On the subject of contagion our author observes, that some difficulties still remain; but these, though proper subjects of future inquiry, “do not appear to be of force sufficient to invalidate facts already established. It is well known, that the same person who has been inoculated two or three times for the small-pox without effect, even in an epidemic season, has afterwards received the infection upon repeating the operation at a distance of time when the disease was hardly sporadic. The cause of this remains unknown; but ignorance of it was never produced as an argument against the reality of variolous contagion.... If, of one hundred persons exposed to the infection of the plague by a near aproach to the sick, ninety should fall sick, shall human inability to assign satisfactory reasons for the escape of the other ten be converted into a positive proof against the disease having been caught by contagion? If persons retired from all commerce with the infected and their attendants, breathing the same air with the rest of the inhabitants, and nourished by the same aliment, remain untouched during the ravage of the plague, as long as they continue secluded, but, upon unguarded communication, are taken ill like others; can any rational doubt be entertained about the cause of their former security? Or if through stealth, or neglect of requisite precautions, substances tainted by the sick should be conveyed into these secluded retreats, and persons living temperately as before, ignorant of what had happened, and consequently in the midst of imaginary security, happen to be seized with the distemper; can it with any show of reason be ascribed, not to contagion, but to terror, or to colluvies in the stomach and bowels, produced by intemperance and bad aliment? The instances here alluded to are not the _creation of fancy_, but _strictly consonant to repeated experience_ in Turky; to say nothing at present of what has been observed at Marseilles and in various cities in Europe.”