Unless we bear in mind these conditions of the public intelligence, we shall misapprehend the demeanour of the people who so cordially welcomed Jenner’s advertisement. It is always a mistake to criticise the conduct of an earlier generation by the light of a later. We turn history to ill account when we use it to nourish our self-complacency; for the probability is that had we lived with our forefathers, we should have done exactly as they did. Some will ask, How did it ever come to pass that so many doctors in 1800 signed Ring’s testimonial certifying that inoculation with cowpox was a sure and everlasting protection from smallpox when they had not, and could not have, any experience to warrant their assertion? True, but they had an illusory experience by which they were beguiled, namely, the Variolous Test. Hundreds were inoculated with cowpox and subsequently with smallpox, and were also exposed to smallpox contagion, and as the disease did not take, it was concluded it could never take, and that the subjects of the operation were fortified for ever. The fallacy is now manifest, but it was by no means manifest in 1800, and all manner of men received and propagated the fable with energetic sincerity. It was once admitted that a tub full of water did not overflow when a fish was slipped into it, and many explanations were current of the curious phenomenon until a sceptical spirit suggested that the experiment be tried. A like spirit might have suggested that it was expedient to wait and see whether cowpox was indeed a perpetual defence against smallpox, inasmuch as nature had an awkward habit of confuting prognostications apparently irrefragable. The ease with which it was asserted cowpox inoculation could be performed, coupled with its harmlessness, not to say wholesomeness, and the absolute security it afforded against smallpox, induced benevolent busybodies to set up as vaccinators all over the country. What the kindly quack delights in is something cheap and handy with a touch of mystery and the promise of immeasurable advantage--conditions which the new practice completely fulfilled. The memoirs of the time, especially of the Evangelical party, abound with instances in which this good soul and that good soul had vaccinated so many hundreds or thousands, delivering them from the peril of an awful disease. Thus in the _Gentleman’s Magazine_, for December, 1800, we read-- Two respectable families near Manchester have within these few months inoculated upwards of 800 of the neighbouring poor from two months old to twenty years with uniform success. Twenty of them were subjected to the variolous test, and all were found proof against the disease. And John Ring relates--