The main causes of this great and growing misery are patent. The remedies for them are scarcely less plain. The chief sources of that disease and death which may be prevented by the action of the community are, first, the filthy and poisonous houses into which a large part of the people are crowded; second, the imperfect ventilation of portions of the city,--its narrow and dirty streets, lanes, and yards; and, third, the want of sufficient house and street drainage and sewerage. It is important to note in relation to these sources of evil, that, while the poverty of our poor is generally not such complete destitution as that of many of the poor in foreign cities, their average condition is worse. The increase of disease and mortality is a result not so much of poverty as of condition. "The pith and burden of the whole matter is, that the great mass of the poor are compelled to live in tenements that are unfit for human beings, and under circumstances in which it is impossible to preserve health and life." To improve the dwellings of the poor, to make them decent and wholesome, is, then, the first step to be taken in checking the causes of preventable disease and death in our cities. This work implies, if it be done thoroughly, the securing of proper ventilation, sewerage, and drainage. Most of the houses which the poor occupy are the property of persons who receive from them a rent very large in proportion to their value. No other class of houses gives, on an average, a larger return upon the capital invested in it. The rents which the poor pay, though paid in small sums, are usually enormous in comparison with the accommodation afforded. The houses are crowded from top to bottom. Many of them are built without reference to the comfort or health of their occupants, but with the sole object of getting the largest return for the smallest outlay. They are hotbeds of disease, and exposed to constant peril from fire. Now it seems plain that here is an occasion for the interposition of municipal authority. In spite of the jealousy (proper within certain limits) with which governmental interference with private property is regarded in this country, it is a manifest dereliction of duty on the part of our city authorities not to exercise a strict supervision over these houses. The interests which are chiefly affected by their condition are not private, but public interests. There are legal means for abating nuisances; and there is no reason why houses which affect the health of whole districts should not be treated in the same way as nuisances which are more obtrusive, though less pernicious. In some of the cities of Europe, in Nuremberg, for instance, there is a public architect, to whom all plans for new buildings are submitted for approval or rejection according as they correspond or not with the style of building suitable for the city. What is done abroad to secure the beauty of a city might well be done here to secure its health.