In addition to these disinfectants of long standing, which have been recognized in medicine for many years, another of great value is now coming into high favor. This is formalin, which, in its various forms, is convenient, economical and highly effective. Under the name of formaldehyde, one preparation of this disinfectant is widely but improperly used as a preservative for milk, meat and some other perishable foods. In almost every instance this is illegal, and properly so, for the substance is a poison and even when diluted cannot fail to be injurious. From formalin various disinfecting substances are made, and may be had at the drug stores, some as liquids and others in tablets to evaporate over a lamp for the general disinfection of rooms or houses. The latter may be recommended in the highest degree as a safe, economical and absolutely sanitary process. Corrosive sublimate is, perhaps, the most powerful germicide known, a solution of one part in a thousand, or a little more than a drachm to a gallon of water, being amply sufficient for all practical purposes. It does not injure or stain wood, varnish, paint, plaster or ordinary fabrics, and if the ceiling be whitewashed with a genuine lime wash, and the walls, floors, doors and furniture of the room be washed down with the mixture, no microbes can possibly escape. It attacks metals, but iron bedsteads are protected by the enameling. Poisonous as corrosive sublimate is, the danger from it is easily guarded against. The smallest dose of it known to have proved fatal, even to a child, would require no less than a quarter of a pint of the solution of one in a thousand parts. A mouthful of this would not cause more than temporary discomfort, while the taste would prevent a second being swallowed. Still, as a further safeguard it might be well to add a little laundry bluing to give color to the mixture, and a little wood alcohol to give it a smell. Then with a proper poison label on it surely no one would be endangered by it. PERIOD OF ISOLATION OR QUARANTINE