Bubonic plague has played a major role in human history for approximately the last 1 years, and possibly longer. It has afflicted mankind in three great pandemics, as we many smaller epidemics, but remains a highly controversial and in many respects poo understood subject. First, there has been disagreement, for all pandemics but the last, w medicine had developed sufficiently to make positive and undeniable identification of bacillus involved, 2 that it actually was bubonic plague (caused by Yersinia pestis) that peatedly killed masses of people and disrupted society. 3 Second, although there is no