In 1847 that city had a cellar population of 20,000; an ordinance was passed forbidding the occupation of underground rooms as residences, with certain restrictions, and within three years the great mass of people in these subterranean haunts were removed to better tenements, with a great reduction of the mortality of the city. That city, formerly the most unhealthy in England, has continued the reforms thus inaugurated by compelling landlords to improve their tenant-houses, and the result is that it has become one of the healthiest towns of Europe. London has recently taken similar action in regard to cellar tenements. What these cities have done, New York can and ought to do for her public health. [Sidenote: A Town That Was Immune] What the diseases which prevail with such fatality in the uncleaned tenant-houses are for the most part preventable, we have the most undoubted evidence. That smallpox is preventable is known to every school-boy, and yet that loathsome disease to-day prevails throughout all the tenant-house districts of New York, without the slightest restraint on the part of our local authorities. Typhus is to-day ravaging the homes of the poor without “let or hindrance,” and yet cleanliness and pure air are sure preventives. Of this truth these reports furnish many examples. The fever-nest--West Thirty-third Street--is one of a row of tenant-houses five stories high, and contains 16 families. It was in a filthy condition, without Croton water, waste-pipes stopped, sinks overflowing and emitting offensive odors; fever had prevailed all winter, nearly every person in the house having had an attack, four having died. It was never inspected by a city official. The owner was induced to clean the house, and from that date not a case of fever has occurred. The inspector who reports this case very justly adds: “If, when the first case of fever occurred in this building, the owner had been compelled to put it in a good sanitary condition, six human lives would undoubtedly have been saved, besides a great amount of sickness.” [Illustration: PLAN OF A REAR CUL-DE-SAC FEVER-NEST, 1865] Cholera infantum and diarrhoeal affections are found in their greatest intensity where putrescible animal matter and domestic filth exist. Remove these causes, or remove the patients from the neighborhood, and these diseases generally disappear at once. Diphtheria is found to be most intense in the vicinity of unclean stables. It is, therefore, with great propriety, that the entire class of zymotic diseases are now called “filth and foul air” diseases by the English sanitary writers. Remove the filth and foul air, and these diseases disappear as effect follows cause. [Sidenote: Can Populous Towns Be Improved?]