The earlier writers have given some account of these diseases, which have occasionally prevailed as very fatal and devastating epidemics; surpassing all other diseases in their mysterious origin, in their rapid extension, and in the duration of their prevalence. In the East,--in Egypt, and on the eastern border of the Mediterranean, fearful epidemics have prevailed from time immemorial. They have often proved very destructive, especially in the Middle Ages, and as late as the sixteenth and seventeenth centuries. During the prevalence of the "Pestis," which raged throughout Europe between the years 1347 and 1350, according to computation, a fourth part of the inhabitants of this part of the globe was carried off. The estimates of the vast numbers swept away by its repeated occurrence and prevalence appear quite incredible. During the time it raged at Marseilles in 1720, it is reported that in the Charity Hospital there were admitted from October 3d to February 28th, 1,013 patients, of whom 585 died; and during the same period, in another hospital, there were admitted from October to July 3d, 1,512 patients, of whom 820 died. The population of Marseilles previous to the occurrence of the disease was estimated at about 90,000, of whom 40,000 died; leaving only about 10,000 of the whole population who had not been attacked or in any way affected; so that the record shows the appalling mortality of fifty per cent. of those who were attacked. The bills of mortality in 1770 and 1771 were as appalling as any arising from epidemics of a later day. A very extended notice of the "Pestis" as it raged in Moscow in the year 1771 is given by M. Gerardin, who, quoting from the published statistics, observes: "In April, the deaths were 744; May, 851; June, 1,099; July, 1,708; August, 7,268; September, 21,401; October, 17,561; November, 5,235; December, 805"; making a total in nine months of 56,672, which is considerably less than the estimate given by De Mertens, who thinks the whole number carried off by this pestilence, from the city alone, cannot be less than 80,000. These statistics bear a striking resemblance to those of the Epidemic Cholera, whose fatality is materially varied by the seasons of the year; the greatest being usually at the close of Summer or the beginning of Autumn. There are, in short, many points of resemblance in this and former epidemics to that of the Cholera, which naturally lead to the supposition that all have had a common origin, if, indeed, they be in many respects dissimilar.