We shall see as we proceed how the natural check to smallpox (whatever it was), the immunity of the majority from infection, and the decline of the disease were all claimed as the blessed results of Jenner’s prescription; and now-a-days it has passed into common-place, for which evidence is thought superfluous, that without that prescription smallpox might have illimitable extension. If anywhere a variolous epidemic is slight, it is said that but for vaccination it would have been severe; and if severe, that its intensity would have been doubled or trebled save for the action of the same prophylactic. We have a remarkable illustration of this style of prophecy in the Report of the Select Committee of the House of Commons upon the Vaccination Act of 1867, dated 23rd May, 1871, where we read-- Smallpox unchecked by Vaccination, is one of the most terrible and destructive of all diseases as regards the danger of infection, the proportion of deaths among those attacked, and the permanent injury to the survivors. Your Committee believe that if Vaccination had not been general, _the epidemic_ [then prevalent] _would have become a pestilence, raging with the destructive force of the Plague of the middle ages_. What is beyond evidence is beyond refutation; and the imaginations of M.P.’s, dull though they be, not unfrequently prevail over their intelligence. To set aside the mass of testimony adduced by Jenner’s friends before the Commons’ Committee in 1802 is sometimes described as a hopeless undertaking; but the answer to such a boast is, that experience has nullified the essential part of that testimony, and that there is little left to account for. No well-informed medical practitioner now believes what the Committee was led to believe, that to be inoculated with cowpox was to be secure from smallpox for life. The security, where still credited, is subject to so many qualifications that the primitive inoculators with cowpox would have thought such protection not worth paying for, still less of exulting over as the greatest discovery ever made in medicine. Nor would many now admit the validity of the Variolous Test which then carried conviction with irresistible force. Inoculation with smallpox was in itself an uncertain operation, and that it should fail after inoculation with cowpox, ere the poisoning of the blood had been worked off, was in nowise surprising. The exposure of vaccinated subjects to smallpox infection was in like manner deceptive; and it was conveniently forgotten that all manner of people were exposed to contagion with impunity in the usual circumstances of life. Taking a year of exceptional smallpox in London, such as Dr. Lettsom set forth as ordinary, when 18,000 were affected and 3000 died (that is one in six), there were in the million of inhabitants 982,000 who escaped. How did they escape? A multitude must have come into immediate contact with the sick: