tion of inoculation, there had been ample time, and the subject had been seriously attended to: and the profession had become universally of opinion, that variolous pus inserted into a wound. excited the Small Pox alone, and never any other malady to which the person furnishing the matter was subject. Inoculation was as free from this tendency as the casual infection. Indeed, the law respecting all infectious diseases, as Small Pox, measles, the plague, and others, was in this respect the same. In whatever form, or by whatever means, the infection is conveyed, the specific disease under which the patient labours at the time is alone communicated, and unmixed with other complaints to which the person infecting may be disposed.

Were it otherwise, each individual of the present generation would be overwhelmed with an accumulation of distempers. But although the disease contracted by infection is simple, yet, after it has finished its course, it is not unusual for ailments of a different character to occur. These last disorders have evidently no reference to the subject from whom the infection was derived; but are to be attributed to the patient's constitution, and to the shock the system has received by the disease. Thus the measles sometimes leaves a tendency to inflammatory affections of the lungs and eyes; and scrofulous symptoms sometimes follow the Small Pox. But

F

instead of the latter proceeding from the pus used in inoculation, the intelligent have observed, that they occurred more frequently after the casual, than after the inoculated Small Pox, the former mode of contamination being the more violent.

The above principle, which governs other infectious diseases, also applies to the Vaccine. This infection is of the mildest nature, it can neither be conveyed by the breath, nor by perspiration; it can only be excited by depositing in a wound, or upon an abraded surface, some vaccine lymph.

Whether the lymph was taken from a cow, or from the human subject, the malady produced is simply the Vaccine: and respectable observers have never detected any other effect from Vaccination. There are not even those grounds of suspicion which are attached to variolous inoculation: for, the vaccine process is so gentle, as neither to enfeeble the habit, nor to rouse into action any indisposition which may be lurking in the constitution; and its influence is so transient, that in a very few days even delicate infants recover their pristine health.

CHAP. IV.

OF SMALL POX OCCURRING AFTER THE VACCINE ;
AND OF SMALL POX AND SEVERAL OTHER IN-

FECTIOUS DISEASES, IN SOME INSTANCES, RE-
CURRING TO THE SAME INDIVIDUALS.

THE groundless objections, hitherto raised against Vaccination, had at first a more powerful influence, than one now to be considered, which has some foundation. It was gradually observed, that a few of the multitudes who had been vaccinated were subsequently attacked with an eruptive fever. An outcry immediately ensued; some affirming, and others denying, that these eruptions were variolous. Strong attestations were signed, and virulent pamphlets were printed; for zeal and faction carried each party to extremes. But when this fervour had a little abated, it was evident to the impartial, that both had been in the wrong.

It was shown in the History of the Small Pox, that the same accusation was formerly raised against inoculation by Wagstaffe, De Haen, Van Swieten, and others: when the over-zealous advocates for that practice, in order to repel the charge, positively denied that the Small

Pox had ever attacked the same individual twice. A similar indiscretion was committed by some warm friends of Vaccination *. They refused their assent to the evidence in any case where Small Pox was said to have seized a person who had previously been vaccinated, and were precipitately convinced that Vaccination was an infallible preventive of Small Pox for life. Assertions of that force ought to have been left to the modern church of Rome: they were not in use in the ancient ritual. For Quintus Cicero†, an orthodox pagan, and a staunch believer in augury, supported this doctrine by boldly comparing it with the science of medicine; and maintained that the predictions of a soothsayer were not more fallacious, than the prognostications of a physician. Although the aptitude of this simile is inadmissible, yet it must be granted, that infallibility is inapplicable to human nature. Even in mixed mathematics, though the demonstrations are universally true in theory; yet, when the principles are put in practice, failures are frequent; for it is impossible to form

Amongst whom was the author.

"At nonnunquam ea, quæ prædicta sunt, minus eve"niunt. Quæ tamen id ars non habet? Earum dico artium "quæ conjectura continentur, et sunt opinabiles. An Medi"cina non putanda est? Quam tamen multa fallunt."

Cicer. De Divinat. lib. i. § 14.

figures, and to mould matter, conformably to ideal perfection. Since invariable success is denied to the mathematical arts, was it to be expected in medicine; the practice of which is not founded upon fixed self-evident propositions, but upon an imperfect knowledge of the animal economy, and of the numberless agents and events which influence the solids, the fluids, and organization of the bodies of ever-varying men; each individual of whom is dissimilar to every other: and all are moving, acting, and suffering under different circumstances; and changing perpetually from their first conception, even till their death. On a transient view of this incalculable variety, it might seem impossible to approximate to any rational system. But upon a closer inspection it is perceived, that there is a considerable similarity in the structure and operations of all human bodies; and that the deviations and disturbances of which they are susceptible, are limited to a certain range, beyond which life cannot subsist. It is owing to the portion of uniformity, harmony, and regularity in the construction and functions of the human organs; and to the aberrations, discordances, and anomalous irregularities being limited in extent, that there is a basis for the doctrines of physiology and pathology. Perfect health would require a faultless body and mind, residing in the most salubrious atmosphere and temperature,

*