We have already made an allusion to some of those facts that must assist us in the solution of this problem, under the head of Public Health (_see page 98_.) “The putrefaction of animal matter,” says Dr. _Bancroft_,[202] “is but a natural separation of organized bodies, previously held together by animal or vegetable life, by which there can be no chance, nor even possibility of thus generating any thing so wonderful, and so immutable as contagion; which resembling animals and vegetables in the faculty of propagating itself, must, like them, have been the original work of our common creator, and must have been continued in existence by the energies of a living principle, exerted successively in the different bodies, through which it has been transmitted from one generation to another; as well might we revive the forever exploded doctrine of equivocal generation, and believe, as formerly, that insects and reptiles are the offsprings of mere corruption, as to believe that a substance so analogous to them, in that most mysterious and essential function of self-propagation, could originate from that cause, or from any operation of chemical agencies alone.” We are not disposed to believe that the specific contagion of typhus can thus be directly generated, but may not typhus be excited by causes independent of contagion, and having been once generated become contagious? If, says Dr. _O’Brien_, the opinion that contagion is the _only_ source of typhus be true, we are at once reduced to the necessity of supposing that all contagious diseases were derived from Adam himself. It is an indubitable fact that the plague has always first appeared, and established its head quarters, in the filthiest parts of crowded, ill constructed, and large cities. _Blackmore_ remarks that the impurity and filth, connected with the galleys and slaves at Marseilles, filled the air with offensive smells easily perceivable by those who passed along the adjoining shore; and in 1720 the plague broke out there; in London, Dr. _Heberden_ also observes, that the plagues of 1626 and 1636 broke out at Whitechapel, a part of the town which abounded with poor, and with slaughter-houses. The importance of cleanliness is also shewn by the exemption of Oxford[203] and other places from pestilential diseases, as recorded by different authorities, in consequence of regulations for ensuring it; while the late dreadful increase of contagious fever in Cork sufficiently demonstrates the evils which arise from deficient ventilation and accumulated filth, and to which causes Dr. _Barry_, in his report, ascribes the awful afflictions to which we allude. _Erasmus_, in a letter to _Franciscus_, Cardinal _Wolsey’s_ physician, ascribes the sweating sickness, which was a species of plague, in a great measure to the incommodious form, and bad exposition of their houses, to the filthiness of the streets, and to the sluttishness within doors.[204] That particular species of typhus, which