As some of the material which I have collected for text-book articles during the past eight years bears directly upon the present discussion and presentation, I have ventured to quote from it, sometimes without rephrasing, such parts as are accurate at the present time. I am also quoting freely from the records and from the experiences of my predecessors and colleagues in the work in Manila. It should be understood that the pathology of the disease has been practically omitted from consideration as out of place in an epidemiologic investigation and report. The pathologic side of the work during the Manila epidemic of 1912-1914 was covered in a masterly manner by Dr. B. C. Crowell and his associates at the Medical School of the University of the Philippines, and I have no doubt that the record of the work done and studies made will appear in appropriate form in due time and will hereafter be referred to as among the most valuable pathologic studies ever made during a plague epidemic, on account of their accuracy and completeness. I have included, as of great value and directly related to the epidemiologic phase of this study, reports of some of the bacteriologic work done in connection with this epidemic at the Bureau of Science, Manila, by Dr. Otto Schöbl. I am sure that the value of his studies as reported in part here, with his permission, will be apparent to every careful reader. I am greatly indebted to him for his permission to make use of this portion of his studies. Having been in daily touch with Dr. Schöbl during the year and a half of the continuance of this epidemic, I can appreciate to the fullest extent the painstaking and accurate character of his work and findings, of which the part here presented is by no means the greatest. I am quite aware of the fact that there are those who view with some question the practicability of controlling plague by the measures applied in Manila, as recited here; but American plague workers are likely to meet this unbelief by pointing to the accomplished fact, in San Francisco, in Honolulu, in Porto Rico, as well as in Manila; and before long, as we confidently expect, in New Orleans.