high degree were reached at any place on the premises, as, for example, in a cesspool, that concentration would cease and a favorable degree of dilution would take its place, somewhere in the neighborhood, at a greater or less distance from the focus of filth. We should therefore always insist upon the degree of cleanliness which we understand to promote the greatest possible prevention and dilution of filth, as our hygienic aim; and we shall furthermore do well, if we remove not only from our houses, but from the neighborhood, and keep removed, all that seems to us to be dirt, and offends our innate æsthetic feelings.
The mycologists have further taught us that no germs escape from fluids and moist objects by mere evaporation, but that they only pass into the air in the form of dust, or when gases are generated and puff out, or when something adheres to things that are washed with such moist objects. We might be tempted to conclude from this that nothing more is necessary, to make and keep our abodes free from disease, than to keep everything properly moist. But, aside from the fact that damp houses and damp soils are positively disadvantageous to health, it would not be possible to maintain such a degree of moisture or other conditions that it should never be too dry, that there should never be any spurts of gas, and that no germs should ever be washed off. We can judge of the uselessness of such efforts from the fact that no one has ever found air, either out-of-doors when it has rained incessantly for a long time, nor in a house where it is still moist, that was free from mold. We attach more importance to the fact, likewise established by mycologists, that all germs flourish only in fluids and damp media, and that moist walls, not dry ones, become moldy.
If moisture really afforded protection against the escape of germs, we might imagine the drains and sink-holes connected with our houses to furnish the best kind of drainage, because they are always moist, and contribute something to the required moisture in the soil. I consider these sinks close to the house to be dangerous neighbors, even when they are designed only to carry off rain-water. I proceed upon the time-honored experience of physicians that certain malarious diseases prevail most actively in damp spots in houses and villages situated in hollow places or at the foot of slopes, after inundations. A sink is an artificial trough, an artificial flood-region for each house, into which is concentrated the drainage from the roof and from the surrounding ground. By it a certain part of the house-ground is exposed to occasional floods, which can have no other results for the house than the occasional inundations in a larger region have for the places lying within it. When such pits are unavoidable, it is well to have them as far as possible from the house; but it would be better to conduct the water coming from the roof or elsewhere to some place where it can no longer prejudice our health. I look upon the removal or great diminution of these sinks as constituting the chief advantage of the sewerage of cities. The hygienic value of sewerage may have been