CONCLUSION, Addressed to the learned Societies, in America, Europe and Asia.

THE preceding history of Epidemic diseases was undertaken solely from a desire of investigating the truth, respecting the ori|gin and phenomena of these terrible scourges of the human race. When the pestilence appeared in the United States in 1791 and 93, I had not a suspicion that the popular doctrins respecting con|tagion, are not well founded. The frequent recurrence of the disease in subsequent years, in opposition to all the best efforts of health officers, in executing rigid laws of quarantine, had, in 1795, shaken my confidence in those doctrins. My investigations in that and the next year, convinced me that the pestilential fever which has visited so many parts of America, is generated in the country; but still I had not the least suspicion of a connection be|tween epidemic diseases. The investigations of the year past, have resulted in unfolding p••nciples and facts to me altogether new and surprising; they cannot therefore be ascribed to a wish to establish a preconceived theory.

These results not only confirm my suspicions that the pestilence of America is of domestic origin, but they overthrow the pre|conceived system of the origin of pestilence, in temperate lati|tudes, from fomes conveyed to those climates from southern re|gions; and demonstrate that it originates occasionally in all lat|itudes from the 25th to the 65th.

It is demonstrated that pestilence, in temperate latitudes, is never an isolated epidemic, but the crisis of a series of epidemics; and we are furnished with the means of determining unequivo|cally the character of pestilence in every case, on the following simple principles.

"If, on the appearance of pestilence in a particular place, all Page  276 other diseases cease, or take some of its predominant symptoms, that pestilence is generated in that place, and dependent on the state of the elements."

It is impossible, on physical laws, that this criterion should ever fail.

Another criterion, almost infallible, is the prevalence of cer|tain diseases before and after the pestilence. If pestilence is im|mediately preceded by measles, affections of the throat, inflam|matory or typhus fevers with anomalous symptoms, and especially by catarrh, that pestilence is an epidemic, produced on the spot, and only the autumnal form of disease—the other diseases, prece|ding and following, being the vernal and hybernal forms, produ|ced by the same general principle.

Of the pestilences which afflict mankind, in all climates, an immense proportion, probably nineteen twentieths, belong to this species—they are epidemics, beginning and ending at the com|mand of the elements, under the co-operating influence of sea|sons and local causes.

These epidemic pestilences are more or less infectious, accord|ing to their violence, or the places where they exist. In close rooms and narrow alleys they are dangerous; hence their mor|tality in fleets, camps, jails, and particular parts of cities. But the infection of such diseases extends to the distance of a few feet only, and is capable of dissipation in a free air, so as to reduce the danger of attending the sick almost to nothing. The same is true of diseases of mere infection, not epidemic.

Diseases, dependent on infection only, are sometimes introdu|ced into cities and hospitals, and occasion considerable mortality. But they are propagated by contact or near approach only, and do not affect the character of other diseases current in the place.

The consequence resulting from these principles is, that epi|demic pestilence is not under human control—but diseases propa|gated by mere infection may be arrested and subdued.

The only means of avoiding or mitigating epidemic pestilence are first to withdraw the aid of local causes; secondly to fit the body, by modes of living, to resist its causes—and thirdly, on failure of these, to remove from the place where its exists.

Page  277The infection of all diseases, even those of specific contagion, as small-pox and measles, may be avoided by keeping at a dis|tance from the diseased. The infection of diseases not specifi|cally contagious, as plague, yellow-fever, dysentery and jail fe|ver, may be nearly destroyed by free air, and cleanliness.

With respect to the primary causes of epidemic diseases, we are in the dark; but we are certain, from all history and modern observations, that the causes of epidemic diseases among the hu|man race, affect every species of animal and vegetable life.

The opinions which I have suggested concerning the general cause, seem to have a foundation in the coincidence of epidemic diseases with numerous electrical phenomena. At the same time, the reader will consider these opinions rather as conjectural, than positive. No certain conclusions can be drawn from an in|terrupted and imperfect series of facts. More materials are ne|cessary to enable us to erect a theory of epidemics which shall de|serve full confidence.

The common doctrin of contagion is utterly insufficient and unphilosophical; for if admitted, it never leads us nearer to the cause. If we trace the yellow fever to the West-Indies, and the plague to Egypt or Constantinople, we are not an inch nearer to the source; for these diseases are not always to be found in those countries; and the people there are as much puz|zled to find the source of them, as the people of Great Britain or America.

If we trace these diseases to the coast of Africa, or to Siam, we are as distant as ever from the source; for many times, the diseases are not to be found in those countries, and seldom in|deed are they ever found within the tropics, except among for|eigners.

Indeed nothing is more common than for the yellow fever to be imported into the West-Indies in vessels from the United States. When vessels from northern latitudes have long passages, it of|ten happens that seamen are seized with the disease, before they arrive at the islands; and the West-Indians may often allege the disease to be imported in such vessels, when it does not exist in the United States.

Page  278In short, the doctrin of deriving all pestilential diseases from contagion or infection, were it not for the immense mischief it does to society, would not deserve a serious refutation. Infec|tion is a subordinate cause of the propagating of malignant distem|pers; but is itself an effect of some more general cause, whose force is a hundred fold more powerful and formidable than that of infection. I have, in condescension to popular opinion, stated the evidence of the domestic origin of the bilious plague, as it stands on the arrival or non-arrival of vessels, and other facts of that kind. But I really consider all this evidence as trifling, when compared with the phenomena of the disease itself and its precursors and attendants. The uniform appearance of other epidemics, as introductory to pestilence, and manifesting an essential change in the atmosphere, with the numerous ac|companiments of the plague and yellow fever, amounts to evi|dence of domestic origin, which leaves no room for cavil or controversy.

For the purpose of collecting facts, the only safe foundation of principles, and comparing the phenomena of diseases and the elements, which occur nearly at the same time, in different coun|tries, I sincerely wish and request that all medical and philo|sophical societies would undertake to register facts and recipro|cally to communicate them, by means of a general correspond|ence. The facts to be registered might be comprized under the following heads.

The time of the appearance and disappearance of any epi|demic disease, with its general history.

The places where it first occurs to be described, in regard to land and water, height of the land, construction of the city or streets, position as to points of compass, woods, morasses, &c. The classes of people most generally affected.

The general state of the seasons, as to heat, and cold, drouth and moisture.

The time of earthquakes, meteors, lumen boreale, and all singular celestial appearances—with unusual tempests, especially when accompanied with hail—all compared with the lunar phe|nomena.

Page  279The appearance of unusual insects of all kinds, and any cir|cumstance attending them.

Diseases among cattle, sheep and other animals.

Sickness and death of fish of all kinds.

Volcanic eruptions, with the phenomena preceding, attending and following them.

For the purpose of ascertaining the lunar influence on the hu|man body, or any diurnal influence, it would be desirable that medical gentlemen should note the days and the hours of the day when persons are seized with particular diseases—especially epidemics—the hours of exacerbation and of paroxisms in fever— the hours which are most fatal to the diseased—and the time when convalescents are most apt to relapse.—These facts should be compared with the position of the moon, in her orbit, and es|pecially in regard to her perigee and apogee; conjunction and op|position; as also with the tides in the main ocean.*

Should the principles unfolded in the preceding work prove to be well founded, they will lead to many important practical in|ferences.

I. If pestilential fevers never appear in the temperate latitudes, without certain precursors, men will, with careful observations, be enabled to foresee the danger and prepare for it; or to use un|common diligence in removing the subordinate local causes.

II. If in certain years pestilential fevers are more predominant, than in others; and the condition of the elements fitted to pro|duce them, is universal over sea and land, the fact is of no small moment in maritime affairs. Double precautions will be taken in fleets, and in merchantmen bound on long voyages.

III. If pestilence is progressive and first manifested in certain malignant fevers, the fact may be of great utility to large cities. The approach may be perceived in time to save the inhabitants by flight, if not by other precautions.

IV. If no plague or yellow fever ever appeared in temperate climates, unless announced by other distempers, the magistracy may be enabled to distinguish when there is danger, and when Page  280 not; and may avoid innumerable vexations to commerce, arising from the rigid execution of health laws, when there is not the least occasion.

V. But a most important use to be made of the facts here col|lected, will be, to guard public health from the ill effects of bad provisions. If, in pestilential periods, salt is less efficacious in preserving flesh, and by means of a greater fermentation of the juices, fish and flesh are more readily dissolved by a putre|factive process, more caution will be found necessary in packing and repacking them, and more care to avoid using it in a bad state.

If the effluvia of dissolving flesh and vegetables are more poi|sonous and prejudicial to health at some times, than at others, it is of importance that, on every such occasion, early notice should be given of the danger.

If animals, which constitute a part of the food of men, are subject to epidemic distempers, they cannot be eaten with safety, while affected by disease. When fish or fowls are sickly and many of them die, or become lean, the fact should be ascertained by the faculty or a board of health, and public notice should be given, that people might avoid using them as food. In some instances, fish are so sickly as to excite nausea; in which case the use of them should be forbidden.

I will close this treatise with the following reflections.

In the construction of the universe, we observe every part of the system to be governed by uniform laws, adapted, with infi|nite skill, to preserve harmony and order. Limited as our un|derstandings are, we can discover many of these laws, which are calculated to impress on our minds the most sublime ideas of the universal intelligence and wisdom of their Great Author.

The existence of natural and moral evils has led sceptics to question the perfections of the author of nature. But doubts on this subject argue want of knowlege or want of candor. It is extremely evident that all the necessary evils of the system are calculated to produce good. The operation of that universal principle of light, heat and fire, which pervades our system, and which is incessantly compounding and decompounding the other more sluggish materials of the earth and atmosphere, are essen|tial Page  281 to the vicissitudes of the seasons, rain, snow, hail and dew, which are necessary to preserve the principles of animal and vegetable life. Storms, hurricanes, earthquakes and volcanic eruptions, however inconvenient to men at particular times and places, are among the means of giving to the principles of life, more equal distribution, and of renewing their energies.

Epidemic diseases are some of the necessary effects of the gen|eral laws that govern the universe. But they have also a final cause of immense value to the human race. They are destined and calculated to answer most important moral and religious purposes.

Men, with their present nature, under a constant course of prosperity, would degenerate into devils or brutes. Uninter|rupted ease and quiet contract the heart and steel it against emo|tions of sensibility—the man rushes into vices and crimes, or sinks into sloth. So often have I seen the hearts of men depraved and their moral character debased, by sudden prosperity, that I am persuaded the world, without frequent inflictions of pain and distress, would not be habitable. The natural evils that surround us, intermingled with innumerable blessings, preserve the mind in perpetual vigor, in seeking the means of protection; they lay the foundation for the exercise of the finest feelings of the human heart, compassion and benevolence, which are the sources of social virtue; they humble the pride and arrogance of man, by cre|ating in his mind a perpetual dependance on divine power; in short, they create and preserve that sense of obligation and ac|countability to God which is the germ of piety, and moral ex|cellence.