The injurious effects on the health of persons who occupy buildings that take in their air supply through unclean apertures are too well known to those medical men and others who have had experience in sanitary matters, and it can be only estimated by results. I could enumerate cases where the health of the inmates and the death-rate were conclusive evidence to prove the disastrous effects produced by air being supplied through such inlets. One case in particular, which consisted of eight blocks of buildings planned exactly alike. The drains were cut off on the outside at the foot of all soil-pipes, and a second disconnection about 50 feet from the building. In one building the basement was drained into the branch drain with a trap in the inside, and from the quantity of water and soil which flowed through this branch drain the basement trap was constantly being siphoned, leaving a 6-inch air supply into the building through 50 feet of drain. This, combined with 200 feet per minute through the W.C., had the effect of causing an unusual depression of spirits in the occupants of this building, and more deaths occurred in this one block than in the whole of the others. It does not require a large amount of scientific knowledge to ensure a healthy building. What is required is sound pipes, the area of them in proportion to the work they have to do, tight joints, and a knowledge of ventilation. Nothing must be left to theory. A pipe either leaks and lets out the soil, or it is sound. If it is sound, sewage matter can be carried through it anywhere without the slightest injury to health or unpleasantness of any kind. Pipes can be ventilated without traps being siphoned, and the gases from sewers and soil-pipes treated so as to ensure healthy buildings at a moderate cost. As a rule, the first intimation of any defect in the drainage system of a town or the sanitary fittings of a building is given by the medical officer of health or the medical attendant of the family, whose attention has been forcibly drawn to it by the serious illness of the inmates. It is no unusual occurrence, that after the medical officer, surveyor, and inspector of nuisances have made a minute inspection of a building, they leave it without discovering defects which exist in pipes carefully cased over, or in the sanitary fittings. To detect the manner in which poisons from drains are thrown into a building and inhaled by the occupants, is oftentimes not an easy matter. In many cases the drains have been so cut about and additions made to them, that to trace defects or even the number of drains which are attached to the branch drains or sewers, a considerable amount of excavating is necessary.