An effective rat-proofing program must be practicable and not too drastic; otherwise it will fail from lack of popular support. Attempts to enforce rat proofing of existing structures would probably not be feasible unless under stress of an outbreak of bubonic plague or other rat-borne disease epidemic. There seems to be no good reason, however, why buildings constructed in the future or remodeled should not be made rat proof under the requirements of building ordinances. Had such ordinances been enacted 50 years ago and rigidly enforced since that time the large majority of buildings to-day would be rat proof, and rats, with their accompanying filth and destructiveness, would have been largely eliminated. There would also be fewer of the unsightly and insanitary shacks now existing in most cities, and the average structure would be of a more desirable type. As modern construction conforms so closely in principle to the requirements of rat proofing, there should be little, if any, opposition among builders to a rat-proofing clause in building ordinances. In considering the suppression of rats, at the outset city authorities should discard all methods other than those that strike at the source of the trouble. The actual destruction of rats is necessary as a temporary means of stopping their depredations, but modern construction and sanitation are the weapons that must be relied upon to gain permanent relief. In addition to a rat-proofing ordinance, every city should have a law requiring that all garbage wherever accumulated be kept in rat-proof containers or garbage cans until collected or until destroyed by incineration or otherwise disposed of in a manner that would avoid the possibility of its providing food for rats. Containers should have covers not easily removed by dogs and other animals. The city should also enact regulations prohibiting the accumulation of trash, refuse, or waste matter of any kind on either public or private premises, and should provide adequate means for collecting and disposing of all waste. Consideration should also be given to the sewer system. Although most modern sewers do not offer opportunity for the unrestricted breeding of rats, there are many still in use that furnish harbors for large numbers of these pests in sections of some cities. Of most importance is the corner catch basin, storm sewer, or street-drainage opening, which should be effectively remodeled, if necessary, to provide smooth interior vertical walls with a drop of at least 3 feet; rats are unable to jump 3 feet vertically or to climb smooth surfaces.