CHAPTER III
THE GENERAL STATISTICS OF SMALL-POX MORTALITY
IN RELATION TO VACCINATION
Having thus cleared away the mass of doubtful or erroneous statistics depending on comparisons of the vaccinated and the unvaccinated in limited areas or selected groups of patients, we turn to the only really important evidence, those "masses of national experience" which Sir John Simon, the great official advocate of vaccination, tells us we must now appeal to for an authoritative decision on the question of the value of vaccination; to which may be added certain classes of official evidence serving as test cases or "control experiments" on a large scale. Almost the whole of the evidence will be derived from the Reports of the recent Royal Commission.
In determining what statistics really mean the graphic is the only scientific method, since, except in a few very simple cases, long tables of figures are confusing; and if divided up and averages taken, as is often done, they can be manipulated so as to conceal their real teaching. Diagrams, on the other hand, enable us to see the whole bearing of the variations that occur, while for comparisons of one set of figures with another their superiority is overwhelming. This is especially the case with the statistics of epidemics and of general mortality, because the variations are so irregular and often so large as to render tables of figures very puz-
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