From the nature of the work, I have not considered myself at liberty to make those extensive alterations of text which usually belong to a second edition. I have restricted myself to a few verbal corrections, and to rectifying or omitting some unimportant paragraph, here or there, in case its matter has been more fully or more correctly stated in parts of a subsequent Report. Frequently, where I have wished to explain or qualify passages in the text, I have added foot-notes; but these are distinguished as interpolations by the mark--J. S., 1854. My Reports lay no claim to the merit of scientific discovery. Rather, they deal with things already notorious to Science; and, in writing them, my hopes have tended chiefly towards winning for such doctrines more general and more practical reception. It has seemed to me no unworthy object, that, confining myself often to almost indisputable topics--to truths bordering on truism, I should labour to make trite knowledge bear fruit in common application. Nor in any degree do they profess to be cyclopædic in the subject of Preventive Medicine; for it is but a small part of this science that hitherto is recognised by the law; and that--so far as the metropolis is concerned, scarcely beyond the confines of the City. It would have been an idle sort of industry, to say much of places or of matters foreign to the jurisdiction of those whom I officially addressed. In re-publishing documents which proclaim extreme sanitary evils, as affecting the City, I think it right to draw attention to the dates of the several Reports, and to state that for the last five years many of these evils have been undergoing progressive diminution, of late at a rapid and increasing rate; while, at their worst, they represented only what I fear must be considered the present average condition of our urban population.