“That fever often exists in them” (gaols) “cannot be denied; but this circumstance can afford no evidence of its being generated therein, any more than the multiplication of vermin in such places could demonstrate the spontaneous generation of these and other insects by the nastiness which favours the deposition and hatching of their eggs.” Taking the controversy at this point, and admitting the force of this statement, the decision upon it will not alter the practical value of cleanliness, or of its protective effects in prevention, whether it remove an original or only a predisposing cause. Yet it cannot but be regretted that the enlightened force of the professional opinion should sustain any diminution from an apparent want of unanimity on so important a question as the necessity of removing these causes, whether original or predisposing: that, for example, whilst the fleets were ravaged by fever and disease, men of high standing should have occupied the attention of the public with speculations on contagion, and infection from the gaols as the original cause, and diverted attention from the means of prevention, cleansing and ventilation, the means by which, as will hereafter be shown, the pestilence was ultimately banished. The main error of those who have ascribed fever to destitution, appears to have been in adopting too hastily as evidence of the fact of destitution, such _primâ facie_ appearances as are noticed by Dr. Scott Alison, an error which non-professional experience may correct. In more than one instance where, in a district in which the demand for labour was still great, and the wages high, benevolent gentlemen have propounded similar doctrines, which, being at variance with the known state of the labour-market, I have requested that the names of these fever cases might be given, that their antecedent circumstances might be examined, and the accuracy of the conclusions tested, by officers of experience in such investigations; but I think it right to state the names or means of inquiry have never been forthcoming. In general, medical practitioners and benevolent individuals are extremely liable to deceive themselves and to deceive others, by what they call the evidence of their own eyes. The occurrence of severe destitution is denied as a general cause of fever, not as a consequence. The evidence shows that the best means of preventing the consequent destitution are those which prevent the attacks of fever and other epidemics upon all classes of the community.