look at small-pox from any other point of view than that of the vaccinationist, and thus miss the essential features of the evidence they have before them. Every statistician knows the enormous value of the representation of tabular statistics by means of diagrammatic curves. It is the only way by which in many cases the real teaching of statistics can be detected. An enormous number of such diagrams, more or less instructive and complete, were presented to them, and, at great cost, are printed in the Reports; but I cannot find that, in their Final Report, they have made any adequate use of them, or have once referred to them, and thus it is that they have overlooked so many of the most vital teachings of the huge mass of figures with which they had to deal.
It is one of the most certain of facts relating to sanitation that comparative density of population affects disease, and especially the zymotic diseases, more than any other factor that can be ascertained. It is mainly a case of purity of the air, and consequent purification of the blood; and when we consider that breathing is the most vital and most continuous of all organic functions, that we must and do breathe every moment of our lives, that the air we breathe is taken into the lungs, one of the largest and most delicate organs of the body, and that the air so taken in acts directly upon the blood, and thus affects the whole organism, we see at once how vitally important it is that the air around us should be as free as possible from contamination, either by the breathing of other people, or by injurious gases or particles from decomposing organic matter, or by the germs of disease. Hence it happens that under our present terribly imperfect social arrangements the death-rate (other things being equal) is a function of the population per square mile, or perhaps more accurately of the proportion of town to rural populations.
In the light of this consideration let us again compare these diagrams of Irish, Scottish, and English death-rates. In Ireland only 11 per cent, of the popu-
