health, wishing to show the need for those measures he advocated, drew a comparison between the rate of mortality in some most salubrious village (in Cumberland, I think it was), and the rate of mortality in London; and then, pointing out the marked difference, alleged that this difference was due to "preventible causes"—to causes, that is, which good sanitary administration would exclude. Ignoring the fact that the carbonic acid exhaled by nearly three millions of people and by their fires, caused in the one case a vitiation of the air which in the other case did not exist—ignoring the fact that most city-occupations are of necessity in-door, and many of them sedentary, while the occupations of village life are out-of-door and active—ignoring the fact that in many of the Londoners the activities are cerebral in a degree beyond that to which the constitution of the race is adapted, while in the villagers the activities are bodily, in a degree appropriate to the constitution of the race; he set down the whole difference in the death-rate to causes of the kind which laws and officials might get rid of.
A still more marked example of this effect of a cherished hypothesis in vitiating the evidence given by an inquirer, was once unconsciously yielded to me by another enthusiast for sanitary regulation. Producing his papers, he pointed out a statistical contrast he had been drawing between the number of deaths per annum in the small town near London where he lived, and the number of deaths per annum, in a low district of London—Bermondsey, or Lambeth, or some region on the Surrey side. On this great contrast he triumphantly dilated as proving how much could be done by good drainage, ventilation, etc. On the one hand, he passed over the fact that this small suburban town was, in large measure, inhabited by a picked population—people of means, well fed and clothed, able to secure all appliances of comfort, leading regular and quiet lives, free from overwork and anxiety. On the other hand, he passed over the fact that this low region of London was, by virtue of its lowness, one out of which all citizens pecuniarily able to take care of themselves escaped if they could, and into which were thrust an unusual number of those whose poverty excluded them from better regions—the ill-fed, the drunken, the dissolute, and others on the highway to death. Though, in the first case, the healthiness of the locality obviously drew to it an excess of persons otherwise likely to live long; and though, in the second case, the unhealthiness of the locality made it one in which an excess of those not likely to live long were left to dwell or brought to die; yet the whole difference was put down to direct physical effects of pure air and impure air respectively.
Statements proceeding from witnesses whose judgments are thus warped—statements republished by careless sub-editors, and readily accepted by the uncritical who believe all they see in print, diffuse erroneous prepossessions; which, again, tend to justify themselves by drawing the attention to confirmatory facts and away from facts that
