epidemic in Manila, where, for a time, the supply of locally prepared (Bureau of Science) serum threatened to become exhausted, I looked into the possibilities of getting a supply elsewhere and found that, to do so, in anything like a reasonable length of time, was impossible. Fortunately the threatened serum famine did not occur, the local supply in Manila proving adequate, although for a few weeks we were obliged to make use of a stock of Japanese serum which had been on hand for several years. Since the warning of some years ago, at which time the plague danger was an anticipated one, bubonic plague has actually appeared in the United States (New Orleans), the cases being sufficiently numerous to cause grave concern and to call forth the utmost repressive efforts of the authorities. The possibility of plague appearance in the coast cities of the United States, at any time, cannot be disregarded and provision for the treatment of human cases, as well as repressive (antirat) measures, is imperative. Antiplague serum is not producible upon a few hours' notice, nor is it manufactured in the United States. In view of present war conditions the difficulty of securing serum from overseas sources is greatly increased, so that we are well-nigh compelled to depend upon home-produced serum. In view of the uselessness of drug treatment it is plainly the duty of national, state and municipal authorities to keep on hand a reasonable supply of antipest serum to meet any outbreak. Manufacturers of biological products realize that the preparations for producing, storing and marketing antiplague serum are expensive and that the maintenance of immunized animals and the employment of expert serologists call for expenditures which are unlikely to be recovered from any demand for serum and that, moreover, the government is doing and will do all that lies within its power to make the serum unnecessary, by excluding plague. These are not encouraging conditions to lead American serum producers to add antiplague serum to the list of their products. If, under these adverse conditions, any producer of biologic products shall undertake to produce and maintain an adequate supply of antiplague serum, he will merit credit for a truly philanthropic service and will deserve the support of governments, national, state and municipal, as well as that of the medical profession.

CHAPTER I
ITS HISTORY AND ITS EXTENSION

In plague there exists the most intimate relationship between cause and prevention. We will therefore set forth here, as briefly and concisely as their importance will permit, the principal facts related to the causation of the disease. Without an understanding of this relationship there can be no rational preventive treatment.

These facts constitute one of the interesting stories of modern medicine: the story of the arrangement and interpretation of certain apparently unrelated facts, some of them long known to men, in the clear light of modern method; the story of the application of analysis, synthesis, logic and experiment, all leading to the creation of an understanding which permits us to battle successfully with pestis bubonica, one of the most ancient of human plagues.

History.—This disease has an historic interest, most engaging and fascinating, which one finds it difficult to pass over with mere mention.

I venture to recall, therefore, that plague almost certainly dates back to the pre-Christian era, the earlier record naturally being lacking in sufficient accuracy of description to enable us to identify the recorded epidemics, definitely and positively, with true bubonic plague.

An epidemic of the second century b.c., as described, seems to have been one of true plague, while the pandemic which began in Egypt in the sixth century a.d., thence extending to Constantinople, Europe and the British Isles, was certainly the disease known in modern times as the plague. This pandemic, beginning as the plague of Justinian, was probably followed by the continuous presence of the disease in Europe, marked by many local outbreaks and periods of quiescence and extending down through the centuries to the period of the Crusades. In the eleventh and twelfth centuries the returning Crusaders spread the plague widely through Europe, which country it ravished from the eleventh to the fourteenth centuries, reaching its climax of intensity in the "Black Death" of Europe of the Middle Ages. The disease thereafter continued to devastate Europe, the great population centres, Paris and London, suffering especially from its visitations and its more or less constant presence. The Great Plague of London, the last important epidemic of the disease in that metropolis, began in 1664 and lasted five years. With less than half a million of inhabitants it is estimated that London gave one of every six or seven of her citizens to the Black Death during the first year of the epidemic. Then followed a remarkable disappearance of the disease from Western Europe. The eighteenth century was marked by few epidemic appearances of plague.

At the end of the first half of the nineteenth century it had practically disappeared from Egypt and from European and Asiatic Turkey, formerly its favorite haunts. In interior Asia it has probably existed for centuries, the non-emigrating character of the people limiting and confining its devastations.

To these centres and to the commercial invasion of China, we must probably trace the beginning of the present pandemic of plague, which exists to-day, a menace to the civilized and uncivilized world. In the days of the Crusades a religious invasion of the infected centres caused the disease to spread throughout Christendom, while in the present day a commercial invasion has caused it to spread completely around the world.

That this is a truth and not a fanciful statement is shown by the appearance of plague in the following countries since 1894, when it spread from interior China. In every case it has followed those sanitary lines of least resistance, the paths of commerce.

Extension.—To the eastward, from China, it spread to Japan, the Philippines, Australia, the Hawaiian Islands, Alaska, California, Mexico, Peru and the western coast of South America. To the westward, it invaded India, Mauritius, Egypt, Suez ports, Eastern, Central and South Africa, Mediterranean ports, Great Britain (Scotland), the West Indies and Brazil. In the last twenty years plague has caused millions of deaths, and, during a single week in April, 1907, it destroyed more than 75,000 lives in India, a number about equal to the deaths of a year in London during the Great Plague of 1665. In contrast with India the rest of the world has suffered little during the present world-epidemic, but this loss, while relatively small, is enormous when translated into lives and dollars. The figures for India are simply huge.

Mortality.—The official lists of deaths in India for the last twenty years include some in which the number of reported deaths per year exceeded one million, and it has been estimated that the actual number of persons dead from the plague during this period approximates 8,000,000.

It is gratifying to note a marked decrease in the total mortality in the reports of the last few years, but so long as the annual death list, year after year, was measured by hundreds of thousands, rather than thousands, the situation could not be considered as anything