In reading Dr. Hecker’s account of the Black Death which destroyed so large a portion of the human race in the fourteenth century, I was struck, not only with the peculiarity of the Author’s views, but also with the interesting nature of the facts which he has collected. Some of these have never before been made generally known, while others have passed out of mind, being effaced from our memories by subsequent events of a similar kind, which, though really of less magnitude and importance, have, in the perspective of time, appeared greater, because they have occurred nearer to our own days. Dreadful as was the pestilence here described, and in few countries more so than in England, our modern historians only slightly allude to its visitation:—Hume deems a single paragraph sufficient to devote to its notice, and Henry and Rapin are equally brief. It may not then be unacceptable to the medical, or even to the general reader, to receive an authentic and somewhat detailed account of one of the greatest natural calamities that ever afflicted the human race. My chief motive, however, for translating this small work, and at this particular period, has been a desire that, in the study of the causes which have produced and propagated general pestilences, and of the moral effects by which they have been followed, the most enlarged views should be taken. The contagionist and the anti-contagionist may each find ample support for his belief in particular cases; but in the construction of a theory sufficiently comprehensive to explain throughout, the origin and dissemination of universal disease, we shall not only perceive the insufficiency of either doctrine, taken singly, but after admitting the combined influence of both, shall even then find our views too narrow, and be compelled, in our endeavours to explain the facts, to acknowledge the existence of unknown powers, wholly unconnected either with communication by contact or atmospheric contamination.