I have already pointed out that it is no protection to have waste-pipes trapped, because in every form of trap one must have stagnation, and wherever stagnation occurs there must be putrefaction. A very small quantity of food-refuse or milk is enough to set up putrefaction in a trap. If any outlet for water is thought desirable in a larder, it should be in the form of an open gutter which can be thoroughly cleaned and dried, and which should pass directly through the wall on the floor-level, the opening in the wall to be closed by a sliding trap-door when the gutter is not being used. No bacteriologist needs to be reminded that a water-trap is necessarily a cultivating chamber. CHAPTER II THE SANITATION OF THE ISOLATED DWELLING We are now in a position to consider the sanitation of the isolated dwelling. Having dwelt upon the evils of putrefaction, it is to be expected that methods which involve no putrefaction will be recommended. Further, it must be remembered that there are many situations which are otherwise suitable for a dwelling, but are rendered unsuitable by the lack of water; and in these days we have become so absolutely dependent upon water, that no site for a dwelling where water is scarce is acceptable. DRY METHODS We have come to think that there can be no cleanliness without soap and water, and it may be necessary to remind the reader that the nomad Arab cleanses himself with the sand of the desert; that polished floors redolent of beeswax and turpentine are at least as wholesome as those that are scrubbed and have their crevices filled with a soapy slime; and that one of the best ways of washing a flannel shirt is said to be to hang it in the sun and beat it thoroughly with a stick. Necessity is the mother of invention, and were there a water-famine to-morrow, I have no doubt that those who were minded to be cleanly would somehow manage to be so. There is no denying that dry methods of sanitation are in this country, where water is plentiful, far from popular. Dwellers in cities want to be rid of matters which have no value for _them_ as individuals, and the luxury of having a scavenger 'laid on,' who can be set at work by merely turning a tap, and who, albeit that we pay handsomely for his services, does not hang about to be 'tipped,' are undeniable. Then, again, our scavenger is a very strict teetotaller and never strikes, although occasionally he is 'frozen out.' Many of us during a severe frost have, so to say, been the victims of dry methods and of 'water' closets, so called, on the principle of _Lucus a non lucendo_. If dry methods of sanitation are to be successfully carried out, it is necessary to bear in mind the principles which underlie them. HUMIFICATION