PLAGUE.
Plague was known in the second and third centuries. In the sixth century it ravaged the Roman empire and destroyed half the population in the eastern provinces. Under the name of the "black death" it swept over Europe in 1347-50 with a sacrifice of one-fourth of the inhabitants—about 25,000,000. During the fifteenth and sixteenth centuries many epidemics prevailed in various parts of Europe, and the disease seemed to have fastened itself on that part of the world. It seems, however, that the pneumonic form, the most contagious, gradually became less common, or the virulence of the infection diminished, and this, with the institution of quarantine regulations, decreased the prevalence of the disease during and following the seventeenth century. Nevertheless, there have been occasional outbreaks in Eastern Europe since that time. Since the recrudescence of plague in Hongkong in 1893 and in other places later, the disease has been subjected