By an extract from a report of the late Dr. Currie, of Liverpool, given in the Appendix, it will be seen that at the time he wrote, 1797, when only 9500 of the population are reported to have lived in cellars, the proportion of fever cases was nearly the same as at present, when the cellar population has risen to 40,000; the disease has been almost as constant as the surrounding physical circumstances of bad ventilation, filth, and damp then pointed out as removable, and the disease has continued in every period of the prosperity of the town in its progress from a population of 77,000 to 223,000 in 1841. So the late Dr. Ferriar, of Manchester, when writing between 30 and 40 years ago, of the state of the population in periods of great prosperity, especially for hand-loom weaving, described the effect of the bad economy of the habitations much as they were described in the year 1829 by Dr. Kay, and as they are described in 1840 by Dr. Baron Howard. _Dr. Ferriar_, when he wrote to warn the labouring classes as to the choice of their dwellings, stated that— “The custom of inhabiting cellars also tends to promote both the origin and preservation of febrile infection. But even in them the action of filth and confined air is always apparent when fevers arise. I have often observed that the cellar of a fever patient was to be known by a shattered pane, patched with paper or stuffed with rags, and by every external sign of complete dirtiness.” The false opinions as to destitution being the general cause of fever, and as to its propagation, have had extensively the disastrous effect of preventing efforts being made for the removal of the circumstances which are proved to be followed by a diminution of the pestilence. The opinion of the majority of the medical officers of the unions in England on this topic, acting in districts in every condition, might be expressed in the terms used by _Dr. Davidson_:— “It has already been shown that filth and deficient ventilation tend much to spread the contagion of typhus, being almost constant concomitants; and that while it generally affects the whole members, or the large proportion of a family among the lower orders, it rarely spreads in this manner among the better classes of society, who attend more to cleanliness and ventilation. It is quite obvious that an amelioration of the physical condition of the lower orders, in these particulars, would, in proportion as this was effected, diminish their chances of catching the contagion, which would not only operate in lessening directly its diffusion, but by reducing the number of its sources, must tend to lessen the actual quantity of this principle that might be generated in a given time.