Chapter XIII: Section III (7)

Mr. Watt in a letter to Dr. Beddoes gives an account of a kind of air, seemingly more noxious than any yet discovered, which he produced by distillation from flesh and from wool. The effects upon himself were so disagreeable that he determined to make no more such experiments, lest he should to his own hurt discover a mode of producing some grievous disease. But we cannot, from an artificial air of this kind, argue to a natural one; as the one produced by Mr. Watt was totally different from any species of air naturally known. All that we can say is, that, as far as we can trace the connexion between our bodies and the different kinds of air which may be breathed, the latter act chiefly by the heat they contain, and which they impart to the body in various proportions; by which means the latent or sensible heat of the blood, and consequently of the whole body, may be occasionally augmented or diminished. Thus the body may be considerably altered in its constitution, and rendered more liable to diseases than it was before; but still it is found that diseases continue to appear at uncertain intervals, though all the causes we are able to discover, or at least all that are constantly evident to our senses, continue to operate without intermission. Though the obvious qualities of air and climate therefore may _predispose_ to an epidemic, we cannot affirm any thing farther: the direct _cause_ is always different, and hath hitherto so much eluded our researches, that we can have little hope of discovering it, except by reasoning from facts less obscure.

8. In all the operations of nature which we have access to investigate, the action of electricity is so much concerned, that we can scarce suppose it to be wanting in any of them. That it is concerned in preserving the health of the human body is likewise certain, if it be the fluid which acts in the nerves, as most probably it is. But whatever preserves health will also bring on disease, if it be applied to that purpose; and we have already seen that this fluid is capable of bringing on the most dreadful symptoms, viz. mortification in its highest stage, fever, convulsions, bilious discharges, lethargy, &c. If it be capable of producing all these, can we say that it is not capable of producing those of an inferior kind, or of varying diseases and symptoms without end, according to the immense diversity of its action? It may be said that this disease was occasioned by a violent stroke of electricity, similar to lightning; but how many people have declared, that, in the beginning of some violent epidemics, they have felt a sudden stroke at the time of seizure! Dr. Hodges mentions this in the plague of 1665 at London, but treats the accounts as effects of a distempered imagination. Procopius relates the same of the plague in his time, viz. that many of the diseased felt a stroke. It is true that they said such strokes were given by spirits in human shape, in which we know they must have been deceived; but, though they were mistaken in supposing that they had been struck by a spirit, it does not from thence follow that they felt no stroke at all. The people mentioned by Dr. Hodges did not say that they were struck by a _spirit_, yet he treats their accounts with as great contempt as though they had. Where people have no interest in deceiving, we ought certainly to look with a favourable eye upon their testimony; for, even although some part of it should be incredible, we have still reason to believe that there is some foundation for what they say. Thus, the poor sailor, so much frightened at the sight of a large bat in New Holland, was certainly mistaken in saying that he had seen the devil; he was even mistaken in saying that he had _horns_;[92] but from all this it would have been doing him great injustice to say that he had seen nothing. In like manner, when numbers of people in Procopius’s time said that they were struck by spirits, when we find others in Dr. Hodges’s time saying that they were struck by some invisible agent, when we know that electricity _can_ strike in an invisible manner, it certainly is more reasonable to conclude that violent diseases sometimes do begin by an electric stroke, than that _all_ who said they were struck in this manner were madmen or liars.

[92] In the account of this sailor’s speech a most essential part of
the devil’s character was omitted. The speech, according to Capt.
Cook, was, that the devil “was about the size of a one gallon keg,
and very like it. He had horns and wings; and he was so near, that,
if I had not been _afear’d_, I might have touched him.” (See p. 105,
n.)

It may now again be asked, if the plague, or violent epidemics, be produced by electric strokes, why are they not much more frequently felt, or by what are those milder diseases produced which are not accompanied by any sensible stroke? Here we can be at no loss to say, that whatever produces the highest disease, may also produce the lowest. But, besides this argument, we have positive evidence that commotions in the electric fluid will not only produce sickness, but very extraordinary and seemingly miraculous effects upon inanimate bodies. It has frequently been remarked that people are sick during the time of earthquakes, when the electric matter is in violent agitation. This has been accounted for from the motion of the earth, as the motion of a ship produces sea-sickness. But Dr. Hillary mentions a slight earthquake in Barbadoes where people were affected with sickness and vomiting for _some hours_ after the phenomenon had ceased altogether; which undoubtedly shows, that a certain state of this fluid will disorder the human body, independent of every other circumstance, either of the heat or cold of the atmosphere, or the oxygen, hydrogen or azote contained in it. Again, we find that a certain state of the electric matter is not only capable of producing very extraordinary effects by itself, but also of communicating a power to the human body to do the same. A good number of years ago, a powder-mill near London was blown up. The explosion, as might be expected, was violent and tremendous; but the most remarkable circumstance was, that the electric matter, for a great way round, was thrown into unusual, though invisible, commotions, which discovered themselves by the rattling and breaking of china dishes though sitting apparently undisturbed upon their shelves. This phenomenon did not suddenly cease, and, during the time of it, some people appeared to be infected by an electric _contagion_; the power of breaking china seemed to reside in their bodies, so that if they approached or touched this kind of ware, it would instantly fly to pieces. Accounts of this extraordinary circumstance were published in many of the periodical works of the time, particularly in Dodsley’s Annual Register; and the fact seems to be established beyond controversy. It proves that what has been advanced by Dr. Priestley concerning electrical operations, on a small scale, holds good also on a large one, viz. that the fluid, when once set in motion, is not easily quieted. It establishes the fact, also, that by great explosions of gun-powder the electric matter is violently agitated; and the consequence of these agitations we cannot know. It may be said, indeed, that in the operations of nature the electric matter is often violently moved without any sickness taking place; neither in fact did any ensue at the time the powder-mill in question was blown up. But it must be remembered, that, in the ordinary course of nature, if the electric matter is moved, a receptacle is also provided for it. In a thunder-storm, where immense discharges of electricity are made from one cloud, there is another cloud of an electricity opposite to the former ready to receive them, or if not, the earth itself is frequently struck. In eruptions of volcanoes, the smoke receives the electricity discharged, and becomes charged with lightning of a more dangerous kind than that of ordinary thunderstorms; and Sir William Hamilton relates, that in the great eruption of Vesuvius, in 1794, lightning of this kind proceeded from the smoke for no less a space than _seventeen_ days. But in artificial commotions of this fluid, where nature has not provided any receptacle, the phenomena must be quite different; and though we may with safety to ourselves interfere with the operations of fire and electricity to a certain degree, yet we may at last rouse these terrible elements into such action as will prove fatal to great numbers. Hence possibly may arise in part some of those sicknesses which take place after battles, in violent sieges, &c. An instance of this is said to have happened at Valenciennes, when last besieged by the Duke of York. A disease prevailed chiefly among women, children, and persons of a weak constitution; great numbers of whom died so suddenly that it was at first thought to be a plague, until it was found not to be infectious. The blood was found greatly dissolved, and the physicians ascribed it to the monstrous bombardment and cannonading which took place during the siege. Such was the account published in some of the newspapers of the time, and from the subsequent considerations it will not seem improbable that such things may take place.

From the experiments of Mr. Bennet (an English gentleman who has made several discoveries in electricity) it appears, that we can neither brush a piece of chalk, open or shut a book, or do several of the most trifling actions, without agitating this subtile fluid in a perceptible manner. It is well known that in some cases we cannot stroke a cat’s back without making the electric matter visible, and in some positions, by putting our fingers near the ears of the animal, very pungent sparks will be received. If then we can neither open or shut a book, if we cannot stroke a cat’s back, or approach a finger to her ear, without agitating the electric fluid, is it reasonably to think we could burn a book, or kill a cat, without doing the same? Certainly it is not. If we cannot burn a book or kill a cat without affecting this fluid, it cannot be supposed that we can burn a house or kill a man without producing a still greater commotion; and in proportion to the extent of our devastations, and the multitude of our massacres, the invisible agitation of this element must become still greater and greater. In all these transactions it must be remembered that the fluid is forced out of its natural mode of action; for electric matter is made for the preservation, not the destruction, of life: but if, by long continued and extensive application of its power to a contrary purpose, we in some measure pervert its action, no wonder that we then feel the consequences of our own proceedings by its partly turning its power against the human race altogether.

Again, the human body is not made for the habitation of an infernal spirit, but for one of a quite different character. The boisterous passions of fury, discord and hatred ought never to disturb the mind, which is made for the habitation of endless peace and joy. The tumultuous passions are enemies to health; and this is so well known to physicians that they are very careful to prevent their patients from being any way ruffled or disturbed by violent passions. It is true these passions act upon the rational soul, which we may suppose to be distinct from that merely animal spirit, probably no other than the electric fluid, which runs along the nerves; but experience shows that each of these can act upon the other; a disorder in the body, particularly in the nervous system, will sometimes disturb the rational soul in such a manner as almost entirely to deprive it of all its faculties; while on the other hand a violent commotion in the rational soul may at once extinguish all the powers of life, as has already been shown from Zimmerman. Now, let any one consider what must be the sensations of those who engage in war. Whatever pity or humanity may be pretended, it is evident that in the day of battle all these sensations must give way to horror and fury on the part of the conquerors, and terror and dismay on that of the vanquished. That these passions never do entirely subside, is evident from the treatment of conquered countries and conquered people. When Jenghiz Khan beheaded his prisoners by hundreds of thousands, when Tamerlane pounded them in mortars, when Khouli Khan caused those who offended him to be carried from place to place, and a piece of flesh to be cut from their bodies at each stage, what must have been the sensations of these miscreants, and those whom they employed in such horrid scenes? On the other hand, what must be the sensations of those who see their dearest relations torn from them and slaughtered or treated even worse than if they were; themselves driven from their peaceable abodes to wander like beasts, while their cruel enemies exult in the miseries they have brought upon them, and glory in doing all the mischief they can, and spreading devastation as wide as possible? Thus, every passion, inimical to health, must, on both sides, be carried to its utmost height; and if these horrid scenes overspread a great part of the earth, for hundreds of years together, is it any wonder that plagues should ensue? If man, forgetting the dignity of his nature, converts the habitation assigned him by his Maker into a kind of hell, and himself into a devil, can we wonder that, in such circumstances, the spirit of life, originally appointed for his use, should become to such a being the spirit of death? Dr. Moseley seems to speak slightly of Helmont for assigning _moral_ causes to fever; but if we consider the matter attentively it will certainly be found that the moral conduct of the human race in general has more connexion with the diseases which befal them, than we are perhaps willing to believe.

Most authors speak of some hidden, unknown and unsearchable power in the atmosphere as the occasion of plagues and other epidemics; and, from what has been already laid down, it seems by no means improbable that this hidden power resides in the electric part of it. But we know that electricity proceeds from the earth, as well as from the air; so that in some countries the evaporation of electric matter from the earth may affect the health of the inhabitants, as well as the constitution of the atmosphere. Hence some spots may be naturally unhealthy, and incurably so, independent of either the perceptible or imperceptible properties of the air; their healthiness may occasionally increase or decrease by means entirely beyond the reach of our investigation. Here then our inquiries must stop. We may indeed make a general conjecture that such differences are produced by the action of the electric matter; but, unless this action be pointed out, and some connexion traced between the situation of the country and a particular mode of action of the fluid, we may as well own our ignorance at once.

9. From all that has been said, then, we may conclude, that none of the obvious properties of the atmosphere, or of any constituent part of it, or of any variation in the proportion of its ingredients, can be accounted the cause of epidemic diseases; that the hidden constitution of the atmosphere may with probability be attributed to the agency of the electric fluid, and that by the action of this secret cause, along with the other more obvious properties of the air, such as heat or cold, moisture or dryness, &c. the human body may be so predisposed to diseases, that they will readily break forth; and that the conduct of mankind themselves may greatly contribute to this predisposition; the question then is, supposing every thing to be thus laid, like a train of gun-powder, what is the spark which first sets it on fire. Does the disease arise spontaneously in the first person affected by it, or does it come from without?

In answer to this we must in the first place observe, that the accounts of all plagues mentioned in profane history trace their progress from one place to another; whence the probability is, that at its origin the disease was confined to a few, perhaps to a single person. In very few cases, however, has it been possible to trace it to an individual; and, even when this has been done, the unfortunate individual is always said to come from some other place. The instance quoted from Dr. Moore is perhaps the only one upon record where the plague arose spontaneously in any person separated from society; and from a single instance little can be inferred. In those terrible examples we have given of people being burned to death without any accident from terrestrial fuel, the agent seems almost certainly to have been electricity. In the plague of Procopius, said not to have been infectious, the strokes complained of by many patients seem to indicate an action of the same fluid. The same in the plague at London, which was infectious, and likewise of others. But, in cases of plagues which are not infectious, another question arises--By what means do such diseases spread from place to place? for even this dreadful pestilence of Procopius did not overspread the earth at once, but is said to have begun at Pelusium in Egypt. To this no answer can be given. To suppose an omnipresent contagion in the atmosphere, proceeding either from contagion or any thing else, cannot be admitted; for upon this supposition the whole world must have been infected at once. The cause, whatever it was, plainly moved from one place to another, or was successively generated in different places. Recourse may be had to the precipitation of the contagious matter of former plagues from the atmosphere; but to account for this in succession will be found very difficult; and the same difficulty will attend every other solution which may be attempted. Mr. Gibbon indeed censures Procopius for supposing it not to have been infectious; and perhaps the spreading of the disease by infection is the only way by which we can account, in a satisfactory manner, for the way in which it diffused itself over the world, which was, by first infecting the maritime places, and afterwards those which were more inland; always visiting the second year those whom it had spared the first.

10. Lastly, to form some idea of the nature of contagion, or infection, as it is more properly called, we must consider, that as the ethereal fluid, acting as heat, pervades the human body, so doth it likewise under that particular modification which we call electricity. Some kinds of air, indeed most of those with which we are acquainted, seem to act by augmenting or diminishing the latent or the sensible heat of the body. Such, when taken in moderate quantity, may produce slight diseases, as head-ach, &c. and, when taken very largely, may even put an end to life at once, either by rarefaction of the blood and rupture of the small vessels, as is the case with fixed air, or by oppressing the lungs entirely with their basis, which cannot be thrown out by the breath as in ordinary respiration. Others may affect the electricity of it, or what in this treatise has been called the _vital spirit_, as well as the latent or sensible heat. The consequence of this will be diseases of a more serious nature; for upon this principle in all probability depend not only the secretion and proper regulation of the nervous fluid, but what has been called the _crafts_, or proper consistence of the blood and other fluids. Hence it is possible that such an instantaneous shock may be given to the body, as will not only injure the organization in an irreparable manner, but may be felt throughout the whole body like an electric stroke, even though there be no visible fire, or sensation of burning, as in the case of the Italian priest and others, who perished in such a miserable manner.

Formerly all acute diseases were supposed to depend on morbific matter taken into the body, and absorbed by the blood: the cure was thought to be accomplished by the expulsion of this morbific matter from the body by sweat, or some of the other natural evacuations. The doctrine was attended by many difficulties, and in many cases did not admit of a satisfactory explanation. It was therefore laid aside, and the debility or excitement of the nervous system arose in its place. But this new system admitting of _miasmata_ and _contagion_, it was plain that morbific matter still kept its ground. With a view, it would seem, to render the nervous theory more complete, it has been found necessary to deny the doctrine of contagion and infection entirely. This has been done, wherever there was a possibility; but the phenomena of the small-pox and measles, as well as those arising from poisons, still militated strongly in favour of morbific matter. To avoid the force of arguments drawn from these sources, the doctrine of absorption was denied, and contagions of all kinds were said to act immediately upon the nervous system without affecting the blood or other fluids. At last the matter seemed to be decided by the experiments of the Abbe Fontana on poisons. He found that some proved fatal by being mixed with the blood, others by being applied to the nerves, and others by being taken into the stomach. Even this did not give satisfaction. It was contended that the effects of poisonous bites were too quick to be accounted for on the principle of absorption; that, after the most violent symptoms had commenced, they might be removed by cutting out the part affected; and consequently that, instead of any absorption by the blood, we were only to believe that the nervous system was irritated.

“Poisons, (says Dr. Girtanner) remedies, and, in general, all surrounding bodies, acting only on the irritable fibre, it follows that they act upon the system in a similar manner, and that every substance capable of producing the greatest possible effect upon the fibre, that is to say, every substance capable of exhausting all the irritability both of the fibre itself and of the system, in an instant, as for instance, laurel water, or white arsenic, is also capable of producing all the inferior degrees of action, either by acting on a fibre less irritable, or by acting upon the same fibre, but in a less quantity. Laurel water, opium, white arsenic, ammoniac, are of course both medicines and poisons capable of _healing_, as well as of _producing_, _all maladies whatsoever, without exception_.[93] And this is confirmed by a number of experiments which I have made upon different animals. This _truth_ seems to me _of the utmost importance_; and the Abbe Fontana, who made more than six hundred experiments to prove that ammoniac is no remedy against the bite of a viper, would have saved himself the trouble, had he known it. If, instead of applying the venom of the viper to so many animals, and afterwards applying ammoniac to the wound, he had made a single comparative experiment, and applied ammoniac to a wound made by a lancet that was not poisoned, he would have found that ammoniac itself, applied in this manner, would have produced a disease exactly analogous to that caused by the venom of the viper; and, consequently, so far from removing the malady, must necessarily increase it, by exhausting the irritability of the fibre in a much less time than the venom of the viper by itself was capable of doing. Mr. Fontana has made more than six thousand experiments upon the poison of the viper; he employed more than three thousand vipers, and caused to be bit more than four thousand animals; and the conclusion he drew after this truly enormous number of observations was, that the poison of the viper kills all animals, and produces the disease by its action on the blood. But why did Mr. Fontana neglect to make the decisive experiment, the _experimentum crucis_ of Bacon? It is well known that frogs, and many animals with cold blood, live a long time without the heart, and entirely deprived of blood. If therefore the poison of the viper kills animals by its action on the blood, it will not destroy frogs without blood. But experiment contradicts this reasoning. The poison of the viper will kill frogs without blood in as short a time as it kills those animals who have not lost their blood. It is not therefore by its action upon the blood that the venom of the viper destroys animals; and thus does it happen that a single experiment frequently overturns all that _six thousand_ other experiments have apparently established. According to my experiments, poisons operate upon the blood just as they do upon the muscular fibre, by depriving it of its principle of irritability, or of its oxygen. After having made this observation upon the experiments of Mr. Fontana, I must do him the justice to add, that I have found all his experiments very accurate, and that in all those which I have repeated, the result has been exactly conformable to the account given by him; it is in his conclusion only that he appears to be deceived.”

[93] This is an assertion so extravagant, that is difficult to
imagine what could induce any one to make it. Did our author ever
hear that laurel water, &c. produced the venereal disease, the
plague, yellow fever, gout, stone, small-pox, &c. &c. or to what
patients and in what diseases did he ever administer this remedy
with success? I mean not to deny that these substances will cure
_some_ diseases as well as produce others; but such an unqualified
expression that they can not only produce but cure all diseases
without exception, never can be admitted.

On this I must in the first place observe, that since _philosophers_ and _truth_ seem to be so far distant from each other that even _six thousand_ experiments cannot bring them together, it were greatly to be wished that in their researches they would pay a little more regard to humanity. If the Author of Nature has set man at the head of the creation, if inferior animals must patiently resign their lives to preserve ours, are we therefore authorised to torment and put them to death by thousands for every idle whim that comes into our heads? After Spallanzani, Fontana, Girtanner and a multitude of other learned _barbarians_ had cut in pieces, boiled alive, poisoned and tortured thousands of inoffensive animals, new massacres it seems must be made, and new tortures inflicted, because an _experimentum crucis_ is still wanted! If knowledge is to be obtained only by such means as these, it certainly must be derived from a very polluted source.

2. The experiment on which Dr. Girtanner builds so much is far from being above suspicion. Though we may cut the heart out of an animal, and let it bleed as freely as possible, yet we certainly overrate our abilities if we say that _all_ the blood is taken out of it. The more perfectly an animal is bled, the less irritability it has; which gives a reasonable suspicion, that, if _all_ the blood could be taken away, the irritability would cease entirely. In frogs, and all other cold blooded animals, the blood contains fewer red globules than in such as are warmer; the circulation is more languid than in such as have warm blood, and, of consequence, the blood will retain its irritability for a longer time, and it will likewise be more difficult to deprive the body of all its blood. In making this experiment, therefore, Dr. Girtanner ought to have brought unexceptionable proofs that he had deprived the frog of _all_ the blood it contained. But, as this was not done, we shall be ready to suspect that some was left; in which case we should be still as uncertain as before whether the poison acted on the irritable fibre, or on the blood. But the decisive experiment, or _experimentum crucis_, seems to have been made by Fontana himself, by injecting a little of the diluted poison of the ticunas into the jugular vein of a rabbit. Here the poison was applied to the blood itself. It could get at no other part of the fibre but the inside of the vein, which is not accounted very irritable; and the quantity injected was so small, that the Abbe thought his experiment had failed; yet the animal died as if by lightning. The moment he turned his eyes towards it, it was absolutely dead, without discovering the least convulsive agony, or other sign of some little life remaining, generally observable for some time in animals killed by the common methods. On applying the same poison to a large nerve of another animal of the same species, no injury followed.

3. The dispute is of no consequence, and the experiment will prove the same thing whether we suppose the poison to act upon the irritable fibre (the nerves and muscles) or upon the blood. The only important point to be ascertained is, whether there be in nature any substance which, applied to the internal parts of the body, or to a wound, will instantly disorder the whole in such a manner as to bring on a violent disease which may prove mortal in a short time. If any such there is, that substance, whether solid or fluid, visible or invisible, may with propriety be called _contagion_; and if any such proceeds from the body of a diseased person to one in health, the vapour so proceeding is _infection_. As to the _mode_ of its operation we are little concerned; the sudden manner in which people are affected shows that poisons kill by suppressing in a very short time the principle of life, which seems to be analogous to electricity, or rather the very same with it; neither is it more incredible that the poison of a serpent should kill by disturbing the natural electricity of the body, than that the stroke of a torpedo, or electrical eel, should kill by the same means. The only difference is, that, in the case of poisons, the pernicious substance is introduced into the body itself; in the torpedo, it comes with violence from without. The former we may compare to the silent discharge of an electrified jar by a point, the latter to its discharge with a violent flash by a knob. But that in poisonous bites the blood is greatly affected, and that in a very short time, we certainly know. There are some kinds of serpents whose bites are so suddenly fatal, that no cure can be applied: one of these, called the small _laharra_, is mentioned by Mr. Bancroft in his Natural History of Guiana. Mr. D’Opsonville, in his Philosophic Essays, takes notice of one in the East-Indies, which he calls the _poison serpent_ or _serpent poison_, which seems to be as bad as the _laharra_ mentioned by Bancroft. This too is but small, viz. two feet long, and very slender. Its skin is freckled with “little traits of brown, or a pale red, and contrasted with a ground of dirty yellow: it is mostly found in dry and rocky places, and its bite proves mortal in less than one or two minutes. In the year 1759, and in the province of Cadapet, I saw several instances of it; and, among others, one very singular, in the midst of a corps of troops, commanded by M. de Bussy. An Indian Gentoo merchant perceived a Mahometan soldier of his acquaintance going to kill one of these reptiles, which he had found sleeping under his packet. The Gentoo flew to beg its life, protesting that it would do no hurt if it was not first provoked; passing at the same time his hand under its belly, to carry it out of the camp; when suddenly it twisted round, and bit his little finger; upon which this unfortunate martyr of a fanatic charity gave a shriek, took a few steps, and fell down insensible. They flew to his assistance, applied the serpent-stone, fire, and scarifications, but they were all ineffectual; his blood was already _coagulated_.[94] About an hour after I saw the body as they were going to burn it, and I thought I perceived some indications of a _complete dissolution of the blood_.”

[94] There must certainly be some error here; for as he mentions a
_dissolution_ of the blood so soon afterwards, we should think it
impossible that any coagulation would have taken place. Perhaps the
word only imports that the circulation was completely stopped.

The bite of the _brulan_ or _burning serpent_, according to the same author, is almost as terrible. “This is nearly of the same form with the last, its skin is not quite so deep a brown, and is speckled with dark green spots: its poison is almost as dangerous, but it is less active, and its effects are very different. In some persons it is a devouring fire, which, as it circulates through the veins, presently occasions death; the blood dissolves into a lymphatic liquor resembling thin broth, without apparently having passed through the intermediate state of _coagulation_,[95] and runs from eyes, nose and ears, and even through the pores. In other subjects the poison seems to have changed the very nature of the humours in dissolving them; the skin is chapped and becomes scaly, the hair falls off, the members are tumefied, the patient feels all over his body the most racking pains, then numbness, and is not long in perishing.”

[95] The blood certainly does not coagulate in the vessels, in any
case whatever, unless by injecting something into them.

From these accounts it is plain that poisons do operate very powerfully on the blood; and if they do so in one case it is reasonable to think that they do so in all. According to the degree of strength of the poison, however, we are sure that the effects will be more or less visible to us; but, though we should not be able to perceive any alteration whatever in the consistence or colour of the vital fluid, we cannot positively say that it has not undergone any change; for the spirit which operates in it is too subtile for our observation. In the beginning of almost all diseases, perhaps, blood drawn from a vein will not be perceptibly different from that of a person in health; and Dr. Fordyce particularly takes notice of this in fevers; but as the disease goes on, an alteration becomes very perceptible, which gives just ground for suspicion, that there had been some alteration from the very first, though invisible to us.

After all our disputes, however, we shall find that the controversy, though ultimately important, begins more about words and trifles than any thing else. Dr. Brown used the word _excitability_, Dr. Girtanner uses _irritability_, and the author of this treatise, the words _vital spirit_ and _electricity_, to express something equally unknown to them all. The only difference is, that Drs. Brown and Girtanner speak of their excitability and irritability as a kind of power essentially inherent in living bodies, acted upon indeed by certain substances, but incapable of deriving any supply from without; the author of this treatise considers it only as a modification in the human body, or an _organization_, if we please to call it so, of that fluid which he believes to be universally diffused, under the names of heat, light and electricity. Hence that portion modified or organized in the human body must be under an entire and absolute dependence upon the immense mass of surrounding fluid, and, by any alteration in the motions of it, must be often very perceptibly affected; nevertheless as this fluid was originally created to preserve and not to destroy human life, there is much less danger from a _natural_ than from an _artificial_ commotion in it. In some visible bodies, such as poisons, the fluid acts in such a manner as to counteract the operation of that part which is organized in the blood or nerves, or both. Hence on the introduction of such into the body the disorder flies like lightning through all parts of it, and in a very short time brings on death. In those vapours properly called _contagions_, the opposite action is less violent, and therefore the disorders they produce are in proportion. Hence such diseases may either be promoted or retarded by the perceptible properties of the atmosphere, which in poisons have little or no effect. There is indeed a remarkable difference in the strength of the poison secreted in the bodies of serpents at certain seasons of the year, or according to their food. M. D’Opsonville observes that the poison of serpents is in general more powerful, the more they live in hot and dry places, where they feed upon insects that are full of saline, volatile and acrimonious particles. But, notwithstanding this difference in the strength of poisons according to the circumstances of time and place, there is not the least reason to suppose that poison of a given strength would not produce the very same effects, let the state of the atmosphere be what it would.

If therefore we certainly know that there are some kinds of aerial vapours which when applied to the human body do exert a power directly opposite to the vital principle, there is no reason to doubt that such vapours may be confined among certain soft substances, such as cotton, wool, &c. and remain there for an unknown length of time, again exerting their malignant powers, when a fresh object comes in their way. Besides, as all kinds of air with which we are acquainted consist of a basis united with the ethereal fluid and volatilised by it, there is reason to suppose that contagions themselves are formed in the same manner. Some kinds of air also are very easily decomposed, in which case the basis attaches itself to some terrestrial substance, the ethereal fluid which volatilised it diffusing itself around in an invisible manner, but generally with a perceptible heat. Fixed air affords a notable example of this; for, by exposing it to lime-water, or even dry lime, alkaline salt, volatile alkali, or common water, a decomposition of the air very readily takes place, and its basis is found to be attached to those substances. What happens to fixed air may also happen to _contagion_. The basis of it may have a tendency to unite itself to cotton, or such like substances, and thus may not only infect them, but concentrate itself to such a degree as to produce a disease much more violent than that of the person who gave the infection; and something of this kind has even been observed with regard to infected cotton. But now another question occurs: As fixed air, by being attached to terrestrial substances, loses its aerial property, why should the basis of contagious effluvia still retain its malignant quality though in a state of decomposition? Here we are again helped out by analogy. Fixed air is known to be capable of resuming its aerial properties occasionally, from causes unknown to us, though we cannot suppose them to be any thing else than the invisible action of the ethereal fluid so often mentioned; which, being guided by laws unknown to us, we cannot possibly comprehend. The fact, however, is certain, that the basis of fixed air does very often quit the substances to which it is attached, and assume an aerial state in great quantity, and with very mischievous effects. Thus the old lavas of volcanoes, if chemically tried will be found at _all_ times to contain great quantities of the basis of fixed air, but it is only at _some_ times that the mofetes which are supposed to be the air itself, break forth.[96] In like manner the strata under ground always contain great quantities of the aerial basis, but the _damps_ in mines, which are certainly known to consist mostly of fixed air, do not always appear; neither do they gradually accumulate, but come suddenly, spreading unexpected destruction among those who unfortunately come in their way. The same may take place with contagion. After remaining some time in a state of decomposition it may have a tendency to become volatile again, or it may lie dormant entirely; and this last will explain what is quoted from Dr. Russel, p. 178, that sometimes commerce may be carried on with infected places without danger.

[96] See p. 128, note.

Thus we see that the dispute, originally begun about a word, involves at last a matter of the utmost importance; for, if it be found unreasonable to believe that any such thing as contagion exists or can exist, it follows of course that it is also unreasonable to take any precautions against it. Mr. McLean even goes a step beyond those who deny the existence of contagion; for we find him also denying that putrid effluvia can produce epidemics; according to which doctrine, it seems, we may not only safely visit places accounted the most dangerous on account of infection, but live in all manner of filth and nastiness with impunity. It is plain that no person can ever prove that it is impossible for contagion or any thing else to _have an existence_. Indeed if nothing had ever induced people to believe that it did exist, it would have been superfluous to say any thing about it. But when we have innumerable testimonies to the contrary; when the opinions of the greatest physicians, as Dr. Lind, Dr. Clarke, Dr. Mead, Dr. Sydenham, Dr. Fordyce, Dr. Russel, &c. agree that not only the plague, but every kind of fever, is infectious; when we know from the analogy of nature that contagion _may_ exist; when we know that there certainly _are_ powers in nature able to produce it; is all this to be thrown aside merely on the strength of a theory, and a theory too which can never be proved? for it is impossible to prove the _non-existence_ of any thing, much less the _impossibility_ of its existence. The lives of mankind are too precious to be sported with on philosophical theories; and prudence will always suggest, that wherever danger may at any time arise, there it is proper to be on our guard.

Dismissing at length the subject of contagion in general, we now enter upon the question, Whether doth it appear from fair investigation of testimony, that the plague has, at any time, been communicated by contagion or not? And here I shall confine myself to what has been adduced by Dr. P. Russel on the subject; for, if we find that the disease has only _once_ been introduced by contagion, it signifies nothing though we were able to prove, which we never can do, that it had been _an hundred_ times bred in some other way. The matter is of too great importance to allow even a _chance_ of its importation by the neglect of the precautions necessary to prevent it.

Our author begins with observing, that though the infectious nature of the plague had been a question much agitated in the schools, “it was less to be expected that physicians who had been engaged in practice among the infected should have persisted in the opinion that the disease was never communicated by contagion.” Such, however, has been the case. In 1720 some French physicians laboured exceedingly to prove that the plague which then raged at Marseilles and throughout Provence arose from corrupt humours bred in the body in consequence of irregularity in the seasons, and bad aliment; that it was spread by the same means, in concurrence with terror, grief, despondence, or other debilitating affections of the mind; but was neither bred nor disseminated contagion. Dr. Russel mentions in a note, seemingly with surprise, that “_so late_ as the year 1778, Dr. Stoll of Vienna should have written expressly against the doctrine of pestilential contagion.” To this professor he thinks it a sufficient answer to quote the following passage from Mr. Howard on Lazarettos, “It must appear very strange, that he should go back to Livy’s Roman History for proofs to establish his point, totally neglecting all the facts concerning the numerous visitations of the plague recorded in modern medical books, or which had happened during his own time. I suppose professional men will lay very little stress upon all that can be said on pestilential diseases, in general, which happened in wars and sieges two thousand years ago, as applied to the plague properly so called, a disease then confounded with various others from which the accuracy of latter observations have sufficiently distinguished it.”

Dr. Russel complains of the French physicians at Marseilles having made unfair representations; particularly that while they produce as irrefragable arguments against contagion their own escape unhurt, amid circumstances of supposed danger, they pass slightly over, or omit all mention of numbers of the medical assistants whom they saw perish in the exercise of their profession. M. Dedier, however, who at first opposed the doctrine of infection, at last renounced his opinions so far as to allow that the disease might be communicated to dogs by injecting pestiferous bile into their veins; and he likewise admitted that it might be communicated from one human creature to another, by drawing in for a considerable time the breath of a diseased person, putting on his shirt, lying in the same bed-clothes, and touching the wounded parts of one’s own body with hands embrued with the sweat or blood of one infected. He affirms, however, that the atmosphere of a person in the plague is no more to be dreaded than that of a venereal patient; and that the touching or dressing of buboes or carbuncles is not attended with any danger. He restricts the infectious quality of the humours to the bile; but the _inoculation_ of a person by the matter of a pestilential ulcer[97] undoubtedly decides this point against him.

[97] See p. 196.

On the subject of contagion Dr. Russel observes, that the vague manner in which the word has been used has given rise to much confusion. Some, taking advantage of the inaccurate mode of expression on this subject used by Dr. Mead, attacked him with sophistical nonsense. The following may serve as a specimen, from a pamphlet entitled “Distinct Notions of the Plague, &c. by the _Explainer_.” This _explainer_ observes, that, according to Dr. Mead, “air and his other causes propagate and spread contagion, not the plague; and therefore either contagion and the plague are the same, or else the plague is not considered; if the first, then his causes propagate the plague; and the plague accompanies the plague; an excellent defence! But, if the plague is out of the play, then contagion accompanies nothing.”--From writers like this we certainly can expect nothing.

The opinion of Dr. Cullen concerning contagion has been already noticed, p. 179; but though he supposes it to be a matter floating in the atmosphere, he observes that contagions are never “found to act but when they are near to the sources from whence they arise; that is, either near to the bodies of men, from which they immediately issue, or near to some substances which, as having been near to the bodies of men, are embued with their effluvia, and in which substances these effluvia are sometimes retained in an active state for a very long time. The substances thus embued with an active matter may be called _fomites_; and it appears to me probable, that contagions as they arise from fomites, are more powerful than as they arise immediately from the human body.” This opinion concerning the great power of contagion imbibed by certain substances is conformable to what was above laid down by reasoning _a priori_ on the nature of contagion.[98] It is doubted by Dr. Russel, but Dr. Lind adopts it, and Van Swieten gives his opinion to the same purpose. “I am convinced, that the body of the diseased, kept exactly neat and clean, is not so liable to impress the taint, as his late wearing apparel, dirty linen, and uncleanliness of any sort about him long retained in that impure state. I say, these last contain a more concentrated and contagious poison than the newly emitted effluvia or excretions of the sick.”

[98] See p. 226.

With regard to the original cause, our author observes, “that the plague is bred or produced originally from vitiated human effluvia, is a matter which has by no means been established on proper authority.” Setting aside therefore inquiries of this kind, he thinks it sufficient to inquire whether the infection be not communicated from a sick to a sound person by immediate contact; whether it be not also communicated at some distance through the medium of the air; and whether substances of various kinds do not imbibe the infectious effluvia, and retain them for a considerable time. So far as these points admit of proof from the experience of times past, the question concerning pestilential contagion will admit of a solution, independent of all theoretic reasoning whatever.

2. On the subject of contagion people have been embarrassed by confounding the true plague with other malignant diseases. This has been done, not only by the ancients, but by some moderns; and our author quotes Dr. Pye, saying “that any epidemic sickness, which rages with more than ordinary violence, and which occasions extraordinary mortality amongst mankind, may be, and is, properly termed a pestilence, or the plague.” By not attending to the proper distinctions, in these cases, circumstances belonging to what are commonly termed malignant or pestilential fevers will often come to be very improperly applied to the true plague.

3. “It may be remarked, that those who contend in favour of contagion, from zeal for accumulating proofs, have collected a number of facts from historical records of very unequal authority, and often with little critical skill in discrimination. Of this error their antagonists availing themselves, have selected from the mass the instances most liable to doubt or objection, and have endeavoured, by their manner of arranging them, to place the whole in a ridiculous light; while more important instances are either evasively past over, misstated in the representation, or invalidated by general declamation on the little credit due to historians in matters of physic, or the prejudices prevalent in ancient times of ignorance, and on contradictions to be found in the arguments of those who support the system of contagion.”

To this the Doctor adds the great quantity of hypothetical reasoning which has been introduced into the controversy, and above all the unfair dealing of the parties in carrying on the dispute, which has reduced the matter from “a calm inquiry in pursuit of truth, to a wrangling contest for victory.” Lastly he insists, that, had it not been for the misrepresentations and sinister dealings of those who have written against contagion, “the question seems to have been properly resolved in the affirmative;” and he complains greatly of the conduct of the Montpelier physicians in this respect, insomuch that “their misstating of circumstances, and the partiality so evidently discoverable in their narrative of cases, will serve more effectually to remove doubts on the subject, than any arguments that could be used against their hypothesis.”