From these and other causes there must necessarily arise a predisposition to hepatic diseases; and this predisposition cannot be removed until the blood has assumed the state of fluidity proper to the climate in which they are, and the body has acquiesced in the change. They are then said to be seasoned to the climate; and it is seldom that this seasoning takes place without a disease; indeed so seldom, that the first illness which happens to seize them after their arrival is called the seasoning. Dr. Trotter indeed gives a very different account of this seasoning. He considers those who come from a cold to a warm climate as having a redundancy both of excitement and excitability, and says that “to wear out this accumulated excitability by slow and gentle gradations is the grand explanation of the word seasoning: it is the secret which constitutes the only difference between the inhabitants of England and Jamaica. The yellow fever of the West Indies therefore, as it appears in the body of a raw European, is a disease of the utmost excitement, in a constitution of accumulated excitability; where a tense fibre and dense blood permit it to be carried to the highest pitch of inflammatory tendency; which, from the nature of the animal economy, speedily exhausts the powers of life, even in a day or two, inducing putrefaction and death.”
Explanations of this kind may edify those who understand them; but, though we should declaim ever so much about excitement and excitability, it is plain, that, in every one who comes from a cold country to a warm one, the liver is affected in a manner that the rest of the body is not. In some constitutions, or from exciting causes in any constitution, this affection of the liver may be augmented, and no doubt at last produce a bilious fever, which may be varied in a number of ways, according to the nature or the energy of these causes. The pure bilious fever, being of itself properly a local affection, may not be contagious; and we find it generally agreed among physicians that the common yellow fever of the West Indies is not infectious. Nevertheless, it seems by no means improbable that from certain circumstances contagion may be joined with it, and it may then spread and infect, even as the most deadly plague. Dr. Crawford relates, that, in the year 1770, a new kind of fever broke out in the Middlesex Indiaman, of which many died. It is not said that the disease was contagious; but, on opening the bodies of some who died, the liver was found enlarged, and of a more florid colour than it ought to be. It cannot be deemed impossible that contagion, even that of the true plague, might be mixed with this fever, which (as the affection of the liver was probably the original disease, might have been accounted little other than symptomatic) would then have assumed very malignant symptoms.
We might now say that we have got to the end of our subject. Having so amply discussed the question concerning contagion, and stated the principal part of the evidence against it, it seems proper to conclude the section with a short history of the disease in the malignant form it has assumed in the United States since the year 1792. Still, however, it is necessary to say something further of one or two of the causes which have been commonly assigned as necessarily inducing this disease. These are, 1. Extreme heat, and, 2. Marsh effluvia. The effect of the former has already been partly considered as a predisponent cause of yellow fever: but it doth not appear that merely from this cause the disease has ever been produced. It hath indeed been observed by very intelligent physicians, that in Virginia the remitting fever has often been brought on by mere exposure to the sun. Dr. Oliver of Salem hath obligingly informed me, that he has “in more than one instance been seized with that disease after riding in the sun;” and that an eminent practitioner in Virginia had informed him that he had also more than once suffered in the same way. Drs. Taylor and Hansforth observe, that, when the remitting fever proves mortal, it is generally attended by sickness and perpetual vomiting; which is the termination of the yellow fever. The above evidence is decisive with regard to heat being able to produce a remittent, but cannot exactly apply to the yellow fever, which has no remissions. Two sailors indeed, lately brought from a coasting vessel to the Salem hospital, were attacked with violent symptoms of yellow fever without having been, as is said, exposed to any infection. But evidence of this kind cannot be supposed to be incontrovertible. We have already seen the difficulty of ascertaining facts; and if it is difficult to prove that contagion has been received, it must be still more so to prove that it has not. The persons in question had both worked during a very hot day in a vessel’s hold, they afterwards sat exposed in the damp air of the evening on the deck until 10 o’clock at night, and then slept in the vessel’s cabin with the windows open. One of them was seized in the night with a most violent pain, and the other on the morning succeeding. It is said that about 11 months since this vessel was at New York, and that a person on board had the yellow fever; it is also alleged that the vessel was not purified, and that the beds remained on board. It has therefore been by some conjectured that the disease might have been derived from this source.
Dr. Ramsay, in a letter to Dr. Currie of Philadelphia, censures Dr. Lining for saying that the yellow fever was imported into South Carolina. “The greater yellowness of the skin (says he) appears to be the only circumstance in which it differs from the bilious remittent fevers of hot climates, or very hot seasons of any climate.” Our author also censures Dr. Lind of Haslar,[185] who, he says, has been misled by the misrepresentations of Dr. Warren and others. He also gives into the opinion that contagion acts only by contact, or at a very little distance; but this subject we cannot enter farther into at present. If we can believe Dr. Moseley, the sure criterion by which the yellow fever may be distinguished from any other is, that the former hath no remissions.[186] If solitary cases of it appear in Carolina and the southern States every year, this will not prove that the disease was generated in the country, any more than that the plague was generated in London, because it appeared there for many years successively.
But, if the heat of the sun cannot produce the true yellow fever, it can kill suddenly without any fever whatever. This is said by Dr. Moseley to be less frequent in the West India islands than on the eastern and western continents. He says that he has felt as great inconvenience from the sun’s heat at Venice, Naples, Rome, Montpelier, and in Virginia, as in the West Indies;[187] but he concludes that the transitions from heat to cold are more pernicious to the human body than any continued heat, however violent.
With regard to the effluvia of marshes, it is not denied that they produce fevers, but those fevers are of the intermittent or remittent kind. Dr. Smith indeed, in the first volume of the Medical Repository, labours to prove that the plague described by Thucydides was not essentially different from the fevers which sometimes prevail in North America, and that it had its origin from marsh effluvia and the ravages of war. That this distemper was not the plague described by Russel we may gather from a single circumstance: for Russel tells us that sneezing never occurred in the plague described by him,[188] while Thucydides says that it was one of the common symptoms of his. Neither does the description of it (Appendix No. 1) at all agree with any of the accounts of the yellow fever we have. The climate of Attica no doubt was variable, and may in this respect resemble that of North America; but so is the climate of China, yet no such diseases are there produced. The Doctor concludes that the distemper originated from local causes; but the difficulty we find in proving such origin of diseases in our own days, and in the country where we reside, must certainly make us look upon the proofs which can be brought for the local origin of a disease which happened two thousand years ago, and in a distant country, as very equivocal. The following extract from the Paris Medical Memoirs may be adduced as a proof of the intrinsic power of marsh mud to produce fevers. It is contained in a paper written by Dr. Perkins of Boston. “A farmer was in the practice of spreading, upon about thirty acres of land, some new marsh mud, from October to April annually, to increase the fertility of the soil. In the summer of the third year, those inhabitants who lived to the northward and eastward of the place were attacked with a very malignant fever, which generally proved mortal. What is a proof that the marsh mud was the cause of the disease is, its extent, which was not more than a mile and an half from the farmer’s house, in the direction of the southerly and westerly winds. Perhaps had this marsh mud been washed by plentiful rains, the danger would have been less. Something like it happened to the inhabitants of the marshes in East Sudbury, (les marais situes a l’est dans le Sudberg) where the passage for the waters was too deep, and too confined. In regular seasons they were attacked with simple intermittent fevers; but, after wet seasons, there prevailed among them malignant fevers, and very obstinate remittents. Since the marshes have been drained, the inhabitants are no longer subject to fevers, and are as healthy as those of others places. We know that there are local epidemics, which are produced by a low, wet and rich soil; such are, probably, those which prevail in the lower part of New York, which, according to the informations obtained by Mr. Perkins, is more unhealthy towards the end of the summer than the other part of the city, and whose inhabitants are subject to diseases of a putrid caractere.
“It appears, from several observations, that the most mortal epidemic fevers are not commonly produced by causes operating immediately; the cause often existing several months before the disease even appears.”
The other arguments used by Dr. Smith in his letters to Dr. Buel proceed upon the state of the city, the mode of living, &c. and the condition of most of the emigrants, their bad accommodations, and especially their abuse of spiritous liquors. The neglect of bathing is also much complained of, and a comparison made with the conduct of the French in this and other respects, greatly to the advantage of the latter.
Drs. Taylor and Hansforth consider the disease which took place in Norfolk in Virginia as only an higher degree of the common remittent fever which usually prevails, and ascribe it to the long-continued heat, putrescence, &c. Some French ships were said to have brought the disease, but these arrived “so long before the disease appeared, that (the Doctors think) it would be absurd to suppose even a possibility of its being derived from them.” Mr. Webster adds, in a note, that the French corvettes, three of which squadron were taken by the Thetis, capt. Cochran, “anchored in Hampton Roads, May 18th. The fever did not appear in Norfolk till August. Captain Cochran’s crew, however, took the fever from the French prisoners, and twelve of them died before the Thetis reached Halifax.” This is certainly a suspicious circumstance.
Dr. Ramsay, in his letter to Dr. Mitchill concerning the same distemper, observes that it was confined almost entirely to foreigners, of whom he gives a very unfavourable account. The situation of the town, putrescence, &c. are likewise brought in for a share, as well as the season, which had been uncommonly warm.