oxyd fhould be produced during the diforganization of the food, &c. in the ( 22 )' the alimentary canal; what changes will it bring about in the chylopoetic vifcera, and what fymp- toms excite in the conftitution at large, particu- larly in thofe who at the fame time inhale more or lefs of it into the lungs? No perfon acquainted with the mode in which the animal body acquires its heat in the rungs,, need be informed that, in a cafe where the gafeous oxyd has, in a dilute form, been breathed, and from the fituation and circum- ftances of the patient continues every moment to enter the trachea, the fymptoms will be very different from thofe of a perfon whofe refpira- tion is free from contagion, but has the noxious gas in his bowels merely. It is therefore to be carefully confidered, that according to the na- ture and function of the organ on which the gafeous oxyd exercifes its virulence, will there be a variety in the morbid fymptoms, though produced by the fame caufe. If, for inftance, the ftomach and the inte'.iines are the feat of the gafeous refidenee, inflammatory fymptoms of thofe parts, with tenfion of the praecordia, dry- nefs and rednefs of the fauces, great heat and high pulfe may be expected to fupervene;— whereas, if the lungs are pervaded by it, the heat will be moderate, the countenance pale, purple, or yellowifh, the pulfe flow, and the firft paflages more quiet: while the moft violent dif- eafe muft enfue, when both the lungs and intef- tines are expofed to its virulence. i. Let its effects upon theftomaeh and bow- els be attended to. Ccftivenefi is favourable to the production of thii ( *3 ) this gafeous oxyd, by retaining the feeces an in- ordinate length of time, and preventing the ready efcape of the flatus. Accordingly, it is related, that in the bilious yellow fever of Phi- ladelphia, which prevailed in 1793, (Rufh's Ac- count, &c. 52.) " the bowels were generally " coftive, and in fome patients asobftinately fo " as in the dry gripes ; and flatulency was an " almoft univerfal fymptom in every ftage of " the diforder." From its qualities, as mentioned before, we are at no lofs to explain the painful burning which fometimes occurred before any vomiting took place, and the gaftrodynia which at times ufhered in the difeafe. Nor, when we confider the irritated or inflamed condition of the parts, can we be at a lofs to underftand wherefore it feldom appeared without naufea and vomiting, and why that vomiting was fometimes fo long continued, violent and convulfive. The inflamed ftate of the ftomach and duode- num, and other parts of the inteftinal tube, in all cafes of diffection after death, and the black, gangrenous and mortified fpots found there- about in numerous inftances, are juft fuch as might be expected from the operation of a gas fo deleterious as the azotic oxyd, which in fome cafes of high malignancy may.be imagined to acquire by union with a larger portion of oxy- gene than common, an uncommon degree of activity, or acrimony as it is called; in its effects, refembling in every particular that condition in- duced by the oxyd of arfenic* TWp * ft is remarkable what an analogy there is be- ( H ) The coffee-coloured, grumous and dark mat- ters ejected from the ftomach, are probably in a great meafure derived from the fanguineous fluid, blackened by contact with the gas, and effufed from the veffels ruptured by its erofion or caufticity. Some part of them may confift of bile vitiated by the fame caufe, and of putrid ichor proceeding from the gangrenous fpots. Excoriations of the rectum and external ter- mination of it, correfpond to the inflamed ftate of the fuperior portions of the inteftinal canal, and tween this oxyd of azote and metallic oxyds. Azote, as well as the metals, in its pure ftate has little or no chemical operation upon the body : as foon, however, as they become oxydated, they acquire ailivity ; and that this adivity is proportioned to the quantity of ox- ygene they abforb, is Jufficiently evinced by the pre- parations of antimony, arfenic and quickfilver. There is another trait of character in which azote rejembles arfenic and fome other metals, which is, that they are both acidifiable bafes: as by increafing the quan- tity of oxygene, you change the oxyd of the metal to an acid, poffeffing powers greatly fuperior to what it t°JTeJfed before, fo, by giving the oxyd of the gas a larger dofe of the acidifying principle, you increafe hs aclivity to an extreme degree. There is thus a very ftrong chemical analogy between the cxyd of azote, and white arfenic. Perhaps azote is a metal. Quick- filver is a metal, maintaining fluidity under the common circumftances of terreftrial heat and atmof- pherical prejfure. May not azote be a metal exift ing in the fame circumftances of warmth and weight in a vaporific form ? ( *5 ) and are fairly afcribable to the fame caufe; as is alfo the hiccuping. In a word, the pain in the fides, and in the regions of the ftomach, liver, and bowels, with their hotnefs and fpafms, and with the confe- quent diftrefs both of body and mind, all indi- cate the locality of this malady, as well as point to the nature and caufe of it. There is one cafe which may be imagined to happen, in which the ftomach and bowels are difturbed by the gafeous oxyd fwallowed with the fpittle and the food. Where the oxyd is abundant, it can eafily be underftood from its difpofition to unite with water, that fome part of it may attach itfelf to the fluids of the mouth, and be fwallowed ; as alfo forming a connection with the alimentary mafs in the act of chewing, may, together with it, defcend into the fto- mach; and thus, in either cafe, produce its harmful effects. 2. Its operation upon the lungs fhall be next inquired into. If a full infpiration of the gafeous oxyd be made, there will be a fudden extinction of life; and this accordingly accounts for the fact relat- ed by Ruffel, (Hiftory of Aleppo, p. 232.) and confirmed by other obfervers, of many perfons falling down dead fuddenly, when ftruck with the contagion of the plague. If a quantity of the fame fluid be mingled in fuch proportion in the atmofphere, as by its di* lute ftate to produce neither immediate death, nor catarrhal affections; then the flow and un- derminingeffect of it, bv conftant breathing, will C be ( 26 ) be manifefted, firft in the fighing, anxiety, tofiing of the body; afterwards by languor, faintifh- nefs, coma; and afterwards by the fleep-like and gentle approach of death. An inhalation of a more condenfed or con- centrated oxyd will account for the pulmonic fymptoms fometimes occurring, give rife to pain and convulfions, and lead to an explana- tion why, after running a certain length, they fhould fuddenly end in effufions of blood or other fluids to ftop the refpiration entirely. I am fatisfied, from experiments repeatedly made upon myfelf and others, that the heat of the body and beat of the heart and arteries are, to a certain degree, under the government of the will. This depends upon their connection with the refpiratory organs. If, while all the other voluntary mufcles are at reft, breathing be quickened by an effort of the will, the aftion or the heart and arteries will be increafed, and \o will the heat of the body; if, on the other hand, a perfon fitting as quiet as polfible in a chair, infpires the fmalleft poffible portion of air that he can, without bringing on anxiety, and con- tinues to do {o for fome time, a thermometer placed in the arm -pit will fall feveral degrees, and the pulfations of the heart and arteries be ex- ceedingly diminifhed in frequency and force. I mention thefe experiments to fhow how inti- mate the connection between refpiration and the circulation of the blood is in the moft healthy ftate of the body, and how the latter is governed by the former.. The heat of the body ,is nearly, other things being equal, in propor- tion ( 27 ) {ion to the oxygene gas decompounded in the Kings, and fo alfo is the force of circulation from the ftimulant quality imparted to the blood. If the air infpired be mixed with a large quantity of non-refpirableair, then, though a full inhalation be made, there will be but a fmall portion of vital air decompounded, and, as in the cafe of voluntary diminution of the breath- ing, the heat muft be leffened, and the con- tractions of the heart be more flow and feeble. It can eafily be underftood then, wherefore in fome cafes there fhould be weaknefs of pulfe ; in others, no uncommon quicknefs or frequen- cy; in others again, fuch lownefs that it can be hardly felt. We hence are enabled to un- derftandwhy the pulfe fometimes intermits, and to account for that remarkable flownefs, which, when confidered in this point of view, indicates extremeft danger; while, according to the or- dinary way of judging, it has been confidered as denoting that there was no fever: and the juftnefs of this interpretation is confirmed by obferving, on diffedtion, the blood in the heart refembling, in its qualities, the blood of perfons that have been hanged. The coolnefs of the fkin and the coldnefs of the limbs are in this manner very naturally accounted for. In certain cafes of high malignity, the bodies of patients dead of fever caufed by this gafeous oxyd, have been all over disfigured with purple fpots, and have even fometimes affumed a biackifh hue. Yea, even during life, vibices and blacknefs are known to make their appearance, and when they do, to be attended with cold- C 2 nefs ( 28 ) nefs prevailing in the livid parts a day or two before death. Thefe appearances are entirely explicable upon the idea, that the lungs are fil- led with a fpecies of air, not capable of oxyga- nating the blood, carrying away its carbone, and imparting heat to the body. The cafe defcribed by Huxham, in pages 98 and 99, is a very inftrudtive one,andilluftrates this doctrine in a forcible manner; as does the cafe defcribed by Sandifort. (Obf. Anatom. Pathol. 11.) From a review and confideration of the hif- tory of fuch cafes, it would appear there was a fcorbutic habit of body induced, and that the haemorrhagies, debility, and proftration of ftrength, as well as the darkened colour of the blood, and the want of cohefion in the folids, might be all accounted for upon the fame prin- ciple in fever as in fcurvy. It very foon occurred to me, if my idea was juft, that the gafeous oxyd ought, when in a concentrated form, and approaching the ftate of an acid, jo manifeft itfelf by corroding metallic fubftances. On inquiry, I found facts of that kind on record; for Van Swieten relates, " that " in the plague of Oczakow, xhtfihcr hilt of a 44 fword, which all the time of the plague him;; "up in a tent, was changed quite black: and "the inftruments which the furgeonsmade ufe 44 of were turned as black and livid as if they had 44 been dipped in aquafortis," (nitrous acid.) (Comment, in Aphor. Boerhaav. § 1407.) Upon difcovering this, I became convinced, that if my conjecture was right, a fubftance fo «<5tive as the gafeous oxyd ought, when applied to ( 29 ) to the fkin of well perfons, to excite diforder there, and this I found to be true: for Van Helmont (Tumulus Peftis, p. 853.) faw a man, 44 who, upon touching fome papers infected by 44 the plague, felt inftantly a pain like the prick 44 of a needle; a peftilential carbuncle made its 44 appearance foon after on his fore finger, and 44 he died in two days." A man who ftirred up with his foot the ftraw whereon the bed of a perfon fick of the plague had been laid—" a 44 little while after he felt an acute pain in the 44 lower part of his leg, juft above the foot, as if 44 the part had been fcalded with boiling water; 44 the next day the epidemis or fcarf-fkin was 44 elevated into a large blifter, upon breaking 44 which, a quantity ofblackifh liquor run our^ 44 and underneath, a latent peftilential carbuncle 44 was difcovered, which could hardly be cured 44 in a fortnight." (Van Swieten, § 1409.) There was another inference from my prin- ciple upon which I laid fo much ftrefs, that if it had not turned out according to my predic- tion, I fliould have given up ttrs whole matter as vifionarv. This was the effect that air of the kind I had in contemplation fhould have upon brute animals of the dorneftic kind. Thus Sorbait. of Vienna (quoted by the laft men- tioned author) fays, that during the plague, 44 larks, fo numerous in Auftria during the au- 44 tumn, were wholly wanting, fo that not a 44 fingle one could be met with; and tame birds 44 kept in cages all died." Homer mentions the death of dogs and mules as the forerunner of the peftilence in the Grecian camp before Troy. C 3. (Iliad ( 3° ) (Iliad i. 69.) The pernicious and deadly effefts of the atmofphere during the plague at Athens, in the fecond year of the Peloponnefian war, upon birds and beafts, and particularly on dogs, is mentioned by Thucidydcs* (B. ii.) Boccace, in * The difputes concerning Epidamnus and Corey ra lad for fome time agitated the governments of Co- rinth and Athens. Thefe diffentions, founded chi efty_ in ajealoufy of the growing and encroaching power 0/ "the people of Attica, fumifhed fufficient pretexts for moft of the ftates of the great Pehponnejus, to join in a confederate war againft them. In the 43 ift year before Chrift, the war began between the Pehponne- fians and Athenians, and their confederates on both fides That more vigorous preparation might be made for war, Pericles advifed the Attkans to move from their country refidences to their chief town Athens. Hit advice was followed. They fent away their Rocks and labouring cattle into Eubaa and the adja- cent i/Iands, tore down their houjes, and with their wives, children and furniture, forrowfully moved from the open country, where they had been accufiom- ed to live, to their metropolis. Great inconveniences were now experienced by them, efpecially fince that, after repairing the wafie committed by the invafion of Xerxes, the inhabitants had efiablifhed themjelves m a moft comfortable way of living. After moving, they were obliged to adopt a new mode of life: Jew had houfes ready for their reception: fome fheltered themfelves with their friends and relations: the greater part were forced to fettle in the lefs frequented quarters of the city, in the buildings facred to the gods end heroes; and many were even obliged to lodgt ( 3* ) in-his account of the plague at Florence, *4 faw •4 with his own eyes, two hogs that had rolled 44 about with their fnouts, and gnawed fome 44 pieces of bread which had been thrown into 44 the ftreet from a poor man's houfe who had 44 died of the plague, inftantly feized with con- 44 vulfions, and died within an hour after." In dogs and cats the fymptoms of plague have ac- tually been known to appear, fhewing them- felves in the form of buboes, &c. The cats of Philadelphia died in 1793, and it is highly pro- bable themfelves "within the turrets of the walls, or where-- tier they could find a vacant corner. Infhort, there wis a greater number of people than the city could contain, and after the Pelafgic was occupied, the Long-walls and great pert cfthe Piraeus were por- tioned out to them for little dwellings. Thus pent up, the Athenians continued accumulating filth and every kind of noxidus matter among them during the winter and until the enfuhig fummer, when, on the operation of heat, the gafes were volatalized that brought on the memorableficknefs, which has been called the plague of Athens. The attempt of Thucidydes, to trace it back to Lybia, Egypt and ./Ethiopia, is wholly unfatisfailory, and jufi as groundlejs as our own endeavours at prefent to prove yellow fever always imported from the IKefi-Indies or fome other foreign place. The caufes cf the plague at Athens, which was, in fait, only a very bad yellow fever, ex- ified among then felves, jufi as they do among the New-Yorkers and Philadel Hans nowa-days. A truth fo plain and fo important as this is. ought to bt eaididly received by every citizen of the United States, ( 32 ) Dable their deaths are to be in part afcribed to the gas they breathed. Again, if the idea I entertained was well founded, the gafeous oxyd ought, when very concentrated, to (hew its capability to fupport flame. The two following facts, though not related with fufficient accuracy or diftinctnefs, are however cafes in point, and as far as they go, illuftrate and confirm the doctrine in a forceable manner. The firft is, " that a light- 44 ed candle being held near dying perfons, a 44 very livid vapour was feen to iffue from their 44 mouths." The other, the relator fays, he fre- quently obferved in the form of a blue fmoke, as it were, in the rooms where the infected lay. (Van Swieten, § 1407.) Now, when thefe facts are compared with what Pritftley defcribes of a candle burning in the gafeous oxyd with an en- larged flame, by another flame (extending every where to an equal diftance from that of the candle, and often plainly diftinguiftiable from it) adhering to it, and in fome of his experi- ments burning blue, there appears to be con- siderable fimilarity in the cafes. Moreover, knowing that under an atmof- pherical preflure, which fupports the quickfil- ver in the barometer at 29 .84 inches, and in a temperature of 54.5 of Farenheit's fcale, a cubit foot of azotic gas weighed one ounce thirty grains and one half; and of oxygenous gas, one ounce one dram and fifty-one grains; it was prefumable that a combination of the two, that is, thirty-feven parts of oxygene united with fixty-three of azote, would form a fluid of near- ly ( 33 ) ly the fame weight with atmofpherical air, or rather heavier, and the probability of this would increafe, by confidering that a cubic foot of ni- trous gas, which contains only thirty-one parts more of oxygene than the gafeous oxyd does, weighs one ounce two drams and thirty-nine grains. An inference from this is, that perfons who refide in low fituations, where the gafeous oxyd is generated, or patients who lie near the floors of infected chambers, ought to fuffer more than others, by reafon of their breathing an at- mofphere more loaded with non-refpirable va- pour, tending downward on account of its weight. This inference from the principle is alfo conformable to fact, fince it is known both in New-York and Philadelphia, the lower parts of the city have been moft feverely afflicted, and that phyficians, friends, nurfes, &c. who walk erect in the chambers of the decumbent fick, efcape danger, and breathe a tolerably pure air; while the unhappy patient, lay ing near the floor, toward which the heavier oxyd fettles, inhales deadly gas at every infpiration. Again, it was clear to me from the little dif- pofition the gafeous o;:vd pcfTeffes to combine with other bodies, and, from its considerable weight, that it might be tranfported from place to place, in tight boxes or packages of goods, &c. and that, on opening thefe, and taking out their contents, the unchanged gas might be in- fpired into the lungs, or infinuate itfelf into the ftomachs of fuch perfons as fhould be expofed to it. This inference from the principle is alfo conformable to fact; for upon it depend the in- stantaneous, -. c 3+ y ftantaneous deaths in fome cafes; tranfporte«I infection in others; and fevers kindled up in others, from the fubtil matter exhaling froav iuch fomes. Befides, if, from the heavinefs of the oxyd, it always has a tendency to the lower parts, then fhips, through whofe fides it cannot leak out by reafon of their tightnefs, fhould be very apt to accumulate it; and this too correfponds with the fact; fea-veflels being among the chief agents in its production and dilfufion, the re- ceptacles of its collected virulence, and the feats of its moft deftrndtive ravages. Cellars are noxi- ous for the fame reafon. It muft be obvious, that the fymptoms of thefe febrile difeafes, excited by the gafeous oxyd, are divifible into two claffes. Sporadic cafes mav occur, in which, from its production within the body, the ftomach and bowels may chiefly labour,'and in thefe will the fymptoms firft enumerated prevail, attended with high ex- citement of the fyftern. Endemic ticknefs may generally be expected, when, from an extrica- tion of the gas in large quantity from fome abundant fource without the body, the conta- gion operates upon the lungs, and produces the fecond clafs of fymptoms, and in thefe wiWthe pulfe be flow, and the heat moderate. The word cafes that can occur will be thofe, where, both from external and internal caufes, the fto- mach, and lungs, and fkin, are attacked at once, and afford a mingled affemblage of fymptoms. There has been much difpute about the pro- duction of contagion, whether from animal or vegetable ( 35 ) vegetable matter. The controverfy feems to me to be a trifling one. It is undcrftood from ana- lvfis, that the bodies both of plants and animals a'recompofed of the fame elements or princi- ples, vaying in their proportions, Structure, &c. It is known for inftance, that oxygene, which conftitutes ^5th parts of the azotic oxyd, is very plentiful in moft vegetable fubftances, and that fome of them alfo contain a portion of azote, the ingredient forming the other xsVb parts. In fuch cafes there can be no question, that the oxyd mi^ht be produced during their decomposition. It is likewife known, that ani- mals contain a very great proportion of azote, and moftly a moderate quantity of oxygene. There can be hardiy a queftion then, that the oxyd might be generated from decaying fub- ftances of this fort. But as the one fubftance is highly charged with oxygene, and the other with azotr, the mixture of the two feems moft likely to afford the greateft amount of oxyd, and this, I believe, is agreeable to fadt. Pure animal matter will therefore perhaps be lefs likely to af- ford this oxyd than a mixture of it with vege- table. This explains why the Stomachs of liv- ing perfons, containing commonly a mixture of the two kinds of food, and the abdomen of dead bodies, are fo prone to the production of it ; and whv Slaughter-houfes, tan-vats, currying- houfes,'works for making glue and Pruflian blue, the horner's bnfinefs, oil Shops, and ma- nufactories of foap and candles, are not re- markable for generating contagion. There is very little acefcent vegetable matter employ- ( 3& ) ed there, and confequently the gafeous oxyd i« fparingly formed. On the other hand, in vine- gar cellars, wine prefles, cyder mills, and other places where much unmixed vegetable matter of the oxygenous kind is accumulated, no in- convenience arifes, as there is little azote to join in producing the oxyd. I fee, however, no improbability in the idea, that independent of animal and vegetable matter at all, there may exift in nature fome mode of combining oxy- genous and azotic airs. But I know of no fuch procefs at prefent. This inquiry has brought contagion home to our doors, and traced it to its feat within our bodies. Henceforth much of the labour em- ployed in tracing the origin of fevers in foreign places, and their introduction in Ships to our own ports, may be confidered as fuperfluous. Caufes enough exift among ourfelves, at cer- tain times, to engender the moft noxious va- pours. The Study of the production, and dif- fusion of thefe from domeftic and internal fources, fliould moft affiduoufly engage our at- tention. In doing this, we Shall be employed in earneft, in counteracting as well as detecting this wide-fpreading and terrible evil. On this head I Shall firft fpeak of prevention, as it refpedts the ftomach and inteftines. According to the theory delivered, the per- fons who live on vegetable food, or keep a lax belly, ought to have no difordcr, or a very flight one. This conclufion is confirmed by facts in abundance. The advice given by the Arabian phyficians to prevent the plague, en- joins ( 37 ) joins the repeated ufe of acid fruits, as pomgra- nates, Seville oranges, lemons, tart apples, &c. but above all wine-vinegar in fmall quantities, &c. (Mead on the Plague, chap, ii.) Doctor Wade has eftabliShed the efficacy of a vegetable diet, (Rufh on Yellow Fever, 334.) and of water as a drink, as the beft means of preventing the yellow fever in a hot climate. Mr. Howard has borne testimony of the benefit of low diet as a preventative of the plague ; and it is reported, that during the famous plague defcribed by Thucidyc'es at Athens, Socrates the philofopher preferved his life by means of Slender diet, as did Juftinian at Constantinople in a fimilar cafe, by his abstinent way of living. The avoiding of animal food, adhering to alow diet, and taking laxatives, was doubtlefs one of the means of preferving the life of Dr. Rufh, during the late calamity in Philadelphia; and what may ferve as a hoft of facts, in a word, it is related by Bontius, that the plague has never yet Shewn itfelf among the natives (rice eaters) of the Eaft-Indies. Speaking of China, Dr. Mead fays, " We have no inftanceof the plague 44 that was originally bred in that country." Here then, we have evidence of fuch an ex- tenfive and conclufive kind, as to fatisfy even the fceptical mind concerning the eafe and pof- fibility of prevention. By avoiding animal food, azote is kept out of the ftomach, the de- structive gafeous oxyd is not formed, nor are the inflammatory torments of the bowels felt. By keeping an open belly, the plan of fecuring the health will be promoted, and no detention D of ( 38 ) of feculent matter ( 4° ) 1793, who tells us, (p. 6.) that cholera, re- mitting fevers, dyfentery, influenza and Scar- latina were the immediate forerunners of the diforder he defcribes; and that, " in the courfe " of a few weeks, (p. 89.) they all difappeand 44 or appeared with Symptoms of the yellow fe- " yer; fo that after the firft week in September 14 it was the folitary epidemic of the city." The cafe of the girl immediately following this quota- tion proves the proposition I am contending for to a demonstration. There is reafonable fubjedt of inquiry too, how far phthifis in hot climates, and fcrophula,may be derived from a likefource. The connection of this fever with other com- plaints is Strikingly exemplified in the follow- ing narrative: (Anfon's voyage, fol. p. 131.) But, (fpeaking of fcurvy) fays Mr. Walter, " it 44 is not eafy to complete the long roll of the 44 various concomitants of this difeafe; for it 44 often produced putrid fevers, pleurifies, the 44 jaundice, and violent rheumatic pains, and 44 fometimes it occasioned an obftinate cof- 44 tivenefs, which was generally attended with 44 a difficulty of breathing, &c. &c. At other 44 times, the whole body, but more efpecially 44 the legs were fubject to ulcers of the worft " kind, &c. &c." The evidence of analogy, too, Strongly favours the opinion, that other contagions and poifons may confift of the fame materials, varying but in their proportions, or in fome unimportant circumftance, and that the virus of fyphilis, fmall-pox and meafles, and of the fpider, rattle-fnake, and other ve- nomous creatures, as being all of animal pro- duction, ( 4* ) dudtion, may confift in the main of azote and oxygene, combined perhaps with fome other ingredient: and there is high probability that marfli miafmata will be found little elfe than a Similar compound. The ichor of cancer and other corroding ulcers is very probably pretty much the fame thing. The difeafe of rabid ani- mals, and the dread of water and other miferable fymptoms confequent upon their bites, may very probably receive fome light fronrthis fource; and fo perhaps may fibbens, yaws, and leprofy. We have confidered already what varied fymptoms may be caufed by the fame matter operating upon different parts of the animal frame. In all probability much of the differ- ence obfervable in the operation of different poifons, arife from the fenfibility, irritability, Structure and function of the part to which it is applied. This idea at leaft feems to be countenanced, by what weobferve in thefyphi- litic virus, which, when applied to a fecreting furface, caufes gonorrhoea; to a dry one,chancre; to a glandular furface, bubo, &c. who knows but a fimilar excitingcaufe may, by operating upon the conftituion, in one way, produce continued, in another remittent, and in a third, intermittent fevers, which in reality differ from each other lefs in their caufes than in the particular part of the body to which this caufe is applied? The difference of the feveral fevers brought on by this gafeous oxyd being chiefly connected with the vifcus or function injured by its action, it is to be understood, that if the liver is invaded, this may induce, according to circumftances, an ( 42 ) an impeded fecretion of bile, and then there will be a fever without yellownefs, or an ob- struction of the gall-dudts, when, from an ab- sorption from the Secreted fluid, there will be yellownefs tinging the eyes or Skin, or a vitiated fecretion, appearing in the form of a green or brown matter vomited up. In like manner, when the lymphatic fyftem is the feat of its action, it may caufe buboes in the glands ; or when the fkin is befet by it, carbuncles, fores, and miliary and petechial eruptions may break out. So likewife in the mouth and fauces, aphthous ulcers, and erysipelatous inflamma- tion, a fpreading perhaps of the original malady in the ftomach, may all derive their origin from the fame caufe. This method of considering contagions is entirely conformable to the Simplicity of nature. The aSfignment of a multiplicity of caufes, to account for particular phenomena, always be- tokens a backward ftate of knowledge. The bufinefs of fcience is to generalize facts, to clafs phenomena under diftindt heads,and Show their dependance upon a common principle or caufe. Accordingly, in the progrefs of human reafon, polytheifm has yielded to the conviction of the existence of one God; the intricate and feemingly oppofite phenomena of matter and motion have been referred to one general law of gravitation ; the puzzling and diverfified appearances of elec- tricity have been reduced to a few plain rules; the multitude of facts concerning light and colours have been in like manner arranged into a fcientific form ; and both the rainbow and the tclefcope ( 43 ) telefcope bear witnefs to the fimplicity of optics. The fluids compofing our atmofphere have been analized, and the influence of thefe, and of many occafional combinations of other fubftan- ces into gafes, upon life and health, been invef- tigated to their principles. Contagion alone has remained a fubject for doubting and gueffing; a difmal fomewhat, whofe exact origin was unknown, and whofe operation feemed capri- cious or unaccountable. This, I truft, will now, like other agents in creation, be found to have its laws of production, diffusion and ac- tion, which are Steady and unvaried in their nature, as well as Simple and eafy to be com- prehended. I was going into the practical considerations and directions refulting from the principles laid down; but the fubject was fo extenfive, and ma- terials flowed in upon me fo faft, that the work would very fpeedily have extended far beyond the bounds I had now prefcribed to myfelf; and impreSTed as I was with the extenfive and beneficial application of this doctrine of conta- gion to every place upon earth where it is ge- nerated, and to every constitution upon which it adts, I felt a deep concern to make it public as foon as I conveniently could. FINIS. 2/70 CO ('7-9)^rmw