These facts are of the utmost importance in determining the nature of contagious diseases. In conjunction with others, they show that such diseases originate in the blood, and from thence are communicated to the rest of the body. They show also, that the contagion is in all cases truly specific, and immutable. Thus the contagion of the small pox, whether existing in the matter of a pustule, in the smoke of burning clothes or paper, or in the effluvia of blood, is invariably the same, and never produces any other disease. It is the same whether applied to the human body, or to that of a brute animal; of which we have a remarkable instance in the Medical Repository, vol. i, p. 258. “A peasant of the county of Essex, in England, seeing a great many children carried off by the natural small pox, was desirous of inoculating his two boys; one nine, and the other twelve years old. Not being able to employ a surgeon, he collected the scabs of a child then sick of the disease, powdered them, and sprinkled the powder upon slices of bread and butter. The two sons ate them, and gave a bit to the house-dog. They had a mild small pox, and got well without any remarkable accident. The dog remained sick for two or three days, drank a great deal, and refused to eat: on the fourth he had a very decided variolous eruption: on the ninth the pustules were full ripe, and dried up and fell off like those of the two children. An English author says he has seen the same epidemic in a flock of sheep, the greater part of which were infected, and communicated it to two cows, one of which died. The symptoms that manifested themselves in these animals in the course of the disease were in every respect the same as in the human species.”
This instance, partly quoted in the former part of this treatise, likewise is a strong proof of the contagion of small pox being first communicated to the blood; for, by swallowing it along with the aliment, it would, in the common course of digestion, be absorbed by the lacteals, and enter the blood with the chyle. The experiments with dogs made by M. Deidier, of which an account is given p. [268], show that the contagion of the plague is equally specific with that of the small pox; and we see that it acted in all cases in which it was tried by being mixed with the blood. Being thus first mixed with the blood, it is plain that the contagion must have passed from this fluid to all the other parts of the body; and, if diseased blood is capable of communicating its disease to all the sound parts of the body in which it circulates, we must own that this strongly corroborates Dr. Waterhouse’s suspicion, “that the blood is capable of producing the infection before the disease is so far advanced as to be apparent on the surface.” If the disease originates in the blood, the latter should indeed seem more capable of communicating it at first than afterwards; because we must suppose that the diseased parts would be thrown off to the surface, and so pass off altogether. On this subject Dr. Waterhouse also quotes the opinion of Dr. Holyoke of Salem, “who, for his learning, professional abilities and integrity, is justly esteemed one of the first physicians in this country, and whose extensive practice has afforded him ample experience in the small pox.” He writes to Dr. Waterhouse, “that, although he has reason to believe that an infected person seldom gives the disease till after the eruption is considerably advanced, yet there are facts which make it probable that it is sometimes communicated earlier.”
In the same letter Dr. Waterhouse gives other instances of the inconceivable subtilty of variolous contagion, no less remarkable than those already mentioned. One is of Dr. Brattle, who, having visited patients infected with the small pox, “used the common precaution of covering his clothes with a loose gown, &c. but neglected his wig. In consequence of this small neglect, after riding six miles on horseback, he gave the disease to a person in a room through which he passed, where he did not stay to sit down.” Another is, if possible, still more remarkable: “David Anthony, esq. one of the overseers of the small pox in Rhode Island, after going into the hospital, and using the common precautions, neglected to smoke his wig. In his way home, two miles from the hospital, he called at the house of his daughter. He did not dismount, but sat on his horse, and talked to her through an open window; and, at the common period (by which we usually understand about fourteen days) she took the disease and died. Many such instances, adds the Doctor, could I relate, where wigs have given the infection, after being exposed to the open air during the passage of several miles.”
From all this it appears how difficult a task they undertake who contend for the domestic origin of the yellow fever, without contagion. In all cases they must have recourse to something visible and obvious to the senses. Thus putrid beef, putrid fish, ponds of water, marshes, &c. are all easily seen, and we are able to prove their absence as well as their presence. But we certainly know that the yellow fever has arisen where none of those supposed causes have existed, as in the Busbridge Indiaman; and, on the other hand, all the supposed causes have existed without the production of any fever. Of this last Dr. Chisholm, in the conclusion of his defence against Dr. Smith, gives the following remarkable instance:[169] “During a considerable part of the years 1776 and 1778 my duty led me very much to reside in New York; and during my residence, particularly in the summer and autumn of 1778, which were remarkably hot, and insufferably so in the lower streets of New York, no disease of a very alarming nature, and none which assumed the form of an epidemic, appeared among the troops or inhabitants. The smell from all the ships, and from those in particular delineated by Dr. Seaman (who has written a treatise on the subject) was in the highest degree offensive. The police at that time was by no means strict: putrid substances of every description were accumulated in the ships, and in many parts of the city unconnected with wharves, and yet no disease was the consequence.”
Some particulars above related may perhaps appear, to those who deny the existence of contagion, in rather a ludicrous point of view. It is indeed too common for people to laugh at what they cannot answer; but if we consider the instantaneous and inexplicable action of the poison of serpents, and in how little time they produce a mortal disorder, or even death itself; when we consider that contagion is only a volatile poison, and that it for the most part takes up an incomparably longer time to bring on death than the bites of some venomous animals; we cannot be surprised that a quantity of this volatile matter inconceivably less than that of animal poison should be capable of bringing on the disorder; for the length of time may be supposed to make up for the deficiency of quantity. Yet, if we consider the extreme activity of some animal poisons, the wonder at the small quantity of contagion necessary to produce a deleterious effect will in a great measure cease. In the former part of this treatise it has been observed, from Dr. Mead, that the whole quantity of poison emitted by a viper, when it bites, does not exceed the bulk of a good drop. An ordinary drop from a vial weighs half a grain, so that we cannot suppose a large drop to be more than a whole grain. But there are instances in which effects equally deleterious are occasioned by the bites of animals the whole bulk of which is scarcely equivalent to that of the poison of the viper. In the northern climates of the Old World, spiders do not grow to any remarkable bulk, yet the bite of the poisonous spider of Russia is as mortal as that of the rattlesnake.[170] The effect of the furia infernalis of Linnæus is still more to our purpose. It is an insect found in the forests of Kemi in Lapland, and likewise in Sweden and Russia; and, if we can give credit to Mr. Pennant, in some of the Western Islands of Scotland. This insect falls down out of the air, and, if it happens to light upon any uncovered part of the human body, it almost instantly penetrates down to the bone, occasioning the most excruciating pain, and death in a quarter of an hour.[171] Now, should we suppose the whole body of this insect to be poison, as it is probable that it is not, it is so minute, that though the whole were volatilized into contagion, it might be well supposed to adhere to a wig, or even a more diminutive part of the clothing; and, considering the virulent effects of even this small quantity of contagion when concentrated, it would easily follow by fair calculation, that a very minute proportion of even this small quantity might bring on a dangerous disease.
Lastly, it may be urged on the side of contagion that, when a vessel arrives from a sickly country, it is no proof that she has not brought a disease with her, that the people aboard are in health. There is abundance of evidence that very dangerous maladies may be communicated by those who do not labour under the same. The prisoners at the Oxford assizes were not sick at the time they communicated a dreadful distemper to those around them. Dr. Brattle and Mr. Anthony were in perfect health when they communicated the contagion of the small pox, yet the effect was not less fatal. In short, contagion being a power certainly known to exist, though invisible and imperceptible, it is impossible ever to prove that it is absent; neither after the contagion of any disease has once got into a country can we be assured that it may not revive. The experience, we may say, of the whole world testifies that it does adhere particularly to clothing. Dr. Lind thinks it may adhere to the timbers of ships; and there is the greatest reason to believe that it may also adhere to the walls of apartments in houses. The appearance of fever therefore without any new importation cannot prove that it has not arisen from contagion. But it is now time to state the evidence on the opposite side.
In Webster’s Collection we find the domestic origin of yellow fever supported by Drs. Valentine Seaman, and E. H. Smith of New York; and by Drs. Taylor and Hansford, and Dr. Ramsay of Norfolk. Dr. W. Buel of Sheffield has also given an account of a fever, but so unlike that of which we treat, that what is said of the one cannot be applicable to the other.
The arguments used by Dr. Seaman are, 1. Several persons were infected, who had taken the utmost care to avoid all communication with the sick, who had not been for several weeks out of their houses, or within eighty feet of an infected person. 2. The nurses and attendants in some places were infected, but in others generally escaped. Neither did the disease spread into the country, as was reported; the Doctor having inquired into these reports, and found them groundless. 3. Dr. Lining says in his letter to Dr. Whytt,[172] “If any person from the country received it in town, and sickened on his return home, the infection spread no further, not even to one in the same house.”[173]
Several other arguments of the same negative kind are adduced, which, being not essentially different from those already quoted, it is needless to detail. The following are rather of a different nature: 4. Some contagions are propagated by contact only, others at a distance; but at any rate we may suppose that contact will propagate contagion more readily and more powerfully than any other mode that can be imagined. Yet multitudes of dissections have been made, and those who made them are still alive. 5. “Specific and acknowledged contagions all seem to arise from themselves only: hence it would be almost as hard for me to believe that the siphylis, small pox, or measles, could be produced from any other cause than their own proper virus, obtained from persons affected with the like disease, as it would be for me to conceive of the formation of a plant without its having received its seed, or radical, from one of the same nature.[174] Contagions seem to fix in the soil of our bodies, and there seed, as naturally and regularly as vegetables do on the earth. But the yellow fever has been produced from other causes than contagion.[175] Does it not then admit of a doubt, whether it can possess a power of propagating itself?” 7. Contagions respect no persons, but all of every clime and colour are equally attacked with them; but the yellow fever is known to attack some much more readily than others. 8. Contagious diseases generally have a determined time of invasion after an exposure to their cause: but the advocates for contagion in the yellow fever cannot be confined in this manner. “Their doctrine requires that it (the contagion of yellow fever) be permitted to act at any time between that of the exposure and the sixteenth day; otherwise it would not embrace cases enough to give it a currency.”[176] 9. “Contagions act more or less at all places and seasons, simply of themselves, without the aid of any particular circumstance of air or climate; but the supporters of the yellow fever being contagious are obliged, by the force of the foregoing observations, to acknowledge their imaginary fondling to be but a half-formed monster, and perfectly inactive without being assisted by the concurrence of a predisposing constitution of the air. (Rush on yellow fever.) This fever exists only in warm weather: hence its cause in this city (New York) was perfectly extinguished by the frosty nights in the 10th month. It is confined mostly to low situations in thick-settled places; otherwise our almshouse and the surrounding country would have sadly experienced its deleterious effects.”
This argument merits a particular consideration, as involving a question of very great importance, namely, concerning the constitution of the atmosphere, which we have had occasion formerly to speak of, and which is by some thought to be sufficient of itself to produce epidemics, without the intervention of any other cause. This constitution of the atmosphere is, it is true, something unknown; and, when people appeal to it, it is only in other words owning their ignorance; but the necessity of recurring to some cause imperceptible by our senses has in all ages been obvious. So much indeed has been said in this treatise on the causes of plague (which may apply also to yellow fever)[177] that more would be superfluous, even if our limits would admit of it. The dilemma (and it is equally insoluble let us say what we will) stands thus: If the yellow fever is produced by the effluvia of marshes, by putrid streams, or by any thing else, how comes it to pass that it has been so frequent in the United States since the year 1792 in comparison of what it was for 30 years before? Have the American cities all at once become sinks of filth and nastiness? Have the seasons been changed, or have the inhabitants given themselves up at once to swinish intemperance and gluttony, devouring, like savages, their meat half-rotten, half-roasted or half-boiled? From some declamatory publications indeed one might be apt to think that the authors certainly meant to bring such accusations against them. But it undoubtedly will be found an hard matter to prove that the general cleanliness of the country is inferior to what it was, or that the people are less virtuous than they were before. Besides, has not the vigilance of the magistrate, ever since 1793, been exerted to the utmost to procure a removal of those nuisances from which the disease might be supposed to arise? Yet their efforts have not availed; for it is confessed that the attack in 1798 was the most severe ever experienced. If cold could have exterminated the disease, certainly the three last winters have been abundantly sufficient to do so; yet it is certain that cases of the fever did appear in the end of December last, when the cold must certainly have been deemed sufficiently intense to put a stop to putrefaction of every kind. No wonder then that people, unable to see the causes of these things, should have recourse to something invisible, which they called the constitution of the atmosphere. On this subject Dr. Haygarth of Chester makes the following objections to the commonly received opinions concerning epidemic constitutions of the atmosphere:[178]