Whether the information which could be collected even by the most diligent and extensive research would prove sufficiently copious and accurate to enable us to pursue this method with complete success, may be a matter of doubt; but it is at least probable, that many valuable facts, now buried in oblivion, would thus be brought to light; and the incidental results, as often occurs in the pursuit of science, might prove as serviceable as those which were the direct object of discovery. Of what immense importance, for instance, in the fourteenth century, would a general knowledge have been of the simple but universal circumstance, that in all severe epidemics, from the time of Thucydides[2] to the present day, a false suspicion has been entertained by the vulgar, that the springs or provisions have been poisoned, or the air infected by some supposed enemies to the common weal. How many thousands of innocent lives would thus have been spared, which were barbarously sacrificed under this absurd notion? Whether Hecker’s call for aid in his undertaking has, in any instance, been answered by the physicians of Germany, I know not; but he will be as much pleased to learn, as I am to inform him, that it was the perusal of the “Black Death” which suggested to Dr. Simpson of Edinburgh the idea of collecting materials for a history of the Leprosy, as it existed in Great Britain during the middle ages; and that this author’s very learned and interesting antiquarian researches on that subject, as published in the Edinburgh Medical and Surgical Journal, have been the valuable, and, I trust, will not prove the solitary result. As the three treatises, now comprised for the first time under the title of “The Epidemics of the Middle Ages,” came out at different periods, I have thought it best to prefix to each the original preface of the author; and to the two which have already been published in English, that of the translator also; while Hecker’s Address to the Physicians of Germany, although written before the publication of the “Englische Schweiss,” forms an appropriate substitute for an author’s general preface to the whole volume. At the end of the “Black Death,” I had originally given, as No. III. of the Appendix, some copious extracts from Caius’ “Boke or Counseill against the Disease commonly called the Sweate or Sweatyng Sicknesse;” but this little treatise is so characteristic of the times in which it was written, so curious, so short, and so very scarce[3], that I have thought it worth while, with the permission of the council of our Society, to reprint it entire, and to add it in its more appropriate place, as an Appendix to the Sweating Sickness. ADDRESS TO THE PHYSICIANS OF GERMANY. BY J. F. C. HECKER.