Traps and trapped gullies are evils which are only to be tolerated for the prevention of greater evils. I visited not long ago a convalescent home built on the slopes of a decidedly steep hill. The building was a fine one, and (why I do not know) was three storeys high. The builder had brought the rain-water pipes from the roof, and had made them terminate in trapped gullies close to the front wall of the house. In these collections of stagnant water, dead leaves, &c., would certainly decay, and every trap would inevitably become a cultivating chamber for the growth of mildew and moulds of various kinds. These trapped gullies communicated with an underground drain, where the same growth of mildew, &c., would inevitably go forward. In such a situation the rain-water, without the interference of the builder and architect, would have got clean away into the valley below, and have left the house perfectly dry. All that was needed was an open gutter. Great expense had been incurred to make the walls of this building dry, and still greater expense had been incurred to ensure precisely those evils which come from damp walls, viz., the growth of mildew. In the autumn of 1896 I was stopping in an hotel which had no less than 42 trapped gullies touching its walls; there was one beneath almost every window and by the side of almost every door. Here, again, a little contrivance and common sense would have obviated all this mischievous expense. The constant inhalation of the gases of putrefaction is a great danger to health, otherwise sanitarians would not lead us to imply that we ought to spend enormous sums to ensure their dilution before we inhale them. If these gases be concentrated, they are capable of killing strong men in a few minutes. The constant inhalation of these gases in a more diluted form leads to malnutrition, and one must suppose that the pasty-faced and undersized Cockney is made in this way. We have little certain knowledge of the diseases caused by sewer air. Personally, I should say that anæmia and malnutrition are the chief resulting evils, and that these conditions make us very vulnerable to infections. Sore-throat is certainly a drain disease, and thus a vulnerability to diphtheria is probably engendered. Puerperal disease of various kinds and rheumatic fever are among the diseases which have been attributed to sewer air, and it is probable that chronic enlargement of the tonsils and the surprising increase of adenoid growths in the pharynx and naso-pharynx are not without similar relationships. Dr. Letheby and Dr. Haldane, who both investigated cases of acute poisoning by air in sewers, came to the conclusion that sulphuretted hydrogen was the fatal ingredient. Dr. Haldane is of opinion that the source of the sulphuretted hydrogen is the kitchen refuse in the fat traps and grease boxes. He states that ·07 per cent. (or a mixture containing 7 parts of sulphuretted hydrogen with 9,993 parts of air) is poisonous.