Although the flush-tank may receive no faecal matter, and even though the housemaid's sink may not deliver into it, it will contain in the discharge from the kitchen alone an amount of organic matter which will produce offensive and dangerous gases by its decomposition. To provide for the safe removal of these gases, a ventilating pipe should be carried up to some point not near to any window or chimney-top. From the time the sewers are ready for service no accumulation of faecal matter or other organic household waste should be allowed to remain in the village. All old vaults and cesspools should be filled with earth, and disinfected by the admixture of lime with the upper layers of the filling. The use of water-closets in all houses should be made imperative; and the construction and arrangement of soil-pipes and of all outlets should be regulated by the health authorities. It is not worth while here to discuss the details of the construction of water-closets and other interior plumbing work, except with reference to soil-pipes and such drains as may deliver the outflow of soil-pipes to the public sewer. The soil-pipe should be of cast iron, carefully jointed with lead, not less than four inches in diameter, and carried by the straightest course possible up through the roof and generally higher than the ridge-pole. Its open top must not be near any window, and if within ten feet of a chimney it should be at least one foot below the level of the top of that chimney. There should be no trap in the soil-pipe, and no trap in a private drain between the outlet of the soil-pipe and the sewer. The reasons for this rule are twofold:-- 1. No matter what amount of water may be used for flushing out the soil-pipe, its sides will always be more or less coated with organic filth; and, however slight this coating, there will be a certain amount of decomposition. The decomposition of all such matters must be rapid and complete, not slow and partial. A necessary condition of complete destructive decomposition is an abundance of atmospheric air to supply the oxygen which complete decomposition demands. If the soil-pipe is closed at its top, or if it is obstructed by a trap in the lower part of its course, there can be no such circulation of air as safety requires. If there is an opportunity for the free admission of air from the well-ventilated sewer to feed the upward current almost constantly prevailing in a soil-pipe open at both ends, the gases resulting from the decomposition will be of a different and less injurious character than where the air is confined,--and by the mere volume of air passing through the pipe they will be so diluted that even were they originally poisonous their power for harm will be lessened.