v/ T R E A T IS ON THE PLAGUE AND TErtOW F E V E R/ With an'APPEND1X, containing, HUTOR1BS OF THB PLACVB AT ATHKNI IN THE TIME OF THB PELOPONNBS1AN WAltj AT CONSTANTINOPLE IN THB TIME OP JUSTINIAN) AT LONDON lit X665; AT MARSEILLES IN tJ20; Scfi,<&'$('/ J? By J A MESTYTLER, ^/„r#n Vv Compiler of the Medical Part of the Encyclopaedia Sritannica. ffet every one. Phyfician or not* freely declare his own fentiments about it; let him afiign any credible account of its rife, or the caufes ftrong enough) in his opinion, to introduce fo terrible a fecne. Txv«tsi»s?> •Twas all the bufinefs thea To tend the fick, and in their turns to die. In heaps they fell. AfttfSTRQS^, Publiflied according to Ac! of Congrefs. SALEM: **tNTKD IT JOIHUff CVIRINC, P«» B, 8. MACANULTT. i;q9. C O N T E N T S. PART FIRST. Of the Afiatic or True Plague, SECTION I. Page Of the Plngue in general.—Inquiry into the Antiquity of the Dijlemper.—Of the Plagues mentioned in the Old Tejlameft.-—"Hiflory of feveral remarkable Plagues zvhich, at various times, have defolated the world. \ i SECTION II. -■'■■ Of the Countries were the Plague is fuppofed to originate. — The Influence of Climate in producing Difeafes— And of the Moral Condud &f the Human Race in producing and influencing the fame. 21 SECTION HI. Of Difeafe in general.—The nature of the Plague as a Difeafe conjidered.—Of Contagion.-—Whether the JPlague is really Contagious or not.—Medical Hif- tory of the Difemper.—Inquiry into its Immediate Caufes, and whether an approaching Plague is indi- cated by any vifble Signs. y± SECTION TV. Of the befi Methods of Preventing the Plague. 302 SECTION V. Of the Cure of the Plague. 347 PART SECOND. Of the Yellow Fever. SECTION I. Hijlory cflhe Yellow Fever. 3 71 SECTION II. Symptoms of the Yellow Fever, as deferibed by various authors.— Comparifon betzveen them and thofe of the Plague, with an inquiry into the Caufes.—Hiflory of 1k CONTENTS. Page^ thcDiftemper as it has Appeared in various parts of the United States fince the year 1793.—A difcujfton of the quejlion Whether the Yellow Fever h Con- tagious or not. L 3^2 SECTION' ML Methods of'Prevention and Cure". 5°7 SECTION IV. Remarkable Cafes. 53*4 A P P E N D I X. N* I. Account of the Plague at Athens, ik the time of the Pelo- ponn^an War:—From ThuC ydidss,—■ Sr*ithV Tranjldtion. 545 N* II. At count of the Great Plague in the time ofJusti- nian :—By ProCopiu*. 547 N° III. AccoifoYof the'Plague at London in 1665 :—From &f. Hodges< and others." £48- N- IV. Account' of the Plague at Marfeilles in 1720 .♦—From the Periodical Publications of the time. 554' Account of the Plague in Syria, Cyprus &c.—From Dr. Patrick Russel'j Tredtijv." ibicU* N° VI; .- ■ * Remarkable cafe of a Remitting Fever at 3ajp;rah in 178?. S56. N\ .VI?. Set of Queries furmfed by QoEiors Atkint and Jebb ; and by Mr. Howard -put to jeveral foreign Phy- sicians, during his tour \ with their Opinions i?.?- f>'rtihir the Plague. + 563 A'TPvE.VTISE 111 niliiii i ■ ii ■ ni»r».»ww«M—io—tr»i^Mw—iw^.i mm.....111^^1^ A ' TREATISE ON THE Plague and Yellow Fever. PART FIRST. Of the Afiatic or True Plague. SECTION I. Of the Plague in general.—Inquiry into the Antiquity of the Dijiempcr.—Of the Plagues mentioned in the Old Tefiament.—Hi [lory of fever al remarkable Plagues which, at various times, have defJated the world. AMONG the many difeafes which afflict the hu- man race, we find one, upon record, fo irre- filr.oie in its progrefs, fo fatal in its attacks, and fo entirely beyond the powers of medicine ; that, like the k'pent Python, the Leviathan, or the Mammoth, among animals, it has generally been diftinguifhed by names expreflive of its deftroying nature ; not, like other dif- e;.fes, by any particular appellation derived from its fymptoms. In the Hebrew language this diftemper is expreffed by the word which fignifics perdition ;* in Greek * Thus Dr. Hodges; hut Calmrt informs us, that the Hebrews call by the na"ir o« plagues aM difeafes lent by way ot punishment or correction from Cod; ii rix- ;>dtilenee, infeflion, the leproty, 1'udden death*, famines, tem- B A TREATISE ON Greek it is called loimos, from luo, to deftroy ; in Latin, peps, from peffundo, to overthrow; and in Englifh, the plague, from the Latin plaga, a ftroke with a whip j alluding to the common opinion, that it is a fcourge from heaven, taking vengeance on mankind for their fins. Other diftempers, called by the general name of Epidemics, have at different times infefted whole cities, and even overfpread extenfive regions j but thefe, though fometimes very fatal, have always been found fo much inferior to the diftemper of which we treat, that, on a comparifon, we may juftly fay, though epi- demics have ilain their thoufands, the true plague has flain its ten thoufands. In fpeaking of the dcftructive ravages of epidemics, we may count the dead by tens, by hundreds, or by thoufands ; but in the true plague, always by thoufands, by myriads,* or by millions. Procopius, when fpeaking of a plague which defolated the world in his time, compares the number of the dead to the fand of the fea> and Mr. Gibbon, who at- tempts tofpecify, thinks they might amount to an hun- dred millions;-{- and I cannot help being of opinion, that the deftruction generally occafioned by violent plagues, amounts to about one half of the population; the pells: in a wordt all calamities, whether public or private. Calmtd Di&. vol. ii- tbl. 412. Plaga. Parkhurft derives the Greek term loimos, either from tut, as above, or from another Greek word Signifying to faint; the fame from which the Englifh' word eclipfe has its origin ; or it may be from the Hebrew lebetn, to confume. A friend obferves, that «' we no where find the word perdition in our ver- sion of the Old Teftament. We have, however, the word d?jl>uEli(,n% which is of a fimilar import; as, for inftance, in Prov. xv. 11. where the Hebrew is abiun. In Rev. xvii 8 & 11, we find the Englilh word perdition ; but as we have no Hebrew verfion of the New Teftament, we may advert to the ancient Syiiac verfion. The Syrac being a filter dialed of the Hebrew, dif- fers, radically, but little from it. The Syriac of the two places referred to above is abdna ; hence the word abaddon, whole root is ebd, and is the lame with that of the Hebrew word above. " As to the word plague, we often find it in the Old Teftament, but per- haps never in that Ipeciric fenfe in which the moderns ule it. The original word, rendered plague, is pretty generally ngp, or its derivations ; as Exod. xii. 13. ii. Sam. xxiv. 21, &c." On this Lalt occafion, however, as the word fejiilenee had been ufed before, in the fame chapter, we can fearce doubt its having been really fome kind of difeafe : and we know that moder.n plagues will fometimes deftroy as quickly as this is faid to have done. * A myriad is generally fuppofed to contain ten thoufand. + Gibbon's Hiftory> vol. iv, THE PLAGUE. 3 the reafons for which opinion will be given in the courfe of this work. In all violent plagues, we hear of the dead being left unburied ; of their being caft into pits, &c. But if we wifh to make any grofs compari- fon between the deftructive power of the true plague, and that of any other violent epidemic, we cannot, perhaps, have a better inftance than that which took place at BafTorah (a city on the confines of Perfia) in the years 1773 and 1780.* In the former of thefe years that city was vifited by the true plague; and in the latter, by an epidemic remittent fever. The fever was moft violent in its kind, and deftroyed twenty-five thoufand in the city and neighbourhood ; but the true plague, no fewer than two hundred and feventy-five thoufand in the fame place. Suppofing the two com- putations therefore to be equally exact, we muft calcu- late this plague to have been eleven times more deadly than the epidemic. If therefore the ingenious claffifiers, in modern times, have brought into alliance the plague with other epidemic difcafes, and characterifed the former from the latter; we mayjuftly fay, that they have fal- len into the fame error with other naturalifts, who chara&erife the fuperior from the inferior; the lion from the cat, not the cat from the lion. As to the remedies applied in thefe difeafes, doubtful in epide- mics, they fo univerfally fail in the true plague, that, notwithftanding the improved ftate of medicine, we may yet fay, it ftands among difeafes, in a great mea- lure, like a giant without any champion to oppofe; like a poifon without any antidote. In this unhappy predicament, the breaking out of a plague, in any city or country, proves a mod diftrefling calamity, not only on account of the num- bers deftroyed by the difeafe itfelf, but by reafon of the bonds of fociety being loofcd; fo that humanity gives way to terror ; children are abandoned by their parents, and parents by their children ; every thing wears the appearance of ruin and defolation; while, in too many .inftanccs, avarice urges on the unprincipled * Tranfaft. of Society for improving Medical Knowledge^ 4 A TREATISE ON unprincipled to rapine, or even to murder. Nor are the cruel modes of prevention, fometimes prac- tifed even by the authority of the magistrate, lefs abhorrent to humanity, than the lawlefs outrage.? of the thief or murderer. Inftances of all this will appear in the courfe of the work; the following are ib remarkable, that I cannot help inferring them in this place. In the great plague at Marfeilles, in 1720, the town being almoft deferted, and few choofing to venture into it, "three fea-captains, and fome hundreds " of failors, having the courage to enter the city, from " the fea-fide, found therein a gang of murderers, who " made it their bufinefs to deftroy people feized with the ^plague, and to plunder their houfes, The ringleader " of them, named Rouamie, a gunfmith, was broken alive " upon th# wheel, and forty others were hanged. Rou- " anne owned that he had killed a thoufand perfons. " There were found, upon one of the murderers, jewels " to the value of more than thirty thoufand livres."* During the time of this public calamity, four men, who came from Marfeilles to Aix, were ihot by order of the parliament, left they Should have brought the infec- tion along wi(h them.-f- Even this is not equ'al to what Mr. Howard informs us was practifed in a hamlet of Dalmatia, where, the plague having raged with fuch violence, that only two or three remained ; the neigh- bouring magiftrates ordered thefe miferable furvivors to be fhot. At fuch prices will people buy a precarious, nay, an imaginary, fafcty. In (hort, what Mr. Gibbon fays of the Situation of people in the time of violent earthquakes, will alfo, in a great meafure, hold good in the time of peftilence, or any great public calamity. " lnftead of the mutual lympathy which might comfort " and aflift the diftrcfled, they dreadfully experience " the vices and palTions which are releafed from a fear " of punifhment; the houfes are pillaged by intrepid " avarice, revenge embraces the moment, and felects "the victim: while J vengeance frequently overtakes > * Political State for 1720. + Political ftate, ibid. " the * Mr. Gibbon, agreeably to the fubjeft on which he writes, particnlarifcs the mode of vengeance; faying, "the earth frequently fivalleius up the af- laflin," iic. It is hoped the iubftitution of the word vengeance, in general, will not be deemed a material alteration. THE PLAGUE. 5 " the affailin or ravifher in the confummation of his " crimes." Whether the world hath been in the fame predicament ever fince the human race began to multiply, or whe- ther plagues have originated at fome remote period, is a queftion not eafily determined. It is certain that, as far as hiftories go, they give us accounts of plagues; much lefs frequent indeed in very ancient times than in thofe which followed; but the compafs of hiftorical knowledge is narrow. There are no authentic hiftories of any nation previous to the termination of thofe of the Old Teftament. Where facred hiftory ends, pro- fane hiftory begins. The fabulous period affords many accounts of wars, heroes, giants, and monfters, but fearce any of plagues. Diodorus Siculus indeed makes mention of a plague which happened in Greece, after the flood of Deucalion ; and which, he fays, was occa- sioned by the general corruption of vegetables, &o. confequent on the flood. Deucalion's flood is fuppo- fed to have been nearly cotempoFary with the depar- ture of the Ifraelites from Egypt; fo that, if there is any truth in the relation of Diodorus, it is not impro- bable that fome of the Egyptian plagues might have fpread into Greece. We are likewife told of a pefti- lence at Athens in the time of Thefeus;* but all the accounts of thefe times are fo uncertain, and fo much involved in fable, that little or no dependente can be placed on any of them. The firft diftinct account we have of plagues of any- kind, then, is in the book of Exodus, where we are told of many heavy judgments fent upon the Egyptians becaufe of their difobedience. Before this, indeed, we read of plagues fent on the king of Egy-pt, for having taken Abraham's wife ; but as thefe fell only upon the king and his houfehold, we cannot fuppofe any thing like a general peftilence to have taken place among the people. In like manner did it happen to Abimelech, king of Gerar, on the dune account. All the women belonging to the king's houfehold were rendered barren * Univ. Kill. vol. vi. b A TREATISE ON for a time; but we hear of nothing happening to the nation at large. Again, when MoSes and Aaron went in before Pharaoh, they faid to him, " Let us go and facrifke to the Lord our God ; left he fall upon us with the fword, or with peji/ettce." Ihis ihews indeed that both Mofes and Pharaoh knew that fuch a thing as fejiilenee exifted, or might exift; but it cannot prove that the difeafe we now call the plague or peftilence commonly took place among nations in thofe days as it has done fince. Even among the plagues inflicted upon the Egyptians by the hand of Mofes and Aaron, we find only two that can be fuppofed to have any fimilarity to the difeafe we now call the plague ; viz. the boil, and the deftruction of their firft born. The former may have been peftilential buboes; the latter alfo may have been the effect of a molt malignant peftilence; fuch as, in the beginning of it, is faid frequently to kill fuddeniy, as by lightning; but whether it was fo or not, we cannot now determine. In the hiftory of Job, who is fuppofed to have been cotemporary with Mofes, we have a cafe more in point. The boils, with which he was covered, are by Dr. Mead fuppofed to have been the fmall pox; though in the true plague the body is fometimes covered with gangre- nous puftules, conftituting a difeafe ftill more dangerous and painful than the fmall pox; but whatever the difeafe of Job was, we may reafonably conclude, that in his time there was none Similar to it commonly exifting among mankind. After the departure of the Ifraelites from Egypt, we find frequent mention of a plague as a difeafe common- ly to be met with ; but it was always that of leprofy ; thofe deftructive plagues, which might be fuppofed to refemble the difeafe we now call by that name, being all miraculous. Concerning the prevalence of the leprofy among the Jews, Diodorus fays that they " were driven " out of Egypt as impious, and hateful to the gods ; for " their bodies being overfpread and infected with the * itch and leprofy, (by way of expiation) they got them * together, and, as profane and wicked wretches, expelled ' tl them THE PLAGUE. 7 " them out pf their coafts." This he tells us was a rea- fon given to one of the kings of Syria why he Should ex- terminate the Jews. In another place our author gives the following account of the origin of the Jewifh nation. " In ancient times there happened a great plague in E- " gypt, and many afcribed the caufe of it to God, who " was offended with them. For there being multitudes " of ftrangers of feveral nations who inhabited there, who " ufed foreign ceremonies, the ancient manner of wor- " Ship was quite loft and forgotten. Hence the natural " inhabitants concluded, that unlefs the ftrangers were " driven out, they Should never be freed from their " miferies. Upon which they were all expelled," &c. He then tells us that fome of them came into Greece under the conduct of Danaus and Cadmus; but the greater part entered Judea, then quite defert aud unin- habited. Their leader " was one Mofes> a very wife and valiant man," &c* ■ The allufion, in this laft paffage of Diodorus, to the plagues of Egypt, mentioned in Exodus, is manifeft j and it is equally manifeft, that the Egyptians them- felves, as well as the facred hiftorian, owned them, to be miraculous. Here, however, let it be remarked, that, though thefe, and others inflicted on the Ifraelites, were miraculous, we are not from thence to conclude that they took place without the intervention of natural caufes. On the contrary, in fpeaking of the plagues of Egypt, we are told, that when the locufts came, " the " Lord fent a ftrong eafl wind, all that day and all that "night; and when it was morning, the eafl wind " brought the locufts." In like manner " the Lord " turned a mighty ftrong zvejl wind, which took away " the locufts, and caft them into the Red fea." Again, when the fea itfelf was divided, " the Lord caufcd it to go back by a ftrong eafl wind all that night." The Egyptians were witnefles to this; but, as they did not believe that the powers of nature had any fuperior, they could never be induced to think that any of the elements would take part in a difpute between two nations, or favour the one more than the other. In * Diodor. Sic. Frag. S A TREATISE ON Tn difeafes inflicted von the human body, we are affured that the powers of nature were as much employed as in the miracles already mentioned. When it was told David that the child born to him by Bathlheba fliould die, the infant was feized with a natural diftem- per, probably a fever, and died the feventh day. When Hezekiah was informed that he Should die, he did not, any more than David had done, give himfelf up to defpair; but ufed, for his recovery, fuch means as were in his power, viz. prayers to God ; from whom, by the conftitution of things under the Old Teftament, he would receive a direct anfwer. And it is remarkable,, that though the anfwer was favourable, yet the difeafe was not removed by any invisible power operating like a charm, but by the ufe of a remedy. It is plain there- fore that this difeafe was occasioned by one natural power, and removed by another. The boil (for that was the dift«mper) was brought to maturity by a poul- tice of figs, andrthe king recovered.* If then the fcripture informs us, that even where the Deity himfelf Ipeaks, he has directed the ufe of a remedy, much more ought we to be diligent in the ufe of fuch as our feeble fkill can fuggeft, in thofe cafes where he leaves us en- tirely to the exercife of our own judgments. To fit down fupinely, in cafe of a dangerous diftemper, with a notion, that if God wills us to die we certainly Shall die, it any ufe of natural means ; and if he wills the contrary, that we 111 a 11 as certainly recover, in any neglecl of them ; is a conduct equally unfcriptural and abfurd. in the books of Mofes we find the Ifraelitc^ in cafe of difobedience, threatened with the botch of Egypt; with terror, confumption, and the burning (>«iurnal of the Plague Year. + See Append* No. IV. C " THE PLAGUE. *9 felt very feverely. In 1743 it was fuppofed to have deftroyed two thirds of the inhabitants of Mefllna. A particular account of its ravages was read before the Royal Society of London by Dr. Mead. The follow- ing is taken from Dr. Lobb's Treatife on the Plague. *' From the beginning of June to the end of July, of " forty thoufand inhabitants, two thirds perifhed. The " diforders in the city were incredible. All the bakers " died, and no bread was baked for many days. The ** Streets were full of dead bodies; at one time from " twelve to fifteen thoufand remaining in the open " air: men, womwi and children, rich and poor, all toge- " ther dragged to the church doors. The vaults being " full, and the living not fufficient to carry the dead " out of the city, they were obliged to put them on f funeral piles, and burn them promifcuoufly. No- " thing was more Shocking than to fee people, far above " the common ftations, go about begging for a loaf of " bread, when they could hardly walk, with their " tumours upon them ; and few were in a State to help " them. All thefe calamities did not hinder the moft " execrable villanies, which were committed every mo- " ment; and, ttpugh fo few furvived, the governor " was obliged to make feveral public examples," In the Turkish dominions, though we have not read of fuch extraordinary devastations as formerly took place, yet we are aflured that the peftilence rages there very frequently. From 1756 to 1762 we have hiftories of it by Dr. Ruffel and others, the fubftance of which ac- counts is given in the Appendix, No. V. In the time of the great war between the Turks and Ruffians, it found its way to Mofcow, which city it invaded in 1771. M- Savary fays, it was brought thither by infected mer- chandife from the Store houfes of the Jews ; and that it carried off two hundred thoufand people. In the Sixth volume of the Medical Commentaries, however, we are told that it was brought from the army by two foldiers ; both of whom were carried into the military hofpital, and both died. The anatomist who diflected their bodies died alfo, The infection quickly feizecj so A TREATISE ON the hofpital, and thence the whole city. This happen- ing in the beginning of the year, its progrefs was for fome time checked by the cold; but its ravages be- came greater as the fummer advanced. It raged molt violently during the months of July, Auguft and Sep- tember; in which time there were inftances of its deftroying twelve hundred perfons in a day. Twenty- five thoufand died in the month of September; in the courfe of which month fearce one in an hundred of the infected recovered. Only feventy thoufand, according to this account, perifhed by the difeafe. The year 1773 proved very fatal to Baflbrah ; where, as formerly men- tioned, two hundred and feventy-five thoufand perifhed in the fummer feafon, through the violence of the dif- temper.* But in countries where the plague rages fo frequently, and where there are few that make obferva- tions with any accuracy, we cannot expect complete hiftories of every attack made by it; neither would the limits of this Treatife admit of a detail of them, though there were. We know, however, that Since the year we fpeak of, the plague has ravaged Dalmatia, particu- larly in the year 1784, when it almoft defolated the town of Spalatro, deftroying three or four thoufand of its inhabitants. Though fome countries therefore have for a number of years remained free from the attacks of this terrible enemy, yet there are others where it is as it were Stored up, and from whence it may, on a proper occafiont break forth as formerly, and once more fpread ruin and defolation through the world. SECTION * An Englifh gentleman, who refided,in Baflbrah at that time, preferved Jiimfelf from the infection by retiring to a mud-hoofe, where he had no fcommunication with the inhabitants. Having a large quantity of Bengal cotton, he fold, it to the people to wrap their dead in. The price was put in a bafltet, which he hauled up by a rope to his ware-room ; lowering it again with the proportionate quantity of cloth. In the courfe of the fummer h* hid ari account oif-venty thoufand winding fheets thus difpofed of 1 (Tranfac*. of a Society for improving Medical Knowledge.) THE PLAGUE. 21 SECTION II. Of the Countries where the Plague is fuppofed to originate. — The Influence of Climate in producing Difeafes—And of the Moral Conduct of the Human Race in producing and influencing the fame, IN considering the origin of a calamity fo dreadful and fo univerfal, we might reafonably fuppofe that the fatal fpots which gave rife to it would long ago have been marked out and abandoned by the human race altogether. But this is far from being the cafe. In the accounts already given of various plagues, they are al- ways faid to have been imported from country to coun- try, but never to have originated in that of the perfon who wrote of them. If a plague arofe in Greece, we are told it came from Egypt; if in Egypt, it came from Ethiopia; and had we any Ethiopic historians, they would no doubt have told us that it came from the land of the Hottentots, from Terra Auftralis Incognita, or fome other country as far distant as poflible from their own. In (hort, though it has been a moft generally received opinion, that plagues are the immediate effects of the difpleafure of the Deity on account of the fins of men ; yet, except David and Homer (already quoted) we find not one who has had the candour to acknow- ledge that a plague originated among his countrymen on account of their fins in particular. In former times Egypt and Ethiopia were marked out as the two great fources of the plague; and even as late as the writings of Dr. Mead we find that the fame opinion prevailed. The Doctor, who attempts to explain the caufes of the plague, derives it entirely from the filth of the city of Cairo, particularly of the canal that runs through it. But later writers, who have vifited and refided in Egypt, aflure us that the country is extremely healthy, and that the plague is always brought there from Conftantinople. It is true that Dr. Timone, in the Philofophical Tranf- actions, No. 364, tells us, that it appears from daily obfervation, as well as from hiftory, that the plague comes ?2 A TREATISE ON comes to Conftantinople from Egypt; but the united testimonies of Savaiy, Volney, Mariti and Ruflel, who all agree that Egypt receives the infection from Conitan-. tinople, mult undoubtedly preponderate. " The peftilence (fays M. Savary) is not a native ot " EgyP^ ! have collected information from the Egyp- ft tians, and foreign phyficians who have lived there " twenty or thirty years ; which all tended to prove the " contrary. They have allured me that this epidemic " difeafe was brought thither by the Turks, though it " has committed great ravages. I myfelf faw the cara-f " vellesof the Grand Signior, in 1778, unlade, according Xi to cuftom, the Silks of Syria at Damietta. The plague " is almoft always on board; and they landed, without " oppofition, their merchandife, and their people who " had the plague. It was the month of Auguft ; and, " as the difeafe was then over in Egypt, it did not cc communicate that feafon. The veffels fet fail, and " went to poifon other places. The fummer following, " the Ships of Constantinople, alike infected, came to " the port of Alexandria, where they landed their dif- " eafed without injury to the inhabitants. It is an ob- " fcrvation of ages, that if, during the months of June, f4 July and Auguft, infected merchandife be brought *' into Egypt, the plague expires of itfelf, and the peo- f' pie have no fears; and if brought at other feafons, *f and communicated, it then ceafes. A proof that it " is not a native of Egypt is, that, except in times of " great famine, it never breaks out in Grand Cairo, nor ** the inland towns, but always begins at the feaports " on the arrival of Turkish veflels, and travels to the " capital; whence it proceeds as far as Syria. Having " come to a period in Cairo, and being again intro- fe duced by the people of Upper Egypt, it renews with " greater fury, and fometimes fweeps off two or three " hundred thoufand fouls; but always flops in the " month of June, or thofe who catch it then are eafily " cured. Smyrna and Conftantinople are now the f{ refidence of this moft dreadful affliction." M. Volney THE PLAGUE. 23 M. Volney informs us, that the European merchants refiding at Alexandria agree in declaring that the dif- eafe never proceeds from the internal parts of the coun- try, but always makes its firft appearance on the fea- coafts at Alexandria; from thence it pafles to Rofetta, from Rofetta to Cairo, and from Cairo to Damietta, and through the reft of the Delta. It is invariably prece- ded by the arrival of fome veflel from Smyrna or Conftan* tinople ; and it is obferved, that if the plague has been violent during the fummer, the danger is greater for the Alexandrians during the following winter. To the fame purpofe, the Abbe Mariti fays, " The " plague does not ufually refide in Syria, nor is this " the place where it ufually begins. It receives this tc fatal prefent from Egypt, where its ufual feat is " Alexandria, Cairo or Damietta. The plague of 1760 " came at once from Cairo and Alexandria; to. the " latter of which it had been brought from Conftanti- " nople. When it comes from that capital, as well as " from the cities of Smyrna and Salonica, it acquires a " peculiar malignity ; and its activity never expands " itfelf with more fury than in the plains of Egypt, " which it overfpreads with incredible rapidity. It is " obferved, that this plague, fo destructive to Egypt, " feldom attacks Syria; but that the latter has every " thing to dread from a plague hatched in the bofora " of Egypt." The teftimony of thefe three authors, who have all been lately on the fpot, mult certainly have very great weight, efpecrally when corroborated by that of Dr. Ruffel; for which fee Appendix, No. V. But ftill there is fome difficulty. M. Savary informs us, that, except in Cafes of great famine, the difeafe never breaks out in Cairo ; which certainly implies that in cafes of famine it does originate in the city itfelf; and Mariti, by fay- ing that the Syrians have much reafon to dread a plague hatched in the bofom of Egypt, undoubtedly intimates that plagues fometimes do originate in Egypt. Smyrna and Salonica likewife feem to come in for their Share of the blame ; and Dr. M'Bride, in his Practice of Phyfic, inform? H A TREATISE ON informs us, that fome parts of Turky are visited by the plague once in fix or feven years; and M. Savary lays, that Egypt is vifited with it once in four or five years; but if Egypt never receives it but from Turky, it would feem that the plague could at leaft be no-more frequent than in that country ; or, if the fact be otherwise, that the difeafe muft either originate in Egypt itfelf, or be brought to it from fome other country than Turky. Dr. Timone, in the paper already quoted,* tells us, that the plague has taken up its residence in Conftan- tinople ; but that, though the feeds of the old plague are fearce ever wanting, yet a new infection is likewife imported from time to time. Thus, in attempting to find out the countries where the plague originates, we are led in a circle. Conftantinople accufes Egypt, and Egypt recriminates on Conftantinople. Ethiopia, the moft diftant and leaft known of thofe countries which in former times had any connexion with the more civi- lized parts of the world, for a long time bore the blame of all; but the Jefuit miflionaries who refided long in Abyflinia (the ancient Ethiopia) do not mention the plague as more common in that country than fome others; neither does Mr. Bruce, in the accounts he has published, take notice of any fuch thing. Ethiopia could not fpeak for itfelf, by reafon of the ignorance and barbarity of its inhabitants; and Conftantinople is now very much in the fame predicament. The inves- tigation of this fubject therefore would require an accu- rate account of the climates of thofe countries where the plague is found to commit the greatcft ravages, and a comparifon of them with thofe which are now ac- counted the moft unhealthy in other refpects, and like- wife a comparifon of the difeafes produced in the latter, with the true plague. The moft unhealthy climates now existing (thofe where the plague commonly rages excepted) are to be met with in the hotted parts of the world ; the Eaft and Weft Indies, the waltes of Africa, and fome parts of America. In all thefe, Dr. Lind, who has written a treatife • Philofoph. Tranfadt. No. 364. THE PLAGUE. 25 treat ife on the difeafes incident to Europeans in hot climates, feems to lay the whole blame upon the heat and moifture accompanying it. In the Eafl: Indies Bencoolen, in the ifland of Sumatra, is the moft un- healthy of all the Englifh fettlements; but he informs us, that by building their fort on a dry, elevated place, about three miles from the town, it became fufficiently healthy. Next to this, Bengal is moft fubject to fick- nefs; for which heafligns the following reafon : " The " rainy feafon commences at Bengal in June, and conti- " nues till October; the remainder of the year is healthy " and pleafant. During the rains, this rich and fertile " country is covered by the Ganges, and converted as it *' were into a large pool of water. In the month of Octo- " ber,when the Stagnated water begins to be exhaled by *' the heat of the fun, the air is then greatly polluted by " the vapours from theflime and mud left by the Ganges, " and by the corruption of dead fifh and other animals. " Difeafes then rage, attacking chiefly fuch as are lately (C arrived. The diftcmpers are fevers of the remitting or 1' intermitting kind ; for, though fometimes they may " continue feveral days without fenfible remiflion, yet " they have in general a great tendency to it. If the fea- " fon be very Sickly, fome are feized with a malignant fe- " ver, of which they foon die. The body is covered with " blotches of a livid colour, and the corpfe, in a few " hours, turns quite livid and corrupted. At this time " fluxes prevail, which may be called bilious or putrid, lt the better to distinguish them from others which are " accompanied with inflammation of the bowels. The " ifland of Bombay has of late been rendered much more " healthy than it formerly was, by a wall built to prevent " the encroachments of the fea, where it formed a fait " marlh ; and by an order that none of the natives Should " manure their cocoa-trees with putrid fiSh. " Batavia, the capital of the Dutch Eaft India do- " minions, is annually fubject to a fatal and confuming " ficknefs. Here the Dutch, in attempting to make this, " their capital in India, refemble their cities in Europe, " have adorned it with canals or ditches, interfering each E other, 26 A TREATISE ON " other, running through every part of it. Notwithftand* " ing the utmoft care to keep thefe clean, during the " rainy feafon, and after it, they become extremely nox- " ious to the inhabitants, but efpecially to ftrangers. It " has been remarked, that the ficknefs rages with the " greateft violence when the rains have abated, and the " fun has evaporated the water in the ditches, fo that the " mud begins to appear. This happened in 1764, when " fome Britifh Ships of war had occafion to flay for a little " time at Batavia. The Stench from the mud was into- " lerable; the fever was of the remitting kind; fome were " fuddenly feized with a delirium, and died in the firft " fit; but none furvived the attack of a third. Nor was " the ficknefs at that time confined to the fhips ; the " whole city afforded a fcene of difeafe and death ; Streets "covered with funerals, bells tolling from morning to " night, and horfes jaded with dragging the dead in her- " fes to their graves. At that time a flight cut of the fkin, " the leaft fcratch of a nail, or the moft inconfiderable " wound, turned quickly into a putrid, fpreading ulcer, " which, in twenty-four hours, confumed the fiefh, even " to the bone. Befides thefe malignant and remitting fe- ;£ vers, which rage during the wet feafon in the unhealthy "parts of the Eaft Indies, Europeans, efpeciallv fuch as " live intemperately,are alfo fubject to fluxes, and to an " inflammation, or difeafe of the liver; which laft isalmoft " peculiar to India, and particularly to the Coromandel " coaSL" In the fame work we have an extract from Mr. Ives's journal of a journey from India to Europe by land || Gambroon in Perfia, fays he, is very unhealthful. tew Europeans efcape being feized with putrid inter- mitting fevers which rage from May to September, and are often followed with obstructions of the liver Various authors who have treated of Gambroon, do[ as we 1 as the prefent Englifh factory, impute its un- healthfulnefs, during the fummer months, to the nox- ious effluvia with which the air is contaminated, from the great quantities of blubber fi(h left by the fea no " on the Shore, and which very foon become highly of- *' fcnfive. THE PLAGUE. £7 " fenfive. In the rainy feafons, at the ifland of Karee, " in the Perfian Gulf, intermitting fevers and fluxes are " the ufual diftempers. On our arrival at Bagdad (fup- " pofed to contain 500,000 fouls) we found a purple " fever raging in the city; but though it was computed " that an eighth part of the inhabitants were ill, yet the " diftemper was far from being mortal. Here we were " informed that the Arabs had broken down the banks " of the river near Baflforah, with a defign to cover with " water the deferts in its neighbourhood. This, it feems, " is the ufual method of revenge taken by the Arabs for " any injury done them by the Turks at Baflforah ; and " was reprefented to us as an act of the moft Shocking " barbarity, fince a general confuming ficknefs would " undoubtedly be the confequence. This was the cafe " fifteen years before, when the Arabs, by demolishing " the banks of this river, laid the environs of Baflbrah " under water. The Stagnating and putrefying water in " the adjacent country, and the great quantity of dead ** and corrupted fifh at that time lying upon the Shore, " polluted the whole atmofphere, and produced a putrid " and moft mortal fever, of which between twelve and " fourteen thoufand of the inhabitants perifhed ; and, at " the fame time, not above two or three of the Europeans " who were fettled there efcaped. The effects of the " violent heats we endured were, an entire lofs of appe- " tite, a faintnefs and gripes, with frequent and bilious " ftools; which greatly exhaufted our Strength. My " Stomach was often fo weak, that it could receive only " a little milk. Several of us became feveriSh through " the exceflive heat, and were obliged to have recourfe " to gentle vomits, &c. Though we were furnished " with the moft ample conveniences for travelling, "which money, or the ftrongeft recommendations to " the principal christians, as well as mahometan chiefs, " could procure, and had laid in a quantity of excellent " madeira, claret, and other provisions, &c. yet moft " of us fuffered in our constitutions by this long and fa- " tiguing journey." On 2S A TREATISE ON On thefe climates in general Dr. Lind obferves, that in well cultivated countries, fuch as China, the air is temperate and wholefome ; while the woody and uncul- tivated parts prove fatal to multitudes accuftomed to breathe a purer air. In all places alfo, near the muddy and impure banks of rivers, or the foul Shores of the fea, mortal difeafes are produced from the exhalations, efpe- cially during the rainy feafon. " There is a place " near Indrapour, in Sumatra, where no European can " venture to remain, or (leep one night on Shore, during " the rainy feafon, without running the hazard of his " life, or at leaft of a dangerous fit of ficknefs ; and at " Podang, a Dutch fettlement on Sumatra, the air has " been found fo bad, that it is commonly called the " Plague-Coaft. Here a thick, peftilential vapour or fog " arifes, after the rains, from the marines, which de- " ftroys all the white inhabitants." In treating of the difeafes of Africa, the fame author takes notice of thofe of Egypt; which country, he fays, is rendered unwholefome by the annual inundation of the Nile, and being furrounded on three fides by large and extenfive deferts of fand, by which means it is ex- pofed to the effects of that noifome vapour, which, dur- ing the fummer months, arifes from fultry, hot fand. He doth not, however, fay, that the true plague origi- nates in this country, either from the inundation of the Nile or any other caufe. On the climate of Egypt I (hall once more quote M. Savary, who is a ftrenuous advocate for its healthinefs, and is at pains to confute the opinion of Mr. Pauw, and others, who aflfert the contrary. " Mr. Pauw (fays he) pretends, that at pre- " fent Egypt is become, by the negligence of the Turks " and Arabs, the cradle of the peftilence; that another " epidemical difeafe, equally dreadful, appears here, by " the caravans of Nubia; that the culture of rice en- genders numerous maladies; that the want of rain " and thunder occafions the air of the Thebais to acquire " a violence that ferments the humours of the human " body, &c." " Thefe aflfertions (M. Savary obferves) " have an air of probability, which might impofe on " people THE PLAGUE. 29 " people who have not lived in Egypt; but Mr. Pauw " has ventured opinions in his clofet, without the guid- •' ance of experience. In valliesj indeed, enclofed by " high mountains, where the atmofphere is not conti- " nually renewed by a current of air, the culture of rice " is unwholefome, but not fo, near Damietta and Ro» " fetta. The plains are nearly on a level with the fea ; " neither hill nor height impedes the refreshing breath of " the north, which drives the clouds and exhalations off " the flooded fields fouthwards, continually purifies the " atmofphere, and preferves the health of the people ; " fo that the hufbandmen who cultivate the rice are not " more fubject to difeafes than thofe who do not. The " heats of the Thebais certainly furpafs thofe of many " countries under the equator. Reamur's thermometer, " when the burning breath of the fouth is felt, fome- " times rifes to thirty-eight degrees above the freezing " point,* often to thirty-fix. Were heat the principle " of difeafes, the Said (Upper Egypt) would not be habi- " table ; but it only feems to occafion a burning fever, " to which the inhabitants are fubject; and which they " cure by regimen, drinking much water, and bathing " in the river : in other refpects they are ftrong and " healthy. Old men are numerous, and many ride on " horfeback at eighty. The food they eat in the hot " feafon contributes much to the prefervation of their " health ; it is chiefly vegetables, pulfe and milk. In " Lower Egypt, the neighbourhood of the fea, the large " lakes, and the abundance of the waters, moderate the " fun's heat, and preferve a delightful temperature. " Strabo and Diodorus Siculus, who long lived here, " did not think the country unhealthy. There is, in- " deed, an unwholefome feafon in Egypt. From Febru- " ary till the end of May, the fouth winds blow at in- " tervals, and load the atmofphere with a fubtile duft, "which makes breathing difficult, and drive before " them pernicious exhalations. Sometimes the heat " becomes infupportable, and the thermometer fudden- " ly riles twelve degrees. The inhabitants call this fea- "fon * Water boils at eighty degrees of this thermometer 1 3° A TREATISE ON " fon Khamfin, fifty; becaufe thefe winds are moft felt " between Eafter and Whitfuntide; during which fea- " fon they eat rice, vegetables, frefh fifh and fruit; " bathing frequently, and ufing plenty of perfumes and " lemon juice ; with which regimen they prevent the " dangerous effects of the Khamfin. But it mult not " be fuppofed that this wind, which corrupts meat in a " few hours, blows fifty days. Egypt would become a " defert. It feldom blows three days together ; and " fometimes is only an impetuous whirlwind, which ra- " pidly pafles, and injures only the traveller overtaken in " the deferts. When at Alexandria a tempeft of this " kind Suddenly arofe, driving before it torrents of burn- " ing fand, the ferenity of the fky difappeared, a thick " veil obfcured the heavens, and the fun became blood- " coloured. The duft penetrated even the chambers, and " burnt the face and eyes. In four hours the tempeft " ceafed, and the clearnefs of the day appeared. Some " wretches in the deferts were fuffocated, and feveral " I faw brought to appearance dead ; fome of whom, " by bathing in cold water, were reftored to life." The internal parts of the continent of Africa are but little known. The northern parts, containing the States of Barbary, are fufficiently healthy; the middle parts of the weftern coaft, known by the names of Negro- land, Guinea, &c. are extremely unhealthy and perni- cious to ftrangers. Dr. Lind informs us, that, at. a distance, this country appears in moft places flat, cover- ed with low, fufpended clouds; and on a nearer approach heavy dews fall in the night time; the land being every morning and evening wrapped up in a fog. The ground is clothed with a pleafant and perpetual ver- dure, but altogether uncultivated, excepting a few fpots, which are generally furrounded with forefts Or thickets of trees, impenetrable to refreshing breezes, and fit only for the refort of wild beafts. The banks of the rivers and rivulets are overgrown with buShes and weeds, continually covered with flime, which fends forth an intolerable Stench. All places however are not equally unhealthy ; nor is any place equally un- wholefome THE PLAGUE. 31 wholefome at all times of the year. It is only with the rainy feafon that the ficknefs commences. But as it would be tedious, and not anfwer our prefent purpofe, to enumerate thofe places which are healthy, and thofe which are not, I Shall only extract from Dr. Lind's work an account of one which feems to be as bad as can well be imagined. It is called Catchou, a town be- longing to the Portuguefe, and fituated in 12 degrees N. lat. " I believe (fays the author of this account) " there is fearce to be found on the whole face of the " earth a more unhealthy country than this during the " rainy feafon. We were thirty miles diftant from the " fea, in a country altogether uncultivated, overflowed " with water, furrounded with thick, impenetrable " woods, and overrun with flime. The air was vitiated, " noifome and thick, infomuch that the lighted torches " or candles burnt dim, and feemed ready to be extin- " guifhed ; even the human voice loft its natural tone. " The fmell of the ground, and of the houfes, was raw " and offensive ; but the vapour arifing from the putrid " water in the ditches was much worfe. All this, how- " ever, feemed tolerable, in refpect of the infinite num- " bers of infects fwarming every where, both on the " ground and in the air ; which, as they feemed to be " produced and cherifhed by the putrefaction of the at- " mofphere, fo they contributed greatly to increafe its " impurity. The wild bees from the woods, together " with millions of ants, overran and deftroyed the furni- " ture; while fwarms of cock-roaches often darkened " the air, and extinguished even the candles in their " flight ; but the greateft plague was the mufquetoes " and fand-flies, whofe inceflant buzz and painful Stings " were more infupportable than any fymptom of the fe- '4 ver. Befides all thefe, an incredible number of frogs, " on the banks of the river, made fuch a conftant and " difagreeable croaking, that nothing but being accuf- *; tomed to fuch an hideous noife, could permit the en- " joy ment of natural fleep. In the beginning of Octo- " ber, as the rains abated, the weather became very hot, u the woods were covered with abundance of dead frogs, " and $2 A TREATISE ON " and other vermin, left by the recefs of the river ; all " the mangroves and fhrubs were likewife overipread " with Stinking flime." . f . No doubt thefe accounts are calculated to mlpire us with dreadful ideas of the countries mentioned in them. What could be done by the putrefaction of dead ani- mals and vegetables, certainly would be done here; the produce, however, was not the true plague 3 not even in Catchou; but " a ficknefs which could not well be " characterifed by any denomination commonly applied " to fevers; it however approached neareft to what is " called a nervous fever, as the pulfe was always low, and " the brain and nerves principally affected," &c. Cer- tainly if in any country heat, moifture and putrefa&ion could produce a plague, it would be in this. Yet, in all the places we have mentioned, whether India, Arabia, Egypt, or Guinea, (and we might go through the whole world in the fame manner) we have not been able to find either moift heat or dry heat, even when aided by putrefaction, infects, and naftinefs of all kinds (not juft- ly chargeable upon any climate ;) I fay, we have not found the united powers of all thefe able to produce a plague. Nay, it is even doubtful whether climates can produce thofe inferior difeafes above mentioned. Even Dr. Lind, who appears to be fo willing to afcribe every thing to climate, feems embarraflfed in this refpect. " There " are many difficulties (fays he) which occur in afligning " a fatisfactory reafon, why in fome countries, as in thofe " between the tropics, heavy and continual rains Should " produce ficknefs; while in other places, efpecially in " the fouthern parts of Europe, a want of rain for two or " three months in fummer brings on difeafes almoft fimi- " lar. Upon this occafion (adds the Doctor) I cannot " help obferving, that there is hardly a phyfical caufc " which can be affigned for the produce of any difeafe, " that will not admit of fome exceptions : thus, not only " the woods and moraflfes in Guinea are tolerably heal- " thy, with fome exceptions, in the dry feafon ; but a few " inftances might be produced of towns furrounded with " marines and a foggy air, where the inhabitants fuffer no THE PLAGUE. S3 u no inconvenience from their Situation, even during the Xi rainy feafon. Do the impetuous torrents of water pour- " ed from the clouds during the rainy feafons, in tropical " countries, contain what is unfriendly to health ? Thus *' much is certain, that the natives of fuch countries, efpe- " cially the mulattoes, avoid being expofed to thefe " rains as much as poffiblej and when wet with theni " immediately plunge themfelves into fait water, if near "' it. They generally bathe once a day, but never in, " the freSh water rivers, when overflown with Tains, " preferring at fuch times the water of fprings. Is the " ficknefs of thefe feafons to be afcribed to the intenfe " heat of the then almoft vertical fun ; which frequent- " ly, for an hour or two at noon, difpeU the clouds, and "with its direct beams inftantly changes.the refreshing " coolnefs of the air into a heat almoft infupportable ? " Further : As the feafon of thofe fudden and terrible " ftorms, called the hurricanes, in the Eaft and Weft " Indies, and tornadoes on the coaft of Guinea, partly " coincides with that of the rains, do thefe dreadful " tempefts in any meafute contribute to produce the " prevailing ficknefs at thofe times ? It was remark- " able T)ne year at Senegal* that, in the beginning of the " rainy feafon, in the night fucceeding one of thefe tor- " nadoes, a great number of the foldiers, and two thirds '" of the EngliSh women, were taken ill, this garrifon " before having been uncommonly healthy. " Laftly : Is it not more probable, as in thofe ** countries the earth for t fix or eight months in the " year receives no moifture from the heavens but what " falls in dews, which every night renew the vegetation, *' and reinstate the delightful verdure of the grafs, that M the furface of the ground in many places becomes »"« hard and incruftated with a dry fcurf, which pens up " the vapours below, until, by the continuance of the " rains for fome time, this cruft is foftened; and the tft vapours fet free ? That thefe dews do not penetrate " deep into the furface of the earth; is evident from the " conftant drynefs and hardnefs of fuch fpots of ground, " in thofe countries, as are not covered with grafs and F " other 34 A TREATISE ON " other vegetables. Thus the large rivers, in the dry " feafon, being confined within narrow bounds, leave a " great part of their channel uncovered, which, having " its moifture totally exhaled, becomes a hard, dry cruft; " but, no fooner the rains fall, than, by degrees, this " long parched up cruft of earth and clay gradually " foftens, and the ground, which before had not the " leaft fmell, begins to emit a ftench, which in four or " five weeks becomes exceeding noifome; at which time " the feafon of ficknefs commences." From thefe quotations it muft certainly appear, that the author himfelf is diflfatisfied with his theory ; and that, though in the outfet he thought heat and moif- ture, affifted by the exhalations from putrid animal and vegetable fubftances, fufficient to produce the diforders of which he treats, yet, on a more minute investigation, he is obliged to acknowledge, that Something inexpli- cable ftill remains. This he now wifhes to folve by un- known properties in the water, by confined exhalations, &c. But as the confideration of thefe things belongs properly to the next fection, I Shall here only remark, that there hath not yet been given any fatisfactory ac- count of the origin of epidemic difeafes of what I call the inferior kind, much lefs of the true plague, which Stands above them all, as I have already faid, like the ferpent Python above other ferpents. To what has been quoted from Dr. Lind, I Shall here fubjoin the teftimony of Dr. Clark, who had an oppor- tunity of obferving the epidemic difeafes which raged at Bengal in 1768 and 1769. Thefe were, " the remittent " fever and dyfentery, which begin in Auguft, and " continue till November. During the beginning of " the epidemic, the fever is attended with extreme ma- " hgnity and danger; frequently carrying off the patient in twelve hours; and if not Stopped, generally proves fatal on the third or fourth day. In Auguft the re- " millions are very imperceptible; in Oftober thev " become more diftina; and, as the cold weather comes " on, the fever becomes a regular intermittent At " that time, too, the putrid dyfentery begins to rage " with THE PLAGUE. 35 *' with the fever. Thefe difeafes were very fatal to ma- " ny Europeans, particularly new comers, in 1768. But " in the year 1770, when there was a fcarcity of rice, " it was computed, that about eighty thoufand natives, " and one thoufand five hundred Europeans, died at " Bengal. The Streets were covered with funerals; the " river floated with dead carcafes; and every place ex- hibited the moft melancholy fcenes of.difeafe and " death. During the fickly feafons at Bengal, the un- " certainty of life is fo great, that it frequently happens " that one may leave a friend at night in perfect-health, " who Shall not fuwive next day. There have been fi feveral inftances of perfons who have returned home " in a State of perfect health from performing the laft " duties to a deceafed friend, and have next day been " numbered with the dead. But the cbol, agreeable " feafon, from December to March, is productive of no " prevailing difeafes. The complaints to be met with " are in general the confequences, or remains, of the dif- " eafes of the former period. The complaints which " the Europeans are fubject to in the dry months are, " the cholera and diarrhoea. Fluxes and fevers are then " feldom epidemic ; and, when they do happen, are not " attended with much danger. " At Batavia the rainy feafon is from November to " May, during which time malignant, remitting and " continued fevers and the dyfentery rage with great fa- " tality. Captain Cook, in his firft voyage, arrived " here in October 1779; the whole crew, excepting " Tupia, a native of Otaheite, being in the moft perfect " health. But, in the courfe of nine days, they expe- " rienced the fatal effects of the climate, and buried " feven people at Batavia. On the 3d of December, " the fhip left the harbour. At that time the number " of fick amounted to forty ; and the reft of the Ship's " company were in a very feeble condition. When the " Ship anchored at Prince's Ifland, in the Straits of " Sunda, the ficknefs increafed, and they buried twenty- " three perfons more in the eourfe of about fix weeks. " The Grenville Indiaman, which touched at this ifland "in 36 A TREATISE ON "in 1771, fuffered equally from the malignity of the " air. A few were taken on board, when the (hip Sailed " from Batavia, ill of a malignant fever; which lpread " by contagion at fea, and carried off great numbers. " I vifited feveral in this fhip, when fhe arrived at Uii- " na, who were reduced to mere Skeletons, by the du- " ration of the fever and dyfentery ; both of which were " moft certainly propagated by contagion. " Thofe parts of Sumatra lying immediately under " the line are continually fubject to rain, and the " ground near the Shore is low, and covered with thick " trees and underwood. The heat being intenfe, noi- * &4erable the ia the neighbouring mountains." THE PLAGUE. 6$ vain to deftroy each other, at laft united in a romantic defign of conquering Paleftine from the Infidels; while the Turks, leaving their habitations about Mount Gau- cafus, where, like the vultures of Prometheus, they had for ages remained unfeen and unknown, precipitated themfelvcs upon the Greeks and Saracens, and laftly, as if all hell had broke loofe at once, the Moguls, from the * moft eafterly part of Afia, poured deftrudion upon the countries to the weft, even as far as Ruflia and Poland. All thefe events took place in a few centuries. In 844 the Turks quitted Mount Caucafus, and fettled in Armenia Major. In 1030 they fell upon the Saracen empire, now divided among innumerable chieftains con- tinually at war with each other. Among thefe was one called the Sultan of Perfia, and another of Babylon. The former being worfted, called in the Turks to his afliftance. They fent him an auxiliary army of only three thoufand men ; and from this (lender beginning has arifen the vaft empire of the Ottoman Porte. The three thoufand men were commanded by a general called by the Greeks Tangrolipix, and by the Afiatics Togrul Beg. Being a man of ability, the Sultan of Perfia, by his afliftance, got the better of his adverfary ; but, refut- ing to let the Turks depart, Tangrolipix with his army withdrew to the defert of Carbon it is, where, being joined by numbers of difcontented Perfians, he began to invade the territories of the Saracens. The Sultan of Perfia fent againft him an army of twenty thoufand men, whom Tangrolipix furprifed and defeated, acquiring at the fame time an immenfe booty. The fame of his vidory, and his wealth, procured him bands of robbers, thieves, and blackguards, from all the neighbouring countries; fo that he foon found himfelf at the head of fifty thou- fand. Againft fuch a formidable force the Sultan of Perfia marched in perfon ; but happening to lofe his life in the engagement by a fall from his horfe, his men threw down their arms and acknowledged Tangrolipix to be Sultan of Perfia. The new fultan inftantly thought of deftroying other fultans and potentates; for which purpofe he opened * pafiage 64 A TREATISE ON paflage for his countrymen from Armenia to Peril*. The Sultan of Babylon was the firft vidim ; after which Tangrolipix turned his arms unfuccefsfully againft the Arabians, but afterwards more fuccefsfully againft the Greek emperors. The firft invafion by the Turks took place in 1041 3 and in four hundred and twelve years they became abfolute matters of the empire. Though unfuccefsful at firft againft the Saracens, they prevailed greatly afterwards, and, by the time of the crulades, we find them matters of Palestine, as well as feveral other countries formerly conquered by the Arabs. From the time of their firft invafion, in 1041, we may fay, the war never ceafed; and there is the greateft reafon to fuppofe that the Greek empire would have been overthrown in a very fhort time, had not the crufaders checked their progrefs. The immenfe numbers with whom the bar- barians had now to contend (amounting to no fewer than feven hundred thoufand) threatened with deftruc- tion the newly ereded empire of the Turks; and had it not been for the want of unanimity among the crufaders themfelves, and the jealoufy of the emperors of Con- ftantinople, they certainly would have overthrown it. But, as matters went, all their labour was loft; and they only increafed the general carnage and defolation to an extreme degree. The firft crufade was planned in 1093, publifhed in 1095, and in March 1096 the firft army fet out. In 1097 tney began their conquefls, but foon found it very difficult to keep them. The Turks being at home, and united, had many advantages over foreign invaders ; which the latter endeavoured to counterad by drawing continual fupplies of frefh men from Europe, Thus, for feveral centuries, the weftern part of Afia was rendered a fcene of bloodfhed and defo- lation. When they had contended for fomething mora than two hundred years, Jenghiz Khan, the Mogul, feems to have formed the noble defign of deftroying the whole human race at once, excepting only his own immediate followers. His plan was, to exterminate man, woman and child wherever he went, and to plant the countries with Ins own people. It is impoflible to do jultice to his THE PLAGUE. 6c his exploits. Voltaire, fpeaking of the irruption of the Moguls, fays, that the people fled every where before them, like wild beafts roufed from their dens by other beafts more favage than themfelves. In the Univerfal Hiftory we are told, that he is fuppofed to have deftroyed fourteen millions and an half of his fellow creatures. He died in 1227, and left fucceflbrs worthy of himfelf. Some of thefe proceeded eaftward, and fome weftward. The latter, under the condud of a monfler named Hula- kti, overthrew, in the year 1256, the remains of the Saracen empire, by the taking of Bagdad. The mifera- ble Khalif, coming forth to meet his conqueror, was trampled under his horfe's feet, then fewed up in a fack, dragged through the Streets, and thrown into the river. The Moguls who proceeded eaftward invaded China. The Chinefe refitted with innumerable multitudes, and battles were fought to which thofe of the prefent age are mere fkirmiShes. The foldiers, overcome with thirft, drank blood inftead of water; hundreds of thoufands fell on both fides, while human blood ran in Streams for five or fix miles. At laft the fury of the Moguls was flopped by the ocean ; for, having attempted the con- quest of Japan, their fleet was wrecked, and an hundred thoufand perifhed. Like other great empires, alfo, pre- tenders to the fovereignty Started up, and the whole was parcelled out into a number of little States, which, of courfe, ceafed to be formidable. The decline of the Mogul empire did not reftore peace to the world. The Turks continued their ravages; the weftern nations continued their crufades. England, which became a kingdom in 800, had been ravaged and conquered by the Danes and Normans, and likewife dif- trefled by civil wars. At laft, having emerged from its own difficulties, it began to inflid upon other nations the miferies itfelf had endured. Wales and Scotland became objeds of the ambition of Edward I, who had already fignalized his valour in the crufade. The Welfn were totally fubjugated, arid the Scots overthrown in the very bloody battle of Falkirk, where almoft the whole force of the country was deftroyed. The Scots, K however, 66 A TREATISE ON however, were never totally fubdued. Robert Bruce retaliated on the Englifh in the battle of Bannock-burn, where two hundred thoufand Englifh were defeated by thirty thoufand Scots. But Robert was not contented with aflerting the liberty of his country. Jealous of his brother Edward, he fent him with an army to conquer Ireland. We (hall not doubt of his valour, or of the miferies he inflided, or was willing to infiid, upon the people among whom he came. In deftroying them he deftroyed his own army. They were reduced to the moft dreadful Straits by famine, infomuch that they were obliged to feed upon the moft loathfome matters, their own excrements not excepted. Being now arrived at the beginning of the fourteenth century, we fee that, from Ireland to China, mankind had involved themfelves in one general work of de- ftrudion. Befides the wars, famines had been fo fre- quent, that the eating of one another feemed to be but a common affair. Indeed the hiftory of mankind would tempt one to believe that they thought themfelves brought into the world for no other purpofe but to de- ftroy each other. As far back as the year 409, in the time of the wars of the Vandals in Spain, a dreadful famine took place, which, in 410, reduced many to the neceffity of feeding upon human flefh ; parents devoured their children, and the wild beafts, being deprived of the dead bodies which they ufed to feed upon, but which were at this time devoured by the living, fell upon the latter, and thus increafed the general deftrudion. Such of the Romans as fled into ftrong holds and fortreffes, were in the end obliged to feed upon one another. To thefe calamities the peftilence was added, which did not fail to rage in its ufual manner. Famine and peftilence had alfo ravaged the city of Rome when befieged by the Goths under Vitiges, and under Totila. In this laft fiege the unhappy citizens were reduced to fuch Straits, that they confumed even the grafs which grew near the walls, and were at laft obliged to feed on their own ex- crements. We do not indeed hear, at this time, of any particular inftances of people feeding upon one another; though, THE PLAGUE. 67 4 though, in fuch dreadful emergences, it is fcarcely to be doubted that fome would have recourfe to this terrible expedient in order to allay their hunger. But in the famines which took place during the ravages of the Sa- racens, Turks and Moguls, nothing feems to have been more common. In 1066 a moft grievous famine took place at Alexandria in Egypt, and throughout the whole country. Three bulhels and a half of flour were fold at eighty dinars, a dog at five, and a cat at three. The Vifir, having waited on the Khalif, left his horfe at the palace gate; but, before he returned, the animal had been carried off and eaten. Three men were hanged for this theft, and their bodies ordered to be expofed upon gibbets; but next day they were found picked to the bones, their fleSh having been all cut off and de- voured the preceding night. Bodies of men and women were boiled, and their flefh publicly fold. A violent plague followed, which fwept away the greateft part of the inhabitants. As the hellifh Moguls fpread defla- tion wherever they advanced, fo their retreats were equally formidable. In 1243, having advanced as far as Aleppo in Syria, they found themfelves obliged to retreat, and that for a very odd reafon, viz. that their horfes were not well fhod. This, however, did not hin- der them from deftroying every thing the earth pro- duced, and Stripping every man, nay, every woman, they met, even of their clothes. The confequence was, a terrible famine, fo that people were fain to fell their children for fmall pieces of bread. Such was the condud of men, from one end of the earth to the other, during the interval, if any interval there was, between the plague in the time of Juftinian and that of 1346. The peftilence, which had con- tinually raged in one place or other, now overfpread the whole world. At what time it began to decline we know not ; and, indeed, as the fame defolations and maffacres continued, if thefe had any fhare in its pro- dudion, it ought fcarcely to have declined at all. That there was all this time little or no interval, appears from what Dr. Rufh fays, vol. hi, p. 16$, that between the x-ears $5 A TREATISE ON years 1006 and 1680, that is, in a period of 674 years, the plague was fifty'-two times epidemic all over Europe. Suppofing the intervals between every general infedion then to have been equal, and the plague to have lafted only one year at a time, it muft have recurred once in twelve years. But the intervals were not equal; for the Dodor tells us that it prevailed fourteen times in the fourteenth century ; which gives an interval of lefs than feven years ; and if the peftilence fo frequently over- fpread the whole continent, we may be very fure that it never was out of particular places of it. The Dodor adds, " The State of Europe in this long period is well " known." We Shall alfo confider that of Afia. The empire of the Moguls, which had fallen into decay, revived under Tamerlane; who, following the example of Jenghiz Khan, had the epithet of the deftroying prince bellowed upon him by the Indians, on account of his behaviour in their country. Building his captives into walls with (tones and lime, pounding them by thoufands in large mortars, was his common pradice ; while the Turks, proceeding weftward, wafted every thing with fire and fword ; the christians all the while continuing their mad crufades, and when driven from one place endeavouring to eftablifh themfelves in another. At laft the Turks and Tartars, or Moguls, or rather their emperors, happening to quarrel, the battle of Angora, in Galatia, decided (at the expenfe of fome hundred thoufand lives) the difpute in favour of Tamer- lane ; but, as his empire ended with his life, the Turks foon recovered from the blow they had received ; and, by the taking of Constantinople in 1453, put an end to the terrible commotions which had prevailed in the eaft for fo many ages. The crufades had alfo for fome time been difcontinued, and the world hath Since that time been comparatively in a (late of peace. But, by \o much intercourfe with the Afiatics, efpe^ cially with the countries particularly fubjed to the plague, all Europe had been fo deeply Weded, that the diftemper could not but prevail for a long time, even though it had not been kept up by the almoft continual wars THE PLAGUE. 69 wars of the Europeans with one another, which was too much the cafe. Dr. Sydenham informs us that before his time the plague commonly vifited England once in forty years ; but by this we muft understand a very vio- lent infedion ; for Dr. Rulh tells us that plagues pre- vailed in London every year from 1593101611, and from 1636 to 1649. The author of the Journal of the Plague Year (1665) mentions a visitation in 1656 ; and Mr. Carey, in the beginning of his account of the plague of London in 1665, fays, that the plague was almoft continually among the difeafes enumerated in their bills of mortality; fo that we may fairly conclude it to have been endemic in that city. Now let us fee how Eng- land had employed itfelf. Its kings, as well as many of their fubjeds, had gone to the holy wars, as they called them, and, by continuing in that devoted country where moft probably the peftilence firft originated, it is impoflible to fuppofe that fome of them did not receive the contagion. Having caught the peftilence in the holy war, they came home to diffufe it among their countrymen, and to keep it up by profane wars, I fup- pofe, both foreign and domeftic. Henry VII put an end to a very long and bloody conteft between the houfes of York and Lancafter; but he brought the peftilence along with him, which raged violently during the fifteenth and fixteenth centuries. A moft violent war, for half a century, on the continent of Europe, and civil wars in England, would ftill continue to keep the infedion alive from 1600 to 1648, when a general peace was concluded; and from the ffubfequent (late of tran- quillity, probably, after the violent attack in 1665, it feems to have languifhed and died in England, as a plant in a foil not natural to it. But, though England has fince remained in peace, on the continent it has been otherwife. In the beginning of the eighteenth century, the heroic madnefs of Charles XII feemed ready to confound the north, while the glorious exploits of prince Eugene and the duke of Marlborough appeared equally confounding to France. In the midft of thefe grand atchievments, the peftilence filently 7° A TREATISE ON filently claimed its fhare in the common work of de- ftrudion; carrying off upwards of two thoufand in a week for fome time, in 1709, in the city of Dantzick, and, in 1711, twenty-five out of Sixty thoufand inhabi- tants in Copenhagen. . . The infedion, however, feemed now to be retiring to the place from whence it originally came. In 1666, or foon after, it feems to have totally abandoned the ifland of Britain; with the attack in 1711 it left the weftern countries of the continent next to that ifland ; in 1713, 1714 and 1715 we are informed by baron Van Swieten that it ravaged Auftria ; in 1721, or foon after, it aban- doned France; in 1743 it made its laft attack on Mef- fina; and in 1784 we find it confined to Dalmatia and the eaftern territories, where it has fo long reigned with- out interruption. From the view then which we have taken of the con- dud of the human race, and the confequences of that condud, we may reafonably conclude, that war will pro- duce famine and peftilence, and that after all violent wars a violent peftilence may be expeded, efpecially if the contending parties interfere with thofe nations where it is moft frequent. Another piece of condud by which mankind expofe themfelves to peltilential con- tagions is, the pradice of cooping themfelves up in great cities. Mr. Gibbon, fpeaking of earthquakes, fays, that men, though always complaining, frequently bring mif- chief upon themfelves. " The institution of great ci- " tics (adds he) which enclofe a nation within the limits " of a wall, almoft realifes the wifh of Caligula, that the " Roman people had but one neck. In thefe difaf- " ters-(earthquakes) the architcd becomes the enemy " of mankind. The hut of a favage, or the tent of an :' Arab, is thrown down without injury to the inhabi- tant ; and-the Peruvians had reafon to deride the :' folly of the Spanish conquerors, who with fo much " colt and care ereded their own Sepulchres. The rich " marbles of a palace are dafhed on its owner's head, a c: whole people is buried under the ruins of public or >' private edifices, and the conflagration is kindled and " Pr0Pagated THE PLAGUE. 71 u propagated by innumerable fires neceflfary for the " fubfiftence and manufadures of a great city." In plagues, great cities are unqueftionably as pernicious as in earthquakes; not indeed by reafon of the weight and bulk of the materials, but the confinement of the peo- ple within the fphere of infedion, and their continual expofure to the caufes which prepare the body for re- ceiving it. In fad, it has always been found that plagues begin in cities; and were it not for the multi- tudes that continually fly out of them there can be no doubt that the mortality would be much greater than it is. The intercourfe of many nations with one another, the carrying from one end of the earth to the other of goods capable of bringing with them the infedion, muft alfo be fuppofed a very principal caufe of peftilence; but this laft will be mote fully considered in the next fedion. At prefent we may conclude, that, the pefti- lential contagion having originally fallen upon mankind for their fins, it is ftill kept alive by the fame caufes; and, as far as we can conjedure, thefe fins are, the pro- pensity to murder and deftroy which breaks forth in war; the vanity, pride and luxury which produces great cities; and the fame vanity, &c. joined with avarice, which gives life to commerce. Add to all this the neg- led of the cultivation of the earth, which ought to be the principal bufinefs of man. In confequence of this negled, immenfe trads of it ar,e Still overrun with woods, covered with ftagnant ancj noxious waters, or lying in wafte and now uninhabitable deferts, fit only for ferpents and the moft deltrudive animals. Thus the very climate is changed from what it ought to be ; the elements become hoftile to man in an extreme degree, and the whole fyftem of nature, originally defigned to give life and happinefs to the human race, is, through their own mifcondud, changed into a fyftem of mifery, difeafe and death. The account juft now given of the ways in which mankind bring upon themfelves the plague, and other difeafes almoft equally terrible, is fo conformable to the opinions of the learned Dr. Mead, that I Shall conclude this A TREATISE ON this fedion with a few extrads from his works. Of the fmall pox he fays, that he fuppofes this " to be a plague " of its own kind, originally bred in Africa, and more " efpecially in Ethiopia, as the heat is exceflive there; " and thence, like the true plague, was brought into tf Arabia and Egypt, after the manner above men- " tioned" (i. e. by war and merchandife.) " Now (adds " he) if any one Should wonder why this contagion was " fo long confined to its native foil, without fpreading "into diftant countries, I pray him to confider, that " foreign commerce was much more fparingly carried on " in ancient times than in our days, efpecially between " Mediterranean nations; and likewife that the ancients " feldom or never undertook long voyages by fea, as we " do. And Ludolfus obferves, that the Ethiopians in " particular were ignorant of mercantile affairs. There- " fore when in procefs of time the mutual intercourfe of " different nations became more frequent by wars, trade " and other caufes, this contagious difeafe was fpread " far and wide. But, towards the end of the eleventh " century, and beginning of the twelfth, it gained vaft " ground by means of the wars waged by a confederacy " of chriftain powers againft the Saracens, for the re- " covery of the Holy Land ; this being the only visible " recompenfe of their religious expeditions, which they " brought back to their refpedive countries." Of the true plague he fays, " It appears, I think, very plainly, " that the plague is a real poifon, which, being bred in " the fouthern parts of the world, is carried by com- " merce into other parts of the world, particularly into " Turky, where it maintains itfelf by a kind of cireu- " lation from perfons to goods; which is chiefly owing •{ to the negligence of the people there, who are ftupid^ " ly carelefs in the affair: that, when the conftitution " of the air happens to favour infedion, it rages there " with great violence ; that at ttiat time, more efpecially, " difeafed perfons give it to one another, and from them " contagious matter is lodged in goods of a foft, loofe " texture, which, being packed up and carried into other " countries, let out, when opened, the imprifoned feeds " of THE PLAGUE. 73 * of the contagion^ and produce the difeafe whenever the " air is difpofed to give them force ; otherwife they may " be diflipated without any considerable ill effeds. The " air of* our climate is fo far from being ever the original " of the true plague, that moft1 probably it never produces " thofe milder infectious diftempets, the fmall pox and " meafles: For thefe difeafes were not heard of in " Europe before the Moors had entered Spain ; and, as " already obferved, they were afterwards propagated and ** fpread through all nations, chiefly by means of the " wars with the Saracens. The fweating ficknefs was " molt probably of foreign original. It began in the " army with which king Henry VII came from France, " and landed in ^ales -, and' it has been fuppofed by " fome to have been brought from the famous fiege of " Rhodes, three or four years before* as may be colleded " from one place of what Dr. Keyes fays in his treatife " on the difeafe. We had here the fame kind of fever " in 1713, about the month of September; which was " called the Dunkirk fiver, as being brought by our " foldiers from that place. This, probably, had its origi- " nal from the plague which broke out at Dantzick a " few years before, and continued fome time among the " cities of the north." I now take leave, for the prefent, of this fubjedj which exhibits the condud of mankind in fuch a dif- agreeable view. Some, like M. Millot above quoted, may be apt to fuppofe that many of the accounts are exaggerated. But it is evident, that in our days it is impoflible to determine any thing to be afalfehood, faid to have happened in former ages, which is not abfolutely contradidory to reafon. Every one of the accounts in- ferted in this fedion has found a place in the works of historians reckoned authentic, particularly in the Uni- verfal Hiftory. All who believe the New Teftament muft certainly believe, from the words of our Saviour, that extraordinary things were to happen'in the ages fubfequent to his appearance. Can we then difcredit the relations of thofe historians who inform us that ex- traordinary things have happened ? Modern hiftorians. L making 74 A TREATISE ON making their own judgments the infallible meafure of vvifr dom, and the ftrength of nations now exifting the ulti- mate meafure of human power, have endeavoured to turn into ridicule every thing which does not preciiely accord with thefe two. In this the French are particu- larly culpable ; accounting every thing to be incredible which exceeds the power of modern France to accom- plish, though they certainly do not know even the extent of this power. Of fuch fcandalous vanity we have a notable inftance in the works of prefident Goguet, who positively determines that the walls of ancient Ba- bylon, the pyramids of Egypt, and all the wonderful works of Semiramis, Nebuchadnezzar, &c. were not equal to the canal of Languedoc made by Louis XIV !. SECTION III. Of Difeafe in general.,-^-The nature of the Plague as a Difeafe confidered.—Of Contagion.—Whether the Plague is really Contagious or not.—Medical Hiflory of the Dif- temper.—Inquiry into its Immediate Caufes, and whether an approaching Plague is indicated by any vifible Signs. HITHERTO we have confidered the origin of the plague entirely in a moral point of view. We have feen, that, in conformity to the general opinion of mankind, it may reafonably be fuppofed to have been inflided upon mankind, the Jews particularly, for their tranfgreflions; that, having been once introduced, it has been perpetuated, and fpread from nation to nation, and that in proportion to the degree of immorality of a certain kind prevailing through the world. From this it is naturally to be inferred, that, were the human race to live at peace with one another, to difperfe them- felves over the face of the earth for the purpofe of improving it by cultivation, and were they to be con- tented with what the produce of each country affords, there would be no plague among them. But we know that THE PLAGUE. 75 that fuch a reformation is not to be expeded, and we muft take the world as we find it. The queftion then is, By what means Shall individuals fecure themfelves from being deftroyed by a plague which fliall happen to invade any country; or how fhall a perfon, already infeded with it, be reftored to health ? For this purpofe let us begin with considering the nature of difeafe in general, and of the plague particularly. As to difeafe in general, phyficians have differed very considerably in their definitions; and, though many have been given, few feem to be unexceptionable, that of Dr. Fordyce feems to be among the cleareft and moft expreffive. " Difeafe (fays he) is fuch an al- " teration in the chemical properties of the fluids or " folids, or of their organization, or of the adion of " the moving powers, as produces an inability or diffi- " culty of performing the fundions of the whole or any fome perfons have accidentally been brought to life, even after interment, by •• the rude motion produced in facrelegious attempts to wreft riogs or brace- •• lets from the apparently dead body." Several furprifing inftances of the recovery of perfons fuppofed to be dead* even of the plague, are given by Fabricius Hildanus; to one of which Dr. Fother- gill feems to allude in the above quotation. Hildanus relates, that in the year 2357, when the plague raged violently at Cologne, a certain noble lady, by name ReicBmutb Ado/eh, being feized with the difeafe, was thought to have died, and was buried accordingly. Her hufband, out of affiidion, would not take off her wedding ring, which (he happened to have on her finger. The undertakers being acquainted with this circumftance, next night came to the church where Hie was buried, opened the fepulchre, and prepared to take off the ring ; when to th'eir utter afto.uifhment fhe began to raife herfelf up in the coffin. Struck with confirmation they fled in the utmoft haile, leaving to the fortunate lady the lanthern with which they lighted themfelves to the church, and by means of which fhe now found out where the was, and after being come to herfej/, returned to her own houfe. Here being known by her voice, and the ring the wore, Uie found admittaace, and by means of a generous diet gradually regained her health ; bringing her hufband afterwards three children! and fur.iving the ac/dent many years. A 7« A TREATISE ON 7. When the organization of the body is injured, the adion of the natural powers themfelves occasions unea- iinefs, and increafes the difeafe. The cure then is, to fubftitute inftead of the natural power, as far as pof- fible, the adion of fome other power till the organiza- tion is reftored ; after which the natural power muft be again allowed to ad, or a difeafe of another kind will take place. This may be exemplified in a confumption of the lungs; where, that part being very much difor- ganized, pure air renders the difeafe worfe ; and the fick are relieved by mixing with the common atmo- fphere fuch kinds of air or vapour as would prove per- nicious to people in health. But, fuppofing this method to be fuccefsful, and the confumption to be entirely removed, it is plain that the ufe of the pure atmofphere muft be refumed, or the impure air would bring on a difeafe in the fame manner as on a healthy perfon. 8. The body is wafted in the natural operations of life; part of it pafling off with the vapour of the breath, part by infenfible perfpiration, &c. Hence it naturally tends to diforganization and death, unlefs the wafte be repaired. 9- This natural wafte of the body is repaired, and health kept up, by the food and drink taken into the Itomach. 10. Hence* LentUl^ho^Z 7 W7?!f,kIWe '"S °f * Woman of the n*m* of NIcollt fffir&^&ssi ^^sjsra^s sr<£T. into a ^er^^^^^ means of efcaping, or mricarin rJerfSf from ?H *? d,d',c°uld fte *"* any which fhe was o^n^^n^dit^heap °u *?« bodies wi,h of no avail, and, in the mean ?m^ I * u"*"1 a"y houfe' her crics were ^^(ktwufytorm!n?^VtThL^t\fCa n° nourifl""«« for four fituation. the pit beingopenStoZ,7* twen.ty-f°U' hours in this dreadful moft endeavours i„ calfin P fo?VmiZl f °theI perf°n* fte exerte<* her ut- fioodround. Bein72 up .KSrEV' culation goes on as already defcribed. The two ventri- cles of the heart, and all the veins throughout the body, are furnifhed with a kind of valves, which allow the blood to proceed in the way of circulation, but prevent its returning in a contrary diredion. 15. The lungs, through which all the blood in the body pafles, receive likewife the air which we draw in every time we breathe. They confift of two large bo- dies called lobes; from their Situation called the right and left. The air is conveyed into them by the wind- pipe, called alfo the trachea, and the afpera arteria. On entering the cavity of the breaft, the wind-pipe divides into two large branches called the bronchia; one of which goes to the right and the other to the left lobe of the lungs. By the further divifion and fubdiviijon of M thefe fo A^ TREATISE ON thefe veflels the lungs are filled with an innumerable multitude of little tubes, terminating in exceedingly minute bladders or cells, which are the final receptacles of the air fucked in when we breathe. Each ot thefe cells is furrounded with a kind of network of blood-vef- fels exceedingly fmall, and confiding of very thin mem- branes ; fo that, in parting through the lungs, the blood is expofed as much as poflible to the adion of the air. 16. It is a matter of great importance to find out what is the ufe of this expofure of the blood ; and great difputes have taken place concerning it. In for- mer times it was fuppofed that the blood received from the air a vitalJpirit, without which it would have been totally incapable of performing its offices in the body. Later phyfiologifts endeavoured to explode this notion^ Dr. Hales particularly, by Shewing that the circulation of the blood through the lungs might be continued by inflating and contrading them alternately by the fumes of burning brimftone, endeavoured to prove that the ufe of the air was only to give the lungs an opportunity of dilating and contrading alternately, by which means principally he thought the circulation might be carried on. This continued to be the moft common hypothefis as late as the time of Dr. Huxham. It was however thought alfo that by the comprefiion of the air the blood was altered in its texture, its bulk, &c. Accord- ingly Dr. Huxham tells us in the preface to his treatife on air and epidemic difeafes, that •* air fit for refpiratioa *' ought neither to be too hot, nor very cold ; for the " ufe of the infpired air is to temperate the blood, which " would otherwife grow too hot, and putrefy, as is cvi- " dent from the experiment of the moft excellent Boer- " haave made in a hot houfe ; for, if the air is more hot, " or even equally hot, as the blood of any animal, it cer- " tainly foon dies."* 17. The modern difcoveries in the compofition of,air, have tended greatly to elucidate the ufe of this fluid in the lungs, and its adion on the blood in refpiration* Dr. * This certainly dees not hold good if we fuppofe the heat of the atmoft phere to be indicated by a thermometer; for we are affined that animals can live m a beat much fuperior to that which raifes the mercury to 97. THE PLAGUE. 83 Vr. Prieftly firft determined it to be what he terms a phlogifiic procefs, i. e. a procefs by which the parts of the blood no longer proper to be retained among the reft, or at leaft fome of them, are carried off. Tnzx fomething is carried off either from the lungs themfelves, or from the blood circulating through them, is evident; for the air which is taken into the lungs in a dry ftate, comes out of them extremely moift, and loaded with vapour. An elfential change is alfo made in the nature of the air it- felf; for it now aflfumes in a great meafure the nature of what has been called fixed air, or the fume of char- coal, or fermenting liquor, and thus becomes unfit for being breathed a fecond time. This change is made by the addition of fome terreftrial fubftance to the pure atmofphere, which the latter volatilizes and carries along with it.* 18. But, whatever may be carried off from the blood, during its paflfage through the lungs, fomething is cer- tainly added to it, for the blood in the pulmonary artery is of a dark red, but when it has undergone the adion of the air in the lungs, and returns by the pulmonary vein, it is then of a bright fcarlet, which colour it retains through all the arteries of the body, but lofes it on its return through the veins. This fcarlet colour is com- municated to blood in all cafes when expofed to the air; and Dr. Prieftley has obferved that it is aded upon by the air even through a bladder; much more then muft it be fo through thofe very thin membranes which form the coats of the fine pulmonary veflfels. What this fubtile matter is which the blood receives, Shall be afterwards inquired into; at prefent it is fufficient to take notice that it is abfolutely neceflfary, for the pur- pofes of life, that the blood Should pafs through the lungs: for, as Dr. Huxham obferves, " we fee neither " nutrition, nor the motion of the mufcles, performed by * The difcoveries of modern chemifts have determined that the aerial fluid* termed fixed air or carbonic acid, and which is nearly the fame with the va- pour arifing from fermenting liquor, and is alfo largely contained in the fume •f burning charcoal, is Hot a fimple but a compound fubftance ; one part con- fifting of the pure part of the atmofphere, or oxygene, the other of real char- coal. The proportions, according to M. Chaptal, are izj0288 parts of ehar* ►03! to 56,687 of oxygen. 84 A TREATISE ON " by any blood that hath not pafled through the lungs; " this is obfervable from the coronary arteries* to the «• ultimate ramifications of the aorta." As the previous circulation of the blood through the lungs therefore is abfolutely neceffary to the growth and life of the body, and as the blood certainly receives fomething from the air, we muft account this a proof, and no inconfiderable one, that the air contains a vitalfpirit, which it imparts to the blood in the lungs. But, before we proceed farther on this fubjed, it is proper to take fome notice of 19. The nerves. Thefe, which conftitute fuch a re- markable and important part of the human body, are white cords, of a foft pulpy fubftance, defended by a tough fkin which goes along with them as far as they can be traced. All the nerves either originate from the brain, or terminate in it. The former dodrine hath been generally adopted, and in conformity to that doc- trine the following account of the nerves is laid down. The brain is enclofed in the cavity of the fcull, but not without the intervention of two membranes, called the dura and pia mater, to prevent injury from the hard bones, as well as for other purpofes. The brain is di- vided into two lobes, the right and left. It is compofed of two different kinds of fubftance, the outermoft called the cortical, the innermost the medullary Substance; the latter feems compofed of fine fibres. The whole of the medullary part of the brain terminates in a fubftance called the cerebellum, very much refembling the brain, but fmaller. The cerebellum terminates in another fubftance refembling the medullary part of the brain, called the medulla oblongata. The cerebellum lies in the back part of the head, and the medulla oblongata under it. The latter terminates in the fpinal marrow, extend- ing from the lower and back part of the head to the lower extremity of the back bone, and is enclofed in the hollow of that bone. The nerves proceed from thefe four fubftances, viz. the brain, the cerebellum, the me- dulla oblongata, and fpinal marrow. As they pafs to all parts TilfThe "aT °f ^e ve(rds by which the heart itfelf is Applied with blood. iftele come from the aorta by the circuitous way of the luags. THE PLAGUE. 85 parts of the body they accompany the arteries, dividing with them into innumerable Small branches ; but they do not return with the veins ; fo that they feem not to contain any fluid which goes and comes, or which circu- lates like the blood. The nervous fluid, if any fuch there be, feems to move conftantly one way, either to the brain or from it. 20. Hitherto we have noticed only things which are evident to our fenfes, and which the induftry of anato- mifts has abundantly evinced; but now our fubjeft ren- ders it neceSTary to ftep afide a little into the obfcure regions of theory and conjedure. The mufcles, as we nave formerly faid, are the flefhy parts of the body ; and by them all the motions of the body are performed. The flefh is distributed into diftind portions, each of which is enclofed in a membrane belonging to itfelf. Each of thefe portions is a mufcle, and each mufcle has a branch of an artery and the branch of a nerve belong- ing to it. On both thefe the adion of the mufcle de- pends ; for, if we cut the nerve belonging to a mufcle, it immediately lofes all power of adion ; and if we cut the artery which accompanies the nerve, it does the fame. As therefore the blood is found to receive fome- thing from the air, and as it lofes this when pafling through the arteries, and as the nerves lofe their power when the communication with the blood is cut off, it feems extremely probable, that what is imbibed by the blood in the lungs is taken up by the fine ramifications of the nerves, and is no other than the immediate prin- ciple of life and fenfation. Thus we will eftablilh a dodrine diredly oppofite to that commonly received ; for, inftead of fuppofing that the nerves originate from- the' brain, we are now led to fuppofe that they terminate in it. Inftead of fuppofing that the fenfations originate in the brain, we will be led to fuppofe that every fenfa- tion originates in the organ appointed for that fenfation. Thus we are confcious that our eyes, not our brain, are the parts of our body which immediately perceive the light; our fingers, or any other parts of the body, feel what is applied to them; and of confequence we have reafon 86 A TREATISE ON reafon to believe that the animal fpirits, nervous fluid, of whatever we pleafc to call it, proceed from the furface of the body inwards to the brain, not outwards from the brain to the furface of the body. The brain itfelf feems to refemble a large colledion or refervoir of water, in which the fenfations, like fo many fmall Streams from every part of the body, unite, and in which our intellec- tual faculties refide in a manner totally inexplicable by us. Thus far it feemed neceflfary to theorife, in order, to form fome idea, however obfcured, of the connexion between the nerves and our fenfitive and intelledual, or, if we pleafe to call them fo, our fpiritual faculties. 21. In confequence of this very intimate connexion between the blood and nerves, it is eafy to fee that any injury done to the one may very greatly affcd the other ; and that a very flight, nay, to us imperceptible, change in the organization of either, may produce the moft grievous, and even incurable diforders throughout the whole body, or in any particular organ. Let us now confider a little farther the blood-vefifels. 22. It hath been a queftion, whether in the ftrudure of thefe veflfels nature hath obferved an exad proportion. For inftance, if the blood pafles by a kind of ftarts through four cavities, as we are aflfured that it does,, it feems natural to fuppofe that thefe four Should be ex- adly equal. This, however, hath been denied; and fome, from its accommodating the human frame to their theory, have fancied that they faw the ufe of fuch difproportionate work. Dr. Huxham expreflfes himfelf in the following words: " Nor doth the air only refrige- " rate the blood, but, by preventing its too great ebul- " lition, and condenfing it, hinders it from burtting the " veflels. This indeed is of exceeding great importance, " if, with the very learned Helvetius, we fuppofe the capa-r " city of the right ventricle of the heart to be greater " than that of the left, and that the pulmonary arteries " are larger than the correfpondent veins ; for it thence " follows, that the blood ought to be confiderably con- " denfed by the infpired air, that an equal quantity of '•* blood may be received, in one and the fame time, by '."'the THE PLAGUE. 8? " the pulmonary veins and left ventricle of the heart, " that is thrown off from the right ventricle, and " through the more capacious pulmonary arteries. This ** indeed many deny, aflferting quite the contrary. It h " neceSTary, however, that the aorta Should receive as " much blood from the left ventricle of the heart, as is " thrown off from the right ventricle through the pul- " monary artery; and that in the very fame and equal " time, or a fatal deluge would foon overwhelm the " lungs, becaufe the contradion of each ventricle is " made at one anil the fame time; we always find " therefore the aorta and pulmonary artery, in a natural *' ftate, equal on this account; alfo the capacity of the *' ventricles ought to be equal, that they may receive, " in one and the fame fpace of time, equal quantities of " blood," &c. If any thing farther is neceSTary upon this fubjed, we may ftill obferve, that if the blood were at all condenfed by the air, it would be fo unequally, becaufe the air is at fome times much colder than at others; and thus the difproportion of the cavities of the heart to one another could not fail of producing the moft difagreeable if not fatal effeds. We often fee what terrible confequences enfue upon the enlargement of any part of an artery near the heart; and thefe would, fometimes at leaft, be felt by every individual.* It is true, indeed, that this objedion will in fome de- gree hold, even though we fuppofe all the cavities of the heart * But there is a ftill more egregious blunder, and this the more furprifing as it has been very general among phyfiologifts, viz. that when an artery branches into two the capacity of the branches taken together is greater than that of the trunk. This would make the whole arterial fyftem one continued mneurifm,* and, inftead of promoting the circulation of the blood, would in the moft effectual manner prevent it. In what manner an error fo extraordi- nary In its nature could pafs the mathematical phyficians of the laft century, I cannot imagine; but certain it is, that, in the year 1780 or 1781, the Edin- burgh College were fchooled on this fubject. by one of their own ftudents named John Theodore Vander Kemp, a Dutchman. This gentleman found, by accurate menfuration, that when an artery divides, if the diameters of the two branches are made the two (horter fides of a right-angled triangle, the diameter of the trunk will be the hypothenule; and thus, as the areas of cir- cles are to one another in proportion to thefquares of their diameters, the fum of the areas of the two branches will be equal to the area of the trunk. On looking into Blumenbach's phyfiology, 1 find the fame remark. * An aneurifm is a preternatural enlargement of an artery. The blood fiagnates in that place* and at length eats through the flefh and (kin. 88 A TREATISE ON heart to be equal, and the capacities of the blood veflels to be perfedly uniform throughout the whole body. For, if we fuppofe the blood to be at all condenkd in the lungs by the coldnefs of the atmofphere, it muft un- doubtedly follow, that while parting from them ltoccu- pies lefs fpace than before it arrives at them. Hence the pulmonary vein, the left auricle of the heart, the left ventricle, the aorta, and all the reft of the arteries for a confiderable way, muft be comparatively empty, even though they receive as much fluid as fills the vena ca- va, right auricle and ventricle of the heart, and pulmo- nary artery. The equality which ought to prevail in the fyftem, and which indeed cannot be difpenfed with, can only take place in thofe remoter branches of the ar- teries in which the blood has reaflfumed its former ftate of dilation or rarefadion. 23. If we consider this matter attentively, we Shall find it not a little myfterious. Every time we breathe out the air we have fucked into our lungs, a confiderable quantity of moift vapour is breathed out along with it; but it has been proved by undeniable experiments that the emiflion of aqueous vapour from any fubftance cools it in proportion to the quantity of vapour emitted. Every breath we draw, then, cools the lungs, and confequently the blood, to a certain degree, and, as the number of times that we breathe in a day is exceedingly great, the cold produced by the evaporation ought to be in proportion. But we fee that, notwithstanding all this cooling, whether we breathe cold air or hot air, the temperature of the body remains ftill the fame. The air then, though conftantly carrying off the Jieat of the body, does not cool it in the leaft by its action on the lungs. The only poffible way ©f folving this apparent contradidion is, by fuppofing that the air, when ading upon the blood in the lungs, leaves precifely as much heat as it carries off, and therefore, though we breathe ever fo long, we cannot by this means become either hotter or colder. 24. To illuftrate this fubjed, we might now enter into an inquiry concerning the origin and caufe of animal THE PLAGUE. S9 . animal heat; but this will be touched upon hereafter. We Shall here only take notice that the heat of the body is almoft univerfally allowed,to proceed from the lungs. It has likewife been demonftrated, that the air does in fad contain an incredible quantity of heat, even when it appears to us to be extremely cold. A certain pro- portion of this heat is feparated from it every time we breathe; and if, either by the mixture of other fluids with the air we breathe, or by any change in the organi- zation of the body itfelf, a greater or fmaller proportion of heat Should be communicated to the blood, difeafe muft enfue. 25. To fum up then what has been faid concerning the blood and nerves: . The whole mafs of fluid pafles from the right fide of the heart to the lungs. In the lungs it receives from the air fomething* neceflary to the fundions of life and fenfation, and purifies itfelf from thofe matters which might prove pernicious. From the lungs it pafles to the left fide of the heart, and thence through the whole body. In its paflfage through t£e body, it is accompanied with nerves, which, taking up from the arterial blood that vitalfpirit received from the air, convey it to all the organs of motion, of fen- fation, and to the brain, where the whole powers of perception being united form our intellectual faculties, and, as far as our fenfes can perceive, the human fpirit itfelf. The blood, thus deprived of its fpirit, is colleded from all parts of the body by the veins, and returned to the right fide of the heart, from whence it is again fent to the lungs, and the procefs carried on as before. This hypothefis concerning the peculiar fundion of the nerves I firft inferted in the Encyclopaedia Britan-« nic a, fecond edition, under the article Blood, in the year 1778. It has been Since continued in the third Scots edition, and from thence into the Irifh and American editions. 26. It has already been obferved, that the body is fubjeded to a continual wafte. One fource'of this wafte * It feems now to be proved beyond a doubt that this fomething fo long un- known is that fluid called by Dr. Prieftley' dephlogiflicated air* and *f Lavoifier exygsn. N 90 A TREATISE ON wafte is the breath, by which a confiderable part pafles off in vapour. A great quantity alfo pafles oft by the pores of the fkin; frequently in a perceptible liquid called fweat, but oftener in an invifible vapour from all parts of the body, called infenfible perfpiration. The lat- ter has been thought to be the great fource of wafte to the human body; and it is certain, that if any perfon in health fc>e weighed when he rifes in the morning, he will be found considerably lighter than when he went to bed. The lofs of weight in this cafe proceeds not only from the pores of the fkin, but from the lungs; but though phyficians have made a general allowance for both thefe, I have not heard of any experiment by which we can determine how much pafles off by the one, and how much by the other, nor indeed does it appear eafy to make fuch an experiment. Galen plainly overlooks the perfpiration from the lungs entirely. " This excremen- " titious vapour (fays he) is expelled through fmall ori- " fices,, which the Greeks call pores, difperfed all over " the body, and efpecially over the fkin, partly by fweat, " and partly by infenfible perfpiration, which cfcap^ " the fight, and is known to few." Sandorius, and the fucceeding writers, have claflfed both together indifcri- minately; allowing the difcharge to be lb great, that if eight pounds of aliment be taken in, five of them pafs off in this manner. In a fyftem of anatomy, publifhed at Edinburgh in 1791, the author fays, that the dif- charge by the fkin " is even much larger than this (the •* difcharge from the lungs we may fuppofe) Since it " not only throws off a quantity of the aliment, but " likewife what is added to the blood by inhalation, " which, entering often in a very confiderable quantity, " is thus again expelled." The fame author likewife fays, that the " perfpirable matter from the fkin is prin- cipally water," and that it iflbes in fuch quantity as to be feen in fubterraneous caverns evidently flying off from the furface of the body like a denfe vapour. But other phyfiologifts, particularly Dr. Blumenbach, inform us, that the matter of infenfible perfpiration is quite flmilar to the difcharge from the lungs, particularly con- taining THE PLAGUE. 9* taining a great quantity of fixed air. The fame ac- count is given in Chaptal's chemiftry, on the authority of Meflrs. Milly and Fouquet. This may be looked upon as a valuable difcovery, efpecially in conjundion with that related by Drs. Beddoes and Girtanner, viz. that the flefh of animals contains a quantity of oxygen. Dr. Girtanner obtained a quantity of this air from the raw flelh of animals, and fays that it may be repeatedly ob- tained by exposing the flelh to the atmofphere, and distilling with a heat of 60 or 70 degrees of Reaumur's thermometer (fomething below that of boiling water.) Hence it is natural to conclude, that, as the difcharge from the lungs purifies the blood from its ufelefs parts, fo does the infenfible difcharge from the fkin purify the folid parts from thofe particles which are no longer ufe- ful. The probability of this alfo becomes greater by considering, that in difeafes, when the quantity of mat- ter to be thrown off is very great, the fkin becomes foul, the teeth furred with black fordes, &c. all which difap- pear as foon as the quantity of the offenfive particles is reduced to its natural Standard. As to any confiderable quantity of aqueous vapour being difcharged this way, unlefs in cafe of fweat, it does not feem probable; for in fuch a cafe our clothes would always be moift; and in the night time the accumulation of moifture would certainly be perceptible. The fweat is entirely of a dif- ferent nature from the infenfible perfpiration, and blood and even fand has been known to iflue through the Ikin along with it. (See the Anatomical Syfilem above quoted.) 27. This very confiderable wafte of the body is re- paired by the aliment taken into the ftomach. In the mouth it is mixed with a confiderable quantity of the liquid called faliva, and in the ftomach with another called the gaftric juice, with which that organ always abounds. From the ftomach it pafles into the intef- tines, where it is mixed with other two fluids; one called the pancreatic juice, the other the bile. This laft is of a yellow colour, and is fometimes produced in enormous quantities, infomuch that Dr. Wade, in his account of the fevers in Bengal, mentions fome patients who have 92 A "TREATISE ON have voided by -Stool half a gallon of bilious matter in one: day. 28. In -the ftomach principally the aliment undergoes a certain change called digeftion-, by which it becomes capable of being converted into the fubftance of the body. Much has been inquired and difputed, to no purpofe, about the nature of this change, and how it is efLded One party has declared for attrition; a fecond for putrefaction; a third for heat; a fourth have fuppofed that our meat was digefted by chewing ; as if, like the lobfter, people had teeth in their ftomach ! and, laftly, fome learned moderns, after much pains and trouble, have found out that it is digefted by fohition. Dr. Moore has fummed up the difcoveries concerning digeftion in the following words : "The food, being previoufly " divided and blended with the faliva and air by mafti- " cation, (chewing) is fwallowed, and meets in the fto* " mach with the gaftric juice, whofe diflblving power, " affifted by the natural heat of the place, is the princi- " pal agent in digeftion. The procefs is completed by " the pancreatic juice and bile, the nutritious parts of " the food being by this procefs converted into chyle " for the fupport of the body, and the grofler parts " thrown out.* 29. The infice of the ftomach and inteftines are full of the mouths of innumerable fmall veflfels, which con- tinually fuck up from the aliment, as it pafles downwards, the finer parts, in form of a white liquid, called chyle \ and from the whitenefs of their colour the veflels have the name of latleals, from the Latin word lac, milk. After pafling-through the fubftance of the ftomach and inteftines, and running along the membrane called the mefentery, to which the inteftines are attached, the lac- teals unite in a large refervoir called the thoracic duel; and this again opens into a large vein on the left fide, called the Jubclavian, which conveys the blood from half the upper part of the body ; fcon after terminating in the vena cava, by which the chyle is conveyed to the heart, thence to the lungs, and fo on in the common courfe * Moore's Medical Sketches. THE PLAGUE. 93 fourfe of circulation. The converfion of the chyle into blood is called the procefs of fanguification. 30. The blood, thus formed out of the aliment we fwallow, is not one uniform fluid like water, but com- pofed of three diftind fubftances ; one, which gives it the red colour, and feems to be compofed of little round globules; another, quite colourlefs, but of a vifcid na- ture, and which very foon coagulates, called the lymph; and a third, of a yellowifh colour, and retaining its flu- idity much longer, called the ferum. A remarkable property of this laft fluid is, that air can ad through it upon the blood; for Dr. Prieftly found that a portion of black blood affumed a bright, florid colour from the air, even though covered with ferum an inch deep. When blood is drawn, the red globules are detained by the lymph which coagulates, and both together form the red mafs called eraffamentum; the ferum remaining fluid, and retaining its name. 31. Befides thefe fluids, the blood either invifibly contains, or is capable of being converted into, a great many others ; for all the fluids in the body arefeparated from it, and all of them, the bile^ only excepted, from the arterial blood, before it has loft that portion of its fpirit which it imbibes from the air. When a fluid is to be fecreted, fometimes it is done only by an infinity of fmall veflels branching off from the arteries, and de- pofiting the liquids which pafs through them in particu- lar places; and fuch are the fluids which moiften the infide of the body, and which are carried off by the breath, or by fweat. But this feparation does not by any means hinder the artery from terminating in its ufual way in a vein, for in no cafe is the whole, fubftance of the blood converted into any other liquid ; all of them appear to be contained in it. But the greatefl number of fluids are feparated by means of certain fubftances called glands. Thefe are fmall round or oval Shaped bodies; each of them enclofed in a membrane or fkin which Separates it from the other parts, and each fur- nished with a fmall tube called the excretory duel, through which the liquor feparated in the gland pafles to its 94 A TREATISE ON place of deftination. Each gland has alfo an artery and nerve, and a vein to bring back the blood after it has parted with the fluid intended to be feparated. . The bile is feparated in the liver from the blood of a large vein called the vena portarum, formed by the union of fome of the veins of the inteftines and mefentery. This vein branches out through the liver like an artery, termi- nating in other veins, which at laft bring back the blood to the heart. m 32. As the human body is thus furnifhed with an apparatus for feparating and carrying off, it is alfo fur- nifhed with one for abforbing or taking in. All the inward parts o£ the body are moift; and the moifture is furnifhed by the fmall veflfels above defcribed, and which feparate part of the lymph from the blood. By fuch continual feparation the cavities of the belly, breaft, brain, &c. would foon be filled with liquid, were not fome means provided for carrying it off as faft as it is formed. The means in queftion are a fet of fmall veflfels called lymphatics. Thefe " arife from the internai " furface of the breaft, belly, and every cavity of the " body ; they alfo overfpread the whole external furface *' of the body, and large lymphatic veflels are ufually tc found clofe to the large blood veflels of the extremi- *' ties, befides thofe fmall fuperficial ones which lie " above the mufcles in the cellular membrane (the fat " or rather the membrane containing it.) The large " vifcera generally have two fets of lymphatics, one " lying on the furface of the vifcus, and the other " accompanying the blood veflfels belonging to it. The tc faculty of abforption, though refufed to the lymphatics, " was afcribed by many anatomists to common veins, " and this opinion continued to prevail in fome degree* *c until Hunter and Monro totally overturned it, *£ exploding at the fame time the notion that any of the " lymphatics are continuations of arteries, and eftablifh- " *;ng, beyond a doubt, that all .ire abforbent veflels."* All the lymphatics terminate in the thoracic dud ; fo that the liquid feparated by the exhalant arteries (fo'the veflfels * Moore's Medical Sketches. THE PLAGUE. 95 veflfels are termed by which that fluid is feparated) is again mixed with the blood, and again performs the fame offices. We have now taken a review of the feveral parts of the human body, flight and fuperficial indeed, but fuch as the limits of this work would allow, and fufficient to furniSh to thofe entirely unacquainted with medical matters fome general ideas on the fubjed. We have feen that the body, in general, confifts principally of four great parts, the blood-veflfels, the lymphatic vefTels, the nerves, and the mufcles. Befides thefe we enumerate the glands and membranes; the former being nearly allied to the blood-veflfels, the latter apparently to the nerves. The bones, havingno concern with our prefent inquiry, are not taken notice of. The ftomach and inteftines, being principally compofed of mufcular fibres, nerves, and blood-vefTels, muft be confidered as belonging to thefe departments. Each of thefe large divisions has obtained the name of fyfiem ; and even the fubdivifion of the blood-veffels into arteries and veins. Thus the arteries ef the body, taken colledively, are called the arterial fyf- tem ; the veins the venous fyfiem; the brain and nerves the nervous fyfiem; the mufcles the mufcular fyfiem; the lympha- tics the lymphatic fyfiem; and the glands the glandular fyftem; &c. Thefe appellations have beengiven for the fake of dif- tindnefs and perfpicuity, but they have had a bad ten- dency, lnfignificant difputes have arifen concerning the fuperiority of one fyftem to the other, and which is to be accounted the primum mobile of the body. By obferving alfo the general ftrudure of the body in a more full and ample manner than that of the parts which compofe it, phyficians have been apt to generalize too much in their theories, and to fancy that from a few obvious laws they might be able to explain the phenomena of difeafe in almoft every poflible variety. To illuftrate this, let us take the blood for an example. This to fight appears an homogeneous fluid ; and Boerhaave and others have afcribed difeafes to fome defed or bad quality of the blood. But this fluid confifts of three parts, each, as far as we can perceive, eflentially diftind from the other ; 96 A TREATISE ON viz. the lymph, ferum, and red globules. As each of thefe happens to be difeafed, the cure muft be different; or if two happen to be. difeafed, the medicines muft ftill be varied. But, befides thefe general difeafes ar.fing from what, like the blood, is common to the whole body, each component part of the body has an arterial fyftem, a venous fyftem, a nervous and lymphatic fyftem, &c. belonging to itfelf; all of which, though dependent on the body at large, have yet laws of their own, in confequence of which any one of them may be confiderably difeafed without much affeding the general fyftem; and this constitutes what is called local difeafe. Again : The parts of the body are fo conneded with one another, that the difeafe of one may fhow itfelf in another; or it may affcd the whole body in fuch a manner as to produce a general difeafe ; though Dr. Rufh confiders this laft, at leaft from injuries of tlie vifcera, as a rare ocqurrence ;* but we certainly know that general difeafes are very often followed by evident difeafes of particular organs; and in thefe cafes it-is im- poffible to fay whether the general difeafe did not begin, though imperceptible to us, in that very organ in which we fuppofe it to terminate when the local difeafe was come to fuch an height as to be evident to our fenfes. In fome cafes it is plain that local injuries will bring on moft violent difeafes of the whole fyftem. Thus a local inflammation of the end of one of the fingers, by phy- ficians called a paronychia, has been known to induce a moft violent fever, nay, even to occafion death. Thefe violent fymptoms end as foon as the fuppuration is completed ; fo that, were it not for the exceffive pain of the inflammation, we might be apt to fuppofe that the fever terminated in the fuppuration, whereas it evi- dently was occafioned by the local difeafe, or the ten- dency of the part to fuppurate ; the pain and inflam- mation being neceflfary preliminaries. Again : When an intermittent fever is faid to terminate, or to be fol- lowed, by a hardnefs of the liver, we do not certainly know whether an original difeafe of the liver might not have * Medical Inquiries and Obfervations, vol. iv, p. 133, THE PLAGUE. 97 have been the caufe of the intermittent. From a con- fideration of all thefe things, viz. the extreme diverfity of parts which compofe the human body, the ultimate invifibility of the ftrudure of each, the incomprehenfible manner in which they are united, the equally incompre- henfible dependence they have upon one another in fome cafes, and independence in others, the numerous laws by which they are governed, and which muft be very much unknown to us, the invifible and incomprehenfible nature of the powers which ad upon them, &c. &c. 1 fay, when we confider all thefe things, the boldeft theorist muft be humbled when he attempts to account for the phenomena of difeafe in any one inftance. The excef- five difficulty in which we are involved is beautifully defcribed by Dr. Ferriar when fpeaking of hyfterics; and obstacles equally infuperable by our theories will undoubtedly be met with in any other diftemper. " We are ignorant (fays he) by what laws the body pof- " feflcs a power of reprefenting the moft hazardous dif- " orders, without incurring danger; of counterfeiting " the greateft derangement in the circulating fyftem, " without materially altering its movements; of produ- " cing madnefs, confcious of its extravagances; and of " increasing the acutenefs of fenfation by oppreffing the " common fenforium. In hyfterical affedions all thefe " appearances are excited, which are incompatible with " the reafonings of every fyftem-maker who has yet en- " deavoured to explain the inexplicable. Nature, as if " in ridicule of the attempts to unmafk her, has, in this " clafs of difeafes, reconciled contradidions, and realized " improbabilities, with a myfterious verfatility, which " infpires the true philofopher with diffidence, and re- " duces the fyftematic to defpair." Notwithstanding all thefe difficulties, however, phy- sicians have theorifed, and that with fuch animofity, as if all the arcana of nature had been laid open to every profeflbr who thought proper to invent or new-model a fyftem; though the conftant fucceflion of theories might certainly have Shown them the vanity of fuch attempts. Some of thefe we muft now confider. O Medical 9* A TREATISE ON Medical theorifts have exerted their greateft abilities in explaining the nature of thofe general difeafes affect- ing the whole body, denominated/ww ; and which are likewife called acute difeafes, from the violence with which they fometimes attack, and the rapidity with which they run through their courfe. Dr. Fordyce fays, that fever will fometimes kill in five minutes from the firft fenfation of uneafinefs. Ancient phyficians have defcribed a number of fevers, which they fuppofed to be of different fpecies, and accordingly have distin- guished by different names. Modern fyftem-makers have added to the number; fo that a bare detail of the names which they have given to their divifions and fubdivifions, would conftitute a very formidable cata- logue ; but the lateft praditioners are decidedly of .opinion that there is but one kind of fever, varying it- felf according to circumftances. Dr. R.ufh declares himfelf of this opinion in the moft exprefs and pofitive terms. " There is (fays he) but one fever. However " different the predifpofing, remote or exciting caufes " may be, . ✓ . , ftill, I repeat,, there can be but one " fever. .... Thus fire is an unit, whether it be pro- " duced by fridionrpercuffion, eledricity, fermentation, "or by a piece of wood or coal in a State of mflam- " mation."* " I have faid that there is but one fever. Of courfe " I do not admit of its artificial divifion into genera " and fpecies; a difeafe which fo frequently changes " its form and place, Should never have been designated*' " like plants and animals, by unchangeable charaders. " . . . . Much mifchief has been done by nofological " arrangements of difeafes. They ered imaginary " boundaries between things which are of an homo- " geneous nature.....They gratify indolence in a " phyfician, by fixing his attention upon the name of a " difeafe, and thereby leading him to negled the vary- " ing ftate of the fyftem, &c."f So much then having been faid and written upon the difeafe in queftion, one might be apt to fuppofe that the nature • Vol. iv, p. 133, f Ibid. p. 149. THE PLAGUE. $9 nature of fever would have been thoroughly investigated, and its caufes explained in the moft fatisfadory manner, long before this time. Inftead of this, however, we find it ftill like a word which every body ufes, and nobody understands. Dr. Fordyce, who has lately written a treatife on the fubjed, endeavours to prove that there is not any Single fymptom from the exiftence of which we can certainly determine the prefence of this difeafe. " Fever (fays he) has obtained its name in Greek, Latin, " Arabic and Perfian, principally from the idea of heat: " pur, in Greek fire; febris in Latin, from fervere, to •■" burn," &c. This idea, he goes on to demonstrate, is erroneous; as the body of a feverifh patient frequently finks the thermometer below the natural Standard ; while the patient fometimes finds himfelf cold when the ther- mometer fhows him to be really hot, and hot while the fame inftrument fhows him to be cold. Neither is cold, followed by heat, a certain indication of the prefence of fever, as many fevers begin without any previous fenfa- tion of cold. Frequency of the pulfe alfo is no certain fign ; and having difcufTed this laft fymptom he con- cludes thus. " If we examine the reftleflhefs, anxiety, "ftate of the tongue, head-ach, or any other of the " fymptoms which often take place in fever, we fhall " find that they alfo may be prefent when there is no " fever, and abfent in a patient afflided with this difeafe; " and therefore we cannot allow that there isanypatho- " gnomic fymptom of fever."*' Dr. Rufh declines giving any definition of fever ;-f- but, with all due deference to thefe two very experienced phyficians, we muft account fuch extreme fcepticifm altogether erroneous. If fever cannot be defined, it cannot be defcribed ; for a defini- tion is no other than a fhort defcription. If again there be no fingle fymptom by which the prefence of fever can be known, it is impoflible that there can beany com- bination by which it can be known, any more than we can form an unit by any combination of cyphers. In fad Dr. Fordyce himfelf is at laft obliged to acknow- ledge • A Pathognomic fymptom is one which being prefent certainly indicates the nrefence of a difeafe, and being abfent, the contrary. t Vol. iv, p. izz. 100 A TREATISE ON Jedge thatthere is acertain fymptom with which icvcr«ene- rally begins; and, by his infiftingupon it in various parts ot the work, we muft certainly be induced to fuppofe that it was by this fign principally that he determined whether his patients had a fever or not. " The firft appear- " ance (fays he) which generally takes place is uneafinefs " and reftleflhefs; a general uneafinefs, the patient feel- " ing himfelf ill, but incapable of fixing on any particular " part of the body. This uneafinefs affeds the mind " at the fame time. Perhaps in this cafe it is the mind " that is firft affeded.....Along with this uneafinefs " there is a reftleflhefs, the patient wifhing to change " his place or pofture frequently ; the mind cannot like* " wife reft upon one objed ; it often wanders from one " to another fubjed. At the fame time there is a feel " of wearinefs which refills the difpofition in the patient " to change his place and pofture, and refills the dif- *' pofition of the mind to alter the objed of its atten- " tion, rendering the wifh for fuch changes ineffedual, " With thefe arifes an adual inability of exerting the " mufcular powers, or performing any of the fundions " of the body ; and alfo an adual inability of exercifing " the great faculties of the mind, the powers of percep- " tion, memory, arrangement of ideas, and of the judg- " ment, in the fame degree that they exifted in health, 11 The degree in which thefe take place is extremely " different in the attacks of different fevers ; but thefe " appearances are very rarely abfent, although indeed " they may alfo happen in other difeafes." Dr. Rufh accounts the laffitude with which fever begins, one of the tranfient phenomena of it; and this with other phenomena he calls fymptoms. Such as are more permanent and fixed, and which by other writers have been reckoned different fpecies, he calls fiates; and of thefe he enumerates forty. Such as have any relation to the plague are as follow. i. The malignant ftate, known by attacking fre- quently without a chilly fit, is attended with coma, a depreffed, flow or intermitting pulfe, and fometimes by a natural temperature or coldnefs of the fkin...... * This THE PLAGUE. 101 This depreflfed ftate of fever more frequently when left to itfelf terminates in petechias, buboes, carbuncles, abfceflfes and mortifications, according as the ferum, lymph, or red blood, is effufed in the vifcera or external parts of the body. 2. The synocha, or common inflammatory ftate; attacking fuddenly with chills, fucceeded by a quick, frequent and tenfe pulfe, great heat, thirft, and pains in the bones, joints, breaft or fides. 3. The bilious ftate of fever; known by a full, quick and tenfe pulfe, or by a quick, full and round pulfe without tenfion, and by a difcharge of green, dark co» loured or black bile from the ftomach and bowels. This ftate fometimes aflumes the form of an hedic; the patient feels no pain in his head, has a tolerable ap» petite, and is even able to fit up and do bufinefs. 4. The typhus ftate; known by a weak and frequent pulfe, a difpofition to fleep, a torpor of the alimentary canal, tremors of the hands, a dry tongue, and, in fome inftances, a diarrhoea. Sometimes it aflumes fymptoms of fynocha on the eleventh, fourteenth, and even twen- tieth days. The common name of this ftate is the nervous fever. 5. Intermiffions, or the intermitting and re* mitting ftates, occur moft diftindly and univerfally in thofe which partake of the bilious diathefis. 6. The sweating ftate occurs not only in the plague, but in the yellow fever, fmall pox, pleurify, rheumatifm, hedic and intermitting ftates. 7. The fainting ftate; occurring in the plague, yel- low fever, fmall pox, and fome ftates of pleurify. 8. The burning ftate. This is attended not only with an intolerable fenfation of heat in the bowels, but with a burning fenfation excited in thofe who touch the patient's fkin. It occurs moftly in the remitting fevers of Afia. 9. The chilly ftate differs from a common chilly fit by continuing four or five days, and to fuch a degree that the patient frequently cannot bear his arms out of bed. The coldnefs is moft obftinate in the hands and feet. 102 A TREATISE ON feet. A coolnefs only of the fkin attends in fome cafes, which is frequently mistaken for an abfence of fever. 10. The intestinal ftate; including the cholera morbus, diarrhoea, and cholic. n, 12, 13,14, 15. The apoplectic, phrenetic, paralytic, lethargic and vertiginous ftates. 16. The eruptive ftate; including the fmall pox, meafles, and other exanthemata of Dr. Cullen. 17. The hemorrhagic ftate; known by fluxes of blood from various parts of the body. 18. The convulsive or spasmodic ftate. Con- vulsions are frequently attendant on the malignant ftate of fever. 19. The cutaneous ftate,; attended with various eruptions on the fkin, particularly petechia. Thefe include the moft remarkable varieties defcribed by phyficians as different fpecies. From the fubfequent account of the fymptoms of the plague, it will appear that this fingle diftemper monopolifes, as it were, the fymptoms, at leaft the moft dangerous and terrible, be* longing to them all. Thofe nofologifts therefore who fuppofe the ftates of fever above defcribed to be different fpecies, inftead of faying that the plague belongs to one kind of fever, ought to fay that it is a complication of a great many different kinds. But here a queftion arifes: Do all the varieties of fever juft now defcribed, or do all the other fevers defcribed by different authors, include all the different modes by which the plague makes its attack? If fo, then we know that the plague really partakes of the nature of fever, or may be accounted the highefl degree of it. This is the opinion of Dr. Rufh; for in his 4th vol. p. 153, he confiders the different inflammatory ftates of fever, according to their ilrength, in the following order. 1. The plague. 2. The yellow fever. 3. The natural fmall pox. 4. The malignant fore throat, &c. To this I can have but one objedion, and to me it appears infuperable; viz. that the plague frequently deftroys without any fymp- tom of fever; and, if fo, we muft certainly account 1* a diftemper of another kind. To decide this matter THE PLAGUE. 103 matter, let us compare the fymptoms of the moft vio- lent fever with what happens in times of violent pefti- lence. We can fearce imagine a fever more powerful than that which deftroys in five minutes, and the follow- ing is the defcription of it from Dr. Fordyce. " When " the firft attack of fever has been fatal, it has been " claflfed among fudden deaths, and all of thefe have " been very erroneoufly called apoplexy, or fyncopy " (fainting.) .... When the attack is fatal, it fometimes " kills in five minutes, fometimes it requires half an " hour, feldom longer than that time. While the pa- " tient is yet fenfiblc, violent head-ach with great fenfe " of chillinefs takes place, the extremities become very *' cold, and perfedly infenfible ; there is great proftration " of Strength, fo that the patient is incapable of fupport- " ing himfelf in an ered pofture ; he becomes pale, his " fkin is of a dirty brown, and he is foon infenfible to " external objeds ; the eyes are half open, and the cor- " nea fomewhat contraded. If the patient goes off very " foon, the pulfe is diminifhed, and at laft loft, without " any frequency taking place ; but if it be longer before " he dies, the pulfe becomes exceflively fmall and fre- " quent; all the appearances of life gradually fubfide, " and the patient is carried off. Of this the author has " feen inftances, fometimes at the firft attack, oftener in " the returns of the difeafe, although very few." This no doubt is very terrible, and no plague what- ever can exceed it. Indeed, when death is the termina- tion, it Signifies little what the difeafe is called. But the queftion is not whether fever or plague is the moft dread- ful, but whether they are the fame. Now, from the above defcription, is is plain that fever never kills with- out fome warning. In the prefent inftance, head-ach and chillinefs give a certain, though fliort, warning of the enfuing cataftrophe ; but, in violent plagues, Dr. Sydenham informs us, that people have been fuddenly deftroyed as if by lightning. Dr. Guthrie aflures us that in the laft plague at Mofcow he has feen foldiers drop down fuddenly as if they had been ftruck by light- ning, or by a mufket ball; yet fome of thefe recovered by 104 A TREATISE ON by bleeding and proper management; but it is certainly not unreafonable to fuppofe that many, who were not thus taken care of, perifhed. Dr. Hodges fpeaks of the contagion of the plague in the moft energetic terms. He fays, " it is fo rare, fubtile, volatile and fine, that it in- " finuates into, and refides in, the very pores and inter- " ftices of the aerial particles. It is faid to be of a " poifonous nature alfo, from its fimilitude to the nature " of a poifon,'fo that they feem to differ in degree only; " for the deadly quality of a peftilence vaftly exceeds " either the arfenical minerals, the moft poifonous ani* " mals or infeds, or the killing vegetables; nay, the " peftilence feems to be a composition of all the other " poifons together, ing that he was now too old to have much enjoyment ot life,, and that, being fo far ad- vanced in a journey .\hich he mult certainly accomplifh fooner or later, he thought it better to proceed than re- turn- The Dodor informs us that he died a few days afterwards, feemingly very eafy, and carelefs about the matter. One experiment of this kind I have been witnefs to; THE PLAGUE. 121 to; not indeed on a human creature, but on a calf. This creature received into one of its jugular veins a confider- able quantity of blood from the carotid artery of another, nearly of the fame age (about a month, or little more.) It was impoffible to fay any thing about how much was transfufed ; only the bleeding was continued till the animal which loft the blood began to fhew Signs of faint- nefs. The artery was then tied up, and the orifice in the jugular vein clofed. The calf which had loft the blood appeared very languid and faint, but lived a few days in a drooping ftate; when it either died of itfelf, or was killed, as being fuppofed past recovery. The other, which had received the blood, appeared to be in every refped highly excited. It became playful, even in the room where the operation was performed, its eyes assu- med a bright and fhining appearance, and its appetite was greatly increafed. Thus it continued for about a fortnight; appearing all the time to be in high health, and eating much more than ufual; but at laft died fuddenly in the night. From thefe effeds on healthy fubjeds, how- ever, we cannot infer what would happen in fuch as are difeafed ; but it is plain that if the cure of difeafes were to depend upon mere excitation, the means are in our power, without any local irritation, which always muft take place in fome degree by the ufe of ordinary medicines. This path is not abfolutely untrodden : the pneumatic praditioners of the prefent day have tried oxygen in confumptions, and found it pernicious; and JDr. M'Kenzie informs us that the transfufion of blood was tried ineffedually in the fame. 7. As all the medicines ufually prefcribed at prefent are only to be accounted partially stimulant, orasading upon particular parts of the fyftem, we fee that fome may promote one evacuation, and fome another ; while all produce fome change in the organization, which may prove ufeful or detrimental, may increafe the difeafe or cure it, or may produce another, according to the judi- cious or injudicious application. But for a knowledge of all this we muft be indebted to experience : there is. not a theory on earth that can lead us a fingle ftep. R Before 122 A TREATISE ON Before we difmifs the confideration of medical theories, however, it will ftill be neceflary to give fome account of the new fyftem as it hath branched out in various ways: for though the fundamental principle is now received by a great number of physicians, yet the fuper- ftrudure is exceedingly different from what Dr. Brown himfelf ereded ; and, indeed, from the very fame prin- ciples we find conclusions made as diredly opposite to one another as can be exprefled in words. Drs. Yates and M'Lean, for instance, at Calcutta in the Eaft Indies, have concluded that the plague " is a difeafe of a very high degree of exhaustion;" which Dr. Brown would have called debility.- Dr. Rufh at Philadelphia, pro- ceeding alfo upon the Brunonian principles, determines it to be the moft inflammatory of all difeafes,* and which Dr. Brown would have called a difeafe of excite- ment. Thefe two dodrines are, in every fenfe of the word, as diftant from one another as eaft from weft, Let us then confider both, if any confideration can avail us on the fubjed. By the ancients it was fuppofed that difeafes wera occafioned by fomething either bred in the Body or re- ceived into it, and that the power of nature produced, during the courfe of the difeafe, a certain change in this matter, called cotlion, or concoction ; which, ifwepleafe, we may exprefs by the Englifh word cooking. The matter of the difeafe, called alfo morbific matter, thus cooked, was in a ftate proper for expulsion, and was therefore thrown out by fweat, vomit, stool, &c* or it might be expelled artificially, which could not have been attempted with fafety before. Modern fyftems deny the existence of morbific matter, and refolve all into an affedion of the nerves, according to Dr. Cullen by cer- tain fedative caufes, but according to Dr. Brown by an accumulation in fome cafes, and an exhaustion in others, of the excitability or excitement of the body. The Science of Life commences with flaring what they fuppofe to be an improvement of the Brunonian princn pies, and from which the following account of the ori- gin * See above, p. 10*. THE PLAGUE, 123 gin of difeafes is extraded. " Upon the different ftates of " excitability depend all the phenomena of health and dif- " eafe. There are three ftates of the excitability. .1. The " ftate of accumulation; when a portion of the ufual " stimuli is withheld, .... When a portion of the " ufual stimuli is withheld, the excitability accumulates, " and the body becomes fufceptible of impreflion in the " dired ratio of the fubdudion. This ftate constitutes " difeafes of accumulation, or of dired debility, 2. The " middle ftate; when the excitability is fuch that the ap- " plication of the accustomed degree of exciting powers ". produces tone or health. 3. The ftate of exhaustion. " When the application of stimuli has been greater than " that which produces healthy adion, the excitability is *' exhausted, and the body becomes lefs fufceptible of " impreflion in the dired ratio of the excefs. This ftate t? constitutes difeafes of exhaustion, or of indired debility. " The ftates of accumulation and exhaustion of the ex- " citability, in their different degrees, constitute all the *' difeafes to which living bodies are fubjed." Here the chime runs on the word excitability, which is not defined, If we call this property life, then we are only informed, that, as life is more or lefs vigorous, the body enjoys a greater or fmaller degree of health; which we know without any medical inftrudor. If, in- ftead of the accumulation and exhaustion of excitability, we take the original dodrine of excitement and debility Jaid down by Dr. Brown himfelf, we are nothing better. The whole theory is loft for want of the definition of 2 fingle word. As long as excitability remains an unknown property, we can explain nothing by it. We may in- deed vary our terms. We may call it nervous influence with Dr. Cullen, or fenforial power with Dr. Darwin; but we fhall still be as much in the dark as ever j and all that can be made out of our theories, when our lan- guage is decyphered, muft be, that fometimes people are well, and fometimes they are fick! Dr. Rufh, in his Treatife on the Proximate Caufe of Fever, adopts in part Dr. Brown's fyftem pretty nearly as the author himfelf laid it down, " Fevers of al| "- kinds A TREATISE ON " kinds (fays he) are preceded by general debility. This " debility is of two kinds, viz. dired and indired. The " former depends upon an abftradion of ufual and " natural Stimuli; the latter upon an increafe of natural, " or upon the adion of preternatural, stimuli upon the "body.....Debility is al way sfucceeded by increafed " excitability, or a greater aptitude to be aded upon by, " Stimuli.....The diminution or abftradion of one c: ftimulus is always followed by the increafed adion of " others." Here it is evident we are as much in want of definitions as ever. We know neither what excitability is, nor what debility is, and yet they are both held out as the caufes, and proximate or immediate caufes, too, of fymptoms produced by things quite obvious to our fenfes. Thus cold and heat, with which we are daily converfant, are only called the predifpoftng caufes of fever; while debility and excitement, words to which we have no meaning, are faid to be the proximate caufe. It would certainly be better to throw away fuch words al- together, and fay that cold, heat, &c. caufe fevers, with- out troubling ourfelves farther about the matter. It remains now to take into consideration the pneu- matic theories, founded upon the difcoveries made by Dr. Black, Dr. Priestley, Lavoisier, and others, concern- ing various kinds of aerial fluids, or gafes,* as they are alfo called. Some of thefe, particularly that afterwards called fixed air, were difcovered by Van Helmoqt. Confiderable advances were made by a German chemist, named Mayozv, in the laft century; but his book had fallen into fuch oblivion that his name was fearce ever- mentioned, until his difcoveries were repeated, and ftill greater advances made by others. Dr. Hales obtained air from a great many different fubftances, but was un- able to afcertain any thing concerning its nature. Dr. Black of Edinburgh laid the foundation of pneumatic chemistry, by difcovering that a certain fpecies of air is capable of being ablbrbed by earths of different kinds, and that many very heavy fubftances owe at leaft one half •G** is a German word, or derived from one, fignifying fpirit. Th< word gbofi comes from the fame original. THE PLAGUE 125 half of their weight to this condenfed air. The difco- very was accidental. Wifhing to obtain a very pure and white lime, he had recourfe to the fine white earth * called magnefia alba. Some of this he diftilled with a heat fufficient to make the veffel red hot. Only a very fmall quantity of water came over, but the magnefia had loft almoft two thirds of its weight. This immenfe lofs was found to arife from an emiffion of air during the operation; and by other experiments it was likewife found that the air might be transferred from one portion of magnefia to another from which it had been previ- ously expelled ; that the existence of this fpecies of air in certain bodies was the caufe of that fermentation which takes place when any acid is poured upon them, as vinegar upon chalk or potaSh. Hence if any of thefe fubftances be deprived of its air, it will not any longer * ferment in this manner. It muft not be forgot, how- ever, that when air thus unites itfelf with any terrestrial fubftance it no longer has its former properties. It is reduced exceedingly in bulk, and in proportion to this re- dudion only the body is increafed in weight; and therefore though we fay that the air is abforbed, we muft ftill re- member that only one part of it is fo, and that by far the leaft confiderable in bulk. A violent fire will always expel the air again, and restore it to its former bulk; and again the condenfation or abforption of the air is always attended with the produdion of heat. This laft property was not much attended to by Dr. Black, but others have obferved it; and the late Dr. Charles Web- ster of Edinburgh publifhed a theory in which he main- tained that condenfation was in all cafes the caufe of of heat. But, however true it may be that condenfation of any kind is followed or accompanied by heat, it is evidently neceflary to know the caufe of the condenfation alfo, otherwife we make no advance in folid theory. The aerial fluid, difcovered by Dr. Black, was one of thofe moft commonly met with. He called it fixed air, from its property of adhering or fixing itfelf to dif- ferent bodies. It was found to be the fame with that which had been difcovered by Van Helmont, and by *i$ A TREATISE ON him named gas fylveftre (fpirit of wood)* or the fuma of charcoal; it was found to he the fame with the fleam of fermenting liquor, and with that very frequent and dangerous vapour, met with in coal mines, called in Scotland the choke-damp. Like other difcoveries, this was quickly pufhed beyond its proper bounds, and ap. plied to the folution of phenomena which it could not folve. Dr. M'Bride, particularly, fuppofed it to be the bond of union between the particles of matter, or in other words the principle of cohesion itfelf. It was alfo fuppofed to be the fubftance of thofe fcorching winds, called famiel, met with in Afia and Africa, and which fometimes prove fatal to travellers. The pernicious va- pours called mofetes, which fometimes iflue from the old lavas of Vefuvius in Italy, were likewife fuppofed to be the fame ;-\ but of this, particularly with regard to the famiel, there feems to be no fufficient evidence. ,-, * This muft be underftood only of its general properties and effefls; for, though the fume of charcoal poffeffes many of the apparent properties of Jure fixed air, it contains alfo a very confiderable quantity of another kinoi + Many fabulous ftortes have been related concerning the famiel. EveW fo late a traveller as Mr. Ives has adopted fome of thofe exaggerated accounts which have been difcredited by thofe who have long refided in the coun- tries where this wind is commonly met with. It is not peculiar to the de- ferts of Arabia, but is met with in all hot countries which are deftitute of water. In the African deferts therefore it is common ; and Mr. Bruce de- scribes it by the name of fimaom. It was preceded by whirlwinds of a v ?y extraordinary kind. "In that vaft expanfe of defert (fays he) from W. ** and to N. W. of us, we faw a number of prodigious pillars of fand at dif- •1 fesent diftances, at times moving with great celerity, at ethers walking on " with a majeftic flownefs. At intervals we thought they were coming in 4 V very few minutes to overwhelm us ; and fmall quantities of fand did adu- •* ally more than once reach us. Again they would retreat fo as to be almoft out «« ot light; their tops reaching to the very clouds.* There the tops often fe- V pirated from the bodies; and thefe, once disjoined, difperfed in the air, ** and did not appear more. Sometimes they were broken near the middle, •* as if ftrucfc with a large cannon ihot. About no4n they began to advance V with confiderable iwiftnefs upon us, the wind being very ftrong at north. »• Eleven of, them ranged along fide of us at about the diftance of three «•• miles. The largeft of them appeared to me at that diftance to be about «' ten feet diameter.....It was in vain to think of flying; the fwifteft « horfe or the fafted failing (hip could be of no ufe to carry us cut of this »* danger; and the full perluafion of this rivetted me as if to the fpot where, " * "ood- At another time he faw them in much greater number, but of fmaller fi»e. They began immediately after funrife, like a thick wood, and almoft darkened the fun. His rays darting through them gave them the appearance of pillars ot fire. They now approached to the diftance of two miles from our travellers. At another time they appeared beautifully. fpangled, N. B. In thefe fandy deferts, where it never rains, there arc no clouds* THE 1PLAGUE. 1*7 The induftry of other experimenters did not long leave theonfts without abundance of materials upon which they might exercife their talents. It is impoffi- ble in this place to aflign to each his proper rank in the way of difcovery, or indeed to mention their names. Dr. Priestley has diftinguifhed himfelf far above the reft. He not only repeated and improved Dr. Black's experi- ments on fixed air, but likewife found out a number of other kind?; particularly that from animal fubftances in a ftate of putrefaction, which is fo pernicious to living creatures* infects excepted; for thefe laft will thrive amazingly in air that would prove certain death to a man. He alfo difcovered that this kind of air, and fome others, were abforbed by vegetables, and thence inferred the ufe of vegetables in purifying the atmofphere. He even analyfed the atmofphere itfelf, and found that it fpangled with ftars. in Darwin's Botanic Garden we find a reafon affignedl for the appearance of thefe whirlwinds; viz. the impulfe of the wind on a long ledge of broken rocks which bound the defert. By thefe the currents of air which (truck their fides were bent, and were thus like eddies in a ftream of water which falls againft obliqie obftacles. In the fame work we have the following poetical defcription or them : «* Now o'er their heads the whizzing whirlwinds breathe, And the live defert pants and heaves beneath j Ting'd by the crimfon fun, vaft columns rife Of eddying fands, and war amid the (kief, tn red arcades the billowy plains furrourid. And whirling turrets ftalk along the ground." Whether the fimoom is always preceded by thefe whirlwinds we know not; but Mr. Bruce mentions an extreme rednefs of the air, pointed out by his atten- dant Idris, as the fure prefage. His advice was, that all of them, upon the approach of the pernicious blaft, fhould fall upon their faces, with their mouths on the earth, and hold their breath as long as poflible, fo that they might not inhale the deadly vapour. They foon had occafion to follow this advice; for next day Idris calle.l out to them to fall upon their faces, for the limoom was coming. " I faw (fays Mr. Bruce) trom the S. E. a haze com- •« ing, in colour like the purple part of the rainbow, but not f» compreUed or «« thick. It did not occupy twenty yards in breadth, and was about twelve " feet tfgh from the ground. It was a kind of blufti upon the air, and it •• moved very rapidly ; for 1 could fearce turn to fall upon the ground, with •« my face to the northward, when I felt the heat of its current plainly upon •« my face. We all lay flat on the ground, as if dead, till Idris told us it " was blown over. The meteor, or purple haze, which I faw, was indeed " patted ; but the light air that ftill blew was of heat fufficient to threaten •• futtbeation. For my part, I felt diftindlly in my breaft that I had imbibed •« a part of it; nor was 1 free of an althmatic fenfation till I had been fome «« months in Italy, at the baths of Poretta, near two years afterwards." It continued to blow for fome time, and in fuch a manner as entirely to ex- hauft them, though fcarcely fufficient to raife a leaf from the ground. The account given by Mr. Ives is, that it blows over the defert (of Syria) in the months of July and Auguft, from the nerthweft quarter, and fometimes continues 128 A TREATISE ON it consisted of two different kinds of fluids, one of which he called dephlogiflicated, the other phlogifticated air. The former was found to fupport animal life for a time, the latter to deftroy it instantly. Their effects upon fire were the fame; the former exciting the moft vehement heat and bright flame, the latter extinguifh- ing a fire at once. The fame of Dr. Priestley's difcoveries quickly reached the continent of Europe ; the French chemists repeated his experiments with improvements, as they thought; and indeed certainly made many curious difcoveries. Lavoifier was particularly remarkable for his numerous and accurate experiments ; but, by his changing entirely the language of former chemists, and substituting a fet of new terms of his own invention, he certainly entailed the greateft curfe upon the fcience it ever met with. It belongs not to this treatife to give an account of his fyftem farther than to fay, that, from the immenfe proportion continues with all its violence to the very gates of Bagdad, but never aflefts any body within its walls. Some years it does not blow at all, and in others it comes fix, eight, or ten times, but feldom continues more than a few mi- nutes at a time. It often pafles with the apparent quicknefs of lightning. The fign of its approach is a thick haze, which appears like a cloud of duft rifing out of the horizon, on which they throw themfelves with their faces on the ground, as already mentioned. Camels are faid, inftinctively, to bury their nofes in the fand. As for the ftories of its diflblving the cohefion of the body in fuch a manner that a leg or an arm may be pulled away from thofe who are killed by it, or that their bodies are reduced to a gelatinous fubftance, we cannot by any means give credit to them. From its extreme quicknefs, and luminous appearance, it would feem to be an electrical phenomenon im- mediately preceding thofe vehement hot winds which all travellers agree in likening to the vapour ifluing from a large oven when the bread is newly ta- ken out. its electrical nature will be more probable from the account given by Mr. Ives, that the Arabians fay it always leaves behind it a very fulphu- reous fmell. Thefe particulars do not at all accord with the fuppofuion of its confiding of fixed air. I have indeed been allured by a gentleman lonj in the fervicoof the Englilh Eaft India Company, that the famiel cannot pals over a river. Hence probably it has been fuppofed to be a blaft of fixed air, becaufe this fpecies of gas is readily abforbed by water ; but we know that the fame thing would alfo take place with any quantity of eleclric matter; for water takes up this alfo much more completely than it does fixed air. The mofetes are invisible, and kill in an inftant. They rife from old volca- nic lavas, and, as it were, creep on the ground, and enter into houfes, fo that they are very dangerous ; but, though they may probably confift of fixed air, we have not as yet any direct proof of it. It is not indeed eafy to imagine why any lava mould fuddenly emit a great quantity of fixed air, and then as fuddenly ceafe; nor in what manner the aii thus emitted (hould continue unmixed with the atmofphere; for fixed air will very readily mix in this manner, infomuch that a large quantity of it being let loole in a room ha:. been found to vanilh entirely in lef» than half an hour. Sir William Harr.il- ton mentions a mofete having got into the palace of the king ot Naples. THE PLAGUE. 129 proportion of condenfed aerial matter found in moft terreftrial fubftances, he and his followers were led to conclude, that different fpecies of air conftitute almoft the whole of the terraqueous globe. Water particularly they have abfolutely and moft positively determined to be a composition of two airs condenfed, viz. the dephlo- gifticated and inflammable, which they call oxygen and hydrogen. However, this doctrine is ftill oppofed by Dr. Priestley and fome others. In the midft of fo much theory, and fo many new and furprifing difcoveries, it would have been wonder- ful indeed if the.fcience of medicine had kept free from innovation. It did not: the new chemistry, with all its formidable apparatus of hard words, was introduced, and thus the study of the fcience, already very difficult, was rendered ftill more fo. In paffing this cenfure upon the modern nomenclature, as it is called, I am fenfible that I muft rank with the minority ; neverthelefs, I have the fatisfaction of finding that I am not altogether lin- gular. Dr. Ferriar, in the preface to his fecond volume, complains, " that, with every attempt towards the for- " mation of a fyfiem, new applications of words are in- " troduced, which, though desirable in the art of po- *' etry, are very inconvenient in pathological books, efpe- " cially when this is done to give an air of novelty to " old theories and obfervations. For, between the an- " cient language, which practitioners cannot entirely " reject, and the new dialed, which they cannot wholly " adopt, the style of medical books is reduced to a kind " of jargon, that the author himfelf may poflibly under- " Stand, but which his readers find it very difficult to " unriddle. Hence refults a neglect of medical litera- " ture, and hence the pernicious habit of regarding as " new whatever has not appeared in the publications of " the laft half century." To the fame or a Similar pur- pofe, in the prelace to his first volume, he cites Qnin- tilian. *" Some have fuch a multitude of vain words, that, while they are afraid of fpeaking like other people, by * Eft etiam in quibufdam tutba inanium verborum, qui dum communem ioquendi morem reformidant, du&i fpecie nitoris, circumeum omnia, copiofa toquacitate, quae dicere volunt. s i3o A TREATISE ON by a kind of affected elegance, they confound every thing they have to fay with their immenfe loquacity. The pneumatic fyftem naturally arofe from a confi- deration of 'the composition of the atmofphere we breathe. Finding this fluid to be compofed of two others, the one of which would preferve life for fome time at leaft, and the other inftantly deftroy it, it be- came natural to think that difeafes might be produced by any confiderable variation in the proportion of thefe ingredients. An instrument was foon invented by which any confiderable variation in this refpect might be difcovered ; but upon trial this was found to be of very little ufe. Dr. Priestley himfelf tried, by means of this instrument, fome very offensive air which had been brought from a manufactory, and could find no remark- able difference between it and that which was ac- counted pure. Still, however, it was evident that by in- creasing very much the proportion of one of the ingre- dients, fome confiderable alteration might be produced, which could not but be perceptible in the human body; and this led to the application of aerial chemistry to dif- orders of the lungs. The mixture chofen for this pur- pofe was pure dephlogifticated (oxygen) with inflam- mable air (hydrogen;) and, though this has not been known to effect a radical cure, it certainly has given relief in many cafes. In fevers alfo the application of fixed air (carbonic acid) hath been found advantageous; but with regard to oxygen and fome others we have not yet a decided inftance of their good effects in any cafe. Dr. Beddoes indeed is of opinion that it would be of fervice in the fea-fcurvy; but in this (whether his con- jecture be right or wrong) the theory is certainly erro- neous,, as (hall prefently be evinced. In considering the pneumatic fyftem it is evident that modern chemists have fallen into the fame error with their predeceflbrs, viz. of fuppofing that every thing which by the force of fire or otherwife they could produce, from any fubftance, previoufly existed in it. Hence, as from a piece of bone for inftance, a chemift can produce water, fait, oil and earth, it was fuppofed that THE PLAGUE. *3i that thefe four were the principles or elements of the bone. But this was falfe reafoning; for if thefe were really the chemical principles, they ought to have been able to produce fome kind of bony fubftance by mixing them together after they had been distilled. But no fuch thing could be done ; and though we fhould add to the mixture the whole quantity of air emitted during the diftillation, and which efcaped the notice of ancient chemists, our fuccefs would be no better. In like manner, becaufe in certain circumstances oxygen is obtained from the flefh of animals, it has been con- cluded that it neceflarily exists as an ingredient in then- bodies while living; and that, if this kind of air happens to predominate, the animal will be affeded in one way, or if hydrogen prevail, in another. But though we have already quoted Dr. Girtanner with approbation as having obtained oxygen gas from frefh meat, yet this does not by any means prove to us that it exists in flefh as one of its component parts. Even in the Dodor's experiment it was neceflary to expofe the flefh to the atmofphere in order to procure the gas by diftillation; which undoubtedly muft excite a ftrong fufpicion that the air in queftion comes from the atmofphere itfelf; and, if this is the cafe, it is not reafonable to fuppofe that a difeafe could be cured by any addition of oxygen to the folid parts; becaufe, though found flefh may have an inclination to abforb this kind of air, we do not know whether it would have fuch a property of abforption in a difeafed ftate. Indeed in the fcurvy, which Dr. Beddoes choofes as an example, experiment feems to determine in favour ot fixed air rather than any other. But let us hear Dr. Girtanner himfelf, who has at large difcuffed this fubjed in two memoirs; one upon the laws of irritability, and another on the principle of irritatibility. In thefe memoirs we find the Brunonian doctrine fet forth with fuch filence in regard to Dr. Brown himfelf, that fome have not fcrupled to charge Dr. Girtanner with literary theft; but this is a matter which belongs not to us to confider: the theory may be verv good, whether stolen or not. He changes the word excitabi- A TREATISE ON lily, ufed by Dr. Brown, for irritability; but hath the misfortune of not being able to tell us what he means by it. He goes on, however, to diftinguifh the three ftates ot tone or health, accumulation, and exhaufiion, as other Brunonians do. Health, he fays, in a fibre <' con- " fifts in a certain quantity of the irritable principle " neceflary for its preservation. To maintain this ftate, " the adion of the ftimulus muft be ftrong enough to " carry off from the fibre the furplus of this irritable prin* " ciple, which the lungs and the circulation of the " fluids are continually Supplying. For this a certain " equilibrium is neceSTary between the stimuli applied " and the irritability of the fibre, in fine that the fum of " all the Stimuli acting upon it may be always nearly " equal; powerful enough to carry off from the fibre " the excefs of its irritability, and not fo ftrong as to " carry off more than this excefs.....When the " fum of the stimuli ading upon the fibre is not great " enough to carry off all its excefs of irritability, the " irritable principle accumulates in the fibre, and then " it is found in that ftate which I call the flate of accu- " mutation; the irritable principle accumulates in the " fibre, its irritability is augmented, and the stimuli pro? " duce much stronger contradions than when the fibre " only retains its tone. .... When the fum of the " stimuli ading upon the fibre is too great, the fibre " is deprived not only of the excefs of its irritability, but " alfo of fome portion of the irritable principle neceflary' " for the tone of the fibre; or, more properly fpeaking, " the fibre lofes more irritability than it receives, and, ft of courfe, in a fhort time finds itfelf in a ftate of ex* " haufiion ; and this exhaustion will be either temporary, " or irreparable." Here it is evident that we have nothing but Dr. Brown's fyftem, without the leaft explanation to render it more intelligible. A definition is still wanting. This invisible and incomprehenfible property of irritability ruins our whole fabric ; nor can the deficiency be fup- plied by human art or fkill: of confequence we muft abandon this part of the fyftem entirely, and come to fomething THE PLAGUE. *33 fomething more cognizable by our fenfes. It is impof- fible, however, to pafs over in silence the amazing inat- tention of the author, in imagining that on fuch unin- telligible principles he could explain other phenomena. *' In the state of temporary exhaufiion (fays he) the fibre " lofes its tone, and fails for want of irritability. The " application of a ftimulus while it is in this state will " not make it contrad. Provided the ftimulus be not " very strong, it will produce no effed at all, but in a " fhort time the irritable principle will accumulate afrefh " in the fibre, and then it will again contrad. It is " only by little and little that the fibre recovers its irri- " tability. This truth, I dare venture to fay, is as new' " as it is striking.. It unfolds a vaft number of phe- " nomena hitherto inexplicable." Here we have no- thing but the pompous declaration of a fad already well known; viz. that not only a fibre, but the whole body, may be in a ftate of temporary infenfibility, and yet recover either of itfelf or by the ufe of external means. How many people have fallen into zfyncope, and yet re- covered ! How many limbs have become paralytic, and in time recovered their fenfe and motion ! Yet this is all that we are informed of with fo much parade and atTumption of novelty. We know that when a perfon is in a faint he is infenfible to ordinary stimuli, though yery ftrong ones will roufe him ; but what can we infer from this ? Nothing ; only we fee it is (o. Does it avail us any thing to be told that during the time of fainting the irritability is exhausted, and " in a fliort time the irritable principle will accumulate afrefh;" in which cafe the patient will no doubt recover, unlefs he happens to be dead, which is the true meaning of an irreparable exhaufiion of the irritability. In fpeaking of the principle of irritability he exprefTes himfelf in the following manner. " I think that the " oxygen is abforbed by the blood, and that the venous " blood is oxygenated in the lungs during refpiration. *' The moft celebrated naturalists and chemists are of a " different opinion : they think that the oxygen does ft not combine with the venous blood. According to " them, ^34 A TREATISE ON " them, this laft lofes carbon and hydrogen, and re- " covers the bright colour natural to it, without abforb- " ing any thing from the atmofphere.....After hav- " ing a long time attended the phenomena of refpira- " tion, and made many experiments upon this fubjed, " I think it may be concluded that one part of the " oxygen of the vital air combines with the venous " blood, of which it changes the black colour, and " makes it vermilion;* the fecond part of the oxygen " unites with the carbon contained in the carbonic-hy- "■ drogen gas, which exhales from the venous blood, and " forms carbonic acid air; a third part unites with the " carbon of the mucus, contained in great quantities in " the lungs, and which is continually decomposing; this "■ part alfo forms carbonic acid air; a fourth part of the " oxygen combines with the hydrogen of the blood to 44 form water." On this theory I fhall only obferve, that though I lay claim to the former part, I allow the Dodor all the latter part to himfelf; particularly where he fpeaks of the formation of water to be exhaled during refpiration. The air in queftion confifts of two parts, like fixed air already mentioned. One of thefe is capable of being attraded, condenfed, or united with certain fubftances; the other vanifhes, leaving no other traces of its having ever ex- isted, but heat, greater or lefs according to circumstan- ces. When the air is taken into the blood, one part of it undoubtedly combines with fomething thrown out by the lungs, and forms fixed air, of which our breath con- tains a confiderable quantity. We know, certainly that the condenfable part of fixed air is formed out of the condenfable part of the oxygen, with certain additions. As therefore great part of this condenfable oxygen is thrown out in fixed air at every expiration, it is natural to fuppofe that all of it is fo : at leaft we cannot know the * Here Dr. Reddoes, from whofe publication this account of Girtanner's memoir is taken, has the following note : " Dr. Goodwyn had ; ;ov< u this before. Could Dr. Girtanner be ignorant of his expeiiments ?" In /Litice to myfelf, however, I muft obferve that this very doctrine had been putlifh- ed in the Encyclopedia Britannica. long before either Dr. Guodv.ya or Dr. Girtanner had made any experiments on the fubjec"t. It may ftj'.l be J'een under the article Blood, and realons are there given for fuppofing that •nly one pari of the oxygen, viz, the elaftic part, can be abforbed. THE PLAGUE. x35 the contrary without a feries of very difficult and tedious experiments, which have never been made by Dr. Gir- tanner or any body elfe. But if the whole of this con- denfable part be thrown out, none can enter the blood by the breath ; and confequently whatever true oxygen may afterwards be expelled from that fluid, muft be a faditious fubftance, formed either during the artificial procefs, ufed for distilling it, or by a natural procefs in the body itfelf. It is not therefore at all probable that the oxygen which flefh emits in distillation can be de- rived from the air by refpiration. N Another and more probable fource is the food and drink we take ; all of which are more or lefs impregna- ted with air of different kinds, particularly fixed air. This, we know, very readily condenfes, and certainly will do fo when taken into the body. In this ftate it not oniy m.iy, but certainly will, pafs into the blood, and through all the different parts of the body, until, having accomplifhed its purpofe, whatever that may be, it is thrown out by infenfible perfpiration, as has been already explained. The conclusions drawn by Dr. Girtanner from his experiments are, i. That the change of colour which the blood undergoes during the circulation is not owing to its combination with hydrogen air.* 2. The deep colour * Here it is neceffary to obferve, for the fake of accuracy and perfpicuity, that, in the new chemiftry, the terms of which are now very generally adopted* the words oxygen and hydrogen when mentioned by themfelves are not under- ftood to fignify any kind ot air, bur what I have called the condenfable part of the air. If the word air is added, then the whole fubftance of the fluid is underftood. But though this is the ftricl orthodox language of the new chemiftry, it is impoflible to fay whether every one who adopts the terms be fufttcieatly careful in this refped Indeed this is one out of many inconve- niences that might be pointed out which have arifcn from this nomencla- ture ; for thus the mere omilfion of a monofyllable, which may happen in numberlefs inftances, totally perverts the meaning of the author, and may of courfe fubjed him to unmerited cenlure. Befides, it is not to be known* unlefs the author tells us fo, that he defigns to obferve this ftridnefs, and ot confequence we muft in multitudes of cafes be uncertain of the meaning of what we read. Thus, in the prefent inftance, when Dr. Girtanner fpeaks of oxy- gen, we know not certainly whether he means the air in fubftance, or only one of its component parts. Probably he means the condenfable or folid part. If he does fo, there muft be a very material difference between his theory and that laid down in the Encyclopaedia, and which is fupported throughout this treatife. In the latter it is maintained that the condenfable part is thrown out by the breath, being previoufly converted into fixed air, while the elaftic part enters the vital fluid, communicating to it not only the red colour, but heat, and the principles of life and fenfation, as will be more fully explained in the fequel. i36 A TREATISE ON colour of the blood in the veins is owing to the carbon it contains. 3. That the vermilion colour of the arterial blood proceeds from the oxygen with which the blood is conjoined during its paflage through the lungs. 4. That refpiration is a procefs exadly analogous to the combustion and oxydation of metals ; that thefe pheno- mena are the fame, and to be explained in the fame manner. 5. That, during circulation, the blood lofes its oxygen, and charges itfelf with carbonic hydrogen air, by means of a double affinity. 6. That, during the distribution of the oxygen through the fyftem, the heat which was united with this oxygen efcapes; hence the animal heat. 7. That the great capacity of arterial bfood for heat is owing to the oxygen with which it is united in the lungs. On thefe propositions, which conftitute in a great meafure the fundamental principles of the dodrine of oxygenation of the human body, we may remark, 1. Nobody can reafonably fuppofe that hydrogen air is the caufe of the dark colour of the blood in the veins, becaufe there is no fource from which it can be derived ; and, befides, it is certain that no kind of air can exist in its elaftic ftate in the blood, without deftroying the life of the animal. Some experiments proving this are given by Dr. Girtanner himfelf. It is true that an ae- rial vapour, of the nature of fixed air, exhales from the body by infenfible perfpiration; but there can be no doubt that this receives its elasticity only at the furface of the body, and is expelled the moment it is formed. It has indeed been proved, by undeniable experiment,. that no air of any kind exists in the larger veins; be- caufe a portion of a vein, included between two liga- tures, being cut out, and put under the receiver of an air- pump, does not fwell in the leaft when the air is ex- haufted, which yet muft be the cafe, did the fmalleft quantity of elaftic air exist in it.* 2. When * Hydrogen air is the fame with that by Dr. Prieftley called inflammable air. He alio difcovered the true compofition of it. Having included a few grains of charcoal in the receiver of an air-pump, and exhaufted the air, h& heated it in vacuo by means of a large burning glafs. The charcoal was entirely volatilized and converted into this kind of air. He found, however, that without fome fmall portion of moifture this volatilisation did not take' place. THE PLAGUE. J37 2. When the Dodor aflferts that the dark colour of the venous blood is owing to the carbon it contains, he is in the firft place chargeable with the error of former chemists, who fuppofed that everything which could be extraded from any fubftance by fire, existed previoufly in it, in thatvery form in which it is extraded by the fire; and in the fecond place he fpeaks entirely, at random, without even a ftfadow of proof. Nay, he himfelf tells us, that he has repeated two of Dr. Priestley's experi- ments, which in the clearest manner demonstrate, that neither the addition nor the abftradion of carbon, or any thing elfe, give this dark colour to the venous blood. " A fmall glafs tube (fays he) filled with arte- " rial blood, of a bright vermilion, was fealed hermeti- " cally,* and expofed to the light. The blood chan- " ged its colour by degrees, and in fix days became " black as venous blood. The fame experiment was " repeated, with this difference only, that the tube was " expofed to heat, and not to the light. The blood " became black in a fhorter time." In thefe experi- ments it is plain, that if the blood contained oxygen at first, it did fo at the laft ; the fame with regard to car- bon. How came it then to pafs, that without either evaporation of the former, or addition of the latter, the change fhould be produced ? If the oxygen imbibed by the blood in the lungs was fufficient to produce the red colour, why did it not preferve it ? The cafe here is pre- cifely similar to what happens with the calx of filver. When that metal is difTolved in aqua fortis, and again reduced to a folid form, it appears as a white powder, and will preferve its colour if carefully kept from the light ; but if a vial be filled with it, and expofed to the fun, that fide on which the light falls will in a fhort time become black, and this though the vial has been ever fo carefully fealed.-j- Formerly, chemists had a me- thod * A glafs tube is fealed hermetically, by heating the open end or ends, till they become foft, and then doling them with a pair of pincers. t Thus letters, or other characters, may be curioufly marked upon the calx within the vial, by cutting them out in paper, and then palling them on the fide to be expofed to the light. We may have them in this manner either dark upon a white ground, or white upon a dark ground. T 138 A TREATISE ON thod of accounting for this appearance, as well as that of .the venous blood, by what they called the evolution ofphlogifton: but now that the very existence of phlo- giston is denied, we are deprived of this refource. But, whatever words we may ufe, it is plain that in neither cafe have we any ideas affixed to them which can make the matter at all more intelligible than it was before. But with regard to the blood, we are at a confiderable lofs to understand what the natural colour of it is ; and indeed the queftion can only be determined by exa- mining the blood of a foetus which has never breathed, If the arterial blood of fuch a foetus be of a dark colour/ refembling that in the veins of a grown perfon, we muft look upon this to be natural to it, and we may as well inquire why a rofe is red, or an iris blue, as why the blood is of a dark, and not of a bright red. But, if we find this dark red change to a bright fcarlet in the arte- ries, as foon as the child has breathed, we have as much reafon to conclude that the air occasions this fuperior rednefs, as that an acid is the caufe of a red colour in the fyrup of violets, or an alkali of a green colour in the fame. Experiments are yet wanting to determine this matter. Mr. Hunter has obferved that " in fuch fce- " tufes as convert animal matter into nourifhment, they " most probably have it (the colour of the blood) influ- " enced by the air, fuch as the chick in the egg, al- " though not by means of the lungs of the chick, we " find the blood, in the veins of their temporary lungs, *' of a florid colour, while it is dark in the arteries."— 'The probability therefore is, that the blood is naturally dark ; by the elaftic principle of the oxygen that it is rendered brighter; and that, this elaftic principle being expended in the courfe of circulation, the fluid reaf- fumes its original colour. 3. Though enough has already been faid to evince that the fuperior rednefs of the arterial blood is derived from oxygen gas, we fhall ftill quote two inftances from Mr. Hunter's Treatife on the Blood, which fet this forth in the clearest manner; and thefe inftances are the more remarkable, becaufe they demonstrate the pheno- mena THE PLAGUE. . *39 mena not of the dead, but of the living body, i. A gen* tieman in an apoplexy, who feemed to breathe with great difficulty, was bled in the temporal artery. The blood flowed very flowly, and for a long time. It was as dark as venous blood. He was relieved by the opera- tion ; but, on opening the fame orifice in two hours, the blood flowed of the ufual florid colour. 2. A lady in an apoplexy was treated in the fame manner, and Mr. Hunter obferved, that when fhe breathed freely, the blood from the temporal artery aflumed a bright red colour; but when her breathing was become difficult, or when fhe feemed fearce to breathe at all, it refumed its dark colour, and this feveral times during the ope- ration. 4. Refpiration is not, as Dr. Girtanner fays, a pro- cefs similar to the combustion and oxydation (the calci- nation) of metals. Some of thefe by calcination, and all of them in the opinion of Dr. Girtanner, unite with the condenfable part of the oxygen contained in the air, while the elaftic part is diflipated in flame or heat. The reverie of this takes place in breathing ; for here the elaftic part of the oxygen unites with the blood, and makes it warm, while the condenfable part, uniting with certain particles to be thrown off from the body, pafles away in fixed air. Thus the procefs of refpiration does not refemble the calcination of a metal (at leaft acccording to our author's opinion of that operation) but rather the inflammation of fome combustible fubftance; for in both cafes a certain quantity of carbon is found to be united with the basis of oxygen in the atmofphere, and thrown off from the place of combustion; and thus a quantity of fixed air is produced from every burning fubftance. Juft fo is it with refpiration. If the con- denfable part of the oxygen combined with the blood, then no fixed air could be produced ; or if any part of the oxygenous bafe was abforbed, it muft certainly be known by a proportional deficiency in the quantity of fixed air produced. But there are no experiments made with accuracy fufficient to determine this point. It is true that many very able phyfiologifts, as Borelli, Ju/in, 140 A TREATISE ON &c. have been of opinion, that part of the air is abfor- bed in refpiration ; but when we come to particulars no- thing can be determined. Dr. Hales by experiment found the quantity abforbed to be a fixty-eighth part of the whole quantity infpired ; but, on account of fuppofed errors, he ftates it only at an hundred and thirty-fixth part. Between thefe two the difference is fo enormous, that we know not how to draw any conclusion from them. The French chemists are more decisive, and agree pretty well with one another. Chaptal calculates it at three- hundred and fifty-three, and La Metherie at three hundred and fixty, cubic inches in an hour. Allowing thefe ex- periments to be juft, the next queftion is, what part of the air is abforbed. Lavoisier fays, that it is the oxy- genous bafe, or the fame with that which is abforbed in the calcination of mercury. But how comes he to know this ? Surely not in the fame way that he determines the abforption of it by mercury. In the latter cafe he takes. a certain quantity of mercury, includes it in another known quantity of oxygen air, and heats the metal by means of a burning-glafs or otherwife : the confequence is, that the air is abforbed, the mercury lofes its fluidity, and is increafed in weight. The metal gains the whole. weight of the air abforbed ; and, by another procefs, all the air and all the metal, or very nearly fo, may be ob- tained in their original form. This experiment is fo decisive, that nothing can be faid againft it with any flia- dow of reafon ; but who hath made, or who can make, fimilar experiments with the blood of a living man ? Such experiments indeed might be made, if infenfible perfpira~ tion did not stand in our way. Common atmofpherical air is about eight hundred times lighter than water. A cubic inch of distilled water, according to Dr. Kirwan, weighs two hundred and fifty-three grains and a quarter. Oxygen air is fomewhat lighter than common air: we fliall therefore fuppofe that fix hundred inches of it are equal to an inch of water. If then the blood abforb three hundred and fixty inches of air in one hour, it will in twenty-four hours have abforbed eight thoufand fix hundred and forty inches, equal in weight to fourteen inches THE PLAGUE. 141 inches of water and two fifths, which according to Dr. Kirwan's estimate is between feven and eight ounces. But the quantity of matter infenfibly perfpired in that time is fo much greater, that no calculation can be made. Here is one mode of determining the quan- tity of oxygen infpired totally impradicable in the hu- man body, though quite eafy and pradicable in the cafe of mercury. The other mode of determining it by the expulsion of oxygen from the blood is equally impradicable. Dr. Girtanner indeed has expelled ox- ygen from flefh; but we know not in what proportion, nor can we determine whence it came. With regard to this laft, indeed, there are two fources allowed by Drs. Beddoes and Girtanner themfelves; viz. the abforption of oxygen by the lungs, and the quantity taken in with the aliment. A third fource was alfo manifeft from Dr. Girtanner's experiments; viz. abforption from the at- mofphere ; for, by expofure to the atmofphere, flefh, which had once parted with its oxygen, became again impregnated with it. In this cafe therefore we muft acknowledge that the uncertainty of the abforption by the lungs muft be extremely great. A certain quantity of oxygen is undoubtedly thrown out in fixed air. How are we to determine this quantity ? Certainly not by the firft reverie that happens to occupy our imagination. It is a problem, the fclution of which mast be attended with the utmoft difficulty. We muft know, in the firft place, how much oxygen was contained in the air infpi- red. In the fecond place we muft know the quantity of fixed air expired. In the third place we muft exadly know the proportion of oxygen contained in the fixed air thrown out by the breath. In the fourth place we muft determine whether, by the conversion of oxygen into fixed air, any change is made in its bulk. For, if this fliall be found to be the cafe, we fhould be led to fuppofe an abforption or augmentation of air when no fuch thing took place. This point therefore ought to be determined with the utmoft accuracy. In the fifth place we-muft exactly know how much azote, Jepton, phlogifiicated air is contained in the atmofphere infpired, and A TREATISE ON and likewife in that expired. In the Sixth place, we muft be aflured that there are no other fluids in the at- mofphere capable of being abforbed by the lungs, ex- cepting oxygen and azote. Whether there are any others or not, hath not been determined. From an expreffion of Dr. Fordyce, he would feem to be fkeptical on the fubjed. " The atmofphere (fays he) is found " to consist of various vapours, of which air, or, as it " has been called, pure air, or refpirable air, (oxygen air) " forms at prefent about a fourth. Gas (probably fixed " air) forms fome part ;-f* but the greateft part confifts '* of one or more vapours, which, without any pofitive " quality, but from that indolence which makes mankind " in their refearches attempt to find a refiing place, have *c been confidered by many chemifis as one individual fpecies; " under the names of phlogifiicated air," &c. In the fe- venth place we ought to know what quantity of pure oxy- gen, unconverted into fixed air, or whether any fuch, is thrown out by the breath. That a quantity of this kind of air is really thrown out, is probable, becaufe we can blow up a fire with our breath, and by a blow-pipe excite a moft intenfe heat, capable of melting the moft refradory metals, platina excepted. It is true that the eolipile, by the mere conversion of water into fleam, will blow up a fire alfo; though, if the accefs of external air be denied, the blast of the eolipile will put the fire out. Probably the breath would do the fame ; but even this cannot be accounted a decisive proof of the oxygen be- ing totally exhaufted ; for the moift vapour with which the breath abounds may extinguifh the fire, even though fome fmall quantity of oxygen fhould remain in it. It is not, however, our bufinefs at prefent to enter minutely into fuch difcuflions. From what has been already faid, it + It is now acknowledged that common atmofpherical air contains a portion ot what Dr. Black and Dr. Prieftley have called fixed air; but this portion is fo fmall (not more than one fiftieth part, according to Dr. Anthony Fotherzill's Prize Diflertation, and none at all, according to Dr. Beddoes) I fay, this proportion is fo fmall, that we cannot fuppofe it to conftitute the quantity of fixed air thrown out by the breath, which is very confiderable. Befides, fixed air, of all others, is the moft readily abforbed ; and, indeed, if we could admit of abforption of any ball, of air in the prefent cafe, it certainly ought to be. that of fixed air; but where fuch a quantity is thrown out, we cannot well admit of any ablorpt ion. v«»«v» y»vW THE PLAGUE. H3 it is evident, that the abforption of oxygen by the blood, inftead of being indubitably eftablifhed, is of all things the moft uncertain; the requifites for determining it be- ing abfolutely beyond the investigation of any perfon, however accurate. We may indeed, with great labour and trouble, determine that fome part of the air is ab- forbed in breathing ; but what that part is, we are un- able to difcover from any chemical investigation. The opinion of the fimplicity of metals, and their being re- duced to a calx by the adhesion of oxygen, has been fo implicitly, and in a manner univerfally, received, that it has given a new turn to phyfiology, fo that, by a kind of analogical reafoning, the human body has been re- duced to a mere chemical apparatus, the operations of which may be calculated as we can do the event of ex- periments in a laboratory. But, after a very long and tedious contest, Dr. Priestley feems at laft to have over- thrown this dodrine of oxygenation, even in the inani- mate parts of the creation ; fo that we can much lefs apply it to the dodrines of life and animation. His experiments are publifhed in the third number of the Medical Repofitory, volume II, and fully demon- strate, that, though mercury abforbs oxygen dur- ing calcination, this is not the cafe with all metals ; that in many cafes the oxygen will unite with other fubftances in preference to the metal, which laft is ne- verthelefs reduced to a calx as though it had united with the oxygen ; that in many cafes the addition of weight gained by the calx is owing to mere water, &c. He has likewife fhown that phlogifticated air (azote) is not a Simple fubftance, as has been taught by the new che- mists, but confifts, as well as fixed air, of an union of oxygen with carbon, or at leaft with the black matter of burnt bones, with which he made the experiment. Thefe aerial fluids therefore being fo eafily convertible into one another, and the uncertainty of the changes in bulk which may occur in confequence of thefe conver- sions fo great, it is impoflible to fay whether a portion of the atmofphere in fubftance, i. e. both oxygen and azote, is abforbed, as phyficians formerly fuppofed; or whether A TREATISE ON whether a portion of oxygen air alone be abforbed, as Dr, Beddoes fuppofes ; or whether only the elaftic principle itfelf is abforbed, and the diminution in bulk made in confequence of the conversion of oxygen into fixed air; I fay, thefe matters depend on circumstances ^fo much beyond the reach of our fenfes, that if we come to any probable conclusion upon the fubjed, it muft be by analogical reafoning from other known fads, not from experiments made diredly upon the living body; which, in their own nature, muft, lways be extremely vague and uncertain. 5. That,'during the circulation, the blood charges itfelf with carbonic hydrogen air, is an aflertion which cannot be eafily admitted. It has already been obferved, that, by the air-pump, venous blood does not appear to contain any elaftic fluid whatever; and it is alfo certain, that animals cannot bear any quantity of air injeded into their veins. Dr. Girtanner himfelf tried feveral kinds, and all of them proved fatal. Having mjeded a confiderable quantity of oxygen air into the jugular vein of a dog, the animal raifed moft terrible outcries, breathed very quickly,, and with the utmoft difficulty; by little and little his limbs became stiff, he fell afleep, and died in lefs than three minutes. On injeding into the vein of another dog a fmall quantity of phlogifticated air, the animal died in twenty feconds. With carbonic acid gas (fixed air) a third dog died in a quarter of an hour. A fourth was killed in fix minutes by nitrous air.* From thefe experiments, had no others ever been made on the fubjed, it feems very probable, that no fpecies of air can be fafely admitted into the blood in its elaftic ftate. If any fuch therefore fhould naturally be produced in the body, it muft either be instantly thrown out, or difeafe muft enfue. Such objedions to the Dodor's theory are fo oatural, that we might have thought he would have forefeen and provided againft them. Inftead of this he grounds the whole upon fuch flender evidence as could not be admitted in the moft trifling matter. " An in- " cifion * Nitrous air is that Suffocating vapour which arifes when aqua fortis is poured upon metals When taken into the lungs it deftroys animal life more quickly than any other fpecies. ✓ THE PLAGUfe. i45 ** cifion (fays he) was made in the jugular vein of a fheep* " and the blood which came from it was received into a " bottle filled with nitrous air. When the bottle was " half filled, it was clofed. The blood coagulated im- " mediately; and a feparation of a great quantity of black- " ifh ferum took place. The day after, on opening the " bottle; a very ftrong fmell of nitrous ether (dulcified ** fpirit of nitre) was perceived; the nitrous air having ** been changed in part into nitrous ether by the car- " bonic hydrogen gas of the blood. This experiment ki proves, beyond a doubt, that the venous blood contains " carbonic hydrogen air; and that this air is not very m- " timately mixed with it, but may be expelled with the u greateft eafe." On reading the Dodor's account of this experiment; it muft be very obvious, that, however decidedly he may be of opinion that it proves, beyond a doubt the exiftence of hydrogen air in the venous blood, yet there is not one folid reafon; from what he fays, for fuppofing any fuch thing. How can any man determine from the mere fmell oiflieefs blood taken out of the body of the animal j and mixed with a poifonous vapour, what is the compofi- tion of human blood in the living body? In the cafe of any fubftance fufpeded to contain elaftic air, the air- pump will always afford an experimentum crucis. But we know that venous blood does not yield any elaftic vapour by the pump : if inftead of blood; however,- we fhould fill a portion of vein with beer, cyder, or other fermented liquor, it would instantly difcover, by its fwelting up; that it really contained air in an elaftic ftate. If theri from the tumefadion of the vein when filled with fer- mented liquor we conclude that the latter contains fixed air, why fhould we not, from the non-tUmefadion of it when filled with blood,- conclude that the vital fluid contains no air? If Dr. Girtanner was fo well aflured that the venous blood contains hydrogen air, he ought to have expelled fome of it from a portion of the blood, noted the difference between the blood which had loft its air, and that which had not, and then, by adding the air to it again, reftored. the blood to its former ftate, U Nothing i46 A TREATISE ON Nothing lefs then recompofition can prove the truth of a chemical analysis; as division can only be proved by multiplication, or multiplication by division. From all that has been faid, we may fairly conclude, that no proof can be brought fufficient to prove the ex- iftence either of oxygen air or any other fpecies of aerial fluid, in its elaftic ftate, in the blood. Neither can we prove that any part of the condenfable part of oxygen air is received by the breath in the lungs. It is, how- ever, probable that this condenfable part may be received into the ftomach with our food; that having patted through the various channels of circulation, and arrived at laft at the furface, it there refumes its aerial nature by combining with the fuperfluous heat of the body, and is evaporated through the pores of the fkin by infenfible perfpiration. The aerial vapour which pafles off by thefe pores indeed has been difcovered to partake of the nature ot fixed air ; but we know that this fpecies of gas always contains the balls of oxygen, being indeed compofed of it; and whether the oxygen be taken into the body in its pure ftate or not, the refult would undoubtedly be the fame ; for an union would be formed between it and the carbonic particles to be thrown off from the body. But thus we can never fuppofe the basis of oxygen or any other air to be a permanent part of the compofition of our* bodies; nor can the quantity of it be augmented by breathing any kind of air. The readiest way to in- creafe the quantity feems to be by drinking fermented liquors. Thus, if the body is too hot, the fuperfluous heat will have a proper fubjed to ad upon, viz. the con- denfable part of the fixed air ; and hence we may per- haps account for the very grateful and cooling fenfation produced by drinking thefe liquors in fome difeafes. With refped to the exiftence of carbon, charcoal or hy- drogen in the blood, it is probable that it exists in equal quantity at all times, being indeed the fundemental ma- terial of the whole body, and probably only a modifica- tion of that duft from whence man was originally taken.'* When * In one of Dr. Prieftley's papers above quoted he fays, that charcoal is en- tirely of vegetable origin j but the converfion of vegetable into animal mat- ter, THE PLAGUE. When the blood therefore grows very black, when the teeth are covered with a black fordes, the hands become foul, &c. we may fay, indeed we too furely feel, that, in such cafes, there is a propensity in the body to return to its original ftate of diflblution ; but there is not one folid reafon for fuppofing the proportion of its materials to be varied; that there is a colledion of oxygen in one part, hydrogen in another, or in fhort that nature can admit of any fuch difproportion taking place. 6. We muft now confider Dr. Girtanner's account of the origin of animal heat, which is, that, " during " the distribution of the oxygen through the fyftem, " the heat which was united with this oxygen efcapes ; " hence the animal heat;" and, " that the great capa- " city of the arterial blood for heat is owing to the oxygen " with which it is united in the lungs."—This leads us to confider in a more particular manner the dodrine of heat, a fubjed hitherto much lefs investigated than the importance of the fubjed requires. What little we do know of this matter feems to be almoft entirely owing to Dr. Black, who hath difcovered fome very remarkable phenomena unknown to former philofophers. His dif- covery here, as in that of fixed air, was accidental. Mak- ing experiments on the water of different temperatures, he found that the mixture would always be an arithme- tical mean betwixt the two quantities mixed. Thus, on ter, which we daily fee, is an undoubted proof that there cannot be any ef- fential difference between them. Even the bones are undoubtedly produced from vegetables in fuch animals as feed upon vegetable fubftances; fo that even the calcareous earth they contain is plainly of vegetable origin. We may fay indeed that the calcareous particles had a previous exiftence in-the vege- tables ufed by the animal as food ; but we may fay the fame of the particles of the blood, flelh, horns, &c. Befides, Dr. Prieftley has fhown that every particle of charcoal may be volatilized into inflammable air, with as great ac- curacy as any human experiment can be made; fo that in this eafe the calca- reous particles, if any fuch there were, fhowed themfelves to be as much charcoal as the reft. In the 74th volume of the Philofophical Tranfa&ions, Mr. Watt has fhown, that dephlogifticated fpirit of nitre may be changed into the fmoking and phlogifticated kind by means of red-lead or magnefia alba, as well as by charcoal; of confequence there can be no eflential difference even there. In lhort, fo wonderful and multifarious are the transforming or metamorphofing powers of nature, that every attempt to find out a fubftance upon which thefe powers cannot act, will be found altogether vain, and our beft conducted and moft plaulible experiments, made with a view to dif- cover the ultimate compoiition or what we call the elements of bodies, will be found mere inaccuracy, bungling and blunder. A TREATISE ON on mixing water at 50 degrees with an equal quantity at 100, the temperature of the mixture would be 75 degrees ; but if inftead of ufing water only he took fnow or ice for one of the quantities, the mixture was no lon- ger an arithmetical mean betwixt the two temperatures, but greatly below it ; fo that a quantity of heat feemed to be totally loft and in a manner annihilated. His ati tention was engaged by this unexpected phenomenon, and, profecuting his experiments, he found that, when water was converted into ice, it really became warmer than it was before; and, by keeping the fluid perfedly ftill cluring the time that cold was applied, he was able to cool it to 27 degrees of Fahrenheit's thermometer, which is five degrees below the freezing point ; but on fhak- ingthis water fo cooled, it was instantly converted in- to ice, and the thermometer rofe to 32. On reverfing the experiment he found that mere fluidity in water is not fufficient to melt ice. A confiderable degree of heat is neceSTary ; and even when this is previously gi- ven to the water, the whole becomes as cold as ice by the time that the ice is melted. The refult of his ex- periments in fhort was this : Water, when frozen, ab- forbs an hundred and thirty-five degrees of heat before its fluidity can be reftored : that is, fuppofing a pound of ice at the ternperature of 32 to be mixed with a pound of water at the temperature of 32, by adding 135 degrees, fo that the temperature of the water is augmen? ted to 167, the ice will indeed be melted, but the tempe- rature of the whole quantity of liquid will be reduced to 32. In this cafe therefore the heat manifestly aflumes two different modes of adion ; one in which it ads in- ternally upon the fubftance of the body, without being fenfible to the touch, while in its other state it hath no effed upon the internal parts, but affeds bodies on the outside. The former ftate therefore the Dodor diftin- guifhed by the name oilatent, the latter by that of fen- fible heat. The fame theory was applied to explain the dodrine of evaporation, and that in the moft decisive and fatis- fadory manner. The Dodor found, that, in the diftillation THE PLAGUE. 149 diftillation of water, much more heat was communi- cated to that in the worm-tub of the still, than could be fuppofed neceflary to raife the water diftilled to 212 degrees, which is the utmoft that water can bear. In profecuting the experiment he found the quantity of heat abforbed by the water, when raifed into vapour, truly furprifing; no lefs than a thoufand degrees; an heat more than fufficient to have made the whole quan- tity of fluid that came over red hot. Some objec- tions, however, were made to this theory, even by the Dodor's friends. Mr. Watt, particularly, though he could not deny the theory derived from Dr. Black's experiments, yet fuggefted one, which, had it proved fuccefsful, would have overthrown the whole. It was this : Let water be diftilled in vacuo, where it boils with a heat of 97 degrees, and the operation muft be carried pn with much lefs fuel, and with much greater eafe, than in the common mode. It was faid that, in this experi- ment, Dr. Black was equally concerned with Mr. Watt; but, in a perfonal converfation with the Dodor himfelf, he afiured me that he had no farther concern than fore- telling that the experiment would not fucceed, which it feems did not. The event was as follows : Mr. Watt, determining at all events to try the experiment, caufed to be made a copper retort and receiver, joined together in one piece. In the receiver he pierced a fmall hole, and, heating both retort and receiver, plunged the latter into cold water. The confequence was, that a conside- rable quantity of water entered the vefTel, and was easily poured back into the retort, as a fubjed for. distillation, A fire being now applied, the water was foon raifed into fleam, which filled both retort and receiver, and in a great meafure expelled the external air. The fmall ori- fice in the receiver being now clofed, and the receiver itfelf plunged into cold water, the diftillation went on in vacuo ; for, as foon as any of the fleam was condenfed, the fpace which it had occupied (according to Dr. Black one thoufand and fixty-fix times more than the ori- ginal water) was become abfolutely empty, and more Seam, rarefied, not by any quantity of fenfible heat, but A TREATISE ON but merely by that which it contained in a latent ftate, would occupy the place of the former. The event of £he experiment fhowed trie truth of Dr. Black's theory. The water boiled, and fleam was raifed as well as if accefs had been given to the air ; but with this difference, that the upper part of the distilling veffel was never heat- ed above what the hand could easily bear. With the water in the cooler it was quite otherwife. It became hot as ufual, and, by the quantity of heat it received, plainly demonftrated that the vapour, though destitute of moft of its fenftble heat, yet contained an immenfe quantity in a latent ftate. The faving of fuel therefore in the pradice of distillation, which was Mr. Watt's ob- jed in making the experiment, was quite trifling, and not equal to the trouble of filling the retort with liquid. The dodrine of latent heat thus eftablifhed, furnifhed a folution of many phenomena which could not former- ly be explained in a fatisfadory manner. Thus the melting of all kinds of fubftances was found to be owing to an abforption of heat, while their condenfation was at- tended with the contrary. Fluidity in all cafes was ex- plained on the fame principle; and the more heat that was abforbed, the more fluid the matter became. Thus water, when in a condenfed or folid ftate, abforbs 135 degrees of heat before it becomes fluid. A thoufand de- grees more convert it into vapour, and at laft, by paf- fing through the intenfe heat of a glafs-houfe furnace, it is converted into a brilliant flame, and augments the heat of the furnace to a great degree. Hence the prac- tice in glafs-houfes of throwing water into the afh-hole, the vapour of which, by parsing through the burning fuel, makes the furnace much hotter than it was. In a fimilar manner were explained the phenomana of crystal- lization, the dudility of metals, the heat produced by hammering them, and the hardnefs produced by the ope- ration, as well as the operation of annealing, &c. One other phenomenon, a very curious one, fhall be noticed, on account of its being conneded with the fubjed of this treatife. It is this : Let a fmall veflel filled with vitri- olic ether be put into a larger one of water, and both included THE PLAGUE. JSl included in the receiver of an air-pump. On exhaust- ing the air, the ether boils, and is converted into va- pour, while the water freezes. This fhows that heat does not always ad equally upon furrounding bodies, but has a tendency to enter fome in preference to others ; and from other experiments it appears, that this pro- perty has a confiderable connexion with the density of the bodies concerned. Thus one ftep was gained, and it was univerfally ad- mitted that heat, in fome cafes, entered bodies, and in others was thrown out of them ; but now the queftion arofe, What is heat; and by what laws is it regulated, or from what fource is it derived ? Here Dr. Black himfelf was at a lofs ; for, as he fuppofed cold to be a mere non-entity, and only to confift in a comparatively fmaller degree of heat, fome phenomena occurred which would not easily admit of folution upon fuch an hypo- thefis. With thefe Dr. Black did not meddle much, but others were bolder. Dr. Irving, Profeflbr of Che- miftry at Glafgow, undertook to explain the whole mystery of latent heat upon the single principle of attradion. One of the moft puzzling phenomena in the way of Dr. Black's theory had been, that in fome cafes heat and cold feemed to repel each other, and a very remarkable in- stance of this was, that, in the morning, a little before funrife, when the rays of light pafs through the atmof- phere, a little above the furface of the earth, the air then becomes manifestly colder than even at midnight. Dr. Irving's explanation of this was, that that the fun's rays atlracled heat from the atmofphere, and thus rendered it colder. Such at leaft was the explanation given in an inaugural diflertation by Dr. Cleghorn, one of Dr. Ir- ving's fcholars ; for the Dodor himfelf delivered his opinions only to them. In other cafes he fuppofed that different fubftances had different capacities for receiving heat ; and, of confequence, fhould the form, or rather the internal confiitution, of the body be changed, the capa- city of it for receiving heat muft alfo be changed ; and as an attradion fubfifts, or is fuppofed to fubfift, between heat and all other fubftances, it is plain that while this attradion j52 A TREATISE ON attradion fubfifts, if the capacity of any fubftance for receiving heat be augmented, it will imbibe much more than it would have done had its former constitution re- mained. Thus water in its liquid ftate contains a cer- tain quantity of heat; we may therefore fay that water has a capacity for receiving heat equal to one to ten, or what we pleafe. Vapour has a capacity for containing heat ten times greater than water. Water therefore, when converted into vapour, will imbibe ten times the quantity of heat that the water contains; and, again,on being re-converted into water, the capacity becoming what it was before, the fuperfluous quantity muft be thrown out, as in Dr. Black's experiments. In like manner, when a metal is melted by the fire, the capacity. of it for receiving heat is changed : of confequence a great' quantity is imbibed, and again expelled by the change of capacity which takes place on its becoming folid ; and thus, from the change of capacity, in differ- ent fubftances, every phenomenon was folved. This dodrine of capacities did not give general fatis* fa&ion. Dr. Black himfelf faid of it, that it was nei- ther probable nor ingenious ;* notwithstanding which, it continued to be received, and even very generally adop- ted. Dr. Crawford, fo well known for his writings on this fubjed, has adopted the idea, and Dr. Girtanner, in the paflage above quoted from him, appears to be of the fame opinion. The dodrine, however, had feveral op- ponents, among whom were the Monthly Reviewers; In their account of Nicholfon's Firft Principles of Che- miftry, they exprefs themfelves in the following manner " We only wifh, that, in the dodrine of heat, he had " avoided, which he might easily have done, Dr. Craw- " ford's idea of bodies having different capacities for " heat. In the melting of ice, for inftance, a quan- " tity of heat is abforbed, without any increafe of the " temperature, that is, without making the water fenfi- *' bly warmer than the ice before its liquefadion ; which , " is * Thefe words arefobe found in the M. S. Copies of his ledlures circulated at Edinhjurgh. Dr. lib k himfelf r " pacity for heat, or being able to hold more of it, than " the ice ; and, in like manner, when converted into " vapour, its capacity is further increafed, or it can hold " more ftill. This appears to us a very unchemical, and " a very inadequate idea of the matter : for, admitting " water to have a greater capacity than ice, how is the 11 change from one ftate to the other to be effeded ? " Can the properties which a body is found to poflefs, " after a change has taken place, be afligned as a caufe " of the change itfelf ? Or will it be faid, that the heat " firft enlarges the capacity, and then hides itfelf in that " capacity fo enlarged ? We fhould think it much bet- " ter to fay, confonantly with the phenomena of other " combinations in chemiftry, that a certain quantity of " heat, uniting with the ice, firft liquefies it, as a certain