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The first of these topics is one of exceeding difficulty, and upon which scarcely any certain knowledge has yet been obtained. The only opinion which can be stated with any assurance, is, that there must be some peculiar virus of the disease, whatsoever its nature, which, like the virus of measles and scarlatina, is capable of spreading or communication under certain laws; and probably of remaining in the body a certain time, before evolving the more active symptoms of the malady. It seems hardly possible to avoid such conclusion, looking at the whole course and history of these epidemics. It is the only view under which we can explain their identity at different periods of time, and in distant places during the course of the same epidemic. Sir G. Baker's narrative of the influenza of 1762, or Huxham's still earlier reports of the epidemics of 1733 and 1743, might be taken throughout as a description of those of 1833 and 1837. That which occurred in 1675, and is recorded by Sydenham, equally corresponds with our recent experience. The history of the disorder at Copenhagen and Berlin will serve with little variation for its course and character at Lisbon and Malta. This uniformity can scarcely be explained but by identity of physical cause; and for such identity it is difficult to look to other source than some material virus; curring, we know not why, at different periods ; — and capable, through certain unknown laws, of being widely diffused, without change of character or loss of power.

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It is true that some authors, and in concurrence with common opinion, have attributed these epidemics solely to atmospheric changes, and the influence of extraordinary seasons upon the human body. And it must be admitted on behalf of this opinion, that certain of the seasons during which they have prevailed, have been remarkable and anomalous; and further, that in common catarrh, arising from

obvious causes of atmospheric change, many of the symptoms resemble the lighter and more transient forms of the disorder in question. But there is something manifestly beyond this relation, and independent of it. A disease which has appeared and spread at different seasons, in the middle of summer as well as in the depth of winter ; which has been found traversing whole continents, continuing this course through many successive months, and often assuming even a definite direction of progress;-which affects contiguous places in different degrees, and at different times;—which frequently continues in the same place for several weeks or months, under every appreciable variety of atmospheric state; — and which often affects, almost simultaneously, large masses of people living on the same spot, while others in adjoining localities are exempt; such disease cannot be considered as due to any of the known qualities or variations of the atmosphere, to which the term weather is applied. changes in the air are at all concerned, they can scarcely be conceived to act in other way than as engendering, or giving greater intensity, or readier diffusion, to some material virus, the active cause of the disorder. Even this is difficult to suppose under the diversity of conditions just noticed; while beyond this we cannot go without contradicting some of the most assured facts which enter into the history of these diseases.

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The argument and inference here may best be established be taking a single epidemic; tracing, as closely as the report of facts will allow, the manner of its spread both as to time and localities; and removing all the conditions which we can thus prove not to be concerned. The influenza which spread over every part of Great Britain and Ireland during the spring of 1833 (after having previously appeared in Russia and the northern parts of Germany, inflicting great mortality in every part of its course), might well be selected

for such illustration; were it not that the similar epidemic of 1837 was even yet more marked in its characters and progress, and attested by more various record from the countries it traversed. I have given below certain facts regarding this epidemic; chiefly illustrative of the points just mentioned, and in so far contributing towards the general history of the disease.* Some of these facts may bear the

* The influenza of this year made itself distinctly known as such in London, the first week in January; the weather during the four months preceding having been singularly wet and stormy. On the 29th of November a hurricane occurred from the S. W., of almost unprecedented violence in this country: on Christmas day a storm of wind and snow, simultaneous over the whole of the west of Europe, snow falling even in the streets of Lisbon and Palermo ; in such quantity in England as for some days to impede all intercourse throughout the country. What is more remarkable, from the remoteness of the locality, snow fell at Canton on the 8th of February, never before seen by the oldest inhabitant of that place. As another singular effect of this widely spread storm, the French army marching upon Constantina, in Africa, suffered severely under three days of incessant snow. About the same period violent hurricanes prevailed over every part of the European and American seas. It might seem as if the earth, in its movement through space, had been exposed to other than the ordinary periodical causes acting on its atmosphere or surface. And it is yet for philosophy to say, whether certain of the more general conditions to which we are thus subject do not arise from material agents, wholly external to itself, with which our planet comes into contact or proximity, while sweeping along its orbit. Some sanction is given to this idea by the periodical meteoric appearances which have recently become the subject of observation;-by what is known of the varying extension and sweep of the zodiacal light;—and by other phenomena, the simultaneous apparition of which, on distant parts of the globe, would seem to preclude all local or limited cause of their production.

Succeeding to the Christmas snow in England was a severe frost for some days; then a thaw the first week in January, followed by very uncertain and fluctuating weather till the middle of February, this being the period during which the influenza chiefly prevailed; the winds variable and from every quarter; the barometer high and low; the thermometer ranging from 25° to 55°; fogs and clear atmosphere, though tending to

aspect of atmospheric causes being directly concerned; but when it is considered that these states of weather were similar

the former; rains and dry weather, though the former much more frequent. It was a remarkable peculiarity in London, which I noticed also during the last weeks of 1836, that the heaviest and most continuous rains occurred with a high barometer; the longest courses of dry days with the barometer below 29°. Succeeding to the period of the influenza the cold was again very severe, with heavy falls of snow all over England, from the 20th of March to the middle of April, and the thermometer as low as 10° or 15° below the freezing point during the latter days of March. Even in May the temperature was several times considerably below 32°.

The duration of the influenza in London might be stated broadly at six or seven weeks. I saw no new cases after the 16th of February, but the tendency to relapse continued long afterwards in one form or another. The greatest severity of the disorder was from the 20th to the 24th of January. Including the slighter cases, it would be no exaggeration to rate the number attacked at half the population of London (perhaps few escaped the influence altogether), while the ordinary ratio of mortality during this time was nearly doubled. The valuable report of Dr. Clendinning from the Marylebone Infirmary, and Dr. Heberden's Analysis of the Bills of Mortality during the epidemic, may be consulted on this part of the subject.

As respects the local progress of the disease, the following are a few of the facts I have noted, but which might be easily rendered much more numerous from authentic sources. The epidemic appeared in Russia, Sweden, and Denmark, during the month of December; at periods varying from one to three weeks before its occurrence in London. In Copenhagen, according to the memoir of Dr. Otto, at least 30,000 persons were under the disease at one time early in January. In Scotland, also, it was observed earlier than in England; and generally in the northern and eastern parts of England before the southern and western. It had been prevalent about a fortnight in London before it became so at Brighton and other parts of the southern coast. It appeared in Lancashire, Cheshire, Gloucestershire, and the south-western counties, from a week to a fortnight later than in London. Though very general over the island, yet were there places seemingly unaffected, even in the contiguity of others where the disease greatly prevailed.

The epidemic showed itself in Paris about a month later than in London, having previously appeared at Calais and other intervening

and simultaneous over vast tracts of continent, while the disease made its progress by steps, having a certain course of general

places. I saw patients who, on their journey from Paris to London, had come upon an infected town, and been suddenly seized with the malady. At Paris it was stated to have affected at least half the population, but seemingly with less mortality than in London. The epidemic spread gradually over other parts of France. About the end of February it affected the northern coast of Spain, the more conspicuous there from its influence on the events of the civil war, then raging in Biscay and Navarre. Almost at the same time it appeared at Lisbon a new occurrence in that cityspreading successively to the several towns which lie upon the Tagus, even to the Spanish frontier. Dr. Leitao, who has narrated its progress in Portugal, seeks to show that it is contagious, and was brought directly from England to the British squadron in the Tagus, in the vessels of which it first appeared. The same idea prevailed in Biscay as to its manner of importation. The disease reached Madrid about the end of March, and prevailed there the whole of April.

In Germany the influenza appeared at Berlin in January, affected Dresden somewhat later, and Vienna and Munich a fortnight after Dresden. At Hamburgh, where it appeared in the first days of January, Dr. Rothenburg states that more than half the population was attacked. I do not possess any information as to its progress in Italy. In Malta it first showed itself about the 1st of June.

A remarkable fact is, that an epidemic, having the characters of the influenza of the northern hemisphere, prevailed at Sydney and the Cape of Good Hope in the latter part of 1836; the time thus corresponding with its earliest appearance in the north of Europe, though under a date of season wholly different. Sir John Herschel informs me that the weather was warm and apparently genial, at the time when almost every individual in the Cape District was suffering under the epidemic. The malady spread up the country as far as Gnadenthal, producing there considerable mortality in the Hottentot population.

The influenza of 1762 is first recorded at Warsaw about the end of February; over the north of Germany it spread about a month later. At Hamburgh and in London it appeared about the same time. Paris, and the greater part of France, were wholly unaffected. Venice appears particularly to have suffered. In the month of July the disease appeared in the English fleet in the Mediterranean. Beyond this time we have no record of its progress.

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