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.”
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.
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.
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.”