It is only possible, during the few moments allotted to me at this time to refer, in the briefest possible manner, to some features of certain epidemics in the past. I shall only consider the four diseases which stand at the head of epidemics, namely, the plague, asiatic cholera, yellow fever and smallpox.
I.—THE BUBONIC PLAGUE.
This is a disease of great antiquity. The first extensive epidemic of which history has given us any definite account occurred in the sixth century, is described as "the plague of Justinian," and is said to have persisted during nearly the whole of that emperor's long reign. It probably originated in Lower Egypt in the year 542 A.D. It swept with increasing fury over Asia Minor; it also visited Constantinople with the result that for some days people died, so it is related, at the rate of 10,000 daily. For seventy years this disease