In dealing with the relation of the earth to disease it behoves us to move with caution, and we shall do well at the outset to admit that there is very little knowledge of the subject which can be regarded as certain. We are in the land of conjectures, surmises, and plausible hypotheses, which perhaps are leading on to certain knowledge, but it will be necessary to check the dicta of the laboratories by experience gained outside of them. Such has always been the admirable custom in this country, where the labours of the pure scientist have been checked by that truly excellent staff of workers, the medical inspectors of the Local Government Board, to whom the world at large is more deeply indebted that perhaps it is aware. Before we blame the earth for causing us harm we must be sure that the facts, or alleged facts, of the bacteriologist are supported by the experience of the practical epidemiologist. Science unchecked by practice will certainly lead us astray in the future, as it has done in the past, and just as a 'lie which is half a truth is ever the blackest of lies,' so a new scientific fact imperfectly understood has potentialities for evil which are unbounded. If we set aside for the present the question of malaria, which is undoubtedly primarily connected with certain soils, we have very little evidence that any other disease of practical importance is primarily connected with the soil. There appear to be two microbes which are present with tolerable constancy in the upper layers of the soil, and which, when applied to a raw surface or injected hypodermically, may cause tetanus and malignant œdema; but as yet we are without any evidence that either of these diseases can be caused by drinking water which has percolated through the soil, or can rise as a miasm from the soil. They concern the surgeon mainly, and from the point of view of epidemiology are unimportant. Phthisis, or rather death from phthisis, which is not quite the same thing, is said to be more prevalent on damp soils than on dry ones, and it has further been said that the death-rate from this disease has been reduced in certain towns by sewerage. This statement is not universally accepted, and even if it be true it does not necessarily inculpate the soil because damp soils are cold, and patients with phthisis or any chronic lung trouble are very intolerant of cold and damp. It is very generally recognised that phthisis is prevalent in proportion to overcrowding, and that it is conveyed by tuberculous milk or meat seems to be certain as the result of recent experimental work. Any charge against the soil itself is as yet not proven. Diphtheria has been said to be prevalent on certain soils, but this assertion is now discredited, and we recognise that the great cause of its spread is overcrowding. Its habitat, if it has any, outside the animal body is not yet known.