Influence. (Spanish.) See Catarrhus epidemicus. The same principle which induced Hippocrates to attribute epidemics to the re oeloe, gave this general epidemic catarrh the name of influenza. From Sydenham, upwards to Hippocrates, it was known by the name of catarr/ialis febris epidemica; but Sydenham chiefly calls it tussis epidemica: it hath been since variously named, but is now styled influenza.

In Dr. Cullen's system it is a variety of catarrhus a contagio.

In the year 1673 Sydenham treated of the nature and cure of the putrid fever, which he called variolous fever; he found that this fever returned every summer afterwards, and was succeeded by the cholera morbus and bilious fever (by him called the new fever). In 1675 these fevers were attended by a new symptom, viz. an uncommon degree of stupor, which frequently ended in a coma, and was for that reason by Sydenham called the comatous fever. In the beginning of November of the same year, this fever was complicated with a cough, and was described by Sydenham nearly as follows:

"The fever proceeded in this manner during the autumn, sometimes seizing the head, at others the bowels, every where raging under the appearance of symptoms peculiar to those parts till the end of October; when the weather, which till now had continued in a manner as warm as summer, changed suddenly to cold and moist; whence catarrhs and coughs became more frequent than I remember to have known them in any other season. But it is of most moment to observe, that the stationary fever of this constitution usually succeeded these coughs, and hence became more epidemic, and likewise varied some of its symptoms. For whereas, some little time before, it attacked the head and bowels, now it chiefly seized the lungs and pleura, whence arose peripneumonic and pleuritic symptoms; though it was still precisely the same fever that began in July 1673, and continued without any alteration of its symptoms till the rise of these catarrhs.

"These catarrhs and coughs continued to the end of November, after which they abated, but the fever still remained the same as it was before the catarrhs appeared: though it was neither quite so epidemic, nor accompanied with quite the same symptoms, these depending accidentally upon the catarrhs.

"1675, the season having continued unusually warm, like summer, till towards the end of October, and being suddenly succeeded by cold and moist weather, a cough became more frequent than I remember

5 L 2 to have known it at any other time; for it scarce suffered any one to escape, of whatever age or constitution be were, and seized whole families at once; nor was it remarkable only for the numbers it attacked (for every winter abundance of persons are afflicted with a cough), but also on account of the danger that attended it; for as the constitution, both now and during the preceding autumn, eminently tended to produce the epidemic fever above described, and as there was now no other epidemic existing, which by its opposition might in some measure lessen its violence, the cough made way for, and readily changed into, the fever. In the mean while, as the cough assisted the constitution in producing the fever, so the fever on this account attacked the lungs and pleura, just as it had affected the head even the week preceding this cough; which sudden alteration of the symptoms occasioned some, for want of sufficient attention, to esteem this fever an essential pleurisy or peripneumony, though it remained the same as it had been during this constitution, i.e. since July 1673.

"For it began now, as it always did, with a pain in the head, back, and some of the limbs; which were the symptoms of every fever of this constitution, except only that the febrile matter, when it was copiously deposited in the lungs and pleura, through the violence of the cough, occasioned such symptoms as belong to those parts. But, nevertheless, as far as I could observe, the fever was the very same with that which prevailed to the day when this cough first appeared: and this likewise the remedies, to which it readily yielded, plainly showed. And though the pungent pain of the side, the difficulty of breathing, the colour of the blood that was taken away, and the rest of the symptoms that are usual in a pleurisy, seemed to intimate that it was an essential pleurisy; yet this disease required no other method of cure than that which agreed with the fever of this constitution, and did no ways admit of that which was proper in the true pleurisy, as will hereafter appear. Add to this, that when a pleurisy is the original disease, it usually arises betwixt spring and summer; whereas the distemper we now treat of began at a very different season, and is only to be reckoned a symptom of the fever which was peculiar to the current year, and the effect of the accidental cough.

"Now, in order to proceed in a proper manner to the particular method of cure, which experience shows to be requisite both in this cough and in those which happen in other years, provided they proceed from the same causes, it is to be observed that the effluvia which used to be expelled the mass of blood by insensible perspiration are struck in, and thrown upon the lungs, from the sudden stoppage of the pores by cold; these by irritating the lungs immediately raise a cough; and the hot and excrementitious vapours of the blood being hereby prevented from passing off by perspiration, a fever is easily raised in the mass; namely, when either the vapours are so copious that the lungs are unable to expel them, or the inflammation is increased by the adventitious heat arising from the use of overheating remedies, or too hot a regimen, so as suddenly to cause a fever in a person who was already too much disposed to one. But of whatever kind the stationary fever be, which prevails the same year, and at the same time, this new fever soon assumes its name, becomes of the same kind, and in most particulars resembles it; though it may still retain some symptoms belonging to the cough, whence it arose. In every cough, therefore, proceeding from this cause, it is sufficiently manifest that regard must be had not only to the cough, but likewise to the fever that so readily succeeds it.